part 2 - posters (16 mb, 410 pages)

PROGRAM

Dresden, GermanyJuly 22 – 27, 2012

International Conference on Superlattices, Nanostructuresand Nanodevices

www.icsnn2012.de

Vol. 2Poster

Presentations

Table of Contents

Poster Session • Tuesday, July 24, 2012 ............................................................................ 5

Poster Session • Thursday, July 26, 2012 ......................................................................... 15

Abstracts – Poster Presentation ........................................................................................ 25

TuP1 ............................................................................................................................... 27 TuP2 ............................................................................................................................... 67 TuP3 .............................................................................................................................. 111 TuP4 ............................................................................................................................. 133 TuP5 ............................................................................................................................. 158 TuP6 ............................................................................................................................. 201 ThP1 ............................................................................................................................. 218 ThP2 ............................................................................................................................. 265 ThP3 ............................................................................................................................. 306 ThP4 ............................................................................................................................. 339 ThP5 ............................................................................................................................. 375

Abstracts – Index of Authors (Poster Presentation) ......................................................... 405

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Poster Session • Tuesday, July 24, 2012

16.30 TUP-1 - GROWTH AND NANOFABRICATION

16.30 TuP-1-1 | Optimization of the number of quantum well pairs for High Bright AlGaInP-based Light Emitting DiodesHwa Sub Oh, Hyung Joo Lee, Young Jin Kim

16.30 TuP-1-2 | Self Assembled Nano Structured Al O Incorporated PI Thin Film: A 2 3

Smart MaterialShailendra Kumar Tiwary, Anand Kumar Gupta

16.30 TuP-1-3 | Growth Kinetics of MPS-capped CdS Quantum Dots in Self-assembled Thin FilmsKenan Koç, Fatma Zehra Tepehan, Galip G. Tepehan

16.30 TuP-1-4 | Probability of Twin Formation on Self-catalyzed GaAs Nanowires on Si SubstrateMasahito Yamaguchi, Jihyun Paek, Hiroshi Amano

16.30 TuP-1-6 | In-plane mapping of buried InGaAs quantum rings and hybridization effects on the electronic structureMarcio Daldin Teodoro, Angelo Malachias, Vivaldo Lopes-Oliveira, Daniel Ferreira Cesar, Victor Lopez-Richard, Gilmar Eugenio Marques, Euclydes Marega Jr., Mourad Benamara, Yuriy Mazur, Gregory J. Salamo

16.30 TuP-1-7 | GeSi quantum dots and quantum wells growth on Si(100) surface by MBEAleksandr Nikiforov, Vyacheslav Timofeev, Serge Teys, Anton Gutakovsky, Oleg Pchelyakov

16.30 TuP-1-8 | In-situ grown hexagonal silicon nanocrystals in silicon-carbide-based filmsTae-Youb Kim, Chul Huh, Rae-Man Park, Hojun Ryu, Cheol-Jong Choi, Maki Suemitsu

16.30 TuP-1-9 | From growth to device fabricationDhirendra Kumar, Poonam Sharma, Vijeta Kumar

16.30 TuP-1-10 | Influence of the pit sidewall inclination on the SiGe quantum dot nucleation siteMartyna Grydlik, Moritz Brehm, Thomas Fromherz, Friedrich Schäffler

16.30 TuP-1-11 | Conditions for perfect ordering of Ge/Si(001) quantum dots: Influence of pit-shape and size and buffer layer on the ordered island growthMoritz Brehm, Martyna Grydlik, Friedrich Schäffler

16.30 TuP-1-12 | Flash Lamp Processing of InAs nanostructures on silicon and SOI wafersSlawomir Prucnal, S.q. Zhou, Stefan Facsko, A. Muecklich, X. Ou, M.o. Liedke, B. Liedke, Manfred Helm, W. Skorupa

16.30 TuP-1-13 | OPTO STRUCTURAL STUDIES OF WELL DISPERSED SILICON NANOCRYSTALS GROWN BY ATOM BEAM SPUTTERINGNupur Saxena, D. Kabiraj, D. Kanjilal

16.30 TuP-1-14 | Influence of In segregation and intermixing on the optical and electronic properties of InAs/GaAs quantum dots and photodetectorsAlvaro Maia, Fernando Fernandes, Marcel Claro, Euzi da Silva, Alain Quivy

16.30 TuP-1-15 | Nanotwinning and structural phase transition in CdS quantum dotsPragati Kumar, Ramesh Chandra, F. Singh, Avinash Agarwal

16.30 TuP-1-16 | Effects of shutter transients in moleculor beam epitaxyShin-Ichiro Gozu, Teruo Mozume, Haruhiko Kuwatsuka, Hiroshi Ishikawa

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16.30 TuP-1-17 | Electrically Conductive Nanocomposite Hollow FibersShi Hyeong Kim, Seon Jeong Kim

16.30 TuP-1-18 | EPITAXY ON THE METALLIC SUBSTRATESGintarė Statkutė

16.30 TuP-1-19 | Impact of Ga induced superstructural phases on GaN growth on Si(111) surfacePraveen Kumar, S. M. Shivaprasad

16.30 TuP-1-20 | Accurate control of highly stacked InAs quantum dash cavity with GaAsSb/AlAsSb-distributed Bragg reflector grown on InP(001) substrate by wet chemical etchingKouichi Akahane, Naokatsu Yamamoto

16.30 TuP-1-21 | A simple method to make electrical connection between nanoscale electrodes and microwire using suspended PMMA stringHakseong Kim, Sang Wook Lee, Hoyeol Yun, Jinkyung Lee

16.30 TuP-1-22 | Particle Size Effects on the Structural, Morphological and Optical Properties of SiO -Al O Sol-Gel Nanocomposite Thin Film Coatings2 2 3

Bengü Özugur Uysal, Fatma Zehra Tepehan

16.30 TuP-1-24 | Synthesis and Characterization of MWCNT-SiO Sol-Gel Hybrid 2

Thin FilmsBengü Özugur Uysal, Fatma Zehra Tepehan

16.30 TuP-1-25 | Thermal stability of III-nitride structures studied by in-situ XRD measurementsLars R. Khoshroo, Alexander Kharchenko, Woitok Joachim F.

16.30 TuP-1-26 | Sol Electrophoretic Growth of TiO nanotubes2

Abolghasem Nourmohammadi


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16.30 TUP-2 - NANOPHOTONICS AND OPTICAL CHARACTERIZATION

16.30 TuP-2-1 | Single-photon emission from single InGaAs/GaAs quantum dots grown by droplet epitaxy at high substrate temperatureM. Benyoucef, V. Zuerbig, J. P. Reithmaier, A. W. Schell, T. Aichele, O. Benson

16.30 TuP-2-2 | Influence of Heat Treatment on Optical and Structural Properties of Self-assembled Thin Films of MPS-capped ZnS Quantum DotsKenan Koç, Fatma Zehra Tepehan, Galip G. Tepehan

16.30 TuP-2-3 | Raman Scattering of InAs/AlAs Quantum Dot Superlattices Grown on (001) and (311)B GaAs Surfaces.Alexander Milekhin, Nikolay Yeryukov, Alexander Toropov, Dmitry Dmitriev, Evgeniya Sheremet, Dietrich R. T. Zahn

16.30 TuP-2-4 | A Groove Patterns on Transfer Rollers-Based Micro-Electrochemical Etching for Circuits Construction on iPhone TouchscreensP.s. Pa

16.30 TuP-2-5 | Enhancement in light emission efficiency of Si nanocrystal light-emitting diodes by a SiCN/SiC superlatticeChul Huh, Chel-Jong Choi, Bong Kyu Kim, Byoung-Jun Park, Eun-Hye Jang, Sang-Hyeob Kim

16.30 TuP-2-7 | Optical properties of Ni, Cu nanowire arrays and Ni/Cu superlattice nanowire arraysY.y. Zhang, Y. M. Xiao, G. T. Fei, Wen Xu

16.30 TuP-2-8 | Investigation of single buried InAs quantum dots by scanning near-field nano-spectroscopyRainer Jacob, Markus Fehrenbacher, Stephan Winnerl, Jayeeta Bhattacharyya, Harald Schneider, Manfred Helm, Hans-Georg von Ribbeck, Lukas M. Eng, Paola Atkinson, Armando Rastelli, Oliver G. Schmidt

16.30 TuP-2-9 | Plasmonic enhancement of photoluminescence in hybrid Si nanostructures with Au fabricated by fully top-down lithographyKoudou Nakaji, Hao Lee, Takayuki Kiba, Makoto Igarashi, Seiji Samukawa, Akihiro Murayama

16.30 TuP-2-10 | Study of N/ In Compositional Modulation in GaInNAsSb Multiple Quantum Wells using Magneto-photoluminescenceKylie O'shea

16.30 TuP-2-11 | A comprehensive study of optical characterization of n- and p- type as-grown and annealed modulation doped GaAs/GaInNAs QW structuresOmer Donmez, Fahrettin Sarcan, Ayse Erol, M. Cetin Arikan, Fatih Ungan, Esin Kasapoglu, Huseyin Sari, Janne Puustinen, Mircea Guina

16.30 TuP-2-12 | Optical and electronic properties of GaSb-based type II ”W-shaped” quantum wells for the active region of interband cascade lasers emitting in the range of 2-6 µmFilip Janiak, Grzegorz Sek, Marcin Motyka, Krzysztof Ryczko, Kazuto Koike, Adam Bauer, Sven Höfling, Martin Kamp, Alfred Forchel

16.30 TuP-2-13 | Effect of Be doping on the optical properties of catalyst free MBE-VLS grown GaAs nanowires on Si (111) substrateAkio Suzuki, Atsuhiko Fukuyama, Ji-Hyun Paek, Masahito Yamaguchi, Tetsuo Ikari

16.30 TuP-2-15 | On the generalized Hartman effect presumption in semiconductors and photonic structuresHerbert P. Simanjuntak, Pedro Pereyra


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16.30 TuP-2-16 | ZnO-based microwire quantum well heterostructures for cavity applicationsMartin Lange, Christof P. Dietrich, Michael Lorenz, Marius Grundmann

16.30 TuP-2-17 | A Study of Photomodulated Reflectance on Staircase n-type GaAs/Al Ga As Quantum Well Structuresx 1-x

Omer Donmez, Ferhat Nutku, Ayse Erol, M. Cetin Arikan, Yuksel Ergun

16.30 TuP-2-18 | Room Temperature Passive Mode-Locked Laser Based on InAs/GaAs Quantum-Dot SuperlatticeMikhail Sobolev, Mikhail Buyalo, Idris Gadzhiev, Ilya Bakshaev, Yurii Zadiranov, Efim Portnoi

16.30 TuP-2-19 | Optical properties of CdTe/PbTe quantum wells and quantum dots emitting in a mid infrared rangeFilip Janiak, Marcin Motyka, Krzysztof Ryczko, Grzegorz Sek, Jan Misiewicz, Kazuto Koike, Takanori Hotei, Mitsuaki Yano

16.30 TuP-2-20 | S-shaped temperature-dependent photoluminescence shift in ZnCdSe / ZnSe multiple quantum wellsKun Gao, Wen-Chung Fan, Slawomir Prucnal, Wolfgang Skorupa, Shengqiang Zhou

16.30 TuP-2-21 | Optical investigation on Ge Sn alloys1-x x

B. H. Tsai, J. Z. Chen, K. Y. Wu, H. H. Cheng, Z. P. Yang, Y. C. Chang

16.30 TuP-2-22 | LOCALIZED SUPERFICIAL PLASMON AS A PROBE OF MOLECULE FORMATION IN PAIRS OF METALLIC NANOPARTICLESAngela Camacho, Mario Zapata-Herrera

16.30 TuP-2-23 | Micro-Raman characterization of GaN nanorodsPaulina Kamyczek, Zbigniew Zytkiewicz, Ewa Placzek-Popko, Eunika Zielony, Marta Sobanska, Kamil Klosek, Anna Reszka

16.30 TuP-2-24 | Temperature dependent Raman investigation of rolled up InGaAs/GaAs microtubesEvgeniya Sheremet, R. D. Rodriguez, D. J. Thurmer, D. Lehmann, O. D. Gordan, F. Seidel, O. G. Schmidt, Michael Hietschold, Dietrich R. T. Zahn

16.30 TuP-2-26 | Performance enhancement of InP based quantum well infrared photodetectors via the incorporation of a photonic crystal structureJuan Pablo Vasco, Wesller Schmidt, Paulo Sergio Soares Guimaraes, Wagner Rodrigues, Weber Hanry Morais Feu, Rudy Massami Kawabata, Mauricio Pamplona Pires, Patricia Lustoza De Souza

16.30 TuP-2-27 | Modulation of the inter-cavity refractive index as a way to control the coupling between two photonic crystal cavitiesJuan Pablo Vasco, Paulo Sergio Soares Guimaraes, Marcelo Franca Santos, Herbert Vinck Posada

16.30 TuP-2-28 | Can the exciton-polariton regime be defined by purely quantum properties?G. Cipagauta, D. G. Suárez-Forero, H. Vinck-Posada, K. M. Fonseca, R. R. Rey-González, W. Herrera

16.30 TuP-2-29 | Towards dynamic strain tuning of quantum dot excitons using Fourier synthesized acoustic pulsesF. J. R. Schülein, Eugenio Zallo, Paola Atkinson, Armando Rastelli, O. G. Schmidt, Achim Wixforth, Hubert J. Krenner

16.30 TuP-2-30 | High Efficiency Integrated Optical Sensor with < 0.5V Bias Voltage in Standard CMOS TechnologyYuh-Hui Lai


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16.30 TUP-3 - NANOELECTRONICS AND TRANSPORT

16.30 TuP-3-1 | Displacing, squeezing, and time evolution of quantum states for nanoelectronic circuitsJeong Ryeol Choi, Kyu Hwang Yeon, Byeong Jae Choi, Hyun Deok Kim, Mustapha Maamache

16.30 TuP-3-2 | Magnetotransport in a GaPSb nanofilmH. E. Lin, S.-W. Wang, Shun-Tsung Lo, Huang-De Lin, Yu-Chung Chin, Hao-Hsiung Lin, Jheng-Cyuan Lin, C.-T. Liang

16.30 TuP-3-3 | QUASISTATATIONARY STATES IN SINGLE AND COUPLED GaAs-(Ga,Al)As QUANTUM WELLS UNDER THE ACTION OF HYDROSTATIC PRESSURE AND APPLIED ELECTRIC FIELDSAna Schönhöbel, Jaime Girón, Nelson Porras-Montenegro

16.30 TuP-3-4 | Electronic transmittance phase extracted from mesoscopic interferometersMugurel Tolea, Valeriu Moldoveanu, Ion Viorel Dinu, Bilal Tanatar

16.30 TuP-3-5 | Talking through the Continuum: A Robust Scheme for Coupling Quantum StatesYoungsoo Yoon, Fransson Jonas, Kang Myoung-Gu, Shiran Xiao, Nobuyuki Aoki, Reno John, Yuichi Ochiai, Mourokh Lev, Jonathan P. Bird

16.30 TuP-3-6 | Temperature Dependence of the Persistent Photoconductivity in SnO Nanobelts2

Emilson Ribeiro Viana Junior, Geraldo Mathias Ribeiro, Juan Carlos González, Alfredo Gontijo de Oliveira

16.30 TuP-3-7 | Current and Shot noise in DNA chainsJudith Ojeda, Monica Pacheco, Luis Rosales, Pedro Orellana

16.30 TuP-3-8 | Transport properties of two finite armchair nanoribbonsLuis Rosales, Jhon González

16.30 TuP-3-9 | Spin-dependent electron scattering and transport through charged quantum dots in a quasi-one-dimensional semiconductor nanostructureLeonardo K. Castelano, Guo-Qiang Hai, Mu-Tao Lee

16.30 TuP-3-10 | Magnetic nanoparticles induced dielectric enhancement in (La, Gd) O : SiO nano-glass composite systems2 3 2

T. H. Kao, S. Mukherjee, C. C. Chou, H. D. Yang

16.30 TuP-3-11 | A study of magnetodielectric effects in magnetic MnO: SiO nano-2

glass composite systemS. Mukherjee, H. D. Yang, A. K. Pal

16.30 TuP-3-12 | Controlling the shot noise in a quantum dot coupled to a side quantum ringVictor Apel, Monica Pacheco, Enrique Anda, Pedro Orellana

16.30 TuP-3-13 | Enhancement of thermoelectric efficiency due to the Fano effect in quantum dotsMaria Loreto Ladrón de Guevara, Oscar Avalos, Guillermo Gómez, Pedro Orellana


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16.30 TUP-4 - TERAHERTZ

16.30 TuP-4-1 | Extraordinary terahertz absorption bands observed in Micro/Nano-structured metallic/dielectric sphere arraysWen Xu, Guotao Duan, Fuhai Su

16.30 TuP-4-2 | Splitting of cyclotron resonance peaks in parabolically confined quantum dots in the presence of high magnetic fields and intense terahertz radiation fieldsWeiyang Wang, Chengxiang Zhao, Shuhui Zhang, Wen Xu

16.30 TuP-4-3 | GR-FET application for high frequency detection deviceYuichi Ochiai, Mahjoub Akram M., Takuto Abe, Katsuhiko Miyamoto, Taashige Omatsu, David K. Ferry, Koji Ishibashi, Nobuyuki Aoki, Jonathan P. Bird

16.30 TuP-4-4 | Ionization of coherent excitons in (GaIn)As/GaAs quantum wells by strong terahertz fieldsBenjamin Ewers, Niko Köster, Ronja Woscholski, Martin Koch, Sangam Chatterjee, Galina Khitrova, Hyatt Gibbs, Andrea Klettke, Mackillo Kira, Stephan Koch

16.30 TuP-4-5 | Terahertz plasmon and surface plasmon modes in hollow nanosphereY. M. Xiao, Y.y. Zhang, Wen Xu

16.30 TuP-4-6 | Higher temperature operation LO phonon depopulation terahertz quantum cascade lasers design with high-Al-compositionTsung-Tse Lin, Hideki Hirayama

16.30 TuP-4-7 | Landau level population inversion and stimulated terahertz transitions in asymmetric quantum well structures in tilted magnetic fieldMaksim Telenkov, Yury Mityagin, Petr Kartsev

16.30 TuP-4-8 | Intersubband dynamics in two-photon quantum well infrared photodetectorsCarsten Franke, Harald Schneider, Hui Chun Liu, Jérôme Faist, Martin Walther

16.30 TuP-4-9 | Coexistence of Bloch and Gunn type oscillations in semiconductor superlatticesM. Alvaro, M. Carretero, L. L. Bonilla

16.30 TuP-4-10 | Cyclotron resonace in HgTe/CdTe based heterostructures in quantizing magnetic fieldsAnton Ikonnikov, Maxim Zholudev, Artem Lastovkin, Kirill Maremyanin, Kirill Spirin, Alexander Antonov, Vladimir Gavrilenko, Milan Orlita, Olexiy Drachenko, Manfred Helm, Michelle Goiran, Frederic Teppe, Wojciech Knap, Sergey Droretskiy, Nikolay Mihailov

16.30 TuP-4-11 | Intraexcitonic coherent nonlinear optics in quantum wellsMartin Teich, Martin Wagner, Dominik Stehr, Harald Schneider, Manfred Helm, Andrea Klettke, Sangam Chatterjee, Stephan Koch, Hyatt Gibbs, Galina Khitrova

16.30 TuP-4-12 | THz spectroscopy of optically excited InGaAs-GaAs quantum wellsJohannes Schmidt, Martin Teich, Dominik Stehr, Stephan Winnerl, Harald Schneider, Manfred Helm

16.30 TuP-4-13 | Interband absorption and photocurrent in type-II InAs/GaSb superlatticesMarcos H. Degani, Justino R. Madureira, Marcelo Z. Maialle

16.30 TuP-4-14 | THz Generation by Gunn Oscillations in Unipolar NanodiodesMubarak Ali, Aimin Song


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16.30 TUP-5 - GRAPHENE AND CARBON NANOTUBES

16.30 TuP-5-1 | Electron Beam Reduction method for Preparing the Catalyst Layer in the Growth of Carbon NanotubesAzam Mahmoodi

16.30 TuP-5-2 | Copper catalyzing growth of Carbon nano tubes on sodalime glass substrate at low temperatureAzam Mahmoodi

16.30 TuP-5-3 | Formation of multi-quantum dots in hydrogenated grapheneChiashain Chuang, Reuben K. Puddy, Malcolm R. Connolly, Shun-Tsung Lo, Huang-De Lin, Tse-Ming Chen, Charles G. Smith, Chi-Te Liang

16.30 TuP-5-4 | Electron States in Graphene with One-dimensional Potential Barriers and WellsDmitry Miserev, Matvey Entin

16.30 TuP-5-5 | Excitons in Monolayer GrapheneMahmood Mahmoodian, Matvey Entin

16.30 TuP-5-6 | Electron Energy Relaxation in GrapheneMatvey Entin, Lev Magarill

16.30 TuP-5-7 | Electrical generation of Cerenkov acoustic-phonon emission from grapheneChengxiang Zhao, Shuhui Zhang, Wen Xu

16.30 TuP-5-8 | Transmission of acoustic waves through graphene-semiconductor layered structuresShuhui Zhang, Wen Xu

16.30 TuP-5-9 | Random and deterministic simple shear in graphene and graphene sheetRaimundo Costa, Gil de Aquino Farias

16.30 TuP-5-10 | Optoelectronic properties of ABC-stacked trilayer grapheneY. M. Xiao, Y.y. Zhang, Shuhui Zhang, Wen Xu

16.30 TuP-5-11 | Bound states in the continuum in trilayer graphene nanoribbonsNatalia Córtes, Luis Rosales, Monica Pacheco, Pedro Orellana

16.30 TuP-5-12 | Study of optical anisotropic property of chemical vapor deposition prepared graphene filmsYu-Lun Liu, Hsuen-Li Chen, Chen-Chieh Yu, Chun-Chiang Kuo, Chen-Kai Chang, Chun-Wei Chen, Li-Chyong Chen, Kuei-Hsien Chen, Yu-Shen Lai

16.30 TuP-5-13 | Nanoscale Optical and Electrical Characterization of Aligned Semiconducting Single-Walled Carbon Nanotubes in a Field Effect TransistorR. D. Rodriguez, Marius Toader, S. Hermann, Evgeniya Sheremet, S. Müller, O. D. Gordan, Y. Haibo, Stefan E. Schulz, Michael Hietschold, Dietrich R. T. Zahn

16.30 TuP-5-14 | Conductive AFM for CNTs characterizationMarius Toader, Holger Fiedler, Sascha Hermann, Stefan E. Schulz, Thomas Gessner, Michael Hietschold

16.30 TuP-5-15 | Novel carbon nanotube film with a self-assembled carbon-metal heterostructureSascha Hermann, Steffen Schulze, Ramona Ecke, Andreas Liebig, Stefan E. Schulz, Thomas Gessner

16.30 TuP-5-16 | Topological and magnetic confinement in graphene bilayer quantum ringsMilton Pereira, Leandro Xavier, Gil de Aquino Farias, François Peeters


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16.30 TuP-5-17 | Effect of Lateral Strain on the Performance of Single Layer Graphene Field Effect TransistorsSatofumi Souma, Yusuke Ohmi, Matsuto Ogawa

16.30 TuP-5-19 | Voltage-driven ring confinement in graphene: tailoring the electronic structureLeonardo Villegas-Lelovsky, Carlos Trallero-Giner, Victor Lopez-Richard, Gilmar E. Marques

16.30 TuP-5-20 | Controllable growth and field emission of multi-layer graphene/carbon nanotube hybridsJian-Hua Deng, Guo-An Cheng

16.30 TuP-5-21 | Flux Cancelation in Magneto-Resistance of Thin Multi-Walled Carbon Nano-TubesYuichi Ochiai, Michio Kida, Hajime Asano, Nobuyuki Aoki, Takeshi Nakanishi, Jonathan P. Bird

16.30 TuP-5-22 | Relaxation dynamics in epitaxial graphene investigated in the whole infrared spectral rangeStephan Winnerl, Fabian Göttfert, Martin Mittendorff, Harald Schneider, Manfred Helm, Milan Orlita, Marek Potemski, Torben Winzer, Andreas Knorr, Ermin Malic, Michael Sprinkle, Claire Berger, Walter A. de Heer

16.30 TuP-5-23 | Ab-Initio investigation of one dimensional superlattices of graphene-like honeycomb crystalsLars Matthes, Karsten Hannewald, Friedhelm Bechstedt

16.30 TuP-5-24 | Study of Electro-mechanical Vibrations in Carbon Nanotube in The Configuration Clamped-ClampedGiovany Ruiz, Angela Camacho

16.30 TuP-5-25 | Wave packet scattering in graphene under (pseudo) magnetic fieldsAndrey Chaves, Diego Rabelo Costa, Lucian Covaci, François Peeters, Gil de Aquino Farias

16.30 TuP-5-26 | Fabrication of Graphene and Graphite Thin Films from Organic SolutionsMikihiro Kato, Keiichi Ikegami, Susumu Harako, Toshiki Ohkane, Tatuya Kobayashi, Xinwei Zhao

16.30 TuP-5-27 | Resonant Cavity Enhanced Graphene PhotodetectorsMarco Mercurio Furchi, Alexander Urich, Andreas Pospischil, Govinda Lilley, Karl Unterrainer, Hermann Detz, Pavel Klang, Aaron Maxwell Andrews, Werner Schrenk, Gottfried Strasser, Thomas Mueller

16.30 TuP-5-28 | Gated Graphene for THz PlasmonicsStefan Badescu, Robert Fitch, Dennis Walker, Justin Cleary, Joshua Hendrickson


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16.30 TUP-6 - THEORY

+16.30 TuP-6-1 | Donor D in vertically coupled quantum dots2

Ramon Manjarres-Garcia, Gene E. Escorcia-Salas, Ilia Davidovich Mikhailov, José Sierra-Ortega

+16.30 TuP-6-2 | Trion X in Vertically Coupled Type II Quantum Dots in Threading Magnetic FieldSindi Horta-Piñeres, Gene E. Escorcia-Salas, Ilia Davidovich Mikhailov, José Sierra-Ortega

16.30 TuP-6-3 | Magnetoexciton in Vertically Coupled Type II Quantum RingsJohonfri Mendoza, Gene E. Escorcia-Salas, José M. García-Díaz, Ilia Davidovich Mikhailov, José Sierra-Ortega

16.30 TuP-6-4 | Double donor complex in vertically coupled quantum dots in threading magnetic fieldRamón Manjarres-García, Gene E. Escorcia-Salas, Javir Manjarres-Torres, Ilia Davidovich Mikhailov, José Sierra-Ortega

16.30 TuP-6-5 | Aharonov-Bohm oscillation modes in non-uniform nanoring under a lateral electric fieldJairo Humberto Marin Cadavid, Ilia Davidovich Mikhailov, Willian Gutiérrez Niño

16.30 TuP-6-6 | Interfacial connement in core-shell nanowires due to high dielectric mismatchTeldo Anderson da Silva Pereira, Ariel Adorno de Sousa, Andrey Chaves, Jeanlex Soares de Sousa, Gil de Aquino Farias

16.30 TuP-6-7 | Exciton-related nonlinear optical properties in strained GaN/InN quantum wells under the effects of intense laser fieldsCarlos M. Duque, Miguel E. Mora-Ramos, Carlos A. Duque

16.30 TuP-6-8 | Inelastic light scattering by 2D electron system with SO interactionAlexander Chaplik, Lev Magarill, Ritta Vitlina

16.30 TuP-6-9 | Electronic Transport and Persistent Current in the Aharonov-Bohm RingsMohammed Shabat, Hisham Fayad

16.30 TuP-6-10 | Dispersion Relation for an Asymmetric Double-Quantum-Dot System in a Normal Magnetic FieldNorman J. M. Horing, S. L. Horton, Hilmi Ünlü

16.30 TuP-6-11 | Eigen-energy Dispersion Relation of a Kronig-Penney-type Model of a 2D Quantum Antidot Lattice in a Magnetic FieldNorman J. M. Horing, S. Bahrami, Hilmi Ünlü

16.30 TuP-6-12 | Donor impurity related Linear and nonlinear intraband optical absorption in quantum ring: Effects of applied electric field and hydrostatic pressureM. G. Barseghyan, R. L. Restrepo, Miguel E. Mora-Ramos, A. A. Kirakosyan, Carlos A. Duque

16.30 TuP-6-13 | Geometrical and applied electric field effects on 1s-like excitonic-related nonlinear optical properties of coupled quantum wellsGuillermo L. Miranda, Miguel E. Mora-Ramos, Carlos A. Duque

16.30 TuP-6-14 | Acoustic phonon modes and phononic band gaps in GaN/AlN nanowire superlatticesSeiji Mizuno


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16.30 TuP-5-15 | Nonlinear optical absorption and optical rectification in cylindrical quantum dots with asymmetric axial potential: combined effects of hydrostatic pressure, intense laser field, and applied electric fieldAlejandro Zapata, Rubén E. Acosta, Eduardo Henao, Elizabeth Aristizabal, Miguel E. Mora-Ramos, Carlos A. Duque

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16.30 THP-1 - NANOPHOTONICS AND OPTICAL CHARACTERIZATION

16.30 ThP-1-1 | Control of spins in a quantum dot by spontaneous emissionJing Wang, Ren-Bao Liu, Bang-Fen Zhu, L. J. Sham

16.30 ThP-1-2 | Photoreflectance lineshapes due to exciton continuum edge in quantum wellsAmlan Mukherjee, Sandip Ghosh

16.30 ThP-1-3 | Ultra-Low-Power Modulation of an Optically-Pumped Microdisk Laser with a Nanoelectromechanical Metal CantileverChieh-Feng Chang, Se-Heon Kim, Aditya Rajagopal, Axel Scherer

16.30 ThP-1-4 | Photoconductivity and photoluminescence under bias measurements in GaInNAs/GaAs multiple quantum wells structuresHagir Mohammed Khalil, Benjamin Royall, Simone Mazzucato, Naci Balkan, Janne Puustinen, Mircea Guina, Ville-Markus Korpijärvi

16.30 ThP-1-5 | Electric generation of vortices in polariton superfluidsMikhail Kaliteevski, Ivan Shelykh, Hugo Flayac, Goran Pavlovic

16.30 ThP-1-6 | Top-Hat HELLISH (THH)-VCSOA based on a light emitting and an absorbing for 1.3 µm wavelength operationFaten Chaqmaqchee, Naci Balkan, J. M. Ulloa, M. Hugues, Mark Hopkinson

16.30 ThP-1-7 | Gain studies of 1.3 µm dilute nitride Hellish-VCSOA for optical communicationsFaten Chaqmaqchee, Naci Balkan, M. Hugues, Mark Hopkinson

16.30 ThP-1-8 | Anomalous paramagnetic shift of annealed nonmagnetic quantum dotsEmanuela Margapoti, Victor Lopez-Richard, Suddhasatta Mahapatra, Lukas Worschech, Karl Brunner, Qu Fanyao, Carlos Destefani, Eduardo Menéndez-Proupin, Catherine Bougerol, Gilmar E. Marques

16.30 ThP-1-9 | Exploiting spin phenomena of exciton and trions in 2D systemsLeonardo K. Castelano, Daniel Cesar, Victor Lopez-Richard, Gilmar E. Marques, Odilon Couto Jr., Fernando Iikawa, Rudolf Hey, Paulo Santos

16.30 ThP-1-10 | Metafluid with anisotropic dynamic massJesus Arriaga, Arkady Krokhin, Ludmila Gumen

16.30 ThP-1-11 | Polarized photoreflectance and photoluminescence spectroscopy of InGaAs/GaAs quantum rods grown with As and As 2 4

sourcesRamūnas Nedzinskas, Bronislovas Čechavičius, Julius Kavaliauskas, Vytautas Karpus, Gintaras Valušis, Lianhe H. Li, Suraj P. Khanna, Edmund H. Linfield

16.30 ThP-1-12 | Electromagnetic waves in a cylindrical superlattice waveguide structureMohammed Shabat

16.30 ThP-1-13 | Picosecond carrier dynamics induced by coupling of wavefunctions in Si-nanodisk arrays fabricated using bio-templatesTakayuki Kiba, Yoshiya Mizushima, Makoto Igarashi, Seiji Samukawa, Akihiro Murayama

16.30 ThP-1-14 | Fourier transformed modulation spectroscopy in the mid and long wavelength spectral rangeMarcin Motyka, Filip Janiak, Grzegorz Sek, Krzysztof Ryczko, Jan Misiewicz

Poster Session • Thursday, July 26, 2012

15

16.30 ThP-1-15 | Intrinsic optical confinement for ultrathin InAs/GaAs/GaP quantum well superlatticesAbdallah Sakri, Cédric Robert, Laurent Pedesseau, Charles Cornet, Jacky Even, Jean-Marc Jancu

16.30 ThP-1-16 | Photoluminescence polarization in strained GaN/AlGaN core/shell nanowire heterostructuresPierre Lavenus, Gwénolé Jacopin, Lorenzo Rigutti, Sara Bellei, François H. Julien, Albert Davydov, Denis Tsvetkov, Kris Bertness, Maria Tchernycheva

2+16.30 ThP-1-17 | Synthesis and enhanced blue emission of Eu -doped GaN/SiO 2

nanocomposites by addition of SiO nanoparticles2

Kang Bong Kyun, Kim Myung-Oh, Yoon Dae Ho

16.30 ThP-1-18 | Mode structure of photonic wires in an organic microcavity in three dimensionsFelix Lemke, Susanne Hintschich, Andreas Mischok, Christoph Reinhardt, Vadim Lyssenko, Alexander Zakhidov, Robert Brückner, Hartmut Fröb, Karl Leo

16.30 ThP-1-19 | Laser-induced thermal diffusion of Mn-interstitials and Stark spectroscopy in nano-LEDsAteeq Nasir, Oleg Makarovsky, Santosh Kumar, Mike W. Fay, Richard Campion, Laurence Eaves, Armando Rastelli, Oliver G. Schmidt, Amalia Patanè

16.30 ThP-1-20 | Thickness dependence of photoluminescence of heavily-doped GeOIDandan Zhao, Choong Hyun Lee, Tomonori Nishimura, Kosuke Nagashio, Guo-An Cheng, Akira Toriumi

16.30 ThP-1-21 | DIMENSIONALITY AND ASPECT RATIO EFFECTS ON THE NONLINEAR OPTICAL RESPONSE OF EXCITON STATES IN SEMICONDUCTOR NANOSTRUCTURESHanz Ramirez, Jeff Florez, Angela Camacho

16.30 ThP-1-22 | Time-resolved photoluminescence studies of Ga(AsBi)/GaAs single quantum wellsMohammad Khaled Shakfa, Dimitri Kalincev, Alexej Chernikov, Sangam Chatterjee, Martin Koch, Xianfeng Lu, Shane R. Johnson, Dan A. Beaton, Thomas Tiedje

16.30 ThP-1-23 | Multi-exciton emission of ordered SiGe island ensemblesPetr Klenovský, Florian Hackl, Elisabeth Lausecker, Moritz Brehm, Vlastimil Křápek, Hubert Steiner, Thomas Fromherz, Josef Humlíček, Friedrich Schäffler, Günther Bauer

16.30 ThP-1-24 | Optically in-well pumped VECSEL emitting beyond 3 µmAmir Khiar, Michael Witzan, Martin Eibelhuber, Astrid Hochreiner, Thomas Schwarzl, Hans Zogg, Gunther Springholz

16.30 ThP-1-25 | Enhanced second harmonic generation from periodic polarity-inverted GaN waveguideRyuji Katayama, Yujiro Fukuhara, Masahiro Kakuda, Shigeyuki Kuboya, Kentaro Onabe, Tomonori Matsushita, Takashi Kondo, Hiroyuki Yaguchi, Takashi Matsuoka

16.30 ThP-1-26 | Detectivity Improvement of Quantum Well Infrared Photodetectors using a Photonic Crystal Slab as Resonant CavityPeter Reininger, Stefan Kalchmair, Hermann Detz, Tobias Zederbauer, Aaron Maxwell Andrews, Werner Schrenk, Gottfried Strasser

16.30 ThP-1-27 | Free-Carrier Refractive Index Contributions and Tuning Performance of InGaAsP Laser DiodesGeorgios Kyritsis, Nick Zakhleniuk


16

16.30 THP-2 - NANOELECTRONICS AND TRANSPORT

16.30 ThP-2-1 | An analysis of Hall mobility in as-grown and annealed n- and p-type modulation doped Ga In N As /GaAs quantum wells0.68 0.32 y 1-y

Fahrettin Sarcan, Omer Donmez, Mustafa Gunes, Ayse Erol, M. Cetin Arikan, Janne Puustinen, Mircea Guina

16.30 ThP-2-2 | 3D Modeling of FINFETSamson Mil'shtein, Brian Zanchi

16.30 ThP-2-3 | Magnetoresistance and Hall Effect studies in n- and p-type GaInNAs/GaAs modulation doped quantum well structuresMustafa Gunes, Metin Aslan, Ferhat Nutku, Ayse Erol, M. Cetin Arikan

16.30 ThP-2-4 | Low-temperature electronic transport mechanisms deduced from noise measurements in quantum-well infrared photodetectorsFernando Massa Fernandes, Alvaro Diego Bernardino Maia, Marcel Dos Santos Claro, Euzi Conceição Fernandes da Silva, Alain Andre Quivy, Marcela de Freitas Mendonça, Gustavo Soares Vieira, Nancy Mieko Abe, Roberto Yuji Tanaka, Angelo Passaro

16.30 ThP-2-5 | Hydrogen ad-atoms resonant tramps in graphene nanoribbonsMonica Pacheco, Jhon González, Luis Rosales

16.30 ThP-2-6 | The role of dislocation-induced scattering in electronic transport in Ga In N alloysx 1-x

Omer Donmez, Mustafa Gunes, Ayse Erol, M. Cetin Arikan, Naci Balkan, William Schaff

16.30 ThP-2-7 | Fine tuning of single barrier thermal resistance in Ge/Si multilayersPeixuan Chen, Jianjun Zhang, Armando Rastelli, Oliver Schmidt

16.30 ThP-2-8 | A Study on Structural and Electronic Properties of GaAsN and GaAsBi AlloysMetin Aslan, Battal Gazi Yalcin

16.30 ThP-2-9 | Transport through nanoscopic 3D constrictionsPedro Pereyra, Stefan Geisler, Dieter Weiss

16.30 ThP-2-10 | Quantum transport through aromatic moleculesJudith Ojeda, R. R. Rey-González

16.30 ThP-2-11 | Effect of localized magnetic moments configurations on the dynamics of electron wave packet -- phase-space approach.Maciej Wołoszyn, Bartłomiej Spisak

16.30 ThP-2-12 | Electron transport properties of MoS2 Nanotubes and NanoribbonsEzgi Erdogan, Gotthard Seifert

16.30 ThP-2-13 | Photoelectrochemical characteristics of one dimensional nanostructured silicon for optoelectronic applicationsShao-Long Wu, Guo-An Cheng, Rui-Ting Zheng, Ting Zhang

16.30 ThP-2-14 | Andreev levels in semiconductor nanowire Josephson junction with strong spin-orbit interactionTomohiro Yokoyama, Mikio Eto, Yuli Nazarov

16.30 ThP-2-15 | Tunneling Through Nanowire Double Quantum Dot With Phonon InteractionFikeraddis Ahmed Damtie, Olov Karlström, Carina Fasth, Andreas Fuhrer, Lars Samuelson, Andreas Wacker


17

16.30 ThP-2-16 | Hole mobility in InP nanowires: effects of temperature, strain and widthMariama Rebello Sousa Dias, Adalberto Picinin, Victor Lopez-Richard, Sergio E. Ulloa, Leonardo K. Castelano, José Pedro Rino, Gilmar E. Marques

16.30 ThP-2-17 | Current transport through single moleculesArtur Erbe, Youngsan Kim, Jannic Wolf, Thomas Huhn, Elke Scheer

16.30 ThP-2-18 | The electron gas in GaAs/AlGaAs modulation doped co-axial nanostructuresGuido Goldoni, Andrea Bertoni, Miguel Royo Valls

16.30 ThP-2-19 | Tuning electrical and magnetic properties of cellulose films by Au nanoparticlesLyudmila Turyanska, Oleg Makarovsky, Amalia Patane, Nadezhda Kozlova, Zhiming Liu, Mei Li, Stephen Mann

16.30 ThP-2-20 | Quantum well infrared photodetector based on an intersubband transition between the ground and a continuum localized statesGermano M. Penello, Patrícia L. Souza, Marcos H. Degani, Rudy Massami Kawabata, Mauricio P. Pires, Daniel N. Micha, Roberto Jakomin, Nelson Studart

16.30 ThP-2-21 | Time-dependent calculation of the transport properties of semiconductor porous layersJeanlex S. de Sousa, Francisco W. N. Silva, Ascânio D. Araújo, Gil de Aquino Farias

16.30 ThP-2-22 | Improved noise properties of unipolar nanodiodes at elevated temperaturesShahrir R. Kasjoo, Linqing Zhang, Yasaman Alimi, Arun K. Singh, Claudio Balocco, Aimin Song

16.30 ThP-2-23 | Overshoot Mechanism of Transient Excitation of THz and Gunn Oscillations in Wide Bandgap SemiconductorsErnesto Momox, Nick Zakhleniuk, Naci Balkan, Muhammet Okur


18

16.30 THP-3 - SPINTRONICS

16.30 ThP-3-1 | Theory of spin transport in Ferromagnetic metal with nonuniform spin-orbit interactionKazuhiro Hosono, Kazuhiro Tsutsui, Takehito Yokoyama, Yukio Nozaki

16.30 ThP-3-2 | Spin polariton population transfer effectVictor S. Comitti, Marina B E. da Silva, Franklin M. Matinaga

16.30 ThP-3-3 | Synthesis, structural and magnetic characterization of Ti Co O 1-x x 2

diluted magnetic oxideTalita Evelyn Souza, Patrícia Covre, Alexandre Mesquita, Person Pereira Neves, Antonio Carlos Doriguetto Doriguetto, Valmir Antonio Chitta, Hugo Bonette de Carvalho

16.30 ThP-3-4 | Uniaxial magnetic anisotropy in1-dimensional Fe nanostructures on Al O (0001) induced by oblique deposition2 3

Wen-Chin Lin, Chiao-Sung Chi, Bo-Yao Wang, Way-Faung Pong, Tsung-Ying Ho, Fang-Yuh Lo, Cheng-Jui Tsai

16.30 ThP-3-5 | Spin polarization in double barrier diodes incorporating InAs self-assembled quantum dotsJ. A. Nóbrega, V. O. Gordo, H. V. A. Galeti, Marcio Teodoro, Y. Galvão Gobato, Gilmar E. Marques, Milan Orlita, D. K. Maude, Mohamed Henini, D. Taylor

16.30 ThP-3-6 | Spin Hall effect in a semiconductor waveguideJose Luis Cardoso

16.30 ThP-3-7 | Spin polarization of carriers in Si delta-doped structuresL. K. S. Herval, V. O. Gordo, H. V. A. Galeti, Y. Galvão Gobato, Gilmar E. Marques, D. Taylor, Mohamed Henini

16.30 ThP-3-8 | Non linear transport model for the giant spin-dependent photo-conductivity in GaAsN dilute nitride semiconductorsAlejandro Kunold, Pedro Eduardo Roman-Taboada, Juan Carlos Sandoval-Santana, Andrea Balocchi, Helene Carrere, Thierry Amand, Naoufel Ben Abdallah, Jean-Christophe Harmand, Xavier Marie

16.30 ThP-3-9 | Polarization-resolved magneto-photoluminescence of InGaAs(N)/GaAs quantum wellsL. K. S. Herval, V. O. Gordo, Vivaldo Lopes-Oliveira, A. Khatab, M. P. F. de Godoy, Y. Galvão Gobato, Gilmar E. Marques, M. J. S. P. Brasil, Mohamed Henini, M. Sadeghi, S. Wang

16.30 ThP-3-10 | Localization effects in InGaAsN/GaAsN /GaAs quantum wells grown on (100) and (311)A GaAs substratesV. O. Gordo, L. K. S. Herval, A. Khatab, M. P. F. de Godoy, Y. Galvão Gobato, M. J. S. P. Brasil, Gilmar E. Marques, Mohamed Henini

16.30 ThP-3-11 | Amplification of spin-dependent recombination ratio and spin polarization in GaAsN dilute nitride semiconductor heterostructures through an external magnetic field in Faraday configuration.Miguel Romero-Serrano, Alejandro Kunold, Andrea Balocchi, Helene Carrere, Thierry Amand, Naoufel Ben Abdallah, Jean-Christophe Harmand, Xavier Marie

16.30 ThP-3-12 | Engineering a spin-fet: spin-orbit phenomena and spin transport induced by a gate electric fieldHugo Hernández-Saldaña, Jose Luis Cardoso


19

16.30 ThP-3-13 | Modulation of Spin-transport in a Magnetic Superlattice for Spin Filter ApplicationNammee Kim, Heesang Kim, Jinwoo Kim

16.30 ThP-3-14 | Geometric effect on spin-pumping-induced inverse spin Hall effect in permalloy/platinum filmsHiroyasu Nakayama, Kazuya Ando, Kazuya Harii, Tatsuro Yoshino, Ryo Takahashi, Yosuke Kajiwara, Ken-Ichi Uchida, Yasunori Fujikawa, Eiji Saitoh

16.30 ThP-3-15 | Magnetic Mn Ge nanocrystals embedded in crystalline Ge: a 5 3

magnet/semiconductor hybrid synthesized by ion implantationShengqiang Zhou, A. Shalimov, Wenxu Zhang, D. Buerger, A. Muecklich, Manfred Helm, H. Schmidt

16.30 ThP-3-16 | Spin polarization of electrons in quantum wireAlexander Vasilchenko, Alexey Bunyakin

16.30 ThP-3-17 | Conductance oscillations in a (Ga,Mn)As point contact deviceStefan Geißler, Alexei Iankilevitch, Martin Utz, Dieter Schuh, Dominique Bougeard, Dieter Weiss

16.30 ThP-3-18 | A Study on the Correlation Between Structural and Magnetic Properties of Co-doped Oxide Nanoparticles: ZnO and CeO2

Vinícius Dantas Araújo, Maria Inês Basso Bernardi, Waldir Avansi, Valmir Antonio Chitta, Fanny Béron, Kleber Roberto Pirota, Alexandre Mesquita, Hugo Bonette de Carvalho

16.30 ThP-3-19 | Spin injection in n-type resonant tunneling diodesY. Galvão Gobato, H. V. A. Galeti, L. F. Dos Santos, Victor López-Richard, Daniel Cesar, Gilmar E. Marques, M. J. S. P. Brasil, Milan Orlita, J. Kunc, D. K. Maude, Mohamed Henini, R.j. Airey

16.30 ThP-3-20 | Voltage controlled spin polarization in p-type GaAs/AlAs double barrier structuresH. V. A. Galeti, Anibal T. Bezerra, Y. Galvão Gobato, M. J. S. P. Brasil, Daniel Cesar, Victor López-Richard, Gilmar E. Marques, Mohamed Henini, D. Taylor

16.30 ThP-3-21 | Low field polar magneto-optical Kerr effect study of excitons in GaAs/Al Ga As single quantum well0.3 0.7

Ashish Arora, Sandip Ghosh

16.30 ThP-3-22 | The oxygen vacancy influence on magnetic properties of the Fe- and Co-doped SnO diluted alloys: a theoretical investigation2

Pablo D Borges, Luísa M. R. Scolfaro, Horacio W. Leite Alves, Eronides F da Silva Jr., Lucy V C Assali

16.30 ThP-3-23 | COUPLING EFFECTS ON PHOTOLUMINESCENCE OF EXCITON STATES IN ASYMMETRIC QUANTUM DOT MOLECULESNelson Fino, Hanz Ramirez, Angela Camacho


20

16.30 THP-4 - EMERGING MATERIAL AND DEVICES

16.30 ThP-4-1 | Mg-doped indium rich Ga In N: evidence for p-type conductivityx 1-x

Naci Balkan, Engin Tiras, Ayse Erol, Mustafa Gunes, Sukru Ardali, M. Cetin Arikan, Delphine Lagarde, Helene Carrere, Xavier Marie, Cebrail Gumus

16.30 ThP-4-2 | The ionization potential and electron detachment energy of small aluminum clustersLadir Cândido, José N. Teixeira Rabelo, Guo-Qiang Hai

16.30 ThP-4-3 | Determination of Operation Region in Silicon-Nanowire BioFETs to Maximize Signal-to-Noise RatioSungho Kim, Taiuk Rim, Kihyun Kim, Eunhye Baek, Unsang Lee, Nanki Hong, Changki Baek, Sooyoung Park, Jeong-Soo Lee, Yoon-Ha Jeong

16.30 ThP-4-4 | Investigation of Photoconductive Properties of ZnO nanoparticlesAyse Erol, Salih Okur, M. Cetin Arikan, Bulent Comba

16.30 ThP-4-5 | Intrinsic Reliability Improvement of SiGe Quantum Well pMOSFETsDo-Young Choi, Chang-Woo Sohn, Hyun-Chul Sagong, Eui-Young Jung, Jun-Woo Jang, Chang-Ki Baek, Jeong-Soo Lee, Yoon-Ha Jeong

16.30 ThP-4-6 | Characterization of as-grown and annealed modulation doped Ga1-

In N As /GaAs quantum well structures using Infrared spectroscopy and x x y 1-y

Raman scattering techniquesElif Akalin, Ayse Erol, Sevim Akyuz, M. Cetin Arikan, Janne Puustinen, Mircea Guina

16.30 ThP-4-7 | Generation of Ultra-Violet Sub-nanosecond Optical Pulses from AlGaN LEDsPierre Renucci, Phi Hoa Binh, Cong Tu Nguyen, Tiantian Zhang, Xavier Marie

16.30 ThP-4-8 | Enhancement of Room Temperature Magnetoresistance in Non-Uniform Size and Distribution of Clusters in Polyaniline-Iron Oxide NanocompositesAigu Lin, Andrew Wee, Wei Chen, Tom Wu

+16.30 ThP-4-9 | Effect of energy and fluence of energetic N ions on the formation 2

of silicon nitride on Si(111) substratePraveen Kumar, S. M. Shivaprasad

16.30 ThP-4-10 | The effect of 1-dimensional nanostructure prepared by solvent treatment of photoactive layer on the performance of polymer solar cellSungho Woo, Jaehoon Jung, Hong-Kun Lyu, Wookhyun Kim, Hyunmin Park, Jihee Jung, Youngkyoo Kim

16.30 ThP-4-11 | Assembling of palladium nanoparticles at vanadium dioxide nanowire surface using dielectrophoresisYoungreal Kwak, Gil-Ho Kim, Ji-Won Byon, Jeong Min Baik

16.30 ThP-4-12 | Electronic properties of ZnO and NB hexagonal monolayersA. M. Rojas-Cuervo, J. D. Rojas Bonilla, R. R. Rey-González

16.30 ThP-4-13 | Transmission electron microscope observation of organic-inorganic hybrid thin active layers of light-emitting diodesYusuke Jitsui, Naoki Ohtani

16.30 ThP-4-14 | Nano-scale Field Effect Transistors for Bio-sensing ApplicationsAditya Rajagopal, Chieh-Feng Chang, Sameer Walavalkar, Axel Scherer


21

16.30 ThP-4-15 | Dilute Nitride nipi Solar CellsNaci Balkan, Benjamin Royall

16.30 ThP-4-16 | Sensor based on Coplanar μ-Strips to Measure the Electronics Properties of the Polyethylene Oxide (PEO) ElectrospunCarlos Fuhrhop

16.30 ThP-4-17 | Novel polymer-coated magnetic nanoparticles for controlled delivery of doxorubicinAbolfazl Akbarzadeh, Soodabeh Davaran

16.30 ThP-4-19 | Properties of Si/SiO quantum well structure on Al O /Si x 2 3

substrates for photovoltaic applicationsKwang-Ho Kim, Ji-Hoon Kim, Pyung Woo Jang, Chi Sup Jung, Kyu Seomoon

16.30 ThP-4-20 | Fabrication of Fe-Al Nanoparticles by Selective Oxidation of Fe-Al Thin FilmsPyung Woo Jang, Seungchan Shin, Kwang-Ho Kim, Chi Sup Jung, Kyu Seomoon

16.30 ThP-4-21 | Study on the surface reflectivity in an early stage of Al MOCVD for photovoltaic applicationsKyu Seomoon, Jongin Lee, Pyung Woo Jang, Chi Sup Jung, Kwang-Ho Kim

16.30 ThP-4-22 | Two Dimensiomal Ferroelectric Copolymer P(VDF-TrFE) Langmuir monolayerChi Sup Jung, Pyung Woo Jang, Hyun Kyu Park, Kwang-Ho Kim, Kyu Seomoon


22

16.30 THP-5 - THEORY

16.30 ThP-5-1 | Relaxation Mechanism in the Optical Recombination Process of Quantum Dot EnsemblesDaniel Cesar, Marcio Teodoro, Victor Lopez-Richard, Gilmar E. Marques, Euclydes Marega Jr., Vitaliy Dorogan, Yu Mazur, Gregory Salamo

16.30 ThP-5-2 | TRANSPORT AND THERMODYNAMICAL PROPERTIES OF QUASI TWO-DIMENSION ELECTRON GASA. C. A. Ramos, Gil de Aquino Farias, N. S. Almeida

16.30 ThP-5-3 | Effects of an intense, high-frequency laser field on bound states in Ga In N As /GaAs double quantum well1-x x y 1-y

Fatih Ungan, Serpil Sakiroglu, Esin Kasapoglu, Ayse Erol, M. Cetin Arikan, Huseyin Sari, Ismail Sökmen

16.30 ThP-5-4 | Theoretical luminescence spectra in p-type superlattices based on InGaAsNSara C. P. Rodrigues, Thiago F. de Oliveira, Luísa M. R. Scolfaro, Guilherme M. Sipahi, Eronides F. da Silva Jr.

16.30 ThP-5-5 | Three-Particle Quantum System in a Disconnected Structure: -Trion X in Two Vertically Coupled Rings and a Coaxial Wire

Marlon R. Fulla, Jairo Marín, Diego Ospina

16.30 ThP-5-6 | EXCITON BINDING ENERGY OF GA-AS IN SYMMETRICAL NARROW NANOTUBE WITH TWO QUANTUM WELL UNDER MAGNETIC FIELDJesus Gonzalez, Jader Gonzalez, Jose Barba

16.30 ThP-5-7 | Energy Structure of an Excitonic System Confined in a Quantum Ring and a Perpendicular Side-Coupled WireMarlon R. Fulla, Jairo Marín

16.30 ThP-5-8 | Coherent control of intersubband quantum well transitions with ultrashort electromagnetic pulsesEmmanuel Paspalakis, John Boviatsis

16.30 ThP-5-9 | The effect of magnetic field on the impurity binding energy of shallow donor impurities in a Ga In N As /GaAs quantum well1-x x y 1-y

Unal Yesilgul, Serpil Sakiroglu, Carlos A. Duque, Miguel E. Mora-Ramos, Esin Kasapoglu, Huseyin Sari, Ismail Sökmen

16.30 ThP-5-10 | Theoretical analysis of the bias influence on infrared photo- and dark currents in Al Ga As/GaAs multiple quantum well structures with 0,15 0,85

Al Ga As tunneling barriers0,3 0,7

Anibal T. Bezerra, Marcos H. Degani, Marcelo Z. Maialle, Paulo F. Farinas, Nelson Studart

16.30 ThP-5-12 | A SOLVABLE MODEL OF NON-UNIFORM EXCITON VOLCANO-SHAPED QUANTUM DOTF. A. Rodriguez Prada, L F García, Ilia Davidovich Mikhailov

16.30 ThP-5-15 | Charge Transfer Magnetoexciton Formation at Vertically Coupled Quantum DotsWillian Gutiérrez Niño, Jairo Humberto Marin Cadavid, Ilia Davidovich Mikhailov

16.30 ThP-5-16 | Giant resonant tunneling in multi-barrier structures under longitudinal and transverse fieldsM. Guadalupe Mendoza-Figueroa, Pedro Pereyra


23

16.30 ThP-5-17 | Role of topological structure in electronic properties of inhomogeneous 3D Möbius ringsVladimir M. Fomin, Oliver G. Schmidt

16.30 ThP-5-18 | Tight binding simulation of type-II superlattice absorptionSoline Boyer-Richard, Cédric Robert, Lionel Gérard, Jan-Peter Richters, Joël Bleuse, Régis André, Henri Mariette, Jacky Even, Jean-Marc Jancu

16.30 ThP-5-19 | Optical modes in cylindrical nanostructuresCarlos Trallero-Giner, Rolando Pérez-Alvarez, Dario G. Santiago-Perez, Leonor Chico

16.30 ThP-5-20 | How effective parameters of elastic superlattice are related to phase and group velocity of soundLyudmila Gumen, Edgar Reyes, Jesus Arriaga, Arkadii Krokhin

16.30 ThP-5-22 | First principles derivation of a position-dependent mass Schrödinger equation.Raimundo Costa, Murilo Almeida, Gil de Aquino Farias, José Andrade

16.30 ThP-5-23 | Tight-binding calculations of Ga(NAsP)/GaP(N) quantum wells for photonic integration on siliconCédric Robert, Mathieu Perrin, Charles Cornet, Olivier Durand, Jacky Even, Jean-Marc Jancu

16.30 ThP-5-24 | III-nitrides multiple quantum wells electronic structures and heterojunctions band alignments calculated using local density approximation with self-energy correctionsLara Kühl Teles, Marcelo Marques, Ronaldo R. Pela, Mauro Ribeiro Jr., Luiz Guimaraes Ferreira

16.30 ThP-5-25 | Quantum Confinement and Electronic Properties of GaN, ZnO and Si NanowiresLara Kühl Teles, Mauro Ribeiro Jr., Pedro H. G. Oliveira, Marcelo Marques, Ronaldo R. Pela, Luiz Guimaraes Ferreira, Juergen Furthmueller

16.30 ThP-5-26 | Electronic Band Structure of L-Diphenylalanine NanotubeTarciso Andrade-Filho, Wendel Andrade Alves, Alexandre Reily Rocha

16.30 ThP-5-27 | Electronic Raman Scattering in Quantum WellsAlison Arantes, Virgilio Anjos


24

Abstracts – Poster Presentation

25

TuP1-1 | Optimization of the number of quantum well pairs forHigh Bright AlGaInP-based Light Emitting Diodes (#16)Hwa Sub Oh 1, Hyung Joo Lee2, Young Jin Kim2

1Korea Photonics Technology Institute LED device research center, Wolchul-dong Buk-gu, 971-35, Gwangju 500-460, Korea Republic (South)2AUK Incorporation Process engineering department, Eoyang-dong, 513-37,Iksan 540-742, Korea Republic (South) ContentFor high bright light emitting diodes (LEDs) appropriate to general lightingapplications, we have investigated the temperature dependent PL characteristicsand the device performances according to the number of QW pairs. As thenumber of quantum well pairs (QWs) is increased from 2 to 35 pairs, internalquantum efficiency and device performances are significantly improved owing tothe suppression of carrier overflow by decreasing the carrier density in activeregion and increasing the effective barrier potential. At further increase in thenumber of QWs to 50 pairs, the optical and device performances are started todegrade owing to the increase of internal loss in the active region like a wellvolume itself acting as light absorbing layer and aluminum oxide complexes inthe barrier.

Figure 1:Behaviors of internal quantum efficiency according to the number of QW pairs

Figure 2:Behaviors of I-V characteristics and light output power (Pout) of devices according to the number of QWpairs

27

TuP1-2 | Self Assembled Nano Structured Al2O3 Incorporated PIThin Film: A Smart Material (#71)Shailendra Kumar Tiwary 1, Anand Kumar Gupta2

1Jabalpur Engineering College Department of Applied Physics, Gokulpur,Madhya Pradesh, Jabalpur 482011, India 2Global Institute of Engineering Department of Engineering Physics, PatanBypass Square, Karmeta, Madhya Pradesh, Jabalpur India ContentThe inorganic material structured polyimide (PI) composite films are viewed asthe revolutionary material, which will play significant role in the present era ofmodern technology. The aluminum oxide (Al2O3) particles were made to dispersein micro/ nano meter regime within polyamic acid, which is precursor to PI. TheAl2O3/PI composite obtained were subsequently thermally imidized up to 350°C.The incorporation of Al2O3 particles within PI matrix was analyzed using FT-IR.The degree of crystallinity, and crystallite size were evaluated using XRD, andAFM technique. The electrical properties were analyzed using UV-VISspectroscopy and four-probe technique. The resultant product exhibits goodproperties due to decrease in free volume space and increase in the surfaceenrichment providing reinforcement to matrix, which may be attributed to thefunctional characteristic either that of the Al2O3 particle itself or particles withspecial structure within the PI matrix and provides means to achieve excellentcombination of micromechanical, thermal and hydraulic resistance with improvedstructural morphology in comparison to unmodified PI film.

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TuP1-3 | Growth Kinetics of MPS-capped CdS Quantum Dots inSelf-assembled Thin Films (#86)Kenan Koç 1, Fatma Zehra Tepehan2, Galip G. Tepehan3

1Yildiz Technical University Department of Physics, Esenler, 34210 Istanbul,Turkey 2Istanbul Technical University Department of Physics, Maslak, 34469 Istanbul,Turkey 3Kadir Has University Faculty of Arts and Sciences, Fatih, 34083 Istanbul, Turkey ContentThe present study aimed to investigate the growth kinetics of 3-mercaptopropyltrimethoxysilane (MPS) capped CdS quantum dots as self-assembled thin films. Colloidal quantum dots were self-assembled directly on aglass substrate by sol-gel spin coating method without introducing any matrix.The growth kinetics were investigated by heat treating the substrates in between225oC and 325oC at the specified time intervals. Growth kinetics of MPS-cappedCdS quantum dots were investigated using absorbance measurements. Theresults showed that sizes of CdS quantum dots were grown from 2.9 to 4.6 nmand 1s-1s transition energy values (E1s1s ) were shifted from 3.2 to 2.7 eV.Increament of the average size of the quantum dots by therm al treatment is dueto Oswald ripening. The thermal process used for the growth of the size ofquantum dots was examined using Lifshitz-Slyozov-Wagner (LSW) theory. Theactivation energy of CdS quantum dots was calculated as 44 kJ/mol. References1- Koç, K., Tepehan, F.Z. and Tepehan, G.G., 2011. Characterization of MPS Capped CdS Quantum Dots andFormation of Self-Assembled Quantum Dots Thin Films on a Glassy Substrate, Chalcogenide Letters, 8, 239- 247. 2-Rao, C.N.R., Müller, A. and Cheetham, A.K., 2007. Growth of Nanocrystals in Solution, in Nanomaterials chemistry:recent developments and new directions, Wiley-Vch Verlag GmbH & Co., Weinheim. 3- Guglıelmı, M., Martuccı, A.,Menegazzo, E., Rıghını, G.C., Pellı, S., Fıck, J. and Vıtrant, G., 1997. Control of semiconductor particle size in sol-gelthin films, Journal of Sol-Gel Science and Technology, 8, 1017-1021. 4- Sung, Y.-M. Park, K.-S., Lee, Y.-J. and Kim,T.-G., 2007. Ripening kinetics of CdSe/ZnSe core/shell nanocrystals, J. Phys. Chem. C, 111, 1239-1242. 5- Wei C-M. and Hou S-S., 2007, Preparation and optical properties of blue-emitting colloidal CdS nanocrystallines by thesolvothermal process using poly (ethylene oxide) as the stabilizer, Colloid Polym Sci., 285, 1343-1349

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Figure 1:Plots of the cubic term of radius of CdS quantum dots as a function of heat treatment time andtemperature.

Figure 2:1s-1s transition energy values of CdS quantum dots as a function of heat treatment time and temperature.

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TuP1-4 | Probability of Twin Formation on Self-catalyzed GaAsNanowires on Si Substrate (#168)Masahito Yamaguchi , Jihyun Paek, Hiroshi AmanoNagoya Umiversity Department of Electrical Engineering and Computer Science,C3-1 Furo-cho, Chikusa-ku, Aichi, Nagoya 464-8603, Japan ContentIII-V compound semiconductor nanowires (NWs) are attracting much attention asfundamental structures of novel optical and electronic devices. Especially, vapor-liquid-solid (VLS) NWs grown on Si substrates have been investigated for anopto-electronic integrated circuit. However, twin boundaries are formed in theNWs during growth. The twin boundaries degrade the optical and/or electronicproperties. Therefore, we attempted to control incorporation of twin boundaries inself-catalyzed GaAs NWs and the probability of twin formation was discussedthermodynamically in detail. The self-catalyzed GaAs NWs were grown on the Sisubstrate under various arsenic pressures by MBE-VLS method which iscombined molecular beam epitaxy (MBE) with VLS method [1]. When the arsenicpressure is low, wurtzite structures are dominant. On the other hand, zinc-blendstructures become dominant as the arsenic pressure rises. When we assumethat one monolayer of wurtzite structure is the twin boundary, the probability ofoccurrence of wurtzite nucleus means that of twin boundary. Therefore, wecalculated the supersaturation of arsenic adatom on the gallium droplet surfaceand the change in free energy, and estimated the probability of occurrence oftwin boundary. When we calculate the change in free energy, we assume thatthe rhombic nucleation occurs at the edge of the VLS triple phase interface asshown in Fig. 1 (a). Figure 1 (b) shows the estimated results of the probability ofoccurrence of twin boundary. The probability of occurrence of twin boundarydecreases as the arsenic adatom on the gallium droplet surface increases. Thisresult is similar to the experimental result. This suggests that we can control theincorporation of twin boundaries in self-catalyzed GaAs NWs by varying thearsenic pressure. Acknowledgement: This work was partly supported by theGrant-in-aid for Scientific Research (KAKENHI) No. 23510148 of Japan societyfor the Promotion of Science (JSPS). References [1] J.H. Paek, T. Nishiwaki, M. Yamaguchi, and N. Sawaki, phys. stat. sol., 6 (2009) 1436.

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Fig.1:(a) Nucleation model on NW (b) Arsenic adatoms dependence of twin boundary probability.

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TuP1-6 | In-plane mapping of buried InGaAs quantum rings andhybridization effects on the electronic structure (#313)Marcio Daldin Teodoro 1, Angelo Malachias2, Vivaldo Lopes-Oliveira1, DanielFerreira Cesar1, Victor Lopez-Richard1, Gilmar Eugenio Marques1, EuclydesMarega Jr.3, Mourad Benamara4, Yuriy Mazur4, Gregory J. Salamo4

1Universidade Federal de São Carlos Departamento de Física, RodoviaWashington Luiz, São Carlos, São Paulo, 13565905, Brazil 2Universidade Federal de Minas Gerais Departamento de Física, Belo Horizonte,Minas Gerais, Brazil 3Universidade de São Paulo Instituto de Física de São Carlos, São Carlos, SãoPaulo, Brazil 4University of Arkansas Arkansas Institute for Nanoscale Materials Science andEngineering, Fayetteville, Arkansas United States ContentThis work reports an investigation on the structural differences between InAsquantum rings and their precursor quantum dots species, as well as on thepresence of piezoelectric fields and asymmetries in these nanostructures. Theresults show a significant reduction in the ring dimensions when the sizes ofcapped and uncapped ring and dot samples are compared. The iso-latticeparameter mapping obtained from Grazing-incidence X-ray diffraction hasrevealed the lateral extent of strained regions in the buried rings. A comparisonbetween strain and In-composition of dot and ring structures allows inferring howthe ring formation and its final configuration may affect optical responseparameters. Based on the experimental observations, we also discuss theeffective potential profiles which emulate the ring-shape confinements. Theeffects of confinement and strain field modulation on electron and hole bandstructures are simulated by a multiband k.p calculation. With the experimentalresults available, the high levels of subband hybridization in the valence band,we also calculate the conditions for tuning the angular momentum of carriers inorder to achieve non-zero values in the absence of magnetic fields.

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TuP1-7 | GeSi quantum dots and quantum wells growth onSi(100) surface by MBE (#352)Aleksandr Nikiforov , Vyacheslav Timofeev, Serge Teys, Anton Gutakovsky,Oleg PchelyakovISP SB RAS MBE, Lavrentjeva 13, 630090 Novosibirsk, Russia ContentThe great practical interest are Ge/GexSi1-x/Ge heterosystems with alternatinglayers of quantum dots and solid solution layers for obtaining of mid-infraredphotodetectors based on intraband transitions [1]. In the system arise intrabandtransitions of charge carriers from quantum dot levels to two-dimensional sub-bands of the solid solution film [2]. There are available numerous papers thatreport studies of early stages of germanium growth on the Si(100) surface butonly few data on the influence of GexSi1-x layer on the wetting layer thickness and“hut”-“dome” transition [3, 4]. A Katun-C MBE installation equipped with twoelectron beam evaporators for Si and Ge was used for synthesis. The criticaltransition thicknesses are observed to decrease to reach saturation as the solidsolution layer thickens or its content increases. The observed decrease inthicknesses is accounted for by strengthening the strain deformation in the solidsolution layer. The received dependence of the 2D-3D transition will enable toobtain two-dimensional dislocation-free GexSi1-x layers, which are used at thegrowth of multilayer periodical Ge/Si structures ( Fig. 1). The surface morphologyof a germanium island film on the surface of GexSi1-x solid solution changesessentially if germanium islands is formed as “hut”-clusters before growing theGexSi1-x layer. The morphology of the GexSi1-x layer located above the hut-islandsdepends on the Ge content in the GexSi1-x layer. On the GexSi1-x surface withconcentrations x>0.25 is observed the relief of underlying islands. Furtherdeposition of the Ge film on the solid solution layer leads to a series of structuraltransitions on the surface. Based on the RHEED data the hut-like island formwhich hasn’t been previously observed by us between the hut and dome islandshas detected. This form of islands appear on the phase diagram in the rangefrom x=0.25 to x=0.5 (Fig. 2). The presence of a thin strained layer of the GeSisolid solution not only causes changes in the critical thicknesses of thetransitions but also affects properties of the germanium nanocluster array. Thework is supported by the Russian Foundation for Basic Research (Grants12-02-00427). References[1] G. Masini, L. Colace, G. Assanto, Encyclopedia of Nanoscience and Nanotechnology, 3, 829 (2004). [2] A.I.Yakimov, et al., Semicond. Sci. Technol. 26, 085018 (2011). [3] N. V. Vostokov et.al. Physics of the Solid State, 47,No. 1, 26 (2005). [4] Zhensheng Tao et.al. Applied Surface Science, 255 3548 (2009).

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Fig.1:Critical thicknesses of 2D-3D transition vs Ge content in GexSi1-x solid solution.

Fig.2.:The phase diagram of the growth for Ge/GexSi1-x/Ge heterostructure.

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TuP1-8 | In-situ grown hexagonal silicon nanocrystals insilicon-carbide-based films (#373)Tae-Youb Kim 1, Chul Huh1, Rae-Man Park1, Hojun Ryu1, Cheol-Jong Choi2, MakiSuemitsu3

1Electronics and Telecommunications Research Institute ConvergenceComponents & Materials Research Laboratory, 218 Gajeong-ro Yuseong-gu,Daejeon 305-700, Korea Republic (South)2Chonbuk National University Chonbuk National University, Jeonju 561-756,Korea Republic (South)3Tohoku University Research Institute of Electrical Communication, Sendai980-8577, Japan ContentSilicon-related low-dimensional structures such as Si nanocrystals (Si-NCs) haveshown great potential in the development of next-generation devices. When Si-NCs are made smaller than the free-exciton Bohr radius of bulk Si, they behaveas quantum dots1-3 with various energy states that can be tuned using carrierconfinement in all three dimensions. These quantum properties of Si-NCs havethe greatest impact when they are embedded in a wide-gap dielectric matrix, thestructure of which is quite intriguing in the field of Si optoelectronics and third-generation photovoltaics.4-5 Among such wide-gap dielectric matrixes foroptoelectronic and photovoltaic devices are Si-carbide-based films. These filmsare considered to have one of the most promising top (window) layers due to ahigh transparency to photons absorbed by an underneath layer of Si-basedjunctions, as well as to the conductive nature of the material. Moreover, when Si-carbide-based film includes Si-NCs, the combination will certainly have furtheradvantages. One such advantage is a lower barrier height caused by a lowerband-gap of Si carbide (~2.5 eV) compared to Si oxide (~9 eV) and Si nitride(~5.3 eV), which brings about an increased tunneling probability between Si-NCs.5-7 Other advantages include the easy formation of minibands between Si-NCs and a higher Bloch carrier mobility.3,8 In this study, we demonstrate the in-situformation of hexagonal Si-NCs during the preparation of a silicon-carbide-basedmatrix film at 250 °C. The optical gaps of the Si-NCs have been characterizedusing photoluminescence (PL). Finally, we discuss the size effect of hexagonalSi-NC on its quantum confinement of carriers.9-12

References[1] L. Pavesi, D. J. Lockwood: Silicon Photonics: Silicon fundamentals for photonic applications, Heidelberg, Berlin(2004). [2] P. J. Walters, G. I. Bourianoff, and H. A. Atwater, Nature Materials 4, 143 (2005). [3] C.-W. Jiang and M.A. Green, J. Appl. Phys. 99, 114902 (2006). [4] N.-M. Park, T.-S. Kim, and S.-J. Park, Appl. Phys. Lett. 78, 2575(2001). [5] E.-C. Cho, S. Park, X. Hao, D. Song, G. Conibeer, S.-C. Park and M. A. Green, Nanotechnology 19,245201 (2008). [6] Q. Cheng, S. Xu, J. Long and K. Ostrikov, Appl. Phys. Lett. 90, 173112 (2007). [7] Y. Kurokawa,S. Tomita, S. Miyajima, A. Yamada, and M. Konagai, Jpn. J. Appl. Phys. 46, L833 (2007). [8] D. Song, E.-C. Cho, G.Conibeer, C. Flynn, Y. Huang, and M. A. Green, Sol. Energy Mater. Sol. Cells 92, 474 (2008). [9] Y. Q. Wang, Y. G.Wang, L. Cao and Z. X. Cao, Appl. Phys. Lett. 83, 3474 (2003). [10] T.-Y. Kim, N.-M. Park, K.-H. Kim, G. Y. Sung, Y.-W. Ok, T.-Y. Seong, and C.-J. Choi, Appl. Phys. Lett. 85, 5355 (2004). [11] T.-Y. Kim, N.-M. Park, C.-J. Choi, A. Kim,I.-K. You, and M. Suemitsu, J. Korean Phys. Soc. 59, 308 (2011). [12] T.-Y. Kim, N.-M. Park, C.-J. Choi, C. Huh, C.-G. Ahn, G. Y. Sung, I.-K. You, and M. Suemitsu, Jpn. J. Appl. Phys. 50, 04DG11 (2011).

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Figure 1.:Cross-sectional high-resolution transmission electron microscopic (HRTEM) images of the Si-QDs grownby SiH4+CH4 gas

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TuP1-9 | From growth to device fabrication (#393)Dhirendra Kumar, Poonam Sharma, Vijeta Kumar Magadh University Department of Physics, 44/23, Bihar, Gaya 803452, India ContentA trace sensor of atmospheric pollutants must meet a set of fundamentalrequisites. High selectivity is necessary to distinguish the gas species present ina multi-component gas mixture, such as air, as long as a high sensitivity isessential for the detection of very low concentrations of the substances. A largedynamic range is important for monitoring the gas components at high and lowconcentrations with the same instrument. In addition, a good time resolutionensures the possibility of online analyses controlled by the computer. Themethodologies based on photo-acoustic spectroscopy, mainly URAS, havesuitable characteristics for the detection of gases. However, the application of thechemical type gas sensor is limited by Several disadvantages, such as thepotential difficulties in detecting gases with low adsorption energies, the highworking temperature (except for the CNTs based sensors), and the higher powerconsumption.

Response:Response characteristics

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TuP1-10 | Influence of the pit sidewall inclination on the SiGequantum dot nucleation site (#407)Martyna Grydlik , Moritz Brehm, Thomas Fromherz, Friedrich SchäfflerJohannes Kepler University Linz Institute of Semiconductor and Solid StatePhysics, Altenbergerstrasse 69, 4040 Linz, Austria ContentWe show for the prototypical Ge/Si(001) system that enhanced degree ofordering is possible via substrate pre-patterning and pit-angle variation.Experiments supported by elasticity simulations show that the pit-inclinationangle critically affects island positioning [1]. We demonstrated the possibility ofgrowing SiGe islands on pit patterned Si(001) substrates with pits having a

continuous variation of the sidewall inclination angle α from α 5° to α 54°. Atthe critical angle α 32°, the position of the islands flips from inside to outside

the pit, as shown in Figs. 1 c) and d). For pre-defined pits with small sidewallinclination angles (i.e. < 30°) islands nucleate solely within the pits – if the growthconditions are chosen adequately. For larger pit-sidewall inclination angle (i.e. >30°) islands grow at the rim of the pits on the slightly relaxed convex Ge wettinglayer. The growth follows an evolution from unfaceted pre-pyramids via pyramidsto domes [2]. The usual symmetry of the islands is, however broken by thepresence of the pit and for the 105-faceted pyramids additional 116 facets arefound. For the pit sidewall inclination reaching 54.7°, i.e. for pits with 111sidewalls, it is possible to obtain ring-like, densely packed arrays of islandsnucleating directly at the rim of the pit. For a Ge deposition of 3 ML such rings ofislands can be formed with a spacing of up to 4.5 µm. No randomly nucleatedislands are formed in-between of the decorated pits. References[1] G. Vastola, M. Grydlik, M. Brehm, T. Fromherz, G. Bauer, F. Boioli, L. Miglio, and F. Montalenti Phys. Rev B 84,155415 (2011). [2] F. M. Ross, R. M. Tromp, M. C. Reuter Science 286, 1931 (1999).

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Evolution of dots growth:Evolution of island nucleation mediated by the pit sidewall inclination, with increasing pit angle (α). (a)(f)3D AFM images (grey image) and surface inclination maps (colorful map) of the pits with inclination anglesranging from (a) α = 5.4°

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TuP1-11 | Conditions for perfect ordering of Ge/Si(001)quantum dots: Influence of pit-shape and size and buffer layeron the ordered island growth (#431)Moritz Brehm , Martyna Grydlik, Friedrich SchäfflerJohannes Kepler University Linz Institute of Semiconductor and Solid StatePhysics, Altenbergerstrasse 69, 4040 Linz, Austria ContentFor the integration of Ge quantum dots into devices based on standard Sitechnologies, addressability, and thus perfect ordering, is mandatory. Moreover,ordered dots show increased size uniformity for a large window of growthparameters, and equally important, their chemical composition is morehomogeneous as compared to randomly nucleated islands. Potential applicationsfor ordered dots strongly depend on their relative lateral spacing. Ordered dotsgrown on patterned substrates with wide pit-periods of, say, one micrometer canbe used e.g. for single photon emitters, while for periods smaller than 100 nmindividual quantum dots start to interact. In our approach, we use pit-patterned Sisubstrates and subsequently solid source molecular beam epitaxy of Si and Geto achieve strictly ordered dots. To obtain both, perfect dot ordering and also thebest structural and optical properties, many aspects of substrate patterning haveto be taken into account. A summary of the ten most important issues isschematically depicted in Fig. 1. In this work we will track down the detailedinfluence of pit parameters, such as pit-depth, pit-diameter, pit-shape, pit-period,as well as Si buffer layer growth and the deposition volume of Ge on thedesigned quantum dot size and composition. In this way we can e.g. determineways to avoid double and multiply occupation of pits by dots as well as decreasethe number of vacancies (missing dots). We find that, if the pits are initially ofcylindrical (see Fig. 2(a), see also Ref. [1]) or of pyramidal shape [2], pitsmoothening due to the initial Si buffer layer growth (see Fig. 2(b)) and the firsttwo monolayers of Ge (see Fig. 2(c)) is crucial to build an appropriateenvironment for the subsequent quantum dot nucleation and growth (Figs. 2(d)-(f)). We identify an optimum window of pit–sidewall inclinations, i.e. between 5°and 30°, for which dots nucleate in the middle of the pits, given that the pitdiameter is not more than about twice the size of the dot diameter. For largesidewall-inclination angles, the favourable island nucleation sites are found to beat the rim of the pit. Surprisingly, for very shallow pits (inclination smaller than 5°)the pits seem not to be preferential nucleation sites for dots. The pits remainempty and are eventually planarized with increasing Ge deposition. The findingspresented in this work provide a concise base for the fabrication of orderedquantum dots based on substrate pre-patterning. References[1] J. J. Zhang, M. Stoffel, A. Rastelli, et al., Appl. Phys. Lett. 91, 173115 (2007) [2] M. Grydlik, M. Brehm, F. Hackl,et al., New J. Phys. 12, 063002 (2010)

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Parameter space:For the growth of ordered dots on pit-patterned substrates we identified the 10 most important growthparameters. This work deals with the ones marked in red color.

Pit evolution:3D-AFM micrographs of (a) a cylindrical pit etched into the Si substrate and the pit after (b) Si buffer layergrowth and (c)-(f) after increasing amount of deposited Ge. The evolution from small pyramids (d) tobigger domes (h) can be traced.

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TuP1-12 | Flash Lamp Processing of InAs nanostructures onsilicon and SOI wafers (#433)Slawomir Prucnal , S.q. Zhou, Stefan Facsko, A. Muecklich, X. Ou, M.o. Liedke,B. Liedke, Manfred Helm, W. SkorupaHZDR FWI, Bautzner Landstrasse 400, 0314 Dresden, Germany ContentOne of the solutions enabling performance progress, which can overcome thedownsizing limit in silicon technology, is the integration of different functionaloptoelectronic devices within a single chip. Silicon with its indirect band gap haspoor optical properties, which is its main drawback. Therefore, a differentmaterial has to be used for the on-chip optical interconnections, e.g. a directband gap III-V compound semiconductor material. Recently we demonstrated acompact, CMOS compatible and fully integrated solution for the integration of III-V semiconductor nanocrystals with silicon technology for optoelectronicapplications. They are synthesized in silicon using combined ion beamimplantation and millisecond flash lamp annealing (FLA) techniques [NanoLett.11, 2814 (2011)]. FLA appears to be the most suitable technique for thispurpose. The energy budget introduced to the sample during FLA is sufficient torecrystallize silicon amorphized during the ion implantation and to form InAsnanocrystals (NCs) via the liquid phase. In this talk we will present results of themicrostructural and electrical properties of InAs quantum dots formed in silicon orSOI wafers. An evolution of the InAs nanocrystals growth during FLA and theinfluence of the annealing parameters on the crystallographic orientation, shapeand size will be explored. Moreover, the self-organization of the InAs nano-objects on the SOI wafers after flashing will be presented. A unique nano-swelling effect appearing during ion implantation of the SOI wafers combinedwith milliseconds range liquid phase epitaxy for the self-organization isresponsible. Conventional selective etching was used to form the n-III-V/p-Siheterojunction. Current-voltage measurements confirm the heterojunction diodeformation between n-type InAs quantum dots and p-type Si substrate. The mainadvantage of our method is its integration with large-scale silicon technology,which also allows applying it for Si-based photronic devices.

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TuP1-13 | OPTO – STRUCTURAL STUDIES OF WELLDISPERSED SILICON NANOCRYSTALS GROWN BY ATOMBEAM SPUTTERING (#438)Nupur Saxena , D. Kabiraj, D. KanjilalInter University Accelerator Centre Material Science, Aruna Asaf Ali Marg,, NewDelhi, New Delhi 110067, India ContentSynthesis and characterization of nanocrystalline silicon grown by atom beamsputtering (ABS) technique is reported. ABS is a unique technique to grownanosized silicon in silicon oxide matrix. The sputtering target consists of siliconglued on 60 % area of a fused silica disc. The substrates used are silicon (100)wafer, fused silica and TEM grids for different studies. Rapid thermal annealingof the deposited films is carried out in Ar + 5% H2 atmosphere for 5 min atdifferent temperatures for precipitation of silicon nanocrystals. The samples werecharacterized for their optical and structural properties using various techniques.Structural studies were carried out by micro-Raman spectroscopy, FTIR, TEM,HRTEM and selected area eletron diffraction. The optical properties were studiedby UV-Vis absorption spectroscopy and band gap was evaluated. The microRaman studies show the formation of nanocrystalline silicon in as deposited aswell as annealed film. The shifting and broadening in the peak suggestsformation of nanophase in the samples. The band gap is found to increase afterrapid thermal treatment. A detailed analysis by micro Raman and HRTEMstudies suggest the presence of a bimodel crystallite size distribution. Thestudies show that atom beam sputtering is a suitable technique to synthesizesilicon nanocrystals. The size of the nanocrystals can be controlled by varyingannealing parameters.

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ABS-Si NCs:TEM studies, SAED pattern and size distribution (Inset).

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TuP1-14 | Influence of In segregation and intermixing on theoptical and electronic properties of InAs/GaAs quantum dotsand photodetectors (#446)Alvaro Maia , Fernando Fernandes, Marcel Claro, Euzi da Silva, Alain QuivyUniversidade de São Paulo Instituto de Física, Rua do Matão Travessa RNr.187, São Paulo, São Paulo, 05508-090, Brazil ContentQuantum-dot infrared photodetectors (QDIPs) recently emerged as a newtechnology for detecting infrared radiation. Compared to more conventionalphotodetectors based on quantum wells (QWIPs), their advantages originatefrom the three-dimensional confinement of carriers and include an intrinsicsensitivity to normal incidence of light, a longer lifetime of the photoexcitedcarriers and a lower dark current which should hopefully allow their operationclose to room temperature. In the present work, molecular-beam epitaxy (MBE)was used to grow several InAs/GaAs QDIP structures where the Si doping of thequantum dots (QDs) themselves was optimized in order to provide two electronsin the lowest energy level of all the self-assembled InAs QDs. To get the bestrelationship between the physical dimensions of the QDs and the operatingcharacteristics of the QDIPs, we developed a position-dependent effective-masscalculation of the bound energy levels and wave function of the electronsconfined in lens-shape InxGa(1-x)As quantum dots embedded in GaAs, taking intoaccount the strain as well as the In gradient inside the QDs which is due to thestrong In segregation and intermixing present in the InxGa(1-x)As/GaAs system.After the growth, the samples were processed into small squared mesas byconventional lithography techniques and fully characterized. The optical andelectrical properties of the devices were checked as a function of temperature ina closed-cycle He cryostat with a cold finger, Ge optical windows and all theconnectors and low-temperature/low-noise cables needed to perform high qualitylow-level electrical measurements. Dark-current curves, Responsivity(photocurrent) data with a black body, noise measurements with a signalanalyzer and spectral responses by FTIR provided a full set of information aboutthe devices. The figures of merit of our best device, operating around 3,3 µm,allowed us also to determine the capture probability and the photoconductivegain. Different In profiles inside the QDs were tested with our new theoreticalmodel and the one that provided the best fit to our experimental data was thelinear gradient that assumes 0% of In at the base of the QDs and 100% of In attheir top.

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Quantum dot wave function:Electronic wave function of the fundamental state of an InAs/GaAs QD with a linear In gradient, showing ashift towards the top of the QD.

Spectral response:Spectral response of an InAs/GaAs QDIP at 77K after optimization of the QD doping.

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TuP1-15 | Nanotwinning and structural phase transition in CdSquantum dots (#454)Pragati Kumar 1, Ramesh Chandra2, F. Singh3, Avinash Agarwal11Bareilly College, Bareilly Department of Physics, UP, Bareilly 243003, India 2Indian Institute of Technology Institute Instrumentation Centre, UK, Roorkee 247667, India 3Inter University Accelerator Centre Material Science, Aruna Asaf Ali Marg,, NewDelhi, 110067 New Delhi, India ContentNanotwin structures are observed in high resolution transmission electronmicroscopy studies of CdS quantum dots formed in cubic phase by chemical co-precipitation method. The twinning structures are present together with stackingfaults in some QDs while others exist with grain boundaries. A noticeable shift isobserved in Raman spectra that indicates the effect of phonon confinement. Thephotoluminescence spectrum shows intense yellow and red emission. Thepresence of stacking faults and other defects are correlated with x-rays diffractionand photoluminescence studies. Thin films of CdS quantum dots are depositedby laser ablation of a target prepared by pressing the chemically synthesizedCdS powder. The effect of thermal annealing on the optical and structuralproperties of these films is studied. Thin films of nanocrystalline CdS aredeposited on Si, glass and TEM grids keeping the substrates at roomtemperature (RT) and 200 °C. These films are then subjected to thermalannealing at different temperatures and further characterized for their optical andstructural properties. The structural studies are carried out using FTIR, GAXRD,micro Raman and TEM. The GAXRD results confirm the presence of a mixture ofhexagonal and cubic phases in the as grown films. The films deposited at 200 °Cshow a phase transformation into complete hexagonal at 400°C first and then incubic phase at 450°C after thermal annealing. There is a transition from mixedphase to pure cubic in the films deposited at room temperature. Ramanspectroscopy analysis shows intense and broad peaks corresponding tofundamental optical phonon mode (LO), the first over tone mode (2LO) and thesecond overtone (3LO) of CdS at around 302 cm-1 and 603 cm-1 and 903 cm-1

respectively. The fundamental peak and first overtone peak is shifted towardslower wave number after annealing where as no such shifting is observed forsecond overtone. The optical characterizations include UV-Vis absorptionspectroscopy and photoluminescence spectroscopy.

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TuP1-16 | Effects of shutter transients in moleculor beamepitaxy (#495)Shin-Ichiro Gozu , Teruo Mozume, Haruhiko Kuwatsuka, Hiroshi IshikawaNational Institute of Advanced Industrial Science and Technology (AIST)Network Photonics Research Center, AIST Tsukuba Central2, 1-1-1 Umezono,Ibaraki, Tsukuba 305-8568, Japan ContentMolecular beam epitaxy (MBE) is an ideal method to grow nano-structures.However, MBE cannot avoid the effects of shutter transients (STs), whereininaccuracies are caused by flux transients after shutter opening owing totemperature gradients in the cells. Two contrasting studies of STs have beenreported: (i) growth rate (GR) decreased and saturated after a characteristic timeconstant (CTC)[1,2]; (ii) GR was below that desired and then approached thetarget GR within a CTC[3]. Hence, the effects of STs appear controversial ormachine-dependent. We have thus studied the effects of STs in our MBE system(VG-V80H). Two series of samples were grown (Fig. 1). One comprised stacks oftwo superlattices (SLs) used to evaluate growth time (GT) dependence of GR.The other comprised coupled double quantum wells (CDQWs) ofInGaAs/AlAs/InP for evaluating GT dependence of layer thicknesses (LTs). Onlyone In cell was used for SL samples, while two In cells, labeled In(1) and In(2),were used individually for 50 nm bottom InP buffers. The period of the SLs wasevaluated by X-ray diffraction (XRD) measurements. The LTs of the CDQWswere evaluated by X-ray reflectivity (XRR) measurements. Fig. 2(a) shows GTdependence of GR for InGaAs, found to be consistent with study (ii). Fig. 2(b)shows the XRR spectra of the CDQWs. Owing to identical intended structures ofthe two CDQWs, identical XRR spectra were expected. However, the measuredspectra revealed a slight difference in period, indicating structural differences.XRR spectrum simulations were performed to evaluate these structures (Fig. 2(c-e)). Because the topmost layer was difficult to evaluate in XRR measurements[4].The differences were found to be mainly due to the InGaAs LTs; the LTs ofbottom layers were thicker than that of the upper ones. This behavior wasconsistent with study (i), but inconsistent with the observed GT dependence ofGR. Therefore, ST effects could categorize two types of behaviors. Becauseexperiments on the SLs revealed an average GR for the entire structure whileXRR measurements revealed an initial growth state, the two opposite behaviorscould be understood as follows: at long shutter closing times, the temperatureinside the cells (Tcell) was slightly higher than that desired, whereas at shortclosing times, Tcell was influenced by the temperature gradient due to shuttermovements. This hypothesis is reasonable because the difference in LTs wasmore suppressed for In(1) than for In(2) References[1] Ch. Heyn and S. Cunis, J. Vac. Sci. Technol. B, vol. 25 (2005) 2014. [2] P. Cristea et al, J. Appl. Phys, vol. 100(2006) 116104. [3] T. Toch et al., Central European Journal of Physics, vol. 5 (2007) 244. [4] P. Colombi et al., Appl.Cryatallography, vol. 41 (2008) 143.

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Figuer 2:Results of X-ray diffraction and X-ray reflectivity (XRR) measurements.

Figure 1:Schematic structure of the samples used in this study.

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TuP1-17 | Electrically Conductive Nanocomposite HollowFibers(#560)Shi Hyeong Kim , Seon Jeong KimHanyang University Biomedical Engineering, 17 Haengdang-dong Seongdong-gu, Seoul 133-791, Korea Republic (South) Content Conducting polymers have been researched for applications in actuators,sensors, and energy storage devices because they have important properties,such as facile interconversion between redox states, high electrical conductivity,and good chemical stability [1]. Conducting polymers with tubular structure areeffective in enhancing the charge/discharge rate and capacity [2, 3]. We havefabricated electrically conducting composite hollow fibers (HFs) using coaxialelectrospinning and chemical polymerization. Randomly oriented and wellaligned polyamic acid (PAA) HFs were successfully fabricated as templates withhigh surface area to volume ratio employing coaxial electrospinning. PAA HFswere converted to polyimide (PI) HFs through thermal treatment. Inner and outersurfaces of well aligned PI HF bundles were uniformly thin coated with apolyaniline conducting polymer by in situ chemical polymerization. Outer andinner thicknesses of coated polyaniline layers were ~ 100 nm and ~10 nm,respectively. These composite HF bundles had an electrical conductivity of 11.5S/m. The average values of outer and inner diameters of the conducting HFswere ~1005 and ~815 nm, respectively. The conducting HF bundles areapplicable as supercapacitors and actuators ReferencesReference 1. G. A. Snook, P. Kao and A. S. Best: Conducting-polymer-based supercapacitor devices and electrodes.Journal of Power Sources 2011, 196: 1. 2. S. Cho and S. B. Lee: Fast Electrochemistry of Conductive PolymerNanotubes: Synthesis, Mechanism, and Application. ACCOUNTS OF CHEMICAL RESEARCH 2008, 41: 699 3. P.Simon and Y. Gogotsi: Materials for electrochemical capacitors. nature materials 2008, 7: 845

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TuP1-18 | EPITAXY on the metallic substrates (#562)Gintarė Statkutė Vilnius University Physics, Saulėtekio al.6, 10222 Vilnius, Lithuania ContentIt is represented results from 2008 growths in Micronova, Helsinki University ofTechnology, Aalto University at present, of GaAs nanowires, nanocrystallites (=nanostructures (ns)) and bulk layers by means of MOCVD from TBA TMG on Au,Au/Pd, Al, Ti, Cu, Ga, Pt, Ni, Ag [1,2] evaporated on SiO2 and Sapphire.Samples were characterized by SEM, TEM. My achievement is in recognizingand showing epitaxy on the metals and in the single step semiconductor(sc)-metal(me) junction / contact (smj/c) manufacturing and in the novelty of thejunction/contact (j/c) which have the same diameter as ns and is of epitaxialquality. During ns contacting with conventional methods metalisation is carriedtwice: for ns growth catalysis and later for contact deposition. The second step islong lasting, additionally expensive contact patterning by lithography or FIB isinvolved. Bulky compared to the diameter of the ns, hanging-covering contactsare achieved due lithography processes errors. FIB preparation disadvantages:expenses, damage of contact by high energy beam (amorphous contact insteadof crystalline) or ns implantation with me atoms (several dopants in the core candramatically tune electrical properties of ns). As a thumb of rule, heating isapplied to improve electrical contacts to ns prepared by lithography or FIB. It isargued that heating cause contact me diffusion to the sc. Contacts after heatingstill remain hanging and bulky. During my ns growth chemical semiconductorprecursors diffuse to the catalyst me. Later, due concentration gradientenergetically favorable ns growth from me particle starts, i.e. starts sc depositionfrom catalyst. Ns are growing with perfectly smooth heteroepitaxial junctions. Infigure Dotted white arrow points to ns. Dashed black arrows point to common transverseelectrical contacts defined by lithography. Solid white concave arrows point to imsj/c atthe substrate end of ns formed by my approach during ns growth. Usually at thesubstrate end there is a uniform junction with sc, not with the me. J/s size can betuned by changing initial catalyst me layer. Solid white Λ shape arrows point to integerme junction on the ns top, which is common result in most catalysed ns growths.#1: SEM image of common contacts prepared by EBL. They are much largerthan ns and contact area is huge. #2-4: New metallic contact which is integer atatomic level with sc ns. #1,2,3 – SEM. #4-TEM. References[1] G.Statkute, A.Nasibulin, A.Aierken, M.Mattila, H.Lipsanen, The epitaxial growth on metals. 3rd Internationalworkshop on nanowire growth mechanisms / Sept.15-16, 2008, Duisburg(GE), Abst.Post [2] G.Statkutė,A.G.Nasibulin, P.Kostamo, A.Aierken, H.Lipsanen, M.Sopanen, T.Hakkarainen, E.Kauppinen, Growth of GaAsnanowires on metals, arXiv:0811.4248, 2009

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Metal- semiconductor j/c:.

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TuP1-19 | Impact of Ga induced superstructural phases on GaNgrowth on Si(111) surface (#142)Praveen Kumar 1, S. M. Shivaprasad2

1Institute for Systems based on Optoelectronics and Microtechnology TechnicalUniversity of Madrid, 28040 Madrid, Spain2CPMU Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore560064, India ContentThe lack of suitable substrate for GaN growth prevail different approaches suchas use of buffer layer, surfactant, ELOG growth etc, to improve the quality ofGaN films. Out of them surface modification [1-4] have been attracted a greatattention of the researchers because of its process compatibility to the existinggrowth process. We present here the impact of surface modification by usingsub-monolayer of metal (Ga) adsorption on GaN growth on clean Si(111)-7x7reconstructed surface. The three Ga induced superstructural phases namely1x1, √3x√3, and 6.3x6.3 have been used as a template to grow GaN at asubstrate temperature of 400oC by keeping all growth conditions constant andprobed in-situ and ex-situ by RHEED, XPS, AFM and LT-PL. All results show thatGaN films grown on √3x√3, have high quality and low surface roughness. Wecorrelate these results with the lattice matching epitaxy, where √3 superstructuralphase has nearly double lattice of GaN and every alternate unit cell of GaNmatches with √3 structure and gives batter epitaxy with the LME relation of 2/1,while 6.3x6.3 and 1x1 have 15/2 and 6/5 respectively. Overall these resultsprovide a clear impact of metal induced superstructural phases on GaN growthand demonstrate a plausible approach of adsorbate induced surfacemodifications as templates for III-V hetroepitaxy on Si surfaces. References1. Praveen Kumar, Jithesh K and S. M. Shivaprasad, Appl. Phys. Lett., 97 (2010) 221913. 2. Praveen Kumar, M.Kumar and S. M. Shivaprasad, Appl. Phys. Lett., 97, (2010) 122105. 3. Praveen Kumar, M. Kumar, B. R. Mehta, ApplSurf. Sci., 256 (2009) 480. 4. Praveen Kumar, M. Kumar and S. M. Shivaprasad, Solid State Communication, 151(2011) 1758.

Figure:AFM images, show the morphology of grown GaN films grown on (a) Clean Si(111)-7x7, (b) 6.3x6.3 and(c) root3xroot3 surface. Inset shows the corresponding RHEED image.

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TuP1-20 | Accurate control of highly stacked InAs quantumdash cavity with GaAsSb/AlAsSb-distributed Bragg reflectorgrown on InP(001) substrate by wet chemical etching (#198)Kouichi Akahane , Naokatsu YamamotoNational Institute of Information and Communications Technology PhotonicNetwork Research Institute, 4-2-1, Nukui-Kitamachi, Tokyo, Koganei 1848795,Japan ContentResearch on quantum dots (QDs) and quantum dashes (QDHs) has attractedsignificant attention because of their applications in high-performance opticaldevices. A QDH structure can control the polarization of light because of itsanisotropic shape, enabling the development of planar-type optical devices thatcan control light-wave polarization. QDHs should have a high density since thereis usually a short interaction length for devices such as the semiconductorsaturable absorber mirror (SESAM) or the vertical cavity surface-emitting laser(VCSEL). A growth procedure for increasing the number of stacked InAs QDHsvia the strain compensation technique and for a high-performance distributedBragg reflection (DBR) mirror has been developed on an InP(001) substrate[1,2]. In this study, we investigate the accurate control of a highly stacked InAsQDH cavity by wet chemical etching; such a control will help realize thefabrication of cost-effective high-performance planar-type optical devices. Allsamples in our work were fabricated using molecular beam epitaxy. After thermalcleaning in a growth chamber, we grew a DBR structure consisting of 25.5 pairsof λ/4-thick (λ = 1550 nm) GaAsSb/AlAsSb multi-layers on InP(001) substrates.Then, 5-ML InAs QDHs and a 20-nm-thick InGaAlAs spacer layer were grownconsecutively in stacks of up to 60 cycles for the active cavity by using the straincompensation technique. The total thickness of the QDH cavity was close to 3λ(λ = 1550 nm). Accurate wet chemical etching was conducted using aH3PO4:H2O2:H2O solution. The etching rate was 24 nm/min. The opticalproperties of the highly stacked InAs QDH cavity were evaluated by reflectancemeasurement and photoluminescence (PL) measurement. Figure 1 shows thereflectance spectrum at 0-, 2.5-, 4.5-, and 6.5-min etching. The cavity modeswere well controlled by wet chemical etching. The most important observationwas that because the cavity had a highly stacked QDH that acted as the gain andabsorption media, a high efficiency of emission and absorption could beexpected. Figure 2 shows the results of the PL measurement. The solid line andthe dotted line show PL from QDH with and without a DBR structure. Etching wascarried out for 6.5 min for the QDH cavity structure (solid line). The narrowingand enhancement of PL were observed in the QDH cavity structure. Theseresults indicated that the highly stacked QDH cavity structure would help realizea high-performance VCSEL and SESAM. References[1] K. Akahane, et al. Physica E, 40, 1916 (2008) [2] K. Akahane, et al. physica status solidi (c), 9, 235 (2012)

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Figure 1:Reflectance spectrum of QDH cavity with 0-, 2.5-, 4.5-, and 6.5-min etching.

Figure 2:PL spectrum of QDH cavity with 6.5-min etching (solid line). The dotted line shows PL spectrum of QDHwithout DBR structure.

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TuP1-21 | A simple method to make electrical connectionbetween nanoscale electrodes and microwire using suspendedPMMA string (#351)Hakseong Kim , Sang Wook Lee, Hoyeol Yun, Jinkyung LeeDivision of Quantum Phases and Devices, School of Physics, Konkuk University,seoul 143701, Korea Republic (South) ContentWe developed a new method for making electrical connection on ZnO microwireswith a small amount of Ti/Au metal evaporation using PMMA strings. Less than90nm height of Ti/Au made a complete electrical connection on the ZnOmicrowires of which diameter around 1~2um. The contact resistances of ZnOmicro wire based electronic devices fabricated by this method shows lowervalues than those of devices fabricated by standard E-beam lithography andevaporation processes. This fabrication method is readily extendible to preparenano scale electrodes on various micro sized materials and serves as a pathwayfor studying their mesoscopic transport phenomena.

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TuP1-22 | Particle Size Effects on the Structural, Morphologicaland Optical Properties of SiO2-Al2O3 Sol-Gel NanocompositeThin Film Coatings (#397)Bengü Özuğur Uysal 1,2, Fatma Zehra Tepehan2

1Kadir Has University Department of Information Technology, Faculty of Arts andSciences, 34083 Istanbul, Turkey 2Istanbul Technical University Department of Physics Engineering, Faculty ofScience and Letters, 34469 Istanbul, Turkey ContentSiO2 nanoparticled Al2O3 thin films were produced by sol–gel spin coatingtechnique. To control the size of the SiO2 nanoparticles, the films were madeusing various NH3 solution/TEOS ratios. The experimental results on the effect ofthe NH3/TEOS ratios on the structural, morphological and optical properties ofSiO2/Al2O3 nanocomposite thin film structure were reported and discussed. X-raydiffraction (XRD), atomic force microscopy (AFM), NKD and ultraviolet–visible(UV–vis) spectroscopy, transmission electron microscopy (TEM), and TheFourier transform infrared (FT-IR) spectroscopy were used for thecharacterization of nanocomposite films. SiO2/Al2O3 thin films were widely studiedwith different groups for preparation of photosensitive films, increasing emissivityof thin-film solar cells, production of the storage layer of the flash memorydevices, ion chromatographic support, etc [1-9]. In this work, the silica sol wasmixed with alumina sol to prepare the SiO2/Al2O3 nanocomposite thin film andthey contain the different sized silica nanoparticles. The nanostructured SiO2 solswere made using a conventional mixture of tetraethoxysilane (TEOS), deionizedwater and ethanol, with various NH3/TEOS ratios. Al2O3 sol was prepared usingAluminium butoxide, distilled water and acetic acid. The SiO2 and Al2O3 sols weremixed at room temperature for 30 min. in volume ratio of 1:10. The sols werespin coated on the corning (2947) and quartz glasses substrates. The finalcoatings were heat treated at 450 C for 1 h. and at 1100 C for 48 h. by a furnace.The XRD studies showed that the composite film has an alfa-cristobalite andmullite crystal structure at annealing temperature at 1100 C. AFM and TEMimages of nanocomposite film are given in Figure 1 and 2. The transmittancedata of the films were carried out by a NKD spectrometer in the s and ppolarization modes in 300-1000nm wavelength. The cut-off wavelength could bedetermined from the extrapolation of the absorbance spectra of the UV–visspectroscopy. The FT-IR spectra of the films in the transmission mode wererecorded in a wave number range of 650–4000cm−1 on a Perkin-Elmer FT-IRSpectrometer. The NH3 /TEOS ratio in the solution of the film is proportional tothe size of the nanoparticles. This is in agreement with Stöber et.al.[10]. Thequantum confinement effect of silica nanoparticles was confirmed by the red shiftof the cut-off wavelength which is related to increase of the diameter of thenanoparticles.

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References[1] High surface passivation quality and thermal stability of ALD Al2O3 on wet chemical grown ultra-thin SiO2 onsilicon, Stefan Bordihn, Peter Engelhart, Verena Mertens, Gerd Kesser, Dennis Köhn, Gijs Dingemans, Magda M.Mandoc, Jörg W. Müller and W. M. M. Kessels, Energy Procedia 8 (2011) 654–659. [2] Preparation of photosensitivegel films and fine patterning of amorphous Al2O3–SiO2 thin films, Gaoyang Zhao and Noboru Tohge, MaterialsResearch Bulletin, 33-1 (1998) 21–30. [3] ArF-line high transmittance attenuated phase shift mask blanks usingamorphous Al2O3–ZrO2–SiO2 composite thin films for the 65-, 45- and 32-nm technology nodes, Fu-Der Lai, Jui-MingHua, C.Y. Huang, Fu-Hsiang Ko, L.A. Wang, C.H. Lin, C.M. Chang, S. Lee, Gia-Wei Chern,Thin Solid Films 496(2006) 247 – 252. [4] SiO2 and Al2O3/SiO2 coatings for increasing emissivity of Cu(In, Ga)Se2 thin-film solar cells forspace applications, Kazunori Shimazaki, Mitsuru Imaizumi, Koichi Kibe, Thin Solid Films 516 (2008) 2218–2224. [5]Charge trapping behavior of SiO2-Anodic Al2O3–SiO2 gate dielectrics for nonvolatile memory applications, Chun-HsienHuang, En-Jui Li, Wai-Jyh Chang, Na-Fu Wang, Chen-I Hung, Mau-Phon Houng, Solid-State Electronics 53 (2009)279–284. [6] High temperature oxidation resistance of FeCrAl alloys covered with ceramic SiO2–Al2O3 coatingsdeposited by sol–gel method, J.G. Che˛cmanowski, B. Szczygie, Corrosion Science 50 (2008) 3581–3589 [7] Ethanolsteam reforming reactions over Al2O3-SiO2-supported Ni–La catalysts, Lifeng Zhang, Wei Li, Jie Liu, Cuili Guo, YipingWang, Jinli Zhang, Fuel 88 (2009) 511–518. [8] Preparation and ion chromatographic properties of a new core-shellchromatographic support Al2O3/SiO2-10 Xiaojing Lianga, ShuaiWang, Jingang Niua, Xia Liu, Shengxiang JiangJournal of Chromatography A, 1216 (2009) 3054–3058. [9] Flame-made nanoparticles for nanocomposites, AdrianCamenzinda, Walter R. Caseri, Sotiris E. Pratsinis, Nano Today (2010) 5, 48—65. [10] W. Stöber, A. Fink, E. Bohn,Controlled growth of monodisperse silica spheres in the micron size range, J. Colloid Interface Sci. 26 (1968) 62-69.

Figure 1:AFM image of Al2O3-SiO2 nanocomposite film

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Figure 2:TEM image of Al2O3-SiO2 nanocomposite film

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TuP1-24 | Synthesis and Characterization of MWCNT-SiO2 Sol-Gel Hybrid Thin Films (#479)Bengü Özuğur Uysal 1,2, Fatma Zehra Tepehan2

1Kadir Has University Department of Information Technology, Faculty of Arts andSciences, 34083 Istanbul, Turkey 2Istanbul Technical University Department of Physics Engineering, Faculty ofScience and Letters, 34469 Istanbul, Turkey ContentMultiwalled Carbon Nanotubes (MWCNT)-reinforced SiO2 nanoparticled thin filmswere produced by sol–gel spin coating technique. The effects of temperature onthe particle size were investigated. The optical properties and surfacemorphology of the hybrid films were characterized by using atomic forcemicroscopy (AFM), NKD and ultraviolet–visible (UV–vis) spectroscopy, scanningelectron microscopy (SEM). MWCNTs are very important in various applicationsof nano-science and technology, and silica thin films was used as thermallystable dielectric material due to their high band gap energy values. MWCNT wereused as reinforcements to strengthen the mechanical properties of silica thinfilms. MWCNT-SiO2 hybrid thin films could be prepared by the sol–gel processthat offers a low-cost, rapid and uniform coating on glass surfaces. MWCNTsproduce a stable composite without changing the nanostructure of silica thin films[1-6]. In the present paper, the nanostructured SiO2 sol was made using amixture of tetraethoxysilane (TEOS), deionized water, ethanol, ammonia, andwas mixed with MWCNT (diameter:30-50 nm, length: 10-20 micrometer). Thesols were spin coated on the corning (2947) glass substrates, and then they wereheat treated at 450, 550, 650 and 900 C for 1 h. by a microprocessor-controlledfurnace. AFM image of hybrid film is given in Figure 1. The transmittance data ofthe films were measured by a NKD spectrometer in the s and p polarizationmodes in 300-1000 nm wavelength. The band gap energy of the hybrid film wascalculated from the absorbance spectra of the UV–vis spectroscopy. Theactivation energy of the hybrid film was evaluated from the particle growthkinetics. The change in the particle size was investigated according to the heattreatment temperature. A blue shift in the absorption threshold of the hybrid filmsindicated that the size of silica nanoparticles was decreased by a decrease at theannealing temperatures from 900 to 450 C. References[1] Effect of surfactants on MWCNT-reinforced sol–gel silica dielectric composites, Shane Loo, SridharIdapalapati,Shanzhong Wang, Lu Shen and Subodh G. Mhaisalkar, Scripta Materialia 57 (2007) 1157–1160. [2]Effects of UV degradation on surface hydrophobicity, crack, and thickness of MWCNT-based nanocompositecoatings, R. Asmatulu, G.A. Mahmud, C. Hille, H.E. Misak, Progress in Organic Coatings 72 (2011) 553– 561. [3]Fabrication of silica nanotubes using silica coated multi-walled carbon nanotubes as the template, Myunghun Kim,Jinho Hong, Jeongwoo Lee, Chang Kook Hong, Sang Eun Shim, Journal of Colloid and Interface Science 322 (2008)321–326. [4] Self-assembly of carbon nanotubes and alumina-coated silica nanoparticles on a glassy carbonelectrode for electroanalysis, Yu-Chen Tsai, Ming-Chieh Tsai, Chian-Cheng Chiu, Electrochemistry Communications10 (2008) 749–752. [5] Tough ceramic coatings: Carbon nanotube reinforced silica sol–gel A.J. López, A. Rico, J.Rodríguez, J. Rams, Applied Surface Science 256 (2010) 6375–6384. [6] Tribological interaction between multi-walled carbon nanotubes and silica surface using lateral force microscopy, Jung-Hui Hsu, Shuo-Hung Chang, Wear266 (2009) 952–959.

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Figure 1:AFM image of MWCNT-SiO2 hybrid film

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TuP1-25 | Thermal stability of III-nitride structures studied byin-situ XRD measurements (#537)Lars R. Khoshroo , Alexander Kharchenko, Woitok Joachim F.PANalytical B.V. Application Competence Center, Lelyweg 1, 7602 EA Almelo,Netherlands ContentA lot of research effort is currently spent on the development and improvement ofgallium nitride (GaN) based AlInN/AlN/GaN heterostructures[1]. Such layers aretypically grown epitaxially by MBE (Molecular Beam Epitaxy) or MOVPE (MetalOrganic Vapor Phase Epitaxy). Both techniques enable an accurate control ofthe materials chemistry and interface quality[2]. But since the structural quality of the layers and their interface is critical for device performance a detailedknowledge of the effects of successive process steps like thermal annealing onthese properties is crucial[3]. In the present work, we investigated the thermalstability of a nitride heterostructure by means of in-situ X-ray diffraction duringannealing. Reciprocal space maps (RSM) around asymmetric (20.4) and ω-2θscans around (00.2) were rapidly measured during annealing the sample underambient air at temperatures between 400°C and 700°C in an Anton Paar DHS1100 Domed Hot Stage. The stage was mounted on high-resolution X’Pert PROMRD X-ray diffractometer equipped with a PIXcel detector. At highertemperatures the intensity of the (00.2) reflection quickly dropped with theannealing time (Figure 1). A plot (Figure 2) of the temperature dependent slopesshows clearly an Arrhenius like behavior. Layer thickness, relaxation andcomposition were also checked by the in-situ measurements and provide furtherinsight into the ongoing processes. The time resolved data allowed to monitor theannealing behavior and its kinetics. This delivers valuable information for thedesign of further thermal processes of the wafer for instance ohmic contactannealing or dopant activation. References[1] Butté et al 2007 J. Phys. D: Appl. Phys. 40 6328 doi:10.1088/0022-3727/40/20/S16 [2] Gurusinghe et al Phys. Rev. B72, 045316 (2005). [3] Eickelkamp et al pss (c) Volume 8, Issue 7-8, pages 2213–2215, July 2011.

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Figure 1:Decrease of the (00.2) AlInN peak intensity versus annealing time at different temperatures showing theincrease of slope.

Figure 2:Arrhenius plot of the slope versus reciprocal temperature enables the determination of the activationenergy for the intensity evolution.

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TuP1-26 | Sol Electrophoretic Growth of TiO2 nanotubes (#546)Abolghasem Nourmohammadi University of Isfahan Department of Physics, Faculty of Science, Hezar-JeribAvenue, 81746-73441 Isfahan, Iran ContentIn the current research, sol electrophoresis technique was utilized to growtitanium dioxide (TiO2) nanotubes. Titanium sol was prepared using anorganometallic precursor of titanium to fill the template channels. The preparedsol was driven into nanopores of porous anodic aluminum oxide templates underthe influence of a DC electric field to form nanotubes on the pore walls. Tubeformation was occured after chemical etching of the template pores withphosphoric acid. After the firing step, the phase structure of the producednanotubes was evaluated based on the X-ray diffraction (XRD) investigations.Scanning electron microscopy and energy dispersive X-ray (SEM and EDX)studies showed that close-packed TiO2 nanotubes have been electrophoreticallygrown in the aluminum oxide template channels. Introduction: Synthesis ofone-dimensional TiO2 nanostructures such as TiO2 nanotubes, nanorods andnanowires has been considered because of their supreme capabilities inphotoelectrochemical reactions due to the enhanced surface charge transfer [1].The advantage of producing TiO2 nanotubes to TiO2 nanorods or nanowires ishigher surface area of nanotubes. Experimental: Porous aluminum oxidetemplates were prepared for the growth of TiO2 nanotubes through two-stepanodizing of aluminum foils. Titanium precursor was mixed with glacial aceticacid to chemically modify the sol hydrolysis-condensation reactions. DCelectrophoresis was used to fill the template channels with the prepared titaniumsol. Results and Discussion: Fig. 1 shows the SEM planar view of an array ofTiO2 nanotubes which have been deposited in the channels of a nanoporousanodic aluminum oxide template using DC sol electrophoresis technique. It isclearly obvious that sol electrophoresis of the prepared sol has resulted in ahollow tubular structure. References[1] A. I. Hochbaum and P. Yang, Chem. Rev. 2010, 110, 527–546.

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TiO2 nanotubes:Fig.1.SEM micrograph of an array of TiO2 nanotubes grown by DC sol electrophoresis technique.

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TuP2-1 | Single-photon emission from single InGaAs/GaAsquantum dots grown by droplet epitaxy at high substratetemperature (#324)M. Benyoucef 1, V. Zuerbig1, J. P. Reithmaier1, A. W. Schell2, T. Aichele2, O.Benson2

1Institute of Nanostructure Technologies and Analytics Technological Physics,University of Kassel, Heinrich-Plett-Strasse 40, 34132 Kassel, Germany 2Nano-Optik Humboldt-Universität zu Berlin, Newtonstrasse 15, 12489 Berlin,Germany ContentSelf-assembled semiconductor quantum dots (QDs) are the most promising zero-dimensional material system for use as single-photon sources which areessential for quantum information and in novel photonics devices such as lasers,solar cells, detectors, light-emitting diodes due to the ability to control their opticalproperties and the growth process. Stranski-Krastanov (SK) is the most usedgrowth method on lattice-mismatched substrates. Droplet epitaxy (DE) growthmethod was proposed as an effective way of fabricating QDs without wettinglayer (WL) for both lattice-matched and lattice-mismatched epitaxial systems.Due to the lack of WL, the DE QDs might have improved carrier confinement withhigh optical quality. DE offers advantages over the conventional SK method andthus a unique route to the fabrication of unpredicted nanostructures. Typically,DE uses low temperature for QD growth to prevent material redistribution.However, the low temperature growth hinders the good optical quality of thegrown QD structures. In this work, we fabricated InAs QDs by DE mode onundoped (100) GaAs substrates using solid-source molecular beam epitaxy atelevated substrate temperatures above 400 °C. We report on the observation oftriggered single-photon emission from a single QD. The morphological andstructure properties are investigated. Their optical properties are characterizedusing single-dot spectroscopy and time resolved spectroscopy. The excitonicstates of a single QD are identified using power-dependent and time-resolvedmeasurements on mesa-patterned samples.

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TuP2-2 | Influence of Heat Treatment on Optical and StructuralProperties of Self-assembled Thin Films of MPS-capped ZnSQuantum Dots (#87)Kenan Koç 1, Fatma Zehra Tepehan2, Galip G. Tepehan3

1Yildiz Technical University Department of Physics, Esenler, 34210 Istanbul,Turkey 2Istanbul Technical University Department of Physics, Maslak, 34469 Istanbul,Turkey 3Kadir Has University Faculty of Arts and Sciences, Fatih, 34083 Istanbul, Turkey ContentFor this study, we prepared colloidal ZnS quantum dots using 3-mercaptopropyltrimethoxysilane (MPS) as the capping agent. Colloidal quantumdots were self-assembled directly on a glass substrate by sol-gel spin coatingmethod without introducing any matrix. The films were heat-treated at 225, 250,275, 300 and 325 °C for 1 hour. The optical and structural characteristics of thefilms were examined by UV-visible spectrometer, NKD spectrometer, atomicforce microscope (AFM), scanning electron microscope (SEM) and profilometer.As a result of these investigations, the refractive index, extinction coefficients,dielectric constants, and the thicknesses of the films were determined. Theresults showed that the dimension of ZnS quantum dots changed from 3 to 4 nmwith thermal heat treatment due to Oswald ripening. The thicknesses of the filmswere found around 75 nm and the refractive index of the films at 550 nm wasfound in between 1.6 and 1.8. AFM measurements was perfomed to investigatea relation between the Rms values and packing density of the self-assembledthin films of MPS-capped ZnS quantum dots. References1- Koç, K., Tepehan, F.Z. and Tepehan, G.G., 2011. Characterization of MPS Capped CdS Quantum Dots andFormation of Self-Assembled Quantum Dots Thin Films on a Glassy Substrate, Chalcogenide Letters, 8, 239- 247. 2-Singh, J. and Whitten, J. E., 2008. Adsorption of 3-mercaptopropyltrimethoxysilane on silicon oxide surfaces andadsorbate ınteraction with thermally deposited gold, J. Phys. Chem. C, 112, 1908819096 3- Rao, C.N.R., Müller, A.and Cheetham, A.K., 2007. Growth of Nanocrystals in Solution, in Nanomaterials chemistry: recent developmentsand new directions, Wiley-Vch Verlag GmbH & Co., Weinheim. 4- Thielsc, R., Bohme, T. and Bottche, H., 1996.Optical and Structural Properties of Nanocrystalline ZnS-SiO2 Composite Films, phys. stat. sol. (a) 155, 157 -170 5-Wu, X., Lai, F., Lin, Y., Huang, Z. and Chen, R., 2007. Effects of substrate temperature and annealing on thestructure and optical properties of ZnS film, Proc. SPIE, 6722, 67222L-1. 6- Koo, H. K., Jeong, S. M., Choi, S. H.,Kim, W. J. and Baik, H. K., 2005. Effects of the Polarizability and Packing Density of Transparent Oxide Films onWater Vapor Permeation, J. Phys. Chem. B, 109, 11354-11360

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Figure 1:Variation of refractive index with wavelength for self-assembled thin films of MPS-capped ZnS quantumdots heat treated at different temperatures.

Figure 2:AFM images of self-assembled thin films of MPS-capped ZnS quantum dots heat treated at differenttemperatures

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TuP2-3 | Raman Scattering of InAs/AlAs Quantum DotSuperlattices Grown on (001) and (311)B GaAs Surfaces. (#90)Alexander Milekhin 1,2, Nikolay Yeryukov1, Alexander Toropov1, Dmitry Dmitriev1,Evgeniya Sheremet3, Dietrich R. T. Zahn3

1Institute of Semiconductor Physics, Lavrentjev av, 13, 630090 Novosibirsk,Russia2Novosibirsk State University, Pirogovstr, 2, 630090 Novosibirsk, Russia3Chemnitz University of Technology Semiconductor Physics, ReichenhainerStraße 70, D-09107 Chemnitz, Germany ContentSemiconductor nanostructures such as quantum dot superlattices (QD SLs) offerunique opportunity of engineering their electron and phonon spectra with themost appropriate properties for nanodevices. Among other optical techniquesRaman spectroscopy is considered as the most informative method fordetermining phonon spectra of semiconductor nanostructures [1]. We present acomparative analysis of Raman scattering by acoustic and optical phonons inInAs/AlAs QD SLs grown on (001) and (311)B GaAs surfaces. Samplescomposed of 20 periods of InAs QD layers with a nominal thickness of 2.8monolayers separated by AlAs spacer layers with thicknesses of 6, 8, 10, and 13nm were grown by molecular beam epitaxy in the Stranski-Krastanow growthmode. Raman scattering from the planar surface and the cleaved edges of thenanostructures was investigated. A microscope was employed to focus the lightto a 1 µm spot. Doublets of folded longitudinal acoustic (FLA) phonons up to 4thorder were observed in the Raman spectra of (001)- and (311)B-oriented QD SLsmeasured in the z(x,x)-z scattering geometry. The energy positions are welldescribed by the elastic continuum model of Rytov [2]. The in-plane Ramanscattering spectra measured in the y’(x’,x’)-y’ geometry reveal changing energypositions and intensities of the FLA doublet components consistent with thechanging effective wave vector in the nanostructures induced by the momentumtransfer of the light. Besides the acoustic phonons the spectra display featuresrelated to confined transverse and longitudinal optical as well as interfacephonons in QDs and spacer layers. Their frequency positions are discussed interms of phonon confinement, elastic stress, and atomic intermixing. The workwas supported by the following projects: DFG project ZA146/22-1, RFBR-DFG11-02-91348, RFBR 11-02-90427-Ukr_a. References[1] A.Mlayah and J.Groenen, in Light Scattering in Solids IX, Topics Appl. Physics, 108, M.Cardona, R.Merlin, Eds.(Springer-Verlag, Berlin, Heidelberg, 2007), pp. 237-314. [2] M.Rytov, Sov. Phys. Acoust. 2, 68 (1956)

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TuP2-4 | A Groove Patterns on Transfer Rollers-Based Micro-Electrochemical Etching for Circuits Construction on iPhoneTouchscreens (#151)P.s. Pa National Taipei University of Education Department of Digital Content Design,Graduate School of Toy and Game Design, No.134, Sec. 2, Heping E. Rd.,,Taipei 106, Taiwan ContentThe study objective lies in designing a system with micro-electrochemical etching(MEE) by utilizing the iPhone surface ITO thin membrane circuit to map out aninnovative fabrication system, and to provide a premise in designing the project’sillustrated example. The research objective has been to replace the highproduction cost required for the multiple processes and issues concerningenvironmental pollution in the present condensed circuitry line etching fabricationfor producing the TFT LCD’s and touch panels. The study adopts MEE as thetechnological premise for iPhone surface ITO thin membrane etching to removethe conductive material ITO deposited on the D.C. positive charge. Bycoordinating the groove patterns on transfer rollers as the template for etching onthe iPhone ITO thin membrane layer with pattern-like micro-fine lines, it simplifiesthe previous metal etching’s multilevel processes (the photoresist coating,exposure, imaging, etching of the photoresist and so forth) into a simple one-stepprocess (groove patterns on transfer rollers-based MEE). The study findingsshow that: using the appropriate process parameters (including the electricalconditions; electrochemical liquid control; electrochemical byproduct removal andsuch) is able to derive a preferred etching quality on the line’s side flange. Usinga higher rotational speed of the transfer rollers is able to derive a higher ITO lineetching speed. Using a smaller electrode gap or a larger processing fluid velocitycan all derive a higher removal speed on iPhone ITO line etching. Using asmaller diameter of the transfer rollers, or a smaller tool electrode is able toderive a higher iPhone ITO line etching speed. The pulsed current is conducivein rapidly removing the electrochemical byproduct and is also able to execute afaster work object’s feeder rate, but does bring up the designated current input.Using a larger current power, coordinated with a higher work object feeder rate,is able to derive a faster iPhone ITO line etching efficiency. As the groovepatterns on transfer rollers-based MEE the study proposes is able to rapidly mapout a micro-fine line pattern on the iPhone surface’s iPhone ITO thin memberlayer within a relative short time, the study has a MEE system mechanicalmodule design and fabrication process for iPhone surface ITO thin member linesto offer the industry a high-efficiency, low-cost innovative process technology.

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Fig. 1 :System module of A Groove Patterns on Transfer Rollers-Based Micro-Electrochemical Etching forCircuits Construction on iPhone Touchscreens

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TuP2-5 | Enhancement in light emission efficiency of Sinanocrystal light-emitting diodes by a SiCN/SiC superlattice(#169)Chul Huh 1, Chel-Jong Choi2, Bong Kyu Kim1, Byoung-Jun Park1, Eun-Hye Jang1,Sang-Hyeob Kim1

1Electronics and Telecommunication Research Institute IT ConvergenceTechnology Research Lab., 138 Gajeongno, Daejeon 305-700, Korea Republic(South)2Chonbuk National University Department of BIN Fusion Technology, 567Baekje-daero, Deokjin-gu, Jeonju-si 561-756, Korea Republic (South) ContentRecently, Si nanocrystals (NCs) has attracted the most attention as a promisinglight sources for the next generation of Si-based nanophotonics [1, 2]. Si NCsshow a quantum confinement effect that increases in overlapping of electron-holewave functions, leading to an enhancement in luminescence efficiency [3]. Inaddition, the optical band gap of Si NCs can be easily tunned by changing thesize of NCs, meaning that Si NCs are of particular interest as a light-emittingdiode (LED) covering whole visible wavelength range. A reliable, simple, andpractical device design is very crucial in the fabrication and an enhancement inlight emission efficiency of Si NC LED. We present here the concept that canuniformly inject the electrons into Si NCs by employing the 5.5-periods ofSiCN/SiC superlattice, leading to an enhancement in the light emission efficiencyof Si NC LED. The Si NCs embedded into a silicon nitride (SiNx) matrix was in-situ grown by a PECVD. A 5.5-periods of SiCN(3 nm)/SiC(3 nm) superlattice wasdeposited on the Si NCs embedded into the SiNx matrix at 300 ºC by a PECVD.A mesa-type Si NC LED was fabricated by using inductively coupled plasmaetching and standard photolithographic technique. Figure 1 shows a schematicillustration of the Si NC LED with 5.5-periods of SiCN/SiC superlattice. The Ncomposition into the SiCN layer into the superlattice was about 18 %. The opticalband gaps of SiCN and SiC layers into the superlattice were estimated to bearound 2.6 and 2.2 eV, respectively. The electrical properties such as current-voltage characteristic and series resistance of the Si NC LED were greatlyimproved by employing the superlattice structure. In addition, light output powerof the Si NC LED with the superlattice was enhanced by 50 %, as shown in Fig.2. These results can be attributed to an enhanced current spreading into the SiNCs through the 5.5-periods of SiCN/SiC superlattice due to the formation of 2-dimensional electron gas at the SiCN/SiC interface. We will discuss on theelectrical and optical properties of Si NC LED with 5.5-periods of SiCN/SiCsuperlattice in detail. Acknowledgements This work was supported by theConverging Research Center Program through the Converging ResearchHeadquarter for Human, Cognition and Environment funded by the Ministry ofEducation, Science and Technology (Grant Code: 2010K001126).

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References[1] L. Pavesi, L. Dal Negro, C. Mazzoleni, G. Franzo, and F. Priolo, Nature 408, 440 (2000). [2] N. M. Park, T. S. Kim,and S. J. Park, Appl. Phys. Lett. 78, 2575 (2001). [3] L. Pavesi and D. J. Lockwood, Silicon Photonics: Siliconfundamentals for photonic applications. Heidelberg, Berlin (2004).

Figure 1:A schematic illustration of the Si NC LED with 5.5-periods of SiCN/SiC superlattice.

Figure 2:Light output powers of the Si NC LEDs with and without 5.5-periods of SiCN/SiC superlattice, respectively.

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TuP2-7 | Optical properties of Ni, Cu nanowire arrays and Ni/Cusuperlattice nanowire arrays (#257)Y.y. Zhang1, Y. M. Xiao1, G. T. Fei2, Wen Xu 1,2

1Yunnan University Department of Physics, Kunming 650091, China2Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031,China ContentIn recent years, quasi-one dimensional (1D) nanostructure materials havereceived much attention due to their potential applications in novel and advancedelectronic, optical and optoelectronic devices. Very recently, we havesuccessfully fabricated Ni, Cu and Ni/Cu superlattice nanowire array systems[1-3] using the techniques such as the electrochemical deposition and the growthfrom porous anodic alumina oxide (AAO) templates (pore size about 50 nm) withan Au film layer about 200 nm sputtered onto back side as the working electrode.In this work, we performed the optical measurements on these nanowire arraystructures. Optical reflectance (OR) of the as-prepared samples was recorded byimaging spectrometor in the range of 300 to 900 nm, and the xenon lamp wastaken as white incident light. The measurement temperatures were set to be 4.2,70, 150 and 300 K respectively. We find that the amplitude of the OR spectra inNi, Cu and Ni/Cu superlattice nanowire array samples depend strongly ontemperature (see Fig. 1). When T150 K, the OR intensity decreases with T.Moreover, at 4.2 K there are two wide reflection peaks around 550-700 nm and700-850 nm and the reflectance amplitude around 700-850 nm is higher than thataround 550-700 nm. These are quite different from the spectra observed athigher temperatures where these two peaks cannot be seen obviously and550-700 nm range is much higher than 700-850 nm one as temperatureincreases. It shows that nanowire arrays have low reflectance which implies thestrong light absorption in the range of 550-700 nm at low temperature. We hopethese findings can gain an in-depth understanding of the optoelectronicproperties of metal nanowire array structures. References[1] Wang XW, Fei GT, Xu XJ, Jin Z, and Zhang LD:Size-Dependent Orientation Growth of Large-Area Ordered NiNanowire Arrays. J. Phys. Chem. B 2005, 109:24326-24330. [2] Xu SH, Fei GT, Zhu XG, Wang B, Wu B and ZhangLD. A facile and universal way to fabricate superlattice nanowire arrays. Nanotechnology 2011, 22:265602. [3] ZhouW F, Fei GT, Li X F, Xu SH, Chen L, Wu B, and Zhang LD. In Situ X-ray Diffraction Study on the Orientation-Dependent Thermal Expansion of Cu Nanowires. J. Phys. Chem. C 2009, 113:9568–9572.

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Fig1:The optical reflectance spectra of a Cu nanowire array sample for different temperatures.

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TuP2-8 | Investigation of single buried InAs quantum dots byscanning near-field nano-spectroscopy (#258)Rainer Jacob1, Markus Fehrenbacher 1, Stephan Winnerl1, JayeetaBhattacharyya1, Harald Schneider1, Manfred Helm1, Hans-Georg von Ribbeck2,Lukas M. Eng2, Paola Atkinson3, Armando Rastelli3, Oliver G. Schmidt3

1Helmholtz-Zentrum Dresden-Rossendorf Institute of Ion Beam Physics andMaterials Research, P.O. Box 510119, 01314 Dresden, Germany 2TU Dresden Institute of Applied Photophysics, TU Dresden, 01062 Dresden,Germany 3Leibniz Institute for Solid State and Materials Research Institute for IntegrativeNanosciences, Helmholtzstraße 20, 01069 Dresden, Germany ContentSince providing optical resolution on the nanometer length scale, scanning near-field optical microscopy (SNOM) is a powerful technique to study the opticalproperties of nanoscale objects. For example SNOM at infrared frequencies hasenabled studies of superlensing effects in perovskite structures [1] and aquantitative characterization of microstructured buried doping profiles insemiconductors [2]. Materials can be distinguished by their interaction with theprobe, hence yielding different near-field signals that depend on the localdielectric constants. For our investigations we used a scattering-type-SNOM (s-SNOM) made up from a non-contact atomic force microscope (AFM) whose tipacts as the scattering center for incident photons. Operating in the mid- and far-infrared regime, the widely tunable free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf serves as an intense and coherent light source.This setup allows to investigate the electronic structure of single self-assembledInAs quantum dots (Q-dots) [3], capped with a 70 nm thick GaAs layer. Althoughcommonly used as a surface sensitive technique, we demonstrate that s-SNOMalso probes sub-surface features such as buried Q-dots. In fact, ourspectroscopic near-field scans performed at room temperature clearly identifiedtwo electronic inter-sublevel transitions within single Q-dots at 85 meV and 120meV. Consequently the linewidth of these transitions measure 5 - 8 meV only,hence being significantly smaller as compared to the inhomogeneouslybroadened peaks resulting from integral photoluminescence measurements. Moreover, spatially scanning the s-SNOM tip at fixed excitation energies allowesmapping the spatial distribution of such buried Q-dots, as shown in Fig. 1. References[1] S. Kehr et al. Nature Comm. 2, 249 (2011) [2] R. Jacob et al., Opt. Express 18, 26206 (2010) [3] R. Jacob, PhDthesis, TU Dresden (2011)

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Fig.1:a) Topography of individual, buried quantum dots, measured by nc-AFM. b) s-SNOM scan at a photonenergy of 85 meV (14.4 µm), and c) at 91 meV (13.6 µm). Obviously, the near-field contrast is stronglywavelength dependent.

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TuP2-9 | Plasmonic enhancement of photoluminescence inhybrid Si nanostructures with Au fabricated by fully top-downlithography (#277)Koudou Nakaji1, Hao Lee1, Takayuki Kiba 1,2, Makoto Igarashi3,2, SeijiSamukawa3,2, Akihiro Murayama1,2

1Hokkaido University Graduate School of Information Science and Technology,Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan 2Japan Science and Technology Agency CREST, 5 Sanbancho, Chiyoda-ku,Tokyo 102-0075, Japan 3Tohoku University Institute of Fluid Science, 2-1-1 Katahira, Aoba-ku, Sendai980-8577, Japan ContentPlasmonic effects induced by metallic nanostructures, such as, significantenhancements of PL intensity in semiconductor nanostructures, are veryattractive, because optical responses can be controlled in nanometer scales.However, fully top-down fabrication of semiconductor nanostructures indicatingthe plasmonic effects have not been established yet, because the plasmoniceffects appear when the optically active nano-materials are placed close to themetallic nanostructures, typically at 10 nm. To solve this problem, we haveemployed high-density Si nanodisks fabricated using bio-templates.[1,2] Wehave demonstrated plasmonic enhancements of photoluminescence (PL) invisible light region from hybrid Si nanostructures with Au, where these hybridnanostructures were fabricated by fully top-down lithography techniques (Figure1). The separation distance between both the nanostructures was controlled byinserting a SiO2 layer with the thickness of 3 nm. Si thin films with the thicknessof 8 nm were deposited on SiO2 substrates. High-density one-dimensional Sinanodisk arrays were fabricated by damage-free neutral-beam etching using bio-templates consisting of ferritin supramolecules.[1] The diameter and interspacingwere intentionally designed at 10 and 2 nm, respectively, by protein engineering.After capping with 3 nm-thick SiO2 layers on the top of the nanodisk arrays, 40nm-thick Au thin films were deposited. Then, square-shaped Au nanoplates withvarious sizes were fabricated by electron-beam lithography. PL spectra wereobserved at 150 K by using micro-PL with the spatial resolution of 1 mm. Weobserve that PL intensities in the Si nanodisks are enhanced by factors up to 5depending on the wavelength by integrating with the Au nanoplates. Thisenhancement is also dependent on the size and shape of the Au nanoplates.The Au nanoplates with the lengths of one side of 100 - 200 nm show the clearPL enhancement, where the edge shape of the square pattern has successfullybeen reproduced. We find that the wavelength region of the PL spectrumindicating the enhancement correlates well with spectral peaks of differentialreflection due to the Au nanoplates. Therefore, we attribute the PLenhancements observed in the present hybrid Si/Au nanostructures to plasmoniceffects originating from the square-shaped Au nanoplates.

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References[1] C-H. Huang, X-Y wang, M. Igarashi, A. Murayama, Y. Okada, I. Yamashita, and S. Samukawa, Nanotechnology 22, 105301 (2011). [2] T. Kiba, Y. Mizushima, M. Igarashi, C-H. Huang, S. Samukawa, and A.Murayama, Appl. Phys. Lett. 100, 053117 (2012).

Figure 1:SEM images of Au nanoplates fabricated on a Si nanodisk array (a) and the Si nanodisk array (b)

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TuP2-10 | Study of N/ In Compositional Modulation inGaInNAsSb Multiple Quantum Wells using Magneto-photoluminescence (#305)Kylie O'shea Lancaster University Physics Department, Lancaster, Great Britain ContentGaInNAsSb multiple quantum wells provide an opportunity to make a GaAs-based laser at 1.55 µm that could operate at temperatures up to 85oC.Introducing N lowers both the lattice constant and bandgap energy [1]. However,N also narrows the growth window and reduces the material quality significantly,making it difficult to produce good devices [2]. The addition of Sb as a surfactantis intended to improve the growth, whilst still extending the wavelength, but thusfar the material still shows deterioration due to N. Degraded laser performancein GaInNAsSb lasers has been observed due to the compositional modulation ofIn and N in the quantum wells [3]. These are periodic fluctuations in thecomposition of GaInNAsSb in the plane of the quantum wells. In areas with highIn incorporation the bandgap is reduced, while if more N is present, only theconduction band is lowered. Sub-energy levels are formed by the undulations inthe bandgap, creating multiple possible transitions for the carriers, and reducingthe functionality of the laser. Temperature dependent magneto-photoluminescence has been shown to give remarkable insight into both thelength scale and the amplitude of composition modulation in quantum wells [4].While a strong magnetic field allows measurement of the length scale of themodulation, a temperature-dependent study reveals the depth of the electron-confining potential in the conduction band due to excess N and the hole-confining potential in the valence band due to excess In. In order to find out moreabout compositional modulation in GaInNAsSb multiple quantum wells, andassess the prospects for exploiting this material in dilute-nitride lasers withimproved performance, temperature-dependent magneto-photoluminescencemeasurements are taken for a range of GaAs-based multiple quantum wellsamples; InGaAs, InGaAsSb and InGaAsN, as well as for GaInNAsSb itself. Toensure a comparative study all of the samples have similar growth conditions,with the percentages of In, N and Sb either maintained at constant level or set tozero. The importance of this research is to understand the phenomena ofcompositional modulation, in order to be able to avoid (in the case of telecomslasers) or harness (in the case of broad band semiconductor optical amplifiers,where the fluctuations are treated as quantum dots [5]) the phenomena to createimproved GaInNAsSb devices. Acknowledgements: This work is supported byEPSRC and Oclaro Inc. References[1] G, Jaschke, R, Averbeck, L, Geelhaar, J, Riechert, 2005, J. Cryst. Growth 378, 224-228 [2] S R, Bank, H, Bae, LL, Goddard, H B, Yuen, 2007, J. of Quan. Elect. 43, 773-785 [3] X, Sun, J, M, Rorison, Phys. Status Solidi C, 8,1646–1649 [4] T, Nuytten, M, Hayne, B, Bansal, H, Y, Liu, M, Hopkinson, V, V, Moshchalkov, Phys. Rev. B, 84 [5] J,Rorison, N, Vogiatzis, X, Sun, Optical Gain Studies for Dilute Nitrides for Application in Broad Band SOAs, presentedat 13th International Conference on Transparent Optical Networks ICTON 2011

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TuP2-11 | A comprehensive study of optical characterization ofn- and p- type as-grown and annealed modulation doped GaAs/GaInNAs QW structures (#310)Omer Donmez 1, Fahrettin Sarcan1, Ayse Erol1, M. Cetin Arikan1, Fatih Ungan2,Esin Kasapoglu2, Huseyin Sari2, Janne Puustinen3, Mircea Guina3

1Istanbul University Faculty of Science, Department of Physics, Vezneciler,34134 Istanbul, Turkey 2Cumhuriyet University Faculty of Science Department of Physics, 58140 Sivas,Turkey 3Tampere University of Technology Optoelectronics Research Center,Korkeakoulunkatu 3, 33720 Tampere, Finland ContentWe report a comprehensive theoretical and experimental study on the opticalproperties of n- and p-type as-grown and annealed modulation dopedGa0.68In0.32NyAs1-y/GaAs (y = 0, 0.9, 1.2, 1.7) single quantum structures.Experimental characterization has been carried out temperature dependentphotoluminescence (PL) measurements. It is observed that the intensity of PLemission is higher for p-type samples and the effective band gap energy red-shifts with increasing N. Thermal annealing improves the optical quality, butcauses a blue-shift effect.The observed blue-shift increases with N amount forboth n- and p-type samples. The characteristic of temperature dependency of theband gap energy has been fitted using semi-empirical Varshni equation thatshows that the dependency of the alfa Varshni parameter decreases with Namount. The redshift of temperature dependence of bandgap becomes larger asN concentration increases. On the other hand, annealing process causes areduction in the temperature dependency of the band gap. In the theoretical partof the study,the electronic structure of the quantum well is calculated from theself-consistent numerical solutions of the coupled Schrödinger-Poisson equationswithin the envelope function approach and the effective mass approximation. Thevalance band of the samples is calculated by using the 4+6 band k.p model andthe finite element method (FEM) and the conduction band modification due to thepresence of nitrogen is explained by using the band anti-crossing model (BAC).

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TuP2-12 | Optical and electronic properties of GaSb-based typeII "W-shaped" quantum wells for the active region of interbandcascade lasers emitting in the range of 2-6 µm (#328)Filip Janiak 1, Grzegorz Sek1, Marcin Motyka1, Krzysztof Ryczko1, Kazuto Koike1,Adam Bauer2, Sven Höfling2, Martin Kamp2, Alfred Forchel21Wroclaw University of Technology Institute of Physics, Wyb. Wyspianskiego 27,50-370 Wroclaw, Poland 2University of Würzburg Technische Physik, Am Hubland, D-97074 Wurzburg,Germany ContentMid-infrared semiconductor lasers are continuously increasing their applicationrange during the last years including for instance gas sensing for detection andcontrol of the presence or concentration of harmful gases like CO2, SOx, NH3,and many others. The benefits of optical detection methods have been limitedmainly by the lack of suitable laser light sources, which have to provide thesensing wavelength in single mode and continuous wave (cw) operation in orderto provide the required wavelength and its tunability. Hereby, we presentfundamental optical and electronic properties of a type IIGaSb/AlSb/InAs/GaIn(As)Sb/InAs/AlSb/GaSb quantum well system potentiallyable to cover spectrally the range of 2 to 6 µm, and beyond, and is possible to beintegrated in a photonic sensor unit for gas detection. The design underconsideration has been introduced in order to enhance the oscillator strength(electron – heavy hole wave functions overlap integral) of the fundamental type IIoptical transition. Spectroscopic experiments at low temperatures, asphotoluminescence and photoreflectance, allowed us to probe the opticaltransitions, including the spatially indirect ones, and their unambiguousidentification after the comparison to the energy level calculations within 8-bandkp model including strain. Based on that the band gap discontinuities in such acomplex system could also be estimated. The fundamental optical transitionoscillator strength in type II ‘‘W’’- shaped quantum wells has been investigatedexperimentally and theoretically in a function of layers composition andthicknesses. We indicate the potential of such type II structures to work in arange 2 to above 6 µm. There has been shown that the transition intensity canbe tailored efficiently via decreasing the indium content in the layer confiningholes. Eventually, it has been demonstrated that replacing the ternary GaInSbmaterial in the valence band well with a quaternary one of GaInAsSb can causethe oscillator strength enhancement by almost a factor of two with respect to thelatter. Additionally, we present results of photoluminescence thermal quenchingfor samples with different width of the InAs and GaInSb layers. Possible carrierloss mechanisms have been connected with tunneling of the holes form activeregion into the surrounding GaSb layers.

References[1] G. Sęk, F. Janiak, M. Motyka, K. Ryczko, J. Misiewicz, A. Bauer, S. Höfling, A. Forchel, Carrier loss mechanisms

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in type II quantum wells for the active region of GaSb-based mid-infrared interband cascade lasers, Optical Materials,Volume 33, Issue 11, September 2011, Pages 1817-1819, [2] M. Motyka, K. Ryczko, G. Sęk, F. Janiak, J. Misiewicz,A. Bauer, S. Höfling, A. Forchel, Type II quantum wells on GaSb substrate designed for laser-based gas sensingapplications in a broad range of mid infrared, Optical Materials, Volume 34, Issue 7, May 2012, Pages 1107-1111, [3]F. Janiak, G. Sęk, M. Motyka, K. Ryczko, J. Misiewicz, A. Bauer, S. Höfling, M. Kamp, A. Forchel, Tailoring theoptical transition oscillator strength in GaSb-based type II quantum wells, APL, under review

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TuP2-13 | Effect of Be doping on the optical properties ofcatalyst free MBE-VLS grown GaAs nanowires on Si (111)substrate (#337)Akio Suzuki 1, Atsuhiko Fukuyama1, Ji-Hyun Paek2, Masahito Yamaguchi2,Tetsuo Ikari11University of Miyazaki Faculty of Engineering, 1-1, Gakuen Kibanadai-nishi,Miyazaki, Miyazaki 889-2192, Japan 2Nagoya University Department of Electrical Engineering and Computer Science,C3-1-631 Furo-cho, Chikusa-ku, Aichi, Nagoya 464-8603, Japan ContentGaAs nanowires (NWs) attract attention for the application to photonic andelectronic devices. Although the most NWs had been grown by a vapor-liquid-solid (VLS) mechanism using gold as a catalyst so far, we have succeeded infabricating the catalyst-free GaAs NWs on a Si (111) substrate using acombination of molecular beam epitaxy and VLS methods [1]. In this study, weinvestigate the effects of Be-doping on the optical properties of GaAs NWs byusing the photoluminescence (PL) and photoreflectance (PR) techniques. Theshape and the size of the NW samples were estimated at 100 nm and 10 µm,respectively. No effect of the Be-doping on the grown wire size could bedetected. Figure shows the temperature dependences of the critical energy Ec ofnon-doped and Be-doped NWs samples estimated from PR. We have alreadyreported [2] that the PR spectrum of the non-doped NWs sample was wellexplained by an Aspnes formula and the estimated temperature change of Ec

agreed well with that of the energy gap Eg of bulk GaAs. In contrast, Ec of Be-doped NWs sample was lower than that of non-doped NWs sample in the wholetemperature region. If the impurity concentration becomes high, the decrease ofEg may be understood. However, the temperature dependence in the lowertemperature range was different from the GaAs bulk. Since the thermalexpansion effect accounts for the rather flat change of the temperaturedependence of Eg in the low temperature region [3], the deformation potential andthe linear thermal expansion coefficient may change by Be doping. Since thenanowire has a limited size, the effect of Be doping may differ from that in bulkcrystal. Further discussion for their impurity levels and the relationship betweenthe crystal nanostructure and the electronic transition should be discussed. References[1] J. H. Paek, et al., Phys. Stat. Sol. 6, 1436 (2009). [2] A. Suzuki, et al., Jpn. J. Appl. Phys., 50, 06GH08 (2011). [3]T. Mishima, et al., J. Appl. Phys., 91, 4904 (2002).

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Fig. 1:Temperature dependences of Ecs estimated from PR analysis of non-doped and Be-doped NWs samples.

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TuP2-15 | On the generalized Hartman effect presumption insemiconductors and photonic structures (#353)Herbert P. Simanjuntak 1, Pedro Pereyra2,3

1FMIPA, Universitas Indonesia Departemen Fisika, Jakarta 16424, Indonesia 2Universidad Autónoma Metropolitana-Azcapotzalco Ciencias Básicas, Av. S.Pablo 180, 02200 Mexico, Mexico3University of Regensburg Institut für Experimentelle und Angewandte Physik,93040 Regensburg, Germany ContentThe Hartman effect is known as the independence of the tunneling time on thebarrier width as the width gets large. There is an idea that the tunneling time isindependent not only of the barrier width but also of the barrier separation, whichis called the generalized Hartman effect (GHE).1 An experiment to check thiseffect was performed by Longhi et al.2 using a system of two Bragg gratings withseparation a. We show that their five values of a do not prove the existence of theGHE. Most of the theoretical conclusions are based on questionable formulasand unnecessary calculations. In proving, we analyze different electronic andphotonic structures to show that the so-called GHE is an erroneous presumption.The resonant character of the phase time, obtained for electron tunneling andtransmission of electromagnetic waves through superlattices and Bragg gratings,show clearly that such effect can not be expected to occur. The resonantbehavior of the transmisson time in figures 1a, 1b, and 2a, show clearly that NoHartman effect can be inferred. A reinterpretation of the experimental results indouble Bragg gratings is proposed. References1. V. S. Olkhovsky, E. Recami and G. Salesi, Europhys. Lett. 57, 879 (2002). 2. S. Longhi, P. Laporta, M. Belmonte,and E.Recami, Phys. Rev. E 65, 046610 (2002).

Figure1.gif:The tunneling time as the number of cells n is varied. (a) Saturation of superlattice tunneling time τn, forelectron energies E = 0.15 eV and E = 0.2 eV in the gap. (b) As energy approaches the band-edge, moreresonances appear as n is increased.

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Figure2.gif:In (a) the phase time (PT) as a function of the separation a between two Bragg gratings. In (b) and (c) thePTs plotted as functions of ω, for a=42mm. The phase times in (b) and (c) can be compared with Fig. 2 ofRef. 2.

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TuP2-16 | ZnO-based microwire quantum well heterostructuresfor cavity applications (#364)Martin Lange , Christof P. Dietrich, Michael Lorenz, Marius GrundmannUniversität Leipzig Institut für Experimentelle Physik II, Linnéstraße 5, 04103Leipzig, Germany ContentNowadays, the prerequisites for highly efficient lasing are the integration of low-dimensional active regions and optimal light confinement. The former can beobtained by incorporating quantum wells (QW) whereas the latter can be realizedby eigenmodes such as whispering gallery modes (WGM) observed e.g. inmicrowires or disks. In this work, we report on ZnO-based microwire QWheterostructures (QW-HS) that are utilized as photonic emitter as well as highquality dielectric resonator [1]. The investigated QW-HS facilitate the spectral andspatial overlap of WGM and QW excitons as observed in luminescencemeasurements. The QW-HS were fabricated by pulsed-laser deposition (PLD) inradial direction on non-polar side facets of either carbothermally grown ZnOmicrowires or high-pressure PLD grown ZnO nanowires, by using an off-anglePLD plasma process. In order to obtain QWs that emit spectrally below bulk ZnO,multiple ZnCdO-QWs were embedded between MgZnO barriers. The resultingQW-HS exhibited diameters in the order of some µm or some hundred nm for themicro- or nanowires, respectively. Resonators with such a size should make theobservation of optical eigenmodes possible. The quantum-confinement effect isinvestigated by a systematic reduction of the QW-thickness to values below 1nm,and proven by a strong blue-shift of the QW-related luminescence. Due to thehigh Cd-content in the active layer [2], a wide spectral range between 2.5 eV and3.5 eV is accessible. The almost perfect homogeneity of the shell-thickness isverified by scanning measurements along the wire axis. Further, all fabricatedQW-HS exhibit photonic eigenmodes covering the wire emission in particularalso the QW-emission. These modes were unambiguously assigned to WGMpassing the entire wire. The mode pattern is modelled taking into account theresonator-geometry and the correct values of the index of refraction. Possibleabsorption mechanisms in the heterostructures which explain the absence ofWGM energetically above the QW-luminescence for the heterostructures withmicrowire cores are discussed, in order to complete the picture of the observedphotonic modes. With this work, we demonstrate the successful combination ofexcitonic QW emission with optical eigenmodes and therefore a first step towardsstrong light-matter interaction and ultra-low threshold lasing. References[1] C.P. Dietrich et al., Appl. Phys. Lett. 100, 031110 (2012). [2] M. Lange et al., Phys. Status Solidi RRL 6, 31(2012).

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Figure 1:Cathodoluminescence spectra of the quantum well heterostructures with micro- (blue) and nanowire(green) core. The QW-emission at about 2.75 eV is modulated by WGM. Schemes of the cross sectionsare shown with possible WGM pathways indicated as lines.

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TuP2-17 | A Study of Photomodulated Reflectance on Staircasen-type GaAs/AlxGa1-xAs Quantum Well Structures (#372)Omer Donmez1, Ferhat Nutku 1, Ayse Erol1, M. Cetin Arikan1, Yuksel Ergun2

1Istanbul University Faculty of Science, Department of Physics, Vezneciler,34134 Istanbul, Turkey 2Anadolu University Science Faculty, Department of Physics, 26470 Eskisehir,Turkey ContentIn this study, photomodulated reflectance technique has been carried out on twodifferent multi quantum well structures that consist of n-type doped GaAsquantum wells between undoped AlxGa1-xAs barrier layers with varying xconcentrations. Each period in the structures have three different barriercompositions producing staircase-like barriers.Themain difference between twostructures is the doping profile and the doping concentration of the quantumwells. Photomodulated reflectance (PR) spectra have been taken at roomtemperature using He-Ne laser as a modulation source and broadband spectrumof a tungsten halogen lamp as a probe light. The obtained spectra show thirdderivative-like behavior, therefore analyzed using Lorentzian line shape of thirdderivative functional form and line broadening. The fact that each quantum well inthe staircase part of the structure has different ground state energyleadstoseveral different optical transitions in the spectrum and it is difficult to resolveeach contribution arising from different QWs using conventionalphotoluminescence technique.To analyze the results, all energy levels in theconduction and valance band have been calculated by using transfer matrixtechnique undereffective mass and parabolic band approximations.Thecomparison of theoretical optical transition energies with PR results is found well-matched. Not only different peaks from different effective band values in thecomplex structures are resolved, but also high carrier density induced effects onband gap are determined using the PR results. In the light of obtained result, it isconcludedthat PR spectroscopy is very accurate experimental tool tocharacterize of even very complicated structures with a high accuracy.

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TuP2-18 | Room Temperature Passive Mode-Locked LaserBased on InAs/GaAs Quantum-Dot Superlattice (#390)Mikhail Sobolev , Mikhail Buyalo, Idris Gadzhiev, Ilya Bakshaev, Yurii Zadiranov,Efim PortnoiIoffe Physical-Technical Institute of the Russian Academy of Sciences Centre ofNanoheterostructure Physics, 26 Polytekhnicheskaya, 194021 St Petersburg,Russia Content For optical amplifiers and modulators, it is desirable to have polarization-independent characteristics of electroluminescence (EL) and absorption from thequantum dot (QD) structures. However, in standard uncoupled QD structures, theabsorption coefficient at the lasing wavelength for TE-polarized light differs by anorder. It is known that in structures with coupled QDs, the intensity of TMpolarization increases with the number of QD layers. Direct current modulation ofsemiconductor lasers does not meet the needs of modern high-speedcommunication lines. As more broadband alternative to the direct currentmodulation can be laser with integrated electro-optical modulator based on theStark effect. High-speed performance of Stark modulator is fundamentally limitedby physical processes. The modulation frequency ceiling can be determined bythe largest feasible frequency of the passive mode-locking regime (PML) in alaser fabricated from the same structure. In this communication, we report on aroom-temperature study a 10-layer system of tunnel-coupled In(Ga)As/GaAs QDsuperlattice (SLQD) incorporated into two-sectional lasers by using EL andabsorption spectroscopy. We have observed the EL and absorption spectra forlight polarized in the plane perpendicular to the growth axis (x–y) in the samespectral range as that for light polarized along the growth direction (z) of thestructure. No transitions involving light holes were observed in theelectroluminescence and absorption spectra. The observed behavior of themeasured signals allows one to conclude that the optical transitions for lightpolarized in the plane perpendicular to the growth axis and in the plane along thestructure growth direction involve ground states of heavy holes, whose wavefunctions have, in addition to the x and y components, a z component. In thissystem, the ratio between the light absorption coefficients for TE and TMpolarization is close to 1 in contrast to structures with unbounded QDs, where theratio is about 10. Lasing spectra lay in the range 1160–1170 nm, the FWHM ofthe spectrum is 5.2 nm. PML was observed in wide injection current range atreverse bias from –1 to –3 V with a repetition frequency of 12.5 GHz. It showsthe fundamental possibility of implementing a laser and modulator in amonolithically integrated design for optical-polarization-independent modulatorsused in fiber-optic communication lines.

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TuP2-19 | Optical properties of CdTe/PbTe quantum wells andquantum dots emitting in a mid infrared range (#394)Filip Janiak 1, Marcin Motyka1, Krzysztof Ryczko1, Grzegorz Sek1, JanMisiewicz1, Kazuto Koike2, Takanori Hotei2, Mitsuaki Yano2

1Wroclaw University of Technology Institute of Physics, Wyb. Wyspianskiego 27,50-370 Wroclaw, Poland 2Osaka Institute of Technology, Asahi-ku Ohmiya, Osaka 535-8585, Japan ContentSemiconductor lasers operating in a mid infrared spectral range typically base ona groups III–V semiconductors compounds. An alternative solution discussedhere is to exploit the groups II – VI materials combination as PbTe/CdTe with theband gap at L point in the Brillioun zone. Such structures exhibit intrinsically lowefficiency ofnonradiative Auger recombination and without the degeneratedheavy-hole bands could be suitable for room temperature laser operations innanostructures as quantum wells or quantum dots. These wide band gapmaterial system could be a promising substitute of InAs and GaSb basedsemiconductor structures. CdTe/PbTe quantum wells (QW) and quantumdots (QD) were grown by molecular beam epitaxy (MBE) on a (100)-orientedGaAs substrate. Their optical and electronics properties have been investigatedby a combination of optical spectroscopy characterization and energy levelcalculations. Fourier transformed photoreflectance (PR) and photoluminescence(PL) have been employed, as nondestructive and highly sensitive methods, andare an efficient tools to study the energies of interband optical transitions in low-dimensional structures, including mid-infrared range 1] and hence can be usedas a post-growth technique of the multilayer system electronic structure probeand the growth accuracy verification. In order to determine accurately the opticaltransition energies and interpret the optical spectra properly, there have beencalculated the energies both electron and hole levels within the effective massapproximation [2], with the II-VI material parameters taken after [3]. Adependence of the optical transition vs temperature has been determined anddiscussed with respect to possible thermally-induced change of the transitioncharacter from type II into type I. References[1] Motyka M., Sek G., Janiak F., Misiewicz J., Klos K., Piotrowski J., Measurement Science & Technology22,125601(2011) [2] Erasmo A. de Andrada e Silva, Phys. Rev. B 60, 8859 (1999). [3] K. Koike, T. Honden, I.Makabe, F. P. Yan, M. Yano, Journal of Crystal Growth 257, 212 (2003).

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TuP2-20 | S-shaped temperature-dependentphotoluminescence shift in ZnCdSe / ZnSe multiple quantumwells (#399)Kun Gao 1, Wen-Chung Fan2, Slawomir Prucnal1, Wolfgang Skorupa1,Shengqiang Zhou1

1Helmholtz-Zentrum Dresden-Rossendorf Institute of Ion Beam Physics andMaterial Research, Bautzner Landstr. 400, 01328 Dresden, Germany 2National Chiao Tung University Department of Electrophysics, Ta-Hsueh Road1001, Hsinchu 30050, Taiwan ContentZnSe based materials and nano-structures have recently attracted muchattention as their promising prospects on applications of green-blue light emitters.It is worth investigating the emission mechanism from the viewpoints of bothphysical interests and devices design. In this contribution we report the opticalproperties revealed by time-integrated and time-resolved photoluminescence oftwo different ZnCdSe / ZnSe multiple quantum wells (MQW) prepared bymolecular beam epitaxy. We have observed an abnormal S-shaped variation ofemission peak (Ep) energy and bandwidth: Ep redshifts in the temperature rangeof 10–40 K, blueshifts for 40–70 K, and redshifts again for 70–300 K withincreasing temperature, accompanied with broadening, narrowing, broadening ofbandwidth, respectively. Random localized potential fluctuation (RLPF) in thewell layer acting as local traps for carriers is accounted for the phenomena. ByGaussian fit, the luminescence generated from the recombination of excitons inthe MQW can be well fitted by the combination of one free exciton peak and onelocalized exciton peak. From the different behavior of the samples with differentwell thicknesses, and the characters of luminescence from defects levels, wehave shown that the dominant mechanism of the RLPF in our case is due to thelocal thickness variations in the well layer rather than the divergence of Cdconcentration.

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S-shaped PL:PL emission energy shift in ZnCdSe / ZnSe MQW with respect to temperature

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TuP2-21 | Optical investigation on Ge1-xSnx alloys (#466)B. H. Tsai 1, J. Z. Chen1, K. Y. Wu1, H. H. Cheng1, Z. P. Yang2, Y. C. Chang2

1Center for Condensed Matter Science Graduate Institute of ElectronicsEngineering, 1, Roosevelt Road, Section 4, National Taiwan University, Taiwan,R.O.C., Taipei 106, Taiwan 2Research Center for Applied Sciences Academia Sinica, 128 Sec. 2, AcademiaRd., Nankang, Taiwan, R.O.C., Taipei 11529, Taiwan Content In a recent development, tin (Sn)—another group IV element—was employedin the growth of IV-IV compounds. The incorporation of Sn modulates thebandgap of the host IV-IV compounds, and, above a certain Sn composition, theenergy band of the IV-IV compounds changes from an indirect to a directbandgap. Here, we report an investigation on a series of Ge1-xSnx alloy withvarious Sn compositions up to 14% grown on Ge wafer using Molecular BeamEpitaxy. These samples have been analyzed by X-Ray to define the strain [1]. Tocharacterize band structure and optical properties of these Ge1-xSnx samples,we performed spectroscopic ellipsometer measurement. Both dielectric constantsof ε1 and ε2 in the range of 1 eV to 4 eV are deduced by the fitting of John-Herzinger model [2], which are shown in the Fig. 1 and 2, respectively. Severalcritical point features, corresponding to E1, E1+∆1, and E0’ transitions, areobserved in ε1 and ε2. Among of them, the strongest features, indicated by anarrow mark, are around ~2 eV assigned as E1 and E1+∆1 transitions,corresponding to the transition between top two valance bands to conductionband along <111> direction. The positions of E1 and E1+∆1 shift toward to lowerenergy as Sn composition increases. This trend is consistent with the empiricalprediction [3], which is plotted in the inset of Fig. 2. In conclusion, we havesuccessfully grown a serial of GeSn samples with wide range of Sn compositionon Ge substrate by Molecular Beam Epitaxy. Different from other groups, thesamples are not fully strained released according our X-Ray analysis. Moreover,we have experimentally demonstrated that the direct transitions can be tuned bySn composition and shift to lower energy as Sn composition increases. References[1] I. S. Yu, T. H. Wu, K. Y. Wu, H. H. Cheng, V. I. Mashanov et al, AIP Advances 1, 042118 (2011). [2] B. Johs, C.M. Herzinger, J. H. Dinan, A. Cornfeld, and J. D.Benson, Thin Solid Films 313-314, 137 (1998). [3] V. R. D’Costa, C.S. Cook, A. G. Birdwell, C. L. Littler, M. Canonico, S. Zollner, J. Kouvetakis, and J. Menendez, Phys. Rev. B 73,125207 (2006).

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Fig. 1.:Real part of the dielectric function of Ge1-xSnx samples.

Fig. 2.:Imaginary part of the dielectric function of Ge1-xSnx samples.

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TuP2-22 | LOCALIZED SUPERFICIAL PLASMON AS A PROBEOF MOLECULE FORMATION IN PAIRS OF METALLICNANOPARTICLES (#472)Angela Camacho, Mario Zapata-Herrera Universidad de los Andes Departamento de Física, Carrera 1 # 18 A -10, 110221BOGOTA, Colombia ContentThe light-matter interaction at nano-scale is nowadays one of the most importantitems in the artificial design of materials. In this work we present a study oflocalized surface plasmons (LSP) coupling in systems of two metallic nano-particles as a probe of artificial molecules formation. We calculate the dielectricfunction and the optical constants of the metallic nanostructures, which are verydifferent to the usual bulk constants, considering their nano-metric dimensions.Our systems are composed of metallic spheres, cylinders and ellipsoids forminghomo-dimers and hetero-dimers built up with copper, silver and gold arranged inseveral ways. We use the Finite Elements Method (FEM) to solve the classicelectromagnetic equations in matter and compare our results with numerical andanalytical calculations. We present the enhancement field factor at the middle ofthe pairs depending on the geometrical features of the systems under study. Wefollow its behavior as a function of: Light Polarization, particle size and shape,and distance between them. We observe the giant enhancement of the nearfield, as a result of LSP resonance and the charge distribution at the surface asfunction of the distance between the particles, allowing us in this way to definethe coupled pairs as dimers. We also report the plasmon frequency for homo-dimers and hetero-dimers and discuss the different physical concepts underlyingthe maximum near- field and maximum frequency. Finally, we analyze ournumerical results making a comparison with the simple theory of moleculeformation based in bonding and antibonding states.

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TuP2-23 | Micro-Raman characterization of GaN nanorods (#477)Paulina Kamyczek 1, Zbigniew Zytkiewicz2, Ewa Placzek-Popko1, EunikaZielony1, Marta Sobanska2, Kamil Klosek2, Anna Reszka2

1Wroclaw University of Technology Institute of Physics, WybrzezeWyspianskiego 27, 50-370 Wroclaw, Poland 2Polish Academy of Sciences Institute of Physics, Al. Lotnikow 32/46, 02-668Warsaw, Poland ContentMicro-Raman spectroscopy was used to study strain in GaN nanorods grown byplasma-assisted molecular beam Epitaxy (PAMBE) on Si(111) substrates. Thegrowth started by deoxidation of Si(111) substrate followed by its exposure to anitrogen flux. Then, self-organized growth of nanorods started at ~750 oC underhighly nitrogen-rich conditions. No catalyst was used to induce nucleation ofnanorods. The morphology of the samples was characterized by high resolutionscanning electron microscopy (HR-SEM). These studies showed that GaNnanorods obtained were ~350 nm long with diameter of 20 – 30 nm. They werehomogenously distributed and well oriented with the c-axis being perpendicularto the substrate. Two types of nanorods (hereafter labeled as A and B) grownwith different values of Ga source temperature TGa were studied. As seen inFig.1, the use of high temperature of Ga source (TGa ~820°C), i.e. large Ga flux,has led to a partial coalescence of nanorods in sample A. Reduction of Ga fluxduring growth of sample B (TGa ~800°C) resulted in an ensemble of separatednanorods. Micro-Raman spectroscopy was carried out with the use of Jobin–Yvon’s T64000 system equipped with a CCD camera. 514.5 nm line of Ar2+ laserwas used as an excitation source. Raman spectra show strong Si related signalat ~521cm-1 and weak structure corresponding to E2high GaN mode at 568cm-1.The intensity of the mode is, as expected, higher for the sample A. Comparisonof the Raman signals let us conclude that GaN nanorods are strain free for theE2high mode is equal to the bulk GaN mode. The same concerns Si substrate.Illumination by focused laser beam can lead to overheating of a sample anddownshift and broadening of Raman shift. In order to estimate the temperature ofthe sample the Stokes’ and anti-Stokes’ Raman spectra for the Si related signalwere collected and it was found that the temperature of the sample at highestapplied power (50mW) does not exceed 300K. It is anticipated however that thetemperature of nanorods grows upon illumination more significantly due to theirreduced thermal conductivity. In spite of this only a slight red-shift of the E2high

mode (568 cm-1 at 4mW down to 567.4 cm-1 at 90mW) is observed which can beattributed to local increase of temperature upon laser illumination.

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Fig. 1a.:SEM image of GaN nanorods grown on Si. A surface of the sample A (from the top).

Fig. 1b.:SEM image of GaN nanorods grown on Si. A surface of the sample B (from the top).

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TuP2-24 | Temperature dependent Raman investigation ofrolled up InGaAs/GaAs microtubes (#480)Evgeniya Sheremet1, R. D. Rodriguez1, D. J. Thurmer2,3, D. Lehmann 1, O. D.Gordan1, F. Seidel1, O. G. Schmidt2,3, Michael Hietschold4, Dietrich R. T. Zahn1

1Chemnitz University of Technology Semiconductor Physics, D-09107 Chemnitz,Germany 2Chemnitz University of Technology Material Systems for Nanoelectronics,D-09107 Chemnitz, Germany 3IFW Dresden Institute for Integrative Nanosciences, Helmholtzstrasse 20,D-01069 Dresden, Germany 4Chemnitz University of Technology Solid Surfaces Analysis Group, D-09107Chemnitz, Germany ContentLarge arrays of multifunctional rolled-up semiconductors can be mass-producedwith precisely controlled size and composition, making them of greattechnological interest for micro- and nano-scale device fabrication [1]. Themicrotube behavior at different temperatures is a key factor towards furtherengineering their functionality, as well as for characterizing strain, defects, andtemperature-dependent properties of the structures. For this purpose we probeoptical phonons of GaAs/InGaAs rolled-up microtubes using Ramanspectroscopy on defect-rich and defect-free microtubes. The microtubes arefabricated by selectively etching an AlAs sacrificial layer in order to release thestrained InGaAs/GaAs bilayer, all grown crystalline by molecular beam epitaxy(MBE). Pristine microtubes show homogeneity of the GaAs and InGaAs peakpositions and intensities along the tube which indicates a defect-free rolling upprocess, while for a cone-like microtube a downward shift of the GaAs LOphonon peak along the cone is observed. This feature can be correlated to thevarying degree of strain relaxation due to changes in the microtube diameter [2].Other type of defects including partially unfolded microtubes can also bedetected due to a higher InGaAs LO phonon intensity on such defective regions.In order to systematically characterize the temperature stability of the rolled-upmicrotubes, Raman spectra are acquired as a function of sample temperature upto 600 K. We observe that above 400K, the dispersion for GaAs and InGaAsoptical phonons differs and the area of the InGaAs peak increases with respectto the GaAs LO peak. Microtubes are seen to oxidize in ambient air under locallaser heating [3], therefore we also investigated the reversibility of thetemperature changes in order to define the temperature range in which thenanostructures remain stable. Acknowledgment The work was supported byDFG Research Unit 1713 “Sensoric Micro- and Nanosystems” and by theBundesministerium für Bildung und Forschung, Project “Kompetenznetzwerk fürNanosystemintegration – Anwendung von Nanotechnologien für energieeffizienteSensorsysteme (nanett)”, project number 03IS2011.

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References[1] A. A. Solovev, W. Xi, D. H. Gracias, S. M. Harazim, C. Deneke, S. Sanchez, and O. G. Schmidt, "Self-propellednanotools," ACS nano 6, 1751-1756 (2012). [2] A. Bernardi, A. R. Goni, M. I. Alonso, F. Alsina, H. Scheel, P. O.Vaccaro, and N. Saito, "Probing residual strain in InGaAs/GaAs micro-origami tubes by micro-Raman spectroscopy,"J. Appl. Phys. 99(2006). [3] C. Deneke, N.-Y. Jin-Phillipp, I. Loa, and O. G. Schmidt, "Radial superlattices and singlenanoreactors," Applied Physics Letters 84, 4475-4477 (2004).

Figure 1:Raman spectroscopy and imaging of pristine, defect-rich and cone-like rolled-up GaAs/InGaAs microtubes

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TuP2-26 | Performance enhancement of InP based quantumwell infrared photodetectors via the incorporation of a photoniccrystal structure (#496)Juan Pablo Vasco 1, Wesller Schmidt2, Paulo Sergio Soares Guimaraes1,Wagner Rodrigues1, Weber Hanry Morais Feu1, Rudy Massami Kawabata3,Mauricio Pamplona Pires4, Patricia Lustoza De Souza3

1Universidade Federal de Minas Gerais Departamento de Fisica, Av. AntonioCarlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil 2Universidade Federal de Minas Gerais Centro Microscopia, Belo Horizonte,Minas Gerais, Brazil 3Pontificia Universidade Catolica LabSem-CETUC, Rio de Janeiro, Rio deJaneiro, Brazil 4Universidade Federal do Rio de Janeiro Instituto de Fisica, Rio de Janeiro, Riode Janeiro, Brazil ContentQuantum well infrared photodetectors (QWIPs) are an interesting alternative forselective detection in the mid-infrared frequency range. One problem of a QWIPdetector is the fact that it is not sensitive to incident radiation that is orthogonal tothe surface of the detector, i.e, perpendicular to the quantum well layers, sincethe intraband transitions which are responsible for the detection couple only tothe component of the electric field perpendicular to the quantum wells. Commonsolutions for this problem are to introduce a diffraction grating to scatter theincident radiation or to arrange for oblique incidence. We propose a differentapproach: insert the active region of the detector, i.e., the quantum wells, inside aphotonic crystal slab optimized for the desired detection wavelength. Additionally,the absorption of the infrared radiation is, consequently, enhanced through aresonant coupling with the photonic crystal slab (PCS) modes. In this work, wepresent a comparison between the performances of a quantum well infraredphotodetector (QWIP) which is fabricated as a photonic crystal slab and QWIPswith diffraction grating coupling. The QWIP layer sequence is grown on an InPsubstrate on top of a 500 nm thick InGaAs buffer layer. The active regionconsists of 50 periods of alternating InGaAs/InAlAs layers of 3 nm and 30 nmthicknesses, respectively. Finally, a 500 nm thick InGaAs top contact layer isgrown. All layers are lattice matched to the InP substrate. Standard Au/Ge ohmiccontacts are fabricated on the top and on the side of the lithographically definedmesas. This QWIP system is designed to be illuminated from the bottom, fordetection at a wavelength of 4.1 µm. A numerical optimization of the PCSperiodic pattern is carried out, in order to obtain a resonant coupling between thePCS modes and the QWIP system. The quality factor of the PCS resonance andits relation with the PCS-QWIP efficiency are also investigated. The calculationswere performed using a Finite Difference – Time Domain (FDTD) algorithm and aplane wave expansion method. Our results demonstrate that the incorporation ofQWIP systems in a photonic crystal structure is an interesting alternative forseveral applications.

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TuP2-27 | Modulation of the inter-cavity refractive index as away to control the coupling between two photonic crystalcavities (#497)Juan Pablo Vasco 1, Paulo Sergio Soares Guimaraes1, Marcelo Franca Santos1,Herbert Vinck Posada2

1Universidade Federal de Minas Gerais Departamento de Fisica, Av. AntonioCarlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil 2Universidad Nacional Departamento de Fisica, Bogota, Colombia ContentThe information transfer between two physical systems through a dissipationchannel is a very important topic in the design of optoelectronic devices. Thealteration of mechanisms that govern these channels and their possible controlwill condition the amount of information that is carried from one system toanother. One interesting system for implementation of information transfer is astructure consisting of two coupled photonic crystal cavities fabricated on asemiconductor material. In this case, the control of the coupling, seen as aconsequence of dissipative phenomena, can be made through smallmodifications of material properties such as the dielectric function of the regionbetween the two cavities. In this work we perform a study of the couplingbetween two L3 cavities in a two-dimensional photonic crystal, consisting of airholes in a GaAs material, with hexagonal network. A L3 cavity consists of threeholes missing in a line. A Gaussian modulation of the refractive index in thecentral region between the cavities is introduced into the system with the purposeof simulating a high power laser spot. We find that the fundamental modes canbe strongly coupled, while the excited modes are decoupled. We also report theinverse behavior. The degree of coupling can be controlled through theparameters of the Gaussian modulation, and is quantified by the frequencysplitting of the coupled modes and by the Poynting vector flux between thecavities.

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TuP2-28 | Can the exciton-polariton regime be defined bypurely quantum properties? (#506)G. Cipagauta1, D. G. Suárez-Forero1, H. Vinck-Posada1, K. M. Fonseca1, R. R. Rey-González1, W. Herrera2

1Universidad Nacional de Colombia - Bogotá Facultad de Ciencias,Departamento de Física, Grupo de Óptica e Información Cuántica, Carrera 30Calle 45-03, C. P. 111321 Bogotá, Colombia 2Universidad Nacional de Colombia - Bogotá Facultad de Ciencias,Departamento de Física, Superconductividad y Nanotecnología, Carrera 30Calle 45-03, C. P. 111321 Bogotá, Colombia ContentCurrent experiments in semiconductor microcavities reveal different regimes inthe photoluminescence properties of the matter-light interacting system. Weattempt to give a full quantum-mechanical explanation of them. To do this, thematter-light system is modelled by a master equation whose unitary dynamicsfollows from a Dicke Hamiltonian. The system density operator is calculated forsingle and multiple radiators. Our results, which allow us to qualitativelyestablish the thresholds between the regimes, show that polariton and photonlaser regimes critically depend on the quantum state of the system, as describedby entanglement and mixedness, and by the second and third order correlationfunctions of emitted light.

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TuP2-29 | Towards dynamic strain tuning of quantum dotexcitons using Fourier synthesized acoustic pulses (#273)F. J. R. Schülein 1, Eugenio Zallo2, Paola Atkinson2, Armando Rastelli2, O. G.Schmidt2, Achim Wixforth1, Hubert J. Krenner1

1Universität Augsburg Lehrstuhl für Experimentalphysik 1, Universitätsstr. 1,86159 Augsburg, Germany 2IFW Dresden Institut für Integrative Nanowissenschaften, Helmholtzstraße 20,01171 Dresden, Germany ContentHere, we report on the dynamic modulation of the photoluminescence (PL)emission energy of individual GaAs/AlGaAs quantum dot (QD) excitons by thestrain field of a surface acoustic wave (SAW). By superimposing two independentwaveforms, we show that this Fourier synthesis reflects itself directly in themeasured emission energy modulation. For our experiments, we use strain-freeGaAs/AlGaAs QDs grown by solid source molecular beam epitaxy [1]. We excitecharge carriers into the WL by picosecond laser pulses of variable repetition rate.The SAW frequency and laser repetition rate are chosen to be harmonics,therefore, we are able to stroboscopically probe the QD emission over two fullcycles of the SAW by adjusting the relative phase between excitation pulse andSAW [2]. In Fig. 1(a), we present typical emission spectra of a single QD which isdynamically modulated by the SAW over two cycles for a frequency of fSAW =144.8 MHz. The extracted emission energy, plotted as symbols in Fig. 1(b),follows the sinusoidal modulation of the SAW, as indicated by the fitted line. Forthe applied SAW power level of 23 dBm, we measure a total modulationbandwidth ∆E = 200 µeV. Since the modulation is symmetric and matches exactlythe periodicity of the SAW, we conclude that the underlying mechanism is adynamic modulation of the deformation potential coupling of the QD to the SAWstrain field [3]. The strain fields as uniform at a given time since λSAW = 20 µm issignificantly larger than the QD size. Using this acoustic technique, we achievedmodulation bandwidths exceeding 1000 µeV at SAW frequencies of 560 MHz.Finally, we combine two independent SAWs to Fourier synthesize a nano-mechanical square wave. We use the fundamental SAW frequency (144.8 MHz)and the third harmonic (434.4 MHz), plotted as solid lines in Fig. 2(a). Themeasured SAW signal plotted as symbols in Fig. 2(a) confirms the Fouriersynthesis. The experimental data of the QD exciton emission energy as afunction of time is plotted as symbols in Fig. 2(b). The measured modulation witha bandwidth of ~380 µeV can be nicely reproduced by fitting the synthesizedwaveform (line). This proof-of-principle experiment demonstrates that Fouriersynthesis of SAWs can be applied to generate tailored nanomechanical strainpulses at radio frequencies. References[1] S. Kumar et al. APL 99, 161118 (2011) ; P. Atkinson et al. (2012) [2] S. Völk et al., APL 98, 023109 (2011) [3] F.Ding et al., PRL 104, 067405 (2010)

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Figure 1:(a) Falsecolor plot of the time evolution of a single QD PL emission over two SAW cycles. (b) Extractedrelative energy shift of the QD exciton (symbols) and sinusoidal fit to the data (line).

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Figure 2:(a) Transmitted SAW signal (symbols), reproducing the waveform (black) synthesized from two SAWs(light and dark blue lines. (b) Extracted energy shift of the QD exciton (symbols) and fitted waveform (line).

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TuP2-30 | High Efficiency Integrated Optical Sensor with < 0.5VBias Voltage in Standard CMOS Technology (#539)Yuh-Hui Lai National Central University Department of Optics and Photonics, No. 26,Prosperity Road I,, Hsinchu, Hsinchu 30078, Taiwan ContentSummary: In this study, fully compatible to standard CMOS process, a highefficiency integrated optical sensor with <0.5V bias voltage has been realizedand demonstrated. By the optical sensor created in the extended ‘Gate’ region ofstandard MOS, significant 2 order improvement of photo current compared withsimply photodiode, with low bias voltage of 0.25V and floating gate voltage ofMOS simultaneously, are achieved successfully. This device merges excellentoptical performance, while keeping the lower bias and read-out voltage forreducing power consumption. The proposed strategy offers high potential forseveral kinds of visible applications, such as ambiance detection. Motivation:Recently, a market that uses ambient light detectors started to grow. Low costremains a requirement and the possibility of integrating photodetectors [1]-[5]with other circuits becomes even more attractive. Generally, the higher powerconsumption of peripherally circuit is, the more significant amplification of opticalsignal becomes. For utilizing the energy effectively, while keeping the reasonablephoto current output and low cost requirement, the integrated optical sensorshould be proposed for these purposes. References[1] L.D. Garrett, J. Qi, C.L. Schow and J.C. Campbell: Trans. Electron Devices, vol.43(1996), p. 411 [2] M. Yang, K.Rim, D.L. Rogers, J.D. Schaub, J.J. Welser, D M. Kuchta, D.C. Boyd, F. Rodier, P. A. Rabidoux, J.T. Marsh, A.D.Ticknor, Q. Yang, A. Upham and S. C. Ramac: Electron Device Letters, vol. 23, (2002), p. 395. [3] M. Jutzi, M.Grozing, E. Gaugler, W. Mazioschek and M. Berroth: Photonics Technology Letters, vol. 17, (2005), p. 1268. [4] A.Nemecek, G. Zach, R. Swoboda, K. Oberhauser and H. Zimmermann: Journal of Selected Topics in QuantumElectronic, vol. 12, (2006), p. 1469. [5] T. Yin, A.M. Pappu and A.B. Apsel: Photonics Technology Letters, vol. 18,(2006), p. 55.

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TuP3-1 | Displacing, squeezing, and time evolution of quantumstates for nanoelectronic circuits (#18)Jeong Ryeol Choi 1, Kyu Hwang Yeon2, Byeong Jae Choi3, Hyun Deok Kim4,Mustapha Maamache5

1Daegu Health College, Department of Radiologic Technology, Taejeon 1-dong,Buk-gu, Daegu 702-722, Korea Republic (South)2Chungbuk National University Department of Physics, Cheongju 361-763, KoreaRepublic (South)3Daegu University Department of Technology of Communication, Kyeongsan712-714, Korea Republic (South)4Kyungpook National University Division of Semiconductor and DisplayEngineering, Daegu 702-701, Korea Republic (South)5University of Setif Department of Physics, 19000 Setif, Algeria ContentNot only quantum dots and quantum lines but also integrated electronic circuitsinvolving nanoscale elements are important in nanometer electronics andquantum information technology. We investigate quantum characteristics of atwo-dimensional nanoelectronic circuit driven by a time-varying power source inthe displaced squeezed number state (DSNS) [1]. The unitary transformationmethod which is very useful when treating time-dependent Hamiltonian systemsin cases like this is used here. The statistical properties of these states exhibitseveral pure quantum effects which have no classical analogues, such asinterferences in the phase space [2], the revival/collapse phenomenon [3], andsub-Poissonian statistics [4]. We consider two loops of RLC circuit whoseelements are nanosize, that are mutually coupled via inductance and resistanceas shown in Fig. 1. Using Kirchhoff’s law, we obtain the classical equations ofmotion for charges of the circuits. From basic Hamiltonian dynamics, the exactwave function associated to the DSNS in the system is derived. The timeevolution of the corresponding probability density is investigated. From Fig. 2, wesee that the trajectory of probability density in the DSNS is significantly distortedby the effects of displacing, squeezing, and external power source. If there is nopower source in the circuit, the initial displacement of charges graduallydisappears according to the dissipation given by the resistances in the circuit.This is the same as that interpreted from the classical dynamics. The probabilitydensity in the DSNS oscillates with time due to the initial displacement of thecharges. Moreover it is more or less distorted on account of sinusoidallyvarying signal power source. We confirmed that the overall value of chargefluctuation decreases exponentially with time whereas that of current fluctuationincreases exponentially. References

1. K.B. Moller, T.G. Jorgensen and J.P. Dahl, Phys Rev A, 54, 5378 (1996).2. M.A. Marchiolli, L.F. da Silva, P.S. Melo and C.M.A. Dantas, Physica A, 291, 449 (2001).3. N.B. Narozhny, J.J. Sanchez-Mondragon and J.H. Eberly, Phys Rev A, 23, 236 (1981).4. M.S. Kim, J Mod Opt, 40, 1331 (1993).

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Figure 1 :Diagram of a two-dimensional electronic circuit composed of nanoscale elements

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Figure 2:The probability density: (a) corresponds to ordinary number state [i.e., number state without displacing,squeezing, and power source] and (b) to the DSNS with a sinusoidal power source.

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TuP3-2 | Magnetotransport in a GaPSb nanofilm (#64)H. E. Lin1, S.-W. Wang1, Shun-Tsung Lo 2, Huang-De Lin1, Yu-Chung Chin3, Hao-Hsiung Lin3,4, Jheng-Cyuan Lin1, C.-T. Liang1,2

1National Taiwan University Department of Physics, No. 1, Sec. 4, RooseveltRoad, Taipei 106, Taiwan 2National Taiwan University Graduate Institute of Applied Physics, No. 1, Sec. 4,Roosevelt Road, Taipei 106, Taiwan 3National Taiwan University Graduate Institute of Electronics Engineering, No. 1,Sec. 4, Roosevelt Road, Taipei 106, Taiwan 4National Taiwan University Department of Electrical Engineering, No. 1, Sec. 4,Roosevelt Road, Taipei 106, Taiwan ContentIII-V based alloys and heterostructures have been attracting much interestbecause of their great device applications as well as their fundamentalimportance. A major issue of composing III-V-based systems is the miscibilitygap in the solid [1]. It is known that the mixing enthalpy of the systems, such asGaAs-GaSb and GaP-GaSb, is proportional to the square of the difference inlattice constant of the two end binary components of the system [2]. This reasonprohibits the epitaxial growth of most alloys at ordinary growth temperatures [3].Therefore, the epitaxial growth of these systems was not achieved until the firstgrowth of GaAs-GaSb, was done in 1979 by carrying out the growth under ahigh-supersaturation condition, such as MBE [4]. The ternary alloy, galliumphosphide antimonide (GaP1-xSbx), was grown on GaAs for the first time in 1988[5]. Since then, there has been a lack of work on gallium phosphide antimonideas well as transport behavior in such a material. In this work, we report extensivemagneto-transport studies of a GaPSb film grown on GaAs substrate. Such adevice is fully compatible with the existing GaAs-based high electron mobilitytransistor (HEMT) technology. Moreover, the GaPSb-based system may well beof great device applications in heterojunction biopolar transistor (HBT), high-power devices and nanoelectronics. Our GaPSb film always shows insulatingbehavior in the sense that the resistance decreases with increasing thetemperature as shown in Fig. 1. We show that in the low temperature regime 4.7K T 31 K, electron transport follows Mott variable range hopping (VRH). For34 K T 48 K, the dominant conduction behavior is probably in the manner ofnearest-neighbor hopping. For T > 49 K, our data shows agreement with thethermally-activated behavior with a gap of 8.8 meV. The carrier densitydetermined from the Hall effect also supports this picture [6]. As shown in Fig. 2,negative magnetoresistance and subsequent positive magnetoresistance areobserved. This interesting behavior is consistent with the interference model andthe shrinkage of the wave function at high fields. Our new experimental resultsmay provide useful information regarding the electrical properties of GaPSb aswell as it device applications.

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ReferencesReferences [1] G. B. Stringfellow, J. Cryst. Growth 58, 194 (1982). [2] G. B. Stringfellow, J. Cryst. Growth 27, 21(1974). [3] J. Pessetto and G. B. Stringfellow, J. Cryst. Growth 62, 1 (1983). [4] J. Waho, S. Ogawa, and S.Maruyama, Jpn. J. Appl. Phys.16, 1875 (1979). [5] M. J. Jou, Y. T. Chern, H. R. Jen, and G. B. Stringfellow, Appl.Phys. Lett. 52, 549 (1988). [6] S.-T. Lo, K. Y. Chen, Y.-C. Su, C.-T. Liang, Y. H. Chang, G.-H. Kim, J.-Y. Wu, and S.-D. Lin, Solid State Commun. 150, 1104 (2010).

Fig. 1:Resistance as a function of temperature.

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Fig. 2:Magnetoresistance as a function of magnetic field B at various temperatures T.

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TuP3-3 | QUASISTATATIONARY STATES IN SINGLE ANDCOUPLED GaAs-(Ga,Al)As QUANTUM WELLS UNDER THEACTION OF HYDROSTATIC PRESSURE AND APPLIEDELECTRIC FIELDS (#68)Ana Schönhöbel, Jaime Girón, Nelson Porras-Montenegro universidad del valle Física, calle 13 # 100-00, cali, Colombia ContentSemiconductor low dimensional systems are of great interest for theunderstanding of basic physics phenomena as well as for the development ofoptoelectronic devices. There have been several works devoted to theunderstanding the role of the applied electric field and hydrostatic pressure onthe electron states in these structures. [1-4]. In some works authors have treatedapproximately the behavior of the wave function as an exponential decayingexpression in the barrier region [1, 2]. In the present work, we have studied theeffects of hydrostatic pressure and uniform electric field on the electron and holequasistationary energy levels in GaAs-(Ga,Al)As single (QWs) and doublequantum wells (DQWs). Theoretical calculations are performed by using theEnderlein’s method [5, 6] to solve exactly the Schrödinger equation. Numericalresults are obtained as a function of the applied electric field, hydrostaticpressure, Al concentration, and the structure geometry as well. We have foundthe anti-crossing phenomenon for a specific electric field between the first andsecond quasistationary energy levels. Additionally, we have analyzed the limitwhen the height of the central barrier of the DQWs tends to zero, that is, the caseof a single quantum well. In such a limit, we have distinguished three regions:confinement, resonant and pulsations; quasistationary states become resonantstates with increasing the electric field, while the opposite happens with the wellwidth or the aluminum concentration. We have found that the electron, light andheavy hole energy levels diminish in a wide range of applied hydrostaticpressure. Above the barrier energy pulsations are observed in the density ofstates, through a modulated frequency, which basically does not depend eitheron the Al concentration or on the applied electric field, whereas the fastfrequency increases with pressure and diminishes with the applied electric field,irrespective of the geometry and Al concentration. References[1] J. López-Gondar et al. Phys.Rev.B 42, 7069 (1990) [2] E. Reyes-Gómez et al, Physica B 367, 267 (2005). [3] A.Montes et al, Phys. Rev. B 61, 9936 (2000). [4] N. Porras-Montenegro et al, J. Phys. Condens. Matter 20, 465220(2008). [5] R. Enderlein, Phys. Rev. B 42, 4708 (1990). [6] W. Trzeciakowski, Phys. Rev. B 44, 3880 (1990).

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Fig.1:Density of states of a GaAs-GaAl0.3As0.7 QWs as a function of energy, with F=100kV/cm and L=20nm.

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TuP3-4 | Electronic transmittance phase extracted frommesoscopic interferometers (#130)Mugurel Tolea 1, Valeriu Moldoveanu1, Ion Viorel Dinu1, Bilal Tanatar2

1National Institute of Materials Physics, 77125 Bucharest-Magurele, Romania 2Bilkent University Department of Physics, 06800 Bilkent, Ankara, Turkey ContentThe usual experimental set-up for measuring the wave function phase shift ofelectrons tunneling through a quantum dot (QD) embedded in a ring (i.e. the thetransmittance phase) is the so-called "open" interferometer [R. Schuster et al.,Nature (London) 385, 417 (1997)], in which the electrons back-scattered atsource and drain contacts are absorbed by additional leads in order to excludemultiple interference. While in this case one can use a simple two-pathinterference formula to extract the QD phase, the open interferometer has areduced signal and the effects of the extra leads are difficult to control. Here wepresent a theoretical study of the QD transmittance phase in "closed"interferometers (i.e. connected only to source and drain leads). By puttingtogether data from existing literature and presenting some new proofs we showboth analitically and by numerical simulations that the existence of phase lapsesbetween consecutive resonances is related to the signs of the corespondingFano parameters. More precisely, if the Fano parameters have the same sign,the transmittance phase of the QD exhibits a π lapse. Therefore, closedmesoscopic interferometers can be used to address the "universal phase lapse"problem. Moreover, the data from Fano interference experiments [e.g. K.Kobayashi et al., Phys. Rev. B 68, 235304 (2003)] can be used to infer on phaselapses. In the presence of the electron-electron interaction, the phasemeasurement problem is also carefully formulated and some results arepresented on a simple model.

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TuP3-5 | Talking through the Continuum: A Robust Scheme forCoupling Quantum States (#192)Youngsoo Yoon1, Fransson Jonas2, Kang Myoung-Gu1, Shiran Xiao1, NobuyukiAoki3, Reno John4, Yuichi Ochiai 3, Mourokh Lev5, Jonathan P. Bird1,3

1University at Buffalo Electrical Engineering, Buffalo, NY 14260, United States2Uppsala University Physics, SE-751 21 Uppsala, Sweden3Chiba University Graduate School of Advanced Integration Science, 1-33 Yayoi-cho, Inage-ku, Chiba, Chiba 263-8522, Japan 4Sandia National Laboratories CINT Science Department, Albuquerque, NM87185-1303, United States5Queens College of CUNY Physics, Flushing, NY 11367, United States ContentCoupling quantum states to achieve novel functionality is a central theme ofnanotechnology. In developing coupling schemes, one usually seeks to minimizethe influence on the system of the external environment, due to its tendency tocause decoherence. Here we show, however, a novel scheme for couplingquantum states that results in a robust interaction between them, by utilizing,rather than avoiding, the external environment. We achieve this by exploitingnanoscale quantum point contacts (QPCs) as an “on-demand” source ofquantum states. By varying the gate voltage that induces their electrostaticconfinement. QPCs can be driven into the limit where only a few electrons arepresent inside them. Experiments in this regime reveal anomalous electricalbehavior that has been attributed to the strong many-body interactions ofelectrons that pile-up around the QPC. These interactions are predicted to inducea naturally-formed “quantum dot” within the QPC, with an associated bound state(BS) that supports just a single electron. Recently, we have provided evidencefor electrical detection of this BS by coupling a pair of QPCs via a region ofmutual two-dimensional electron gas that serves as a continuum. By forming theBS in one of these devices, a clear Fano resonance is observed in the other,which serves as a detector. In this presentation, we take this capability one stepfurther by configuring a pair of BSs on two separate QPCs and allowing them tointeract with each other through a mutual continuum. By using a third QPC as adetector we then observe a novel multi-state Fano resonance due to theinteraction of the two BSs. To explain this result, we develop a theoreticalformulation that attributes the robust character of the interaction between the twoBSs to the fact that it is mediated by a large number of degenerate continuumstates. Work supported by the Department of Energy (DE-FG03-01ER45920)and performed, in part, at the Center for Integrated Nanotechnologies, a U.S.DOE, Office of Basic Energy Sciences nanoscale science research center.Sandia National Laboratories is a multi-program laboratory operated by SandiaCorporation, a Lockheed-Martin Company, for the U. S. Department of Energyunder Contract No. DE-AC04-94AL85000. JF thanks the Swedish ResearchCouncil for support.

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ReferencesJ. P. Bird and Y. Ochiai, Science 303, 1621 (2004). Y. Yoon et al., Phys. Rev. Lett. 99, 136805 (2007). Y. Yoon et al.,Phys. Rev. B 79, 121304(R) (2009). Y. Yoon et al., Phys. Rev. X, in press (2012).

Figure:Supporting figures for abstract

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TuP3-6 | Temperature Dependence of the PersistentPhotoconductivity in SnO2 Nanobelts (#211)Emilson Ribeiro Viana Junior , Geraldo Mathias Ribeiro, Juan Carlos González,Alfredo Gontijo de OliveiraUniversidade Federal de Minas Gerais Physics Department, Av. Pres. AntônioCarlos, 6627, Belo Horizonte, MG, 31270-901, Brazil ContentAn individual tin oxide (SnO2) nanobelt was connected in a two-probeconfiguration, and the photoconductivity was studied. Under ultraviolet (UV)illumination, and for temperatures measured in the range 400 to 250K wereobserved that the maximum induced photocurrent increases with a decrease intemperature, and when the UV illumination is turned off, the photocurrent decayvery slowly to a constant value and persists for several hours. So the PersistentPhotoconductivity (PPC) effect was observed for the first time in a SnO2

nanobelt. In order to quantify this PPC effect, the photocurrent decay was fittedby two exponentials, obtaining two different carrier lifetimes t1 and t2. For eachtemperature measured, t1 and t2 were determined, and since we have t2 >> t1, t2

was the parameter used to quantify the PPC effect. From the analysis of t2, adeep energy-trap were estimated approximately 170meV, and this deep-energyobtained is consistent with the theory, since is high if comparable with theactivation energy of the conductivity for the n-type carriers, and with the kineticenergy at the range of temperatures measured.

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TuP3-7 | Current and Shot noise in DNA chains (#220)Judith Ojeda1, Monica Pacheco2, Luis Rosales 2, Pedro Orellana3

1Universidad Pedagógica y Tecnológica de Colombia Departamento de Física,Tunja, Colombia 2Universidad Técnica Federico Santa María Departamento de Física, AvenidaEspaña 1680, 110V Valparaíso, Chile 3Universidad Católica del Norte Departamento de Física, Antofagasta, Chile ContentTransport properties of DNA molecules is still an interesting issue, due to thediversity of electronic behaviours reported by experimental studies. Thosereports show that depending on the type of the considered systems, the DNAmolecules behave as superconducting [1], metal [2], semiconductor [3] orinsulator [4]. Transport in DNA molecules can be considered as discrete jumpsbetween pairs of nucleotide bases. The two strands representing the double helixstructure of DNA form two channels of propagation of the electrons [5], which canbe controlled by applying gate voltages over the molecules. The current passingthrough these molecular systems is a non linear function of the applied voltages,and therefore, it is possible to observe quantum fluctuations in the transportproperties of DNA systems. In the absence of scattering processes, thesefluctuations are known as the noise power spectrum which, in a steady state, isdescribed by the Shot noise. The noise power provides an important informationabout the electronic correlation by means of the Fano factor (F), which indicateswhether the magnitude of the noise reaches a Poisson (F = 1) or sub-poisson (F< 1) limits [6]. In this work we propose a semi-analytic method for the calculationof the transport properties of DNA molecules. By using a nearest neighbour tightbinding Hamiltonian and based on the Green’s function formalisms, wecalculated the transmission probability, the I-V characteristics, the Shot noise andthe Fano factor of molecules composed by homogeneous segments of pairs ofbasis poly(G) and poly(C), connected to two semi-infinities metallic contacts. Todescribe these molecules we have adopted the Fishbone and the Laddermodel . Both representations consider the DNA molecules as a planar structurescomposed by N unit cells coupling to the leads. By applying real-spacerenormalization techniques, we obtain one-dimensional effective models forwhich we analytically determined the transmission coefficients [7]. With thisexpression, we numerically calculate the I-V characteristics, the Shot noise andthe Fano factor, reducing efficiently the computational time of calculus. We havefocused our analysis in the modulations of the transport properties as a functionof the intrasite and the DNA-leads coupling potentials. Our results show differentelectronic behaviours as a function of the coupling intensities, exhibitingtransitions between metal and semiconductor regimes [8]. References[1] A. Yu. Kasumov, et al., Science 280, 291 (2001). [2] O. Legrand, et. al., Phys. Rev. E 73, 031925 (2006). [3] D.Porath, et. all., Nature, 403, 635 (2000). [4] E. Braun, et. al., Nature 391, 775 (1998). [5] V. Bagci, et. al, Chaos,Solitons and Fractals 34 104 (2007). [6] Y. M. Blanter, M. Buttiker, Phys Rep 1, 336 (2000). [7] S. Roche, Phys. Rev.Lett. 91, 108101 (2003). [8] J. Ojeda, M. Pacheco, L. Rosales, and P. A. Orellana, Organic Electronics, in press(2012)

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TuP3-8 | Transport properties of two finite armchairnanoribbons (#231)Luis Rosales 1, Jhon González2

1Universidad Técnica Federico Santa María Departamento de Física, AvenidaEspaña 1680, 110V Valparaíso, Chile 2International Iberian Nanotechnology Laboratory, Av Mestre josé Veiga4715-330, Braga, Portugal ContentGraphene nanoribbons (GNRs) are quasi one-dimensional systems based ongraphene which can be obtained by different experimental techniques [1]. Theelectronic behaviour of these nanostructures is determined by their geometricconfinement which allows the observation of quantum effects. The controlledmanipulation of these effects, by applying external perturbations to thenanostructures or by modifying the geometrical confinement, could be used todevelop new technological applications [2] In this work we present a theoreticalstudy of the transport properties of a heterostructure composed by two parallelan finite armchair graphene nanoribbons (A- GNRs) of widths Nd and Nu andlength L, connected to two semi-infinite lead made of the same material. Aschematic view of a considered system is shown in Fig.1. We have focused ouranalysis on the electronic transport modulations due to the geometricconfinement and the presence of external perturbations. We have studied thetransport response due to variations in the length and width of the centralribbons, considering symmetric and asymmetric configurations. On the otherhand, we have considered two independent external potentials: i) The interactionwith two gate potentials applied independently to each ribbon of the conductor,which allow to control the symmetry or asymmetry of the transverse levels withinthe conductor and, ii) The interaction of electrons with an uniform externalmagnetic field applied perpendicular to the heterostructure. We have obtainedperiodic modulations of the transport properties as a function of these twoexternal perturbations. The gate voltages produce modulations of the energygap of the systems, giving the possibility of control the transport response. This ismore evident in the I-V characteristics and in the behaviour of the differentialconductance curves, where negative values are obtained at low bias voltages. Inthe case of the magnetic field interaction, we have observed a completeAharonov-Bohm type of modulation as a function of the magnetic flux. Thisrobust effect, is observed even when the two A-GNRs have different widths, andconsequently, different transverse electronic states. Besides, the magnetic fieldgenerates a periodic metal -semiconductor transition of the conductor, which canbe used in electronics applications [3] References[1] X. Li, X. Wang, et. al. Science 319, 1229 (2008). [2] B. Oezyilmaz, et al., Phys. Rev. Lett. 99, 166804 (2007). [3] L.Rosales and J. W. González, submitted to Physical Review B, (2012)

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Figure 1:Schematic view of the conductor. The length L of the conductor is measured in unitary-cells units.

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TuP3-9 | Spin-dependent electron scattering and transportthrough charged quantum dots in a quasi-one-dimensionalsemiconductor nanostructure (#239)Leonardo K. Castelano1, Guo-Qiang Hai 2, Mu-Tao Lee3

1Universidade Federal de São Carlos Departamento de Física, São Carlos, SP,13565-905, Brazil 2Universidade de São Paulo Instituto de Física de São Carlos, Av. TrabalhadorSãocarlense 400, São Carlos, SP, 13560-970, Brazil 3Universidade Federal de São Carlos Departamento de Química, São Carlos,SP, 13565-905, Brazil ContentElectron scattering and transport through quantum dots (QDs) have beenintensively studied. The spin-dependent transport is related to some possibleapplications such as the QD spin valves and the quantum logic gates usingcoupled QDs. A thorough quantitative understanding of spin-dependent transportproperties due to e-e interaction through QDs in a semiconductor nanostructureis therefore of particular interest. In a previous paper[1], we developed atheoretical method to study electron scattering through a QD of N-electrons in atwo-dimensional (2D) semiconductor structure. The generalized Lippmann-Schwinger (LS) equations were solved in 2D systems by using the method ofcontinued fractions (MCF). In this work, we construct the scattering equations fora free electron injecting into and scattered by a charged QD confined in a quasi-one-dimensional (Q1D) semiconductor nanostructure. The MCF is applied tosolve the LS equation in this system. The convergency of the MCF is veryaccurate in this case and achieves a precision of 10−4 for the conductance inabout 20 interactions. Our results show that the e-e exchange potential splits theresonant transport peak into two. When the spin state of the incident andconfined electrons is singlet (triplet), the transmission probability is enhanced(suppressed). Fig. 1 shows the transmission probability through a QD containingone electron as a function of the incident electron energy (for the QD of size 90nm with a finite parabolic potential of ħωx =5 meV; the potential for the Q1Dchannel is an infinite parabolic one in the y-direction with ωy=1.7ωx). Thedashed (solid) curve is for the incident and QD electron being of anti-parallel(parallel) spin. The results due to the QD potential only (dotted curve) and due tothe static potential (dash-dotted curve) are also plotted in the figure. Furthermore,we study the multi-channel scattering arising from the multi-levels in the QD andthe inelastic scattering in which the scattering leaves the QD in an excited state.Finally, we present our calculations for two-coupled QDs with bonding andantibonding states. (This work was supported by FAPESP and CNPq, Brazil). References[1] ] L. K. Castelano, G.-Q. Hai, and M.-T. Lee, Phys. Rev. B 76, 165306 (2007).

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Fig. 1:The electron transmission probability through a one-electron QD in a Q1D structure

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TuP3-10 | Magnetic nanoparticles induced dielectricenhancement in (La, Gd)2O3 : SiO2 nano-glass compositesystems (#244)T. H. Kao , S. Mukherjee, C. C. Chou, H. D. YangNational Sun Yat-Sen University Department of Physics, No. 70, Lienhai Rd.,Kaohsiung 80424, Taiwan ContentMagnetic Gd2O3 and non-magnetic La2O3 nanoparticles (NPs) have beensynthesized together with different doping concentrations in SiO2 matrix via sol-gel route calcination at 700 oC and above. Properly annealed nano-glasscomposite systems show enhancement of dielectric constant andmagnetodielectric effect (MDE) near room temperature, depending on magneticNPs concentration. The thermal behavior of magnetization (zero-field-cooled andfield-cooled) and magnetic hysteresis of Gd2O3 NPs in the 2–360 K temperatureinterval have demonstrated that the Gd2O3 NPs present in these glasses displaysuperparamagnetic–ferromagnetic transition at low temperatures. The radialdistribution functions, reconstructed from extended x-ray absorption fine structure(EXAFS), show shortening of RE3+-O (RE~ La, Gd) depending on the RE2O3 NPssize which is consistent with oxygen vacancy induced dielectric anomaly. Thehigh-k and MDE of these nano-glass composite systems are very muchconditional by magnetic property of Gd2O3 NPs, concentrations of magnetic ions,and the degree of deformation of the host matrix.

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TuP3-11 | A study of magnetodielectric effects in magneticMnO: SiO2 nano-glass composite system (#245)S. Mukherjee 1, H. D. Yang1, A. K. Pal21National Sun Yat-Sen University Department of Physics, No. 70, Lienhai Rd.,Kaohsiung 80424, Taiwan 2Indian Association for the Cultivation of Science Department of Solid StatePhysics, Jadavpur, West Bengal, Kolkata 700032, India ContentMagnetic nanoparticles (NPs) of 0.1 mol% MnO doped in silica glass samplesprepared by a sol–gel method followed by calcination at various temperatures upto 1000 oC are studied by x-ray diffraction (XRD), transmission electronmicroscopy (TEM), dielectric spectroscopy and magnetic methods, includingelectron paramagnetic resonance (EPR). XRD and TEM of sample calcined at1000 oC shows the presence of NPs of MnO having orthorhombic crystallinephase and sizes about 10 nm. The thermal behavior of magnetization (zero-field-cooled and field-cooled) and magnetic hysteresis of MnO NPs in the 5–300 Ktemperature interval have demonstrated that the MnO NPs displaysuperparamagnetic–ferromagnetic transition at low temperatures. An intriguingcolossal enhancement of dielectric constant with distinct anomalies coincidingwith the magnetic blocking temperature and significant magnetodielectric withthermal hysteresis effect is observed near the transition temperature. X-bandEPR linewidth data plotted versus inverse of temperature (1/T) for samplescalcined at 900 and 1000 oC (EPR recorded in the vicinity of 0.35 tesla appliedfield) depict similar transitions.

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TuP3-12 | Controlling the shot noise in a quantum dot coupledto a side quantum ring (#247)Victor Apel1, Monica Pacheco2, Enrique Anda3, Pedro Orellana 1

1Universidad Católica del Norte Physics, Avenida Angamos, 0610 Antofagasta,Chile 2Universidad Federico Santa Maria Physics, Avenida España, 1680 Valparaiso,Chile 3Pontificia Universidad Católica de Rio de Janeiro Physics, Rio de Janeiro, Riode Janeiro, Rio de Janeiro, 22453, Brazil ContentThe electronics transport through quantum dots (QDs) has been extensivelystudied in the last decade [1,2]. The QDs allow studying systematically quantum-coherent effects as Kondo, Fano and Aharonov-Bohm effects, due to thepossibility of continuous tuning the relevant parameters governing the propertiesof these resonances, in equilibrium and nonequilibrium situations. The Kondoresonance is accessible in electronic transport experiments, as it opens anadditional transport channel, which is readily seen in the differential conductanceof these structures (typically in the zero-bias limit). In these configurationelectrons transmitted from one electrode to the other necessarily pass throughthe QD. It is presently known that a quantum dot with a side attached quantumring exhibits the electronic counterpart of the Fano effect [3], and that they can becontrolled by the magnetic flux through the ring. Present understanding ofelectron transport properties of quantum dots is based mainly on direct transportexperiments. However, additional information can be obtained from noisemeasurements. Electronic current through any conductor fluctuates with time andmanifests the consequence of charge granularity, which is referred to a shotnoise in the literature. It has been demonstrated that electron shot noise providesa useful tool to detect coherence in quantum dots, as well as it give insight on therole of electron coherence and Coulomb interactions in electronic transport. Itfurther provides information about current fluctuations that cannot be extractedfrom the average current alone. For instance, shot noise experiments candetermine the kinetics of electrons, and give information on the correlation of theelectronic wave function. In the present work we investigate the transportproperties of strongly correlated quantum dot in Kondo regime attached to twoleads and side coupled to a quantum-ring under a magnetic flux as shown in Fig.1. We show that the differential conductance develops a sequences of Fanoantiresonances as a consequence of destructive interferences of N discretequantum ring levels with a continuous conducting channels. The interactiondetermines the Fano antiresonance shape, in the U-infinity limit the Fanoantiresonances are asymmetric while in the case without interaction (U=0) theyare symmetric. We show that the shot noise and Fano factor can be controlled bythe magnetic flux in the quantum ring.

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References[1 ] D.Goldhaber-Gordon, H.~Shtrikman, D.Mahalu,D.Abusch-Magder, U.Meirav, M.A.Kastner, Nature 391, 156(1998); D.Goldhaber-Gordon, J.Göres, M.A.Kastner, H.Shtrikman, D.Mahalu, U.Meirav, Phys. Rev. Lett. 81, 5225(1998). [2] U. Fano, Phys. Rev. 124, 1866 (1961), Kensuke Kobayashi, Hisashi Aikawa, Shingo Katsumoto, andYasuhiro Iye Phys. Rev. Lett. 88, 256806 (2002). [3] Ya M Blanter and M. Büttiker, Phys. Rep. 336, 1 (2000). [4] P. A.Orellana, M. L. Ladrón de Guevara,M. Pacheco, and A. Latgé Phys. Rev. B 68, 195321 (2003).

Figure 1:Quantum dot connected to two leads with a side coupled quantum ring

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TuP3-13 | Enhancement of thermoelectric efficiency due to theFano effect in quantum dots (#330)Maria Loreto Ladrón de Guevara, Oscar Avalos, Guillermo Gómez, Pedro OrellanaUniversidad Católica del Norte Physics, Avenida Angamos, 0610 Antofagasta,Chile ContentIn this article we are concerned with the thermoelectric properties of a double-quantum dot molecule embedded in an Aharonov-Bohm ring as shown in Fig 1.This system is described by a transmission amplitude with two components ofdifferent spectral line-widths, the combination between them giving rise to aconvolution of a Breit-Wigner and a Fano resonance in the transmissionprobability. Liu et al. in Ref [1] studied the thermoelectricity of this systemnumerically both in the absence and in presence of electronic correlations,finding that the figure of merit has a significant increase in the Fano line shaperegime. Our work advances further on the findings of Refs. [1] and [2] presentingan analytical work showing clearly that the enhancement of the thermoelectricefficiency comes from the Fano antiresonances, which are also responsible forthe failure of the Wiedemann-Franz law. In the framework of a noninteractingmodel, we use the Sommerfeld expansion to derive analytical expressions of thethermo-power, the electric and thermal conductances, and the figure of merit.The Fano antiresonances in transmission demand that terms usually discarded inthe Sommerfeld expansion are taken into account. References[1] Y. S. Liu and X. F. Yang, J. Appl. Phys. 108, 023710 (2010). [2] S. Liu, D. B. Zhang, X. F. Yang, and J. F. Feng,Nanotechnology 22, 225201 (2011).

Figure 1:Scheme of the double quantum dot molecule embedded in an Aharonov-Bohm ring.

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TuP4-1 | Extraordinary terahertz absorption bands observed inMicro/Nano-structured metallic/dielectric sphere arrays (#92)Wen Xu 1,2, Guotao Duan1, Fuhai Su1

1Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031,China2Yunnan University Department of Physics, Kunming 650091, China ContentVery recently, extraordinary surface-plasmon-enhanced transmission in terahertz(THz) frequency domain has been extensively investigated in both metallic [1]and semiconductor [2] array structures due to their applications in THzplasmonics. In this work, we examine the THz optoelectronic response of theperiodic Au/dielectric sphere array films deposited on Si substrate. By means ofIon-beam sputtering, the Au sphere arrays with various shell thicknesses anddiameters were produced by depositing the gold onto the Si substrates coated byorderly colloidal polystyrene (PS) monolayer. The PS balls on Si substarte werecomposed with the spheres with the diameters of 200 - 2000 nm, in which the Aulayers with the thickness of 5 - 15 nm were deposited, respectively. The THztime-domain spectroscopy was performed in the standard THz transmissionspectrum configuration by using the GaAs photoconductive antenna THz sourceand free-space electro-optic sampling via ZnTe crystal. The experiments werecarried out under a dry nitrogen purge at room temperature. We find that themetal-insulator transmission is determined by not only the thickness of Au shellbut also the diameter of Au/dielectric spheres. The Au/PS sphere arrays with 500nm diameter does not show the metallic THz response even when the Au shellthickness is larger than 15 nm, which deviates from the observation in flat Au filmon Si substrate. More interestingly, the Au sphere arrays with 5 nm thicknessshows extraordinary absorption bands in frequency dependent absorptionspectra (see Fig. 1). Such effect is associated to the quantum confinement totrap electrons in sphere potential well of gold shell in the array structure. StrongTHz absorption bands located at about 0.6, 1.2, and 1.7 THz can be observedwhen the shell thickness is at about 5 nm. These results demonstrate that Micro/Nano-structured periodic Au/dielectric sphere arrays can modulate the THzabsorption by varying the thickness of gold shell and size of the sphere. We hopethese interesting findings can shed some lights on the application of goldnanosphere arrays as THz plasmonic devices. References[1] D. Qu, D. Grischkowsky, and W. Zhang, Opt. Lett. 29, 896 (2004). [2] A. K. Azad, Y. Zhao, and W. Zhang, Appl.Phys. Lett. 86, 141102 (2005).

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Fig.1:TDS spectra of gold nanosphere arrays at a fixed shell thickness 5 nm for different sphere diameters from200 to 2000 nm.

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TuP4-2 | Splitting of cyclotron resonance peaks in parabolicallyconfined quantum dots in the presence of high magnetic fieldsand intense terahertz radiation fields (#204)Weiyang Wang, Chengxiang Zhao , Shuhui Zhang, Wen XuInstitute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031,China ContentAt present, the magneto-optical measurement has been a powerful andcommonly used experimental technique to characterize and studysemiconductor-based quantum dot (QD) systems [1]. Two absorption peaksobserved at cyclotron resonance (CR) frequencies [2] are often applied todetermine the sample and structure parameters of a QD, such as thecharacterization frequency or strength of the confinement of the QD. Inconventional magneto-optical measurements, the light radiation levels arerelatively low. With the development and application of terahertz (THz) free-electron lasers (FELs), now it becomes possible to conduct magneto-opticalmeasurements in the presence of intense THz radiation fields. In this work, weexamine theoretically what happens when the radiation field becomes intense inthe magneto-optical measurements on a parabolically confined QD. Here wedevelop a non-perturbative approach to handle magneto-photon interaction bysolving exactly the time-dependent Schrödinger equation in which the magneticand radiation fields are included. By employing time-dependent Green’s functionapproach, we obtain the steady-state electronic transition rate induced bymagneto-photon-phonon coupling. Then the electronic energy transfer rate ormagneto-optical absorption coefficient is evaluated by the energy-balanceequation derived from the Boltzmann equation. We find that at relatively lowradiation levels, two peaks of CRs appear at two Kohn’s frequencies (see Fig. 1),as previously observed experimentally [2,3]. In such a case, the strength and thewidth of magneto-optical absorption increase with radiation intensity. When theradiation is intense enough, the splitting of CR peaks can be observed and thesplitting increases with radiation intensity. Interestingly, at intermediate radiationlevels, the splitting of CR peak at higher resonant frequency can be observedwhereas is not appeared at lower one. Moreover, in the vicinity of resonantfrequencies, the magneto-optical transitions can be achieved via multi-photonabsorption and emission channels. We discuss the physics reasons behind theseinteresting theoretical findings and predications. It is worthy to mention that thesimilar phenomena induced by intense light radiation have been observedexperimentally in bulk materials [4] and in GaAs-based two-dimensional electrongas systems [5]. References[1] T. Chakraborty, Quantum Dots (North-Holland, Amsterdam, 1999). [2] B. Meurer, D.Heitmann, and K. Ploog,Phys. Rev. Lett. 68, 1371 (1992). [3] C. Sikorski and U. Merkt, Phys. Rev. Lett. 62, 2164 (1989). [4] B. K. Meyer, D.M. Hofmann, D. Volm, W. M. Chen, N. T. Son, and E. Janzén, Phys. Rev. B 61, 4844 (2000). [5] W. Xu, R. A. Lewis,P. M. Koenraad, and C. J. G. M. Langerak, J. Phys: Condens. Matter 16, 89 (2004).

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Fig1:Electron energy transfer rate per electron (or optical absorption coefficient) as a function of radiationfrequency at a fixed magnetic field for different radiation intensities. Here F0 is the electric field strength ofthe radiation field.

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TuP4-3 | GR-FET application for high frequency detectiondevice (#249)Yuichi Ochiai1, Mahjoub Akram M. 1, Takuto Abe1, Katsuhiko Miyamoto2,Taashige Omatsu2, David K. Ferry3, Koji Ishibashi4, Nobuyuki Aoki1, Jonathan P.Bird5

1Chiba University Nano Science, 1-33 Yayoi, Inage, Chiba, Chiba 263-8522,Japan 2Chiba University Nano Imaging, 1-33 Yayoi, Inage, Chiba, Chiba 263-8522,Japan 3Arizona State University Electrical Engineering, Tempe, Arizona AZ85287-5706, United States4RIKEN Advaced Device Lab., Saitama, Wako 351-0198, Japan 5SUNY Buffalo Electrical Engineering, Buffalo, New York NY 14216, UnitedStates ContentConductance fluctuations in basic quantum transport have been widely studied ina variety of systems [1], and also their application as a broadly tunable sensorhas been discussed for use in the microwave and terahertz (THz) regimes. Asmall forbidden gap appears in bilayer graphene (BGR), whose characteristicquantum transport seems to be due to massive Dirac fermions, in markedcontrast to conventional semiconductors whose relevant band-gaps are typicallyseveral orders of magnitude larger. In our study, we discuss the results ofstudies of high frequency transport in BGR at room temperature, specificallyfocusing on an analysis of the trans-conductance in microwave frequencyregions in order to prepare for THz irradiation experiments. In our previous studyin semiconductor QD THz sensor [2], already a basic frequency characteristichas been clarified by use of conventional microwave trans-conductancemeasurement setup system. Following such high frequency measurements,BGR two-terminal strip line has been prepared as a QD and the microwavetrans-conductance measurements has been performed by using of microwavetransmitter, high frequency detective oscilloscope, the spectrum analyzer andmicrowave power meter, as shown in Fig. 1. In our observation of such highfrequency characteristics in BGR QD, the room temperature result shows a clearresponse up to several ten GHz region. Therefore, we clarify two importantcharacteristics here, on the power and the intensity components of themicrowave transmission. Therefore, it is found that at RT the BGR QD shouldwork in a broad frequency range up to 40 GHz. This work is supported in part byGrants-in-Aid for Scientific Research from JSPS (19054016, 19204030 and16656007), also JSPS Core-to-Core Program, and in partly supported by GlobalCOE program at Chiba University (G-03, MEXT) and also by internationalstudent exchange between Chiba University and SUNY Buffalo. References[1] Y. Ujiie , S. Motooka , T. Morimoto , N. Aoki , D. K. Ferry , J. P. Bird and Y. Ochiai, J. Phys.: Condens. Matt. 21(2009) 382202. [2] A. M. Mahjoub, S. Motooka, N. Aoki, J. Song, J. P. Bird, Y. Kawano, D. K. Ferry, K. Ishibashi, andY. Ochiai, Jpn. J. Appl. Phys. 50, (2011) 070119.

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Fig.1:Experimental layout of the GHz & THz range high frequency detection for the low power resistancechange in the power passing and stopping characteristics at room temperature in order to apply for highfrequency radiation sensor using BGR-FET.

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TuP4-4 | Ionization of coherent excitons in (GaIn)As/GaAsquantum wells by strong terahertz fields (#259)Benjamin Ewers 1, Niko Köster1, Ronja Woscholski1, Martin Koch1, SangamChatterjee1, Galina Khitrova2, Hyatt Gibbs2, Andrea Klettke3, Mackillo Kira3,Stephan Koch3

1Philipps-Universität Marburg Faculty of Physics and Materials Sciences Center,Renthof 5, 35037 Marburg, Germany 2The University of Arizona College of Optical Sciences, 1630 E. University Blvd.,Tucson, Arizona 85719-0094, United States3Philipps-Universität Marburg Faculty of Physics and Materials Sciences Center,Mainzer Gasse 33, 35037 Marburg, Germany ContentWe observe Rabi flopping at the excitonic 1s-2p transition and the multi-THz-photon ionization with increasing field strength by monitoring the changes of theoptical absorption of a multiple quantum well structure simultaneously excitedwith strong THz. 1. Introduction Using an optical white light – strong THztransmission experiment we create an excitonic polarization in high-quality(GaIn)As/GaAs multiple quantum well structure. The simultaneous excitation withstrong single-cycle THz pulses addresses several intraband-transmissions of theexcitonic polarizations (Fig. 1), going well beyond in nonlinearity than reportedearlier [1, 2]. By monitoring the changes to the linear optical absorptionintroduced by the strong THz pulse we observed a bleaching and a clearlysplitting of the 1s-excitonic resonance as welle a high dynamically change of thehigh energy side of the optical spectrum. 2. Results Figure 2 displays theabsorption spectra αL of the transmitted optical pulse at different THz-fieldstrengths. It shows an increasing bleaching and a clear splitting of the 1s-excitonresonance with higher THz-field strengths. Furthermore, high dynamicalmodulations above and below to the 1s-exciton resonance as well as of thecontinuum are observed. The latter indicate the generation of higher THz-harmonics while the former are signatures of THz-multi-photon ionization of the1s excitonic polarization. We reproduced all experimentally observed features byanalyzing our fndings using a microscopic quantum-mechanical many-bodytheory [3,4]. 3. Conclusions In conclusions, we have investigated the interactionof strong single-cycle THz-pulses with a coherent excitonic polarisation andobserve the transition from Rabi flopping of the 1s-2p transition to multi THz-photon ionization with increasing field strength. References[1] A. D. Jameson, J. L. Tomaino, Y.-S. Lee, J. P. Prineas, J. T. Steiner, M. Kira, and S. W. Koch, Applied PhysicsLetters 95, 201107 (2009). [2] M. Wagner, H. Schneider, D. Stehr, S. Winnerl, A. M. Andrews, S. Schartner, G.Strasser, and M. Helm, Phys. Rev. Lett. 105, 167401 (2010). [3] J. R. Danielson, Y.-S. Lee, J. P. Prineas, J. T.Steiner, M. Kira, and S. W. Koch, Phys. Rev. Lett. 99, 237401 (2007). [4] J. T. Steiner, M. Kira, and S. W. Koch,Phys. Rev. B 77, 165308 (2008).

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Fig. 1:Schematically experimental situation of the excitionic system. The excitionic polarizations are created by aweak optical pulse by exciting the |vac> to |1s> transition. The |1s> to |2p> transition is excited by thestrong Thz-pulse.

Fig. 2:Optical absorption spectrum of the multiple quantum well structure by simultaneously excitation withstrong THz-pulses. The THz-field strength increases from the black line with no field applied to the lightred line with a THz field strength of 15kV/cm.

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TuP4-5 | Terahertz plasmon and surface plasmon modes inhollow nanosphere (#260)Y. M. Xiao1, Y.y. Zhang1, Wen Xu 1,2

1Yunnan University Department of Physics, Kunming 650091, China2Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031,China ContentAt present, it has become possible to fabricate metal and semiconductor hollownanosphere structures in which the radius and shell thickness of the sphere canbe controlled artificially [1]. In recent years, such structures have been widelyapplied to realize terahertz (THz) plasmonic devices [2]. Hence, it is of greatimportance and significance to study the electronic subband structure andcorresponding collective electronic excitations from these advanced nano-material systems. In this work, we study theoretically the electronic subbandstructure and the collective excitations associated with plasmon and surfaceplasmon modes for electron gas in gold hollow nanospheres. The eigenvalue andeigenfunction of the sample structure are obtained by solving the Schrdingerequation using hard-shell confinement approximation. We find that different `l’states roughly degenerate when the outer radius of a sphere r2>100 nm. In thiscase, the energy spectrum of the structure is mainly determined by the `n’quantum number. It is found that the electronic subband energy depends muchmore sensitively on the shell thickness than on the outer radius of the hollownanosphere. Employing the random phase approximation (RPA), we calculatethe plasmon and surface plasmon modes in these structures. We find that theplasmon and surface plasmon excitations can be achieved via inter-subandelectronic transition channels. Two branches of the plasmon oscillations and twobranches of the surface plasmon oscillations can be observed, respectively.From Fig. 1, we see that: i) the higher-frequency branch of the plasmon mode isslightly higher than that of the surface plasmon mode; ii) the frequencies of allthese modes are in the THz bandwidth; and iii) they depend strongly on size andshell thickness of the nanosphere. The theoretical findings from this work confirmthat hollow gold-nanosphere structures are indeed the THz plasmonic materialswhich can be applied as frequency-tunable THz optoelectronic devices. References[1] G. T. Duan, F. J. Lv, W. P. Cai, Y. Y. Luo, Y. Li and G. Q. Liu, J. Phys. Chem. B 26 6295 (2010). [2] D. K. Polyushkin,E. Hendry, E. K. Stone, and W. L. Barnes, Nano Lett. 11 4718 (2011).

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Fig.1:Plasmon and surface-plasmon frequencies as a function of outer radius r2 of gold hollow nanosphere for afixed shell thicknesses d= 10 nm.

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TuP4-6 | Higher temperature operation LO phonondepopulation terahertz quantum cascade lasers design withhigh-Al-composition (#274)Tsung-Tse Lin , Hideki HirayamaRIKEN Terahertz Quantum Device Laboratory, 519-1399 Aoba, Aramaki, Aoba-ku, Miyagi, Sendai 980-0845, Japan Content A promising compact solid-state THz source: THz QCLs [1][2] utilize carrierrecycling and intersubband transition in repeated quantum well structures areexpected for widely application. Even a state-of-the-art GaAs/Al0.15Ga0.85Asstructure with LO phonon depopulation scheme design already reportedmaximum operation temperature up to near 200 K [3]. Higher temperatureoperation THz QCLs is still earnest required. Here we study the High-Al-composition GaAs/AlxGa1-xAs and AlxGa1-xAs/AlyGa1-yAs LO phonon depopulationscheme design THz QCLs to reduction of threshold current density Jth andimprovement of characteristic temperature T0. The increase of the total LO-phonon energy expected to improve the temperature performance near currentlimited temperature region. This proposal suggests one more characteristic forthe alignment of structures design. We already reported the experiment resultsof increasing barrier Al composition in Cu-Cu metal-metal waveguide THz QCLswith 4-well LO phonon depopulation scheme design [4]. The results show thedecrease of Jth about 20% when we increase Al composition from 15 % to 35 %.The calculation of phonon mode derived within the macroscopic dielectriccontinuum model. And take into account both confined mode and interface modephonon which calculated from transfer matrix method. Dominant scatteringprocess between two lasing states of THz QCLs at higher temperature region ismainly limited as thermally activated LO-phonon scattering and highly related tothe relaxation time τu-l. Increase of Al composition in structures cause theaveraged LO phonon energy increase. And the non-radiative leakage via LO-phonon scattering between two lasing states is reduced near high temperatureregion. Figure 1 shows the effect of thermally activated LO scattering through τu-l

is rapidly increased at the temperature above 100-150K dependent on differentstructures design. It causes a reduction in Jth and improves T0. Here we focus onthe effect of high-Al-composition structures near recent limited highertemperature operation region. The upper lasing state scattering rate will increaseby proper fine design with higher Al composition in structures are expected toimprove temperature performance of the recent GaAs based THz QCLs. References[1] J. Faist et al., Science 264 (1994) 553. [2] R. Köhler et al., Nature 417 (2002) 156. [3] S. Fathololoumi et al., Opt.Express 20 (2012) 3866. [4] T. T. Lin et al., APEX 5 (2011) 012101.

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Figure1:Solid line is the simulation of higher Al composition THz QCL and triangle point is the experiment results.

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TuP4-7 | Landau level population inversion and stimulatedterahertz transitions in asymmetric quantum well structures intilted magnetic field (#279)Maksim Telenkov 1,2, Yury Mityagin1, Petr Kartsev3

1P.N. Lebedev Physical Institute of RAS Solid State Physics Department,Leninskiy prospekt 53, 119991 Moscow, Russia2Moscow Institute for Steel & Alloys Theoretical physics and QuantumTechnologies Department, Leninskiy prospekt 4, 119049 Moscow, Russia3National Research Nuclear University MEPhi Department of solid state physicsand nanosystems, Kashirskoye shosse 31, 115409 Moscow, Russia ContentThe work is devoted to the investigation of Landau level (LL) population inversionin periodic resonant tunneling quantum well structures with asymmetric periods intilted magnetic field. Previously [1,2] the possibility was shown to achieve theintersubband LL inversion in periodic superlattice-like quantum well structuresunder resonant tunneling pumping of the upper subbands in wide range ofmagnetic field strength. This result may give the way to obtain a terahertzstimulated emission tunable in wide spectral range. However the transition ofinterest from 0-th LL of higher subband to 1-st LL of the lowest one is opticallyforbidden in a magnetic field perpendicular to the structure layers. In [2] it wasshown the possibility to overcome this selection rule by placing the structure intilted magnetic field and simultaneously providing the asymmetrical potential byapplying an electric field along the structure growth direction. It was also statedthat more effective way is the use of asymmetric construction of the structureperiod. Here we considered periodic GaAs/AlGaAs quantum well structures withan asymmetric period consisting of two coupled quantum wells of different width.It was shown that in considered asymmetric structures a rather high value of thedipole matrix element for the transitions of interest can be achieved. Thepreviously developed inter-Landau level scattering model was extended to thecase of structures with complex period and arbitrarily directed magnetic field. Thecalculation of inter-LL electron-electron scattering times and analysis of electronkinetics shown also that in such asymmetric structures the degree of populationinversion can be considerably higher than in symmetric ones. The populations ofLL’s and the values of optical gain were calculated as functions of magnetic field,structure parameters, doping and tunneling rate. The work was supported byRussian Basic Research Foundation (grants No. 09-02-00671 and 08-02-92505-NCNIL) and by MISIS grant 3400022. References[1]. M.P. Telenkov, Yu.A. Mityagin, P.F.Kartsev, J.Phys:Conf. Series, 334, 012059 (2012) [2]. M.P. Telenkov, Yu.A.Mityagin, P.F.Kartsev, JETP Lett., 92(6), 444 (2010)

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TuP4-8 | Intersubband dynamics in two-photon quantum wellinfrared photodetectors (#298)Carsten Franke 1, Harald Schneider1, Hui Chun Liu2, Jérôme Faist3, MartinWalther4

1Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany 2Shanghai Jiao Tong University, Shanghai 200240, China3ETH Zürich, 8093 Zürich, Switzerland4Fraunhofer IAF, 79108 Freiburg, Germany ContentTwo-photon quantum well infrared photodetectors (QWIPs) are interestingnonlinear devices for autocorrelation measurements. Here we present studies ontwo-photon QWIPs in the mid-infrared and THz-regimes. First we investigatesamples in the mid-infrared with absorption wavelengths at around six microns,based on the material systems InGaAs/AlGaAs on GaAs and GaInAs/AlInAs onInP. We study the intersubband relaxation dynamics by interferometricautocorrelation. To create the necessary mid infrared sub-picosecond pulses, weuse a regenerative amplifier system with subsequent wavelength conversion byoptical parametric amplification and difference frequency generation. With this wecan create mid-infrared laser pulses shorter than 200 fs tunable from 3 to 10 µm.For the intersubband relaxation time we determined values between 590 and 730fs. Secondly we present first dark current measurements on AlGaAs/GaAs two-photon QWIPs designed for absorption wavelength in the Thz-regime.

2-P QWIP Autocorrelation:Interferometric Autocorrelation with a two-photon QWIP at 5.5 µm wavelength.

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TuP4-9 | Coexistence of Bloch and Gunn type oscillations insemiconductor superlattices (#299)M. Alvaro , M. Carretero, L. L. BonillaGregorio Millan Institute for Fluid Dynamics, Nanoscience and IndustrialMathematics, Universidad Carlos III de Madrid, Avenida de la Universidad 30,28911 Leganes, Spain ContentBloch oscillations are potentially important to design infrared detectors, emitters,or lasers which can be tuned in the terahertz frequency range simply varying theapplied electric field. We analyze theoretically Bloch oscillations in a dopedsemiconductor superlattice with long scattering times and almost elasticcollisions so that the damping of Bloch oscillations is small and convectivenonlinearities may compensate it. In this case, Bloch oscillations persist in thehydrodynamic regime and, for low enough temperatures, they may coexist withGunn type oscillations. To demonstrate this, we propose a Boltzmann-Poissontransport model of miniband superlattices with inelastic collisions and derivehydrodynamic equations for the electron density, the electric field, and thecomplex amplitude of the Bloch oscillations by means of singular perturbationmethods [1]. At 70K, their numerical solutions for a dc voltage biased superlatticeexhibit a current density showing coexistence of stable inhomogeneous Blochoscillations of frequency 0.36 THz modulated by 13.8 GHz Gunn type oscillations[2]; see the figure. Our novel finding of coexisting Bloch and Gunn typeoscillations runs contrary to the widespread belief that Gunn type oscillationshave to be eliminated to get Bloch oscillations. For larger temperatures (300 K)there are only Bloch oscillations with inhomogeneous stationary amplitude andelectric field profiles. The Bloch oscillations disappear as the collisions becomesufficiently inelastic and scattering times become sufficiently short. References[1] L. L. Bonilla, S. W. Teitsworth, Nonlinear wave methods for charge transport. Wiley, Weinheim, 2010. [2] L. L.Bonilla, M. Alvaro and M. Carretero, Phys. Rev. B, 84, 155316 (2011).

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Fig. (a):Total current density vs time during coexisting Bloch and Gunn type oscillations at 70 K.

Fig. (b):Fourier transform of the total current density showing two peaks corresponding to coexisting Bloch (0.36THz) and Gunn type (13.8 GHz) oscillations

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TuP4-10 | Cyclotron resonace in HgTe/CdTe basedheterostructures in quantizing magnetic fields (#354)Anton Ikonnikov 1, Maxim Zholudev1, Artem Lastovkin1, Kirill Maremyanin1, KirillSpirin1, Alexander Antonov1, Vladimir Gavrilenko1, Milan Orlita2, OlexiyDrachenko3, Manfred Helm3, Michelle Goiran4, Frederic Teppe5, Wojciech Knap5,Sergey Droretskiy6, Nikolay Mihailov6

1Institute for Physics of Microstructures of the Russian Academy of Sciences,GSP-105, 603950 Nizhny Novgorod, Russia2Laboratoire National des Champs Magnetiques Intenses (LNCMI-G), 25 rue desMartyrs, B.P. 166, 38042 Grenoble, France 3Institute of Ion-Beam Physics and Materials Research, FZD, BautznerLandstraße 400, 01328 Dresden, Germany 4Laboratoire National des Champs Magnetiques Intenses (LNCMI-T), 143Avenue de Rangueil, F-31400 Toulouse, France 54 Laboratoire Charles Coulomb (LCC), Universite Montpellier II, 34095Montpellier, France 6Institute of Semiconductor Physics, Siberian Branch of the Russian Academy ofSciences, pr. Lavrentieva 13, 630090 Novosibirsk, Russia ContentHgTe/CdTe based quantum well (QW) heterostructures are of interest both forfundamental research, because they have a number of remarkable properties, aswell as for practical applications, especially as the detectors of terahertzradiation. For example, such heterosystems are known as "topological insulator"[1]. Also the simultaneous existence of two-dimensional (2D) electrons and holes[2] was found in HgTe/CdHgTe heterostructures. Nevertheless the band structureof HgTe/CdTe based QW heterostructures is not well known. Cyclotronresonance (CR) is an effective method for band structure determination. In thiswork we present the results of CR study in HgTe/CdTe based QWheterostructures in quantizing magnetic fields. We found a systematicdiscrepancy of the calculation results and experimental data that also can beobserved in other works (see, for example, [3]). We propose a “corrected” bandparameters (VBO – valence band offset and Ep - interaction energy between theS and P bands) for Kane’s Hamiltonian that allow us to fit calculation results toexperimental data better when the “traditional” band parameters is used [4]. References[1] M. König, S. Wiedmann, C. Brüne, A. Roth, H. Buhmann, L. Molenkamp, X.-L. Qi, S.-C. Zhang // Science 318,766 (2007). [2] G. M. Gusev, E. B. Olshanetsky, Z. D. Kvon, N. N. Mikhailov, S. A. Dvoretsky, and J. C. Portal //Phys. Rev. Lett. 104, 166401 (2010). [3] M. Orlita, K. Masztalerz, C. Faugeras et. al. // Phys. Rev. B, 83, 115307(2011) [4] E. G. Novik, A. Pfeuer-Jeschke, T. Jungwirth et al. // Phys. Rev. B 72, 35321 (2005).

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Fig. 1:Typical CR spectra in the HgTe/Cd0,72Hg0,28Te heterostructure (dQW=7nm).

Fig. 2:The calculated transition energies (lines) and CR peaks positions (symbols) in HgTe/Cd0,72Hg0,28Teheterostructure. Solid lines - "corrected" parameters, dotted - "traditional".

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TuP4-11 | Intraexcitonic coherent nonlinear optics in quantumwells (#361)Martin Teich 1, Martin Wagner1, Dominik Stehr1, Harald Schneider1, ManfredHelm1, Andrea Klettke2, Sangam Chatterjee2, Stephan Koch2, Hyatt Gibbs3,Galina Khitrova3

1Helmholtz-Zentrum Dresden-Rossendorf Institute of Ion Beam Physics andMaterials Research, Bautzner Landstraße 400, 01328 Dresden, Germany 2Philipps University Faculty of Physics and Material Sciences Center, Renthof 5,35032 Marburg, Germany 3The University of Arizona College of Optical Sciences, 1630 East UniversityBoulevard, Tucson, Arizona 85721, United States ContentA fundamental problem in light-matter interaction is the coupling of an intense,monochromatic electromagnetic wave with a quantum mechanical two-levelsystem. One effect related to this is the Autler-Townes or AC Stark effect.Originally observed and described in molecular spectroscopy the effect refers toa splitting of an energy level that is resonantly coupled via intense radiation to anadjacent level, i.e. the states get ”dressed” by the light-matter interaction. Weinvestigate this effect using a free-electron laser (FEL) driven intra-excitonictransition between the heavy-hole 1s and 2p states in a semiconductor multiplequantum well. We have observed distinct intensity- and wavelength dependentRabi sidebands of the 1s exciton line when the FEL was tuned around the 1s-2ptransition [1]. We also present measurements at higher electric fields exploringthe regime beyond the rotating-wave approximation (RWA), where the Rabienergy is comparable to the transition energy. Theoretical calculations supportthe understanding of the underlying processes, which is especially interesting forthe regime beyond the RWA. Also temperature-dependent measurements havebeen done and a clear Rabi-sideband behavior is observable up to 200 K wherethe thermal energy already exceeds the exciton binding energy by a factor of 1.7[2]. A threefold NIR transmission change at 200 K on picosecond timescalescould be promising for optical modulators with Peltier-cooling. References[1] M. Wagner, H. Schneider, D. Stehr, S. Winnerl, A. M. Andrews, S. Schartner, G. Strasser, and M. Helm, Phys.Rev. Lett. 105, 167401 (2010) [2] M. Wagner, M. Teich, M. Helm, and D. Stehr, Appl. Phys. Lett. 100, 051109 (2012)

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GaAs/AlGaAs quantum well:Near resonant THz pumping of the heavy-hole (1s) –(2p) transition at 295 K with a peak field strength of14 kV/cm.

InGaAs/GaAs quantum well :Near-resonant pumping of the heavy-hole (1s)–(2p) transition. The heavy-hole (1s) absorption line isprobed by a weak NIR beam.

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TuP4-12 | THz spectroscopy of optically excited InGaAs-GaAsquantum wells (#367)Johannes Schmidt , Martin Teich, Dominik Stehr, Stephan Winnerl, HaraldSchneider, Manfred HelmHelmholtz-Zentrum Dresden-Rossendorf Institute of Ion Beam Physics andMaterials Research, POB 51 01 19, 01328 Dresden, Germany ContentIntersubband transitions in "wide" quantum wells are interesting in combinationwith standard THz sources based on photoconductive antennas where thebandwidth is limited to few THz. In addition, low-energy transitions at photonenergies of less than 10 meV are interesting for nonlinear and coherent THzphysics since necessary powers are much lower than at higher photon energies,thus making available new possibilities in THz spectroscopy. In this work thephoto-induced absorption of THz radiation in 40 nm wide InGaAs-GaAs quantumwells is investigated by time-domain THz spectroscopy to get information aboutthe electron dynamics. In these experiments, a photoconductive antenna is usedto generate THz radiation with a spectral range from 0.3 to about 2.5 THz and asynchronized 800 nm excitation pulse is used to generate carriers in theconduction and valence band. The transmitted probe beam is then detected byelectric optic sampling. Fig. 1 shows the differential absorption spectrum asobtained from a Fourier analysis of the differential THz transmission. The peak at1.25 THz is attributed to intersubband absorption. The line width at a bathtemperature of 4 K corresponds to a time constant of 1.9 ps, which we associatewith the dephasing time of the intersubband transition. While the data in Fig. 1have been obtained for non-resonant interband excitation at 800 nm, we alsoinvestigate the behaviour under resonant excitation at the energy of the heavy-hole exciton using a wavelength tuneable pump source. THz transmissionsignals as obtained using these two excitation methods will be compared. Wethank Hychul Kim and Pierre Petroff for sample growth as well as ChristopherMorris for processing the sample.

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Fig. 1: :Intersubband absorption in InGaAs quantum wells

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TuP4-13 | Interband absorption and photocurrent in type-IIInAs/GaSb superlattices (#376)Marcos H. Degani 1, Justino R. Madureira2, Marcelo Z. Maialle1

1Universidade Estadual de Campinas Faculdade de Ciências Aplicadas, RuaPedro Zaccaria,1300, Limeira, São Paulo, 13484-350, Brazil 2Universidade Federal de Uberlândia, Ituiutaba, Minas Gerais, Brazil ContentInfrared photodetector devices based on InAs/GaSb superlattice (SL) wereproposed long time ago1 and are now objects of intense studies. By tailoring theindividual layers of the different semiconductors SL, the hetero-structure gapenergy can be modified over the range spanning from 0 to 400 meV. We can findin the literature InAs/GaSb SL with very thin GaSb layers, which allow broaderand lower electron miniband energy. Many theoretical works, as many-band k.pcalculations, have been done in order to obtain the InAs/GaSb SL band structure,taking into account realistic conditions such as band mixing, strain, piezoelectricfields. In the present work, we focused on the photo-excitation processes leadingto the generation of the photocurrent. Our InAs/GaSb SL model consists of onlyone conduction band and one valence (HH) band, with the photo-injected carriescreated by light exciting close to the band edge, avoiding, in this way, bandmixing and multiple-band excitation issues. The dynamical interband polarization,P(ze,zh,t), is described by the semiconductor Bloch equation (SBE) in real-spaceand time representation2 . The hamiltonian operator includes the kinetic energyterms, the electron-hole Coulomb interaction, the band-edge potential profiles,and a longitudinal oscillatory electric field. The SBE is solved using the time-evolving technique of split-operator.3 Our discussion presents comparisonsbetween the optical absorption and the photocurrent spectra, emphasizing thefact that the latter depends on the optical transitions, but also on the carriertransmission through the system. The use of a longitudinal oscillatory electricfield is discussed, since it can lead to dynamic localization for carriers in spatially-periodic potential.2 The authors (MHD and MZM) acknowledge financial supportfrom FAPESP and DISSE-INCT de Nanodispositivos Semicondutores - CNPq,Brazil. References[1] G. A. Sai-Halasz, R. Tsu, and L. Esaki, Appl. Phys. Lett. 30, 651 (1977). [2] J. R. Madureira, P. A. Schulz, andM.Z. Maialle, Phys. Rev. B 70, 033309 (2004). [3] M. H. Degani and M. Z. Maialle, J. Comput. Theor. Nanosci. 7, 454(2010).

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TuP4-14 | THz Generation by Gunn Oscillations in UnipolarNanodiodes (#552)Mubarak Ali , Aimin SongUniversity of Manchester School of Electrical & Electronic Engineering,Manchester, M13 9PL, Great Britain ContentA pressing concern in the deployment of terahertz (THz) technology is the lack ofefficient and portable THz emitters. Recently, self-switching diodes (SSDs) havebeen demonstrated to detect microwave radiation up to 1.5 THz at roomtemperature.1,2 The SSD is a novel unipolar device whose diode-like current-voltage characteristic is based on breaking symmetry of a nanochannel, ratherthan using any doping junction or Schottky barrier as in a conventional diode.The new working principle and the planar architecture result in extremely lowparasitic capacitances and hence enable THz speed. Apart from thedemonstrated THz detection, SSD has recently been envisaged to operate as anemitter in the THz regime under suitable DC biases.3,4 In this work, we modelledin a planar InGaAs SSD as shown in Fig. 1(a), using Silvaco Atlas to provideevidence of dipole domain formation in the channel and systematically studiedthe dependence of emission frequency and intensity as a function of channellength and width as well as interface-charge density. Fig. 1(b) shows the currentresponse obtained when the voltage applied to the SSD is incremented in stepsof 0.5 V every 50 ps. Current oscillations having a frequency of 0.24 THz arise ata threshold voltage of 1.5 V which corresponds to the critical electric fieldrequired for Gunn oscillation. From the electron dynamics plots, we obtainevidence of charge dipole domain formation at the position of the vertical trench.These domains travel parallel to the conduction layer, as opposed toperpendicular to the layer in traditional vertical devices (Fig. 1c). The analyticalresults showed that the fundamental oscillation frequency can reach as high as0.4 THz for geometrical alterations to channel length and width, whereas a high-interface charge density enabled higher harmonics to reach well beyond 1.2 THz.By careful construction of an array that contains different geometries of SSDsplaced in parallel, we expect to achieve the tuning of frequency in wide andnarrow bands, which may have useful implications to practical applications. References1 A. M. Song et al., Appl. Phys. Lett. 83, 1881 (2003). 2 C. Balocco et al., Appl. Phys. Lett. Matter. 98, 223501(2011). 3 K. Y. Xu et al., Appl. Phys. Lett. 93, 233506 (2008). 4 T. Gonzalez et al., J Phys.: Conf. Ser. 193, 12018(2009).

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Fig. 1:Fig. 1. (a) Geometry of the InGaAs SSD. (b) Current response for ∆V=0.5 V applied every 50 ps. (c)Electron density profiles along the centre of channel during one period of oscillation. The dotted linesrepresent the beginning and end of the chann

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TuP5-1 | Electron Beam Reduction method for Preparing theCatalyst Layer in the Growth of Carbon Nanotubes (#4)Azam Mahmoodi Plasma Physic Research Center, Science and Research branches, Islamic AzadUniversity physics, Tehran, Iran ContentIn this paper, electron beam reduction method is applied for preparing theparticles of catalyst in the growth of carbon nanotubes (CNTs). A hot cathodicelectron beam facility was employed to electron bombarding of catalyst layerbefore stage of CNTs growth. This new method leads to reducing the diameter ofparticles via sputtering and evaporating the surface of catalyst. The growth ofcarbon nanotubes was performed on the Fe catalyst layer with SiO2 substrate inan environment of different mixed gases (H2, NH3 and C2H2) by ThermalChemical Vapor Deposition (TCVD) system. .The morphology of the electronbeam reduced catalyst particles were probed by Atomic Force Microscopy(AFM). All samples were analyzed by Scanning Electron Microscopy (SEM)before and after growth of CNTs. SEM analyzes clarified that the catalyst grainshas been smaller under effect of electron beam bombardment. References[1] A. Loiseau, P. Launois, P. Petit, S. Roche and J.P. Salvetat, Understanding carbon nanotubes: from basics toapplications, Springer, Lecture Notes in Physics (2006) vol. 677. [2] H. Takikawa, M. Ikeda, K. Hirahara, Y. Hibi, Y.Tao, P.A. Ruiz Jr., T. Sakakibara, S. Itoh and S. Iijima, Physica B: Condensed Matter 323 (2002), p. 277. [3] M.Zhang, M. Yudasaka and S. Iijima, Chemical Physics Letter 336 (2001), p. 196. [4]C. Singh, M. Shaffer, I. Kinlochand A. Windle, Physica B: Condensed Matter 323 (2002), p. 339. [5] A. Moisala, A.G. Nasibulin and E.I. Kauppinen,Journal of Physics: Condensed Matter 15 (2003), p. S3011. [6] T. Ungar, J. Gubicza, G. Ribarilc, and et al.: Carbon40 (2002) 929.

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AFM images of Fe catalyst:pretreated with electron beam

Fig1(a):AFM images of Fe catalyst :without any pre-treatment

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TuP5-2 | Copper catalyzing growth of Carbon nano tubes onsodalime glass substrate at low temperature (#23)Azam Mahmoodi Plasma Physic Research Center, Science and Research branches, Islamic AzadUniversity physics, Tehran, Iran ContentThermal chemical vapor deposition (TCVD) method was applied in growing ofcarbon nano tubes (CNTs) on soda-lime glass at low temperature. Cu catalystwas coated on glass substrate by using dc magnetron sputtering system and wasetched by hydrogen (H2) gas in order to form nanometer sized catalytic particles.Mixture of C2H2/H2/Ar (20:80:100 sccm) was heated at 580 oC for the CNTsgrowth on the glass substrate. A novel approach utilizing the four-pointprobe method was implemented to measure the change in electrical resistance ofspecimen before and after growth of CNTs at room temperature. The growthbehavior of CNTs is investigated by scanning electron microscopy (SEM). References[1] Iijima S 1991 Nature 354 56–8 [2] S. Iijima and T. Ichihashi, Nature (London) 363 , 603 (1993) . [3] D. S. Bethune, C. H.Kiang, M. S. de Vries, G. Gorman, R. Savoy, J. Vazquez, and R. Beyers,Nature (London) 363 , 605 (1993) [4 ] A. Thess, R.Lee, P. Nikolaev, H. Dai, P. Petit, J. Robert, C. Xu, Y. H. Lee, S. G. Kim, D. T. Colbert, G. Scuseria, D. Tomanek, J.E. Fisher, and R. E. Smalley, Science 273, 483 (1996) . [5] Z. F. Ren, Z. P. Huang, J. W. Xu, J. H. Wang, P. Bush, M. P.Siegal, and P. N. Provencio, Science 282, 1105 (1998)

Fig.1:and 3D AFM images of Cu:glass nanoparticles

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Fig.2:SEM image of Cu:glass nanoparticles

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TuP5-3 | Formation of multi-quantum dots in hydrogenatedgraphene (#77)Chiashain Chuang1,2, Reuben K. Puddy2, Malcolm R. Connolly2, Shun-Tsung Lo3, Huang-De Lin1, Tse-Ming Chen4, Charles G. Smith2, Chi-Te Liang1,3

1National Taiwan University Physics, Taipei Taiwan 2University of Cambridge Cavendish Laboratory, Cambridge, Great Britain3National Taiwan University, Graduate Institute of Applied Physics, TaipeiTaiwan 4National Cheng Kung University Physics, Tainan Taiwan ContentWe report a formation of multi-quantum dots on a hydrogenated single layergraphene flake obtained by mechanical exfoliation. The existence of multi-quantum dots is supported by the low-temperature measurements on a fieldeffect transistor structure device. The resulting Coulomb blockade diamondsshown in the color scale plot together with the number of Coulomb peaks exhibitthe characteristics of the so-called “stochastic Coulomb blockade” as shown inFig. 1 and Fig. 2 [1-3]. A tentative explanation for the formation of the multi-quantum dots, which is not observed on the pristine graphene to date, wasattributed to impurities and defects unintentionally decorated on a single layergraphene flake which was not treated with the thermal annealing process. References[1] I. M. Ruzin and V. Chandrasekhar, Phys. Rev. B 45, 13469 (1992) [2] M. Kemerink and L. W. Molenkamp, App.Phys. Lett. 65, 1012 (1994) [3] M. Suzuki, K. Ishibashi, T. Ida, and Y. Aoyagi, Jpn. J. Appl. Phys. 40, 1915 (2001)

Figure 1:Color scale plot of the conductance G versus VBG and VSD at T = 6.5 K

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Figure 2:The characteristics of stochastic Coulomb blockade in hydrogenated graphene

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TuP5-4 | Electron States in Graphene with One-dimensionalPotential Barriers and Wells (#85)Dmitry Miserev 1,2, Matvey Entin2

1Novosibirsk State University Physical Department, 2, str. Pirogova, 630090Novosibirsk, Russia2Institute of Semiconductor physics, Siberian Branch, Russian Academy ofSciences, prospect Lavrent'eva, 630090 Novosibirsk, Russia ContentElectron states in graphene with one-dimensional potential U(x) are studied in theenvelope approximation. Near the conic points the Hamiltonian H=σp+ U(x) isutilized. The analytical solutions are found for potentials U(x)=-U/(|x|+d) (a), Fx (b)and U tanh(x/a) (c). The potential (a) is applicable to the problem of electronicstates with a Coulomb impurity in a carbon nanotube. The rest potentialscorrespond to the plane graphene with p-n junction. All considered potentials areapplicable as model smooth potential walls. In addition to analytically solvableproblems we have studied different approximate methods for arbitrary potentials,such as the quasiclassics and the series expansion by small y-component ofelectron momentum py. It was found that the reflection probability vanishesproportionally to py

2 . We have found the wave functions, 1D subband energies,transmission and reflection probabilities and phases. The transmissionprobabilities give us the conductance and I-V characteristics of graphene with p-nor n-p-n junctions.In particular case of the model potential (c) the exact solutionfor conductance of p-n junction is G=e2U(πL-1(2πaU)-2)/(8π2 sinh2(πaU)), where L-1(x) -the Struve function. The scattering phases are used for approximatedetermination of the quantum states of a graphene strip with smooth potentialwalls. The potential (a) gives the Coulomb-like electron states. If d tends to zero,the ground state is 2pyU2log2(pyUd) and the rest states have double degeneracy.These results are valid for U<<1. The discrete spectrum condenses to the energyE=py. The transmission coefficient for energies py–U/d<E<-py strongly oscillates, hasweak energy dependence when E=py and has no finite limit when d vanishes.

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TuP5-5 | Excitons in Monolayer Graphene (#161)Mahmood Mahmoodian 1,2, Matvey Entin1

1Institute of Semiconductor Physics, Siberian Division, Russian Academy ofSciences, pr. ak. Lavrent'eva, 13, 630090 Novosibirsk, Russia2Novosibirsk State University, Pirogova str., 2, 630090 Novosibirsk, Russia ContentAs contrasted to the widespread opinion the present contribution is aimed toprove the possibility of moving indirect excitons in monolayer graphene. Weconsider the exciton formation from single-electron and hole states with energies±sk, near the conic points of the single-electron spectrum sk, where s is theelectron velocity and k is the momentum counted from the conic points ±K. Theexcitons binding energy εex is assumed to be much less than the kinetic energy.The pair states are formed from the free-particle states in the vicinity of points inthe momentum space with the same velocities of particles. The conicapproximation does not permit the particle binding, hence we took into accountthe quadratic in momentum corrections to the electron and hole spectra. Theproblem of indirect exciton states is studied analytically and numerically. It isfound that the corrections help the indirect exciton formation with momentumclose to ±2K and hinder the direct exciton formation. The ground energy of theindirect exciton is ε(k)=sk-εex(k), where k±2K is the exciton momentum,εex(k)=π-1skg2log2[4√3/(νka cos3φk)] is the binding energy, g=e2/(sχ) is theinteraction constant, χ is the dielectric constant of external medium, a is thegraphene lattice constant, ν=±1, φk is the angle between K and k. The excitonexists in the sectors of the momentum space νcos3φk>0 and has strong trigonalk-dependence. On the contrary, we have found that the direct excitons ingraphene don't exist. We consider different ways of observation of the indirectexcitons in graphene. We have studied the exciton contribution to the lightabsorption. In addition, unlike the semiconductors with gaps, the grapheneexcitons have gapless spectra. Hence, these excitons are thermally excited downto the zero temperature and contribute to the specific heat and the thermalconductivity. These quantities can be derived using pulse electric heating ofelectron-hole plasma and subsequent cooling with time-resolving measuring ofelectron temperature via quantum corrections to conductivity or width of theShubnikov-de-Haas oscillations.

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TuP5-6 | Electron Energy Relaxation in Graphene (#162)Matvey Entin 1, Lev Magarill1,2

1Institute of Semiconductor Physics, Siberian Branch, Russian Academy ofSciences, 13 prospect Lavrent'eva, 630090 Novosibirsk, Russia2Novosibirsk State University, 2, Pirogova str., 630090 Novosibirsk, Russia ContentThe energy relaxation is important in the problems of hot electron transport, weaklocalization, hot luminescence and photogalvanic effect. The absence of theenergy gap makes the Auger-like relaxation e->2e+h and h->2h+e one of themost essential relaxation processes in the Dirac point. The conic spectrum ofmonolayer graphene determines unusual kinematics of electron and holescattering [1]. In conic approximation the electron-hole scattering is allowed iffinal electrons and holes have the same direction of momentum as initialparticles. Despite seeming small phase space of this process, in fact, it has afinite probability if warping corrections to the spectrum are taken into account .These corrections have trigonal symmetry and they are concave in some sectorsof the momentum space and convex in the rest. The scattering process ispermitted in the sectors of the momentum space where the spectrum is convex.In real graphene there is another competing factor, the interaction corrections tothe spectrum [2], hindering the scattering process. The purpose of the presentcontribution is to study energy relaxation in graphene caused by electron-electron interaction with taking into account both warping and interaction-inducedcorrections to the electron spectrum. We considered the energy relaxation ratefor warm electrons. We found that at low temperature T<Tc (here Tc =(ħs/a) g ln(1 /g),g=e 2/ χħs, s is the electron velocity in the conic approximation, a is the latticeperiod, χ is the dielectric constant of the external medium) the Auger processesare forbidden, but at higher temperature the warping prevails and the Augerprocesses become permitted. The process of relaxation of optically highly excitedelectrons (holes) at low temperature was studied also. The relaxation of hotelectrons by the Auger processes is possible in some sectors of the momentumspace near the conic points. The accounting for the impurity scattering mixes thedirection of the momentum. However, when electrons (holes) achieve thethreshold energy Tc, they stop to relax and produce the inverse population andthe laser effect. We have also estimated the scattering of electrons with excitoncreation and found it as essential one for the momentum and energy relaxation. References[1] L. E. Golub, S.A.Tarasenko, M.V. Entin, and L.I. Magarill, PRB 84, 195408 (2011). [2] E. G. Mischenko, PRL 98,216801 (2007).

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TuP5-7 | Electrical generation of Cerenkov acoustic-phononemission from graphene (#173)Chengxiang Zhao , Shuhui Zhang, Wen XuInstitute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031,China ContentAs it is well known, graphene is an ideal two-dimensional electron gas (2DEG)with high carrier density and mobility at room-temperature(1). Both experimental(2) and theoretical(3) results have already shown that in sharpcontrast to conventional GaAs-based 2DEGs, acoustic-phonon scattering playsan important role in determining electronic transport properties in graphene. As aresult, one can immediately think that graphene should be a good acoustic-phonon source which can be generated electrically through electron-phononinteractions. In this work, we examine the interesting and important features forelectrical generation of acoustic-phonon emission from graphene. Consideringelectron interactions with charged impurities, acoustic-phonons via deformationpotential coupling and with optic-phonons via polar optical coupling, we firstcalculate the drift velocity and temperature for electrons in graphene by solvingself-consistently the momentum- and energy-balance equations derived from theBoltzmann equation. The obtained results for current-voltage response agreeboth qualitatively and quantitatively with experimental data(4). We find that theelectron drift velocity can easily exceed the longitudinal and transverse soundvelocities in graphene. Thus, one can achieve the enhanced acoustic-phonongeneration via a mechanism of Cerenkov phonon emission. We then examinethe dependence of acoustic-phonon emission from graphene on driving electricfield, phonon frequency and phonon emission angle. We find that (see Fig. 1): i)the frequency of emitted phonons in graphene can reach up to about 20 THz,which is much higher than that in GaAs-based 2DEGs; ii) the angulardependence of acoustic-phonon emission in graphene differs from that in CaAs-based 2DEG systems; and iii) when electron drift velocity exceeds the soundvelocities in graphene, the intensity of phonon emission increases sharply withdriving electric field. In this case, the intensity of phonon emission increases alsowith electron density which can be controlled by the applied gated voltage. Theseresults confirm that graphene is very good acoustic-phonon source which can beutilized to realize graphene-based hypersonic devices. References[1] A. H. Castro Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov and A. K. Geim Rev. Mod. Phys. 81.109 (2009) [2]J. H. Chen, C. Jang, S. Xiao, M. Ishigami, and M. S. Fuhrer, Nat. Nanotechnol. 3, 206 (2008). [3] W. Xu, F. M.Peeters, and T. C. Lu, Phys. Rev. B 79, 073403 (2009). [4] A. Barreiro, M. Lazzeri, J. Moser, F. Mauri, and A.Bachtold, Phys. Rev. Lett. 103, 076601 (2009).

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FIG1:(1) Contribution from longitudinal (PL) and transverse (PT) phonon emission at the fixed electric field andphonon emission angle θ=30°. (2)- (4): Frequency and angle dependence of phonon emission for differentelectric fields.

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TuP5-8 | Transmission of acoustic waves through graphene-semiconductor layered structures (#199)Shuhui Zhang , Wen XuInstitute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031,China ContentIn recent years, the investigation into electronic, optical and optoelectronicproperties of graphene has been a hot and fast-growing field of research due topotential and important device applications. However, the acoustic properties ofgraphene based devices have not yet been explored considerably. Graphene is avery thin layer of carbon crystal and its density and sound velocity differ verysignificantly from those in conventional semiconductor materials. One cantherefore expect that the strong mismatch of density and sound velocity at thesemiconductor/graphene interface can lead to important and interesting acousticproperties for semiconductor-graphene layered structures. Here we present adetailed study on how acoustic waves can go through such structures. Employingthe transfer-matrix method, the transmittance for longitudinal acoustic waves isevaluated theoretically. We first compare the results obtained from the cases withand without consideration of the thickness of monolayer graphene. We find thatthe oscillations induced by the presence of the finite thickness of graphene layercan be clearly observed. We also examine the influence of the numbers ofembedded graphene layers in graphene-Si structures on the transmissionspectrum (see Fig. 1). For such structures, the oscillations of the acoustic wavetransmission can be observed. Such effect results from the interference of theacoustic waves at the graphene-semiconductor interfaces. With increasingnumbers of embedded graphene layers, the transmission gaps for longitudinalacoustic wave propagation can be achieved. Moreover, with increasing thicknessof the Si layer to separate the graphene layers, the transmmission gaps are red-shifted. These phenomena are similar to those observed in conventional acousticsuperlattices(1) . The results from this study demonstrate that the graphene-semiconductor layered structures can be utilized to realize novel acousticdevices such as hypersonic filters and phonon mirrors. References[1] S. Tamura, D. C. Hurley, and J. P. Wolfe, Phys. Rev. B 38, 1427 (1988).

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Fig1:Transmission spectrum for Si-graphene layered structures with different graphene layers separated by 11nm thick Si layers.

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TuP5-9 | Random and deterministic simple shear in grapheneand graphene sheet (#226)Raimundo Costa, Gil de Aquino Farias Universidade Federal do Ceará Departamento de física, Campus do Pici,Fortaleza, Ceará, 60455-760, Brazil ContentA tight-binding model is used to study the energy band of graphene andgraphene ribbon under simple shear strain that are random or follow somespecific function on the y-dirction. The ribbon consists of carbon atom lines in anarmchair or zig-zag orientation where a simple shear strain is applied in the x-direction keeping the atomic distances in the y-direction unchanged. Suchmodification in the lattice gives an energy band that differs in several aspectsfrom the one without any shear and with pure shear. The changes in thespectrum depends on the line displacement of the ribbon, and also on themodified hopping parameter. It is also shown that this simple shear strain tunesthe electronic properties of both graphene and graphene ribbon, opening andclosing energy gaps for different displacements of the system. The modifieddensity of states is also shown.

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TuP5-10 | Optoelectronic properties of ABC-stacked trilayergraphene (#250)Y. M. Xiao1, Y.y. Zhang1, Shuhui Zhang 2, Wen Xu1,2

1Yunnan University Department of Physics, Kunming 650091, China2Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031,China ContentAt present, the low-cost and reliable growth of high quality and large sizegraphene films is mainly based on chemical vapor deposition (CVD) technique[1]. Normally the CVD method can produce multi-layer graphene samples.Hence, the investigation into physical properties of multi-layer graphene systemsis of great importance and significance from a view point of device applications.Here we present a theoretical study on optoelectronic properties of ABC-stackedtrilayer graphene (TLG). The optical conductance and light transmittance areevaluated via energy-balance equation derived from the Boltzmann equation foran air/graphene/dielectric-wafer system in the presence of linearly polarizedradiation field. Two different kinds of band structure models [2,3] are examined.For short wavelength radiation, we obtain the universal optical conductanceσ=3e2/(4ћ), which does not depend on temperature and electron density and onthe chosen band structure models. This confirms that the optical conductanceper graphene layer is a universal value σ=e2/(4ћ). Importantly, there exists anoptical absorption window in the radiation wavelength range 10 - 200 µm, whichis induced by different transition energies required for interband and intrabandoptical absorption (see Fig. 1). In particular, we find that the lower frequencyedge of the absorption window is induced by intraband free carrier absorption. Asa result, we find that the position and width of this absorption window dependsensitively on temperature and carrier density of the system, especially the lowerfrequency edge. There is a small absorption peak at about 82 µm where thelargest interband transition states exist in the ABC-stacked TLG model [2]. Incontrast, the relatively smooth curves can be seen by using a simplified model[3]. Comparing with those obtained for mono- [4] and bi-layer [5] graphene, wefind that the optical absorption window is red-shifted with increasing number ofgraphene layers (layer=1, 2, and 3). These theoretical results indicate that multi-layer graphene structures have some interesting and important optoelectronicsproperties which can be utilized to realize infrared or THz optoelectronic devices. References[1] See, e.g., W. Xu, Y.P. Gong, L.W. Liu, H. Qin and Y.l. Shi, Nanoscale Res. Lett. 6, 250 (2011). [2] F. Zhang, B.Sahu, H. Min, and A. H. Mac-Donald, Phys. Rev. B 82, 035409 (2010). [3] H. Min and A. H. MacDonald, Prog.Theor. Phys. Suppl. 176, 227 (2008). [4] W. Xu, H.M. Dong, L.L. Li, J.Q. Yao, P. Vasilopoulos, and F.M. Peeters,Phys. Rev. B 82, 125304 (2010) [5] H.M. Dong, J. Zhang, F.M. Peeters, and W. Xu, J. Appl. Phys. 106, 043103(2009).

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Fig.1:Contributions from different transition channels to optical conductance and the corresponding lighttransmittance at T=150 K. The results from (a) the ABC-stacked TLG model and (b) the simplified modelare shown. Here, σ0=3e2/(4ћ), the results

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TuP5-11 | Bound states in the continuum in trilayer graphenenanoribbons (#325)Natalia Córtes1, Luis Rosales2, Monica Pacheco2, Pedro Orellana 1

1Universidad Católica del Norte Physics, Avenida Angamos, 0610 Antofagasta,Chile 2Universidad Federico Santa Maria Physics, Avenida España, 1680 Valparaiso,Chile ContentInteresting interference effects, which are present in the electronic transportthrough low dimensional systems, are the so-called bound states in thecontinuum (BICs)[1-3]. BICs are discrete states embedded in the continuum ofthe allowed carrier bands. They can be seen as resonances of vanishing linewidth, which can occur when different channels interfere. In recent years, it hasbeen an increasing interest in BICs. In this context, we have studied theformation of BICs in graphene-based structures; the systems are segments ofgraphene ribbons with different widths connected with each other [4]. We haveidentified the presence of BICs in these structures and we have discussed themechanism for their formation. In this work we study the presence of BICs in atrilayer graphene system. The scheme of the system is shown in Fig 1. The centrallayer is coupled to leads, while the top and bottom finite layers are coupled onlyto the central one. BICs would form in this system by the hybridization of thestates of the top and bottom layers coupled by the continuum states of thecentral layer. By applying transversal electric fields the BICs can be modified,since the up-down symmetry is broken and these states would evolve toresonances. By the use of the above interference effect in a trilayer graphenesystem a switch can be designed controlled by the transversal electric field. Weobtain results for the conductance and density of states of the system. Wediscuss the form in which the information about the presence of BICs in theconductance can be extracted. References[1] J. von Neumann, E. Wigner, Phys. Z. 30, 465 (1929). [2] H. Friedrich, D. Wintgen, Phys. Rev. A 31, 3964 (1985);H. Friedrich, D. Wintgen, Phys. Rev. A, 32, 3231 (1985). [3] Federico Capasso, Carlo Sirtori, Jerome Faist, DeborahL. Sivico, Sung-Nee G. Chu, Alfred Y. Cho, Nature 358, 565 (1992). [4] J.W. González , L. Rosales, M. Pacheco andP.A. Orellana, EPL 91, 66001 (2010).

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Figure 1:Trilayer graphene system. The central layer is coupled to leads, while the top and bottom finite layers arecoupled only to the central one.

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TuP5-12 | Study of optical anisotropic property of chemicalvapor deposition prepared graphene films (#334)Yu-Lun Liu 1, Hsuen-Li Chen1, Chen-Chieh Yu1, Chun-Chiang Kuo2, Chen-KaiChang2, Chun-Wei Chen1, Li-Chyong Chen2, Kuei-Hsien Chen2, Yu-Shen Lai31National Taiwan University Department of Materials Science and Engineering,No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan 2National Taiwan University Center for Condensed Matter Sciences, No. 1, Sec.4, Roosevelt Road, Taipei Taiwan 3National Nano Device Laboratories, Hsinchu 300, Taiwan ContentGraphene’s sp2-hydridized carbon atoms are packed in a honeycomb-like crystallattice, forming a near-ideal flat two-dimensional nanostructure, with potentiallyattractive properties for device integration. In this study, we used an opticalspectrometer to measure the optical anisotropy properties of graphene films. Asdisplayed in Figure 1a, we could characterize the optical anisotropy of these two-dimensional materials by measuring the transmission and reflection spectra fortransverse electric (TE) and transverse magnetic (TM) polarized light at differentincident angles. Using this approach, we could examine the optical anisotropyproperties of graphene films with different numbers of stacked layers. First, TE-polarized light is used to calculate the in-plane optical absorption; next, the TM-polarized curve is used to calculate the out-of-plane optical absorption of thegraphene films. Figure 1b to 1e displays the absorption coefficient of one-layerCVD-prepared graphene film at different incident angles and polarizations. Theabsorption coefficients of graphene films for TE-polarized light remained almostconstant upon changing the incident angle. In contrast, the absorptioncoefficients for the TM-polarized light decreased considerably upon increasingthe incident angle. Thus, the absorption coefficients of the graphene layerdepended strongly on the direction of the polarized light, resulting in differentabsorption coefficients for different polarizations. When the electric field of thepolarized light was parallel to the main chain of sp2-hybridized carbon atoms (i.e.,parallel to the graphene surface), the absorption would be greater than that ofother polarizations of incident light. In other words, the absorption coefficientwould reach its largest value in the in-plan direction of the graphene layer. Asdisplayed in Figures 1c to 1e, the difference in absorption coefficients betweenthe TE- and TM-polarized lights increased upon increasing the incident anglefrom 20 to 60°. References[1] Novoselov, K. S.; McCann, E.; Morozov, S. V.; Falko, V. I.; Katsnelson, M. I.; Zeitler, U.; Jiang, D.; Schedin, F.;Geim, A. K. Unconventional quantum Hall effect and Berry's phase of 2in bilayer graphene. Nat. Phys. 2006, 2,177-180. [2] Nair, R. R.; Blake, P.; Grigorenko, A. N.; Novoselov, K. S.; Booth, T. J.; Stauber, T.; Peres, N. M. R.;Geim, A. K. Fine Structure Constant Defines Visual Transparency of Graphene. Science 2008, 320, 1308. [3] Freitag,M.; Chiu, H. Y.; Steiner, M.; Perebeinos, V.; Avourios, P. Thermal infrared emission from biased graphene. Nat.Nanotechnol. 2010, 5, 497-501.

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Figure 1:Figure 1. Schematic representation of angle-variable reflectance and transmittance of different types ofpolarized light. (b-e) Absorption coefficients for different types of polarization at different incident angles

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TuP5-13 | Nanoscale Optical and Electrical Characterization ofAligned Semiconducting Single-Walled Carbon Nanotubes in aField Effect Transistor (#478)R. D. Rodriguez1, Marius Toader 2, S. Hermann3, Evgeniya Sheremet1, S.Müller1, O. D. Gordan1, Y. Haibo4, Stefan E. Schulz3,4, Michael Hietschold2,Dietrich R. T. Zahn1

1Chemnitz University of Technology Semiconductor Physics, D-09107 Chemnitz,Germany 2Chemnitz University of Technology Solid Surfaces Analysis Group, D-09107Chemnitz, Germany 3Chemnitz University of Technology Center for Microtechnologies (ZfM),D-09107 Chemnitz, Germany 4Fraunhofer Institute for Electronic Nano Systems (ENAS), D-09126 Chemnitz,Germany ContentDuring recent years a lot of research has been performed on single-walledcarbon nanotubes as a channel material in thin film transistors [1]prompting theemergence of advanced characterization techniques based on combined atomicforce microscopy and Raman spectroscopy studies [2]. In this context we useconfocal Raman microscopy and current sensing atomic force microscopy (CS-AFM) to study phonons and electronic transport in semiconducting single-walledcarbon nanotubes (SWCNTs). Therefore a CNT transistor structure wasprepared using a silicon substrate covered with a SiO2 dielectric layer andstructured palladium electrodes. Subsequently, purified and type-selected CNTs(98% semiconducting), in deionised water containing 0.2 wt% of sodium dodecylsulfate (SDS), were deposited and aligned between the electrodes bydielectrophoresis [3]. Transconductance measurements of the CNT structuresconfirm transistor properties with an on/off ratio of up to 102. Raman imaging wasperformed in the region around the electrodes on the suspended CNT usingseveral laser excitation wavelengths. Analysis of the G+/G- splitting in the Ramanspectra [4]shows CNT diameter dispersion from 1.3 to 1.9 nm. No surfacemodification, increase in defects density or stress at the CNT-electrode contactwas detected but rather ashift in G+ and G- peak positions in regions with highCNT density between the electrodes. Such behavior is ascribed to CNT-CNTinteraction within the bundles due to van der Waals interactions with a minor butnon-zero covalent component [5]. Simultaneous topographical and electricalcharacterization of the CNT transistor by CS-AFM confirms the presence of CNTbundles having a stable electrical contact with the transistor electrodes. Forsimilar load force, reproducible current-voltage (I/V) curves for same CNTregions verify the stability of the electrical contact between the nanotube and theelectrodes as well as the nanotube and the AFM tip over different experimentalsessions using different AFM tips. However, strong variations in the I/V responseat different regions of the CNT transistor were observed. Our results show thepower in combining Raman imaging with the 3D nanoscale capabilities of currentsensing AFM for understanding and improving future CNT-based devices.

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Acknowledgment The work was supported by DFG Research Unit 1713“Sensoric Micro- and Nanosystems”. References[1] D. T. Pham, H. Subbaraman, M. Y. Chen, X. C. Xu, and R. T. Chen, "Self-Aligned Carbon Nanotube Thin-FilmTransistors on Flexible Substrates With Novel Source-Drain Contact and Multilayer Metal Interconnection," IEEETrans. Nanotechnol. 11, 44-50 (2012). [2] L. S. Liyanage, H. Lee, N. Patil, S. Park, S. Mitra, Z. Bao, and H.-S. P.Wong, "Wafer-Scale Fabrication and Characterization of Thin-Film Transistors with Polythiophene-SortedSemiconducting Carbon Nanotube Networks," ACS Nano 6, 451-458 (2011). [3] A. Kuzyk, "Dielectrophoresis at thenanoscale," ELECTROPHORESIS 32, 2307-2313 (2011). [4] H. Telg, J. G. Duque, M. Staiger, X. Tu, F. Hennrich, M.M. Kappes, M. Zheng, J. Maultzsch, C. Thomsen, and S. K. Doorn, "Chiral Index Dependence of the G+ and G–Raman Modes in Semiconducting Carbon Nanotubes," ACS Nano 6, 904-911 (2011). [5] A. M. Rao, J. Chen, E.Richter, U. Schlecht, P. C. Eklund, R. C. Haddon, U. D. Venkateswaran, Y. K. Kwon, and D. Tomanek, "Effect of vander Waals interactions on the Raman modes in single walled carbon nanotubes," Phys. Rev. Lett. 86, 3895-3898(2001).

Figure 1:Characterization of CNT transistor with scanning electron microscopy, Raman imaging and currentsensing AFM

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TuP5-14 | Conductive AFM for CNTs characterization (#488)Marius Toader 1, Holger Fiedler2, Sascha Hermann2, Stefan E. Schulz2,3, ThomasGessner2,3, Michael Hietschold1

1Chemnitz University of Technology Institute of Physics, Solid Surfaces AnalysisGroup, 09107 Chemnitz, Germany 2Chemnitz University of Technology Center for Microtechnologies, 09126Chemnitz, Germany 3Fraunhofer Research Institute for Electronic Nano Systems, 09126 Chemnitz,Germany ContentWithin a continuous downscaling tendency, the remarkable mechanical andelectrical properties of Carbon NanoTubes (CNTs) recommend them as suitablecandidates for usage in nanoscale electronics and interconnects. Thecorresponding integration with inorganic counterparts toward formation of hybridnanodevices depends strongly on understanding the interface between the metalelectrodes and the CNTs with strong repercussions on the final quality andelectric performance. A versatile technique able to address simultaneouslymorphological and electrical measurements within such nanosystems isConductive Atomic Force Microscopy (C-AFM). In this work, multi-walled CNTs(MWCNTs) networks were vertically grown by chemical vapour deposition on aconductive bottom contact line as described in [1]. Using C-AFM, topographicinformation as well as current mapping of CNTs networks within distinct trencheswere obtained. Despite the constant electric response inside the trenches, clearvariations were found when compared between neighbouring trenches (refer tothe inserted figure). The current-voltage (I-V) characteristics emphasize themetallic character of the CNTs and indicate the difference in the CNTs networksperformance within distinct trenches. The corresponding reproducibility waschecked over multiple measurement sets and distinct locations. The outcome I-Vspectra were found to be highly reproducible and consistent with the voltagedependent current mapping of the CNTs networks. References[1] H. Fiedler, S. Hermann, S. E. Schulz and T. Gessner; online via DOI: 10.1109/IITC.2011.5940346

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Figure:Topography vs current mapping

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TuP5-15 | Novel carbon nanotube film with a self-assembledcarbon-metal heterostructure (#491)Sascha Hermann 1, Steffen Schulze2, Ramona Ecke3, Andreas Liebig2, Stefan E.Schulz1,3, Thomas Gessner1,3

1TU Chemnitz Center for Microtechnologies, Reichenhainer Strasse 70, 09126Chemnitz, Germany 2TU Chemnitz Physics, Reichenhainer Strasse 70, 09126 Chemnitz, Germany 3Fraunhofer Institute for Electronic Nano Systems, Technologie-Campus 3,09126 Chemnitz, Germany ContentWe present a unique nanostructure with carbon nanotubes (CNTs), where acontinuous and smooth bi-metallic film is directly interconnected with theunderlying CNT forest after growth (Figure 1). Such a structure was obtained withcatalyst layer stacks like Cr/Ni, which itself entirely lift-off from the substrateduring the growth. Unlike typical appearance of CNT films, the surface appearsremarkably smooth and shiny metallic. The films can be obtained in a thermalCVD process. The CNT film height and structure can be precisely controlled withCVD parameters. Extensive characterization with techniques like SEM, AFM,XRD, TEM and Raman spectroscopy are presented to enlighten the structuralcomposition, growth properties, and growth mechanisms. Thereby the role of Crwas identified as a co-catalyst supporting the catalytic function of embedded Ninanoparticles. The special structure and properties of such CNT films facilitateimproved fabrication processes and new integration possibilities of CNTs invarious applications. Thus, a freely configurable layer stack can be deposited onan ICNT film without intermixing with the CNTs. For instance, this can simplifythe CNT via fabrication process in ULSI circuits and improve theelectrical/thermal contact at the upper CNT/metal interface. Moreover, the ICNTgrowth allows the fabrication of novel nanostructures with multidirectional grownCNTs in one structure. This can be applied in electronic applications like supercapacitors, NEMS, and different sensors. Different integration approaches andfirst results on those are going to be highlighted. Acknowledgement Prof. M.Albrecht (Surface and Interface Physics / TU Chemnitz), Prof. D.R.T. Zahn(Semiconductor Physics / TU Chemnitz), Prof. Hietschold (Solid SurfacesAnalysis Group / TU Chemnitz) are gratefully acknowledged for helpful support.This work was financially supported by the German Research Foundation (DFG)in the International Research Training Group 1215 “Materials and Concepts forAdvanced Interconnects”.

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Figure 1:SEM cross section of the nanostructure showing CNT forests interlinked with a thin bi-metallic catalystlayer on top of the CNTs

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TuP5-16 | Topological and magnetic confinement in graphenebilayer quantum rings (#499)Milton Pereira 1, Leandro Xavier1, Gil de Aquino Farias1, François Peeters2

1Universidade Federal do Ceara Physics, Fortaleza, Ceara, Brazil 2Universiteit Antwerpen Physics, Antwerp, Belgium ContentGraphene, a one atom thick crystal sheet of carbon, has been shown to displaystriking electronic and mechanical properties which are expected to lead to thedevelopment of new devices in the near future. For two coupled graphenesheets, known as bilayer graphene, the electronic structure presentsmodifications due to the weak interlayer interaction, which cause the otherwiselinear dispersion to become approximately parabolic. Another important featureof bilayer graphene is the fact that the electronic dispersion can be made todevelop a gap, either by doping of one of the layers or by the application of anexternal perpendicular electric field. Such gap can be tuned by varying theexternal electric field, which allows for the possibility of tailoring the electronicstructure of BG for the development of devices. Recently it has been shown thatelectrons can be confined in bilayer graphene in antisymmetric potential ”kinks”,i.e., at the interface between two regions of an antisymmetric external electricfield. Here we show results for localized electron and hole states in a ring-shapedpotential kink with magnetic field in biased bilayer graphene. Within thecontinuum description, we show that for sharp potential steps the Dirac equationdescribing carriers close to the K point of the first Brillouin zone can be solvedanalytically for a circular kink/antikink dot with a perpendicular magnetic field. Wealso consider the case of a quantum ring created by a circularly symmetricpotential described by a kink and an antikink. We show the energy spectrum asfunction of the potential height, magnetic field and geometric parameters of thesystem.

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TuP5-17 | Effect of Lateral Strain on the Performance of SingleLayer Graphene Field Effect Transistors (#530)Satofumi Souma , Yusuke Ohmi, Matsuto OgawaKobe University Department of Electrical and Electronic Engineering, 1-1Rokkodai, Nada, Kobe 657-8501, Japan ContentThe long-continued advance in LSI technologies has been based onminiaturization of semiconductor electronic components. As the size of suchdevice approaches around 10 nm, however, such miniaturization itself become acause of reducing the device performance because of various leakage currentand short channel effects, meaning the practical downsizing limit of conventionalsemiconductor devices. Various possible scenarios for post-miniaturization havebeen proposed so far including nanowire field effect transistors (FETs), band-to-band tunneling FETs, carbon based devices, and so on. Among such newstrategies the graphene FET is particularly important because of its high mobilityand high thermal conductivity. Nevertheless, absence of the band gap ingraphene sets limitations on its practical applications. As methods of creating thebandgap, various approaches have been proposed in single or bi-layergraphene. The use of graphene-substrate interaction, graphene nanoribbon bylateral confinement, and breaking the inversion symmetry in bi-layer grapheneare well known examples. Recently, the possibility of using lateral strain forcreating the bandgap in single layer graphene (SLG) has also been pointed out[1,2]. Among various types of lateral strain, the sheer strain is especiallyimportant since it allows SLG to possess the bandgap with the experimentallyachievable strain [2]. While it has been predicted theoretically that the lateralstrain can actually induce the bandgap in bulk two-dimensional SLG, the effect ofsuch strain on the switching behavior of SLG based field effect transistor (SLG-FET) has not been understood in detail yet. With such motivation, in this work westudy numerically the effect of various types of lateral strain on the performanceof the SLG-FETs, with the special attention to the dependences on the channellength, the type of strain, and the strength of the strain. Our simulationsemploying the empirical tight-binding method and the non-equilibrium Green’sfunction method have shown that the switching behavior SLG-FET can bedramatically modulated by applying the lateral strain, especially when the zigzagstrain (i.e., strain along the zigzag direction in SLG) or the sheer strain is appliedto SLG, exhibiting the clear switch-off regime with the definite threshold voltage ifthe channel length is larger than an appropriate value. The dependence of thesub-threshold swing on the strain value is also clarified. References[1] V. M. Pereira and A. H. Castro Nero, Phys. Rev. B 80, 045401 (2009). [2] G Cocco, E. Cadelano, L.Colombo, Phys. Rev. B 81, 241412(R) (2010).

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Fig. 1:Drain current is plotted as a function of gate voltage for various strength of the strain applied along thezigzag direction.

Fig. 2:Drain current is plotted as a function of gate voltage for various strength of the strain applied along thearmchair direction.

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TuP5-19 | Voltage-driven ring confinement in graphene:tailoring the electronic structure (#58)Leonardo Villegas-Lelovsky1, Carlos Trallero-Giner 1,2, Victor Lopez-Richard1,Gilmar E. Marques1

1Universidade Federal de Sao Carlos Departamento de Fisica, Sao Carlos,13.565-905, Brazil 2Havana University Faculty of Physics, 10400 Havana, Cuba ContentWe have systematically studied the single-particle states in quantum rings (QR)produced by a set of cylindrical gates over a graphene sheet placed on asubstrate (Fig. 1 (a)). The resulting electrostatic potential is shown in Fig. 1(b) and modeled as displayed in Fig 1 (c). This confinement profile and theinteraction between the graphene layer and the substrate [1] are consideredwithin the Dirac Hamiltonian equation in the framework of the envelope functionapproximation. Our simulations allow the microscopic mapping of the character ofthe electron and hole quasi-particle solutions according to the applied voltage.Contrasting behaviors are obtained when comparing the results for repulsive andthe attractive electrical contacts as well as for varying the strength of thegraphene-substrate coupling parameter. By mapping the energy-phasediagrams we have identified seven types of solutions that can be described as: (i)tunneling states from the QR barrier-core, (ii) energy gap due to forbidden phaseor semiconducting transition, (iii) bound states in the rim, (iv) continuum states ortraveling waves, (v) ionization phase from the QR barrier-core, (vi) core-rimbound states, and (vii) bound sates in the QR barrier-core. The classification ofpseudo-relativistic states in terms of system parameters are presented as phase-diagrams. We describe general conditions to attain and control the appearanceof bound states in the QRs as function of the external parameters within realisticranges of controllable variables. The simultaneous characterization of localizedelectron and hole states allows discussing how the optical properties of thisstructure can be tuned by varying the configurations of applied voltages. Asdisplayed in Fig. 1 (d), diferent phases of the electronic states should lead to,respectively, long-wavelength-(solid black arrow), medium-wavelength-(dashedblack arrow) and short-wavelength-(dot-dashed black arrow) interband opticaltransitions between the corresponding mixed, gapless and gaped band states.The inset in Fig. 1 (d) shows the corresponding band diagram of the gapedsystem for Vb = 0. References[1] S.Y. Zhou, G.-H. Gweon, A. V. Fedorov, P. N. First, W. A. De Heer, D.-H. Lee, F. Guinea, A. H. Castro Neto, andA. Lanzara, Nat. Mater. 6, 770 (2007).

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Figure 1:(a) Etched electrostatic gates in a Graphene sheet over a substrate. (b) Realistic confinement potentialprofile. (c) Model profile used in the simulations. (d) Electron (blue curves) and hole (red curves) reducedenergies in a graphene QR.

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TuP5-20 | Controllable growth and field emission of multi-layergraphene/carbon nanotube hybrids (#193)Jian-Hua Deng, Guo-An Cheng Beijing Normal University College of Nuclear Science and Technology, XinjiekouWai Street 19#, Beijing China ContentHybrids consisted of one dimensional (1D) carbon nanotube (CNT) and 2Dgraphene are attractive candidates for novel applications that involve advantagesof the both, such as fabricating electron field emitters which ensure a fullutilization of the large aspect ratio of the CNT and the numerous sharp edges ofthe graphene. We report here a catalyst-free and controllable approach tofabricating multi-layer graphene/carbon nanotube (MLG/CNT) hybrids usingmicrowave plasma enhanced chemical vapor deposition. The MLG/CNT hybridswere fully characterized by SEM, TEM, Raman, and photoelectron spectrometer.The MLG morphology, such as density, size and thickness, shows a strongdependence on the carbon concentration (Cc) that used in its fabrication.Besides, the thickness of amorphous carbon layer on CNT increases with theincreasing Cc, either. We also studied the field emission of the MLG/CNT hybrids,and found that hybrids with a sparse MLG distribution (synthesized with C2H2/H2

= 1/10) which not only reserve the excellent field emitting ability of the CNTs butalso introduce new emission sites from the sharp-edge MLGs present excellentfield emission properties, with low turn-on electric field (0.82 V/µm at 10 µA/cm2)and threshold field (1.32 V/µm at 10 mA/cm2), larger enhancement factor of~5677, and good stability (~1.20% current degradation in 10 hours), which are farbetter than those of the as-grown CNT arrays and thick MLG densely packedhybrids (synthesized with C2H2/H2 = 3/10, 5/10 and 10/10), suggesting promisingprospects in applications as high-performance field emitters.

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TuP5-21 | Flux Cancelation in Magneto-Resistance of ThinMulti-Walled Carbon Nano-Tubes (#268)Yuichi Ochiai 1, Michio Kida1, Hajime Asano1, Nobuyuki Aoki1, TakeshiNakanishi2, Jonathan P. Bird3

1Chiba University Nano Science, 1-33 Yayoi, Inage, Chiba, Chiba 263-8522,Japan 2AIST, Umezono, Ibaraki, Tsukuba 305-8568, Japan 3SUNY Buffalo Electrical Engineering, Buffalo, New York 14216, United States ContentThe flux cancelation has been observed in the low temperature magneto-resistance (MR) in case of thin multi-walled carbon nano-tubes (CNTs), [1]. Inorder to clarify the flux cancelation, angular dependent MR has been studied inthin multi- walled carbon nano-tubes (TMWNTs). Based on the theoreticalstudies of the carrier scattering behaviors in the CNT [2] and the flux cancelationin one-dimensional transport in CNT, we can analyze an intrinsic carrierscattering mechanism by means of the angular dependence on the applied fielddirection based on the longitudinal axis of the TMWNT, from parallel toperpendicular directions of the magnetic fields. Therefore, three kinds of theTMWNT samples are prepared in which one is the standard 4 terminal leads andother two have the 8 or 6 terminal leads in order to observe length dependenceof the carrier scattering properties. The results of the temperature dependencein the many choices of the transport path give us important information on therelationship between carrier scattering and flux cancelation. Also, in a few cases,the background component of the MR shows a particular oscillation componentthat can be explained in terms of quantum interference via the Aharanov-Bohmor Aronov-Altshuler-Spivak effect. In addition, we can also discuss theappearance of a positive MR that has been clearly observed in the perpendiculardirection into the TMWNT axis and strongly depended on the magnetic fielddirection. This work is supported in part by Grants-in-Aid for Scientific Researchfrom JSPS (19054016, 19204030 and 16656007), also JSPS Core-to-CoreProgram, and in partly supported by Global COE program at Chiba University(G-03, MEXT) and also by international student exchange between ChibaUniversity and SUNY Buffalo. References

1. M-G. Kang et al., PRB, B77, 113408, 2008.

2. T. Nakanishi and T. Ando, J. Phys. Soc. Jpn., 74, 3027, 2005.

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Fig. 1:Angular dependence of the MR in MWNT has been analyzed by tuning from the parallel field to theperpendicular field directions to the tube axis. In the low temperature MR at 1.5K, four-terminal resistancemeasurements were performed with each angle.

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TuP5-22 | Relaxation dynamics in epitaxial grapheneinvestigated in the whole infrared spectral range (#295)Stephan Winnerl 1, Fabian Göttfert1, Martin Mittendorff1, Harald Schneider1,Manfred Helm1, Milan Orlita2,3, Marek Potemski2, Torben Winzer4, AndreasKnorr4, Ermin Malic4, Michael Sprinkle5, Claire Berger5, Walter A. de Heer1

1Helmholtz-Zentrum Dresden-Rossendorf Institute of Ion Beam Physics andMaterials Research, Bautzner Landstrasse 400, 01328 Dresden, Germany 2Grenoble High Magnetic Field Laboratory CNRS-UJF-UPS-INSA, 38042Grenoble, France 3Charles University Faculty of Mathematics and Physics, Ke Karlovu 5, 12116Praha, Czech Republic 4Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany 5Georgia Institute of Technology, Atlanta, 30332, United States ContentAs a gapless material with linear dispersion graphene is of great interest for theinfrared spectral range. In this study we investigate the carrier relaxationdynamics of graphene in a wide spectral range from the near to the far-infrared,covering more than two orders of magnitude in photon energy. The samples forthis study are epitaxially grown graphene layers on the carbon-terminated face ofSiC, which behave essentially like a stack of electronically uncoupled layers. Inthe near infrared (NIR) spectral range (photon energy 0.41 eV – 1.5 eV)degenerate and two-color experiments were performed. In the mid (MIR) and farinfrared (FIR) range (photon energy 10 meV – 250 meV) degenerate pump-experiments were carried out employing the free-electron laser FELBE as asource. In the NIR range pump-induced transmission was observed in two-colorexperiments with both red and blue shifted probe radiation. The signals in case ofthe blue shifted probe are evidence for a hot carrier distribution. Thethermalization process is beyond the temporal resolution of our experiment (~100 fs in the near infrared). The observed decay times are in the range of 2 – 4ps. In the MIR range we observe a significant increase of the relaxation time asthe photon energy is decreased to values below the optical phonon energy (~200meV). These experiments are complemented by microscopic theory based onthe density matrix formalism [1]. The theory reflects the trends seen in theexperiment well. It reveals the contribution of Coulomb scattering as well as therole of both optical and acoustic phonons in the observed dynamics. In the FIRrange an unexpected change from enhanced transmission to enhancedabsorption is found (cf. Fig. 1). It is caused by an interplay of interband and intrabandprocesses. For photon energies above twice the value of the Fermi energy,bleaching of interband transitions results in pump-induced transmission. Forsmaller photon energies, however, interband transitions are not possible. Hereintraband transitions cause a heating of the carrier distribution, which is responsiblefor the intraband absorption. References[1] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C.Berger, W. A. de Heer, H. Schneider, and M. Helm, Phys. Rev. Lett. 107, 237401 (2011).

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Fig.1:Measured pump-induced transmission for two photon energies E and almost similar pump fluencies F.

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TuP5-23 | Ab-Initio investigation of one dimensional superlatticesof graphene-like honeycomb crystals (#420)Lars Matthes 1,2, Karsten Hannewald1, Friedhelm Bechstedt1

1Universität Jena Institut für Festkörpertheorie und -optik, Max-Wien-Platz 1,07743 Jena, Germany 2Università di Roma Dipertimento di Fisica, via della Ricerca Scientifica 1, 00133Rome, Italy ContentSince the two-dimensional material graphene was rediscovered in 2004 by Geimet al. there has been a strong interest in tailoring its properties in order to achievea broad usability in manifold applications. Furthermore, due to masslesselectrons graphene is also a playground for theoretical physicists for testing basicphysical theories of high energy physics in a solid state system. Here we presentfirst-principles studies of electronic and structural properties of various graphene-based one-dimensional superlattices including modifications of pristine grapheneby means of hydrogen adsorption, substitution of carbon atoms with boron-nitrideas well as a heterostructure including the very recently discovered silicene. [1]We discuss the occurrence of an electronic band gap in these systems. We focusin particular on the interesting case of graphene-silicene superlattices whichprovides insights to the physics of heterostructures consisting of materials whereboth may contain massless Fermions and a vanishing electronic gap around theFermi-energy. Finally, we discuss the novel properties of the 1D interfacesbetween those 2D crystals. References[1] B. Lalmi et al., Applied Physics Letters 97, 223109 (2010)

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TuP5-24 | Study of Electro-mechanical Vibrations in CarbonNanotube in The Configuration Clamped-Clamped (#456)Giovany Ruiz1,2, Angela Camacho 1

1Universidad de los Andes Departamento de Física, Carrera 1 # 18 A -10,110221 BOGOTA, Colombia 2Universidad de los Andes Departamento de Física, Carrera 1 # 18 A -10,110221 BOGOTA, Colombia ContentIn this work, we study the vibration behavior of a clamped-clamped carbonnanotube (CNT) flexure element that can guide motions innanoelectromechanical systems. It is known that this compliant elementexperiences strain stiffening that leads to localized bending deformations in theCNT. As such, linearized macro-scale elastomechanic models fail to accuratelypredict the static response of the beam, we approach the problem by find out thefield distribution along the tube solving numerically the Laplace equation by usinga finite element method for a CNT actuated by an electrode underneath it with agap width d. We also calculate the fundamental natural frequency of a CNT in theconfiguration Clamped-Clamped in the presence of a static electric field bysolving the Euler-Bernoulli equation taking into account the Maxwell tensorcomponents along the surface. We follow the behavior of the frequency of theCNT as function of the external voltage finding a maximum of the frequency foreach CNT and the pull-in voltage when the frequency vanishes. In addition, westudy the dependence of the fundamental natural frequency as the distance dbetween CNT and cathode is changing under constant voltage. Our resultsdescribe the electric response of a Clamped-Clamped CNT that can be used todesign an electro-mechanical sensor.

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TuP5-25 | Wave packet scattering in graphene under (pseudo)magnetic fields (#505)Andrey Chaves 1, Diego Rabelo Costa1, Lucian Covaci2, François Peeters2, Gilde Aquino Farias1

1Universidade Federal do Ceará Departamento de Física, Fortaleza, Ceará,Brazil 2University of Antwerp Department of Physics, Antwerp, Belgium ContentGraphene has been attracting much interest due to its unique electronicproperties, arising from its singular energy spectrum, where it is demonstratedthat low energy electrons, in the vicinity of the K and K' points of its first Brillouinzone, behave as massless dirac particles, with an almost linear dispersion. [1]Different edge types in graphene nanostructures, such as dots and ribbons, playan important role on the electrons scattering in these systems, defining thecharacter of the scattering as inter-valley or intra-valley. The character of thescattering has an important influence e.g. in the Raman spectrum of thesesystems, and have even been suggested as an efficent mechanism to producevalley filtering, [2] which stimulates us to theoretically study this topic in greaterdetail. Recent papers in the literature have also shown that, under specific strainconfigurations, electrons in graphene behave as if they were under an appliedmagnetic field, which points to opposite directions for each valley K and K', sothat the time-reversal symmetry of the crystal as a whole is preserved. [3] In thepresent work, the scattering of a Gaussian wavepacket by defects, as well as bythe armchair and zigzag edges in a graphene squared dot, is theoreticallyinvestigated by numerically solving the time dependent Schrodinger equation forthe tight-binding model Hamiltonian. Our theory allows one to observe theevolution of the packet in the reciprocal space, where the possibility of scatteringwithin the same valley, or between different valleys, depending on the type of theedge or defect, is analyzed. In the presence of an external magnetic field, thewell know skipping orbits are observed in the sample edges. A comparison ismade between these orbits and the trajectories obtained in the case of a pseudo-magnetic field, induced by non-uniform strain, where the differences andsimilarities between the pseudo and external magnetic fields effects on theelectrons motion in graphene are discussed. References[1] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, and A. A. Firsov,Science 306, 666 (2004). [2] A. Rycerz, J. Tworzydło, and C. W. J. Beenakker, Nat. Phys. 3, 172 (2007). [3] F.Guinea, M. I. Katsnelson and A. K. Geim, Nat. Phys. 6, 30 (2010).

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TuP5-26 | Fabrication of Graphene and Graphite Thin Filmsfrom Organic Solutions (#524)Mikihiro Kato , Keiichi Ikegami, Susumu Harako, Toshiki Ohkane, TatuyaKobayashi, Xinwei ZhaoTokyo University of Science ADL and Department of Physics, 1-3 Kagurazaka,Tokyo, Shinjuku-ku 162-8601, Japan ContentGraphene has attracted a lot of attentions since the report by Novoselov et al. in2004 [1]. Graphene is mechanically strong, and has good flexibility, high thermalresistance and very high electron mobility at room temperature (RT). Most purecrystal graphene was made from peeling graphite by using Scotch tape. Themost important research for mass production is how to fabricate uniformed andcontrollable large graphene sheet. In this work, we propose a method to makegraphite thin layer by using deposited organic solution which includes benzenerings. The process has two steps: coating the organic solution on SiO2

substrates and post heat treating. The organic solutions used in CVD processvaporize so fast, so that our study chose benzene ring contained organic solutionas the starting material. A Si (100) wafer with 300 nm thick oxide layer was usedas the starting material. Pure Ni metal having thickness of 100 nm wasdeposited on the SiO2 in vacuum. Next, a saturated acetone:OrangeII (AcidOrange 7; C16H11N2NaO4S) solution was coated on the sample surface. Afterword, the sample was annealed at 850 oC for 5 min in vacuum. Then, thesample was evaluated by SEM-EDS, AFM and Raman spectroscopy. Relativelylarge thin graphite layers with size ranged from several ten to hundredmicrometers have been formed on the Ni surface. These graphite layers wereinvestigated by the microscopic Raman spectroscopy. Two Raman peaks wereknown for graphite materials [2]: D-band originates from the disorder phase ofgraphite and appears at around 1350 cm-1 under laser excitation at 532 nm. G-band originates from vibration Raman mode and appears at around 1585 cm-1. An intense G-band indicates good crystallinity of the graphite thin layer. The G /D intensity ratio is a factor of characterizing the graphite crystallization. Furthermore, an intense 2D-band at around 2700 cm-1 indicates the formation ofsingle layer grapheme. Our results showed a similar Raman spectra as that inRef. 1, and it was also similar to the graphene sheet formed by peeling highlyoriented pyrolytic graphite for comparison. The AFM observation suggested thesame conclusion, too. We have fabricated graphene sheet and graphite thinlayers by resolving organic solutions on Ni/SiO2 surface. Our results suggestedthat this method might be a potential way to fabricate large graphene sheet easilywith low cost. References[1]. K. S. Novoselov et al., Science 306, 666 (2004). [2]. R. Saito et al., PhysRevLett. 88, 02740 (2001).

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TuP5-27 | Resonant Cavity Enhanced Graphene Photodetectors(#538)Marco Mercurio Furchi 1, Alexander Urich1, Andreas Pospischil1, Govinda Lilley1,Karl Unterrainer1, Hermann Detz2, Pavel Klang2, Aaron Maxwell Andrews2,Werner Schrenk2, Gottfried Strasser2, Thomas Mueller1

1Vienna University of Technology Photonics Institute, Gußhausstraße 27-29,1040 Wien, Austria 2Vienna University of Technology Center for Micro- and Nanostructures,Floragasse 7, 1040 Wien, Austria ContentGraphene, a novel two-dimensional carbon allotrope, is reported to haveextraordinary electrical and optical properties [1]. Graphene basedphotodetectors [2] show a nearly wavelength independent sensitivity [3] and havebeen proven to work at high speeds [4]. Graphene has a high optical absorptioncoefficient, which is independent of wavelength, but due to the thickness of only0.335 nm the optical absorption in graphene is weak (≈2.3 %). To overcome thisproblem, we integrated a graphene photodetector into an optical cavity [5] (seeFigure 1). This allows us to increase the absorbance by spatially concentratingthe energy of the incident light on the graphene sheet. As design wavelength wehave chosen 850 nm, because of its wide spread use in optical communications.We used two distributed Bragg-mirrors, consisting of quarter-wavelength thicklayers of alternating materials with varying refractive indices, as a high-finesseplanar cavity. Bragg mirrors were chosen, because unlike for metal mirrors, thereflectivity can be well controlled and reaches values up to nearly unity. A Si3N4

buffer layer ensures that the maximum of the field amplitude occurs at theposition where the graphene sheet is placed. Numerical simulations were used todetermine the optimal design. Reflectivity measurements show that at the cavityresonance more than 60 % of the light is absorbed by the graphene layer, whichis a 26-fold enhancement compared to the 2.3 % absorption for freestandinggraphene. Using a tunable laser source and a two dimensional stage, spatiallyresolved photocurrent images were acquired. Subsequently, the spot of the laserbeam was aligned to the photocurrent maximum and wavelength dependentmeasurements were carried out. The experimental results showed an increase ofresponsivity from less than 1 mA/W to 21 mA/W, which makes such devicespromising for future optoelectronic applications. References[1] Bonaccorso, F.; Sun, Z.; Hasan, T.; Ferrari, A.C. Nature Photon. 2010, 4, 611–622. [2] Mueller, T.; Xia, F.;Avouris, Ph. Nature Photon. 2010, 4, 297–301. [3] Nair, R.R.; Blake, P.; Grigorenko, A. N.; Novoselov, K. S.; Booth,T. J.; Stauber, T.; Peres, N. M. R. ; Geim, A. K. Science 2008, 320, 1308. [4] Urich, A.; Unterrainer, K.; Mueller, T.Nano Lett. 2011, 11, 2804–2808. [5] Furchi, M.; Urich, A.; Pospischil, A.; Lilley, G.; Unterrainer, K.; Detz, H.; Klang,P.; Andrews, A.M.; Schrenk, W.; Strasser, G.; and Mueller, T. Arxiv:1112.1549v1, 2011.

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Figure 1:Schematic illustration of a resonant cavity enhanced graphene photodetector.

199

TuP5-28 | Gated Graphene for THz Plasmonics(#558)Stefan Badescu , Robert Fitch, Dennis Walker, Justin Cleary, JoshuaHendricksonAir Force Research Laboratory, Wright Patterson AFB, Ohio 45433, UnitedStates ContentGraphene was identified as a tunable, low-loss material for plasmonicapplications at room temperature [1,2]. Understanding the limitations of its opticalconductivity is essential for possible opto-electronic applications [3,4,5]. Wepresent a model of plasmons in gated graphene, where top split gates localizeTHz-range plasmons under each gate and at p-n junctions induced by two gates.The former type of plasmons have similarities with plasmons in graphenemicroribbons [2]. The latter has been anticipated theoretically [6]. We describethe plasmonic spectral and amplification properties taking intoaccount quantitatively the equilibrium charge density and the injection currents atp-n junctions and in gated regions of graphene. To describe density wavesaccurately, the dielectric function goes beyond the Drude model by incorporatinggraphene optical phonons and electron-hole pairs, and coupling to the SiCsubstrate. We discuss the required voltages, channel and gate sizes necessaryfor THz detection and possibly emission through population inversion next tographene p-n junctions [7]. Plasmons at p-n graphene junctions are candidatesfor channels in electro-optical switches and also raised interest for room-temperature THz sensors and sources [3,4,5]. Population inversion and THzamplification has been demonstrated in graphene via optical pumping butrequires large optical setups [3]. Plasma instabilities and THz amplification hasbeen demonstrated in GaN HEMTs but displayed broad peaks. Using a set ofgates creates conditions for both plasmon types in a single, compact all-electricalsystem, with a large bandwidth tunability provided by gating. References[1] A. Boltasseva and H. A. Atwater, "Low-Loss Plasmonic Metamaterials," Science, vol. 331, p. 290, 2011 [2] L. Juand al., "Graphene Plasmonics for Tunable THz Metamaterials," Nature Nanotechnology, vol. 6, p. 630, 2011 [3] H.Karasawa et al., "Observation of Amplified Stimulated Terahertz Emission from Optically Pumped HeteroepitaxialGraphene-on-Silicon Materials," J. Infrared Mm. THz Waves, vol. 32, p. 655, 2011 [4] V. Ryzhii et al., "Toward thecreation of terahertz graphene injection laser," Journal of Applied Physics, vol. 110, p. 094503, 2011 [5] J. A. Dionneet al., "PlasMOStor: A Metal-Oxide-Si Field Effect Plasmonic Modulator," Nano Letters, vol. 9, no. 2, p. 897, 2007. [6]E. G. Mishchenko, A. V. Shytov and P. G. Silvestrov, "Guided Plasmons in Graphene p-n Junctions," PhysicalReview Letters, vol. 104, p. 156806, 2010. [7] F. Rana, "Graphene THz Plasmon Oscillators," IEEE Transactions onNanotechnology, vol. 7, no. 1, p. 91, 2008.

200

TuP6-1 | Donor D2+ in vertically coupled quantum dots (#73)

Ramon Manjarres-Garcia1, Gene E. Escorcia-Salas1, Ilia Davidovich Mikhailov2,José Sierra-Ortega 1

1Group of Investigation in Condensed Matter Theory Universidad del Magdalena,Carrera 32 No 22 - 08, 2-1-21630 Santa Marta, Colombia 2Universidad Industrial de Santander, A.A. 678 Bucaramanga, Colombia ContentRecently, it has been proposed to use the singly ionized double donor system(D2

+) confined in a single semiconductor quantum dot [1] or ring [2] as anadequate microscopic two-level system as the functional part in a wide range ofdevice applications, including spintronics, optoelectronics, photovoltaics, andquantum information technologies. This system encodes the logical informationeither on the spin or on the charge degrees of freedom of the single electron andallows us to manipulate conveniently its molecular properties, such as the energysplitting between the bonding and antibonding lowest-lying molecular-like statesor the spatial distribution of carriers in the system [3]. We show that similarproperties should have the singly ionized double donor system (D2

+) confined invertically coupled quantum dots. The electronic states of a singly ionized doubleon-axis donor complex (D2

+) confined in two identical vertically coupled axiallysymmetrical quantum dots in a threading magnetic field are calculated. Thesolutions of the Schrödinger equation are obtained by a variational separation ofvariables in the adiabatic limit. Numerical results are shown for bonding and anti-bonding lowest-lying molecular states corresponding to different quantum dotsmorphologies, dimensions, separation between them, thicknesses of the wettinglayers and the magnetic field strength. References1. J. L. Movilla, A. Ballester, and J. Planelles, Phys. Rev. B 79, 195319 (2009); 2. W. Gutiérrez, L.F. García, I.D.Mikhailov, Physica E 43 (2010) 559 3. M. J. Calderón, B. Koiller, and S. Das Sarma, Phys. Rev. B 75, 125311 (2007);A. V. Tsukanov, Phys. Rev. B 76, 035328 (2007); L. A. Openov, Phys. Rev. B 70, 233313 (2004); B. Koiller, X. Hu,and S. Das Sarma, Phys. Rev. B 73, 045319 (2006); S. D. Barrett and G. J. Milburn, Phys. Rev. B 68, 155307(2003).

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TuP6-2 | Trion X+ in Vertically Coupled Type II Quantum Dots inThreading Magnetic Field (#74)Sindi Horta-Piñeres 1,2, Gene E. Escorcia-Salas2, Ilia Davidovich Mikhailov3, JoséSierra-Ortega2

1Universidad de Sucre, Cra 28 #5-267, Sincelejo, Colombia 2Group of Investigation in Condensed Matter Theory Universidad del Magdalena,Carrera 32 No 22 - 08, 2-1-21630 Santa Marta, Colombia 3Universidad Industrial de Santander, A.A. 678 Bucaramanga, Colombia ContentWe analyze the energy spectrum of a positively charged exciton confined in asemiconductor heterostructure formed by two vertically coupled axiallysymmetrical type II quantum dots located close to each other. The electron in thestructure is mainly located inside the dots while the holes generally are placed inthe exterior region close to the symmetry axis. The solutions of the Schrödingerequation are obtained by a variational separation of variables in the adiabaticlimit. Numerical results are shown for bonding and anti-bonding lowest-lying ofthe trion states corresponding to different quantum dots morphologies,dimensions, separation between them, thicknesses of the wetting layers and themagnetic field strength.

Fig. 1.:Scheme of a trion X+ confined in a type II vertically coupled quantum dots

202

TuP6-3 | Magnetoexciton in Vertically Coupled Type II QuantumRings (#113)Johonfri Mendoza 1,2, Gene E. Escorcia-Salas1, José M. García-Díaz1, IliaDavidovich Mikhailov3, José Sierra-Ortega1

1Group of Investigation in Condensed Matter Theory Universidad del Magdalena,Carrera 32 No 22 - 08, 2-1-21630 Santa Marta, Colombia 2Universidad de la Guajira, Km 5 Vía a Maicao, Riohacha, Colombia 3Universidad Industrial de Santander, A.A. 678 Bucaramanga, Colombia ContentWe analyze a Wannier–Mott exciton in which the electron is mainly constrainedto move inside vertically coupled InxGa1-xAs self-assembled quantum ringstunneling between them and the hole moves in the surrounded GaAs matrixaccording to the model schematically presented in Fig. 1. The solutions of thetwo-particle Schrödinger equation are obtained by a variational separation ofvariables in the adiabatic limit. Numerical results for the lower energies asfunctions of the separation between rings and the strength of the magnetic fieldapplied along the symmetry axis are shown for bonding and anti-bonding of theexciton states for different rings and the wetting layer thicknesses. For a largeseparation between rings, the orbital Zeeman contribution prevails leading to thewell-known Aharanov–Bohm spectrum, but it slowly decreases as theoverlapping between rings increases.

Fig. 1.:Scheme of an exciton confined in a type II vertically coupled quantum rings

203

TuP6-4 | Double donor complex in vertically coupled quantumdots in threading magnetic field (#114)Ramón Manjarres-García1, Gene E. Escorcia-Salas 1, Javir Manjarres-Torres1, IliaDavidovich Mikhailov2, José Sierra-Ortega1

1Group of Investigation in Condensed Matter Theory Universidad del Magdalena,Carrera 32 No 22 - 08, 2-1-21630 Santa Marta, Colombia 2Universidad Industrial de Santander, A.A. 678 Bucaramanga, Colombia ContentWe consider a model of hydrogen-like artificial molecule formed by two verticallycoupled quantum dots in shape of axially symmetrical thin layer whose profile isgiven by the Cauchy curve with on-axis single donor impurity in each of them andwith the magnetic field directed along the symmetry axis. In order to separatethe rapid electrons motion in vertical direction from slow in-plane motion we usethe adiabatic approximation [1] and show that the analysis of the lower energylevels of this system is reduced to an exactly solvable model of a two-electronquantum dot with parabolic confinement [2]. We present numerical results forenergies of some low-lying levels as functions of the magnetic field strength fordifferent quantum dots heights, radius and separations between them. Theevolution of the Aharonov-Bohm oscillations of the energy with the increase ofthe separation between dots as the artificial hydrogen-like molecule transforms intwo independent artificial hydrogen-like atoms is analysed References[1] F. M. Peeters and V. A. Schweigert, Phys. Rev. B53, 1468, 1996; I. D. Mikhailov, J. H. Marín, and F. García,phys. stat. sol. (b) 242, No. 8, 1636–1649 (2005) [2] D. Pfannkuche, V. Gudmundsson, and P. Maksym, Phys. Rev. B47, 2244 (1993).; J. L. Zhu, J. Z. Yu, Z. Q. Li, and Y. Kawazoe, J. Phys: Condensed Matter 8, 7857 (1996).; [12] I. D.Mikhailov and F. J. Betancur, phys. stat. sol. (b) 213, 325 (1999).

204

TuP6-5 | Aharonov-Bohm oscillation modes in non-uniformnanoring under a lateral electric field (#143)Jairo Humberto Marin Cadavid1, Ilia Davidovich Mikhailov2, Willian Gutiérrez Niño2

1Universidad Nacional de Colombia Antioquia, 05001000 Medellin, Colombia 2Universidad Industrial de Santander Santander, 68001000 Bucaramanga,Colombia ContentLow-lying states of a narrow one-electron nanoring with variable thickness in thepresence of a threading magnetic and a lateral electric fields are analysed byusing the adiabatic approximation in the framework of the functional derivativetechnique [1-4]. In this technique the problem is reduced to a one-dimensionalSchrödinger equation that describes the rotation of the electron along the ring inan axially non-homogeneous effective field whose potential depends on both thevariation of the nanoring thickness and the external electric and magnetic fields. We solve this equation by using the Fourier method and present novel curves forenergies of lower levels and the magnetization as functions of the magnetic andelectric fields for structures with different profiles given by periodicaldependencies of the ring thickness on the azimuthal angle presentedschematically in Fig. 1. We show that the electronic properties of narrownanorings are very sensitive to both the external electric field and the structuralnon-homogeneity. Particularly, the non-homogeneous height of the ring and thein-plane electric field provide each one the electron localization and a quenchingof the Aharonov Bohm oscillations corresponding to states with the lowerenergies, but if they act together the oscillations reinforcement instead of theirquenching can be achieved. This opens a new possibility to control nanoringproperties by external electric field. References1. L. Wendler and V. M. Fomin, Phys. Rev. B51,17814 (1995) 2. Y. V. Pershin and C. Piermarocchi, Phys. Rev. B72, 195340 (2005) 3. A. Bruno-Alfonso and A. Latgé, Phys. Rev. B 77, 205303 (2008) 4. I. D. Mikhailov,J. H. Marín,and F. García, Phys. Stat. Sol. (b) 242, 1636 (2005)

Figure 1:Images of nanorings with different profiles

205

TuP6-6 | Interfacial connement in core-shell nanowires due tohigh dielectric mismatch (#148)Teldo Anderson da Silva Pereira 1, Ariel Adorno de Sousa2, Andrey Chaves2,Jeanlex Soares de Sousa2, Gil de Aquino Farias2

1Universidade Federal de Mato Grosso Instituto de Física, Av. Fernando Correiada Costa 2367 Bloco F, Cuiabá, Mato Grosso, 78060900, Brazil 2Universidade Federal do Ceará Departamento de Física, Campus do Pici CaixaPostal 6030, Fortaleza, Ceará, 60455-900, Brazil ContentWe theoretically investigate the role of the dielectric mismatch between materialson the energy levels and recombination energies of a core-shell nanowire. Ourresults demonstrate that when the dielectric constant of the core material is lowerthan that of the shell material, the self-image potential pushes the charge carrierstowards the core-shell interface, in such a way that the ideal confinement modelis no longer suitable. The effects of this interfacial confinement on theelectronic properties of such wires, as well as on its response to appliedmagnetic fields, are discussed.

206

TuP6-7 | Exciton-related nonlinear optical properties in strainedGaN/InN quantum wells under the effects of intense laser fields(#157)Carlos M. Duque1, Miguel E. Mora-Ramos2, Carlos A. Duque 1

1Universidad de Antioquia Instituto de Física, AA 1226, Medellin, Colombia 2Universidad Autónoma del Estado de Morelos facultad de Ciencias, Ave.Universidad 1001, 62209 Cuernavaca, Mexico ContentInGaN-based systems have revealed high prospect for applications inoptoelectronics. Although the hexagonal allotropic form is the one mostcommonly considered, the quantum nanostructures based on zincblende III-Vnitrides are also promising systems. In this work, we study the nonlinear opticalabsorption and the generation of second and third harmonics associated toexciton states in strained zincblende InGaN/InN quantum wells using avariational technique. The system will be considered under the action of intenselaser fields with the incorporation of hydrostatic pressure and stationary electricfields as additional external probes. The influence of these effects on each of thenonlinear optical properties is discussed in detail.

207

TuP6-8 | Inelastic light scattering by 2D electron system withSO interaction (#159)Alexander Chaplik1,2, Lev Magarill 1,2, Ritta Vitlina1

1Institute of Semiconductor Physics, Siberian Branch, Russian Academy ofSciences, 13 prospect Lavrent'eva, 630090 Novosibirsk, Russia2Novosibirsk State University, 2, Pirogova str., 630090 Novosibirsk, Russia ContentInelastic light scattering by electrons of 2D system with taking into account theRashba spin-orbit interaction (SOI) in the conduction band is theoreticallyinvestigated. The case of resonance scattering (frequencies of incident andscattered light are close to the effective distance between conduction and spin-split-off bands of the semiconductor A3B5 -type) is considered. Taking intoaccount SOI substantially changes the spectrum of inelastic light scattering. Anew peak (of a nontrivial shape) appears with the frequency shift ω equal to thespin splitting at Fermi momentum pF. As opposed to the case of SOI absence theplasmon peak in scattering occurs even at strictly perpendicular polarizations ofthe incident and scattered waves. Under definite geometry one can observe thespectrum features conditioned by only single-particle transitions. The polarizationdependencies are changed qualitatively. In the general case of ellipticallypolarized incident and/or scattered light the amplitude of plasmon peak turns outto be sensitive to the sign of the SOI coupling α. At last, the left-right symmetry ofcircularly polarized incident light is violated: the cross section is invariant undersimultaneous change of signs of polarizations and the SOI constant. This allows,in principle, to determine the sign of the Rashba constant experimentally. Numerical calculations were carried out for 2D electron gas at temperature T=0in the scattering geometry when incident and scattered beams make right angle. Figure shows the example of inelastic light scattering spectrum in the mostinteresting case when incident wave has right or left circular polarization whilescattered one is linearly polarized at angle π/4 to the incidence plane. Calculations have been done for the structure InAs/GaSb with α=1.44 ·106 cm/sp,m=0.055 m0, κ =15.69 (κ is the background dielectric constant). The momentumtransfer ħq has been chosen as ħq=0.004 pF (q= q1- q2, q1,2 are the projections ofwave vectors of incident and scattered light onto the system plane). One cansee from the figure that at α >0 the amplitude of plasmon peak for leftpolarization is distinctly larger than for right polarization.

208

Fig.:Dependence of the scattering cross section R on frequency. Solid - incident wave has left polarization,dashed - incident wave has right polarization

209

TuP6-9 | Electronic Transport and Persistent Current in theAharonov-Bohm Rings (#205)Mohammed Shabat 1, Hisham Fayad2

1Islamic University of Gaza Physics, Alazher str., Gaza 108, Egypt 2Alaqsa University, Gaza Strip, Palestinian Authority Physics, Alaqsa st., GazaEgypt ContentIn recent year electronic transport properties of mesoscopic systems in particular,the Aharonov-Bohn rings have been extensively investigated both theoreticallyand experimentally [1-4]. By virtue of highly developed nanotechnology, someinteresting phenomena based on quantum coherence have been observed. Oneof the interesting mesoscopic phenomena predicted by theory [5] and verified byexperiment [6] where the persistent current is flowing in a ring of mesoscopicsize with a piercing magnetic flux through the ring. An additional phase evolutionis involved to satisfy the invariance when a magnetic flux passing through thering. This additional phase evolution is responsible for the persistent current in aclosed ring. The well-known Aharonov-Bohm (AB) effect is the interference dueto the phase difference. The physical basis underlying the persistent current inthe mesoscopic ring with a piercing flux is the difference in phase evolution alongdifferent paths of the ring. The piercing flux and the mesoscopic ring threaded bythis flux are called the AB flux and the AB ring, respectively. A great deal ofresearch has been made on the single ring [7,8] and double-barrier [9] structures.These studies show us that the persistent current can be generated not only inisolated rings but also in the rings with external leads connected to electronreservoirs. In this paper we consider a model of a non-interacting quantum ringsserially connected to a quantum wire in the presence of a uniform magnetic field.We develop a recursive algorithm depends on the matrix approach by usingMAPLE software to compute the electronic transport properties of the proposedstructure. References[1] J. Imry, introduction to Mesoscopic physics (Oxford University Press, New York, (1997) [2] M.Dragoman,and D. Dragoman, Nanoelectronics, Principles and Devices, Nanotechnology series, Artech House, Norwood, (2006)[3] A.A.Gorbatsevich, and V.V.Kapaev, Russian Microelectronics.36, 1, (2007) [4] P.Singha Deo, andA.M.Jayannavar, Modern Physics Lett.B8, 1045-1051, (1993) [5] M.Buttiker, Y. Imry, and R.Landaur, Phys. Lett.96A, 365 (1983). [6] R. A. Webb, S. Washburn, C.P. Umbach, and R.B Laibowitz, Phys. Rev. Lett. 54, 2696(1985). [7] A.M. Jayannavar and P. Sigha Deo, Phys. Rev. B 51, 10175 (1995). [8] M.Pascoud and G.Montambank,Phys. Rev. Lett. 82, 4512 (1999). [9] T. B. Bahder, C.A. Morrison, and I. D. Bruno, Appl. Phys. Lett. 51, 1089 (1987).[10] Ben-Yuan Gu, Phys. Rev., B51, 16840 (1995). [11] W.Park and J. Hong, Phys. Rev. B69, 035319 (2004). [12] J.Yi, J. H. Wei, J. Hong, and S. Lee, Phys. Rev. B65, 033305 (2001). [13] C. Benjamin and A. M. Jayannavar, Cond-mat/ 0110407 V2 (23 Oct.) (2001).

210

TuP6-10 | Dispersion Relation for an Asymmetric Double-Quantum-Dot System in a Normal Magnetic Field (#228)Norman J. M. Horing1, S. L. Horton 2, Hilmi Ünlü3

1Stevens Institute of Technology Department of Physics and EngineeringPhysics, Hoboken, New Jersey 07030, United States2Stevens Institute of Technology Department of Physics and EngineeringPhysics, Hoboken, New Jersey 07030, United States3İstanbul Technical University Department of Physics Engineering, Maslak,34469 İstanbul, Turkey ContentWe examine the subband energy eigenstates of a two-dimensional asymmetricquantum double-dot system embedded in a two dimensional host sheet subjectto Landau quantization. The dispersion relation for the asymmetric quantumdouble-dot subband energies is formulated and examined by analyzing thefrequency poles of the appropriate Green’s function with Landau-quantization-likesplintering of the levels by a magnetic field. The effects of the asymmetry of thequantum dots in regard to their potential well depths are analyzed as functions ofthe well depth difference and dot separation.

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TuP6-11 | Eigen-energy Dispersion Relation of a Kronig-Penney-type Model of a 2D Quantum Antidot Lattice in aMagnetic Field (#229)Norman J. M. Horing1, S. Bahrami 2, Hilmi Ünlü3

1Stevens Institute of Technology Department of Physics and EngineeringPhysics, Hoboken, New Jersey 07030, United States2Stevens Institute of Technology Department of Physics and EngineeringPhysics, Hoboken, New Jersey 07030, United States3İstanbul Technical University Department of Physics Engineering, Maslak,34469 İstanbul, Turkey ContentWe derive the Schrödinger eigen-energy dispersion relation for a twodimensional sheet of electrons in a one dimensional periodic lattice of quantumantidot potential barriers, with a perpendicular quantizing magnetic field. Thissystem is in the nature of a Krönig-Penney model with a high magnetic fieldpresent and we construct the appropriate Green’s function which we use toformulate the dispersion relation for the energy spectrum.

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TuP6-12 | Donor impurity related Linear and nonlinearintraband optical absorption in quantum ring: Effects ofapplied electric field and hydrostatic pressure (#232)M. G. Barseghyan1, R. L. Restrepo2, Miguel E. Mora-Ramos3, A. A. Kirakosyan1,Carlos A. Duque 4

1Yerevan State University Department of Solid State Physics, Yerevan, Armenia 2Escuela de Ingeniería de Antioquia Física Teórica y Aplicada, Medellín,Colombia 3Morelos State University Faculty of Sciences, Cuernavaca, Mexico4Universidad de Antioquia Instituto de Física, Medellín, Colombia ContentThe effects of hydrostatic pressure, in-growth direction applied electric field andasymmetry of confining potential on a donor impurity 1s, 2s-like states togetherwith the linear and nonlinear intra-band optical absorption in a semiconductingquantum ring are studied using the variational method and the effective massapproximation. The energies of the 1s and 2s-states are calculated as a functionof the geometry of the ring, hydrostatic pressure, electric field and parameter ofconfining potential. Besides, the intra-band optical absorption associated withtransitions between ground and first excited states is investigated as a function ofthe incident photon energies, for different values of hydrostatic pressure, electricfield and impurity position. The results show that the energy reveals to be adecreasing function of the hydrostatic pressure, as well as an increasing ordecreasing function of the applied electric field depending on the degree ofasymmetry of the confining potential. In the case of the intra-band absorptioncoefficient the outcome of the calculation show that "blue" and/or "red" shift of themaximum lineshape can be induced as a result of the influences posed by thehydrostatic pressure, the electric field and the asymmetry of the potential. References1. A. Lorke, R.J. Luyken, A.O. Govorov, J.P. Kotthaus, J.M. Garcia, P.M. Petroff, Physical Review Letters 84 (2000)2223. 2. V.A. Harutyunyan, Journal of Applied Physics 109 (2011) 014325. 3. M.G. Barseghyan, M.E. Mora-Ramos,C.A. Duque, Eur. Phys. J. B 84, (2011), 265. 4. Wenfang Xie, Physics Letters A 372 5498, (2008)

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TuP6-13 | Geometrical and applied electric field effects on 1s-like excitonic-related nonlinear optical properties of coupledquantum wells (#238)Guillermo L. Miranda 1, Miguel E. Mora-Ramos2, Carlos A. Duque3

1Escuela de Ingeniería de Antioquia Física Teórica y Aplicada, Medellín,Colombia 2Morelos State University Faculty of Sciences, Cuernavaca, Colombia 3Universidad de Antioquia Instituto de Física, Medellín, Colombia ContentThe epitaxy fabrication technique has permitted the creation of low dimensionalsemiconductor heterostructures in which the charge carriers present a noticeablequantum confinement effect. The optical properties associated to the intersubband transitions associated to the confined carriers have been measured inthis systems and it have been found that they present nonlinear optical propertieswhich are several orders of magnitude greater than in bulk materials. Thesenonlinear properties have attracted the attention of scientists and technologistdue to their application in the development of new optoelectronic devices. Several factors (such as electric and magnetic fields, hydrostatic pressure,presence of impurities and excitons) affect the optical response of the lowdimensional heterostructures and are used to tune and improve the devicesdeveloped from them. In this work, nonlinear optical properties related to 1s-like excitonic transitions of the GaAs-Ga1-xAlxAs coupled double quantum wells,such as, the nonlinear optical absorption (NOA), nonlinear refraction index (NRI),second harmonic generation (SHG) and third harmonic generation (THG) arestudied. Using the effective mass and parabolic band approximations andemploying a variational scheme, the lowest four 1s-like excitonic states of theexcitons in a copled double quantum wells are calculated, and based on these, the (NOA), (NRI), (SHG) and (THG) related to excitonic transitions are obtain fordifferent geometrical configurations and considering the effects of an appliedelectric field.

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TuP6-14 | Acoustic phonon modes and phononic band gaps inGaN/AlN nanowire superlattices (#248)Seiji Mizuno Hokkaido University Department of Applied Physics, Kita-ku, Sapporo 060-8628,Japan ContentThe nanowire superlattices (NWSLs) were shown to be offer unique features,which are different from plain nanowires and quantum wells in their electronicand optical properties [1]. Also, the NWSLs are expected to yield interestingphysical effects on phonon properties. The phonons influence the electronicstates and the transport properties via the electron-phonon interaction. Inaddition, the NWSL can be regarded as a wire-type phononic crystal (WPC), inwhich the phononic band gaps are induced by the periodicity along the wire axis.In a paper [2], we developped a numerical method to derive all phonon modes ina free-standing NWSL of anisotropic material with an arbitrary shape of cross-section. In this paper, as examples, the phonon modes were calculated for therectangular and square cross-section GaAs/AlAs NWSLs composed ofanisotropic materials. Though this result revealed the important aspects ofphonon modes in the NWSLs, it seems to be difficult to design WPCs withcomplete phononic band gaps because in the dispersion relations of theGaAs/AlAs NWSL many subbands are folded into the mini-Brillouin zone and thefrequencies of gaps are different with phonon modes. In addition, the gap widthsare narrow in this NWSL because the acoustic mismatch between the GaAs andAlAs layers is small. To realize the phonon optics devices (e.g., filters, mirrors,and resonators), the NWSLs with large acoustic mismatch would be suitable. Inthe present work, we calculate numerically the dispersion relations andcorresponding displacement fields for a NWSL consisting of GaN and AlN, andwe determine a set of parameters which gives complete frequency gaps. Figure1 shows the calculated phonon dispersion relations. In the present frequencyrange, we can see three different modes, i.e., A1, A2, and E modes. These modeshave features of dilatational, torsional, and flexural modes, respectively. Thedispersion curves corresponding to B1 (stretching) and B2 (shear) modes exist inhigher frequency range. In the present example, we selected R = 5.0 nm and D =25.0 nm so that the first frequency gaps of the A1 and A2 and the second gaps ofthe E1 modes are located in the similar frequency range. The results suggest therealization of the design of the optimized phonon devices for phonon generationor control, such as mirrors, filters, and also resonators. These are expected to beapplicable to the micro/nano electromechanical systems. References[1] M. S. Gudikson L. J. Lauhon, J. Wang, D. C. Smith, and C. M. Lieber, Nature(London) 415, 617 (2002). [2] S.Mizuno and N. Nishiguchi, J. Phys.: Condens. Matter 21, 195303 (2009).

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Fig.1:Phonon dispersion relations of the circular cross-section NWSL consisting of GaN and AlN with R=5nmand D=25 nm. For GaN and AlN layers, cubic lattice are assumed.

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TuP6-15 | Nonlinear optical absorption and optical rectificationin cylindrical quantum dots with asymmetric axial potential:combined effects of hydrostatic pressure, intense laser field,and applied electric field (#483)Alejandro Zapata1, Rubén E. Acosta1, Eduardo Henao1, Elizabeth Aristizabal1,Miguel E. Mora-Ramos2, Carlos A. Duque 1

1Universidad de Antioquia Instituto de Física, Medellín, Colombia 2Morelos State University Faculty of Sciences, Cuernavaca, Mexico ContentDuring the past two decades, intersubband optics has becomes one of the mostimportant research subjects in semiconductor science both from fundamentaland technological point of view. Intersubband transitions have a number ofunique properties that make them very attractive for many device applications.The most significant feature of intersubband transitions is to exhibit largeoscillator strengths which are responsible for the large optical transition dipolemoments. Associated with these dipole moments large optical nonlinearities maybe obtained in semiconductor heterostructures. In this work are studied thenonlinear optical absorption and optical rectification in asymmetrical GaAs-Ga1-

xAlxAs cylindrical quantum dots with the use of the effective mass approximation,the compact-density matrix approach, and an iterative method. The influences onthese properties of the application of a nonresonant intense laser field, a staticelectric field along the growth direction of the cylinder, and hydrostatic pressureare particularly considered. This study considers the hydrostatic pressureinduced Γ-X crossover of the conduction band. Numerical results presented for atypical cylindrical quantum dot show that higher order optical effects areconsiderably sensitive to intense laser field and can be adjusted by a correctchoice of asymmetry parameters of the potential via the applied electric field.

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ThP1-1 | Control of spins in a quantum dot by spontaneousemission (#527)Jing Wang1,2, Ren-Bao Liu2, Bang-Fen Zhu 1,3, L. J. Sham4

1Tsinghua University Deartment of Physics, Beijing 100084, China2The Chinese University of Hong Kong Deartment of Physics, Shatin, N.T. HongKong (China)3Tsinghua University Institute of Advanced Study, Beijing 100084, China4University of California San Diego Department of Physics, La Jolla, California92093-0319, United States ContentIncoherent photon spontaneous emission during coherent optical control of spinsvia Raman processes is usually considered as a harmful factor to be avoided. However, since the dissipation via emission is essentially due to correlation ofthe fluctuations, when emission ends in a superposition of multiple final states,correlation between different pathways may build up if the “which-way”information is not fully resolved (i.e., the emission spectrum is broader than thetransition energy range). Such correlation can be exploited for spin-flip control ofa Λ-type three-level system in a quntum dot. Here we propose a scheme of spinecho with spin pump (initialization), spin flip (control), and probe (readout) allrealized by perturbative optical processes and show that the incoherentspontaneous emission can be utilized to control the spins. With the assistance ofincoherent spontaneous emission, the spin echo presents in the 5th-orderdifferential transmission signal. Otherwise, at least 7th-order optical nonlinearityis required. We use a spectral diffusion model in numerical simulation todemonstrate the suppression of pure spin decoherence under the flip of spin byspontaneous emission. This finding may open a new class of nonlinearspectroscopy with some perturbation orders of the optical field replaced by thevacuum fluctuation. References[1] Jing Wang, Ren-Bao Liu, Bang-Fen Zhu, L. J. Sham and D. G. Steel, Physical Review A, 83, 0538332011

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ThP1-2 | Photoreflectance lineshapes due to exciton continuumedge in quantum wells (#528)Amlan Mukherjee, Sandip Ghosh Tata Institute of Fundamental Research Condensed Matter Physics and MaterialScience, Homi Bhabha Road, Mumbai 400005, India ContentModulated reflectance spectroscopy techniques, such as photo-reflectance (PR)spectroscopy, are important for characterization of semiconductor opto-electronicdevice structures. At the heart of a typical modern opto-electronic device activeregion lies a quantum well (QW) structure. PR spectroscopy is often used as apost growth non-destructive method for characterization of the QW through ameasurement of its transition energy spectrum. However a typical devicestructure may have several semiconductor alloy layers and more than one QW,leading to a large number of spectral features. In addition the presence of built-inelectric fields will give rise to an asymmetry in the QW potential leading toadditional spectral features associated with normally-forbidden transitions. Toanalyze such complex spectra it is important to understand all the physicalphenomena that can give rise to spectral features and also what thecorresponding PR lineshapes would look like. Here we show that a subtle effect,whose origin lies in the behaviour of excitons in a 2D QW system as opposed toexcitons in 3D bulk, can give rise to additional spectral features in the PR spectraof a semiconductor QW. We have performed PR measurements onGaAs/AlGaAs quantum wells with high spectral resolution at low temperatures.We used a special dual detection plus electronic compensation scheme for PRmeasurement to improve the signal-to-noise ratio in order to be able to detectvery weak PR signals. We show that one can indeed observe a distinct PRspectral feature associated with the continuum edge discontinuity in the densityof states for 2D excitons. We verify this by comparison with photoluminescenceexcitation measurements and first principles simulation of the PR spectrum. Theiridentification immediately tells us the exciton binding energy. We also analyzethese lineshapes by using a modified version of Aspnes's derivative functionalform lineshape function. We show that these features have a distinct quantifiablelineshape symmetry that is different from the main heavy-hole and light-holeexciton transitions in the QW and which can therefore be used to identify suchfeatures.

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ThP1-3 | Ultra-Low-Power Modulation of an Optically-PumpedMicrodisk Laser with a Nanoelectromechanical Metal Cantilever(#556)Chieh-Feng Chang , Se-Heon Kim, Aditya Rajagopal, Axel SchererCalifornia Institute of Technology Electrical Engineering, 1200 E. CaliforniaBoulevard, Pasadena, CA 91125, United States ContentThe demand for miniaturized devices with a wireless interface has increasedrapidly in order for them to be deployed in large numbers at an affordable cost. Limited by the chip size, the power budget for the system is very tight, whichnecessitates the development of an efficient method of wireless communication. Specifically, optically-wireless systems are being intensively studied since theycan further shrink the device beyond the size of a battery or a radio frequencyantenna [1]. To turn on an electrically-pumped semiconductor laser, however, ittypically requires ~1.7 V and ~0.3 mA, which consumes ~0.5 W already. Thevoltage requirement of 1.7 V also introduces additional system complexity, sinceit is larger than the maximal voltage output from a single photovoltaic device ofcommon materials like silicon [2]. Multiple cells have to be connected in seriesas a result. Here we propose a new method to modulate a microlaser throughcapacitive mechanical tuning at ultralow power levels. Since the system ispowered by an external light source already, we resort to an optically-pumpedmicrolaser to avoid the power loss in the optical-electrical-optical conversion. Referring to Fig. 1, when no voltage is applied to the cantilever and the bottomelectrode, the microdisk laser is already pumped and ready to lase. When themodulation signal is sent to the electrodes, the capacitive force draws thecantilever close to the surface of the microdisk laser, which significantly lowersthe Q factor of the cavity and modulates the output intensity accordingly. Following the models in [3, 4], the thickness of and the gap below the cantileverneed to be in the nano regime for the operation voltage to be smaller than thevalue that can be reasonably provided from a single photovoltaic cell. Forexample, for a cantilever made of tungsten with dimensions of 5 µm by 2 µm by100 nm, a microdisk diameter of 10 µm and a gap of 100 nm, the actuationvoltage would be ~0.45 V. At its resonance frequency of ~1.5 MHz, thetheoretical power consumption of the modulation would be ~4 nW. Even ifimperfections are present in an actual device, the final power consumption wouldstill be greatly smaller than the original value of ~0.5 W. More results andanalysis will be presented in the conference. References[1] A. Scherer et al., “Systems and methods for optically powering transducers and related transducers,” U.S. patentPub. No. US2011/0044694 A1. [2] M. A. Green, “Limits on the open-circuit voltage and efficiency of silicon solar cellsimposed by intrinsic Auger processes,” IEEE T. Electron Dev. 31 (5), pp. 671-678 (1984). [3] G. G. Stoney, “TheTension of Metallic Films Deposited by Electrolysis,” Proc. R. Soc. London Ser. A 82, pp. 172-175 (1909). [4] G. M.Rebeiz et. al., “RF MEMS Switches and Switch Circuits,” IEEE Microw. Mag. 2 (4), pp. 59-71 (2001).

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Fig. 1:Schematics of the device. When a voltage is applied across the metal cantilever and the bottom electrode,the Q factor of the microdisk laser drops, which modulates the output intensity of the emission.

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ThP1-4 | Photoconductivity and photoluminescence under biasmeasurements in GaInNAs/GaAs multiple quantum wellsstructures (#1)Hagir Mohammed Khalil1, Benjamin Royall1, Simone Mazzucato1, Naci Balkan 1,Janne Puustinen2, Mircea Guina2, Ville-Markus Korpijärvi21University of Essex School of Computer Science and Electronic Engineering,Colchester, CO43SQ, Great Britain2Tampere University of Technology Optoelectronics Research Centre,,Korkeakoulunkatu 10, FI-33720, Tampere, Finland ContentThe low temperature photoluminescence under reverse bias (PLb) andphotoconductivity (PC) in GaAs p-i-n structure containing GaInNAs MQWs in theintrinsic region have been investigated. Both photocurrent and PLb signal show anumber of oscillations when plotted versus the applied reverse biased (Fig 1).We interpret the phenomena in terms of thermionic emission and negativecharge accumulation in the quantum wells and the formation of space chargedomains. At high temperatures thermal escape from the wells inhibit the chargeaccumulation and the oscillations diminish.

I-V:Fig 1. I-V results for GaInNAs/GaAs sample

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ThP1-5 | Electric generation of vortices in polariton superfluids(#25)Mikhail Kaliteevski 1,2, Ivan Shelykh3, Hugo Flayac4, Goran Pavlovic5

1Ioffe Institute, Polytechnichestaya, 194021 St-Petersburg, Russia2Academic University—Nanotechnology Research and Education Centre,Khlopina 8/3, 194021 St-Petersburg, Russia3University of Iceland, Dunhagi-3, IS-107 Reykjavik, Iceland 4Blaise Pascal University CNRS, avenue des Landais, FR-63177 Aubi`ere,France 5International Institute of Physics, av Odilon Gomes de Lima, Capim MacioNatal,, CEP 59078-400, Brazil ContentElementary excitations in superfluid Bose-Einstein condensates1 (BECs) arequantum vortices, topological defects arising from the Onsager-Feynmanquantization rule for the flow. Experimental investigations of the formation ofvortices remain one of the topical issues in physics of cold atoms andcondensate of exciton polaritons. Recently, optically exited vortices in polaritonsuperfluid were demonstrated [1,2]. However, hybrid states of exciton polaritonand Tamm plasmons [4] can be manipulated also by application of externalelectric field [4]. We have theoretically demonstrated the on-demand electricgeneration of vortices in an exciton-polariton superfluid [5]. Electric pulsesapplied to a horseshoe-shaped metallic mesa, deposited on top of themicrocavity, generate a noncylindrically symmetric solitonic wave in the system.Breakdown of its wave front at focal points leads to the formation of vortex-antivortex pairs (VAP), which subsequently propagate in the superfluid, as shownin figure 1. The trajectory of these vortex dipoles can be controlled by applying avoltage to additional electrodes. They can be confined within channels formed bymetallic stripes and unbound by a wedged mesa giving birth to grey solitons.Finally, single static vortices can be generated using a single metallic plateconfiguration, as shown in figure2. References[1] G. Nardin, G. Grosso, Y. Leger, B. Pietka, F. Morier-Genoud, and B. Deveaud-Pledran, Nat. Phys. 7, 635 (2011).[2] D. Sanvitto et al., Nature Photonics 5, 610 (2011) [3] M. Kaliteevski, I. Iorsh, S. Brand, R.A. Abram, I ShelykhAnd A.V Kavokin, Tamm plasmon-polaritons: Possible electromagnetic states at the interface of a metal and adielectric Bragg mirror, Phys.Rev. B 76, 165415 (2007) [4] M Kaliteevski, S Brand, R A Abram, I Iorsh, A V Kavokinand I A Shelykh, Hybrid states of Tamm plasmons and exciton polaritons, Appl. Phys. Lett., 95(25) 251108 (2009) [5]H. Flayac, G. Pavlovic, M.A. Kaliteevski, and I.A. Shelykh, Electric generation of vortices in polariton superfluids,Phys. Rev. B., 85, 075312 (2012) (2012)

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Figure 1:Figure 1. VAP nucleated by the application of a voltage impulse (a) Density of the condensate (b) Velocityfield of the condensate. (c) Phase vector field

Figure 2:Generation of single vortices. (a) Superfluid density 30 ps after the pulse, which exhibits shock wavesbroken into VAPs and single vortices. (b) the plate region at 80 ps; the VAPs have vanished and foursingle vortices remain stable.

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ThP1-6 | Top-Hat HELLISH (THH)-VCSOA based on a lightemitting and an absorbing for 1.3 µm wavelength operation (#37)Faten Chaqmaqchee 1, Naci Balkan1, J. M. Ulloa2, M. Hugues3, Mark Hopkinson3

1Essex university school of computer science and electronic engineering,wivenhoe park, colchester, CO43SQ, Great Britain2Universidad Politécnica de Madrid Institute for Systems based onOptoelectronics and Microtechnology, 28040 Madrid, Spain3University of Sheffield Electronic and Electrical Engineering Department,Sheffield, S1 3JD, Great Britain ContentTop-Hat (THH)- Vertical Cavity Semiconductor Optical Amplifier (VCSOA) is amodified version of Hot Electron Light Emission and Lasing in SemiconductorHeterostructure (HELLISH) VCSOA device. It has a shorter p-channel and longern-channel. The device consists of simple GaAs p-i-n junction, containing 11Ga0.35In0.65N0.02As0.08/GaAs MQW in its intrinsic region, the active region isenclosed between 6-pairs of AlAs/GaAs top DBR mirrors and 20.5-pairs of AlAs/GaAs bottom DBR mirrors. The operation of the device is based on longitudinalcurrent transport parallel to the layers of GaAs p-n junction. The device ischaracterised through I-V-L and by spectral photoluminescence,electroluminescence and electro-photoluminescence measurements. Anamplification of about 2.5 is observed at applied voltages of around V=40 Voltsand incident laser power of 13 mW.

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ThP1-7 | Gain studies of 1.3 µm dilute nitride Hellish-VCSOA foroptical communications (#38)Faten Chaqmaqchee 1, Naci Balkan1, M. Hugues2, Mark Hopkinson2

1Essex university school of computer science and electronic engineering,wivenhoe park, colchester, CO43SQ, Great Britain2University of Sheffield Electronic and Electrical Engineering Department,Sheffield, S1 3JD, Great Britain ContentThe Hot Electron Light Emitting and Lasing in Semiconductor HeterostructureVertical Cavity Semiconductor Optical Amplifiers HELLISH-VCSOA device isbased on Ga0.35In0.65N0.02As0.08/GaAs material for operation in the 1.3 µm windowof the optical communications. The device has undoped distributed Braggreflectors (DBRs). Therefore, problems such as those associated with refractiveindex contrast and current injection, which are common with the doped DBRs inconventional VCSOAs, are avoided. The gain versus applied electric field curvesare measured at different wavelengths using a tunable laser as the source signal.The highest gain is obtained for the 1.3 µm wavelength when an electric field inaccess of 2 kV/cm is applied along the layers of the device.

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ThP1-8 | Anomalous paramagnetic shift of annealednonmagnetic quantum dots (#46)Emanuela Margapoti1,2, Victor Lopez-Richard 3, Suddhasatta Mahapatra2, LukasWorschech2, Karl Brunner2, Qu Fanyao4, Carlos Destefani3, Eduardo Menéndez-Proupin5, Catherine Bougerol6, Gilmar E. Marques3

1Technische Universität München Walter Schottky Institut and PhysikDepartment, Am Coulombwall 4, DE-85748 Garching, Germany 2Universitat Wurzburg Physikalisches Institut, Am Hubland, 97074 Wurzburg,Germany 3Universidade Federal de Sao Carlos Departamento de Fisica, Sao Carlos, SP,13.565-905, Brazil 4Universidade de Brasilia Instituto de Fisica, Brasilia, DF, 608400-902, Brazil 5Universidad de Chile Departamento de Fisica, Las Palmeras 3425, 780-0024Santiago, Chile 6Institut Neel-CNRS Univ. J Fourier, 25 avenue des Martyrs, 38042 Grenoble,France ContentA characteristic signature of nonmagnetic semiconductors (NMSs) is theabsence of a permanent magnetic moment. Typically, the zero-dimensionalground state of the electron and the hole in NMS quantum dots (QDs) have zeroangular momentum and exhibit therefore, a diamagnetic response of spin splitstates to an external magnetic field. The realization of magnetic QDs, usuallyrequires the incorporation paramagnetic ions, e.g. Mn2+. Here we demonstratethat pronounced paramagnetic behaviour can also be observed in the spectra ofsingle nonmagnetic CdSe QDs after post-growth rapid thermal annealing [1] andwithout the incorporation of extra manganese spins. The photoluminescence ofannealed CdxZn1−xSe QDs under the influence of an external magnetic field wasstudied. The QDs were grown by molecular beam epitaxy [2]. Post-growththermal annealing was performed for different annealing times. Above a criticalannealing time, the QD luminescence shows a pronounced red-shift of theZeeman split magnetic subcomponents. This observation is in contrast to theblue-shift caused by the diamagnetic behavior usually observed in nonmagneticQDs. Such a behaviour cannot be observed in bulk materials and is associatedwith quantum-confinement induced inversion of heavy (hh) and light holes (lh)states that hybridizes the valence band ground state as depicted in Fig. 2. Theiso-probability surface of such a hybrid state is shown in the bottom part of Fig. 2(a). The different pure valence-band states contributing to the hybrid hole groundstate are shown in Fig. 2(b). While for a pure hh-state the angular momentumcomponent, m = 0, the hybrid state, due to contributions from the higher-lyingstates, acquires a non-zero magnetic quantum number. It is this non-zero valueof m along with the mean spin momentum j, which is responsible for the observedparamagnetic dispersion of the exciton transition in RTA-treated single QDs.Considering hybridization of the ground hole-state, the calculated trends of E, fordifferent values of the QD height are shown in the main panel of Fig. 2 (a). Therole of extra charges under the influence of the magnetic field [3] and the

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formation of charge excitons has also been simulated and discussed. Wepredict that this magnetic phenomenon might be observed in QDs based onother material systems as well. Therefore, annealed semiconductor QDs havethe potential to serve as a new class of magnetic material. References[1] Margapoti, E.; Alves, Fabrizio; Mahapatra, S.; Schmidt, T.; Lopez-Richard, V.; Destefani, C.; Menéndez-Proupin,E.; Qu, Fanyao; Bougerol, C.; Brunner, K.; Forchel, A.; Marques, G.; Worschech, L Phys. Rev. B 82 205318 (2010). [2] Mahapatra S, Kiessling T, Margapoti E, Astakhov G V, Ossau W, Worschech L, Forchel A and Brunner K. Appl.Phys. Lett. 89 43102 (2006). [3] Margapoti, E.; Worschech, L.; Mahapatra, S.; Brunner, K.; Forchel, A.; Alves, F M;Lopez-Richard, Victor; Marques, G; Bougerol, C. Physical Review B 77, 073308 (2008).

Figure 1:Magnetic response of single QD excitons confined in annealed QDs [1]. (a)-(c) circularly polarized PLcomponents of a single QD after thermal annealing. (d) Magnetic shift for the single QD emissions before(BTA) and after thermal anneling (ATA).

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Figure 2:2 (a) Calculated magnetic shift for different combinations of QD parameters. (b) The hybrid hole state iscomposed of states with different angular momentum, l, and component, m.

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ThP1-9 | Exploiting spin phenomena of exciton and trions in 2Dsystems (#72)Leonardo K. Castelano 1, Daniel Cesar1, Victor Lopez-Richard1, Gilmar E.Marques1, Odilon Couto Jr.2, Fernando Iikawa2, Rudolf Hey3, Paulo Santos3

1Universidade Federal de Sao Carlos Departamento de Fisica, Rod. WashingtonLuis, km 235 - SP-310, Sao Carlos, Sao Paulo, 13565-905, Brazil 2Universidade Estadual de Campinas Instituto de Fisica, Campinas, Sao Paulo,13083-859, Brazil 3Paul-Drude-Institut fur Festkorperelektronik, Berlin, Germany ContentThe Zeeman splitting modulation of neutral and charged excitons in twodimensional systems is investigated both theoretically and experimentally. Asystematic characterization of this effect was not previously available becausethe Zeeman splitting was considered unaffected in charged and neutral excitons.The nature of spin-dependent Coulomb interaction in 2D excitonic complexes insemiconductor GaAs quantum wells grown along the [110] direction istheoretically analyzed, as shown in Fig. 1 (a). The unusual growth direction [110]takes the advantage of large spin lifetimes when compared to analogoussystems grown along [100] direction. In Fig. 2 (a), we present thephotoluminescence confirmation of this effect that enables its generalization to2D systems with different compositions. Circularly polarized resolvedphotoluminescence has been used to study such effects under applied magneticfields. The renormalization of the effective Zeeman splitting by charging theexciton is expected and confirmed. According to the field strength, the groundstate spin polarization can be flipped and this condition differs for each kind ofexcitonic complex, as depicted in Fig. 2 (a). The nature of this behavior can beattributed to effects associated to the strong valence band admixture observed inalmost all semiconductor systems. Moreover, given the dependence of thevalence band state spin hybridization on the external bias, we predict that thiseffect can be easily tuned by an applied voltage. The degree of circularpolarization of both excitons and trions has revealed the peculiar spin dynamicstaking place in this kind of system, as shown in Fig. 2 (b). To explain suchresults, we proposed a theoretical model for the spin dynamics that takes intoaccount the fact that excitons and trions share the same source of carriers. InFig. 1(b), we present the theoretical results that show that neutral excitons aresubjected to a spin thermalization, affected by the Zeeman splitting tuning withmagnetic field, while the behavior of the trions is affected by the spin populationof the remaining carriers in the limit of slow spin-relaxation times.

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Figure 1:(a) Calculated Zeeman-splitting for optical recombination of X0, X+, and X- excitonic complexes in the[110] QW. (b) Theoretical calculations of the degree of circular polarization for the neutral exciton X0 andnegatively charged trions X-.

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Figure 2:(a) Zeeman splitting of X0 and X- complexes extracted from circularly polarized emissions. (b) Degree ofcircular polarization extracted from the PL spectra: open and filled circles correspond to the polarization ofX0 and X- complexes, respectively..

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ThP1-10 | Metafluid with anisotropic dynamic mass (#116)Jesus Arriaga1, Arkady Krokhin 2, Ludmila Gumen3

1Benemerita Universidad Autonoma de Puebla Instituto de Fisica, 18 Sur y SanClaudio, Edif. 110, Ciudad Universitaria, 72570 Puebla, Mexico2University of North Texas Department of Physics, Denton, Texas 76203, UnitedStates3Universidad Popular del Estado de Puebla Department of mathematics, 72160Puebla, Mexico ContentAnisotropy is a property which is usually associated with crystal solids. Fluidsand glasses are naturally isotropic in the absence of external fields. Anisotropymay, however, be artificially stimulated by embedding periodic structures innaturally isotropic fluids. Then these artificial structures — so called phononiccrystals — may have very unusual properties. Within a narrow band offrequencies of sound the effective mass or the effective elastic modulus ofspecially designed phononic crystals may become anisotropic, take negativevalues, or acquire abnormally large imaginary part. Due to such “strange”properties that do not exist for natural materials these artificial structures areusually called metamaterials or metafluids We show that a fluid filling the spacebetween solid cylinders arranged in a two-dimensional lattice exhibits anisotropicdynamic mass for sound waves propagating through the lattice, if its unit cell isanisotropic. Using the plane-waves expansion method proposed in Ref. [1] wederive (in the long wavelength limit) a formula for the effective mass tensor of themetafluid. The proposed formula is very general and it is valid for arbitraryBravais lattices and arbitrary filling fractions of the cylinders. In particular, wecalculate the effective mass tensor for sound waves in air with embedded latticeof aluminum cylinders having different cross sections. We consider cylinders withcircular and triangular cross sections arranged in both rectangular and hexagonallattice. The proposed method of calculation may find numerous applications fortailoring of metafluids with prescribed anisotropy which is necessary for design ofacoustic cloaks [2]. References[1] A.A. Krokhin, J. Arriaga, and L. Gumen, Phys. Rev. Lett. 91, 264302 (2003). [2] S.A. Cummer and D. Schurig, New J.

Phys. 9, 45 (2007).

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ThP1-11 | Polarized photoreflectance and photoluminescencespectroscopy of InGaAs/GaAs quantum rods grown withAs2 and As4 sources (#141)Ramūnas Nedzinskas 1, Bronislovas Čechavičius1, Julius Kavaliauskas1,Vytautas Karpus1, Gintaras Valušis1, Lianhe H. Li2, Suraj P. Khanna2, Edmund H.Linfield2

1Semiconductor Physics Institute, Center for Physical Sciences and TechnologyOptoelectronics department, A. Goštauto 11, 01108 Vilnius, Lithuania 2School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS29JT, Great Britain ContentSelf-assembled semiconductor quantum dots (QDs) formed by molecular beamepitaxy (MBE) are the foremost candidates for numerous applications inoptoelectronics. To modify polarization dependent optical gain function, importantfor optoelectonic engineering, columnar QDs or quantum rods (QRs) were grownby MBE, depositing a short period InAs/GaAs superlattice (SL) on top of a seedQD layer [1]. In this work we investigate optical polarization properties ofInGaAs QRs, MBE-grown with different As sources, As2 and As4. Two sets of QRstructures, grown on (001)-oriented GaAs substrate with SL periods N=10, 20,and 35, are studied using photoreflectance (PR) [2] and photoluminescence (PL)techniques. We also use polarized PR (PPR) and PL (PPL) to reveal both the in-plane optical anisotropy, and the cleaved facet polarization properties of QRs.Interband optical transitions within the InGaAs QRs and the surrounding quantumwell (QW) for As2/As4-grown quantum structures are revealed and discussed in-detail. Room temperature PR spectrum (Fig. 1) demonstrates a full-extent of theoptical transitions occuring within the nanostructure. An optical feature at 1.67 eVis due to the bandgap transition in the Al0.2Ga0.8As layer. Oscillations in thespectral range of 1.42–1.67 eV can be attributed to the above-GaAs-barrierstates. Optical features between 1.2–1.4 eV correspond to the optical transitionsin the InGaAs QW, which surrounds the QRs. Finally, the photon energy regionof 1–1.2 eV is associated with the ground and excited state transitions within theInGaAs QRs. The polarization properties of optical transitions observed in PPRand PPL spectra (Fig. 1) were evaluated by the in-plane polarization degree, P(001)

= (TE[1-10] – TE[110]) / (TE[1-10] + TE[110]), which reaches a high value of about 60%for QRs with N = 35. As a result, PL polarization properties (TE and TM modes)from the cleaved facet surfaces are different for the (110) and (1-10) facets. TheTM mode was dominant from the (1-10) surface (TM[001] > TE[110]), while from the(110) surface TE mode prevailed (TM[001] < TE[1-10]). In accordance with thetheoretical predictions [3], such intriguing optical anisotropy can be ascribed tothe hole wavefunction [1-10] orientation, which suppresses the TE[110] mode, andthe light-heavy-hole band mixing, which favors an increase of the TM[001] mode. References1. L. H. Li, G. Patriarche, M. Rossetti, and A. Fiore, J. Appl. Phys. 102, 033502 (2007). 2. B. Čechavičius, J.Kavaliauskas, G. Krivaitė, D. Seliuta, G. Valušis, M. P. Halsall, M. J. Steer, and P. Harrison, J. Appl. Phys. 98,023508 (2005). 3. M. Usman, T. Inoue, Y. Harda, G. Klimeck, and T. Kita, Phys. Rev. B 84, 115321 (2011).

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Nedzinskas-Fig_1.png:Fig. 1. Room temperature photoreflectance (PR) and photoluminescence (PL) spectra of the As4-grownsample L397 (N = 35). Polarized PR (PPR) and PL (PPL) spectra show a significant in-(001)-planepolarization anisotropy.

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ThP1-12 | Electromagnetic waves in a cylindrical superlatticewaveguide structure (#167)Mohammed Shabat Islamic University of Gaza Physics, Alazher str., Gaza 108, Egypt ContentMore work has been done in investigating the waves in multilayer's structureswhich composed of magnetic and non magnetic layers such as fef2 /znf2

superlattice. Shabat and Mousa[1-4] discussed the propagation characteristicsof nonlinear electromagnetic TE surface waves in a planer waveguide structureof a lateral antiferromagnetic/nonmagnetic superlattices (LANS) film bounded bya nonlinear dielectric cover. The non-reciprocal and bistability behaviors havebeen noticed. Mousa[4] studied the propagation characteristics of nonlinear TMsurface waves at (LANS) film bounded by a nonlinear cover. In recent years,much attention is drawn to artificial Left-handed materials or metamaterials withsimultaneously negative permittivity and permeability [5-7]. In thiscommunications, the propagation characteristics of both TE and TM waves in acylindrical waveguide structure of a lateral antiferromagnetic -non magneticsuperlattices (LANS) bounded by a left Handed material (LHM) are investigated.We have derived the eigenmodes equation and obtained the solutions for bothTE and TM propagation modes. For TE waves, we found that, adjusting thethickness of the waveguide to small reduced radius will support backward TEwave modes which can have very large effective index nx . At large reducedradius the forward waves of definite wave index and lower frequency areobserved. High power flow is switched by decreasing the operating frequency.The increasing of the magnetic field supports forward and backward waves ofhigher power and larger propagation lengths. Larger propagation lengths andconstant power of the backward waves are realized by decreasing the values of negative electric permittivity of LHM . Larger propagation lengths and lower power of the forward waves are realized by decreasing the values of negativemagnetic permeability of LHM. For TM propagation modes. We found that, thewaveguide supports backward TM waves since both permittivity and magneticpermeability of LHM are negative. The Largest wave index and largest propagation lengths of TM waves and best confinement are achieved for thethinnest LANS and less magnetic material.vWe also displayed the influence ofthe magnetic permeability and electric permittivity of LHM on the power flow ofTM waves. Larger wave indexes are switched by increasing permittivit andPermeability. We believe that new interesting results could lead to futurenanotechnology applications. References[1] H. M. Mousa, M. M.Shabat,H. Khalil and D.Jager, Proc.SPIE 5445, 274-278 ( 2003). [2] M. C. Oliveros, N. S.Almeida, D. R. Tilley, J. Thomas, and R. E.Camley, J.Phys; Condens. Matter, vol. 4, 8497- 8510, (1992). [3] H. M.Mousa, M. M.Shabat, Int.J. Modern Physics, B, 19 (29)4359-4369, ( 2005). [4] H. M. Mousa, M. M.Shabat, Int.J.Modern Physics, B, 21(6) 895-906, (2007). [5] V.Veselago, Sov. Phy. Usp. 10 509-514(1968). [6] R.Shelby, Science292, 77-79 (2001). [7] J. Pendry, Phys. Rev. Lett. 85, 3966-3969 (2000).

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ThP1-13 | Picosecond carrier dynamics induced by coupling ofwavefunctions in Si-nanodisk arrays fabricated using bio-templates (#270)Takayuki Kiba 1,2, Yoshiya Mizushima1, Makoto Igarashi3,2, Seiji Samukawa3,2,Akihiro Murayama1,2

1Hokkaido University Graduate School of Information Science and Technology,Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan 2Japan Science and Technology Agency CREST, 5 Sanbancho, Chiyoda, Tokyo102-0075, Japan 3Tohoku University Institute of Fluid Science, 2-1-1 Katahira, Aoba-ku, Sendai980-8577, Japan ContentSi nanostructures have extensively been studied because of their potentialapplications to photovoltaics and optoelectronics, which can be integrated withmodern Si technology. The size, density, and interspacing of the Sinanostructures need to be precisely controlled for the device applications. Forthis purpose, we have recently developed a fabrication process of closed-packedSi-nanodisk (Si-ND) arrays using bio-templates.[1] The carrier wavefunctions canspread over neighbouring NDs in this periodic regular alignment of the ND withultrathin potential barriers. Therefore, we expect the ultrafast carrier transferamong the NDs induced by coupling of the wavefunctions, which is important forfuture applications of superlattices composed of the present Si-NDs to highlyefficient solar cells and high-speed photonic devices. The Si-ND array wasfabricated by lithography using a bio-template composed of ferritinsupramolecules and neutral-beam etching. The ND thickness, diameter, and theinterspacing, were intentionally designed at 4, 10 and 2 nm, respectively. Thesamples were excited by second harmonic light pulses of a mode-lockedTi:sapphire laser with a wavelength of 400 nm. The time-resolved PL spectrawere detected by a streak camera. The time resolution of the transient PLobservation was 5 ps with deconvolution. Fig. 1 shows the PL time-profile of theSi-ND array at 250 K with an excitation power of 50 mW. The temporal evolutionof the PL profile was fitted by a triple exponential function. [2] From this fitting, wehave identified three PL decaying components with different time constants τ1 =850 ps, τ2 = 100 ps, and τ3 = 20 ps, respectively. Time-resolved PL spectra ofthe Si-ND array are shown in Fig. 2. The PL peak energy shifts towards lowerenergy side as the time elapsed. The time-resolved PL spectra reveal two energylevels, where the higher-energy level originates from coupling of carrierwavefunctions among NDs. The carriers at this level can transfer between NDswith a time constant of τ3. The lower-energy level corresponds to a localized stateof the carrier in each ND, emitting slower PL with τ1. The ultrafast carrier transferdemonstrates that high-density nanostructures precisely designed are highlyefficient for controlling the carrier dynamics and optical applications.

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References[1] C.-H. Huang, X.-Y. Wang, M. Igarashi, A. Murayama, Y. Okada, I. Yamashita, and S. Samukawa, Nanotechnology 22, 105301 (2011). [2] T. Kiba, Y. Mizushima, M. Igarashi, C.-H. Huang, S. Samukawa and A.Murayama, Appl. Phys. Lett. 100, 053117 (2012).

Fig. 1:PL time-profiles of the Si-ND array at 250 K. Solid black line shows a fitting result deconvoluted with aninstrumental response function and each resolved decaying component is shown by a narrow line.

Fig. 2:Time-resolved spectra of the Si-ND array at 250 K. Solid black lines shows the fitting result with aGaussian function.

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ThP1-14 | Fourier transformed modulation spectroscopy in themid and long wavelength spectral range (#285)Marcin Motyka, Filip Janiak , Grzegorz Sek, Krzysztof Ryczko, Jan MisiewiczWrocław University of Technology Institute of Physics, WybrzeżeWyspiańskiego, 50-370 Wrocław, Poland ContentModulation spectroscopy, due to its absorption and differential character, is anexcellent tool to study the energies of optical transitions (including the excitedstate ones) in quantum well (QW) and quantum dots as well as energies of bulk-like QW barriers or intermediate layers. Such experiments have already beensuccessfully employed to study GaSb-based QWs for infrared applications up to3 µm [1] and including type II structures for even longer wavelengths [2].Nevertheless, the standard modulation spectroscopy based on diffraction gratingmonochromators has some limitations due to several reasons like e.g. lesssensitive detectors or less efficiency of the probing light sources in case of midand far infrared (comparing e.g. to the tools used in the visible range) [3].Because there is a growing interest and necessity to investigate structuresdesigned for operation in mid and far infrared range (e.g. infrared detectors,quantum cascade lasers, etc.) it has been proposed to exploit modulationspectroscopy realized by using Fourier transformed spectrometer [3,4]. Thisapproach has already been used to investigate mainly the bulk-like materials andlayers. In this work we are demonstrating the application of FTIR modulationspectroscopy for investigation of low-dimensional structures like type I or IIquantum wells designed for mid infrared spectral region (up to ~ 5 µm)[5]. Inaddition, we would like to introduce the Fast Differential Reflectance (FDR)spectroscopy [6]. This technique allowed to posses the photoreflectance-likespectra similar to this achieved by modulation concept utilize lock-in amplificationtechnique. Nevertheless in FDR approach, the time of collecting spectra might byreduce from hour to seconds in comparison to standard grating- basedtechnique. In this study we have received reasonable FDR spectra of HgCdTelayers contains optical features in range of 5-15 µm connected with band gapabsorption in investigated structures(see Fig.1.)[7]. In this report we will alsopresent the results of FTPL and FTPR (or FDR) measurements applied foroptical investigations of the materials being results of infrared gas sensingrequirements (in the range of 2-10 µm). It can be mentioned e.g. GaInAsSb/InAslayers and quantum wells type II GaSb/AlSb/InAs/GaInSb/InAs/AlSb/GaSb(seeFig.2.)[8]. References[1] M. Motyka , G. Sęk, K. Ryczko , J. Misiewicz , S. Belahsene , G. Boissier, Y. Rouillard J. Appl. Phys. 106, 066104(2009) [2] M. Motyka, G. Sek, K. Ryczko, J. Misiewicz, T. Lehnhardt, S. Höfling, and A. Forchel, Appl. Phys. Lett. 94,251901 (2009) [3] T.J.C. Hosea, M. Merrick, B.N. Murdin, Phys. Stat. Sol.(A) 202, 1233 (2005) [4] Jun Shao, Wei Lu,Fangyu Yue, Xiang Lü, Wei Huang, Zhifeng Li, Shaoling Guo, Junhao Chu, Review of Scientific Instruments 78,013111 (2007) [5] M. Motyka, G. Sęk, J. Misiewicz, A. Bauer, M. Dallner, S. Höfling, and A. Forchel, Appl. Phys. Exp.2 (12) 126505 (2009) [6] M. Motyka, J. Misiewicz, Appl. Phys. Express 3 (2010) 112401 [7] M. Motyka G. Sęk, F.Janiak, J. Misiewicz, K. Kłos, J. Piotrowski, Measurement Science Technology 22 (2011) 125601 [8] M. Motyka, K.Ryczko, G. Sek, F. Janiak, J. Misiewicz, A. Bauer , S. Höfling, A. Forchel, Optical Materials 34 (2012) 1107–1111

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ThP1-15 | Intrinsic optical confinement for ultrathin InAs/GaAs/GaP quantum well superlattices (#311)Abdallah Sakri 1,2, Cédric Robert1,2, Laurent Pedesseau1,2, Charles Cornet1,2,Jacky Even1,2, Jean-Marc Jancu1,2

1Université Europeenne de Bretagne, INSA Rennes, 20, avenue des Buttes deCoësmes, 35708 Rennes, France 2CNRS, UMR 6082, Foton, 20 avenues des Buttes de Coësmes, 35708 Rennes,France ContentElectronic–Photonic Integrated Circuits on Si (EPIC) are probably the mostpromising challenge in information and communication technology. A lasercompatible with the current processing of electronic chips for integrated circuits,based on III-V materials, is extremely desirable to monolithically integrateelectronics and photonics1. To this end, new material systems are sought for inorder to enhance the range of possibilities. SiGe-based heterostructures2 andInAs/InP quantum wires3 are among recent avenues under study in the field ofband-gap engineering on Si. An additional possibility is that of the controlledintroduction of the localized states in ultrathin strained InAs quantum wells grownon Si substrates. So far this has received no attention mostly because of the lackof a viable means of introducing deep levels both controllable in energy andcompatible with the epitaxial growth of high-quality materials on Si substrate. Inthis work, we theoretically demonstrate the possibility of introducing energy-controlled localized levels in InAs-GaAs/GaP superlattices (SLs) compatible withthe experimental process. Electronic band structure calculations are performedwithin the extended basis sp3d5s* Tight-binding model4. This method provides theelectronic band structure over the whole Brillouin zone, the spatial and orbitalcompositions of the states, and the matrix elements of optical transitions. GaAs/GaP quantum wells on GaP are known to have an X-like conduction bandminimum5. We show that indium sheet in GaAs/GaP SLs induces a Γ-Xcrossover with a Γ-like conduction band minimum localised in the surrounding ofthe monolayer, resulting in enhanced dipole transition strengths. Theses resultsare supported by first-principle calculations. It is argued that the modelling herepresented provides a valid framework to implement a new class of type Iheterostructures for EPIC based on an engineered band structure. References1 D. Liang and J. E. Bowers, Nat. Photonics 4, 511 (2010) 2 J. Liu and al. Optics Letters, 35, 679 (2010) 3 M H HadjAlouane and al. Nanotechnology 22, 405702 (2011) 4J. M. Jancu and al. Phys. Rev. B 57, 6493 (1998) 5J. A. Prietoand al. Appl. Phys. Lett. 70, 3449 (1997)

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ThP1-16 | Photoluminescence polarization in strainedGaN/AlGaN core/shell nanowire heterostructures (#319)Pierre Lavenus 1, Gwénolé Jacopin1, Lorenzo Rigutti1, Sara Bellei1, François H.Julien1, Albert Davydov2, Denis Tsvetkov2, Kris Bertness3, Maria Tchernycheva1

1Institut d'Electronique Fondamentale, Université Paris Sud, 91405 Orsay,France 2MML, NIST, Gaithersburg, Maryland 20899, United States3PML, NIST, Boulder, Colorado 803005, United States ContentConventional c-plane AlGaN-based UV-LEDs suffer from the decrease of lightoutput efficiency with increasing Al composition due to high density ofdislocations, reduced extraction efficiency and the internal electric field. Inparticular, it has been shown that for AlxGa1-xN with x>0.12 the dominant opticaltransition is polarized parallel to the c-axis, which is detrimental for the emissionfrom the surface. In this context, core/shell GaN/AlGaN nanowire (NW) geometryis advantageous to improve microstructural quality, enhance light extractionefficiency and provide more flexibility in the design of the LED active region. Inthis work, we report on the optical properties of n-GaN/p-AlGaN core-shell NWheterostructures. The n-type GaN core NWs have been grown by plasma-assisted MBE, followed by epitaxial p-type AlGaN shell overgrowth using HVPEtechnique. The NW structure was studied by SEM/EDX and X-ray diffraction. Thecore-shell heterostructures consist of two parts: the NW base, about 10 µm long,containing bare GaN core with a diameter of 50-100 nm, and the top, around 7µm long, where the GaN core is covered by a 500-1000 nm thick AlxGa1-xN shellwith x=0.15-0.27. The micro-photoluminescence (µ-PL) maps of individual core-shell structures exhibit a set of emission peaks assigned to different NW regions(Fig 1a). When exciting the GaN NW uncoated base, a main peak at 3.472 eVcorresponds to the donor-bound exciton D°XA in strain-free GaN. The PLspectrum of core-shell part of the NW exhibits two additional features. One,around 3.51 eV, corresponds to strained GaN, while a second one, between3.7-3.8 eV, originates from the AlGaN shell. The polarization resolved µ-PLanalysis (Fig. 1b) shows that the near-band-edge (NBE) peak of the relaxed GaNis polarized perpendicular to the NW axis, according to the selection rules of theWurtzite crystal. However, NBE from the strained GaN core in the core-shellstructure is polarized parallel to the NW axis. The luminescence of the AlGaNshell is almost unpolarized because of the tensile c-axial strain in the shell. Thepolarization properties are interpreted by modeling the electronic band structureof GaN and AlGaN under uniaxial strain along the c-axis. By means of 6x6 k.panalysis, we demonstrate that it is possible to keep the AlGaN emission polarizedalong the c-axis, in order to enhance the light extraction along the NW axis byengineering both the strain and the composition in the AlGaN shell.

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Figure1:a) Position resolved photoluminescence (the NW SEM inset is shown at the top of a) b)Micro-PL spectraat different polarization at T=4K.

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ThP1-17 | Synthesis and enhanced blue emission of Eu2+-dopedGaN/SiO2 nanocomposites by addition of SiO2 nanoparticles(#355)Kang Bong Kyun , Kim Myung-Oh, Yoon Dae HoSungkyunkwan University School of Advanced Materials Science andEngineering, Suwon 440-746, Korea Republic (South) ContentIn recent years, III-nitrides nanostructures have attracted extensive attention dueto their unique electronic and optical properties. Gallium nitride (GaN) has adirect wide bandgap of 3.4 eV at room temperature, and is a promising candidatematerial for short wavelength optoelectronic devices, such as light emittingdiodes and laser diodes, as well as high power and high temperature operationdevices. Forthermore, rare earth-doped GaN have a promising applications asmultiple color electroluminescent (EL) devices due to the chemical stability and alarge incorporation of rare earth dopants such as Eu, Er, Tb, Tm. In case of Euions in host materials, it has a distinctive optical property which was commonlyobserved strong and shape emission at around 612 nm by the f-f transitions ofEu3+ ions, on the other hand, the Eu2+ ions showed broad blue emission ataround 450 nm, depending on the environments around the Eu ions such as inaluminates, silicate matrices. Despite the large number of reports on thesynthesis of rare earth doped GaN over the past few years, most reports focusedon the rare earth doped GaN film and nanowires by MOCVD, MBE, MOVPE andthermal CVD. Compared with film and nanowires, GaN nanopowder could bealternative hybrid integration materials with a variety of optical propertiesbecause of the flexible powder form and controlled shape or size, as well as lowfabrication cost [1-3]. GaN:Eu2+ added SiO2 nanoparticles were synthesizedsuccessfully nitridation of Eu3+-doped gallium oxide with SiO2 nanoparticles. Wereport on the synthesis and characterization of the GaN:Eu2+ added SiO2

nanoparticles as a function of SiO2 amounts. Strong emission and shoulderpeaks of the Eu2+-doped GaN/SiO2 nanocomposites were observed at around470 nm and 450 nm upon the addition of SiO2, respectively. The Eu2+-dopedGaN/SiO2 nanocomposites showed the highest blue emission intensity at 0.15mol% of SiO2 nanoparticles. References[1] Kang SM, Kang BK, Kim SW, Yoon DH. Cryst. Growth Des 2010; 10: 2581–2584. [2] Li YQ, Delsing ACA, de WithG, Hintzen HT. Chem. Mater 2005; 17: 3242-3248. [3] Xu CK, Chun JH, Chon BH, Joo TH, Kim DE. Nanotechnology2007; 18: 015703-015707.

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Photoluminescence spectra:Photoluminescence spectra of Eu2+- GaN/SiO2 nanocomposites with various amounts of SiO2 addedfrom 0.01 to 0.25 mol% at room temperature, λex = 317 nm.

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ThP1-18 | Mode structure of photonic wires in an organicmicrocavity in three dimensions (#405)Felix Lemke , Susanne Hintschich, Andreas Mischok, Christoph Reinhardt,Vadim Lyssenko, Alexander Zakhidov, Robert Brückner, Hartmut Fröb, Karl LeoTU Dresden Institut für Angewandte Photophysik, George-Bähr-Str. 1, 01326Germany, Germany ContentWe investigate a microcavity made of two distributed Bragg reflectors (DBRs)enclosing a lambda/2-layer of the organic dye Alq3 doped with 2 wt.% of the laserdye DCM. Between this active layer and the bottom DBR, we deposited a 40 nmthin metal grating of 7.4 or 11.1 µm period and 3.7µm stripe width.1 Thereby, wegenerate photonic wires, in which light is confined in one lateral direction.2,3 Viaµ-photoluminescence spectroscopy, we observe the resulting discretisation ofthe cavity resonance in the angle dispersion (or far field), see figure. This well-known behaviour is observed when collecting emission in the planeperpendicular to the metal stripes. By use of a dove prism, we rotate thisobservation plane about the sample normal axis, see sample sketch. Thedetected far field shows a transition from discrete states upon collectionperpendicular to the metal stripes to multiple continuous parabolae uponcollection parallel to the metal stripes, see left panels of the figure below. In orderto explain this behaviour, we perform an analytical calculation. The two-dimensional dispersion relation is exactly described using the geometry of thesample. We calculate the energy dispersion relation E(j, q) depending on thesample orientation j and the outcoupling angle q. Additionally, the two-dimensional Fourier transformation gives the intensity distribution along theenergy curve. By combining these two equations, the behaviour shown in theexperiments is perfectly reproduced, despite our approximations of an idealresonator with perfect reflectivity and a vanishing electric field at the metal edges.In short, we demonstrate a three-dimensional tomography of the resonances ofphotonic wires by using a Dove prism to rotate the plane of photoluminescencedetection. We model our experimental results using analytical calculations whichare based on a surprisingly simple coordinate transformation. Nevertheless, theresulting three-dimensional description of photonic wire resonances unifies theup-to-now incomplete experimental and theoretical descriptions in the literature.4,5,6

References1 R. Brückner, A.A. Zakhidov, R. Scholz, M. Sudzius, S.I. Hintschich, H. Fröb, V.G. Lyssenko, and K. Leo, NaturePhotonics in press , (2012) 2 F. Manni, K.G. Lagoudakis, B. Pietka, L. Fontanesi, M. Wouters, V. Savona, R. André,and B. Deveaud-Plédran, Phys. Rev. Lett. 106, 176401 (2011) 3 G. Dasbach, C. Diederichs, J. Tignon, C. Ciuti, Ph.Roussignol, C. Delalande, M. Bayer, and A. Forchel, Phys. Rev. B 71, 161308(R) (2005) 4 A. Kuther, M. Bayer, T.Gutbrod, A. Forchel, P.A. Knipp, T. L. Reinecke, and R. Werner, Phys. Rev. B 58, 15744 (1998) 5 A.I. Tartakovskii,V.D. Kulakovskii, P.S. Dorozhkin, A. Forche, and J.P. Reithmaier, Phys. Rev. B 59, 10 251 (1999) 6 M.Abbarchi, V.Ardizzone, T. Lecomte, A. Lemaître, I. Sagnes, P. Senellart, J. Bloch, P. Roussignol, and J. Tignon, Phys. Rev. B 83,201310(R) (2011)

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Figure 1:Sketch of the DBR microcavity with photonic wires and the geometry for collecting samplephotoluminescence. A Dove prism is used to rotate the image plane and the far-field distribution at thespectrometer entrance.

Figure 2:Far field measurements (left panels) and analytical calculations (right panels) for a rotation of theobservation plane by 0° to 90°.

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ThP1-19 | Laser-induced thermal diffusion of Mn-interstitialsand Stark spectroscopy in nano-LEDs (#413)Ateeq Nasir 1, Oleg Makarovsky1, Santosh Kumar2, Mike W. Fay3, RichardCampion1, Laurence Eaves1, Armando Rastelli2, Oliver G. Schmidt2, AmaliaPatanè1

1The University of Nottingham Physics and Astronomy, Nottingham, NG7 2RD,Great Britain2IFW-Dresden Institute for Integrative Nanosciences, Helmholtzstraße, 01069Dresden, Germany 3The University of Nottingham Nottingham NanoScience and NanoTechnologyCentre (NNNC), Nottingham, NG7 2RD, Great Britain ContentWe describe how laser-induced annealing can be used to thermally diffusemobile charged ions into the active region of a GaAs based light-emitting diode(LED). The dopant ions form preferential submicron-sized channels for electricalinjection of carriers into the quantum well (QW) of the device. Our techniqueprovides a new means of creating a wavelength resolution-limited LED spot atone or more predetermined positions on the crystal surface or else an orderedarray of such nano-LEDs. We also use stark spectroscopy as a nanoscale probeto measure the ion-induced electric field fluctuations in the device. Our device isan MBE-grown p-i-n heterostructure diode with an AlAs/GaAs/AlAs QW in theoptically active intrinsic (i) region. The top p-contact is a layer of (GaMn)As with[Mn] = 12%. By focusing a laser beam on the top surface, we activate thediffusion of Mn interstitial ions from the (GaMn)As layer towards the QW (Fig. a).The random clustering of these ions creates a complex potential landscape U inthe (x, y) plane of the QW which we can probe with nanoscale precision bymonitoring the quantum-confined Stark shift of the luminescence peaks of the“natural” quantum dots formed by monolayer fluctuations in the QW (Fig. b). Thenanoscale laser assisted diffusion of Mn interstitial ions can not only enhanceexisting luminescence peaks but also tune their emission energy by modifyingthe quantum-confined Stark shift (Fig. c). The spatially varying electric fieldassociated with this potential acts to reduce significantly the built-in electric fieldof the p-i-n junction in nanoscale regions of the (x, y) plane (Fig. d & e) and, inforward bias, leads to enhanced spot-like LED emission from the laser-annealedregions [2-3]. The use of focused laser annealing to form nanoscale opticaldevices and controlled electric field landscapes at predetermined positions in adevice has potential for general use in other material systems that can hostmobile dopant atoms. It can be implemented to locate and tune quantum statesof, for example, self-assembled QDs for applications in quantum information andnanophotonics. References[1] A. P. Wijnheijmer, O. Makarovsky, J.K. Garleff, L. Eaves, R.P. Campion, B.L. Gallagher, and P.M. Koenraad,Nano Lett. 10, 4873 (2010). [2] O. Makarovsky, S. Kumar, A. Rastelli, A. Patanè, L. Eaves, A.G. Balanov, O.G.Schmidt, R. Campion, and C. T. Foxon, Adv. Materials 22, 3176 (2010). [3] F. Intonti, V. Matarazzo, A. Nasir, O.Makarovsky, R. Campion, A. Patanè, S. Kumar, A. Rastelli, O. G. Schmidt, and M. Gurioli, App. Phys. Letts. 98,183102 (2011)

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Figure 1:a) Schematic of the LED and laser-induced diffusion of ions. b) The bias dependence of microPL linesshow shifting maxima of the emission energy. c) microPL spectra showing the strong enhancement andthe appearance of new features after anealling.

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Figure 2:Numerical simulation of the varying in-plane electric field d) and perpendicular electric field e) created inthe central plane of the QW by Mn interstitial ions.

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ThP1-20 | Thickness dependence of photoluminescence ofheavily-doped GeOI (#424)Dandan Zhao1, Choong Hyun Lee2,3, Tomonori Nishimura2,3, Kosuke Nagashio2,3,Guo-An Cheng 1, Akira Toriumi2,3

1Beijing Normal University College of Nuclear Science and Technology, beijing100875, China2The University of Tokyo Department of Materials Engineering, 7-3-1 HongoBunkyo-ku,, Tokyo 113-8656, Japan 3JST-CREST, 7-3-1 Hongo Bunkyo-ku,, Tokyo 113-8656, Japan ContentJunctionless Ge p-channel field-effect transistors (FET) fabricated on heavily-doped GeOI has been proposed as a promising candidate for future electrondevice applications due to its higher mobility than Si one.[1] The off-state ofjunctionless Ge FET is achieved by fully-depleted the channel, thus an ultrathinGe film is needed. However, when the Ge thickness become very thin, electricalor optoelectronic properties may be changed due to quantum effect. In this work,thickness dependece of photoluminescence of heavily-doped GeOI isinvestigated. P-type gallium-doped GeOI substrate with a doping concentration of1019 cm-3 was used in this study. The initial thickness of Ge was 100 nm, and Gewas thinned by a H2O2-based wet etching process. The final thicknesses of Gewere about 8, 12, 22, 55, 100 nm, respectively, which were determined byspectroscopic ellipsometry. The pumping laser of photoluminescence has thewavelength of 457 nm and the power of 3 mW. The InGaAs detector has thedetection range from 1400 to 2000 nm to cover almost all range of spectrum forGe. Fig. 1 shows a photoluminescence spectrum of GeOI with various Gethicknesses, which indicates that band gap becomes wider when Ge thickness isreduced to less than 10 nm. The reason is under investigation. References[1] D. D. Zhao, T. Nishimura, C. H. Lee, K. Nagashio, K. Kita, and A. Toriumi: Appl. Phys. Express 4 (2011) 031302.

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Fig. 1:Photoluminescence spectrum of GeOI with various Ge thicknesses

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ThP1-21 | DIMENSIONALITY AND ASPECT RATIO EFFECTS ONTHE NONLINEAR OPTICAL RESPONSE OF EXCITON STATESIN SEMICONDUCTOR NANOSTRUCTURES (#450)Hanz Ramirez , Jeff Florez, Angela CamachoUniversidad de Los Andes Physics Department, Crra. 1 No. 18A-12, Bogotá,Colombia ContentNonlinear optical response of some materials is a useful feature for applicationsencompassing a wide range of fields including optoelectronics, spectroscopy,sensing, and communications, between others. In particular, second harmonicgeneration has been found suitable for production of high quality polarizationentangled photon pairs [1]. However, the conversion efficiency of the currentlyavailable nonlinear crystals is still far from being optimal. On the other hand,recent progress in fabrication of nanostructures has allowed engineering wavefunctions of carriers in such a way that variables as dipole moments andtransition energies, which crucially determinate nonlinear properties, can becontrolled in an unprecedented manner [2]. Previous reports on nonlinear opticalresponse in semiconductor quantum wells point out the enhancement in severalorders of magnitude of the second order susceptibility as compared to bulksystems. Nevertheless, corresponding studies in lower dimensions are scarce inthe literature. In this work we study the second order harmonic generationby exciton transitions in ensembles of quasi-1D and 0D semiconductornanostructures, by evaluating the effects of dimensionality and shape on thesecond order optical susceptibility. For the studied nanostructures we observe astrong dependence of the nonlinear susceptibility on the aspect ratio of theconfining potentials, even at the point of increasing several orders of magnitudewhen varying the nanostructure from rod-like dots (1D) to disk-like dots (0D).This suggests a convenient scheme for controlling nonlinearities innanostructured materials, and to a greater extent, a more efficient parametricconverter for entanglement generation. References[1] N. Grosse et al., Phys. Rev. Let. 96, 063601 (2006) [2] E. Rosencher et al., Science 271, 168 (1996)

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ThP1-22 | Time-resolved photoluminescence studies ofGa(AsBi)/GaAs single quantum wells (#452)Mohammad Khaled Shakfa 1, Dimitri Kalincev1, Alexej Chernikov1, SangamChatterjee1, Martin Koch1, Xianfeng Lu2, Shane R. Johnson2, Dan A. Beaton3,Thomas Tiedje4

1Philipps-University of Marburg Department of Physics, Renthof 5, 35032Marburg, Germany 2Arizona State University Department of Electrical Engineering, Tempe, Arizona85287-6206, United States3University of British Columbia Department of Physics and Astronomy,Vancouver, British Columbia V6T 1Z4, Canada 4University of Victoria Department of Electrical and Computer Engineering,Victoria, British Columbia V8W 3P6, Canada ContentNovel semiconductor alloys containing Bi have received considerable attentionover the last decade due to their potential application in photonic and spintronicdevices, especially in near and mid-infrared spectral range [1-4]. Bi incorporationinto GaAs resulting in a great reduction in the band gap as much as 60-80 meVper percent of Bi resulting from the giant band gap bowing effect [1,2], whichhave been described using the valence-band anticrossing model [3]. Additionally,a high bowing coefficient of the split-off band is reported [5]. In our recent work,time-resolved photoluminescence (TRPL) technique is used to investigate carrierdynamics of Ga(AsBi)/GaAs single quantum well (SQW) with Bi concentration of5.5%. The excitation source was a mode-locked Ti:sapphire laser trend to 780nm with 80 MHz repetition rate and pulse duration of 100 fs. The emission signalwas spectrally dispersed by imaging spectrometer, and temporally resolved usinga streak camera. Efficient PL emission is reported in infrared spectrum even atroom temperature (RT) with a peak wavelength of 1150 nm. At low temperatures,PL emission is dominated by the recombination of localized electron-hole pairsdue to the varying concentration and clustering of Bi in Ga(AsBi) alloy's structure[2]. Furthermore, the PL spectra exhibit a blue-shift and broadening withincreased excitation intensity due to the filling of the localized states. For evenhigher excitation conditions, additional PL signatures at the high energy side ofthe emission peak [1], indicating higher confined states of the quantum well. Anon-monotonous temperature dependence of the PL maximum position, the so-called S-shape accompanied by the characteristic maximum of the linewidth areobserved as a result of the hopping transitions of charge carriers betweenlocalized states. In addition, the PL exhibits a typical thermal quenching as wellas a significant shortening of the decay time due to the delocalization of carriersand increased non-radiative recombination. A substantial increase in the decaytime with decreasing energy across the main PL peak of the investigatedstructure is observed under low excitation intensities and low temperatures, seeFig. 1. Gourdon and Lavallard model is used to fit the experimental results [6].Characteristic localization energy of 9.5 meV is found according to this model,attributed to the energy distribution of the Bi-clusters [2].

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References[1] Y. I. Mazur, V. G. Dorogan, M. Schmidbauer, G. G. Tarasov, S. R. Johnson, X. Lu, S.-Q. Yu, Zh. M. Wang, T.Tiedje, and G. J. Salamo, Nanotechnology 22, 375703 (2011). [2] S. Imhof, A. Thranhardt, A. Chernikov, M. Koch, N.S. Koster, K. Kolata, S. Chatterjee, S. W. Koch, X. Lu, S. R. Johnson et al., Appl. Phys. Lett. 96, 131115 (2010). [3]S. Imhof, C. Bückers, A. Thränhardt, J. Hader, J. V. Moloney, and S. W. Koch, Semicond. Sci. Technol. 23, 125009(2008). [4] K. Oe, Jpn. J. Appl. Phys. 41, 2801 (2002). [5] B. Fluegel, S. Francoeur, A. Mascarenhas, S. Tixier, E. C.Young, and T. Tiedje, Phys. Rev. Lett. 97, 067205 (2006). [6] C. Gourdon and P. Lavallard, Phys. Status Solidi B153, 641 (1989).

Figure 1:PL spectrum and its PL decay time as a function of emission photon energy. Dashed line represents thetheoretical fit. Inset shows related PL transition profiles for various emission photon energies. Thetransitions were normalized and shifted vertically.

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ThP1-23 | Multi-exciton emission of ordered SiGe islandensembles (#471)Petr Klenovský1, Florian Hackl 2, Elisabeth Lausecker2, Moritz Brehm2, VlastimilKřápek1, Hubert Steiner2, Thomas Fromherz2, Josef Humlíček1, FriedrichSchäffler2, Günther Bauer2

1Masaryk University Department of Condensed Matter Physics, Kotlářská 2,61137 Brno, Czech Republic 2Johannes Kepler University Institute of Semiconductor and Solid State Physics,Altenbergerstrasse 69, A-4040 Linz, Austria ContentThe growth of SiGe islands on pit-patterned substrates results in islandensembles with superior structural and compositional homogeneity as comparedto randomly nucleated islands on planar substrates grown under identicalconditions [1]. It has been shown that this homogeneity can be achieved overlarge areas (in the 10 mm2 range) of addressable islands [2]. We utilize theselarge area, homogeneous island ensemble for investigating the dependence ofthe photoluminescence emission of the SiGe islands on the excitation intensity inthe range between 0.15-8 W/cm2 emitted by an Ar+ laser operating at 457.9 nm.The islands were grown by solid source molecular beam epitaxy on substrateswith 170 nm and 300 nm periods. On the substrate with smaller period,homogeneous island ensembles were grown at lower temperatures as comparedto the substrates with larger period. As a consequence, the Ge concentration islarger in those islands and their emission spectrum is shifted by ~50,meVtowards lower energies as compared to the islands on the substrate with 300 nmperiod. For both types of islands, the ensemble PL emission line-widths arereduced by a factor of ~3 as compared to islands nucleated on unpatternedsubstrates, indicating the superior compositional homogeneity of the orderedSiGe islands. The rather narrow PL emission lines permit a detaileddecomposition of the ensemble PL spectrum into various exciton recombinationchannels. A detailed analysis of the dependence of these channels' intensity onthe excitation intensity allows us to identify multi-exciton contributions to the PLemission via their non-linear characteristics. The observed energy differencesbetween single and multi-exciton emissions are in excellent agreement withmodel calculations based on the configuration interaction method [3] using singleelectron (hole) wavefunctions as calculated by the nextnano simulation package[4] as basis states. Depending on the Ge concentration, an anti-binding exciton-exciton interaction energy for the type-II SiGe islands of 10 meV and 16 meV isobtained. References[1] M. Brehm, M. Grydlik, F. Hackl, E. Lausecker, T. Fromherz, G. Bauer, Nanoscale Research Letter 5, 1868 (2010).[2] E. Lausecker, M. Brehm, M. Grydlik, F. Hackl, I. Bergmair, M. Mühlberger, T. Fromherz, F. Schäffler, G. Bauer,Appl. Phys. Lett. 98, 143101 (2011). [3] S. Rodt, A. Schliwa, K. Pötschke, F. Guffarth, D. Bimberg, Phys. Rev. B 71,155325 (2005). [4] J. A. Majewski, S. Birner, A. Trellakis, M. Sabathil, P. Vogl, phys. stat. sol. (c) 1, 2003 (2004).

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SiGe island PL spectrum:Measured (red) and fitted PL spectra (symbols and broken lines). The identification of the multi-excitonline XX0 is based on its quadratic increase with the excitation intensity and model calculations.

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ThP1-24 | Optically in-well pumped VECSEL emitting beyond 3µm (#514)Amir Khiar1, Michael Witzan1, Martin Eibelhuber1, Astrid Hochreiner1, ThomasSchwarzl1, Hans Zogg2, Gunther Springholz 1

1University of Linz Institut for Solid State and Semiconductor Physics,Altenbergerstr. 69, 4040 Linz, Austria 2Thin Film Physics Group ETH Zuerich, CH-8005 Zuerich, Switzerland ContentIn this work, the first optically in-well pumped vertical external cavity surfaceemitting laser (VECSELs) operating in the wavelength range beyond 3 µm ispresented. Mid-IR laser are especially suitable for spectroscopic sensingapplications, since the strong fundamental vibration mode of molecules are lyingwithin the mid-IR. Among others, they are used for environmental monitoring,high speed exhaust gas analysis, chemical reaction control and so on [1]. Incontrast to all edge emitting diode lasers, VECSELs are attractive forspectroscopic sensing due to their very small beam divergence (<1°) and nearlyperfect circular emission cone[4-6]. In addition, VECSELS offers power scalabilityas a result of their nearly vertical heat flow and are generally optically pumped.The active structure of our VECSEL is formed by 30 periods of PbTe QWs (each15 nm thick) and CdTe barriers (each 50 nm thick) (Fig. 1). All layers aredeposited by MBE on a GaAs substrate without any further processing. Thebarrier material is transparent for our 1.55 µm pump laser. Consequently, allpump power is only absorbed in the QWs (in-well pumping). The material systemPbTe/CdTe allows also to produce active regions containing PbTe dots in CdTe[4]. As shown in Fig. 1, the bottom Bragg mirror of the VECSEL is realized with4.5 PbEuTe/EuTe layer pairs to reach a reflectivity of more than 99.9%.Pb0.97Eu0.03Te is used as high refractive index material with n ~ 5, and EuTe aslow index material with n = 2.4. The resonant laser cavity is completed with acurved top mirror situated external to the layer structure and consisting of 2.5pairs of Pb0.94Eu0.06Te and BaF2 (n ~ 1.45). Such an arrangement contains a freespace region permitting optical pumping directly of the active region and verticallaser emission from the chip surface. Figure 2 shows measured spectra of theVECSEL at different temperatures. Pumping is done with 100 ns pulses and 10kHz repetition frequency. The VECSEL is tunable from 3.7 µm down to 3.2 µm byincreasing the temperature from 98 K to 203 K. The absorbed threshold pumppower is around 13.5 W and the maximal output power is around 5 mW. Byoptimizing the quantum well position with respect to the intensity distribution ofthe laser and pump beam we expect to increase the operation temperature up toRT. Furthermore, the PbTe QW active region will be replaced by a PbTe dotstructure, which finally could lead to very low threshold VECSELs.

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References[1] A. Krier “Mid-infrared Semiconductor Optoelectronics”, (Springer, Verlag London Limited, 2006). [2] A. Hochreiner,T. Schwarzl, M. Eibelhuber, W. Heiss, G. Springholz, V. Kolkovsky, G. Karczewski, T. Wojtowicz, Appl. Phys. Lett.,98, 021106/1-3 (2011). [3] T. Schwarzl, E. Kaufmann, G. Springholz, K. Koike, T. Hotei, M. Yano, W. Heiss, PhysicalReview B 78, 165320 (2008). [4] M. Kuznetsov, Semiconductor Disk Lasers: Physics and Technology, Wiley, NewYork, 2010, Chapter 1. [5] A. Khiar, M. Rahim, M. Fill, F. Felder and H. Zogg, Appl. Phys. Lett. 97, 151104 (2010). [6]M. Rahim, A. Khiar, M. Fill, F. Felder and H. Zogg, Appl. Phys. Lett. 94, 201112 (2009).

Khiar_FiguresL_ICSNN-2012:Figures

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ThP1-25 | Enhanced second harmonic generation from periodicpolarity-inverted GaN waveguide (#529)Ryuji Katayama 1,2, Yujiro Fukuhara3, Masahiro Kakuda3, Shigeyuki Kuboya3,Kentaro Onabe3, Tomonori Matsushita4, Takashi Kondo4, Hiroyuki Yaguchi5,Takashi Matsuoka1

1The Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Miyagi,Aoba-ku, Sendai 980-8577, Japan 2PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Saitama,Kawaguchi 332-0012, Japan 3Department of Advanced Materials Science, The University of Tokyo, 5-1-5Kashiwanoha, Chiba, Kashiwa 277-8561, Japan 4Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo,Tokyo, Bunkyo-ku 113-8656, Japan 5Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Saitama, Sakura-ku 338-8570, Japan Content As a novel application to the quantum optics, a periodic polarity-inverted GaNwaveguide with a period of 2.0 µm was fabricated (Fig.1) utilizing molecularbeam epitaxy and electron beam lithography [1,2]. Here we report on thesuccessful periodic reversal of the crystallographic orientations with ±c, andintense violet second harmonic generation (SHG) with the aid of aspontaneously-formed grating structure on the surface, which enables us tocouple the incident light to the guided modes resonantly. In this work, firstly linearoptical properties were assessed by variable-angle optical reflectance spectra toassign the origins of all these resonances, next the enhanced SHG wasdemonstrated using a tunable laser as a fundamental wave. Sample wasmounted on an optical goniometer with multiple scanning axes of incident angle θand detection angle ζ, both were synchronously scanned to monitor the specularreflections. A white light from a Xe lamp was focused onto the waveguide, andreflected beams were collected by an optical fiber which was connected to CCDspectrometer with a sensitivity range from 300 to 1600 nm. In the actualsequence of measurements, the angle ζ dependence of the reflectance spectra,scanned from 15.0° to 150.0° with a step of 1.0°, were recorded. In addition tothe optical interference fringes, clear reflectance dips originated from theresonance between the incident light and guided modes appeared. Taking intoaccount the refractive index dispersions and the zone-folding effects invoked bythe grating, origins of all the resonant features are successfully elucidated.Especially in case of resonant coupling to the guided modes, the correspondingorders of both the grating diffractions and the guided modes are assignedcorrectly. Then the incident light was replaced by a p-polarized beam from amode-locked Ti:sapphire laser (80-100 fs, 81 MHz). Violet emission wascollected by the identical optics used for the above measurements and dispersedthrough a grating spectrometer, and detected by a photomultiplier tube. In caseof fundamental wavelength around 850 nm, the successful resonant 103-times-enhancement of SHG has been confirmed (Fig.2), which satisfy three criteria: a

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spectral narrowing with a central wavelength of 425 nm which reflects a tuningcharacteristic of the quasi phase matching, the power of violet emission which isproportional to the square of fundamental power, and its complete polarizationdependence. References[1] R. Katayama, Y. Kuge, T. Kondo and K. Onabe, J. of Cryst. Growth 301-302, 447 (2007). [2] Y. Fukuhara, R.Katayama and K. Onabe, phys. stat. sol. (c) 7 (7–8), 1922 (2010).

Figure 1:Fabrication process flow of periodic polarity-inverted GaN waveguide.

Figure 2:Second harmonic intensity plotted against incident and exit angles in case of fundamental wavelength of850 nm.

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ThP1-26 | Detectivity Improvement of Quantum Well InfraredPhotodetectors using a Photonic Crystal Slab as ResonantCavity (#536)Peter Reininger , Stefan Kalchmair, Hermann Detz, Tobias Zederbauer, AaronMaxwell Andrews, Werner Schrenk, Gottfried StrasserVienna University of Technology Center for Micro- and Nanostructures andInstitute for Solid State Electronics, Floragasse 7, 1040 Vienna, Austria ContentThe performance of a quantum well infrared photodetector (QWIP) can besignificantly enhanced by combining it with a photonic crystal slab (PCS).Additionally, instead of indirect reflection measurements for characterization ofphotonic crystal structures, the resonances can be directly observed in thephotocurrent spectrum. To do so the device is illuminated with a Globar lightsource and the photocurrent response is measured with a Fourier transforminfrared spectrometer. The photocurrent spectrum of a PCS-QWIP exhibitspronounced resonance peaks that arise from an increased photon lifetime in thedetector material. A more elaborate experimental characterization was carriedout to determine the photonic bandstructure by bandstructure mapping1.Photocurrent spectra were measured for incident angles ranging from 0° to 70°along the Γ-M and the Γ-K direction. Higher order modes can be identified byvarying the slab-to-PC ratio d/a as we have shown previously2 . Anotherimportant feature of PCS-QWIPs is an increase of the specific detectivity D*. Theenhancement is maximal if a photonic crystal resonance coincides with the peakabsorption of the QWIP. To accurately characterize the device performancesingle-mode mid-infrared lasers were used to illuminate the device. Laser beamsare spatially and spectrally well confined and, hence ideal to measure thedetector performance. Generally, the reduction of the doping concentrationresults in a lower noise current, however the responsivity decreases as well. Byusing a PCS as resonant cavity the photon lifetime in the QWIP material isincreased and therefore a higher responsivity without increase of the dark currentcan be optained3. In fact, the holes of the PCS reduce the effective detectorvolume, which decreases the dark current noise compared to a standard QWIP.The measured noise current spectral density S* of the PCS-QWIP is less thanhalf of S* of a standard QWIP, although the effective detector volume is reducedby only 25% due to the PC holes. The additional noise current reduction isattributed to Fermi level pinning of the electron potential of the holes of the PCS.We show that the increased responsivity and decreased dark current noise of alow doped PCS-QWIP enhances the specific detectivity by up to 20 times4. References1 S. Schartner, S. Golka, C. Pflügl, W. Schrenk, A. M. Andrews, T. Roch, and G. Strasser, Appl. Phys. Lett., 89,151107 (2006) 2 R. Gansch, S. Kalchmair, H. Detz, P. Klang, A. M. Andrews, W. Schrenk, and G. Strasser, Opt.Exp., 19, 15990 (2011) 3 S. Kalchmair, H. Detz, G. D. Cole, P. Klang, M. Nobile, R. Gansch, C. Ostermaier, W.Schrenk, and G. Strasser, Appl. Phys. Lett., 98, 011105 (2011) 4 S. Kalchmair, R. Gansch, S. I. Ahn, A. M. Andrews,H. Detz, T. Zederbauer, E. Mujagic, P. Reininger, G. Lasser, W. Schrenk, and G. Strasser, Optics Express, 20, 5622(2012)

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Detectivity Enhancement:The detectivity enhancement calculated from the PCS-QWIP detectivity normalized by the standard QWIPdetectivity.

Normalized photocurrent:Normalized photocurrent spectra of a standard QWIP and a PCS-QWIP. The inset shows a sketch of thefabricated PCS-QWIP.

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ThP1-27 | Free-Carrier Refractive Index Contributions andTuning Performance of InGaAsP Laser Diodes (#549)Georgios Kyritsis , Nick ZakhleniukUniversity of Essex School of Computer Science and Electronic Engineering,Wivenhoe Park, COLCHESTER, CO4 3SQ, Great Britain ContentWavelength tunable laser diodes (TLDs) are widely used in modern opticalcommunications, sensing and optical component characterisation. The threemain physical mechanisms of the wavelength tuning are the thermal tuning, theelectro-optic tuning and the free-carrier (FC) injection tuning. These mechanismshave been thoroughly studied in many publications for a variety of semiconductormaterials [1, 2]. There are also many experimental studies of FC injection tuningin TLD devices [3]. However in the latter case one usually observes thecombined tuning effect and it is very difficult to find out the role and thecontributions of various refractive index change mechanisms to the overallwavelength tuning. The usual approach is to split and consider independently theoptical and the carrier transport problems, but this is not what usually takes placein real devices. In this paper we present to the best of our knowledge, the firstcomprehensive numerical model of TLD operation with wavelength tuning basedon simultaneous consideration of optical and FC transport phenomena incomplex multi-section device. A simulation model of a three-section InGaAsPTLD operating at 1550 nm with a bulk optical cavity was developed, usingCrossLight software. Our main attention here is focused on the investigation ofvarious FC physical mechanisms of the refractive index change and the influenceof material parameters on the tuning performance of each section of the TLD andtheir combined effect. Fig. 1 demonstrates contributions of the FC plasma effectand the changes in the interband transitions to the effective refractive indexchange, as a function of the injection current (bias). The latter contribution iscalculated using the Kramers-Kronig relations (K-K effect). We show that the K-Keffect gives a dominant contribution to the refractive index change. However notall available index change leads to further wavelength tuning. Fig. 2 shows thewavelength tuning of the DBR section. We have achieved ~ 10 nm of bluewavelength shift. Wavelength tuning saturates after ~ 1 V of bias, although therefractive index still changes with further bias increase. The possible physicalreason for this is that there is a significant modification of the lasing spectrumwith the tuning depth and decrease of sidemode suppression, which makes itdifficult to select a particular lasing mode. We also report on the effect of variousmaterial and design parameters on the device tuning performance. References[1] B.R. Bennett, R. A. Soref, and J. A. Del Alamo, "Carrier-induced change in refractive index of InP, GaAs, andInGaAsP", IEEE J. Quantum Electron., vol. 26, pp. 113-122, 1990. [2] J.-P. Weber, "Optimization of the carrier-induced effective index change in InGaAsP waveguides-application to tunable Bragg filters", IEEE J. QuantumElectron., vol. 30, pp. 1801-1816, 1994. [3] J. Buus, M.-C. Amann, and D. J. Blumenthal, Tunable Laser Diodes andRelated Optical Sources, Hoboken, NJ: John Wiley & Sons, 2005.

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Figure 1:Refractive index as a function of current (bias) in a DBR section and different mechanisms of FCcontributions.

Figure 2:DBR wavelength tuning due to FC plasma effect (1), Kramers-Kronig effect (2), and the combined effect(3).

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ThP2-1 | An analysis of Hall mobility in as-grown and annealedn- and p-type modulation doped Ga0.68In0.32NyAs1-y /GaAsquantum wells (#359)Fahrettin Sarcan 1, Omer Donmez1, Mustafa Gunes1, Ayse Erol1, M. CetinArikan1, Janne Puustinen2, Mircea Guina2

1Istanbul University, Science Faculty Department of Physics, 34134 Istanbul,Turkey 2Tampere University of Technology Optoelectronics Research Centre,Korkeakoulunkatu 3, 3720 Tampere, Finland ContentIn this study, we investigate the effect of annealing and nitrogen amount onelectronic transport properties in n- and p-type doped Ga0.68In0.32NyAs1-y/GaAsquantum well (QW) structures with y = 0, 0.9, 1.2, 1.7. The samples are thermalannealed at 700oC for 60s and 600s and Hall Effect measurements have beenperformed between 10 and 300K. The analysis of Hall mobility is carried outusing an analytical model considering dominant scattering mechanisms. Drasticdecrease is observed in electron mobility of n-type N-containing sample and N-free samples due to the possible N-induced scattering mechanisms andincreasing effect mass of the alloy. The temperature dependence of electronmobility have almost temperature insensitive characteristic, on the contrary, for p-type samples, hole mobility is decreased drastically at T > 120K. The holemobility is increased as N concentrations increase, because of decreasing latticemismatch. The results show that thermal annealing improves crystal quality andincrease carrier mobility. The analytical mobility calculations exhibit that interfaceroughness scattering is dominant at low temperatures in the n-type and p-typesamples. At high temperature regime, N-related alloy scattering is dominant overphonon scattering for n-type samples. At low temperature regime, hole mobilityare higher as a factor of about 3-4. However, at high temperatures (T > 120), themobility of p-type samples is restricted by scattering of optical phonons. Becausethe valance band discontinuity is small compared to the conduction band, alsothermionic transport of holes from quantum well to the barrier material, GaAs,contributes to the mobility at high temperatures that result in a decrease inmobility.

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ThP2-2 | 3D Modeling of FINFET (#377)Samson Mil'shtein 1, Brian Zanchi21University of Massachusetts Lowell Electrical and Computer Engineering, Ball301, 1 University Ave, Lowell, Massachusetts 01854, United States2University of Massachusetts Lowell Electrical and Computer Engineering, Ball301, 1 University Ave, Lowell, Massachusetts 01854, United States ContentThe tendency to have better control of the flow of electrons in a channel of FieldEffect Transistors (FETs) did lead to design of two gates in JFETs, field plates invariety of MESFETs and HEMTs, and finally to a gate wrapping around threesides of a channel in a FINFET. With the enhanced control trend performance ofall FETs is still challenged by carrier mobility dependence on the strengths ofelectrical field along the channel. In recent years we did study performance ofMESFETs and HEMTs manufactured by semiconductor companies, wheredesign was based on our novel concept of tailoring the electrical field along achannel of FETs. As a result of 1D modeling we demonstrated significantimprovement of transconductance in FINFET, if the electrical field was properlyshaped [1]. However in cases, when the ratio of FINFET volume to its surfacedramatically decreases, one should carefully consider the surface boundaryconditions of the device. Small physical dimensions of FINFET motivated us todo 3D modeling. The dual-gate of Si with cross section 20nmx80nm carries two30nm long gates. In order to improve transistor performance we modeled andcompared this FINFET with two gates, as the same voltage was applied to bothgates, with the device where the voltage Vg1> Vg2 and in addition the spacing inthe devise was as follow: source to 1st gate distance was 30nm; distancebetween gates was 30nm, however the distance between 2nd gate to drain was60nm. Changes of the distances in the device as well as different ratios of gate voltages didallow decreasing the strengths of electrical field and provided the optimal fieldprofile along the channel. As a result significant improvement oftransconductance was observed and much better linearity of FINFET amplifiersand switches is expected. Most important, that current results are different fromrecently published by our group 2D modeling. Although about same devicedimensions of the FINFETs were used and the same commercial designpackage was employed, the different outcome invites the discussion aboutlimitations of device simulators, when modeling of nano-scale devises areinvolved. Our future work is focused on comparison of quantization effects in 3Dand conventional modeling. References[1] S. Mil’shtein, “Shaping Electric Field in Heterostructure Devices”, Microelectronics Journal, vol. 36, no. 3-6, pp.319-322, (2005).

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FinFET Structure:3D FinFET structure generated by Atlas

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ThP2-3 | Magnetoresistance and Hall Effect studies in n- and p-type GaInNAs/GaAs modulation doped quantum wellstructures (#387)Mustafa Gunes 1, Metin Aslan2, Ferhat Nutku1, Ayse Erol1, M. Cetin Arikan1

1Istanbul University Science Faculty, Department of Physics, 34134 Istanbul,Turkey 2Sakarya University Faculty of Arts and Sciences, Department of Physics, 54187Sakarya, Turkey ContentWe present a study of the electronic transport properties of 2D carriers in n- andp-type Ga1-xInxNyAs1-y/GaAs modulation-doped quantum well structures withhaving different nitrogen concentrations using Hall, Photo-Hall andmagnetoresistance measurements. Photo-Hall effect results showed thatillumination with IR LED caused an increment in mobility for n-modulationstructures, which can be explained in terms of photo-generated excess carriers,but negligible changing on mobility for the p-type modulation doped sample.Magnetoresistance (MR) measurements at dark depicted a negative contributionto the magnetoresistance effect and decreases with increasing temperature for n-type modulation samples. When the samples are illuminated, negative MRcurves started to be positive at lower temperatures. The observation of negativeMR is explained in terms of quantum corrections to the classical Drudeconductivity, mainly weak localization effect. Due to N-related disorder in thestructure electron and N interaction induces weak localization. No MR wasobserved for the p-type modulation doped sample neither at dark not underillumination.

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ThP2-4 | Low-temperature electronic transport mechanismsdeduced from noise measurements in quantum-well infraredphotodetectors (#422)Fernando Massa Fernandes 1, Alvaro Diego Bernardino Maia1, Marcel DosSantos Claro1, Euzi Conceição Fernandes da Silva1, Alain Andre Quivy1, Marcelade Freitas Mendonça2, Gustavo Soares Vieira2, Nancy Mieko Abe2, Roberto YujiTanaka2, Angelo Passaro2

1Instituto de Física, Universidade de São Paulo Laboratório de Novos MateriaisSemicondutores, PO Box 66318, São Paulo, Sao Paulo, 05314-970, Brazil 2Instituto de Estudos Avançados, Centro Técnico Aeroespacial, Trevo CoronelAviador José Alberto Albano do Amarante, no 1, São José dos Campos, SãoPaulo, 12228-001, Brazil ContentQuantum-well infrared photodetectors (QWIPs) of III-V materials are nowadaysthe devices of choice when focal plane arrays (FPAs) of high quality are needed. Although QWIPs technology has now reached a certain maturity, some problemsstill remain. In general, their performance is strongly influenced by the presenceof a large dark current that is the major source of noise that limits their detectivity.Therefore, noise measurements are important but they are generally considereddifficult to be carried out, especially below the temperature of liquid nitrogen(77K), as a consequence of the very low level of the electric signals and of theparasitic sources of noise coming from the other equipments or components ofthe experiment. We grew, processed and fully characterized a QWIPcontaining 50 AlGaAs/GaAs quantum wells operating around 9.4um. In the QWIPproject the contact doping level was adjusted in such a way that no chargeshould be transferred in or out of the quantum well structure at zero bias. Fromvery careful measurements, we could experimentally determine the noise of thedark current and were able to successfully compare the data to a theoreticalmodel involving the recombination of electrons from the first excited state to thefundamental state of the quantum well. The good agreement between thetheoretical and experimental results may indicate that, even at temperatures aslow as 30 or 10K, the dark current might be originated by carrier transport in thecontinuum rather than by the defect-assisted tunneling through the AlGaAsbarriers, as usually assumed in the literature. The simulation of the noise curveswas based on the capture probability of the carriers into the wells, which dependson the capture time and drift velocity. The capture time was calculated with aformalism which takes account of the carrier wave function. The calculation wasdone in the effective-mass approximation and assuming a uniform appliedelectric field. The drift velocity was obtained from a known semi-empirical modelfor GaAs, and the saturation velocity was finally used as a fitting parameter inorder to adjust the experimental noise curves. The low-temperature dependenceof the saturation velocity obtained from the fits showed approximately a 1/Tbehavior as usually observed at higher temperature.

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References1. Quantum Well Infrared Photodetectors, Physics and Application., H. Shneider and H. C. Liu, Springer 2007 2. R.Ferreira and G. Bastard, Physical Review B 40, 1074 (1989) 3. J. S. Blakemore, Journal of Applied Physics 53(10)(1982)

QWIP noise at 10K:Current noise measured experimentally (full circles) and calculated (stars) after calculating the capturetime and using the saturation velocity as a fitting parameter to the experimental noise data

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Saturation velocity:Temperature dependence of the saturation velocity obtained by fitting our experimental noise data at 10,30, 50 and 70K. The 300K value in the figure comes from the literature and is in excellent agreement withour low-temperature results.

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ThP2-5 | Hydrogen ad-atoms resonant tramps in graphenenanoribbons (#437)Monica Pacheco 1, Jhon González2, Luis Rosales1

1Universidad Técnica Federico Santa María, Avda España 1680, Valparaíso,Chile 2International Iberian Nanotechnology, Av. Mestre Jose Veiga, 4715-330, Braga,Portugal ContentWe report a theoretical study of transport properties of a system formed by agraphene nanoribbon with adsorbed hydrogen atoms along two stripes crossingthe ribbon. Considering ordered and random distributions we study the effects onthe transport, of the number and position of H atoms, the width of the stripes, andthe separation between them. When hydrogen atoms interact with graphene itcreates localizes states, this leads to electronic confinement and the apparition ofresonant states along the heterostructure. We have calculated the local densityof states (LDOS) and the conductance of these systems described by a single-band tight binding Hamiltonian by using Green's function formalisms within realspace renormalization techniques. We found evidence of the presence ofresonant states in both, the local density of states and in the conductance,regardless of whether the distribution of hydrogen atoms is ordered orrandomized.

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Fig. 1:Schematic view of four ordered geometries under study.

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Fig. 2:Local density of states for the carbon atoms in the D2 barrier configuration separated L = 15 in a metallicribbon N = 11. Panel (a), (b) and (c) correspond to the contour plots of some resonant states within theseparation region, indicated with arrows i

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ThP2-6 | The role of dislocation-induced scattering inelectronic transport in GaxIn1-xN alloys (#439)Omer Donmez1, Mustafa Gunes1, Ayse Erol1, M. Cetin Arikan 1, Naci Balkan2,William Schaff3

1Istanbul University Physics Department, Science Faculty, 34134 Istanbul,Turkey 2University of Essex School of Computer Science and Electronic Engineering,Colchester, Colchester, CO4 3SQ, Great Britain3Cornell University Department of Electrical and Computer Engineering, Ithaca,New York, 14853, United States ContentElectronic transport in unintentionally doped GaxIn1-xN alloys with various Gaconcentrations (x = 0.06, 0.32, 0.52) is studied. Hall Effect measurements areperformed at temperatures between 77K and 300K. Temperature dependence ofcarrier mobility is analysed by an analytical formula based on 2D degeneratestatistical by taking into account of all major scattering mechanisms for a twodimensional electron gas confined in a triangular quantum well between GaxIn1-xNepilayer and GaN buffer. Experimental results show that as the Ga concentrationincreases, mobility not only decreases drastically but also becomes lesstemperature dependent. Carrier density is almost temperature independent andtends to increase with increasing Ga concentration. The weak temperaturedependence of the mobility may be attributed to screening of polar opticalphonon scattering at high temperatures by the high free carrier concentrationwhich is in the range of 1014 cm-2. In our analytical model, the dislocation densityis used as an adjustable parameter for the best fit to the experimental results.Our results reveal that, in the samples with lower Ga compositions and carrierconcentrations, alloy and interface roughness scattering are the dominantscattering mechanisms at low temperatures, while at high temperatures; opticphonon scattering is the dominant mechanism. In the samples with higher Gacompositions and carrier concentrations, however, dislocation scatteringbecomes more significant and suppresses the effect of LO phonon scattering athigh temperatures, leading to an almost temperature-independent behaviour.

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ThP2-7 | Fine tuning of single barrier thermal resistance in Ge/Si multilayers (#442)Peixuan Chen , Jianjun Zhang, Armando Rastelli, Oliver SchmidtIFW-Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany ContentThermoelectric materials, which can directly convert heat into electricity (and viceversa), are very appealing for applications ranging from power generation tomicroprocessor cooling. However, with the exception of a few niche applications,these solid-state energy converters have proven too inefficient to be practical.Now, engineers and scientists are using nanotechnology to create novelsemiconducting materials that could finally make thermoelectricity a widely usedtechnology. One of the approaches to increase the efficiency of a thermoelectricconverter is the reduction of the lattice thermal conductivity k of the employedmaterials. Previous work on nanoscale thermal transport has demonstrated thatin some cases nanostructuring can reduce k of a material below that of itsdisordered alloy counterpart, and can even beat the amorphous limit [1-4]. In ourprevious work, by using multilayers of Ge nanodots separated by Si spacers, weshowed that it was possible to precisely control the thermal conductivity at thenanoscale by simply varying the thickness of the Si spacer [5]. The experimentalresults suggested that phonon transport in the Si spacers was ballistic and thatthe Ge dot layers acted as phonon scattering barriers with thermal resistancevalues comparable to the value predicted by diffusive mismatch mode (DMM).However, it is still not clear how to control the Ge barrier thermal resistance. Inour current work, we study the dependence of Ge barrier thermal resistance onthe amount of deposited Ge. By gradually increasing the amount of depositedGe, flat Ge/Si multilayers with different Ge thickness (see sketch in figure 1) andnanodot Ge/Si multilayers with different dot density were obtained. We performedthermal conductivity measurements by using the differential 3-omega method [6]and found that: the Ge barrier thermal resistance is linearly proportional to thedeposited Ge amount, as shown in figure 2(a). Because of the linear dependenceof the Ge barrier resistance on the amount of deposited Ge, our resultsdemonstrate that the thermal conductivity of a Ge/Si multialyer can be preciselycontrolled by the amount of deposited Ge even when Si spacer thickness is fixed,as shown in figure 2(b). References[1] W. Kim et al., Phys. Rev. Lett. 96, 045901 (2006). [2] S. M. Lee, D. G. Cahill and R. Venkatasubramanian Appl.Phys. Lett. 70, 2957 (1997). [3] M. L. Lee and R. Venkatasubramanian Appl. Phys. Lett. 92, 053112 (2008). [4] C.Chiritescu et al., Science 315, 351 (2007). [5] G. Pernot et al., Nature Materials 9, 491 (2010). [6] T. Yamane et al.,J. Appl. Phys. 91, 9772 (2002).

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Figure 1:Schematic picture of a Ge/Si multilayer.

Figure 2:(a) Ge barrier thermal resistance as a function of deposited Ge amount per period; (b) Thermalconductivity as a function of deposited Ge amount per period.

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ThP2-8 | A Study on Structural and Electronic Properties ofGaAsN and GaAsBi Alloys (#484)Metin Aslan, Battal Gazi Yalcin Sakarya University Physics, Serdivan, 54187 Sakarya, Turkey ContentWe have performed first principles method to investigate structural and electronicproperties of GaAsyN1-y and GaAsxBi1-x ternary semiconductor alloy using DensityFunctional Theory (DFT) and pseudopotantial method within the GeneralizedGradient Approximations (GGA). The zinc-blende phase is found stable forGaAsN and GaAsBi alloys. In this study we investigate the both bowingparameters with changing Bi concentration in GaAsBi and N concentration inGaAsN alloy. By using the bowing parameter of GaAsBi and GaAsN alloys weinvestigate the bandgap energy and lattice constant of both alloys which areimportant for wide range device application. For studied materials, latticeparameters and band gap energies are compared with available theoretical andexperimental works.

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ThP2-9 | Transport through nanoscopic 3D constrictions (#492)Pedro Pereyra 1,2, Stefan Geisler3, Dieter Weiss3

1Universidad Autónoma Metropolitana-Azcapotzalco Ciencias Básicas, Av. S.Pablo 180, 02200 Mexico, Mexico2University of Regensburg Institut für Experimentelle und Angewandte Physik,93040 Regensburg, Germany 3University of Regensburg Institut für Experimentelle und Angewandte Physik,Universitätsstrasse 31, 93053 Regensburg Germany, Germany ContentRecent measurements of hole transport through nanoscopic constrictions etchedin a highly doped (Ga,Mn)As semiconducting layer, yield a great variety ofquantum transport properties ranging from coherent quasi-ballistic to diffusiveand weakly localized regime. To understand some of these results, in particularthe strong oscillations of the differential conductance (ortransconductance) induced by the gate voltage, at low bias and low temperature,we model the quasi-ballistic constriction as a 3D hole transport channel, which(effective channel) cross section changes with the gate voltage. We consideralso a bias potential that drops linearly along the x axis (with different rates in theconstriction and wide regions, according with COMSOL simulations). Tocalculate the transmission coefficents and conductance through the constrictionwe use the transfer matrix method, and derive the conductance for an arbitrarynumber of propagating modes. We also consider the presence of magneticimpurities. We evaluate the conductance as a function of the carrier energy, thespin exchange and the gate and bias voltage, both in the absence and in thepresence of a small number of magnetic impurities. Using a depletion thicknessof the order of 0.1nm/V, as measured by Sawicki et al.,1 incoming hole energiesof the order of the Fermi energy2, about 0.2eV, we found the conductanceoscillations shown in figures 1a) and 1b), assuming holes with and without spin,respectively. These results agree qualitatively with experimenal results. Toimprove this model and to account for other properties observed in theseexperiments, we are working to include the diffusive motion and temperatureeffects. References1. Maciej Sawicki, Daichi Chiba, Anna Korbecka, Yu Nishitani, Jacek A. Majewski, Fumihiro Matsukura, Tomasz Dietland Hideo Ohno, Nature Physics, 6, 22 (2010). 2. Dietl T., Ohno H., Matsukura F., Physical Review B, 63, 195205(2001).

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Fig1.gif:Oscillations in the conductance of holes, with spin (left) and without spin (right), due to channel crosssection depletion induced by the gate voltage.

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ThP2-10 | Quantum transport through aromatic molecules (#509)Judith Ojeda1, R. R. Rey-González 2

1Universidad Pedagógica y Tecnológica de Colombia Escuela de Física, Grupode Física de Materiales, Tunja, Colombia 2Universidad Nacional de Colombia - Bogotá Facultad de Ciencias,Departamento de Física, Grupo de Óptica e Información Cuántica, Carrera 30Calle 45-03, C. P. 111321 Bogotá, Colombia ContentIn recent decades has been a growing interest in the study of molecular systemsdue to possible use in electronic nanodevices. In particular, molecules andmacromolecules with sizes ranging between 0.2 nm and 10 nm are valid objectsfor use in this area of knowledge, this molecules are grow on surfaces forobtaining devices with particular electrical characteristics. One of the majorchallenges of nanotechnology is the molecular manipulation that takesadvantage of self-assembling and self-organization properties that possess manyorganic molecules which are arranged spontaneously from its constituent units. Aromatic ring systems are prototypes that attract attention due to its electricalproperties are potentially useful (semiconductors properties) and they are stable,flat and symmetrical structures. However, its electronic properties remainunclear, there are experimental reports showing an insulator, semiconductor ormetallic behaviour In this work, we analyze the transport properties througharomatic molecule between two metal contacts. It is modelled as a homogeneousand plane segment considering two possible configurations: a biphenyl (C6H5)2

and naphthalene (C10H8). The Hamiltonian of the system is described into thetight binding approximation with one orbital per site and nearest-neighbourinteractions only. The current and conductance properties are calculated usinggeneralized techniques Green functions.

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ThP2-11 | Effect of localized magnetic moments configurationson the dynamics of electron wave packet -- phase-spaceapproach. (#547)Maciej Wołoszyn , Bartłomiej SpisakAGH University of Science and Technology Faculty of Physics and AppliedComputer Science, al. A.Mickiewicza 30, 30-059 Krakow, Poland ContentSubstantial progress in nanotechnology and in detecting techniques leads to newpossibilities in the physics of single-electron transport in solid nanosystems. Oneof the interesting problems is the influence of the localized magnetic momentconfigurations on the dynamic processes of electronic transport. In order todescribe the dynamics of the electron wave packet through the region ofnanometer size containing a number of localized magnetic moments, the phase-space approach based on the Wigner function is adopted in our computersimulations. The influence of different magnetic moments configurations on thetransmission times and the quantum trajectories of the wave packet through thediscussed systems is investigated. Another factor included in the discussion isthe effective size of the electron's wave packet and its initial phase-spaceposition. References[1] Hillery M, O’Connell R F, Scully M O, and Wigner E P. Distribution functions in physics: Fundamentals. Phys. Rep.106 (1984) 121. [2] Lee H-W. Theory and application of the quantum phase-space distribution functions. Phys. Rep.259 (1995) 147. [3] Dragoman D. Phase space formulation of quantum mechanics. insight into the measurementproblem. Phys. Scr. 72 (2005) 290. [4] Dragoman D. Wigner distribution function expression for the tunnelling time inquantum resonant structures. Optical and Quantum Electronics 29 (1997) 79. [5] Wong C-Y. Explicit solution of thetime evolution of the Wigner function. J. Opt. B: Quantum Semiclass. Opt. 5 (2003) S420. [6] Zhang H, Tang W, ZhaoX. Spin transmission in a series of magnetic barrier structure. Physica B 389 (2007) 281. [7] Ibrahim I S, Peeters F M.The magnetic Kronig–Penney model. Am J Phys 63 (1995) 171.

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ThP2-12 | Electron transport properties of MoS2 Nanotubesand Nanoribbons (#184)Ezgi Erdogan , Gotthard SeifertTU Dresden Physical Chemistry, Mommsenstr.13, 01062 Dresden, Germany ContentElectron transport properties of MoS2 Nanotubes and Nanoribbons We havestudied the electron transport properties of MoS2 nanotubes and nanoribbons,using a density functional theory tight binding method in combination with aGreen's function formalism. The results show how the edge termination in thenanoribbons determines essentially their electronic properties. The resultsdemonstrate the tuning of the electronic band gap by the edge type (arm-chairvs. zig-zag) and the edge termination (Sulfur vs. Molybdenum). In contrast, MoS2nanotubes posses rather robust electron transport properties, due to the absenceof volatile edges. The results are discussed with respect to the application ofsuch MoS2 nanostructures for corresponding electronic devices. ReferencesE.Erdogan, I.Popov,A.Enyashin and G.Seifert,Eur. Phys. J. B (2012) 85: 33

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ThP2-13 | Photoelectrochemical characteristics of onedimensional nanostructured silicon for optoelectronicapplications (#241)Shao-Long Wu , Guo-An Cheng, Rui-Ting Zheng, Ting ZhangBeijing Normal University Key Laboratory of Beam Technology and MaterialModification of Ministry of Education, College of Nuclear Science andTechnology, Beijing China ContentIn recent decades, one dimensional nanostructured semiconductor materials(1DNSMs) have attracted much attention due to their unique physical andchemical properties. One dimensional nanostructured silicon (1DNSi) play animportant and intriguing role in the 1DNSMs because of the compatibility with theSi-based microelectronics as well as their extraordinary properties, which makenanostructured Si perform a promising candidate for applications in thephotovoltaics, photodetectors, photoelectrolysis, photochemical catalysis,sensors, thermoelectricity, and so on. In this paper, one dimensionalnanostructured Si were prepared by metal assisted chemical etching (MacEtch)method, which is low-cost and widely used to fabricate large-area onedimensional silicon nanostructures. The nanostructured Si exhibit excellentoptical absorption properties (> 98%) in the range of 200―1000 nm. The as-prepared nanostructured Si were used as photoelectrodes in aphotoelectrochemical cell for studying their photoactive characteristics. A tri-dimensional “bulk” heterojunction was formed when the nanostructured Si wereimmersed in the electrolyte. In this novel architecture, the light absorption isalong the axle direction of nanostructures, and the collection of photogengeratedcarriers is along the radial direction (which may result in an enhancement ofcollection efficiency because of the small transport distance). In this case, thesubstantial photoelectrochemical responses of nanostructured Si are envisionedaccording to the combination effects of the excellent optical absorption and theseparation of the directions of light absorption and photo-carriers collections.Different morphological nanostuctured Si with or without removal of Agnanoparticles obtained in various synthesized conditions were systematicallyresearched under the irradiation of white, red and yellow light LEDs. Goodphotovoltaic properties can be extracted from the photocurrent vs. voltage (J―V)characteristics. High photoresponsivity (> 0.6 A/W) and large photocurrent-to-darkcurrent ratio (> 103) were obtained. The generation, transport and collectionof photo-carriers in various morphological samples were detailed discussed. Ourresults imply that the tri-dimensional junctions of one dimensional nanostructuredSi perform a good optoelectronic application prospects.

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Graphical Abstract:Schematic of photoelectrochemical characteristics measurement (a) and energy band program (b).

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ThP2-14 | Andreev levels in semiconductor nanowireJosephson junction with strong spin-orbit interaction (#269)Tomohiro Yokoyama 1, Mikio Eto1, Yuli Nazarov2

1Keio University Faculty of Science and Technology, 3-14-1 Hiyoshi, Kohoku-ku,Yokohama 223-8522, Japan 2Delft University of Technology Kavli Institute of Nanoscience, Lorentzweg 1,2628 CJ Delft, Netherlands ContentIn Josephson junctions, discrete energy levels of quasiparticles are formed dueto the Andreev reflections at the interfaces, called Andreev levels. TheJosephson current flows through the levels in the presence of phase difference jbetween left and right superconductors. In this study, we theoretically investigatea superconductor-semiconductor nanowire-superconductor Josephson junctionwith strong spin-orbit (SO) interaction in the nanowire, e.g., InAs nanowire [1].We show that spin-split Andreev levels are asymmetric with respect to j in thepresence of magnetic field, which results in the Josephson current of I (j) = -I (-j).In consequence, the critical current is different in the positive and negativedirection, which qualitatively agrees with experimental [2]. In our formulation, thetransport through a nanowire is described in terms of the scattering matrix. Thescattering matrices S (E) for electrons and S* (-E) for holes are given by therandom matrix theory for the diffusive regime, where E is an energy measuredfrom the Fermi level. To take into account a weak energy-dependence, weintroduce a single resonant pole in the scattering matrices, assuming that thelength of nanowire L is comparable to the coherent length. In the presence ofmagnetic field, the Zeeman effect is considered as a spin-dependent phase ±qB =±|g|mBBL/(2vF) accompanied by the transport through the nanowire. The Andreevlevels are obtained by solving the Bogoliubov-de Gennes equation. Figure (a)shows the Andreev levels in the absence of magnetic field as functions of j. |D| isthe magnitude of order parameter in the superconductors. There are threeconduction channels in the nanowire. We find the Kramers’ degeneracy at j = 0and ±p. When j ≠0, ±p, the spin-splitting of levels is induced by the SO interactionand time reversal symmetry breaking, where Dn (j) = -Dn (-j) [3]. Figure (b) showsthe Andreev levels when qB = 0.03p. We obtain an asymmetric spin-splitting |Dn

(j)| ≠ |Dn (-j)| due to the interplay between the SO interaction and Zeeman effect.In Figs. (c) and (d), the Andreev levels and Josephson current are shown whenqB = 0.55p. The discontinuous behaviors of the current at j ≈ 0 and -0.4p areattributable to the zero points of the lowest level in Fig. (c). In Fig. (d), themaximum of positive current is not equal to that of negative current. Thus theeffect of SO interaction is reflected by the different critical current in positive andnegative directions. References[1] S. Nadj-Perge et al., Phys. Rev. B 81, 201305(R) (2010). [2] L. Kouwenhoven and S. Frolov, privatecommunications. [3] B. B`eri et al., Phys. Rev. B 77, 045311 (2008).

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figure:Andreev levels and Josephson current

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ThP2-15 | Tunneling Through Nanowire Double Quantum DotWith Phonon Interaction (#321)Fikeraddis Ahmed Damtie 1, Olov Karlström1, Carina Fasth1, Andreas Fuhrer2,Lars Samuelson1, Andreas Wacker1

1The Nanometer Structure Consortium (nmC@LU), Lund University, Box 118,SE-221 00, Lund, Sweden2IBM Research-Zurich, Rüschlikon, Zurich, Switzerland ContentStudies of transport properties of low dimensional semiconductor structures playan important role both in understanding the basic physics and in an advancedtechnological applications. We analyze the current spectrum for double quantumdot in a semiconductor nanowire by taking in to account phonon scattering.Generally, in double dot structures transport is restricted to the alignment oflevels which can be tuned individually for both dots by gates. [1] This providescharacterstic current spectra as shown in Fig 1. Tunneling processes can beeither elastic or involve the exchange of energy with other degrees of freedom. Inthe elastic case, the levels in the two dots need to be aligned for an electron toflow which is the resonant tunneling . A significant contribution to the current canalso be obtained from inelastic processes by emitting or absorbing phonons andphotons. The dynamics for the tunneling rates were calculated by using the firstorder von-Neumann approach [2] which we exteded by adding phononscattering. The phonons are modeled by using deformation potential interactionbetween the electrons and an acoustic phonon mode. We compared oursimulation results with the experimental data of a nanowire double dot structure[3] .In particular we focus on the Pauli spin blockade for the transition T (1, 1) →S(2, 0) which is a prominent effect in double quantum dot systems. References[1] W. G. van der Wiel et al., Rev. Mod. Phys. 75, 1 (2002). [2] J. N. Pedersen, B. Lassen, A. Wacker, and M. H.Hettler, Phys. Rev. B 75, 235314 (2007). [3] C. Weber , A. Fuhrer, C. Fasth, G. Lindwall, L. Samuelson, A.Wacker, Phys. Rev. Lett. 104, 036801 (2010).

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Figure 1:Experimental current response by tuning the level energies [3]

Figure 2:Simulation result by assuming ground and excited states in both dots including phonon scattering

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ThP2-16 | Hole mobility in InP nanowires: effects oftemperature, strain and width (#327)Mariama Rebello Sousa Dias 1,2, Adalberto Picinin1, Victor Lopez-Richard1,Sergio E. Ulloa2, Leonardo K. Castelano1, José Pedro Rino1, Gilmar E. Marques1

1Universidade Federal de São Carlos Física, Rodovia Washington Luiz, Km 235,São Carlos, São Paulo, 13565-905, Brazil 2Ohio University Physics & Astronomy, Clippinger Labs 251B, Athens, Ohio45701, United States ContentTransport properties of holes in InP nanowires were calculated considering theeffect of temperature and the presence of realistic strain fields. The mobility ofholes is obtained analytically by considering electron-phonon interactionvia deformation potential through longitudinal optical (LO) phonons. Usingmolecular dynamics with realistic force potentials, we simulate nanowirestructures and the associated phonon density of states; the structures showeffects of LO phonon energy renormalization due to the reduced dimensionalityand variation of the phonon lifetimes important for carrier mobility. Our mobilitycalculations include heavy and light hole subbands in a Luttinger Hamiltonianformalism and consider how the valence band ground state changes betweenlight- and heavy-hole character, as both the strain field configuration and thenanowire size are changed. Depending on the dimensions and characteristics ofthe nanowire, we find interesting sudden changes in the mobility, which arise withthe onset of a resonance between the LO phonon frequencies and the subbandseparation between the ground and first hole state. We will present the effect ofstrains, size, and temperature on this resonant behavior and discuss theconsequences for carrier mobility in these systems.

Light hole mobility ratio:Monotonic to non monotonic behavior of the light hole mobility ratio versus wire width for different valuesof strain at kz=0.

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ThP2-17 | Current transport through single molecules (#331)Artur Erbe 1, Youngsan Kim2, Jannic Wolf3, Thomas Huhn3, Elke Scheer2

1Helmholtz-Zentrum Dresden-Rossendorf FWIO-T, Bautzner Landstr. 400,01328 Dresden, Germany 2University of Konstanz Physics, Universitätsstr. 10, 78464 Konstanz, Germany 3University of Konstanz Chemistry, Universitätsstr. 10, 78464 Konstanz,Germany ContentThe goal of molecular electronics is the use of molecular structures as activecomponents in electrical circuits. In order to achieve this goal basic questions likethe connection between molecules and metallic contacts and the conductance ofa metal-molecule contact need to be addressed. Using the mechanicallycontrollable breakjunction technique we have performed transport experimentsthrough single ethyne molecules attached to gold electrodes via thiol, nitro, andcyano anchoring groups. We have measured current-voltage characteristicsinside a liquid cell. By fitting the experimental curves to a single-level resonanttunneling model we are able to extract both the position of the molecular orbitalclosest to the Fermi energy and the strength of the metal-molecule coupling. Wecompare the results to ab initio calculations which give further insight into thetransport properties. The dependence of the I-V characteristics on the variousanchoring groups shows clearly that these groups affect the coupling strengthbetween metal and the molecules as well as the position of the molecular energylevels [1]. Measurements at low temperature allow for the recording of inelastictunneling spectroscopy (IETS). We show how we can use this information toverify that single molecules are contacted [2]. References[1]Linda A Zotti, Thomas Kirchner, Juan-Carlos Cuevas, Fabian Pauly, Thomas Huhn, Elke Scheer, and Artur Erbe,"Revealing the role of anchoring groups in the electrical conduction through single-molecule junctions." Small 6,1529 (2010). [2] Youngsang Kim, Torsten Pietsch, Artur Erbe, Wolfgang Belzig, and Elke Scheer "Benzenedithiol: ABroad-Range Single-Channel Molecular Conductor". Nano Letters 11, 3734 (2011).

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Single molecule transport:Schematic drawing (left) of the experimental setup and typical I-V curve including a fit to the single levelmodel (right

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ThP2-18 | The electron gas in GaAs/AlGaAs modulation dopedco-axial nanostructures (#391)Guido Goldoni 1,2, Andrea Bertoni2, Miguel Royo Valls2

1University of Modena and Reggio Emilia Physics, VIA CAMPI 213/A, 41125Modena, Italy 2CNR NANO S3, VIA CAMPI 213/A, 41125 41125, Italy ContentSemiconductor nanowires (NWs) of the core-shell type [1] offer the fascinatingpossibility to form axially symmetric high-mobility electron gases, similar totraditional planar 2DEGs formed in modulation doped GaAs/AlGaAsheterojunctions, but with a different topology. In this contribution we shall discussthe nature and the formation of electronic states, both at zero field and in theQuantum Hall regime, in doped co-axial hetero-junctions and quantum wells.Calculations have been conducted within a k.p approach on symmetry compliantgrids, including the self-consistent field of the electron gas at the mean-field levelwith exchange-correlation corrections [2]. This allowed to treat explicitly thecompositional profiles and remote doping in complex core-multi-shellGaAs/AlGaAs NWs with diameters in the experimentally relevant tens ofnanometer range. We show that the prismatic symmetry of nanowires –usuallyhexagonal in GaAs – may lead to the coexistence of quasi-2D layers, along thefacets of the hetero-interface, and quasi-1D channels, along the edges of theinterface, as shown in the figure. Localization and dimensionality of the quantumstates are strongly dependent on the n- or p-type and amount of doping, andeither 2DEGs with cylindrical symmetry or coupled quasi-1D channels or bothmay form [2]. Occupation and dimensionality of the carrier can also be controlledto a large extent by external wrap-around or back gates in a field effect transistor.Magnetic states in a transverse field can only partially be reconducted to theLandau level picture [3]. The single most important fingerprint of the electron gasformation is the detection of collective excitations by, e.g., light scattering. Therefore, we have calculated the collective excitations of the electron gas andestimated the relative intensity in Raman experiment within a multi-band RandomPhase approach. We shall discuss recent experiments in light of thesecalculations. References[1] A. Fontcuberta i Morral, D. Spirkoska, J. Arbiol, M. Heigoldt, J.R.. Morante, G, Abstreiter, "Prismatic quantumheterostructures synhesized on molecular-beam epitaxy GaAs nanowires", Small 4, 899 (2008) [2] A. Bertoni, M.Royo, F. Mahawish, G. Goldoni, "Electron and hole gas in modulation doped GaAs/AlGaAs radialheterjunctions",Phys. Rev. B 84, 205323 (2011) [3] G. Ferrari, G. Goldoni, A. Bertoni, E. Molinari, "Magnetic states inprismatic multishell nanowires", Nano Lett.. 9, 1631 (2009)

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Figure:Charge densities for conduction electron, valence holes at zero bias, or at positive or negative bias of aback gate in a field effect transistor

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ThP2-19 | Tuning electrical and magnetic properties ofcellulose films by Au nanoparticles (#409)Lyudmila Turyanska 1, Oleg Makarovsky1, Amalia Patane1, Nadezhda Kozlova2,Zhiming Liu3, Mei Li3, Stephen Mann3

1The University of Nottingham School of Physics and Astronomy, UniversityPark, Nottingham, NG72RD, Great Britain2IFW Dresden Institute for Metallic Materials, P.O. Box 270116, D-01171Dresden, Germany 3University of Bristol Centre for Organized Matter Chemistry, School ofChemistry, Bristol, BS8 1TS, Great Britain ContentMetal nanoparticles (NPs), such Au, Pt and Pd, provide a versatile system toprobe physical properties at the nanoscale of fundamental interest and ofrelevance to a wide range of potential applications that span from photonics andchemistry to biosensing [1]. Of particular interest is the prediction of unexpectedphysical effects, such as ferromagnetism in Au nanoparticles, which emerge asthe size of the NPs reaches the quantum limit [2]. Here we use Au NPs toproduce electrically conducting cellulose films with tunable electrical andmagnetic properties [3-4]. Cellulose is an attractive biopolymer as it is readilyavailable, easy to manipulate and biodegradable and can be made electricallyconducting by cellulose regeneration in Au NP aqueous dispersions [3]. Ourflexible self-supporting films contain 27 wt% to 44 wt% of Au NPs with diameterd=11.6±1.4 nm with the majority of nanoparticles located in the top 0.2-0.5 µmlayer of the 5 µm-thick film, with a deeper penetration observed at higherconcentrations of Au (Figure 1a). We show that the Au NPs provide a means oftuning the resistivity ρ from 20MΩ to 20Ω and that the mechanism of transport inthese films changes from variable range hopping (VRH) to metallic-likeconduction with decreasing values of ρ. In the regime of VRH conductivity, wehave observed negative magnetoresistance at applied magnetic fields, B, as highas 45T corresponding to a magnetic length lB= 4 nm smaller than the nanoparticlediameter (Figure 1b). Our data and analysis indicate that the negativemagnetoresistance at high B is due to the spin polarization of the Au NPs and themagnetic field induced suppression of electron spin-flips during spin-polarizedtunneling [4]. The analysis of the magnetoresistance data at various B andtemperatures, T, also suggests that the Au NPs possess a magnetic moment µ =(0.26±0.05) µB, where µB is the Bohr magneton. These observations are offundamental interest and of relevance to the investigation and exploitation of awide variety of metal nanoparticles that have emerged in the recent literature.Our findings on transport properties of Au NP-cellulose are also relevant to futureapplications that require environmentally benign and flexible conductingmaterials.

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References[1] V. I. Klimov, Semiconductor and Metal Nanocrystals: Synthesis and Electronic and Optical properties. (MarcelDekker, Inc., New York, Basel, 2004). [2] Y. Yamamoto, and H. Hori, Rev. Adv. Mater. Sci. 12, 23-32 (2006). [3] Z.Liu, M. Li, L. Turyanska, O. Makarovsky, A. Patanè, W. Wu, and S. Mann, Chemistry of Materials, 22, 2675 (2010).[4] L. Turyanska, O. Makarovsky, A. Patanè, N. Kozlova, Z. Liu, M. Li, and S. Mann, Nanotechnology 23, 045702 1-5(2012).

Figure 1:(a) Cross-section TEM image of a Au NPs/cellulose film and (inset) zoomed image of the marked area. (b)Magnetoresistance at various T. Inset: Measured and calculated T dependence of the magnetoresistanceat various B.

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ThP2-20 | Quantum well infrared photodetector based on anintersubband transition between the ground and a continuumlocalized states (#475)Germano M. Penello 1,2, Patrícia L. Souza3,2, Marcos H. Degani4,2, Rudy MassamiKawabata3,2, Mauricio P. Pires1,2, Daniel N. Micha5,1, Roberto Jakomin3,2, NelsonStudart6,2

1Universidade Federal do Rio de Janeiro - UFRJ Instituto de Física, Rio deJaneiro, RJ, Brazil 2Instituto Nacional de Ciência e Tecnologia em NanodispositivosSemicondutores - DISSE, Rio de Janeiro, RJ, Brazil 3Pontifícia Universidade Católica - PUC-Rio LabSem/CETUC, Rio de Janeiro,RJ, Brazil 4Universidade Estadual de Campinas - UNICAMP Faculdade de CiênciasAplicadas, Campinas, SP, Brazil 5Centro Federal de Educação Tecnológica Celso Suckow da Fonseca (CEFET),Petrópolis, RJ, Brazil 6Universidade Federal de São Carlos - UFSCar Departamento de Física, SãoCarlos, SP, Brazil ContentWhen designing a quantum well (QW) structure for a quantum well infraredphotodetector (QWIP) one faces the dilemma of choosing a structure in whichthe absorption occurs either between two bound states or between a bound stateand the continuum [1,2]. The former presents higher oscillator strength while thelatter favors an efficient carrier collection. Even though the bound to boundtransition has the additional advantage of achieving narrow absorption peaks,desirable for sharp wavelength discrimination in many gas detection applications,one has not much freedom in designing the structure for wavelengths shorterthan 5 µm due to the limitations imposed by the band offsets of the materialsystems. Moreover, the carrier collection mechanisms are often inefficient. In thiswork we propose a QWIP structure where the active quantum well layer issurrounded by a superlattice which gives rise to confined states with energiesabove that of the bottom of the conduction band of the barrier material [3, 4].Such structure not only leads to sharp photocurrent peaks but renders the designof QWIP structures rather versatile for energy tuning in the short wavelengthrange and benefits from an efficient miniband carrier transport, as well [4]. Figure1 shows the scheme of such structure based on InGaAs/InAlAs QWs latticematched to InP substrate. It consists of a superlattice of 11 QWs in which thecentral QW act as a “defect”, just as in a photonic crystal. The entire structurecontains 10 periods spaced by a thick barrier. The states and the oscillatorstrength for all possible transitions are calculated solving Schrodinger’s equationincluding nonparabolicity corrections. Due to the strong overlap of the wavefunctions of the ground and the continuum localized states, the oscillator strengthis almost two orders of magnitude larger than the others. Two single QWstructures designed to have absorption of photons with the same energy, onebased on a bound-to-bound transition and the other on a bound-to-continuum,

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were also grown as reference samples. Comparing their device characteristics tothose of the proposed structure, the improvements in the photocurrent peakFWHM and carrier transport are highlighted. In summary, the photonic crystaltype QWIP structure is ideal to simultaneously achieve large absorption oscillatorstrength, sharp photocurrent peaks, efficient electron transport and freedom indesigning devices for infrared photodetection in the 2 to 5 µm range. References[1] B. F. Levine, "Quantum well infrared photodetectors" - J. Appl. Phys. 74, R1 (1993). [2] H. Schneider and H. C.Liu, "Quantum Well Infrared Photodetectors Physics and Applications", Springer, (2007). [3] C. Sirtori, F. Capasso, J.Faist, D. L. Sivco, S. G. Chu, and A.Y. Cho, "Quantum wells with localized states at energies above the barrierheight: A Fabry–Perot electron filter", Appl. Phys. Lett. 61, 898 (1992). [4] R. P. Leavitt and J. W. Little, "Infraredphotodetector based on intersubband transitions to minigap-confined states in doped quantum wells" , Appl. Phys.Lett. 79, 2091 (2001).

Figure 1:(a)Conduction band structure of the sample showing two confined states on the continuum. (b)A hightransmission is observed on the confined states (c)The oscillator strength of the confined state is almosttwo orders of magnitude larger than the others.

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ThP2-21 | Time-dependent calculation of the transportproperties of semiconductor porous layers (#503)Jeanlex S. de Sousa , Francisco W. N. Silva, Ascânio D. Araújo, Gil de AquinoFariasUniversidade Federal do Ceará Departamento de Física, Fortaleza, Brazil ContentThe demonstration of light emission in porous silicon (PS) in early 90’s triggeredstrong efforts to understand how light could be emitted from indirect gapcrystalline materials [1]. It is currently accepted that those porous structure canbe considered as a disordered network of nanostructures in which radiativerecombination due to (i) quantum confinement and (ii) surface defects are themain light emission mechanisms. Numerous reports show that PS electronicproperties significantly depend on few parameters during PS formation: etchingrate, anodization current density and composition of the electrolyte [2-4]. Inessence, those parameters determine the micro-morphology of the porousstructure, e. g. size distribution and the spatial arrangement of the linkednanostructures network that composes the porous structure. Despite of theknowledge about PS that has been accumulated so far the effect of themicroscopic structure on the charge mobility and resistance is not wellunderstood yet. We revisit the problem of electrical transport across asemiconductor porous layer by means of a time-dependent theoretical frameworkbased in the Schrodinger equation. Our simulation method is inspired inphotocurrent time-of-flight (TOF) experiments [5], which is commonly employedto characterize the transport properties of disordered systems. In our simulation,the time T for a single electron pulse (accelerated by a external voltage V) tocross the porous region is recorded, and the current, calculated as i=q/T, isaveraged over a number of randomly generated porous structures. Thetransmission coefficient and charge mobility are also calculated as a function ofthe system porosity. Our results show that those systems exhibit interestingdynamical effects and that the current-voltage characteristics strongly depend onthe porosity and pore sizes. We will also discuss the similarities between ourmodel system and the electrical properties of real porous structures. References[1] L. T. Canham, Appl. Phys. Lett. 57, 1046 (1990). [2] Z. Gaburro et al., J. Appl. Phys. 84, 6345 (1998). [3] G. Algünet al., Tr. J. of Phys. 23, 789 (1999). [4] P. Bettotti et al., J. Phys.: Condens. Matter 14, 8253 (2002). [5] E. A.Lebedev et al., Phys. Rev. B 57, 14607 (1998).

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Figure 1:Time evolution of an electronic pulse (V = 0.5 V) crossing a porous region with porosity of 90%.

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ThP2-22 | Improved noise properties of unipolar nanodiodes atelevated temperatures (#551)Shahrir R. Kasjoo , Linqing Zhang, Yasaman Alimi, Arun K. Singh, ClaudioBalocco, Aimin SongUniversity of Manchester School of Electrical & Electronic Engineering,Manchester, M13 9PL, Great Britain ContentTerahertz (THz) region is referred to the electromagnetic waves at frequenciesfrom 0.1 – 10 THz. In the last two decades, interest in THz emission anddetection has been growing steadily given its huge potential in manyapplications. Recently, self-switching diodes (SSDs)1 have shown properties notonly proven as room temperature detectors at microwave2 and THz3,4 frequenciesbut also potentially as THz emitters.5 By breaking the symmetry of asemiconductor nanochannel, the SSD provides a strong nonlinear current-voltage (I-V) characteristic similar to the behaviour of a conventional diode butwithout the use of any doping junction or barrier structure (see Fig. 1). Thedevice is defined by a single high-resolution lithography step, thus making thewhole fabrication process simpler, faster and at low cost. Its planar architecturenot only enables operation at ultrahigh speed up to 1.5 THz due to theintrinsically low parasitic capacitance, but also allows the formation of manyparallel-connected devices in a single fabrication step without the need ofinterconnection layers between them. In this report, we study the noiseperformance of a large SSD array at elevated temperatures, T, after our recentwork which demonstrated comparable noise-equivalent-power of SSDs to thosereported for the state-of-the-art Schottky diodes at room temperature.6 The arraywas fabricated on an InGaAs/InAlAs quantum-well wafer grown onto an InPsubstrate, in which free carriers were confined in a quantum-well located 25 nmbelow the surface, forming a two-dimensional electron gas (2DEG) layer. Thecarrier density and the electron mobility at room temperature were 1.3 × 1012 cm-2

and 10,400 cm2/Vs respectively as determined by Hall measurement. Here, weobserve a drastic reduction of low-frequency (1/f) noise (by a factor of 10 at150 °C) and also even a slightly decreased thermal noise (see Fig. 2). Thefinding may be useful in practical applications in terms of improving the signal-to-noise ratio for THz detection. The data analysis suggests that the increasedthermionic emissions are responsible for the decreased device resistance andhence reduced thermal noise. The barrier height induced by the surface chargesaround the device channel is derived from the behaviour of its reverse-biassaturation current, I0, in the sub-threshold regime at different temperatures (seeFig. 3). The observed noise property seems to be in good agreement withHooge’s mobility fluctuation theory. References1A. M. Song et al, Appl. Phys. Lett. 83, 1881 (2003) 2Claudio Balocco et al, Nano Lett. 5, 1423 (2005) 3ClaudioBalocco et al, Appl. Phys. Lett. 98, 223501 (2011) 4J. Mateos et al, Appl. Phys. Lett. 86, 212103 (2005) 5K. Y. Xu, G.Wang, and A. M. Song, Appl. Phys. Lett. 93, 233506 (2008). 6Claudio Balocco et al, Appl. Phys. Lett. 99, 113511(2011)

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Fig. 2:Fig. 2 Voltage noise spectra of SSD array as a function of frequency, f, at different temperatures and V =1.2 mV. The observed flicker (1/f) noise in the device was reduced as T increased and so did its thermalnoise as shown in the inset.

Fig.1:Fig. 1 (a) Atomic-force microscope (AFM) image of a single SSD where V is the applied voltage to theright hand side of the device. (b) Current-voltage (I-V) characteristic of SSD array resembles the nonlinearbehaviour of a conventional diode.

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ThP2-23 | Overshoot Mechanism of Transient Excitation of THzand Gunn Oscillations in Wide Bandgap Semiconductors (#553)Ernesto Momox , Nick Zakhleniuk, Naci Balkan, Muhammet OkurUniversity of Essex School of Computer Science and Electronic Engineering,Wivenhoe Park, Colchester, CO4 3SQ, Great Britain ContentUntil recently the maximum emission frequency in III-V emitters was limited to ~100 GHz, e.g. in Gunn diodes. The latter devices work at a fixed dc bias. In thelast few years the attention turned to transient regimes [1] where a short (< 1 ps)high-electric field pulse is incident on a sample using e.g. a photoconductiveswitch. It is usually assumed [1] that the electron gas remains spatiallyhomogeneous and there is no space-charge injection. In addition, the electrondistribution is a shifted Maxwellian function which is impossible to realise in bulkmaterials. In this paper we investigate a non-linear transient response of highly-doped samples to the three types of the incident electric fields: (a) short (~ 1 ps)pulse; (b) step-function with a very steep (~0.1 ps) rise time; (c) dc regime. Thetransient transport model is developed using powerful software tool SentaurusDevice [2]. Both the drift-diffusion (DD) and the hot-electron hydrodynamic (HD)models are investigated. We utilise various VF characteristics [2] including theCanali model and the transferred electrons (TE) model. The main our result isthat the transport is strongly influenced by the injected space charge. Thetransient response is completely different than it was observed in [1]. The space-charge accumulation layer is generated at the cathode and propagates to theanode during the incident pulse (no domain formation was observed). Allinvestigated models show sharp (~ 0.2 ps) response pulses, as is shown in Fig. 1for GaN sample. The strongest response is observed when the transport obeysthe HD model with the TE velocity. In this case the electrons are injected at theovershoot velocity. The overshoot injection also takes place for Canali model.The generated THz pulses are observed for all transport models. This indicatesthat our result is physically sound and should be observed experimentally. Thesteady-state I-Vs are shown in Fig. 2. Although in practice these I-Vs cannot beobserved due to instability, it is interesting to see that the HD model with the TEvelocity does not produce the non-monotonous I-V because of the space chargeinjection. In case of the step incident field we found that the system exhibits avery sharp subpicosecond overshoot current pulses which are repeated at aGunn oscillation frequency (~ 100 GHz). The frequency spectrum of these pulsesis ~ 10 THz. We present spatio-temporal analysis of all the above effects forvarious materials. References[1] V. V. Korotyeyev, V. A. Kochelap and K. W. Kim Semicond. Sci. Technol. 26 (2011) 105008 [2]http://www.synopsys.com/tools/tcad/devicesimulation/pages/sentaurusdevice.aspx

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Figure 1:Transient conduction current response of 2 um bulk GaN sample to a 1 ps incident bias for varioustransport models. The current is normalized to a 1 um thick sample.

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Figure 2:Steady state current voltage characteristics of the same sample as in Fig. 1.

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ThP3-1 | Theory of spin transport in Ferromagnetic metal withnonuniform spin-orbit interaction (#134)Kazuhiro Hosono 1, Kazuhiro Tsutsui2, Takehito Yokoyama2, Yukio Nozaki1,3

1Keio University Physics, 3-14-1,Kouhoku-ku, Hiyoshi, Kanagawa, Yokohama223-8522, Japan 2Tokyo Institute of Tchnology Pysics, 2-12-1 Ookayama, Meguro-ku, Tokyo152-8551, Japan 3JST, CREST, 5, Sanbuncho, Chiyoda-ku, Tokyo 102-0075, Japan ContentThe basic for electronic devices aiming at manipulating the spin degree forfreedom is spintronics, which provides a possible means to realize advantageousfunctionalities for spin based recording and information processing. For suchfunctions, the usage of spin current, a flow of spin angular momentum, isindispensable. Thus establishing techniques and theoretical interpretation ofgeneration and manipulation of spin currents is a key for further advancement ofspintronic devices. Recent experiments suggested that the spin current inferromagnet were absorbed by a nonmagnetic metal with strong spin-orbitinteraction [1]. The theoretical interpretation of the spin-current absorption or spinsink effect has so far been considered on phenomenological grounds [2]. Wemicroscopically derive the theoretical expression of the spin current inferromagnetic materials with inhomogeneous spin-orbit interaction, by developinglinear response theories on uniform spin-orbit interaction [3]. Based on ourresults, we found that a spin current is generated by the gradient of the spin-orbitinteraction in external electric field. We discuss the relevant experimental set upto observe this spin current generation and the correlation between the spincurrent generation and the spin sink effect. References[1]S. O. Valenzuela and M. Tinkham, Nature 442, 176 (2006). T. Kimura, Y. Otani, and J. Hamrle, Phys. Rev. B 73,132405 (2006).;T. Kimura, Y. Otani, T. Sato, S. Takahashi, and S.Maekawa, Phys. Rev. Lett. 98, 156601 (2007).;T.Seki, Y. Hasegawa, S. Mitani, S. Takahashi, H. Imamura, S. Maekawa, J. Nitta, and K. Takanashi, Nature materials7, 125 (2008). [2]P. Van Son, H. Van Kempen, and P. Wyder, Physical Review Letters 58, 2271 (1987).; S.Takahashi and S. Maekawa, Phys. Rev. B 67,052409 (2003).;T. Valet and A. Fert, Physical Review B 48, 7099(1993) [3]K. Hosono, A. Yamaguchi, Y. Nozaki, and G. Tatara, Phys. Rev. B 83, 144428 (2011).;J. Shibata,and H.Kohno, Phys. Rev. B 84, 184408 (2011).

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ThP3-2 | Spin polariton population transfer effect (#165)Victor S. Comitti , Marina B E. da Silva, Franklin M. MatinagaUniversidade Federal de Minas Gerais Depto. de Física, AV ANTONIO CARLOS6627 PAMPULHA, BELO HORIZONTE, MG, 30123-970, Brazil ContentStudy of polariton spin emission from a microcavity has been shown by manygroups[1,2,3]. The usual lower polariton branch (LP) split in to the s+, s- states(right, left circular polarization light) as shown by polariton beating dynamicsobservations[1], or in the Faraday polarization rotation effect[2]. We have studiedthe polariton spin splitting behaviour in relation to the excitation polarizationdegree r=( Is+ - Is- )/( Is+ + Is-) by using a pulsed laser (~100 fs) excitation andmeasuring the polariton emission slightly above the condensed state (k>0), i.e.the polariton emission light was blue shifted in relation to the bottom line. Weobserved a population exchange from Is+ to Is- (intensity from polariton with spinup and down) in the emission when the pump polarization degree r were tunedfrom +1 to -1, also when the pump power was increased. These measurementsshow a polariton population exchange and density inversion between thesestates. We used a GaAs SQW microcavity and the polariton emission behaviorwas reported previously[4]. The sample was cooled to 10 K and the experimentalset-up was mounted as the usual photoluminescence (PL) system using aTi:Sapphire pulsed laser. The excitation beam was focused in to the magic angleq=12 degree in relation to the cavity normal direction. The LP emission wascollected from the sample normal direction, i.e. for k=0. We used a l/4 plate inthe pump laser path to tune the polarization degree from +45° to -45°. The usualphotoluminescence (PL) spectrum shows us mainly a sharp strong peak from thecondensed states, however, we can select the PL for k>0, where we can observetwo peaks separated by 0.19 meV, coming from Is+and Is- as illustrated on figure1. We measure the emission spectrum behavior for each laser polarizationdegree r (from +1 to -1) as shown on intensity peaks ratio (Is+/ Is-) in figure 2, alsothe same intensity relation by increasing the pump power at constant r wasmeasured. Those measurements show a population transfer from s+ to s- whenthe polarization degree were tuned from +1 to -1. We have not observed majorchange in the splitting energy when the cavity resonance was detuned in thosemeasurements. In summary, we have addressed spin polariton populationtransfer measurements between s+ and s- states. All these states energy wereabove the BEC state of the cavity. The authors acknowledge the financialsupport from FAPEMIG, CNPq and DISSE (MCT). ReferencesReferences [1] K.V. Kavokin et.al., Phys. Rev. Lett. 92, (2004), pp. 017401. [2] D. Scalbert, et. al., Superlattices andMicrostructures, 43 (2008), pp. 417-428. [3] Kasprzak, J. et. al., Nature 443, (2006) pp. 409-414 ; A. Amo et. al.,Nature Photonics 4, (2010), pp. 361 - 366. [4] L.M. Moreira, E.A. Cotta, J.C. González, F. M. Matinaga, M. V. B.Moreira, and A. G. de Oliveira, Solid State Communication, 143, (2007), pp. 166-170.

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Figure 1:Polariton PL for 0 degree polarization excitation laser

Figure 2:Polaritons PL intensity ratio for 5meV detuning

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ThP3-3 | Synthesis, structural and magnetic characterization ofTi1-xCoxO2 diluted magnetic oxide (#234)Talita Evelyn Souza1, Patrícia Covre1, Alexandre Mesquita1, Person PereiraNeves1, Antonio Carlos Doriguetto Doriguetto1, Valmir Antonio Chitta2, Hugo Bonette de Carvalho1

1Universidade Federal de Alfenas Instituto de Ciências Exatas, Alfenas, MinasGerais, 37130000, Brazil 2Universidade de São Paulo Instituto de Física, PO Box 66318, São Paulo, SãoPaulo, 05315970, Brazil ContentTransition metal doped oxides are known as diluted magnetic oxides (DMOs).The incorporation of the magnetic ions on the oxide matrix has been extensivelystudied as an alternative to achieve a room temperature ferromagnetic behavior.This family of materials has been attracting to much attention due itspotential application in the development of spintronics devices [1, 2]. Thesematerials are also economic strategic due to its electro-electronics, optical andcatalytic properties. Transition metal doped TiO2 belong to this class of materialand, in spite of the huge effort both from the experimental and the theoreticalpoint of view, the understanding of its magnetic properties remains inconclusiveand controversial. In the present work we report the synthesis of nanostructuredCo-doped TiO2 prepared trough the method of the polymeric precursors (Pechini)with Co atomic concentrations of 3, 6, 9 and 12%. We have performed a carefulstructure characterization and determined its corelation to the magneticproperties. The microstructure were characterized by X-ray di®raction (XRD),transmission electron microscopy (TEM), Raman scattering spectroscopy and X-ray absorption spectroscopy (XAS) in the Co K-edge (XANES and EXAFS). Themagnetic characterization was performed using a superconducting quantuminterference device (SQUID) magnetometer. The authors are grateful toFAPEMIG, FAPESP and CNPq for financial support. References[1] T. Kasuya and A. Yanase; Rev. Mod. Phys. 40, 684 (1968). A. Mauger and C. Godart; Phys. Rep. 141, 51 (1986).[2] S. A. Wolf et al.; Science 294, 1488 (2001).

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ThP3-4 | Uniaxial magnetic anisotropy in1-dimensional Fenanostructures on Al2O3(0001) induced by oblique deposition(#252)Wen-Chin Lin 1, Chiao-Sung Chi1, Bo-Yao Wang2, Way-Faung Pong2, Tsung-Ying Ho1, Fang-Yuh Lo1, Cheng-Jui Tsai11National Taiwan Normal University Physics, Taipei 11677, Taiwan 2Tamkang University Department of Physics, Taipei Taiwan ContentIn ferromagnetic (FM) materials, the magnetic anisotropy energy (MAE) not onlydetermines the easy magnetization direction, but is also correlated to themagnetization processes of FM materials. Based on the knowledge of thephysical origins of MAE, the manipulation of MAE has been demonstrated to befeasible, especially in nano-sized materials, for applications in magnetic datastorages and nano-devices. One of the practical methods is tuning MAE by theshape of the magnetic materials, i.e. shape magnetic anisotropy. Self-organizedapproaches have been realized as promising ways for fabrication of nano-structured thin lms, as well as the control of shape MAE. Due to the shadowingand steering e ects, oblique deposition of magnetic atoms on suitable substratescan lead to highly elongated grains or ripples of nanometer scale width. Theseelongated nanograins or ripples were shown to induce a uniaxial MAE. Thismethod of manipulating MAE is easy to apply to magnetic nano-devices. In thisstudy, self-organized 1-dimensional magnetic structures of Fe on Al2O3(0001)were prepared by oblique deposition. The surface morphology, crystallinestructure, and magnetic behavior were studied. The X-ray diffraction (XRD)characterization shows the preferred (110) texture of the Fe lms. Both the XRDand extended X-ray adsorption fine structure (EXAFS) measurements indicatethe larger oblique deposition angle (65 deg.) leads to more disorder in the Fecrystalline structure. After capping of the Pd overlayer, the Pd/Fe/Al2O3(0001) stillreveals the uniaxial magnetic anisotropy induced by the buried 1-dimensional Fenanostructures. This uniaxial magnetic anisotropy changes with the variation inFe thickness and oblique deposition angle. The higher oblique deposition angleresults in a larger coercivity, a larger uniaxial MAE, as well as more obviousdisordering in the crystalline structure. These results clearly indicate thepracticability of manipulating a uniaxial magnetic anisotropy, as well as crystallineorder by oblique deposition of magnetic materials. Besides, the hydrogenadsorption in Pd capping layer changes the Kerr signal of the Pd/Fe bilayers.This hydrogen adsorption effect on magneto optical property is shown to bereversible and can be applied in nanotechnology.

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Figure 1:STM images of Pd/0, 45 and 65 degree-deposited Fe films on Al2O3(0001).

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Figure 2:MOKE hysteresis loops of Pd/25 ML 0, 45, 65 degree-deposited Fe/Al2O3(0001), measured with thevariation in azimuthal angle in a step of 10 degree.

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ThP3-5 | Spin polarization in double barrier diodesincorporating InAs self-assembled quantum dots (#292)J. A. Nóbrega1, V. O. Gordo 1, H. V. A. Galeti1, Marcio Teodoro1, Y. GalvãoGobato1, Gilmar E. Marques1, Milan Orlita2,3, D. K. Maude2, Mohamed Henini4, D.Taylor4

1Federal University of São Carlos Physics Department, São Carlos, Brazil 2Grenoble High Magnetic Field Laboratory, Grenoble, France 3Charles University Institute of Physics, 121 16 Praha 2, Ke Karlovu 5, CzechRepublic 4University of Nottingham School of Physics and Astronomy, NottinghamNanotechnology and Nanoscience Center, Nottingham NG72RD, Great Britain ContentWe have investigated the spin polarization of carriers in n-type resonanttunnelling diodes which incorporates a layer of InAs self-assembled quantumdots (QDs) in the center of a GaAs quantum well (QW) grown on a (311)B-oriented GaAs substrate. The spin-dependent carrier transport along thestructure was investigated by measuring the left- and right-circularly polarizedphotoluminescence (PL) intensities from InAs dots and GaAs contact layers as afunction of the applied voltage, laser intensity and magnetic fields up to 20 T. Thecurrent voltage characteristics curve (I(V)) presents one resonant peak due to theresonant tunnelling of electrons through the confined level in the QW. The PLintensity from QDs for both circular polarizations presents a clear correlation withthe I(V) characteristic curve. The QD circular polarization degree depends onboth the applied bias and the light intensity and presents a maximum value nearthe resonant tunnelling condition of photo-generated holes. On the other hand,the spin-splitting of the QD PL emission is negligible and does not show anyappreciable variation with the applied voltage and light intensity. Therefore thespin splitting does not explain the voltage dependence of the QD polarizationdegree. Finally, our experimental results are discussed in terms of the tunnellingof minority carriers into the QW, carrier capture into the InAs QDs, partialthermalization of minority carriers and bias-controlled density of carriersaccumulated in the QW region.

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ThP3-6 | Spin Hall effect in a semiconductor waveguide (#309)Jose Luis Cardoso Universidad Autónoma Metropolitana - Azcapotzalco Departamento de CienciasBásicas, Av. San Pablo Xalpa 180 Col. Reynosa-Tamaulipas, 02100 MexicoCity, Mexico ContentIn this work, we use the analytical solution Pauli equation in the effective massapproximation, with Rashba and linear Dresselhaus interactions, for a two-dimensional electron gas moving through a semiconductor waveguide under alongitudinal electric field. We study the relative influence of Rashba andDresselhaus terms on the spin-Hall effect, and the spin-channels mixing. Weshow that for unpolarized electrons, the spin-Hall effect is only due to theDresselhaus term. In a 2DEG an high magnetic fields, the integer Quantum Halleffect and the Hall resistance quantization[1] lead to transversal modes and edgestates. In this case, each edge state is spin-degenerate because the Zeemansplitting is negligible[2]. There has been theoretical predictions that a differentkind of edge channels can form even in absence of an external magnetic field[3],this anomalous behavior is called Spin Hall Effect (SHE). In this work we studyspin electrons dynamic. We neglected the cubic Dresselhaus spin-orbit term andwe propose an alternative form of the linear Dresselhaus interaction. Here, weshall work with regions where there is no applied magnetic field. We found spinaccumulations near the semiconductor waveguide edges: spins of onepolarization pile up at one edge, while spins of the opposite polarization pile up atthe other edge. In other words, it is possible to see the edge states and,therefore, SHE. In figure, the transversal spin amplitudes |Fr,↑|2, |Fr,↓|2 and ∆|Fr|2= |Fr,↑|2-|Fr,↓|2 as functions of the y-direction when here is only Dresselhausinteractions for spin unpolarized electrons at the z-direction: a) for the firstFourier open channel r = 1; and b) the second open channel r = 2. The symmetryof |Fr,↑|2 and |Fr,↓|2 are broken by the Dresselhaus term. The spin-up electrons pileup at the left edge because ∆|Fr|2> 0, while ∆|Fr|2< 0 indicating that the spin-downelectrons pile up at the right edge. In figure, the transversal spin amplitudes |Fr,↑|2,|Fr,↓|2 and ∆|Fr|2= |Fr,↑|2-|Fr,↓|2 as functions of the y-direction when here is onlyDresselhaus interactions for spin unpolarized electrons at the z-direction: a) forthe first Fourier open channel r = 1; and b) the second open channel r = 2. Thesymmetry of |Fr,↑|2 and |Fr,↓|2 are broken by the Dresselhaus term. The spin-upelectrons pile up at the left edge because ∆|Fr|2> 0, while ∆|Fr|2< 0 indicating thatthe spin-down electrons pile up at the right edge. References[1] K. V. Klitzing, G. Dorda, and M. Pepper, Phys. Rev. Lett. 45, 494 (1980). [2] A. Kunold and M. Torres, Annals ofPhysics 315, 532 (2005). [3] J. E. Hirsch, Phys. Rev. Lett. 83, 1834 (1999); S. Zhang, Phys. Rev. Lett. 85, 393(2000); S.-Q. Shen, Phys. Rev. B 70, 081311(R) (2004); S. Murakami, N. Nagaosa, and S.-C. Zhang, Phys. Rev.Lett.93, 156804 (2004); B. A. Bernevig, T. L. Hughes, and S.-C. Zhang, Science 314, 1757 (2006).

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Figure 1:spin amplitudes |Fr,↑|2, |Fr,↓|2 and ∆|Fr|2= |Fr,↑|2-|Fr,↓|2 as functions of the y-direction. The symmetry of |Fr,↑|2 and |Fr,↓|2 are broken by the Dresselhaus term.

315

ThP3-7 | Spin polarization of carriers in Si delta-dopedstructures (#314)L. K. S. Herval1, V. O. Gordo1, H. V. A. Galeti1, Y. Galvão Gobato 1, Gilmar E.Marques1, D. Taylor2, Mohamed Henini21Federal University of São Carlos Physics Departament, São Carlos, Brazil 2University of Nottingham School of Physics and Astronomy, NottinghamNanotechnology and Nanoscience Center, Nottingham, Great Britain ContentWe have studied GaAs/AlGaAs resonant tunneling diodes with a Si delta-dopedlayer placed at the center of the quantum well (QW). The presence of donorimpurities in the GaAs QW, which gives rise to localized states below the edge ofthe first subband in the QW, can add new features in the current-voltage, I(V),characteristics. These features are associated to donor assisted tunneling whichis obtained by the alignment of occupied states in the emitter and donor states inthe QW. In this work, we have investigated the magneto-transport and polarizedresolved photoluminescence (PL) from GaAs QW and contact layers as afunction of applied voltage and magnetic field parallel to the tunnel current. Tworesonant peaks are observed in the I(V) characteristics. The lower and highervoltage peaks are associated to the donor-assisted resonant tunneling (D) and tothe electron resonant tunneling through the first confined state in the QW (e),respectively. The QW PL intensity (Figure 1) shows a good correlation with theI(V) characteristics for both polarizations. The circular polarization degree (Figure2) in the QW is light and voltage dependent. High values of QW polarizationdegree (up to 85% at 15T) are obtained at low applied voltages (donor assistedresonant tunneling condition) and for low laser intensities. The optical emissionfrom GaAs contact layers shows evidence of highly spin polarized two-dimensional electron (2DEG) and hole (2DHG) gases, which affect the spinpolarization of carriers in the QW. These results may be interesting for thedevelopment of voltage- controlled spintronics devices.

Figure 1:Color-coded maps of polarization resolved PL intensities as a function of voltage for QW under B=15T

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Figure 2:Bias voltage dependence of QW polarization degree from QW, GaAs contact and 2DEG-h emissions at 15T.

317

ThP3-8 | Non linear transport model for the giant spin-dependent photo-conductivity in GaAsN dilute nitridesemiconductors (#318)Alejandro Kunold 1, Pedro Eduardo Roman-Taboada1, Juan Carlos Sandoval-Santana2, Andrea Balocchi3, Helene Carrere3, Thierry Amand3, Naoufel BenAbdallah4, Jean-Christophe Harmand5, Xavier Marie3

1UAM-A Ciencias Basicas, Av. San Pablo, 02200 Mexico, Mexico2Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal20-3641, 01000 Mexico, Mexico3INSA-Toulouse LPCNO, 135 avenue de Rangueil, 31077 TOULOUSE, France 4Universite de Toulouse; UPS-CNRS-INSA IMT, 118, Route de Narbonne,F-3106 TOULOUSE, France 5LPN-CNRS Site Alcatel de Marcoussis, Route de Nozay, 91460 MARCOUSSIS,France ContentWe present a theoretical study of the spin-dependent photoconductivity in adilute Nitride GaAsN heterostructures [1]. In this materials the strong localizationof the electron's wave function in the deep paramagnetic centers harnesses thespin dependent recombination processes[2,3]. We develop a non linear transportmodel based on the rate equations for electrons, holes, deep paramagnetic andnon paramagnetic centers under CW optical excitation. Particular attention ispaid to the role drift and diffusion of charge carriers. Under an external magneticfield in Voigt geometry the photoconductivity exhibits a Hanle-type curve whereasthe spin polarization of electrons shows two superimposed Lorentzian curveswith different widths, respectively related to the recombination of free andtrapped electrons[4]. The model is capable of reproducing the most importantfeatures of photoluminescence and photocurrent experiments and is helpful inproviding insight on the various mechanisms involved in the electron spinpolarization and filtering in GaAsN semiconductors. References[1] A. Kunold, A. Balocchi, T. Amand, N. Ben Abdallah, J. C. Harmand and X. Marie,Phys. Rev. B 83, 165202 (2011).[2] V. Kalevich, E. Ivchenko, M. Afanasiev, A. Shiryaev, A. Egorov, V. Ustinov, B. Pal, and Y. Masumoto, JETP Lett.82, 455 (2005). [3] F. Zhao, A. Balocchi, A. Kunold, J. Carrey, H. Carrere, T. Amand, N. Ben Abdallah, J. C.Harmand, and X. Marie, Appl. Phys. Lett. 95, 241104 (2009). [4] V. Kalevich, A. Shiryaev, E. Ivchenko, M. Afanasiev,A. Egorov, V. Ustinov, and Y. Masumoto, Physica B 404, 4929 (2009).

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ThP3-9 | Polarization-resolved magneto-photoluminescence ofInGaAs(N)/GaAs quantum wells (#322)L. K. S. Herval1, V. O. Gordo1, Vivaldo Lopes-Oliveira1, A. Khatab2, M. P. F. de Godoy1, Y. Galvão Gobato1, Gilmar E. Marques1, M. J. S. P. Brasil3, MohamedHenini2, M. Sadeghi4, S. Wang4

1UFSCar Departamento de Física, Rodovia Washington Luiz, km 235, CaixaPostal 676, São Carlos, SP, 13565-905, Brazil 2University of Nottingham School of Physics and Astronomy, NottinghamNanotechnology and Nanoscience Center, Nottingham, NG72RD, Great Britain3UNICAMP Instituto de Física "Gleb Wataghin", Campinas, SP, 13083-859,Brazil 4Chalmers University of Technology Photonics Laboratory, Departament ofMicro-technology and Nanoscience, 41296 Goteborg, Sweden ContentInGaAsN/GaAs heterostructures have attracted much attention in the last years. Small fractions of substitutional nitrogen in III-V semiconductors changedrastically the optical and electronic properties of such materials. The maineffects of N-content in InGaAsN alloys are a strong bandgap reduction, which isattractive for 1.30-1.55 µm optoelectronic devices, and an increase of the carrier-localization phenomenon. Moreover, spin properties in dilute nitridesemiconductors have only recently been investigated. The reported results showa correlation between the N-content and an increase of spin lifetime in GaAsNepilayers. In the present work, we have investigated the polarized-resolvedphotoluminescence in InxGa1-x As1-yN y / GaAs quantum wells (QWs) under high-magnetic fields parallel to the growth axis, including a control sample without N(y=0). The samples consist of two QWs of 4 and 7 nm with x=36% and y=1.2%.All samples were grown by molecular beam epitaxy on (100) GaAs substrates.Magneto-photoluminescence measurements were performed as a function oftemperature and magnetic fields up to 15T. We have observed that for lowtemperatures, the degree of polarization for N-free and N-containing QWs arequite similar, but the observed spin-splitting is twice larger for InGaAsN QWs.Furthermore, we have observed that the diamagnetic shift was reduced for N-containing samples. This effect is attributed to localized excitons in thistemperature range. The main differences between N-free and N–containingsamples appear as the temperature is increased. The polarization degree for N-free QWs decreases monotonically as a function of temperature, as expected.However, for N-containing samples the polarization remains relatively large up to140 K. Our results are interpreted in terms of localized and free excitons, andstrain effects.

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ThP3-10 | Localization effects in InGaAsN/GaAsN /GaAsquantum wells grown on (100) and (311)A GaAs substrates(#326)V. O. Gordo1, L. K. S. Herval1, A. Khatab2, M. P. F. de Godoy 1, Y. GalvãoGobato1, M. J. S. P. Brasil3, Gilmar E. Marques1, Mohamed Henini21UFSCar Departamento de Física, Rodovia Washington Luiz, km 235, CaixaPostal 676, São Carlos, SP, 13565-905, Brazil 2University of Nottingham School of Physics and Astronomy, NottinghamNanotechnology and Nanoscience Center, Nottingham, NG72RD, Great Britain3UNICAMP Instituto de Física "Gleb Wataghin", Campinas, SP, 13083-859,Brazil ContentRecently dilute nitride III-V semiconductors have attracted much attention due topotential applications in optoelectronic devices in the infra-red range to accessthe transmission windows from optical fibers. The incorporation of N in smallfractions into (InGa)As heterostructures reduces drastically the bandgap andperturbes the conduction band. It is also responsible for carrier localizationobserved in photoluminescence (PL) at low temperatures. Additionally, recentstudies on GaAsN layers have shown long spin lifetimes at room temperaturewhich is the key for new spintronic devices. These samples are traditionallygrown on (100) substrates. Growth of dilute nitrides heterostructures on non-(100) substrates can be attractive due to the possibility of achieving highercritical-layer thickness and longer emission wavelength tuning. In this work, wehave investigated InGaAsN/GaAsN/GaAs quantum wells grown by molecularbeam epitaxy on (100) and (311)A GaAs substrates. We have measuredpolarized-resolved photoluminescence under magnetic fields up to 15 T. TwoQW emission bands are clearly observed: the lower-energy band is usuallyattributed to localized excitons (LE) and the higher-energy should be associatedto free excitons (FEs). As temperature increases the FE emission becomesrelatively stronger and the radiative recombination process is dominated by FEsfor temperatures larger than 140K for (100) QW and 50 K for (311)A QWs. Thecircular polarization degrees at low temperatures are similar for both sampleorientations. However, their temperature dependence is very distinct. Inparticular, the polarization degree for the (100) QW has significant values up to160K as compared to (311)A QW. In addition, no magnetic-shift was observedfor the LE transition, while the FE band exhibits small energy shifts, namely 1meV for (100) and 6 meV for (311)A directions. At high temperatures, severalanomalies in diamagnetic shift as a function of magnetic field are also observed.Our results indicate that InGaAsN/GaAsN/GaAs QWs grown on (311)A substrateorientation has minor localization effects as compared to those of (100) QW.

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ThP3-11 | Amplification of spin-dependent recombination ratioand spin polarization in GaAsN dilute nitride semiconductorheterostructures through an external magnetic field in Faradayconfiguration. (#343)Miguel Romero-Serrano1, Alejandro Kunold 2, Andrea Balocchi3, HeleneCarrere3, Thierry Amand3, Naoufel Ben Abdallah4, Jean-Christophe Harmand5,Xavier Marie3

1Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal20-3641, 01000 Mexico, Mexico2UAM-A Ciencias Basicas, Av. San Pablo, 02200 Mexico, Mexico3INSA-Toulouse LPCNO, 135 avenue de Rangueil, 31077 TOULOUSE, France 4Universite de Toulouse; UPS-CNRS-INSA IMT, 118, Route de Narbonne,F-3106 TOULOUSE, France 5LPN-CNRS Site Alcatel de Marcoussis, Route de Nozay, 91460 MARCOUSSIS,France ContentRecent experiments show that the intensity and circular polarization degree ofthe photoluminescence in GaAsN dilute nitride semiconductor heterostructuresexcited by circularly polarized light increase substantially under an appliedmagnetic field in Faraday configuration [1]. It has been suggested that thisbehavior is related to the coupling of nuclei with deep paramagnetic centresthrough the hyperfine interaction. In order to explain these experimental resultswe have developed a model based on the Von Neumann equation with a nonlinear Lindbladian. The Hamiltonian contains the hyperfine interaction betweendeep paramagnetic centres and nuclei and the Zeeman terms that coupleconduction band electrons and trapped electrons spins to an external magneticfield . The spin-dependent recombination processes are introduced through thenon linear Lindbladian. We show that the proposed model yields the correctbalance equations for the spin polarization and charge carrier density [2-4]together with additional terms that account for the hypefine interaction. Themodel described here is capable of reproducing the most important features ofthis phenomenon. References[1] V. K. Kalevich, M. M. Afanasiev, A. Yu. Shiryaev, and A. Yu. Egorov, 107.22 arXiv:1107.2250v150v1 [2] V.Kalevich, E. Ivchenko, M. Afanasiev, A. Shiryaev, A. Egorov, V. Ustinov, B. Pal, and Y. Masumoto, JETP Lett. 82,455 (2005). [3] F. Zhao, A. Balocchi, A. Kunold, J. Carrey, H. Carrere, T. Amand, N. Ben Abdallah, J. C. Harmand,and X. Marie, Appl. Phys. Lett. 95, 241104 (2009). [4] V. Kalevich, A. Shiryaev, E. Ivchenko, M. Afanasiev, A. Egorov,V. Ustinov, and Y. Masumoto, Physica B 404, 4929 (2009).

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ThP3-12 | Engineering a spin-fet: spin-orbit phenomena andspin transport induced by a gate electric field (#344)Hugo Hernández-Saldaña , Jose Luis CardosoUniversidad Autónoma Metropolitana - Azcapotzalco Departamento de CienciasBásicas, Av. San Pablo Xalpa 180 Col. Reynosa-Tamaulipas, 02100 MexicoCity, Mexico ContentIn this work, we show that a gate electric field, applied in the base of the field-effect devices, leads to inducing spin-orbit interactions (Rashba and linearDresselhauss) and confines the transport electrons in a two-dimensional electrongas. On the basis of this phenomena and solving analytically the Pauli equation,we study the spin transport. The main consequences of the nanometer scale,with defined boundary conditions, is the confinement of the electric carriers inone-dimensional potential wells and the formation of the discrete energy spectra.For example, when an homogeneous magnetic field is applied in ananostructure, the energy levels are defined by the well-known Landau levelsand the associated spectrum can be manipulated by this magnetic field. For agate electric field, there are many ways to study this influence in the 2DEGspectrum. We shall study how the gate electric field works on the base. Itquantize, with appropiate boundary conditions, the transverse energy of theelectron creating the 2DEG and, hence, provokes the spin-orbit interactions. Themanipulation of spin by electric fields in semiconducting environments hasgenerated a lot of theoretical and experimental research aimed at developinguseful spintronic devices and novel physical concepts. The spin transistorelucidated by Datta an Das[1] is made to drive a modulated spin-polarizedcurrent. For this, the spin precession is controlled via the Rashba spin-orbitcoupling associated with the interfacial electric fields present in the quantum wellthat contains the two-dimensional electron gas. Externally applied electric fieldmay also induce spin-orbit interactions[2-4]. This work shows how the gateelectric field can manipulate the Rashba and linear Dresselhaus strength and theinterplay between them. The dynamics of the 2DEG with both spin-orbitinteractions is described by the Pauli equation. We solve analytically thisequation and study the spin transport for the 2DEG. References[1] Datta S. and Das B., Appl. Phys. Lett, 56 (1990) 665. [2] De Sousa R. and Sarma D., Phys. Rev. B, 68 (2004)155330. [3] Prabhakar S. and Raynolds J. E., Phys. Rev. B, 79 (2009) 195307. [4] Prabhakar S., Raynolds J. E.,Inomata A. and Melnik R., Phys. Rev. B , 82 (2010) 195306.

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ThP3-13 | Modulation of Spin-transport in a MagneticSuperlattice for Spin Filter Application (#356)Nammee Kim , Heesang Kim, Jinwoo KimSoongsil University Physics, Sang-do-dong, Seoul 156-743, Korea Republic(South) ContentWe study the spin miniband structure and the ballistic spin-polarized transport ofa magnetic superlattice, formed by inhomogeneous magnetic field in asemiconductor nanowire. Based on the transfer matrix theory and Bloch'stheorem, we calculate the energy dispersion having spin-minibands and spin-minigaps due to Bloch periodicity and spin-dependent ballistic conductance forvarious geometrical and physical parameters. Results show that full spin-polarization in the ballistic conductance of the system occurs clearly for eachspin, and that the fully spin-polarized range for each spin can be enhanced by modulation of geometrical and physical parameters.

Figure 1:Schematic diagram of a magnetic superlattice constructed by superconducting gridded mask on the top ofa quantum wire

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ThP3-14 | Geometric effect on spin-pumping-induced inversespin Hall effect in permalloy/platinum films (#379)Hiroyasu Nakayama 1, Kazuya Ando1, Kazuya Harii1, Tatsuro Yoshino1, RyoTakahashi1, Yosuke Kajiwara1, Ken-Ichi Uchida1, Yasunori Fujikawa1, EijiSaitoh1,2

1Tohoku University Institute for Materials Research, Sendai 980-8577, Japan 2Japan Atomic Energy Agency Advanced Science Research Center, Tokai319-1195, Japan Content Generation and detection of a spin current, a flow of electron spins, insolid-state systems have attracted much attention in the field of spintronics [1, 2].One method for generating and detecting spin current is the combination of thespin pumping and the inverse spin Hall effect (ISHE) [3, 4]. The spin pumpingenables spin current generation from magnetization precession at aferromagnetic/paramagnetic interface; a precessing magnetization in theferromagnetic layer induces a pure spin current in the attached paramagneticlayer [5]. This spin current is converted into a charge current via the ISHE in theparamagnetic layer, which allows the electric detection of a spin current. Thecombination of the spin pumping and ISHE allows direct quantitativemeasurements of spin currents generated by the spin pumping. We havequantitatively investigated the geometry dependence on the ISHE induced by thespin pumping driven by FMR. We measured the FMR spectrum and the electricvoltage induced by the ISHE with changing the size and the thickness ofpermalloy (Ni81Fe19)/platinum (Pt) bilayer films. The intensity of generated chargecurrents due to the ISHE changes systematically with changing the filmgeometry, which is consistent with the prediction of the ISHE. The experimentalresults show clear difference between Ni81Fe19 and Pt thickenss dependence ofthe ISHE induced by the spin pumping due to the different mechanism. With aconstant Pt thickness, the intensity of the generated charge current is keptproportional to that of the injected spin current density, which decreases withincreased spin relaxation in the Ni81Fe19 layer due to interfacial effect, inverselyproportional to its film thickness. On the other hand, reflecting the spin diffusionmechanism in the Pt layer, the charge current decreases significantly with thedecrease of the Pt thickness while injected spin current density is almost keptconstant. Since the spin pumping and ISHE enable spin current injection anddetection in various systems, these results will provide a guideline for designing ahigh efficiency spin current generator and detector. References[1] Concepts in Spin Electronics, edited by S. Maekawa (Oxford University Press, Oxford, 2006). [2] I. Zutic, J.Fabian, and S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004). [3] E. Saitoh, M. Ueda, H. Miyajima, and G. Tatara,Appl. Phys. Lett. 88, 182509 (2006). [4] O. Mosendz, J. E. Parson, F. Y. Fradin, G. E. W. Bauer, S. D. Bader, and A.Hoffmann, Phys. Rev. Lett. 104, 046601 (2010). [5] Y. Tserkovnyak, A. Brataas, G. E. W. Bauer, and B. I. Halperin,Rev. Mod. Phys. 77, 1375 (2005).

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ThP3-15 | Magnetic Mn5Ge3 nanocrystals embedded incrystalline Ge: a magnet/semiconductor hybrid synthesized byion implantation (#398)Shengqiang Zhou 1, A. Shalimov1, Wenxu Zhang2, D. Buerger1, A. Muecklich1,Manfred Helm1, H. Schmidt1

1Helmholtz-Zentrum Dresden-Rossendorf Institute of Ion Beam Physics andMaterials Research, Dresden, Germany 2University of Electronic Science and Technology of China State Key Laboratoryof Electronic Thin Films and Integrated Devices, Chengdu China ContentDue to its compatibility to Si technology, Ge has attracted special attention as ahost semiconductor for diluted magnetic impurity atoms. However, due to the lowsolid solubility of transition metals in Ge intermetallic compounds (mainlyMn5Ge3) tend to form in the Ge host. Mn5Ge3 is a ferromagnet with a TC of 296 Kand a large spin polarization [1]. It was recently pointed out that the integration ofMn5Ge3 with the Ge matrix is indeed quite promising for spin injection in a silicon-compatible geometry [1]. Therefore, considerable work has been done tofabricate epitaxial Mn5Ge3 films as well as nanostructures. An ensemble ofnanomagnets exhibits rich magnetic properties with a large technological impact.Temperature dependent memory effects and slow magnetic relaxation have beenobserved in a Mn5Ge3/Ge hybrid system [2]. In this contribution, we report thepreparation of magnetic Mn5Ge3 nanocrystals embedded inside the Ge matrix byMn ions implantation at elevated temperature. By X-ray diffraction andtransmission electron microscopy, we observe crystalline Mn5Ge3 with variablesize depending on the Mn ion fluence. A large positive magnetoresistance hasbeen observed at low temperature. It can be explained by the conductivityinhomogeneity in the magnetic/semiconductor hybrid system. References1. S. Picozzi, A. Continenza, and A. J. Freeman, Phys. Rev. B 70, 235205 (2004). 2. S. Zhou, A. Shalimov, K.Potzger, N. M. Jeutter, C. Baehtz, M. Helm, J. Fassbender, and H. Schmidt, Appl. Phys. Lett. 95, 192505 (2009).

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ThP3-16 | Spin polarization of electrons in quantum wire (#453)Alexander Vasilchenko , Alexey BunyakinKuban State Technological University, Moskovskaya str.,2, 350072 Krasnodar,Russia ContentDensity functional theory has been used to study the electronic structure ofquantum wires at zero magnetic field. Particular attention has been given tosystems with low electron density. The nonlinear system of Kohn-Shamequations was solved numerically and the total energy of the electrons for spinfactor gs = 1 and gs = 2 were calculated. Results of calculations showed that statewith fully polarized electrons is energetically favorable at low electron densities.The critical electron density, below which all electrons are in spin-polarized statehas been found. Analytical estimation has been done for one-dimensional criticaldensity (in atomic units Nc = 0,3), which is in good agreement with calculations.

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ThP3-17 | Conductance oscillations in a (Ga,Mn)As pointcontact device (#459)Stefan Geißler , Alexei Iankilevitch, Martin Utz, Dieter Schuh, DominiqueBougeard, Dieter WeissInstitut für Experimentelle und Angewandte Physik Universität Regensburg,Universitätsstr. 31, 93053 Regensburg, Germany ContentWe fabricated a nanoscale point contact device out of a 15 nm thick layer of thediluted magnetic semiconductor (Ga,Mn)As using electron beam lithography anda trench isolation technique. The device consists of two 1 µm wide leadsconnected by a 20x20 nm² point contact. On top we patterned a 50 nm thickAl2O3 layer and a gate electrode. The (Ga,Mn)As material is highly p-doped witha Mn content of approximately 5% and a hole density of about 3*1020cm-3. As(Ga,Mn)As is known to be a strongly disordered semiconductor close to themetal-insulator transition, the point contact geometry enhances disorder inducedeffects. Our transport experiments were done at cryogenic temperatures in a twopoint measurement setup. We observed oscillations of the differentialconductance depending on the applied gate voltage as well as on the externalmagnetic field and the magnetization direction of the device. Comparing the pointcontact device with an unconstricted device it can be shown that the observedtransport properties are dominated by the point contact. Moreover the device canbe tuned from zero to finite conductance at zero bias by post processingannealing as well as by the device dimensions itself.

conductance oscialltion:differential conductance oscillations vs. bias and gate voltage

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point contact device:20x20 nm² point contact device in a two point measurement setup

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ThP3-18 | A Study on the Correlation Between Structural andMagnetic Properties of Co-doped Oxide Nanoparticles: ZnOand CeO2 (#218)Vinícius Dantas Araújo1, Maria Inês Basso Bernardi1, Waldir Avansi2, ValmirAntonio Chitta3, Fanny Béron4, Kleber Roberto Pirota4, Alexandre Mesquita5,Hugo Bonette de Carvalho 5

1Universidade de São Paulo Grupo Crescimento de Cristais e MateriaisCerâmicos, Instituto de Física de São Carlos, PO Box 369, São Carlos, SãoPaulo, 13560970, Brazil 2Universidade Estadual Paulista INCTMN, LIEC, Instituto de Química,Araraquara, São Paulo, 14800900, Brazil 3Universidade de São Paulo Instituto de Física, PO Box 66318, São Paulo, SãoPaulo, 05315970, Brazil 4Universidade Estadual de Campinas Instituto de Fisica Gleb Wataghin,Campinas, São Paulo, 13083970, Brazil 5Universidade Federal de Alfenas Instituto de Ciências Exatas, Alfenas, MinasGerais, 37130000, Brazil ContentThe interest in transition metal doped oxides has been attracted much attentionin the last years since it was predict a long range magnetic ordering above roomtemperature (RTFM) in such systems [1]. In spite of the extensive studies, theorigin of its magnetic properties still remains a controversial issue. Some recenttheoretical and experimental results have been shown that magnetic orderingdepends on structural defects, such as oxygen vacancies, created during thesample preparation [2, 3]. In this work nanostructured Co-doped Oxides systems,specifically ZnO and CeO2, were synthesized via microwave-assistedhydrothermal route with Co molar concentrations of 1, 3 and 5%. The microwave-assisted hydrothermal method combines the advantages of both hydrothermaland microwave-irradiation techniques such as very short reaction time,production of small particles with a narrow size distribution and high purity whichmight be attributed to fast and homogeneous nucleation of the mixture. Thecrystal structures of the samples were characterized using x-ray diffraction(XRD). The nanostructure and composition distributions were characterized bytransmition electron microscopy (TEM) and energy dispersive x-ray (EDS)measurements. RAMAN scattering was used to study of the incorporation ofdopants and the resulting lattice disorder of the host matrix. Co K-edge x-rayabsorption near-edge structure (XANES) and extended x-ray absorption finestructure (EXAFS) was used to determine the valence state and to evaluate theenvironment of Co in the oxide lattice. Changes in the density of defects wereestimated by RAMAN and Photoluminescence (PL) measurements. Magneticcharacterizations were performed using a superconducting quantum interferencedevice (SQUID) magnetometer. The conjugated different techniques confirmedthe Zn/Ce replacement by Co ions in the host matrix structure. No segregatedsecondary phases neither Co-rich nanocrystals were detected. Defect mediatedmagnetic coupling between the Co atoms under the scope of the bound magnetic

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polarons model is used to interpret the observed magnetic properties. For theZnO system defects at the cation (Zn) sites has prove to be a necessarycondition to achieve the expected RTFM. On the other hand, for the CeO2system, the RTFM is achieved with defects associated to the anion (O) sites. Theauthors are grateful to FAPEMIG, FAPESP and CNPq for financial support. References[1] T. Dietl et al., Science 287, (2000) 1019. [2] En-Zuo Liu et al., Appl. Phys. Lett. 93, (2008) 132506. [3] M. Ivill etal., New. J. Phys 10, (2008) 065002.

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ThP3-19 | Spin injection in n-type resonant tunneling diodes(#237)Y. Galvão Gobato 1, H. V. A. Galeti1, L. F. Dos Santos1,2, Victor López-Richard1,Daniel Cesar1, Gilmar E. Marques1, M. J. S. P. Brasil3, Milan Orlita4,5, J. Kunc5, D.K. Maude4, Mohamed Henini6, R.j. Airey7

1Federal University of São Carlos Physics Department, Via Washington Luis, km235, São Carlos, S.P., 13565-905, Brazil 2Instituto de Fisica de São Carlos, Universidade de São Paulo, São Carlos, S.P.,13560970, Brazil 3Instituto de Física ‘‘Gleb Wataghin’’ Universidade Estadual de Campinas,Campinas, S.P., Brazil 4Grenoble High Magnetic Field Laboratory, Grenoble, France 5Institute of Physics, Charles University, Praha, Czech Republic 6School of Physics and Astronomy, Nottingham Nanotechnology andNanoscience Centre, University of Nottingham, Nottingham, Great Britain7EPSRC National Centre for III-V Technologies, The University of Sheffield,Sheffield, Great Britain ContentWe have studied the polarized-resolved photoluminescence from the contactlayers and the quantum-well (QW) in a n-type GaAs/GaAlAs resonant tunnelingdiode for magnetic fields up to 19 T. We have observed a voltage-controlledpolarization-degree from the QW emission of our resonant tunneling diode (RTD)structure with values up to -63% at 19T . In addition we have observed that thephotoluminescence spectra from the GaAs contact layers comprises therecombination from highly spin-polarized two-dimensional electron (2DEG)- andhole (2DHG)-gases with free tunneling carriers. Both the energy position andintensity of this indirect recombination are voltage-dependent and showremarkably abrupt variations near scattering-assisted tunneling resonances. Weshow that RTDs are interesting systems to investigate the physical properties ofa 2DEG and a 2DHG, as they both can be observed in a single sample. Ourresults also show that these 2D gases can act as spin-polarized sources forcarriers tunneling through the QW in non-magnetic resonant tunneling diodes[1-2]. References[1] Y. Galvão Gobato, H. V. A. Galeti, L. F. dos Santos, V. López-Richard, D. F. Cesar, G. E. Marques, M. J. S. P.Brasil, M. Orlita, J. Kunc, D. K. Maude, M. Henini, R. J. Airey Appl. Phys. Lett. 99, 233507 (2011). [2] H. V. A. Galeti,Y. Galvão Gobato, V.O. Gordo, L. F. dos Santos, M. J. S. P. Brasil, V. López-Richard, G. E. Marques, M. Orlita, J.Kunc, D. K. Maude, M. Henini, R. J. Airey, Semiconductor Science and Technology 27, 015018 (2012).

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ThP3-20 | Voltage controlled spin polarization in p-typeGaAs/AlAs double barrier structures (#278)H. V. A. Galeti1, Anibal T. Bezerra1, Y. Galvão Gobato 1, M. J. S. P. Brasil2, DanielCesar1, Victor López-Richard1, Gilmar E. Marques1, Mohamed Henini3, D. Taylor3

1Federal University of São Carlos Physics Department, Via Washington Luis, km235, São Carlos, S.P., 13565-905, Brazil 2Instituto de Física ‘‘Gleb Wataghin’’ Universidade Estadual de Campinas,Campinas, S.P., Brazil 3School of Physics and Astronomy, Nottingham Nanotechnology andNanoscience Centre, University of Nottingham, Nottingham, Great Britain ContentSpin effects in p-i-p GaAs/AlAs resonant tunneling diodes under magnetic fieldsparallel to the tunnel current have been investigated. The current-voltagecharacteristics curves (I(V)) were measured at 2.5 K for various magnetic fieldsup to 15 T. We have observed several hole-resonant peaks in the I(V) characteristics curves, which we assign to heavy-hole (HH1 and HH2) and light-hole resonances (LH1 and LH2). The spin-dependent tunneling of carriers wasstudied by analyzing the I(V) characteristics curves and the right and left circular-polarized photoluminescence (PL) from the contact layers and the GaAsquantum-well (QW) as a function of the applied bias. We have observed that thecircular polarization degree from the QW and the contact emission are highlylight and bias-voltage sensitive. For low voltages and low laser intensity and magnetic field of 15 T, the QW polarization exhibits strong oscillations withvalues up to 50 % and sign inversions at the voltages corresponding to theresonant tunneling of carriers into the well (Figure 1). The GaAs contact emissionshows several bands including the indirect recombination between free electronsand holes localized at the two-dimensional hole-gas formed at the accumulationlayer (2DHG-e). We have evidence that the spin-polarized hole-gas contributesto the circular-polarization degree of the carriers that accumulate at the QW. Ourresults show, however, that the circular-polarization of the carriers in the QW is acomplex issue, which depends on various factors, including the g-factors of thedifferent layers, the spin-polarization of the carriers in the contact layers, thedensity of carriers along the structure and the Rashba effect. References[1] H.B. de Carvalho, Y.Galvão Gobato, M.J.S.P. Brasil, V. Lopez-Richard, G. E. Marques, I. Camps, M. Henini, L. Eaves, G. Hill,Phys. Rev. B 73, 15531,(2006). [2] H.B. de Carvalho, , M.J.S.P. Brasil, V. Lopez-Richard, Y.Galvão Gobato,G. E. Marques, I.Camps,L.C.O. Dacal, M. Henini, L. Eaves, G. Hill, Phys. Rev. B 74, 041305 (2006). [3] Y. Galvão Gobato, H. V. A. Galeti,L. F. dos Santos, V. López-Richard, D. F. Cesar, G. E. Marques, M. J. S. P. Brasil, M. Orlita, J. Kunc, D. K. Maude,M. Henini, R. J. Airey, Appl. Phys. Lett. 99, 233507 (2011).

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Figure 1:(a),(b) Color-coded maps of QW polarization resolved PL intensities as a function of bias voltage underB=15T (c) I(V) characteristics curve, QW PL intensity and (d) QW polarization degree as a function of biasvoltage at 15T

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ThP3-21 | Low field polar magneto-optical Kerr effect study ofexcitons in GaAs/Al0.3Ga0.7As single quantum well (#304)Ashish Arora, Sandip Ghosh Tata Institute of Fundamental Research Department of Condensed MatterPhysics and Material Sciences, Homi Bhabha Road, Colaba, Maharashtra,Mumbai 400005, India ContentSemiconductor quantum well and superlattice structures are promising materialsfor their potential applications in the field of spintronics, therefore thedetermination of their excitonic Landé g-factors under low magnetic fields isimportant for practical device applications. We present a study of polar Magneto-optical Kerr effect (MOKE) spectroscopy for n = 1 confined electron-heavy hole(e1hh1) and electron-light hole (e1lh1) excitons in 4.2~nm wide GaAs/Al0.3Ga0.7Assingle quantum well grown using metal-oxide vapor-phase epitaxy on GaAs(001)substrate. A photoelastic modulator based polarization modulation technique wasused to perform the MOKE spectroscopy measurements under magnetic fields ofupto 18 kG with samples at ~12 K. Our setup has an additional advantage overthose used traditionally in that we are able to perform the measurements using aconventional H-frame electromagnet without the requirement of a hole in one ofits pole pieces.[1] It is capable of measuring Kerr rotation and ellipticity with anaccuracy of 0.001o at a wavelength of 800 nm. Sharp features observed in theKerr rotation and ellipticity spectra were associated with the excitonic transitionsin the quantum well. A Kramers-Kronig treatment based on MOKE dispersionrelations was used for the confirmation of the Kerr rotation and ellipticity dataobtained. Thereafter, a lineshape analysis of the MOKE spectra was performedthat involved comparison of the experimental data with first principles simulationswhere a generalized Lorentzian (GL) function was used to represent the excitoniccontribution to the dielectric function. Another independent method based on thecomparison of Kerr ellipticity spectrum with the derivative of logarithm ofreflectivity (DLR) was also used to analyze the data. Zeeman splittings obtainedfrom both the methods agree well with each other. Figure 1 shows examples oflineshape fitting of the reflectance and the Kerr spectra. Zeeman splitting for theexcitons was found to behave linearly as a function of applied magnetic field asshown in Fig. 2. Landé g-factors for both the heavy-hole and light-hole excitonswere found to be -0.46 ± 0.002 and 7.42 ± 0.002 respectively. References[1] A. Arora, S. Ghosh and V. Sugunakar, Rev. Sci. Instrum. 82, 123903 (2011).

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Figure 1:(a to c) Lineshape fitting of the reflectance, Kerr rotation and Kerr ellipticity spectra using GL basedmethod and d) Fitting of the Kerr ellipticity spectrum using DLR based method

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Figure 2:e1hh1 and e1lh1 excitonic Zeeman splitting as a function of magnetic field.

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ThP3-22 | The oxygen vacancy influence on magneticproperties of the Fe- and Co-doped SnO2 diluted alloys: atheoretical investigation (#426)Pablo D Borges1, Luísa M. R. Scolfaro 2, Horacio W. Leite Alves3, Eronides F daSilva Jr.4, Lucy V C Assali51Universidade Federal de Vicosa CRP-ICET, Rio Paranaiba, MG, 38810-000,Brazil 2Texas State University Department of Physics, San Marcos, Texas 78666,United States3Universidade Federal de Sao Joao Del Rei, Sao Joao Del Rei, MG, 36301-160,Brazil 4Universidade Federal de Pernambuco Departamento de Fisica, Recife, PE,50670-901, Brazil 5Universidade de Sao Paulo Instituto de Fisica, Sao Paulo, SP, 05315-970,Brazil ContentTransition-metal (TM) doped diluted magnetic oxides (DMOs) have attractedattention from both experimental and theoretical points of view due to theirpotential use in spintronics. Although the existence of room temperatureferromagnetism (FM) in TM-doped SnO2 has been reported, the origin of the FMis still controverse. There are indications that the FM comes from differentsources, like metallic clusters, nanosize secondary phases, or is due to a free-carrier mediated mechanism. The presence of oxygen vacancies has been systematically related to the observed ferromagnetic state. In the present workwe report the magnetic properties of Sn0.96TM0.04O2 and Sn0.96TM0.04O1.98(VO)0.02,where TM = Fe or Co, focusing particularly in the role played by the presence ofO vacancies (VO) nearby the TM. Spin-polarized electronic structure calculationswere performed using the Projector-Augmented-Wave method as implemented inthe Vienna Ab-initio Simulation Package, within density functional theory and thelocal density approximation. The calculated total energy as a function of the totalmagnetic moment per TM (MM) shows a magnetic metastability, correspondingto a ground state, respectively, with 2 and 1 µB/TM, for Fe and Co. Twometastable states, with 0 and 4 µB/TM were found for Fe and a single value of 3µB/TM, for Co. The spin-crossover energies (ES) were calculated and the valuesfound for Fe were ES

0/2 = 107 meV and ES4/2 = 233 meV, while for Co the value

was ES3/1 = 28 meV. By creating O vacancies close to the TM site, the

metastable states and the ES energies change. For iron, a new metastable stateappears with a MM of 6 µB/Fe and the energy barrier relative to the 4 µB/Fe state is 45 meV, while the state with zero MM disappears. The ES

4/2 energylowers down to 30 meV and the ground state has a MM of 4µB/Fe instead of 2µB/Fe. For cobalt, the ground state turned out to be the state with the MM of 3µB/Co and the metastable state the one with MM of 1 µB/Co. The spin-crossoverenergy ES

3/1 decreases to 21 meV. These results suggest that these materialsmay be used in spintronics applications that require different magnetizationstates.

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ThP3-23 | COUPLING EFFECTS ON PHOTOLUMINESCENCE OFEXCITON STATES IN ASYMMETRIC QUANTUM DOTMOLECULES (#455)Nelson Fino, Hanz Ramirez, Angela Camacho Physics Department, Universidad de Los Andes Physics, Bogota D.C., Colombia ContentThe development of novel devices for spintronics and quantum informationprocessing (single photon emitters, quantum logic gates) has been a primarymotivation in the development of nanostructured semiconductors in the last years[1]. Confined excitons offer the possibility of using laser for initialization, readout,and coherent manipulation of spins. We present a theoretical study of the excitonphotoluminescence in InAs/GaAs asymmetric artificial molecules, where interdotcoupling is tuned via magnetic field in the Faraday configuration [2]. Electronicstructure is obtained by finite element calculations and Coulomb effects areincluded using a perturbative approach. Appearances of interdot energyresonances, and the magnitude of required fields for reaching them, are found tobe strongly dependent on the geometry parameters. According our simulatedspectra, excited bright exciton states may become optically accessible at lowtemperatures in hybridization regimes where intermixing with the ground state isachieved. Our results show efficient magnetic control on the energy, polarizationand intensity of emitted light, and suggest these coupled nanostructures asrelevant candidates for implementation of quantum optoelectronic devices. References[1] M. F. Doty, M. Scheibner, A. S. Bracker, I. V. Ponomarev, T. L. Reinecke, and D. Gammon, Phys. Rev. B 78 , 115316

(2008). [2] M. Bayer, O. Stern, A. Kuther, and A. Forchel, Phys. Rev. Lett. 101 , 267402 (2008) .

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ThP4-1 | Mg-doped indium rich GaxIn1-xN: evidence for p-typeconductivity (#63)Naci Balkan 1, Engin Tiras2, Ayse Erol3, Mustafa Gunes3, Sukru Ardali2, M. CetinArikan3, Delphine Lagarde4, Helene Carrere4, Xavier Marie4, Cebrail Gumus5

1university of essex CSEE, Colchester, CO43SQ, Great Britain2Anadolu University physics, Eskisehir, Turkey 3Istanbul University physics, Istanbul, Turkey 4INSA LPCNO, F-31077 Toulouse, France 5Cukurova University Physics, Adana, Turkey ContentWe report on the Mg doped indium rich GaxIn1-xN (x<30). In the nominallyundoped material where the electron density is very high, there is no detectablephotoconductivity (PC) signal within the range of temperatures of 30K<T<300K. In the Mg doped material however, there is a strong PC spectrum with twoprominent low energy peaks at 0.65 eV and 1.0 eV and one broad high energypeak at around 1.35 eV. The temperature dependence of the spectralphotoconductivity, under constant illumination intensity at T > 150K, isdetermined by the LO phonon scattering together with the thermal re-generationof non-equilibrium minority carriers from traps with an average depth of 103 ±15meV. This is close to the Mg binding energy in GaInN. The complementarymeasurements of transient PL at liquid He temperatures give the e-A0 bindingenergy of around ~100 meV. Furthermore, Hall measurements in the Mg dopedmaterial are also indicative a conduction mechanism with an acceptor bindingenergy of 108 ± 20meV. References1. J. W. L. Yim,R. E. Jones, K. M. Yu,2 J. W. Ager, W. Walukiewicz, W. J. Schaff and J. Wu Phys. Rev. B 76,041303 (2007) 2. D. Zanato, N. Balkan, B.K. Ridley, G. Hill and W.J. Schaff, Semiconductor Science and Technology19(8), 1024-1028, (2004) 3. E. Tiras, D. Zanato, S. Mazzucato, N. Balkan and W. J. Schaff, Superlattices andMicrostructures 36, 473-485, (2004)

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Figure 1:PL spectra in undoped and Mg doped GaInN

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ThP4-2 | The ionization potential and electron detachmentenergy of small aluminum clusters (#212)Ladir Cândido1, José N. Teixeira Rabelo1, Guo-Qiang Hai 2

1Universidade Federal de Goiás Instituto de Física, Goiânia, GO, 74001-970,Brazil 2Universidade de São Paulo Instituto de Física de São Carlos, Av. TrabalhadorSãocarlense 400, São Carlos, SP, 13560-970, Brazil ContentIn the last two decades, considerable effort has been made in trying tounderstand the properties of the Al clusters and nanoparticles. Experimental andtheoretical studies have been carried out to obtain the ionization potential,electron affinity and detachment energy of Al clusters as a function of theiratomic size. These studies have provided valuable information for ourunderstanding on the Al clusters. However, due to lack of accuracy both intheoretical and experimental techniques, it is still challenging to obtain theirvalues in chemical accuracy. Density functional theory (DFT) with approximatedlocal and semi-local exchange-correlation (xc) energy functionals is currently thestandard approach for computing materials properties and has been successfulin studies for a wide range of materials. However, it is often doubtful on theaccuracy of calculated results within DFT at describing a given property ofmaterials due to the approximations in xc energy. In order to obtain theoreticalresults with better precision and clarify previous theoretical calculations, in thiswork, we employ fixed node diffusion quantum Monte Carlo (FN-DMC) method tostudy the electronic structure of small Aln(n=1-13) clusters in comparison with theDFT calculations. We calculate the total energies of the relaxed and unrelaxedaluminum clusters and extract the ionization potential and electron detachmentenergy. Our results from both the FN-DMC and DFT calculations are inreasonably good agreement with the available experimental data. However, acomparison reveals that the DFT calculations systematically underestimate thetotal energies of the clusters up to 1 eV. As a consequence, the DFT cannotpredict correctly the alternations in the order of sub-electron-volt in the ionizationpotential and electron detachment energy. The figures below show thedependences of the vertical and adiabatic ionization potential on the cluster sizefrom the FN-DMC and DFT-PBE calculations. The green vertical bars indicatethe experimental data[1]. This work was supported by FAPESP and CNPq(Brazil). References[1] D. M. Cox, D. J. Trevor, R. L. Whetten, and A. Kaldor, J. Phys. Chem. 92, 421 (1988).

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Fig. 1:The vertical and adiabatic ionization potential of the Al clusters

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ThP4-3 | Determination of Operation Region in Silicon-Nanowire BioFETs to Maximize Signal-to-Noise Ratio (#242)Sungho Kim 1, Taiuk Rim1, Kihyun Kim1, Eunhye Baek2, Unsang Lee2, NankiHong1, Changki Baek3, Sooyoung Park3, Jeong-Soo Lee1,2, Yoon-Ha Jeong1,3

1Pohang university of science and engineering Department of ElectricalEngineering, 77 Cheongam-ro. Nam-gu., Pohang 790784, Korea Republic (South)2Pohang university of science and engineering Division of IT-ConvergenceEngineering, 77 Cheongam-ro. Nam-gu., Pohang 790784, Korea Republic (South)3Pohang university of science and engineering Department of Creative ITExcellence Engineering, 77 Cheongam-ro. Nam-gu., Pohang 790784, KoreaRepublic (South) ContentAdvances of the information technology, biotechnology and nanotechnologyenable the concept of the ubiquitous-health care (U-health) service[1-3]. For a U-health biosensor platform, the Si-nanowire biologically-selective FET (Si-NWBioFET) is the most promising device [4]. In this study, we fabricated Si-NWBioFETs and measured electrical characteristics including noise characteristics. The Si-NW BioFET was fabricated using conventional top-down semiconductorfabrication process. To enhance a current drivability, 10-nanowires with 50-nmwidth and 10-µm length are arranged in a device. An embedded Ag/AgClpseudo-reference electrode which is placed about 600-µm away from thenanowire was fabricated using an electrochemical technique. For themeasurement, 30 µl of 0.1X phosphate buffered saline (PBS) was dropped onthe device. The pH value of 0.1 X PBS solutions was adjusted using 1M HCland1M NaOH solution. The Si-NW BioFET showed sub-threshold slope of120mV/dec, on-off current ratio of 105 under the various pH conditions (Fig. 1).As the pH value of 0.1X PBS solution decreased, the threshold voltage of thedevice also decreased. The hydroxyl groups (-OH) on the SiO2 are protonatedwith the H+ ions in the solution and form OH2

+. The additional positive charges onthe SiO2 surface attract negative charges on the nanowire and make thethreshold voltage shift to the negative direction. To evaluate noise characteristicsof Si-NW BioFET, we measured the noise spectral density on drain current. Fromthe measured noise spectral density, the noise RMS value can be easilyextracted by simple calculation [5]. As the drain current increased, the sensitivityof the Si-NW BioFET decreased and the noise RMS voltage increased (Fig. 2).The Si-NW BioFET shows higher sensitivity with lower noise at the sub-thresholdregion. Therefore the Si-NW BioFET should be biased in this operation region forsensing application. AcknowledgementsThis work was partially supported bythe BK21 program and by the WCU (World Class University) program throughthe National Research Foundation of Korea funded by the Ministry of Education,Science and Technology (Project No. R31-2008-000-10100-0). This work wasalso supported by the MKE(The Ministry of Knowledge Economy), Korea, underthe “IT Consilience Creative Program” support program supervised by theNIPA(National IT Industry Promotion Agency)" (C1515-1121-0003).

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References[1] M. Meyyappan, “Moore and more progress in electronics and photonics,” Nanotechnology, vol. 20, pp. 2, 2009. [2]H. J. Lee, S. H. Lee, K. S. Ha, H. C. Jang, W. Y. Chung, J. Y. Kim, Y. S. Chang, and D. H. Yoo, “Ubiquitoushealthcare service using Zigbee and mobile phone for elderly patients,” International Journal of Medical Informatics,vol. 87, issue 3, pp. 193-198, Mar. 2009 [3] N. Bricon-Souf, and C. R. Newman, “Context awareness in health care: Areview,” International Journal of Medical Informatics, vol. 76, issue 1, pp. 2-12, Jan. 2007 [4] I. Park, Z. Li, X. Li, A. P.Pisano, and R. S. Williams, “Towards the silicon nanowire-based sensor for intracellular biochemical detection,”Biosensors and Bioelectronics, Vol. 22, pp. 2065-2070, Oct. 2007. [5] S. Kim, T. Rim, K. Kim, U. Lee, E. Baek, H.Lee, C. K. Baek, M. Meyyappan, M. J. Deen and J. S. Lee, “Silicon nanowire ion sensitive field effect transistor withintegrated Ag/AgCl electrode: pH sensing and noise characteristics,” Analyst, Vol. 136, pp. 5012-5016, Oct. 2011.

Figure 1:Transfer characteristics of Si-NW BioFET under various pH conditions.

Figure 2:pH sensitivity and the noise RMS voltage of Si-NW BioFET when drain current of 1 nA, 20 nA, 70 nA, and140 nA flows.

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ThP4-4 | Investigation of Photoconductive Properties of ZnOnanoparticles (#366)Ayse Erol 1, Salih Okur2, M. Cetin Arikan1, Bulent Comba1

1Istanbul University Physics Department, Science Faculty, 34134 Istanbul,Turkey 2Izmir Katip Celebi University Department of Metallurgy, Faculty of Engineering,35620 Izmir, Turkey ContentPhotoconductive properties of ZnO nanoparticles with ~10 nm diameter wereinvestigated under ambient, vacuum and oxygen environments using UV lightillumination. ZnO nanoparticles are synthesized via a sol-gel method. Themorphology and crystal structure of the ZnO nanoparticles have beencharacterized by Scanning Electron Microscopy (SEM) and X-Ray diffraction(XRD), respectively. The band gap of the synthesized ZnO nanoparticles hasfound approximately 3.3eV. Transient photoconductivity measurement is doneunder UV light illumination. The response of the ZnO nanoparticles wasdetermined by electrical resistance measurements. It is observed that ZnO isvery sensitive material to humidity changes therefore; transient PCmeasurements are carried out ambient and vacuum environment. The resultsshowed that sensitivity of ZnO nanoparticles increases by an order 0f 4 under200 W UV light illumination and depends on humidity and oxygen amount in theenvironment.

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ThP4-5 | Intrinsic Reliability Improvement of SiGe QuantumWell pMOSFETs (#388)Do-Young Choi 1, Chang-Woo Sohn1, Hyun-Chul Sagong1, Eui-Young Jung2,Jun-Woo Jang3, Chang-Ki Baek3, Jeong-Soo Lee1,2, Yoon-Ha Jeong1,3

1POSTECH Electrical Engineering, Pohang 790-784, Korea Republic (South)2POSTECH IT-Convergence Engineering, Pohang 790-784, Korea Republic(South)3POSTECH Creative IT Excellence Engineering, Pohang 790-784, KoreaRepublic (South) ContentINTRODUCTION: High-mobility SiGe Quantum Well (QW) pMOSFETs havebeen demonstrated to be viable candidates for future high-speed applications [1].Negative-bias temperature instability (NBTI) is considered a major reliabilityconcern for scaled CMOS technology [2]. In this paper, we investigated theimproved NBTI characteristics of SiGe-QW pMOSFETs compared toconventional Si-channel pMOSFETs. RESUTLS AND DISCUSSION: In Fig. 1,the NBTI characteristics of SiGe-QW pMOSFETs with HfO2/SiO2 gate dielectricand metal gate were investigated and for comparison, conventional Si-channelpMOSFETs with same gate dielectric and metal was also investigated. TheSiGe-QW pMOSFETs showed a lower threshold voltage instability (∆Vth) than Si-channel pMOSFETs, which was attributed to QW-induced low tunnelingprobability of carriers from the channel to bulk traps in the dielectrics [3]. Besides,it is noted that the SiGe-QW pMOSFETs showed a higher percentage ofrecovery (R) that was defined as (∆Vth(500s)-∆Vth(1000s))/∆Vth(500s). The Rincreased linearly with the applied effective oxide field (Eox) for both devices(inset of Fig. 1). As shown in Fig. 2, the field-dependent recovery characteristicswas originated from the fast recovery component which occurred by tunnelingfrom bulk traps to the channel [4]. The fast recovery component varies with Eox

because of filed-dependent defect band (inset of Fig. 2) and high Eox gives rise tolow R due to the large amount of trapped charges far away from the Fermi levelat recovery condition. In addition, the high R of SiGe-QW pMOSFETs wasattributed to its small amount of trapped charges. CONCLUSION: The SiGe-QW pMOSFETs showed improved recovery characteristics as well as lowerdegradation than Si-channel pMOSFETs. In real conditions, there is moreimprovement of lifetime compared to Si-channel pMOSFETs than that derivedfrom stress-only reliability tests. ACKNOWLEDGEMENTS: This work waspartially supported by the BK21 program and by the WCU (World ClassUniversity) program through the National Research Foundation of Korea fundedby the Ministry of Education, Science and Technology (Project No.R31-2008-000-10100-0). This work was also supported by the MKE (The Ministryof Knowledge Economy), Korea, under the “IT Consilience Creative Program”support program supervised by the NIPA (National IT Industry PromotionAgency)" (C1515-1121-0003). References[1] J. Mitard, L. Witters, M. Garcia Bardon, P. Christie, J. Franco, A. Mercha, P. Magnone, M.Alioto, F. Crupi, L.-Å.

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Ragnarsson, A. Hikavyy, B. Vincent, T. Chiarella, R. Loo, J. Tseng, S. Yamaguchi, S. Takeoka, W-E. Wang, P. Absiland T. Hoffmann, " High-mobility 0.85nm-EOT Si0.45Ge0.55-pFETs: delivering high performance at scaled VDD," inIEDM Tech. Dig., 2010, pp. 249-252. [2] J. Franco, B. Kaczer, G. Eneman, J. Mitard, A. Stesmans, V. Afanas’ev, T.Kauerauf, Ph.J. Roussel, M. Toledano-Luque, M. Cho, R. Degraeve, T. Grasser, L.-Å. Ragnarsson, L. Witters, J.Tseng, S. Takeoka, W.-E. Wang, T.Y. Hoffmann, and G. Groeseneken, " 6Å EOT Si0.45Ge0.55 pMOSFET withoptimized reliability (VDD=1V): meeting the NBTI lifetime target at ultra-thin EOT," in IEDM Tech. Dig., 2010, pp.70-73. [3] J. Franco, B. Kaczer, M. Cho, G. Eneman, and G. Groeseneken, "Improvements of NBTI reliability in SiGep-FETs," in proc. IRPS 2010, pp. 1082-1085. [4] D. Heh. R. Choi, C. D. Young, and G. Bersuker, "Fast and slowcharge trapping/detrapping process in high-k nMOSFETs," in proc. IIRW 2006, pp. 120-124.

Figure 1:NBTI characteristics of SiGe-QW and Si-channel pMOSFETs under same effective oxide field (Eox)(Eox=-7 MV/cm and -10.3 MV/cm) at 125 °C. Inset shows the dependence of percentage of recovery (R)on Eox.

Figure 2:Field dependence of fast, slow and total recovery. Inset shows energy band diagram and defect bandcorresponding to recovery, low and high stress conditions (only Ev is described for low and high stressconditions).

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ThP4-6 | Characterization of as-grown and annealedmodulation doped Ga1-xInxNyAs1-y /GaAs quantum wellstructures using Infrared spectroscopy and Raman scatteringtechniques (#415)Elif Akalin 1, Ayse Erol1, Sevim Akyuz2, M. Cetin Arikan1, Janne Puustinen3,Mircea Guina3

1Istanbul University Physics Department, Science Faculty, 34134 Istanbul,Turkey 2Istanbul Kultur University Physics Department, Faculty of Science andEngineering, 34156 Istanbul, Turkey 3Tampere University of Technology Optoelectronics Research Centre,Korkeakoulunkatu 3, 3720 Tampere, Finland ContentFT-Raman, Micro-Raman and Attenuated Total Reflection (ATR) InfraredSpectroscopy have been performed to investigate the effect of Nitrogen amountand annealing process on phonon scatterings and chemical bond configuration inas-grown and annealed n- and p-type modulation doped Ga1-xInxNyAs1-y/GaAsquantum well (QW) structures. The samples were grown by molecular beamtechnique (MBE) with different N concentrations (y = 0, 0.9, 1.2, 1.7) at the sameIn concentration of 32%. Micro-Raman scattering measurements are carried outusing 532 nm diode laser (green) and 785 nm diode laser (red) whereas FT-Raman scattering measurements are carried out using a 1064 nm Nd-YAG laser.Raman scattering measurements reveals that excitation source has a criticalimportance to observe vibrational modes. The fact that Raman scatteringmeasurements with 785 nm (red) and 1064 nm are in resonance with GaAs andGa1-xInxNyAs1-y band gap energy results in an electronic transition-dominant peakin the spectra. On the otherhand, Raman scattering with green laser (532 nm) isnot in resonance with any constituent semiconductors in the samples therefore,only vibrational modes are observed in the spectra. Micro-Raman with greenlaser and ATR spectroscopy results can be used to understand the effect of Namount and annealing on phonon modes and chemical bond preference in thesamples. The results indicate that Raman scattering (with 1064 nm and 785 nmlaser) may be a useful tool to determine the band gap energy of the samples,along with the phonon modes that are not suppressed by the electronic transitionpeak. Traditionally, PL measurements are employed to characterize radiativetransitions in semiconductors and the sample quality is the key parameter toobserve PL spectrum with low excitation power at room temperature. It is well-known that N-containing materials suffer from optical quality due to N-induceddefects and the quality is deteriorated with increasing N content that causes toobserve very weak PL signal at room temperature. It is realized that even at verylow laser powers, about a few watts, FT- Raman spectrum is more sensitive andhave the same characteristics with PL measurements. Therefore, FT- Ramanscattering have been used to probe the effect of N amount and annealing onelectronic transitions, i.e. effective band gap energy, of the samples.

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ThP4-7 | Generation of Ultra-Violet Sub-nanosecond OpticalPulses from AlGaN LEDs (#419)Pierre Renucci 1, Phi Hoa Binh2, Cong Tu Nguyen1, Tiantian Zhang1, XavierMarie1

1Université de Toulouse INSA-CNRS-UPS, LPCNO, 135 avenue de Rangueil,31077 Toulouse, France 2Institute of Material Science, 18 Hoang Quoc Viet Road Cau Giay Dist, Hanoï10000, Vietnam ContentLight Emitting Diodes (LEDs) have recently experienced a spectaculardevelopment. However LEDs still suffer from poor modulation bandwidths, whichare typically smaller than 300 MHz in commercial devices. Increasing thismodulation bandwidth would yield the development of many applicationsincluding low-cost short distance telecommunication by optical fibre forembedded systems (automotive, aircrafts), smart lighting applications andfluorescence lifetime measurements in biology. We demonstrate here that anovel pulse shaping circuit connected to AlGaN quantum well LEDs allows us togenerate sub-ns optical pulses in the ultra-violet region. This pulse shaping issimply obtained with a parallel Schottky-Capacitance circuit in series with theLED [1] which yields much better performances in terms of generated peakpower compared to classical pulse peaking circuits based on R-C [2] . We haveinvestigated LEDs emitting at different wavelenghts: 270, 315, 335, and 355 nm.For all these LEDs, sub-nanosecond optical pulses were generated with intensepeak power and repetition frequency up to 150 MHz. As an example figure 1displays the measured time-resolved electroluminescence intensity using aStreak camera (time-resolution: 125 ps) for the 270 nm LED. The AlGaN LEDconnected to the Schottky-C pulse shaping circuit is driven with a rectangularpulse wave-shaped signal with a pulse-width of 1 ns (frequency 80 MHz). Wemeasure a pulse width of ~750 ps (FWHM) and a peak power of 0.65 mW.These fast pulsed LEDs, emitting in a spectral region where no diode lasers areavailable, have strong potential for applications in time-resolved fluorescencespectroscopy, biochemical analysis and calibration of fast optoelectronic devicessuch as scintillation counters and photomultiplier tubes. References[1] P.H. Binh, X. Marie, P. Renucci, V.G. Truong and, Patent n° FR2953343, International PCT PatentWO2011067514 (2009) [2] E.F. Schubert , ‘Light Emitting Diodes’, (Cambridge University Press, Cambridge, 2006)

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Figure 1:LED electroluminescence as a fucntion of time. Inset: LED electroluminescence spectrum

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ThP4-8 | Enhancement of Room TemperatureMagnetoresistance in Non-Uniform Size and Distribution ofClusters in Polyaniline-Iron Oxide Nanocomposites (#429)Aigu Lin 1,2, Andrew Wee1,2, Wei Chen1,2, Tom Wu3

1National University of Singapore NUS Graduate School for Integrative Sciences& Engineering, Centre for Life Sciences (CeLS), #05-01 28 Medical Drive, sg117456, Singapore 2National University of Singapore Physics, 2 Science Drive 3, sg 637371,Singapore 3Nanyang Technological University School of Physical & Mathematical Sciences,SPMS-04-01, 21 Nanyang Link, sg 637371, Singapore ContentSpintronics1-3 or Spin Transport Electronics is an emerging technology whichuses the electron spin to store information. In recent years, there has been muchinterest in organic spintronics devices4-6 which have the advantage over theirinorganic counterparts due to their very weak spin-orbit coupling which allows fora long spin diffusion length, as well as being cheap, flexible and easy to process.However initial organic spintronics devices such as organic spin valves werereported to have a room temperature magnetoresistance of less than 20%, wellbelow the limit needed for applications7-11 We demonstrate a polyaniline-ironoxide nanoparticle (PANI-NP) organic hybrid composite device with roomtemperature positive magnetoresistance of 89%, several times higher than thebest reported values for organic-based devices. Temperature dependentresistivity measurements attribute this observation to the decrease in localizationlength of the charge carriers in the presence of an external magnetic field. Inaddition, it is found that the charge transport occurs via the 3D Variable RangeHopping mechanism. The decrease in localization length, coupled with the non-uniform distribution of the localized sites (as well as their different sizedistribution) makes charge transport even more difficult as some neighbouringclusters are found at distances far above the localization length, thus makinghopping to those clusters unlikely. The device is also able to maintain its resistivestate even when the power is switched off, thus exhibiting a memory effect. References[1] Zutic, I.; Fabian, J.; Das, S., Rev. Mod. Phys., 2004, 76, 323-410 [2] Das, S. , Am. Sci., 2001, 89, 516 [3] Prinz,G. A., Science, 1998, 282, 1660- 1663 [4] Wolf, S. A.; Awschalom, D. D; Buhrman, R. A.; Daughton, J. M., vonMolnar, S.; Roukes, M. L.; Chtchelkanova., A. Y.; Treger, D. M., Science, 2001, 294, 1488- 1495 [5] Sugawara, T.;Matsushita, M., J. Mater. Chem., 2009,19, 1738- 1753 [6] Xiong, Z.H.; Wu, D.; Vardeny, Z.V.; Shi, J. , Nature,2004,427,821-824 [7] Campbell, J. S.; Bozano, L. D., Adv. Mater., 2007, 19, 1452- 1463 [8] Francis, T. L.; Mermer,O.; Veeraraghavan, G.; Wohlgenannt, M., New. J. Phys. , 2004, 6, 185 [9] Mermer, O.; Veeraraghan, G.; Francis,T.L.; Sheng, Y.; Nguyen, D.T.; Wohlgennant, M.; Kohler, A.; Al-Suti, M.K.; Khan, M.S., Phys. Rev. B, 2005, 72,205202 [10] Barraud, C.; Seneor, P.; Mattana, R.; Fusil, S.; Bouzehouane, K.; Deranlot, C.; Graziosi, P.; Hueso, L.;Bergenti, I.; Dediu, V.; Petroff, F.; Fert., A. , Nature Phys. ,2010, 6, 615-620 [11] Naber, W.J.M.; Faez, S.; van derWiel, W. G., J. Phys. D., 2007, 40, R205-R228

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Localization Length :The change in localization lengths of the different nanocomposites with different iron oxide nanoparticleconcentrations under the influence of an external magnetic field from 0.1 T to 0.6 T.

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Material Characterization:Magnetic field dependence of the magnetoresistance for different nanoparticle concentrations togetherwith their TEM images. (a)Iron Oxide nanoparticles 2% by volume. (b) 6% by volume (c) 10% by volume(d) demonstration of memory effect

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ThP4-9 | Effect of energy and fluence of energetic N2+ ions on

the formation of silicon nitride on Si(111) substrate (#440)Praveen Kumar 1, S. M. Shivaprasad2

1Institute for Systems based on Optoelectronics and Microtechnology TechnicalUniversity of Madrid, 28040 Madrid, Spain2CPMU Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore560064, India ContentThe large lattice and thermal expansion mismatch between Si and GaN result inthe highly defected GaN films on Si(111) substrate. However, to improve thequality of GaN films different approaches such as buffer layers, use of surfactant,patterning of the substrate surface (ELOG), surface modifications etc. have beentried in the literature. The surface modification of Si into silicon nitride (Si3N4)could be an alternate solution to other techniques because of having nearlydouble lattice parameter, anti-surfactant nature and process compatibility to theexisting growth process of GaN films. In this work, we present the surfacemodification of Si(111) into silicon nitride by using low energetic N2

+ ions. Theenergy and fluence of energetic N2

+ ions have been optimized for the formation ofstoichiometric silicon nitride. The experiments have been performed in-situ in UHVsystem, equipped with X-ray photoelectron spectroscopy. We have used lowenergetic N2

+ ion beam in the energy range of 0.2 to 5.0keV for the different ionfluence to induce surface reactions, which leads to the formation of Si3N4 onSi(111) surface. The XPS core level spectra of Si(2p) and N(1s) have beendeconvoluted into different oxidation states to extract qualitative information,while survey scan has been used for quantitative analysis (atomic %composition) for the silicon nitride formation. The uptake curve for the nitridationprocess demonstrate that surface nitridation initially increase rapidly with ionfluence after that it slow down and finally reaches saturation at higher N2

+ ionfluence. The fluence require to reach saturation increases from 4.0x1015ions/cm2

for 1keV, 1.18x1016 ions/cm2 for 2keV and 1.7x1017 ions/cm2 for 5keV N2+ ions.

This modified surface can be used as a template to grow GaN with low defects tointegrate the III-nitride with silicon technology. References1. Praveen Kumar, M. Kumar, Govind, B.R. Mehta, S.M. Shivaprasad, Applied Surface Science, 256 (2009) 517. 2. Praveen Kumar, L. Nair, S. Bera, B.R. Mehta, S.M. Shivaprasad, Applied Surface Science, 255 (2009) 6802.3. Praveen Kumar, S. Bhattacharya, Govind, B. R. Mehta, and S. M. Shivaprasad, J. Nanosci. Nanotechnol. 9, (2009)5659.

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ThP4-10 | The effect of 1-dimensional nanostructure preparedby solvent treatment of photoactive layer on the performanceof polymer solar cell (#504)Sungho Woo 1, Jaehoon Jung1,2, Hong-Kun Lyu1, Wookhyun Kim1, HyunminPark1, Jihee Jung1, Youngkyoo Kim2

1Daegu Gyeongbuk Institute of Science & Technology Green energy researchdivision, 50-1, Sang-ri, Hyeonpung-myeon, Dalseong-gun, Daegu 711-873,Korea Republic (South)2Kyungpook National University Department of Chemical Engineering, 1370,Sankyuk-dong, Buk-gu, Daegu 702-701, Korea Republic (South) ContentIn recent years, much effort has been devoted toward developing high efficiencyorganic based solar cells that are easily processed, mechanically flexible, andhave low fabrication costs for large area. The highest power conversionefficiency of organic solar cell is now over 10%, which is thought to be a goal forcommercialization of organic solar cell into photovoltaic market. Although theircell performance has been largely enhanced, there are still many issues toimprove such as long-term stability and large area module efficiency. In thisstudy, we checked the effect of 1-dimensional nanostructure embedded in thebulk heterojunction active layer. This nanostructure, obtained by a careful solventtreatment of photoactive solution, is expected to be useful for the formation ofcharge transfer path and eliminating the post thermal or solvent treatment toproduce well-ordered morphology. The UV-Vis absorption and deviceperformance properties will be discussed fully. References1. H.-L. Yip, A. K.-Y. Jen, Energy Environ. Sci., 5, 5994 (2012) 2. F. He, L. Yu, J. Phys. Chem. Lett., 2, 3102 (2011)3. H. Xin, O. G. Reid, G. Ren, F. S. Kim, S. S. Ginger, S. A. Jenekhe, ACS nano, 4, 1861 (2010) 4. J.-H. Kim, J. H.Park, J. H. Lee, J. S. Kim, M. Sim, C. Shim, K. Cho, J. Mater. Chem., 20, 7398 (2010)

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ThP4-11 | Assembling of palladium nanoparticles at vanadiumdioxide nanowire surface using dielectrophoresis (#507)Youngreal Kwak1, Gil-Ho Kim 1, Ji-Won Byon2, Jeong Min Baik2

1Sungkyunkwan University School of Electronic and Electrical Engineering andSungkyunkwan Advanced Institute of Nanotechnology (SAINT), Suwon 440-746,Korea Republic (South)2Ulsan National Institute of Science and Technology (UNIST) School ofMechanical and Advanced Materials Engineering, Ulsan 689-805, KoreaRepublic (South) ContentZero or one dimensional materials, such as nanoparticles, semiconductorquantum dots, or nanowires are currently of intense research interest due notonly to understanding their fundamental sciences but also to their wide variety ofpotential applications in various fields such as electronics, optics, sensors,photovoltaic, biology, and medicine. These nano-materials of nanoparticles andnanowires suggest that the integration of electrical and optical nano devices withthese nano-objects may generate hybrid systems that combine the properties ofthe low dimensional materials with new functions of nano devices. On thevanadium dioxide (VO2) nanowire1 surface, palladium nanoparticles have beenassembled by optimized dielectrophoresis process. Depending on thedielectrophoresis2 parameters, such as frequency, trapping time and voltage ledto different converge of palladium nanoparticles on the VO2 nanowire. This novelfabrication with combination of nanowire and nanoparticles has demonstrated anexcellent performance as a controlled density of the nanoparticles on thenanowire surface. Palladium nanoparticles nanoparticles of diameter in the range2–4 nm were assembled on the vanadium dioxide VO2 nanowire surface using acdielectrophoresis process. Depending on the dielectrophoresis parameters, suchas frequency, trapping time and voltage led to different converge of palladiumnanoparticles on the VO2 nanowire. A lump of palladium nanoparticles weredistributed on the VO2 nanowire when measurement time was stopped withremaining a palladium solution. New assembled palladium nanoparticles aspectwas observed much less lump of palladium and good distribution on the VO2

nanowire just before dry out a palladium solution. Mutual dielectrophoresis couldbe attributed to the nanoparticles force with solution and subsequently thedielectrophoresis force directs this trapping region. Such controlled assembly ofindividual nanoparticles may find application in fabricating devices for gassensor. References[1] J. M. Baik et al., Nano Lett. 9, 3980 (2009). [2] Binh Le Huy, Sanjeev Kumar and Gil-Ho Kim, J. Phys. D: Appl.Phys. 44, 325402 (2011).

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ThP4-12 | Electronic properties of ZnO and NB hexagonalmonolayers (#508)A. M. Rojas-Cuervo, J. D. Rojas Bonilla, R. R. Rey-González Universidad Nacional de Colombia - Bogotá Facultad de Ciencias,Departamento de Física, Grupo de Óptica e Información Cuántica, Carrera 30Calle 45-03, C. P. 111321 Bogotá, Colombia ContentIn the last years nanotechnology, as multidisciplinary science, has become a fieldof great interest of research and innovation, due to significant progress thatexpected in the near future a big variety of technological applications. So,attempting to obtain novel materials has motivated new theoretical andexperimental studies. In this context, graphene had show very interest unusualproperties. It is the first real two dimensional material, and it presents a linearelectronic dispersion near to Fermi energy level, the called Dirac's cones.Recently, other systems that crystallize in the same way that graphene havebeen attracted theoretical and experimental interest. In particular, there are twoopen questions about them: Is it possible to obtain other real two dimensionalmaterial? Is the linear electronic dispersion unique for graphene? There arepreliminary theoretical studies for hexagonal lattices of Si, Ge, GaN and GaAs. Other possible hexagonal monolayers are made of Boron nitride (h-BN) and ZincOxide (h-ZnO). The first one is a interest material due to it can be coupled withBoron Nitride nanotubes in electronic devices. In the present work we do an abinitio theoretical study of h-BN and h-ZnO. We use the SIESTA code [1] as oneDFT implementation. This method uses localized atomic orbital as basis.Exchange and correlation energy are calculated into the Generalized GradientApproximation with non local pseudo potentials which are optimized including alarge number of Kleinman-Bylander projectors. We report the chemical stability,the lattice parameter, electronic properties as the dispersion relation, the densityof states and the charge density and phonon dispersion for theses systems. References[1] José M Soler, Emilio Artacho, Julian D Gale, Alberto García Javier Junquera, Pablo Ordejón, Daniel Sánchez-Portal. J. Phys.: Cond. Matt 14, 2745 (2002).

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ThP4-13 | Transmission electron microscope observation oforganic-inorganic hybrid thin active layers of light-emittingdiodes (#523)Yusuke Jitsui, Naoki Ohtani Doshisha University Electronics, 1-3 Tatara-Miyakodani, Kyoto, Kyotanabe6100321, Japan ContentOrganic light-emitting diodes (OLEDs) are energetically investigated for theapplication to flat-panel displays and illumination light sources. However, theoperation lifetime of OLEDs is very short than that of inorganic LEDs, becauseOLEDs is strictly affected by the oxidant effect. Very recently, we fabricatedorganic-inorganic hybrid LEDs in which the active layers consist of organicemissive materials dispersed in SiO2 [1]. These novel LEDs exhibit very longoperation lifetime, because the organic emissive materials in SiO2 are protectedagainst the oxidant effect. However, the structures of the fabricated organic-inorganic hybrid active layers are still unknown. In this research, we performtransmission electron microscope (TEM) observation of them. The organic-inorganic hybrid thin films were fabricated by sol-gel method. An organicemissive material TFB and Perhydropolysilazane (PHPS) were dissolved inxylene. Then, a thin film of the TFB-PHPS solution was fabricated on SiO2

substrate by spin-coating method. Thirdly, the sample was annealed to removeof xylene. Finally, the thin film was tuned into the organic-inorganic hybridmaterial by humidity treatment of 80 RH in 60 minutes. We confirmed that thefabricated thin film exhibits photoluminescence (PL) signal from TFB. Figure 1shows a cross-sectional TEM image of the sample studied. It was clearlyobserved that the fabricated thin film consists of three stacked layers. Thethicknesses of these layers from the surface were about 10 nm (Layer A), 30 nm(Layer B) and 10 nm (Layer C). In order to evaluate the composition of thelayers, the distribution of atoms in them was measured by energy dispersive X-lay fluorescence spectroscopy (EDS). Figure 2 shows the results of EDSmapping of three atoms, silicon (a), oxygen (b), and carbon (c). It is very clearthat the atoms of silicon and oxygen are not contained in Layer B. On the otherhand, the atoms of carbon are clearly contained in Layer B. This result clearlydemonstrates that organic materials concentrate in Layer B. In addition, Layers Aand C consist of SiO2. Since it was confirmed by PL measurement that themolecular structure of TFB was not destroyed, the structure of the organic-inorganic hybrid thin film can be identified as the sandwich structure in which theorganic emissive material TFB is sandwiched by SiO2 layers. As a consequent,the organic emissive material can be protected against the oxidant effect. References[1] Y. Jitsui, S. Kimura, and N. Ohtani, submitted to ICPS 2012.

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Figure 1:Cross sectional TEM image.

Figure 2:Distribution of three atoms, (a) silicon, (b) oxygen, and (c) carbon.

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ThP4-14 | Nano-scale Field Effect Transistors for Bio-sensingApplications (#565)Aditya Rajagopal , Chieh-Feng Chang, Sameer Walavalkar, Axel SchererCalifornia Institute of Technology Electrical Engineering, MC 200-36 1200 E.California Blvd., Pasadena, California 91125, United States ContentField effect transistors can be used as sensors for a variety of bio-relatedapplications. Specifically, the nano-pillar transistors with bio-mimetic gates canbe used to sense trans-membrane cell potentials. We describe the fabrication ofetched mesa-FETS with aspect ratios exceeding 40:1 (height:width). Etchednano-pillars with widths ranging from 50nm to 1um are then processed usingfocused-ion-beam milling and deposition to define source, drain, and gateregions. Gate isolation is achieved by an under-passivated pseudo-Bosch etch inconjunction with a thru-pillar oxidation. The gate contacts are functionalized bydeposition of biomimetic metal stacks. Finally, the nano-FETs are mated withCMOS application specific integrated circuits to serve as the platform for trans-membrane cellular recording. ReferencesReferences [1] M.D. Henry, S. Walavalkar, et al. “Alumina Etch Masks for Fabrication of High-Aspect Ratio SiliconMicropillars and Nanopillars.” Nanotechnology, 2009, Vol. 20, Issue 25. [2] X. Duan, R. Gao, P. Xie, et al.“Intracellular recordings of action potentials by an extracellular nanoscale field-effect transistor.” NatureNanotechnology, 2011, Vol. 7. [3] B.D. Almquist and N.A. Melosh. “Fusion of biomimetic stealth probes into lipidbilayer cores.” PNAS, 2010, Vol. 107, No. 13.

Nano FET:Nano-FET Final Dimensions

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Nano-FET Fabrication:Nano-FET Fabrication Sequence

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ThP4-15 | Dilute Nitride nipi Solar Cells (#62)Naci Balkan , Benjamin Royalluniversity of essex CSEE, Colchester, CO43SQ, Great Britain ContentIn this paper dilute nitride nipi solar cells are modelled and demonstrated. A nipidoping solar is formed by growing a series of horizontal layers with the dopingalternating between n-type and p-type creating the band profile shown on theright of the diagram. The device also has layers of vertical doping periodicallythroughout the device which are used to selectively contact the n and p-typehorizontal layers. When the structure is illuminated electron hole pairs are generated throughout the horizontal layers. If the horizontal layers thicknessesare comparable with the photogenerated minority carrier diffusion lengths theminority carriers diffuse to the n and p-type side respectfully before they canrecombine. Once spatially separated the carriers have a much longer life timeand drift or diffuse to their corresponding selective electrode. Drift diffusionconductivity is used to model the performance of GaInNAs nipi solar cells both asstandalone devices for 1 eV GaInNAs nipi solar cells, and when incorporated intoa tandem solar cell as the 3rd junction in 3 junction series connected tandemsolar cells. Modelling results shows that 1 eV GaInNAs nipi structures couldreach AM1.5G one sun efficiencies as high as 15 % alone and 35 % efficiencywhen incorporated into a GaInP / GaAs / 1eV cell. Prototype GaAs and GaInNAsnipi structure were grown by molecular beam epitaxy and selective contacts wereformed by ion implantation of Si and Mg. Spectral response and I-Vcharacteristics of devices under AM1.5G illumination are reported.

Figure1:(a) AGaInNAs n-i-p-i solar cell with 5 junctions (b) Efficiency versus number of junctions in a nipi structures incorporated into a tandem solar cell.

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ThP4-16 | Sensor based on Coplanar µ-Strips to Measure theElectronics Properties of the Polyethylene Oxide (PEO)Electrospun (#473)Carlos Fuhrhop Research Assistant PPI, Volgershall 1, 21339 Lüneburg, Germany ContentThe aim of our research is the development of a prototype of a Bionanosensor,which can detected the pathogens (virus) in enclosed spaces in real time. Thesensor based on Polymers nanofibers, which act as sensing element. Thereforeis important to investigate the geometrical, mechanical and electrical propertiesof it, in order to understand better its properties for the sensor application. Thesensitivity of the DC electrical properties of various nanowires to moleculesadsorbed on their surfaces also raises the question of whether similar ACconductance changes exist and can be exploited for Biosensor purposes. Thenanofiber is produced by electrospinning method, which is a cost-effective andversatile process to fabricate nanofibers from a wide range of materials at roomtemperature and atmospheric pressure, of which the diameter ranges from tensof nanometers to a few micrometers. The research involved experimental andtheoretical efforts to investigate and understand high frequency electrodynamicresponse properties of nanowires of polymer and conductive polymer. We haveanalysed the electronic properties (the impedance) of the electrospun using acoplanar µ-strip (CPµS) sensor, where the electrospun is the fibers net resultingfrom the electrospinning process. Here we present a model for the sensor basedon the transmission line theory. The electrospun impedance is modeled by aconductance and capacitance in parallel with the transmission line sensor'smodel. The model was simulated with MATLAB and its result was compared withthe experimental data of the CPµS in order to see if the model is a good model ofthe sensor or not. After the validation of the sensor prototype we have measuredthe impedance of the electrospun. First we measure the impedancecharacteristic of the sensor without electrospun and after that the electrospun isdeposited by electrospinning on the surface of the CPµS sensor, the impedancecharacteristic of the system CPµS/ Electrospun was measured. From theexperimental data we have obtained two curves, one for the sensor withoutelectrospun and one for the CPµS/ Electrospun system. We using the differencebetween both curves to calculated the impedance, conductance and thecapacitance of the polymer electrospun. We have found that the the complex ACconductance of the polymer electrospun exhibited a sub-linear power lawdecrease with frequency that is consistent with behavior found in polymer(insulator).

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References[1] F.Musio, et al., High-frequency a.c. investigation of conducting polymer gas sensors. Sensors and actuators B, 23(1995), pp. 223-226. [2] M. Amrani, et al., High-frequency measurements of conducting polymers: development of anew technique for sensing volatile chemicals. Measurement Science and Technology, Volume 6, Issue 10, pp.1500-1507 (1995). [3] C. Fuhrhop et al., Sensoren und Messsysteme 2010. Nürnberg, Germany (18-19.05. 2010).ISBN 978-3-8007-3260-9. [4] S. Ramakrishna; K. Fujihara; W. Teo; T. Lim; Z. Ma. An Introduction to Electrospinningand Nanofibers. World Scientific Publishing Co. Pte. Ltd., Singapore, 2005. [5] J. D. Jackson. (1975) ClassicalElectrodynamics. Second Edition. John Wiley & Sons. [6] A. K. Jonscher. The Universal Dielectric Response. NatureVol. 267, 23 June 1977. [7] B. c. Wadell. (1991) Transmission Line Design Handbook. Artech House. [8] A. A. Talin,L. Hunter, F. Leonard, B. Rokad, Appl. Phys. Lett. 89, 153102 (2006). [9] J. Xiang, W. Lu, Y. Hu, Y. Wu, H. Yan, C.M. Lieber, Nature 441, 489 (2006)

CPS Sensor:Schema of the CPµS sensor model. (right) 3D schema of the sensor with its equivalent circuit model (left).

Electrospinning:Schema of the electrospinning process and CLSM picture of PEO nanofibers.

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ThP4-17 | Novel polymer-coated magnetic nanoparticles forcontrolled delivery of doxorubicin (#520)Abolfazl Akbarzadeh 1,2, Soodabeh Davaran3,4

1Department of Medical Nanotechnology, Faculty of Advanced Medical Science,Tabriz, Iran Department of Medical Nanotechnology, Ashrafi, 1477763581Tehran, Iran2Department of Medicinal Chemistry, Tabriz university of Medical Sciences,Tabriz, Iran Department of Medicinal Chemistry, Daneshgah, 411 Tabriz, Iran3Department of Medical Nanotechnology, Faculty of Advanced Medical Science,Tabriz, Iran Department of Medical Nanotechnology, Ashrafi, 1477763581Tehran, Iran4Department of Medicinal Chemistry, Tabriz university of Medical Sciences,Tabriz, Iran Department of Medicinal Chemistry, Daneshgah, 411 Tabriz, Iran ContentIntroduction: Magnetic nanoparticles (MNPs) are a major class of nano-scalematerials with the potential to revolutionize current clinical diagnostic andtherapeutic techniques. Due to their unique physical properties and ability tofunction at the cellular and molecular level of biological interactions, MNPs arebeing actively investigated as the next generation of magnetic resonanceimaging (MRI) contrast agents and as carriers for targeted drug delivery. Inpresent work poly (N-isopropylacrylamide- methacrylic acid) (PNIPAAm-MAA) -grafted magnetic nanoparticles (MNPs) were synthesized and loaded withdoxorubicin as an anti cancer drug. Materials and method: For synthesis ofPNIPAAm-MAA-coated MNPs, two synthetic steps were used. First, MNPs werecovalently bound with a silane coupling agent, vinyltriethoxysilane (VTES), toproduce a template site for a radical polymerization. NIPAAm and MAA werethen polymerized on the silane-modified MNPs via methylene-bis-acrylamide andammonium persulfate as a cross-linking agent and an initiator, respectively. Theresultant particles were characterized by scanning electron microscopy (SEM),FT-IR, and vibrating sample magnetometry (VSM). The release behavior ofdoxorubicin from the nanoparticles at various pH and different temperaturesbelow and above LCST was also analyzed. Properties of these nanoparticlessuch as size, drug loading efficiency, and drug release kinetics were evaluated invitro for targeted and controlled drug delivery. Results: The resultantnanoparticles with a diameter of 100 nm showed doxorubicin loading efficiency of70%. Drug release study indicates that the PNIPAAm-MMA is a temperature-sensitive polymer, whereby at its LCST the nanoparticles go through the phasechange to collapse and release more drugs. After 200 hours, 60% of the bondedDOX was released at 42°C, whereas at 37°C ~43% was released. saturationmagnetization is found to be 45.5 and 27.3 emu/g for VTES-modified Fe3O4 andpoly(NIPAAm-MAA)-grafted Fe3O4, respectively, less than the pure Fe3O4

nanoparticles (58.9 emu/g). Conclusion: These modified magnetic nanoparticlescould be used for loading and sustained release of doxorubicin under mildconditions.

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References[1]. Abolfazl Akbarzadeh, Davoud Asgari, Nosratollah Zarghami, Rahmati Mohammad, Soodabeh Davaran.Preparation and in-vitro evaluation of doxorubicin-loaded Fe3O4 magnetic nanoparticles modified with biocompatibleco-polymers. International Journal of Nanomedicine. 2012 ,7,511-526, [2]. Gref R, MinamitakeY, Peracchia MT, et al.Biodegradable long circulating polymeric nanosphers. Science.1994; 263:1600–30.

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ThP4-19 | Properties of Si/SiOx quantum well structure onAl2O3/Si substrates for photovoltaic applications (#196)Kwang-Ho Kim 1, Ji-Hoon Kim1, Pyung Woo Jang2, Chi Sup Jung2, KyuSeomoon3

1Research Institute of Photovoltaics, Cheongju University Department ofSemiconductor Engineering, 298 Daeseong-Ro, Cheongju 360-764, KoreaRepublic (South)2Cheongju University Dept. of Laser and Optical Information Engineering, 298Daeseong-ro, Cheongju 360-764, Korea Republic (South)3Cheongju University Dept. of Applied Chemistry, 298 Daeseong-ro, Cheongju360-764, Korea Republic (South) ContentAbstract Si/SiO2 quantum well or superlattice are the promising structures forapplications in optoelectronics, display, and PV applications due to its quantumwell confinement property1. By reducing the dimensions of silicon to much lessthan the free-exciton Bohr radius of about 5 nm, quantum confinement causes itseffective bandgap to increase2, 3. Therefore, silicon quantum wells using thesequantum phenomena could be a good candidate to achieve high performancethird generation silicon solar cells. The SiOx/Si QW structures were fabricated onsubstrates of Al2O3/p-Si (100) by using the successive deposition technique, asquantum confinement device to increase the effective energy bandgap andpassivation effect in Si surface for the 3rd generation photovoltaic applications.For Si QW of Si/SiOx structures we used a combination of e-beam evaporationfor SiOx layers and successive RF sputtering system to achieve conductivesilicon layers. Low-temperature deposited aluminum oxide (Al2O3) thin films weregrown on p-type Si substrates by the remote plasma atomic layer deposition(RPALD) technique. The RPALD technique uses an alternativetrimethylaluminum precursor and oxygen radicals to obtain good interfaceproperties between the insulator and semiconductor for solar cell applications. InSi/SiOx QWs, the thicknesses of Si and SiOx layers were varied between 1 to 5nm, respectively. The roughness of sputter-deposited Si on SiOx was less than 4Å in the thickness of 2 nm. Figure 1 shows the transmission electron microscope(TEM) photograph image of a single SiOx/Si QW structure deposited on Al2O3/Si(100) substrate. The interface of each layer, such as SiOx/Si, Si/Al2O3, and Al2O3/Si (100) are smooth and vivid. Especially, the interface of Al2O3/Si (100) is veryimportant for application to the solar cells operation. By using the SiOx/Si QWstructures on Si surfaces, the lifetime measured by u-PCD technique increasedas a result of passivated surface effects. The electrical properties of the singlequantum well capacitor of SiOx/Si/Al2O3/p-Si (100) structure showed a goodinterface property and sufficient tunneling conduction as shown in the Fig. 2 and3. Acknowledgement: This research was supported by Basic Science ResearchProgram through the National Research Foundation of Korea (NRF) funded bythe Ministry of Education, Science and Technology (2011-0025843).

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References[1] Z.-H. Lu, D. J. Lockwood, and J.-M. Baribeau, "Quantum confinement and light emission in SiO2/Si superlattices",Nature, 378, 258-260 (1995). [2] L. Pavesi and D. J. Lockwood (Eds.), [Silicon photonics], Springer, Berlin, TopicsAppl. Phys. 94, 1-50 (2004). [3] G. Conibeer, M. Green, E.-C. Cho, D. König, Y.-H. Cho, T. Fangsuwannarak, G.Scardera, E. Pink, Y. Huang, T. Puzzer, S. Huang, D. Song, C. Flynn, S. Park, X. Hao and D. Mansfield, "Siliconquantum dot nanostructures for tandem photovoltaic cells ", Thin Solid Films, 516(20), 6748-6756 (2008).

Fig. 1:TEM photograph of a single SiOx/Si/Al2O3 (3nm/2nm/1.5nm) QW structure

Fig. 2 & 3:C-V and I-V curves of the SiOx/Si/Al2O3/p-Si (100) structure

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ThP4-20 | Fabrication of Fe-Al Nanoparticles by SelectiveOxidation of Fe-Al Thin Films (#200)Pyung Woo Jang , Seungchan Shin, Kwang-Ho Kim, Chi Sup Jung, KyuSeomoonCheongju University College of Science and Engineering, 298 Daesung-Ro,Cheongju 360-764, Korea Republic (South) ContentThere are various methods to fabricate nanoparticles. In this paper new methodfor fabricating nanoparticles from thin films is introduced so that the fabricatednanoparticles are fixed on a substrate. It is very well known that when an alloyconsisting of two elements, the oxygen affinity of which is very much different,one element is selectively oxidized in a damped hydrogen atmosphere. Suchselective oxidation was well investigated in a field of high temperature corrosionof super alloys. However, selective oxidation phenomenon of a thin film would bedifferent from that of bulk alloys. To verify this, 10, 20 and 50 nm Fe-5wt.%Alfilms were rf-sputtered on 100 nm SiO2 substrates, for which Si wafers wereoxidized at 1000oC in oxygen atmosphere. The sputtered films were selectivelyoxidized at 900oC for 200 min in a damp hydrogen atmosphere, the dew point ofwhich was 0oC. The oxidized films were analyzed by SEM, TEM, AFM, XRD andVSM. In an early stage of oxidation, the films became cleaved and then changedto particles with increasing time. After oxidation for 200 min, the continuous filmswere changed to particulates on the SiO2 substrate. And the size of the particlesdecreased with decreasing the thickness of the Fe-Al films. However, the particlesize was not uniform. The size of the particles forming after oxidation of 10 nmFe-Al as-sputtered films was from 60 nm to 210 nm. From the fact that therewere not small particles around large particles the large particles were assumedto be grown by Ostwald ripening. In EDS analysis Fe content of the particles wasmuch higher than that of the matrix containing the particles. Also the matrix wasassumed to be γ-Al2O3 from XRD and EDS analysis. As the oxidation timeincreased the resistivity of the oxidized films were increased due to the formationof both Al2O3 film on the surface and particulates. Due to becoming particulate ofthe film, slope of the VSM magnetization loop of the films became lower withincreasing oxidation time. If the film thickness becomes thinner than 10 nm,particles with a size smaller than 10 nm would be formed. This result as well asothers will be discussed in the conference. References[1] Richard E. Grace and Alan U. Seybolt, J. Electrochemical Society, 105(10), 582, 1958

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Fig. 1 :SEM images of 10, 20 and 50 nm Fe-Al films after selective oxidation at 900oC for 200 min.

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ThP4-21 | Study on the surface reflectivity in an early stage ofAl MOCVD for photovoltaic applications (#307)Kyu Seomoon 1, Jongin Lee1, Pyung Woo Jang2, Chi Sup Jung2, Kwang-Ho Kim3

1Cheongju University Applied Chemistry, 298 Daeseong-ro, Cheongju 360-764,Korea Republic (South)2Cheongju University Laser and Optical Information Engineering, 298 Daeseong-ro, Cheongju 360-764, Korea Republic (South)3Cheongju University Semiconductor Engineering, 298 Daeseong-ro, Cheongju360-764, Korea Republic (South) ContentMetal organic chemical vapor deposition (MOCVD) is useful method for an Aldeposition due to its high deposition rate and good step coverage even in thehigh aspect ratio via holes. Unfortunately Al films deposited via MOCVD have aserious problem of void formation so that many approaches are reported toimprove this problem. However this problem isn’t solved yet. In this study anearly stage of the Al film formation of a several tens nm thickness wereinvestigated to elucidate the void formation problem. Al thin films were depositedon TiN/Si(100) substrates via MOCVD using a N-methylpyrrolidine alane (MPA)precursor. To investigate the surface morphology, surface reflectivity variations ofthe Al films were monitored with in-situ optical apparatus consisted of a laser andphotometer . There were very big variations in the surface reflectivity withreaction time, especially in the initial stage of the MOCVD reaction. Typicalvariations of the reflectivity of the film were shown in Fig. 1. The surfacereflectivity decreased with a time for an initial few seconds, but after thenincreased sharply to almost 200% value of the initial reflectivity followed bygradual decrease to a nearly zero reflectivity. It means that there were significantchanges in the surface morphology. Variation patterns of surface reflectivity werechanged with MOCVD reaction conditions, substrate temperatures and reactionpressures. We investigate the surface morphology changes at significant points,e.g. initial, minimum, maximum points, and the middle points of decreasing andincreasing region (A~H in Fig. 2). This study will help to elucidate the initial stageof film formation and make a guide for a proper control of Al MOCVD.

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Fig. 1.:Typical variations of the surface reflectivity of Al films.

Fig. 2.:Significant points in the surface reflectivity pattern.

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ThP4-22 | Two Dimensiomal Ferroelectric Copolymer P(VDF-TrFE) Langmuir monolayer (#342)Chi Sup Jung 1, Pyung Woo Jang1, Hyun Kyu Park1, Kwang-Ho Kim2, KyuSeomoon3

1Cheongju University Laser and Optical Engineering, Daesungro 298, CheongjuKorea Republic (South)2Cheongju University Semiconductor Engineering, Daesungro 298, CheongjuKorea Republic (South)3Cheongju University Applied Chemistry, Daesungro 298, Cheongju KoreaRepublic (South) ContentThe discovery of two dimensional ferroelectric properties in the Langmuir-Blodgett (LB) film of the copolymer of vinylidene fluoride and trifluoroethylene,P(VDF-TrFE) offer the technological opportunity to fabricate the electro-optic (E/O) devices operating in the scale of nm-thickness. If the molecules, both havinghydrophilic polar head groups and hydrophobic nonpolar tails, interact with air atthe air-water interface, the monolayers can be formed on the water surface. Thecopolymer material P(VDF-TrFE) is partly soluble in water and polar solvent.However, this polymer can be dispersed on the water surface to form asufficiently stable monolayer. The meta-stable nature of this polymer isinvestigated with polarization modulation ellipsometry, Brewster anglemicroscopy (BAM), and surface pressure-area isotherm. Surface morphology ofLangmuir monolayer is observed by using Brewster angle microscope (BAM).The figure below shows the typical images of the monolayer films of P(VDF-TrFE) Langmuir film observed at the various molecular density conditions. Theshape of the domain and the evolution of domain structure will be discussed inthis conference.

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Surface Morphology:Typical images of the monolayer films of P(VDF-TrFE) Langmuir film observed at the various moleculardensity conditions

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ThP5-1 | Relaxation Mechanism in the Optical RecombinationProcess of Quantum Dot Ensembles (#282)Daniel Cesar 1, Marcio Teodoro1, Victor Lopez-Richard1, Gilmar E. Marques1,Euclydes Marega Jr.2, Vitaliy Dorogan3, Yu Mazur3, Gregory Salamo3

1Universidade Federal de Sao Carlos Departamento de Fisica, RodoviaWashington Luiz, km 235, Sao Carlos, Sao Paulo, 13565-905, Brazil 2Universidade de Sao Paulo Instituto de Fisica de Sao Carlos, Sao Carlos, SaoPaulo, 13560-970, Brazil 3University of Arkansas Department of Physics, Fayetteville, Arkansas 72701,United States ContentSeveral mechanisms in the optical relaxation process in semiconductorsquantum dots (QDs) may simultaneously occur. In this work we report a study ofdynamic effects detected in the time-resolved emission from InAs QDensembles. To elucidate main effects that take part in carrier relaxation andoptical recombination processes, and explain the behavior of the time decay as afunction of QDs emission energy we perform theoretical calculations that take inaccount strain effects on the electronic structure and carrier-phonon interactionby Fröhlich Hamiltonian. Also, we discuss the effects of occupation of the groundstate in both valence and conduction bands of QDs in the dynamics of thesystem relaxation as well as the nonlinear effects, such as carrier imbalance. Thetheoretical results show that, when the system behaves like an ensemble,collective effects predominate, and different relaxation processes stand out in thesystem, distinguishing it from that one of isolated QDs. Moreover, we point outthat strain effects and initial density of carriers play a crucial hole in the opticaltime decay behavior. By means of theoretical calculations we were able tosatisfactorily explain the behavior of experimental data and the contribution ofdifferent effects on the optical decay characterized by time-resolvedphotoluminescence.

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ThP5-2 | TRANSPORT AND THERMODYNAMICAL PROPERTIESOF QUASI TWO-DIMENSION ELECTRON GAS (#296)A. C. A. Ramos1, Gil de Aquino Farias2, N. S. Almeida 3

1Universidade Federal do Ceará Departamento de Física, Campus Cariri,Juazeiro do Norte, Ceará, 63040-360,, Brazil 2Universidade Federal do Ceará Departamento de Física, Campus do Pici,Fortaleza, Ceará, 60455-760, Brazil 3Universidade do Estado do Rio Grande do Norte Departamento de Física,Campus Central, Mossoró, Rio Grande do Norte, 59610-210, Brazil ContentElectron gas (EG), confined in finite regions has motivated many experimentaland theoretical studies in the last decades. The possibility of manipulating thephysical properties of the constituent particles (often in a reversible manner) isthe main reason for these systems to remain as object of investigation of severalresearch teams around the world for so long. This kind of system can be seen asone where their constituent particles are free to move in two directions and havetheir movement restricted in the third one (the growth direction). Recently, westudied the influence of the size of the confining region which was modeled by asquare well potential of finite width. We obtained that the existence of energiessub-bands (consequence of the finite thickness) produces significant changes inthe transport and thermodynamics properties of the system when the width of thepotential well reaches a critical value. This value is the one that allows thepresence of electrons in the second sub-band and the main consequence is thatthe system lose the two dimensional character [1]. However, it was alsoobserved that the critical thickness can be controlled by the electrical andmagnetic fields acting on the system. The investigation of this dependence is thegoal of this work. We use a linear combination of Landau and square welleigenfunctions to find the energy spectrum/eigenstates for Q2DEG in presenceof an electric and dc tilted magnetic fields. With these results on hands weinvestigate the dependence of the critical value of the thickness of the region onthe intensity of the fields acting on the system, as well as the influence of theterm of the Hamiltonian which couples the in-plane orbital with the motion in thegrowth direction (not considered in previous works). This was done through theanalysis of the results obtained for some thermodynamic properties (chemicalpotential, specific heat and magnetic susceptibility) for several temperatures aswell as through the study of the behavior of the Hall conductivity under the sameconditions. The results allow us to find the conditions for an electron gas tobehavior as a two dimensional system. However, despite the results clearly topoint out the existence of a critical point, above it the system does not behavioras a 3D system and the results suggest that it behaviors as a system with noninteger dimension. [1] A. C. A. Ramos, G. A. Farias and N. S. Almeida, Physica E43, 1878 (2011)

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ThP5-3 | Effects of an intense, high-frequency laser field onbound states in Ga1-xInxNyAs1-y/GaAs double quantum well (#332)Fatih Ungan 1,1, Serpil Sakiroglu2, Esin Kasapoglu1, Ayse Erol3, M. Cetin Arikan3,Huseyin Sari1, Ismail Sökmen2

1Cumhuriyet University Physics, 58140 Sivas, Turkey 2Dokuz Eylül University Physics, 35140 İzmir, Turkey 3İstanbul University Physics, 34459 İstanbul, Turkey ContentWithin the framework of the effective-mass approximation, using a variationalmethod, we have investigated theoretically the effect of an intense, high-frequency laser field on the bound states in a GaxIn1-xNyAs1-y/GaAs doublequantum well for different nitrogen and indium mole concentrations. Ournumerical results show that both intense laser field and N (In)-incorporation intothe GaInNAs have strong influences on carrier localization. We hope that ourresults can stimulate further investigations of the related physics, as well asdevice applications of group-III nitrides.

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ThP5-4 | Theoretical luminescence spectra in p-typesuperlattices based on InGaAsN (#333)Sara C. P. Rodrigues 1, Thiago F. de Oliveira1, Luísa M. R. Scolfaro2, GuilhermeM. Sipahi3, Eronides F. da Silva Jr.4

1Universidade Federal Rural de Pernambuco Departamento de Física, R. DomManuel de Medeiros s/n, Recife, Pernambuco, 52171-900, Brazil 2Texas State University Department of Physics, 601 University Drive, San Marco,Texas 78666, United States3Universidade de São Paulo Instituto de Física de São Carlos, Av. TrabalhadorSão-Carlense, 400, São Carlos, São Paulo, 13566-590, Brazil 4Universidade Federal de Pernambuco Departamento de Física, Av. ProfessorLuiz Freire, s/n, Recife, Pernambuco, 50670-901, Brazil ContentIn the past few years, the dilute nitride system, InGaAsN, is proposed as a goodcandidate for several device applications. InGaAsN is considered a promisingmaterial for laser devices working at 1.3 or 1.5 mm and high-efficiencymultijunction solar cells [1,2]. Incorporation of In and N into GaAs result in astrong redshift of the emission wavelength.However, despite their great potentialfor applications, the understanding of their physical properties is ratherincomplete. In particular, the dominant mechanisms of light emission in thesealloys and their dependence on the nitrogen composition are not wellestablished.Such information is crucial not only for a better understanding of theoptical properties of the nitrogen containing III-V alloys, but also for a bettertechnological control of alloy formation and optimization light emission efficiency.Another point concerns to investigation in p-type doping in InGaAsN. This is ofgreat importance since, for example, can improve the transport in HBT(Heterojunction Bipolar Transistors) devices [3]. In this work we report ontheoretical luminescence spectra calculations for p-doped GaAs/InxGa1-xAs1-yNy

superlattices (SLs) at any temperature. The calculations are performed within thek.p method by solving the full 8 x 8 Kane Hamiltonian, generalized to treatdifferent materials.By varying the acceptor concentration we analyze the effect ofexchange-correlation, which plays an important role in potential profile. In Figure1 we present the self-consistent potential profiles for an unstrained GaAs/InxGa1-

xAs1-yNy SLs with 3% of In and 1,3 % of N.The barrier and well widths are equal to3 nm. The calculations were performed for following acceptor concentrations, NA:(a) 1 x 1018 cm-3, (b) 2 x 1018 cm-3, (c) 4 x 1018 cm-3, (d) 6 x 1018 cm-3. The bandbending of the total potential changes from attractive to repulsive as the NA

increases.This behavior is caused by relative contributions of the Coulomb,VC

(repulsive) and exchange-correlation, VXC (attractive) potentials to the totalpotential of the heterostructure. Consequently, the electronic transitions areaffected as shown in Figure 2, which we observe a redshift in energy until NA=4 x1018 cm-3 and after a blueshift.These findings can be used as a guide for futureexperiments.

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References[1] H-C. Yu et al., Appl. Phys. Express 4, 012103 (2011). [2] A. Hoffmann et. al., Mat. Sci. and Eng. B 93, 55 (2002).[3] T-H Wu et. al., Jap. J. of Appl. Phys 50, 01AD07 (2011).

Figure 1:p-doped unstrained GaAs/InGaAsN SLs with 3% of In and 1.3 % of N. The barrier and well widths areequal to 3 nm and the acceptor concentration was varied.

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Figure 2:Theoretical PL spectra at T= 2 K for the same systems described in Figure 1.

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ThP5-5 | Three-Particle Quantum System in a DisconnectedStructure: Trion X- in Two Vertically Coupled Rings and aCoaxial Wire (#345)Marlon R. Fulla 1, Jairo Marín2, Diego Ospina2

1Instituto Tecnológico Pascual Bravo-IU Electronic and Informatics, Calle 73 No.73A - 226, 6564 Medellín, Colombia 2Universidad Nacional de Colombia Sede Medellín Faculty of Science, Calle 59ANo 63 - 20, 3840 Medellín, Colombia ContentThe rapid progress in semiconductor growth techniques has led to fabrication ofquantum dots with exotic geometries providing more opportunities to developnew opto-electronic devices. Ring-like structures have been a focus of attentionbecause their topology is closely related to intriguing mesoscopic phenomenasuch as the quantum interference effects, Aharonov–Bohm oscillations, quantumHall effects and persistent currents [1]. In recent years, it has been demonstratedthe formation of concentric [2] and vertically coupled quantum rings [3],stimulating several experimental and theoretical investigations about few-particlesystem energy spectra. More recently, the study of one-dimensional systemscompound by a quantum wire with side-coupled ring has become important dueto the great potential offered by these systems for applications in submicrondevices [4]. Motivated by all these experimental facts, in the present work weconsider a three-particle system consisting of one hole restricted to move into aquantum wire that coincides with the symmetry axis of two vertically coupledrings, each one containing one electron. The system is under a uniform magneticfield and the quantum rings considered have different radii. By modifiyinggeometrical parameters such as the ring radii ratio and the interring distance, it isdetermined and analyzed in detail the conditions in which a transition from a gas-like phase to a strongly correlated system (Wigner-type transtition) occurs. References[1] T. Ihn, A. Fuhrer, T. Heinzel, K. Ensslin,W. Wegscheider; and M. Bichler, Physica E 16, 83 (2003) [2] T. Mano, T.Kuroda, S. Sanguinetti, T. Ochiai, T. Tateno, J. Kim, T. Noda, M. Kawabe, K.Sakoda, G. Kido and N. Koguchi,Nanoletters 5, 425 (2005). [3] Z.R. Wasilewski and S.F.Fafard and J.P. McCalrey, J. of Crys. Growth 201/202, 1131(1999) [4] Minchul Lee and C. Bruder, Phys. Rev. B 73, 085315 (2006)

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ThP5-6 | EXCITON BINDING ENERGY OF GA-AS INSYMMETRICAL NARROW NANOTUBE WITH TWO QUANTUMWELL UNDER MAGNETIC FIELD (#347)Jesus Gonzalez 1,2, Jader Gonzalez3, Jose Barba2

1UNIVERSIDAD DEL MAGDALENA Grupo en Teoría de la Materia Condensada,Cra. 32 No 22 - 08, SANTA MARTA, Colombia 2UNIVERSIDAD NACIONAL DE COLOMBIA DEPARTAMENTO DE FISICA,Cra. 45 N° 26-85, BOGOTA, Colombia 3UNIVERSIDAD PONTIFICIA BOLIVARIANA FACULTAD DE INGENIERIA,Autopista Piedecuesta Kilometro 7, BUCARAMANGA, Colombia ContentThe effect of the field on the binding energies of excitons in micro-tubescontaining two GaAs/GaAlAs quantum wells (QWs) in a section of the tube layerwhich has been fabricated and optical properties of the embedded QWs hasbeen studied [1].We analyze the effect of the magnetic field parallel to the axisand different potential shape on the ground-state binding energy of the off-axisdonors in cylindrical nanotubes containing two GaAs/GaAlAs quantum wells(QWs) in a section of the tube layer. We express the wave function as a productof combinations of s and p subband wave functions and an envelope function thatdepends only on the electron–ion separation [2]. By using the variational principlewe derive a differential equation for the envelope function, which we solvenumerically [3,4]. Two peaks in the curves for the dependence of the ground-state binding energies on the donor distance from the axis are presented and it isshown that the increasing the magnetic field increasing the binding energy whilethe impurity is located in the QW1, whereas the opposite occurs when theimpurity is located in the QW2. References[1] Kubota K, Vaccaroa P O, Ohtania N, Hiroseb Y, Hosodab M, Aida T, Physica E 13(2002)313–316. [2] Betancur FJ, Orozco E A, Gonzalez J D and Mikhailov I D, Phys. Stat. Sol., 242 (b), 1833 (2005). [3] F. J. Betancur, I. D.Mikhailov and L. E. Oliveira, J. Appl. Phys. D 31, 3391 (1998). [4] I. D. Mikhailov, F. J. Betancur, R. Escorcia and J.Sierra-Ortega, Phys. Stat. Sol., 234 (b), 590 (2002), Phys. Rev., B67, 156317 (2003).

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ThP5-7 | Energy Structure of an Excitonic System Confined in aQuantum Ring and a Perpendicular Side-Coupled Wire (#349)Marlon R. Fulla 1, Jairo Marín2

1Instituto Tecnológico Pascual Bravo-IU Electronic and Informatics, Calle 73 No.73A - 226, 6564 Medellín, Colombia 2Universidad Nacional de Colombia Sede Medellín Faculty of Science, Calle 59ANo 63 - 20, 3840 Medellín, Colombia ContentThe relevant advances in semiconductor growth technology have made possiblethe fabrication of semiconductor nanostructures with novel geometries, forinstance, ribbons [1], rings [2], wires[3], among others. These nanoscopicsystems provide an interesting scenario to develop new opto-electronic devices,for example the quantum dot lasers [4], photo-detectors [2,4], and one-singletransistors [4]. In recent years, it has been an important object of study, quantumsystems compound by wires with side-coupled rings, in which can be observedinteresting quantum transport phenomena [5] and are excellent candidates todevelop technological devices such as the spin filters [6]. This fact has motivatedus to carry out a theoretical study with the aim of obtaining the energy spectrumof an electron-hole system restricted to move separately in a narrow quantumring and a perpendicular side-coupled wire. Since the hole-electron effectivemass ratio is greater than one, the adiabatic approximation [7] has been used tocalculate the energy as a function of the ring-wire separation, the ring radius andthe magnetic field strength applied parallel to the wire axis. The cases in whichthe electron is confined into the wire while the hole is restricted to move into thering and vice versa are analyzed. References[1] V. Ya Prinz, Physica E 23, 260 (2004) [2] P.M.Petroff, A.Lorke, and A.Imamoglu, Physics Today, (2001) [3] M.U.González, L. González, J.M. Garcıa, Y. González, J.P. Silveira and F. Briones, Microelectronics J. 35, 13 (2004) [4]Z. M. Wang. Self-Assembled Quantum Dots. Springer Science and Business Media, NY. , 2008. [5] Santanu K. Maiti,Physics Letters A 362, 225 (2007) [6] Minchul Lee and C. Bruder, Phys. Rev. B 73, 085315 (2006) [7] M.R.Fulla,F.Rodriguez-Prada, J.H Marín Cadavid, Superlatt. and Microstruct. 49, 252 (2011)

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ThP5-8 | Coherent control of intersubband quantum welltransitions with ultrashort electromagnetic pulses (#360)Emmanuel Paspalakis1, John Boviatsis 2

1University of Patras Materials Science Department, Rio, 26504 Patras, Greece2Technological and Educational Institute of Patras, Megalou Alexandrou 1,26334 Patras, Greece ContentAn important problem in the area of light interaction with intersubband quantumwell transitions is the potential for controlled population transfer between twoquantum well subbands [1-7]. This problem was first studied by Batista and Citrin[1-3] including the many-body effects arising from the macroscopic carrier densityof the system. They showed that the inclusion of the electron-electroninteractions makes the system behave quite differently from an atomic-like two-level system. To succeed high-efficiency population transfer in a two-subband n-type modulation-doped semiconductor quantum well, they used the interactionwith specific chirped electromagnetic fields, i.e. fields with time-dependentfrequency [1-3]. Different approaches for creating high-efficiency intersubbandpopulation transfer were also proposed by our group, where specific formulae forthe electric field amplitude of the electromagnetic field that leads to high-efficiency population transfer were given [4-6]. We also showed that when a two-subband system interacts with a strong chirped electromagnetic pulse, high-efficiency population inversion is possible for several values of the chirp rate andthe electric field amplitude [7]. In this work we study the interaction of ultrashortelectromagnetic pulses with intersubband quantum well transitions, givingemphasis to the case of a few cycle and single cycle electromagnetic pulses. Wenumerically solve the nonlinear density matrix equations [1-3,6,7] for a specificdouble GaAs/AlGaAs quantum well structure, taking into account the ultrashortnature of the applied field, and show that high-efficiency population inversion ispossible for several values of the electric field amplitude. The effects areexplained with an approximate analytical solution of the density matrix equations.The dependence of the efficiency of the population transfer on the electron sheetdensity is also explored. References1. A.A. Batista and D.S. Citrin, Phys. Rev. Lett. 92, 127404 (2004). 2. A.A. Batista, Phys. Rev. B 73, 075305 (2006).3. A.A. Batista and D. S. Citrin, Phys. Rev. B 74, 195318 (2006). 4. E. Paspalakis, M. Tsaousidou, and A.F. Terzis,Phys. Rev. B 73, 125344 (2006). 5. E. Paspalakis, M. Tsaousidou, and A.F. Terzis, J. Appl. Phys. 100, 044312(2006). 6. E. Paspalakis, C. Simserides, S. Baskoutas, and A.F. Terzis, Physica E 40, 1301 (2008). 7. E. Paspalakis,C. Simserides, and A.F. Terzis, J. Appl. Phys. 107, 064306 (2010).

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ThP5-9 | The effect of magnetic field on the impurity bindingenergy of shallow donor impurities in a Ga1-xInxNyAs1-y/GaAsquantum well (#384)Unal Yesilgul 1, Serpil Sakiroglu2, Carlos A. Duque3, Miguel E. Mora-Ramos4,Esin Kasapoglu1, Huseyin Sari1, Ismail Sökmen2

1Cumhuriyet University Physics, 58140 Sivas, Turkey 2Dokuz Eylül University Physics, 35140 İzmir, Turkey 3Universidad de Antioquia Institude de Fisica, AA 1226 Medellin, Colombia 4Morelos State University Faculty of Sciences, CP 62209 Cuernavaca, Mexico ContentUsing a variational approach, we have calculated the impurity positiondependence of the binding energy for a hydrogenic donor impurity in a GaInNAs/GaAs quantum well in the presence of the magnetic field. Our calculations haverevealed the dependence of the impurity binding on the applied magnetic field,and the impurity position.

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ThP5-10 | Theoretical analysis of the bias influence on infraredphoto- and dark currents in Al0,15Ga0,85As/GaAs multiplequantum well structures with Al0,3Ga0,7As tunneling barriers(#448)Anibal T. Bezerra 1,2, Marcos H. Degani3,2, Marcelo Z. Maialle3,2, Paulo F.Farinas1,2, Nelson Studart1,2

1Universidade Federal de São Carlos Departamento de Física, São Carlos, SãoPaulo, 13565-905, Brazil 2Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores- DISSE CNPq, Rio de Janeiro, Brazil 3Universidade Estadual de Campinas Faculdade de Ciências Aplicadas, Limeira,São Paulo, 13484-350, Brazil ContentIn this work, we simulate the photocurrent spectra of a multiple quantum well(MQW) heterostructure under bias, varying from zero to Stark-strong fields. Thephotocurrent was calculated from the time evolution of a quantum state using aSplit-Operator numerical approach. Both localized and continuum eigenstatesand their eigenvalues are also obtained. The structure under analysis has ten5nm GaAs quantum wells (QW), approximately 139meV deep, spaced by 11nmAl0,15Ga0,85As barriers. On top and at the center of each spacing barrier, additional3nm Al0,3Ga0,7As filter barriers are placed, whose heights are nearly the same asthe QW depths. These barriers lead to the modulation of the continuum abovethe spacing barriers, working as resonant tunneling filters and yielding thereduction of the dark current when this MQW is working as an infraredphotodetector (QWIP). We calculate the dark current of this structure using themodel of Levine[1]. This model has been extensively used to describe the darkcurrent of QWIPs because of its simplicity. It considers the effective number ofelectrons which are thermally excited out of the QW into the continuum.We areable to determine the contribution arising from each individual QW to the totaldark current and the efficiency of the tunneling filter. For the calculatedphotocurrent, under the application of both static and dynamic electric fields, weobserve both the Wannier-Stark localization and also different behaviors of thephotocurrent with the increasing of the bias. For low biases the photocurrentshows both negative- and positive-current peaks at different incident-photonfrequencies. As the bias increases, the negative and positive maxima shift theirpositions towards an common value of the frequency, and the superposition ofnegative and positive peaks leads finally to a single positive peak. Within thisfield range, due to this superposition, the overall intensity of the main peakreaches a minimum before increasing with the increasing bias. References[1] Levine, BF. Quantum Well Infrared Photodetectors. J Appl Phys 74; 8 (1993)

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ThP5-12 | A SOLVABLE MODEL OF NON-UNIFORM EXCITONVOLCANO-SHAPED QUANTUM DOT (#467)F. A. Rodriguez Prada , L F García, Ilia Davidovich MikhailovUniversidad Industrial de Santander Escuela de Física, Carrera 27, Calle 9Ciudad Universitaria, Bucaramanga, Colombia ContentThe influence of the no uniformity on the spectral properties of the one- and two-particle quantum rings has been studied previously by using the finite elements[1] and exact diagonalization methods [2]. Exact solutions for a quantum dot withparabolic confinement are usually used as a set of the base functions todiagonalyze the Hamiltonians of few particles in 3D quantum dots with non-uniform shapes [2]. In this work we propose to use other type of the basefunctions for this aim, which correspond to exact solutions of the Schrödingerequation for a heterostructure, whose height increases linearly in the radialdirection and it can vary arbitrarily in the angular direction. In Fig. 1 we show theprofiles of the cross sections through both directions for one example of suchexactly solvable model (dashed lines) and compared them for one example ofthe experimentally manufactured quantum ring (solid lines) from Ref. [3]. Weshow that our exactly solvable model can present a type of reordering andcrossovers of the curves of the energy levels as functions of the strength of theexternal magnetic field, different from those in 1D quantum ring, known asAharonov-Bohm effect, as the profile slope in the radial direction is sufficientlylarge. Also, we analyse the effect of the structural non-uniformity related to thevariable quantum ring thickness, on the low-lying electronic levels. References[1] I. Filikhin, V.M. Suslov, B. Vlahovic, Physica E 33( 2006), pp. 349. [2] V. M. Fomin, V. N. Gladilin, J. T. Devreese,N. A. J. M. Kleemans and P. M. Koenraad, Phys. Rev. B 77 , (2008), pp. 205326 . [3] S. Boonpeng, W. Jevasuwan, S.Suraprapapich, S. Ratanathammaphan, S. Panyakeow, Microelectronic Engineering 86 (2009), pp. 853.

Quantum dots profiles :Surface morphology by AFM (a) of experimentally manufactured nanoring [3] and profiles of theexperimentally manufactured nanoring from Ref. [3] (solid lines) and of the model from this work (dottedlines) in the radial (b) and angular (c) directions

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ThP5-15 | Charge Transfer Magnetoexciton Formation atVertically Coupled Quantum Dots (#502)Willian Gutiérrez Niño 1, Jairo Humberto Marin Cadavid2, Ilia DavidovichMikhailov1

1Universidad Industrial de Santander Santander, 68001000 Bucaramanga,Colombia 2Universidad Nacional de Colombia Antioquia, 05001000 Medellin, Colombia ContentCurrently there is significant interest in the theoretical study vertically alignedsemiconductor quantum dots considered as a possible gate in a quantumprocessor required to entangle different states of an electron-hole pair createdoptically [1]. Different exciton's states can be disentangled by preventing thetunneling through the application of an electric field along the growth direction. Formed in this way one of the disentangled states, charge-transfer exciton hastwo important characteristics: an extremely long lifetime and a permanent dipolemoment [2]. Additionally, its optical properties can be controlled by an externalmagnetic field. In this work we present a theoretical investigation of the chargetransfer excitons properties at vertically coupled semiconductor quantum dots inthe presence of electric and magnetic fields directed along the growth axis. Weshow that wave functions and the low-lying energies of charge transfermagnetoexciton can be analysed approximately in framework a simplified exactlysolvable quasi-two-dimensional model with a parabolic lateral confinement. Starting from this exact solution we analyse the effect of the non-uniformheterostructure morphology and the influence of the external electric field byusing the Galerkin method [3]. The density of energy states is calculated forInAs/GaAs heterostructures as functions of the quantum dots’ dimensions, theseparation between layers and the strength of electric and magnetic field. References[1] D. Bouwmeester, A. Ekert, A. Zeilinger (Eds.): The Physics of Quantum Information (Springer, Berlin, Heidelberg2000) 94, 135;. P. Hawrylak, S. Fafard, Z.R. Wasilewski: Cond. Matter News 7, 16 (1999) 94, 135 [2] RonenRapaport, Gang Chen, and Steven H. Simon, Phys. Rev. B, 73 (2006), pp. 33319-33322 [3] A. W Gutiérrez, J. E.Galván-Moya, and I. D. Mikhailov, Journal of Physics: Conference Series, 210 (2010), pp. 12053-12056

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ThP5-16 | Giant resonant tunneling in multi-barrier structuresunder longitudinal and transverse fields (#510)M. Guadalupe Mendoza-Figueroa 1, Pedro Pereyra1,2

1Universidad Autónoma Metropolitana-Azcapotzalco Ciencias Básicas, Av. S.Pablo 180, 02200 Mexico, Mexico2University of Regensburg Institut für Experimentelle und Angewandte Physik,93040 Regensburg, Germany ContentWe study the effect of external transverse and longitudinal electric fields on thetransport properties (conductance and tunneling time) of multi-barrier structures.We use the transfer matrix method to evaluate multichannel transmissioncoefficients, Landauer conductance and tunneling time. The presence of smalltransverse fields induce important channel mixing that changes the position ofthe isolated resonances and can be used to tune giant resonant tunneling bysimultaneous transmission of resonant propagating modes. In figure 1 theresonant structure experience a red shift of about 30meV when the transverseelectric field changes from 0.004eV/nm to 0.01eV/nm. At the same time thechannel-mixing transmission coefficients T12 and T21 increase and we can see, forexample, that the resonance at 0.12eV moves to 0.09eV where the conductance(in units of e2/h) becomes larger. Similar effects can be seen at higher energiesand for systems with a larger number of propagating modes. We also study thetunneling time for 1D and 2D structures. In figure 2, the tunneling time of a 1Dtwo-barrier system is shown as a function of the longitudinal electric field. As theelectric field increases the tunneling time evolves from a strong resonantbehavior, with quasi-stationary states, to almost monotonic single barriertunneling time.

Figure2.gif:The tunneling time in a 1D two-barrier system as a function of the longitudinal electric field. Increasing thebias, the tunneling time changes from a resonant behavior to a sigle-barrier tunneling time.

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ThP5-17 | Role of topological structure in electronic propertiesof inhomogeneous 3D Möbius rings (#26)Vladimir M. Fomin , Oliver G. SchmidtLeibniz Institute for Solid State and Materials Research (IFW) Dresden Institutefor Integrative Nanosciences (IIN), Helmholtzstraße 20, D-01069 Dresden,Germany ContentAdvancements in fabrication of strain-driven self-assembled systems [1] haveallowed for realisation and study of man-designed topological structures whichdetermine the energy spectrum and other physical properties of charge carriersand photons in such systems. Spooling a single crystalline NbSe3 ribbon on aselenium droplet by surface tension produces a twist leading to formation of aone-sided Möbius strip [2]. The surface curvature affects quantum eigenstates ofsemiconductor 2D Möbius strips [3]. A number of man-made [4] and natural [5]structures with Möbius topology clearly reveal a spatial inhomogeneity of twist. Wetheoretically demonstrate that the inhomogeneity of twist makes observable thegeometry-governed space-dependent metric in semiconductor 3D Möbiusnanostructures. In those structures, the effective inhomogeneity of the spacemetric leads to a change in the electron kinetic energy, which constitutes about10-3 to 10-2 of the electron energy in a conventional ring rolled up from the samesemiconductor film. A change of the space metric in the twisted region leads toan increase of the electron kinetic energy and results in a trend to confine theelectron in the untwisted region. The wave function is expelled from the twistedregion. The magnitude of this expulsion increases when increasing the ratio Lx1/Lx

of the length of the untwisted part of the ring Lx1 to the circumference of the ring Lx.An interplay between the energy reduction (because the electron avoids theregion of a high kinetic energy) and the energy rise (due to the size quantizationin the untwisted region) leads to a continuous transition of the electron groundstate from delocalized (Fig. 1a, at Lx1 = 0), where the untwisted region is small incomparison with the circumference of the ring, to effectively localized (Fig. 1b, atLx1/Lx = 0.2), where the untwisted region becomes sufficiently large. A clearmanifestation of this transition is provided by the Aharonov-Bohm effect in a 3DMöbius ring. It is detectable through observation of persistent currents(magnetization) as a function of the magnetic flux threading inhomogeneousMöbius rings. Quantum states of electrons and holes confined in inhomogeneousMöbius rings reveal the role of the topological structure also through the opticalresponse. Thus, an inhomogeneous twist makes feasible an experimentalobservation of the topology effect on the electronic properties of 3D Möbiusnanostructures. References[1] O. G. Schmidt, N. Schmarje, C. Deneke, C. Müller, and N.-Y. Jin-Phillipp, Adv. Mater. 13, 756-759 (2001). [2] S.Tanda, T. Tsuneta, Y. Okajima, K. Inagaki, K. Yamaya, and N. Hatakenaka, Nature 417, 397-398 (2002). [3] B.Lassen, M. Willatzen, and J. Gravesen, J. Nanoelectron. Optoelectron. 6, 68–75 (2011). [4] W. J. Arora, A. J. Nichol,H. I. Smith, and G. Barbastathis, Appl. Phys. Lett. 88, 053108 (2006). [5] C. V. Jennings, K. J. Rosengren, N. L. Daly,M. Plan, J. Stevens, M. J. Scanlon, C. Waine, D. G. Norman, M. A. Anderson, and D. J. Craik, Biochemistry 44,851-860 (2005).

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Fig. 1.:Wave function of an electron confined to a Möbius ring with homogeneous (a) and inhomogeneous (b)twist. Calculation is performed using Möbius rings rolled up of a semiconductor InAs membrane with sizes62,8nm x 8nm x 2nm.

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ThP5-18 | Tight binding simulation of type-II superlatticeabsorption (#98)Soline Boyer-Richard 1, Cédric Robert1, Lionel Gérard2, Jan-Peter Richters3,Joël Bleuse3, Régis André2, Henri Mariette2, Jacky Even1, Jean-Marc Jancu1

1Université Européenne de Bretagne INSA, FOTON, UMR 8622, 35708 Rennes,France 2Institut Néel, CNRS Nanophysics and semiconductors, 38042 Grenoble, France3CEA/INAC/SP2M Nanophysics and semiconductors, 38054 Grenoble, France ContentA solar cell is typically built onto 3 parts: a light absorber surrounded by a n-typeand a p-type layer to collect the photo-generated charge carriers. In an idealcase, the absorber and n-type layer conduction bands shall be aligned whileforming a barrier for holes. Respectively, the absorber and p-type layer valencebands shall be aligned while forming a barrier for electrons. Such a 3 materialsystem does not exist and we propose here to mimic the absorber by using atype II short-period superlattice (SL) made of two materials with a type-II bandalignment. Bulk CdSe and ZnTe are among the best zinc-blende semiconductorsto this scope because they are almost lattice matched and exhibit a type IIinterface. We have performed tight binding (TB) calculations to design the moresuited CdTe/ZnSe SL configuration that fully maximizes absorption in the solarspectrum. The TB parametrizations for cubic CdSe and ZnTe are calculatedwithin the extended orbital-basis scheme [1] together with those of CdTe andZnSe, which allows for modeling the non-symmetric interfaces. We have used amesh of 1200 points to sample the SL Brillouin zone center and the resultingdiscrete transitions are dressed with a 0.005 eV Gaussian broadening to getsmooth spectral functions. The calculated optical properties of bulk exhibit a verygood agreement with experiment, especially for the dielectric functions. Theelectronic structure of type II SL is very sensitive to the valence band offset(VBO) and in the present case we have considered the ab-initio values of [2]. AsCdTe and ZnSe do not share any common atom, three configurations have beensimulated: CdTe-like or ZnSe-like terminations (symmetric SL) and theCdSe/ZnTe interfaces (non-symmetric SL). To test our tight-binding for II-VIheterostructures, we have calculated the electronic properties of the non-symmetric (CdSe)7/(ZnTe)7 superlattices and found a strong in-plane anisotropyof the optical spectrum, which is consistent with observation [3]. Absorptionthresholds strongly depend on the chemical species at interface (figure 1). CdTeinterfaces allow for a lower absorption threshold due to the very small VBO withZnTe. A comparison with PL measurements on the same SL grown by MBEshows that simulation slightly underestimates the absorption threshold, possiblybecause of the VBO uncertainty (PL peak at 1.63 eV). Nevertheless, thistheoretical study opens new routes towards type II solar cells. References[1] J.M. Jancu, R. Scholz, F. Beltram, and F. Bassani, Physical Review B 57, 6493 (1998). [2] C.G. Van de Walle andJ. Neugebauer, Nature 423, 626-8 (2003). [3] W. Su, M. Ya, Y. Chiu, and Y. Chen, Physical Review B 66, 64-66(2002).

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Absorption spectra:Calculated in-plane absorption of (CdSe)_7/(ZnTe)_7 in 3 interface cases. The absorption peak around1.55 eV on CdTe curve is due to hole interface states.

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ThP5-19 | Optical modes in cylindrical nanostructures (#131)Carlos Trallero-Giner 1, Rolando Pérez-Alvarez2, Dario G. Santiago-Perez3,Leonor Chico4

1Havana University Physics, San Lazaro y L, 10400 Havana, Cuba 2Universidad Autónoma del Estado de Morelos Physics, Ave. Universidad, 62209Cuernavaca, Mexico3Universidad Jose Marti Physics, Ave. de los Martires, 62100 Sancti Spiritus,Cuba 4Instituto de Ciencia de Materiales de Madrid Teoría, 28049 Madrid, Spain ContentA detailed analysis of the polar optical-phonon modes in semiconductornanostructures with cylindrical symmetry is presented, with emphasis on thespatial symmetry of the modes. We report a basis for the solutions space of thisproblem, which can be used in standard quantum wires, dressed quantum wires,or in any other cylindrical structure with an arbitrary number of walls. The basis iscomposed of eight linearly independent solutions. Each solution is a four-component vector, with three components of spatial character and the fourth onecorresponding to the scalar potential of the electric field associated with theoptical mode. The spatial parts of these solutions have been already classified aslongitudinal, i.e., irrotational (rot u=0), or transversal (div u=0), i.e., source-free orsolenoidal [1]. Besides the basis for the solutions, we also give some analyticaland numerical results for core/shell GaAs/GaP quantum wires. We discuss themixing of longitudinal and transversal modes in these core/shell wires; it isremarkable that the only uncoupled modes are those with angular momentumand wave vector equal to zero. The effects of strain on confined LO- and TO-likephonon modes are considered in a simple manner in terms of the Gruneissenparameters and of the tensional states of the constituent materials. In principle,applying Raman and infrared spectroscopy techniques allows for themeasurement of the TO splitting and LO-confined modes, which may be used toextract information on core/shell radius ratio and other relevant information as theGruneissen parameters. The axisymmetric states (i.e., those with zero angularmomentum) have been discussed elsewhere [2]. In this contribution we reportsome preliminary numerical results for the modes of the core-shell GaAs/GaPstructure with non-zero wave vector and angular momentum. It is shown that themain effect of the stress due to the interface is the red-shift or blue shift ofphonon frequencies for the shell or core, respectively. References[1] “Continuum model for long-wavelength optical phonons in cylinders: application to carbon nanotubes”, L. Chicoand R. Pérez-Álvarez, Phys. Rev. B 69, 035419 (2004). [2] "Optical phonons in core/shell nanowires: strain effects",Darío G. Santiago-Pérez, C. Trallero-Giner, R. Pérez-Álvarez, L. Chico, R. Baquero, and G. Marques, submitted.

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ThP5-20 | How effective parameters of elastic superlattice arerelated to phase and group velocity of sound (#149)Lyudmila Gumen 1, Edgar Reyes2, Jesus Arriaga2, Arkadii Krokhin3

1Universidad Popular Autonoma del Estado de Puebla Mathematics, 21 sur 1103Barrio Santiago, 72410 Puebla, Mexico2Universidad Autonoma de Puebla Instituto de Fisica, Av. San Claudio y Blvd. 18Sur, 72570 Puebla, Mexico3University of North Texas Physics, 1155 Union Circle # 311427, Denton, Texas76203, United States ContentSpeed of sound c2 = B/ρ is determined by elastic modulus B and mass density ρof the medium. The same relation is widely used in homogenization theories ofperiodic composites. It is definitely correct in the quasi-static limit (ω→0) whenthe frequency of sound is so low that the dispersion relation is linear, ω = ceff kand the phase and group velocities are equal, cph = cg = ceff [1]. In particular,for elastic superlattice with period d containing two layers of width a and b thequasi-static effective parameters are given by the well-known formulas, d/Beff = a/Ba + b/Bb and dρeff = aρa + bρb ,(1)where Ba,b and ρa,b are the parameters of the layers. At finite frequencies thedispersion relation becomes nonlinear. Then, the effective parameters becomefrequency-dependent and even may be negative, giving rise to metamaterialbehavior. In this case it is not clear whether the ratio Beff /ρeff defines phase orgroup velocity of sound. To clarify this issue we study a superlattice with highacoustic contrast between the constituents, ca >> cb. Due to the high contrast,the wavelength 2πca/ω does not necessary exceed the width a of the "slow"layer even if the homogenization condition kd<<1 for the Bloch vector k issatisfied. For sound propagating along the superlattice axis we obtain that therelation between the effective parameters and the phase and group velocitieshas the following form: cphcg = Beff/ρeff(2)Here the effective bulk modulus is still given by Eq. (1). In agreement with theWood’s law all the details about the microstructure enter through the effectivemass density a b sin(ωa/ca) b ρeff = (— ρa + — ρb) ————– + — cos(ωa/ca).(3) d 2d ωa/ca 2dIn the quasi-static limit Eq. (3) is reduced to Eq. (1). However, in the vicinity ofthe resonance ωa/ca = π the effective mass density exhibit strong frequencydependence.We also discuss a possibility for ρeff to rich negative values at theresonance for bi-and tri-layer systems. These results are equally valid for theeffective parameters and speed of light in dielectric superlattices. References: [1] A. Krokhin, J. Arriaga, L. Gumen, Phys. Rev. Lett. 91, 264302 (1999).

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ThP5-22 | First principles derivation of a position-dependentmass Schrödinger equation. (#221)Raimundo Costa , Murilo Almeida, Gil de Aquino Farias, José AndradeUniversidade Federal do Ceará Departamento de física, Campus do Pici,Fortaleza, Ceará, 60455-760, Brazil ContentA translation operator is introduced to describe the quantum dynamics of aposition-dependent mass particle in a null or constant potential. From thisoperator, we obtain a generalized form of the momentum operator as well as aunique commutation relation for x and pγ . Such a formalism naturally leads to aSchrödinger-like equation that is reminiscent of wave equations typically used tomodel electrons with position-dependent (effective) masses propagating throughabrupt interfaces in semiconductor heterostructures. The distinctive features ofour approach are demonstrated through analytical solutions calculated forparticles under null and constant potentials like infinite wells in one and twodimensions and potential barriers.

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ThP5-23 | Tight-binding calculations of Ga(NAsP)/GaP(N)quantum wells for photonic integration on silicon (#288)Cédric Robert 1,2, Mathieu Perrin1,2, Charles Cornet1,2, Olivier Durand1,2, JackyEven1,2, Jean-Marc Jancu1,2

1Université Européenne de Bretagne, INSA, Rennes, France 2CNRS, UMR 6082 Foton, 20 avenue des Buttes de Coësmes, 35708 Rennes,France ContentThe development of a laser on silicon is one of the main challenges forElectronic-Photonic Integrated Circuits (EPIC)1. Because of the large latticemismatch, the growth on Si of III-V materials classically used for laserapplications such as GaAs or InP faces the issue of high defect densities2. Tobypass this issue, the pseudomorphic approach, consisting in growing a perfectlylattice-matched GaP(N) buffer layer followed by an optically active areaheterostructure, has shown promising results. Recently, the epitaxial growth onSi of the perfectly lattice-matched GaPN0.02 layers has been greatly improved3

allowing for dilute nitride based active areas to efficiently emit light. Among them,quaternary GaNAsP QWs have shown to be reliable in both electrically pumpedlaser on GaP4 (at room temperature) and Si 5(below 150K) substrates. However,the exact band structure and the optical properties of GaNAsP/GaPN have to beknown to optimize the design of the laser structure. Modeling heterostructureswith quaternary dilute nitride alloys is not a trivial problem. Polymorphous modelssuch as empirical pseudopotentials method6 or supercell tight-bindingcalculations7 have described in details both ternary dilute nitride alloys GaAsNand GaPN. However, they have not been used to describe quaternary GaNAsPor heterostructures. In parallel, the commonly used band anticrossing model8,based on the repulsion of the N level with the Γ band of the host material, suffersfrom the lack of biaxial strain effects and lateral valleys consideration. A sp3d5s*sN

tight-binding basis is considered here9. The localized character introduced by theN atom is taken into account by adding a sN orbital to the original sp3d5s* basis10.We found that biaxially strained GaNAsP is rather similar to GaPN than GaAsN;i.e. the conduction band minimum is found to have a strong localized characterwith a predominant contribution of the sN orbital. Material gain is simulated for theGaNxAs0.92-xP0.08/GaP QWs structure of Borck et al.11 in Fig1. Increasing N contentis found to red shift the position of the peak due to the giant band gap bowing.The gain also increases because of the reinforced Γ character of the conductionband minimum. The interaction of various levels placed in the same energyregion (Γ and X levels in the well and barrier, localized states on N atoms) isshown to lead to a Type I QW with a large Γ character and an associated largematerial gain that enable lasing.

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References1 D. Liang and J.E. Bowers, Nature Photon 4, 511 (2010). 2 T. Egawa, Y. Murata, T. Jimbo, and M. Umeno, PhotonicsTechnology Letters, IEEE 9, 872 (1997). 3 K. Momose, H. Yonezu, Y. Fujimoto, Y. Furukawa, Y. Motomura, and K.Aiki, Applied Physics Letters 79, 4151 (2001). 4 N. Hossain, S.J. Sweeney, S. Rogowsky, R. Ostendorf, J. Wagner, S.Liebich, M. Zimprich, K. Volz, B. Kunert, and W. Stolz, Electronics Letters 47, 931 (2011). 5 S. Liebich, M. Zimprich,A. Beyer, C. Lange, D.J. Franzbach, S. Chatterjee, N. Hossain, S.J. Sweeney, K. Volz, B. Kunert, and W. Stolz, Appl.Phys. Lett. 99, 071109 (2011). 6 P.R.C. Kent and A. Zunger, Phys. Rev. B 64, 115208 (2001). 7 E.P. O’Reilly, A.Lindsay, P.J. Klar, A. Polimeni, and M. Capizzi, Semicond. Sci. Technol. 24, 033001 (2009). 8 W. Shan, W.Walukiewicz, J.W. Ager, E.E. Haller, J.F. Geisz, D.J. Friedman, J.M. Olson, and S.R. Kurtz, Phys. Rev. Lett. 82, 1221(1999). 9 C. Robert, M. Perrin, C. Cornet, J. Even, and J.M. Jancu, Applied Physics Letters 100, 111901 (2012). 10 J.-M. Jancu, R. Scholz, F. Beltram, and F. Bassani, Phys. Rev. B 57, 6493 (1998). 11 S. Borck, S. Chatterjee, B. Kunert,K. Volz, W. Stolz, J. Heber, W.W. Rühle, N.C. Gerhardt, and M.R. Hofmann, Appl. Phys. Lett. 89, 031102 (2006).

Fig.1:Material gain for TE polarisation at 300K for a 8nm thick GaNxAs0.92-xP0.08/GaP QW

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ThP5-24 | III-nitrides multiple quantum wells electronicstructures and heterojunctions band alignments calculatedusing local density approximation with self-energy corrections(#468)Lara Kühl Teles1, Marcelo Marques2, Ronaldo R. Pela 1, Mauro Ribeiro Jr.2,3, LuizGuimaraes Ferreira1,4

1Instituto Tecnologico de Aeronautica Departamento de Fisica, Praca MarechalEduardo Gomes, 50, Sao Jose dos Campos, Sao Paulo, 12.228-900, Brazil 2Instituto Tecnologico de Aeronautica Departamento de Microondas eOptoeletronica, Praca Marechal Eduardo Gomes, 50, Sao Jose dos Campos,Sao Paulo, 12.228-900, Brazil 3Centro de Pesquisas Avançadas Wernher von Braun, Avenida Alice de CastroPupo Nogueira Mattosinho, 301, Campinas, Sao Paulo, 13098-392, Brazil 4Universidade de Sao Paulo Intituto de Fisica, Sao Paulo, Sao Paulo,05315-970, Brazil ContentHistorically, the determination of band offsets in semiconducting interfaces hasbeen a fundamental topic in semiconductor devices design and functioning,unfortunately never achieved by theoretical tools with high accuracy for a widerange of compounds. Part of this unsuccess was due to the lack of powerfultheoretical tools that, from first principles, should be as good as to predict theband offsets to be within the typical photoemission experimental error of lessthan 0.1 eV [1,2]. This has been so because, even with powerful computers,there was still lacking computationally cheap treatment to excited states, stillposing issues to the brilliant, most used ab initio tool, the density functional theory(DFT) within the local density approximation (LDA). In addition to this, to achievethose levels of accuracy, atomistic model structures must be large enough togive converged results for the wave functions across the interfaces, thus avoidingmistakes that arise with the inclusion of quantum confinement effects. In thiswork we show our recent results from the calculations of the band alignmentsand structures of a special system, short-period superlattice of (GaN)n/(InN)m,particularly for m=1 (one monolayer of InN), in light of the results of Yoshikawa etal. for high-efficiency III-nitrides solar cell design [3]. As is widely known now, III-nitrides are potentially applicable materials for various photonic devices workingin UV, Visible, IR, and even up to THz regions. We employed a new method,called LDA-1/2, for removing the spurious electron self-interaction energythrough corrections in the atomic pseudo-potentials, and obtain the correctedexcited states energies across the junctions for the multiple quantum well system[4,5]. Our results for bulks and using very large supercells are in excellentagreement with newest experimental data.

399

References[1] International Technology Roadmap for Semiconductors, Technical report(2009),http://www.itrs.net/Links/2009ITRS/2009Chapters 2009Tables/2009 Modeling.pdf. [2] Carlo Lamberti, editor.Characterization of Semiconductor Heterostructures and Nanostructures, Chapters 2 and 12, Elsevier, First edition(2008). [3] A. Yoshikawa, S. B. Che, W. Yamaguchi, H. Saito, X. Q. Wang, Y. Ishitani, and E. S. Hwang. Appl. Phys.Lett. 90, 073101 (2007). [4] L. G. Ferreira, M. Marques and L. K. Teles, Phys. Rev. B 78, 125116 (2008); AIPAdvances 1, 032119 (2011). [5] M. Ribeiro Jr., L. R. C. Fonseca, and L. G. Ferreira, Phys. Rev. B 79, 241312(R)(2009)

Figure 1. :InN layer inside GaN. (a) and (c) atomistic models; (b) XTEM image (InN in dark); (d) Band gaps andoffsets LDA-1/2 results. Top: Conduction and valence interface band edges variations. Bottom: interfaceband gap variation (2.82 eV around InN).

400

ThP5-25 | Quantum Confinement and Electronic Properties ofGaN, ZnO and Si Nanowires (#490)Lara Kühl Teles1, Mauro Ribeiro Jr.3,2, Pedro H. G. Oliveira2, Marcelo Marques2,Ronaldo R. Pela 1, Luiz Guimaraes Ferreira4,1, Juergen Furthmueller5

1Instituto Tecnologico de Aeronautica Departamento de Fisica, Praca MarechalEduardo Gomes, 50, Sao Jose dos Campos, Sao Paulo, 12.228-900, Brazil 2Instituto Tecnologico de Aeronautica Departamento de Microondas eOptoeletronica, Praca Marechal Eduardo Gomes, 50, Sao Jose dos Campos,Sao Paulo, 12.228-900, Brazil 3Centro de Pesquisas Avançadas Wernher von Braun, Avenida Alice de CastroPupo Nogueira Mattosinho, 301, Campinas, Sao Paulo, 13098-392, Brazil 4Universidade de Sao Paulo Intituto de Fisica, Sao Paulo, Sao Paulo,05315-970, Brazil 5Friedrich-Schiller-Universität Jena Institut für Festkörpertheorie und -optik, Max-Wien-Platz 1, D-07743 Jena, Germany ContentAfter the discovery of carbon nanostructures such as nanotubes, their synthesisstill poses challenges like the ability to control geometrical parameters, e.g. thediameter, as well as the costs involved. Nanowires are an extremely attractivealternative to nanotubes, because it is much esasier to control their electricalpropeties and they are semiconducting when the surface is properly passivated.Also, tuning the semiconductors properties using other types of structures likenanometer sized wires (nanowires) (NW) has become an aim for materialsscience in its theoretical branch. Silicon nanowires as well as nanowires builtusing wide band gap (Eg) semiconductors are appealing choices, since theformer provide the ideal interface with the existing Si-based technology, and thelatter are interesting since wide Eg semiconductors have emerged as importantmaterials for the solid state blue and ultra-violet optoelectronics. Therefore,theoretical understanding of NW properties are very desirable, and in mostsituations they can only be made using ab initio methods, which fail drastically indetermining excited states properties and have in density functional theory (DFT)their most used tool. For example, for the bulk phase of ZnO, the standard DFTelectronic structure calculations gives an Eg of about 0.8 eV, far away fromexperimental value of 3.4 eV. Considering such level of error in ZnO electronicproperties, simply the application of standard DFT could lead to the danger ofhasty conclusions. Approaches beyond DFT as GW are desirable, but unfeasibledue to extremely high computational costs involved. Recently, we addressed thisquestion and propose a general form to calculate one-particle excitations insolids, based on Slater transition state, named LDA-1/2 [1]. In this work, weemployed the LDA-1/2 method in order to describe the electronic properties,specially the band gap and the quantum confinement, of ZnO, GaN and Si NWs.We studied the effects of hydrogen-passivated, as well as non-passivatednanowires to a range of diameters. We also analyzed the merits and limitationsof the LDA-1/2 method. In each case the results are compared with othertheoretical results or experimental data, when available.

401

References[1] L. G. Ferreira, M. Marques and L. K. Teles, Phys. Rev. B 78, 125116 (2008).

Figure 1.:(a) Eg values for non-passivated (squares) and H-passivated (triangles) ZnO NWs. Empty (filled) symbolsand solid (dotted) lines represent the LDA (LDA-1/2) cases; (b) LDA and LDA-1/2 Eg absolute values ofconfinement.

402

ThP5-26 | Electronic Band Structure of L-DiphenylalanineNanotube (#494)Tarciso Andrade-Filho 1,2, Wendel Andrade Alves2, Alexandre Reily Rocha2

1Universidade Federal do Pará Faculdade de Física, Fl 17 Qd Especial S/N,Marabá, Pará, Brazil 2Universidade Federal do ABC CCNH, Rua Santa Adélia 166, Santo André, SãoPaulo, Brazil ContentIn this work we calculated the electronic band structure of L-diphenylalaninenanotube, a molecular crystal formed by the suitable packing of six residues of L-diphenylalanine, using the Self-Consistent Charge Density Functional BasedTight-Binding method augmented by Dispersion interaction. The calculations takeinto account also the presence of water molecules confined in the centralhydrophilic channel of the nanotube. In fact, it representes a situation closest tothe one observed in the nature.The electronic band structure of the nanotube is characterized to be a large bandgap and flat bands. The little dispersion in the electronic band structure is relatedto the weak intermolecular interactions between L-diphenylalanine residues. Theconfined solvent under study does not promote a substantial modification in theelectronic band structure of the nanotube.

403

ThP5-27 | Electronic Raman Scattering in Quantum Wells (#498)Alison Arantes, Virgilio Anjos Universidade Federal de Juiz de Fora Physics Department, Rua José LourençoKelmer, s/n - Campus Universitário, Juiz de Fora, MG, 36036-900, Brazil ContentWe present a theory for obtaining the inelastic light scattering cross section,Raman scattering at T : 0K temperature in a quasi-bidimensional electron gasformed by the GaAs-AlGaAs semiconductor heterostructure doped selectively.The electronic structure calculations were based on Density Functional Theorywithin the local density approximation. The calculations for the Raman crosssection were performed in backscattering geometry and the laser energy inresonant regime with the spin-orbit optical gap of GaAs. Using a generalized self-consistent field theory we have investigated the charge density excitationsmechanism and spin density excitations mechanism. The excitations spectrawere calculated varying the width of the well as well as the density of the electrongas. Our results were as follows: 1) the observation of the collapse of the Hartreeterm in the charge density excitation for low densities, observed experimentally;2) the observation of an anomalous cross between charge density and spindensity excitations, due to the exchange-correlation functional. This effect is avalidity test for the adopted parameterizations; 3) the prediction of the existenceof excitations of higher energy, not yet observed experimentally; Finally, wedemonstrate that the formalism developed enables mapping the electronicexcitations in the BCS theory, which describes the normal superconducting state.

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Abstracts – Index of Authors

Aristizabal, E. 217 Bong Kyun, K. 243AArora, A. 334 Bonilla, L. L. 147Arriaga, J. 233, 395 Borges, P. D. 337A. Beaton, D. 253Asano, H. 190 Bougeard, D. 327Abdallah, N. B. 318, 321Aslan, M. 268, 278 Bougerol, C. 227Abe, T. 137Assali, L. V. C. 337 Boviatsis, J. 384Acosta, R. E. 217Atkinson, P. 77, 106 Boyer-Richard, S. 392Adorno de Sousa, A. 206Avalos, O. 132 Brasil, M. J. S. P. 319, 320, Agarwal, A. 48Avansi, W. 329 331, 332Aichele, T. 67

Brehm, M. 39, 41, 255Airey, R. 331Brückner, R. 245BAkahane, K. 55Brunner, K. 227Akalin, E. 348Buerger, D. 325Akbarzadeh, A. 365 Badescu, S. 200Bunyakin, A. 326Akram M., M. 137 Baek, C. 343Buyalo, M. 92Akyuz, S. 348 Baek, C. - K. 346Byon, J. - W. 356Ali, M. 156 Baek, E. 343

Alimi, Y. 301 Bahrami, S. 212CAlmeida, M. 396 Baik, J. M. 356

Almeida, N. S. 376 Bakshaev, I. 92Alvaro, M. 147 Balkan, N. 222, 225, 226, 275, Camacho, A. 98, 195, 252, 338Amand, T. 318, 321 303, 339, 362 Campion, R. 247Amano, H. 31 Balocchi, A. 318, 321 Cândido, L. 341Anda, E. 130 Balocco, C. 301 Cardoso, J. L. 314, 322Anderson da Silva Barba, J. 382 Carrere, H. 318, 321, 339

Pereira, T. 206 Barseghyan, M. G. 213 Carretero, M. 147Ando, K. 324 Bauer, A. 83 Castelano, L. K. 126, 230, 290Andrade Alves, W. 403 Bauer, G. 255 Cechavicius, B. 234Andrade-Filho, T. 403 Bechstedt, F. 194 Cesar, D. 230, 331, 332, 375Andrade, J. 396 Bellei, S. 241 Chandra, R. 48Andre Quivy, A. 269 Benamara, M. 33 Chang, C. - F. 220, 360André, R. 392 Benson, O. 67 Chang, C. - K. 176Andrews, A. M. 198, 261 Benyoucef, M. 67 Chang, Y. C. 96Anjos, V. 404 Berger, C. 192 Chaplik, A. 208Antonov, A. 149 Bernardi, M. I. B. 329 Chaqmaqchee, F. 225, 226Aoki, N. 120, 137, 190 Béron, F. 329 Chatterjee, S. 139, 151, 253Apel, V. 130 Bertness, K. 241 Chaves, A. 196, 206Arantes, A. 404 Bertoni, A. 293 Chen, C. - W. 176Araújo, A. D. 299 Bezerra, A. T. 332, 386 Chen, H. - L. 176Araújo, V. D. 329 Bhattacharyya, J. 77 Chen, J. Z. 96Ardali, S. 339 Binh, P. H. 349 Chen, K. - H. 176Arikan, M. C. 82, 91, 265, 268, Bird, J. P. 120, 137, 190 Chen, L. - C. 176

275, 339, 345, 348, 377 Bleuse, J. 392 Chen, P. 276

405


Chen, T. - M. 162 de Freitas Mendonça, M. 269 Eugenio Marques, G. 33Chen, W. 351 de Godoy, M. P. F. 319, 320 Even, J. 240, 392, 397Cheng, G. - A. 189, 250, 284 de Heer, W. A. 192 Ewers, B. 139Cheng, H. H. 96 de Oliveira, T. F. 378Chernikov, A. 253 de Sousa, J. S. 299 FChi, C. - S. 310 Degani, M. H. 155, 297, 386Chico, L. 394 Deng, J. - H. 189 Facsko, S. 43Chin, Y. - C. 114 Destefani, C. 227 Faist, J. 146Chitta, V. A. 309, 329 Detz, H. 198, 261 Fan, W. - C. 94Choi, B. J. 111 Diego Bernardino Maia, A. 269 Fanyao, Q. 227Choi, C. - J. 36, 73 Dietrich, C. P. 89 Farias, G. D. A. 171, 184, 196,Choi, D. - Y. 346 Dinu, I. V. 119 299, 376, 396Choi, J. R. 111 Dmitriev, D. 70 Farinas, P. F. 386Chou, C. C. 128 Donmez, O. 82, 91, 265, 275 Fasth, C. 288Chuang, C. 162 Doriguetto, A. C. D. 309 Fay, M. W. 247Cipagauta, G. 105 Dorogan, V. 375 Fayad, H. 210Claro, M. 46 Dos Santos Claro, M. 269 Fehrenbacher, M. 77Cleary, J. 200 Dos Santos, L. F. 331 Fei, G. T. 75Comba, B. 345 Drachenko, O. 149 Fernandes, F. 46Comitti, V. S. 307 Droretskiy, S. 149 Ferreira Cesar, D. 33Conceição Fernandes Duan, G. 133 Ferreira, L. G. 399, 401

da Silva, E. 269 Duque, C. A. 207, 213, 214, Ferry, D. K. 137Cornet, C. 240, 397 217, 385 Fiedler, H. 180Córtes, N. 174 Duque, C. M. 207 Fino, N. 338Costa, D. R. 196 Durand, O. 397 Fitch, R. 200Costa, R. 171, 396 Flayac, H. 223Couto Jr., O. 230 E Florez, J. 252Covaci, L. 196 Fomin, V. M. 390Covre, P. 309 E. Ulloa, S. 290 Fonseca, K. M. 105

Eaves, L. 247 Forchel, A. 83D Ecke, R. 182 Franca Santos, M. 104

Eibelhuber, M. 257 Franke, C. 146da Silva Jr., E. F. 337, 378 Eng, L. M. 77 Fröb, H. 245da Silva, E. 46 Entin, M. 164, 165, 166 Fromherz, T. 39, 255da Silva, M. B. E. 307 Erbe, A. 291 Fuhrer, A. 288Dae Ho, Y. 243 Erdogan, E. 283 Fuhrhop, C. 363Daldin Teodoro, M. 33 Ergun, Y. 91 Fujikawa, Y. 324Damtie, F. A. 288 Erol, A. 82, 91, 265, 268, 275, Fukuhara, Y. 259Davaran, S. 365 339, 345, 348, 377 Fukuyama, A. 85Davydov, A. 241 Escorcia-Salas, G. E. 201, 202, Furchi, M. M. 198de Aquino Farias, G. 206 203, 204 Furthmueller, J. 401de Carvalho, H. B. 309, 329 Eto, M. 286

406


G H I

G. Smith, C. 162 Hackl, F. 255 Iankilevitch, A. 327Gadzhiev, I. 92 Hai, G. - Q. 126, 341 Igarashi, M. 79, 237Galeti, H. V. A. 313, 316, Haibo, Y. 178 Iikawa, F. 230

331, 332 Hannewald, K. 194 Ikari, T. 85Galvão Gobato, Y. 313, 316, Harako, S. 197 Ikegami, K. 197

319, 320, 331, 332 Harii, K. 324 Ikonnikov, A. 149Gao, K. 94 Harmand, J. - C. 318, 321 Ishibashi, K. 137García-Díaz, J. M. 203 Helm, M. 43, 77, 149, 151, Ishikawa, H. 49García, L. F. 387 153, 192, 325Gavrilenko, V. 149 Henao, E. 217 JGazi Yalcin, B. 278 Hendrickson, J. 200Geisler, S. 279 Henini, M.313, 316, 319, 320, J. Salamo, G. 33Geißler, S. 327 331, 332 Jacob, R. 77Gérard, L. 392 Hermann, S. 178, 180, 182 Jacopin, G. 241Gessner, T. 180, 182 Hernández-Saldaña, H. 322 Jakomin, R. 297Ghosh, S. 219, 334 Herrera, W. 105 Jancu, J. - M. 240, 392, 397Gibbs, H. 139, 151 Herval, L. K. S. 316, 319, 320 Jang, E. - H. 73Girón, J. 117 Hey, R. 230 Jang, J. - W. 346Goiran, M. 149 Hietschold, M. 101, 178, 180 Jang, P. W. 367, 369, 371, 373Goldoni, G. 293 Hintschich, S. 245 Janiak, F. 83, 93, 239Gómez, G. 132 Hirayama, H. 143 Jeong, Y. - H. 343, 346Gontijo de Oliveira, A. 122 Ho, T. - Y. 310 Jitsui, Y. 358Gonzalez, J. 382 Hochreiner, A. 257 Joachim F., W. 63González, J. 124, 272 Höfling, S. 83 John, R. 120González, J. C. 122 Hong, N. 343 Jonas, F. 120Gordan, O. D. 101, 178 Hopkinson, M. 225, 226 Julien, F. H. 241Gordo, V. O. 313, 316, 319, 320 Horing, N. J. M. 211, 212 Jung, C. S. 367, 369, 371, 373Göttfert, F. 192 Horta-Piñeres, S. 202 Jung, E. - Y. 346Gozu, S. - I. 49 Horton, S. L. 211 Jung, J. 355Grundmann, M. 89 Hosono, K. 306Grydlik, M. 39, 41 Hotei, T. 93

KGuina, M. 82, 222, 265, 348 Hugues, M. 225, 226Gumen, L. 233, 395 Huh, C. 36, 73

K. Puddy, R. 162Gumus, C. 339 Huhn, T. 291Kabiraj, D. 44Gunes, M. 265, 268, 275, 339 Humlícek, J. 255Kajiwara, Y. 324Gupta, A. K. 28Kakuda, M. 259Gutakovsky, A. 34Kalchmair, S. 261Gutiérrez Niño, W. 205, 388Kalincev, D. 253

407


Kaliteevski, M. 223 Klang, P. 198 Lee, H. 79Kamp, M. 83 Klenovský, P. 255 Lee, H. J. 27Kamyczek, P. 99 Klettke, A. 139, 151 Lee, J. 57, 371Kanjilal, D. 44 Klosek, K. 99 Lee, J. - S. 343, 346Kao, T. H. 128 Knap, W. 149 Lee, M. - T. 126Karlström, O. 288 Knorr, A. 192 Lee, S. W. 57Karpus, V. 234 Kobayashi, T. 197 Lee, U. 343Kartsev, P. 145 Koç, K. 29, 68 Lehmann, D. 101Kasapoglu, E. 82, 377, 385 Koch, M. 139, 253 Leite Alves, H. W. 337Kasjoo, S. R. 301 Koch, S. 139, 151 Lemke, F. 245Katayama, R. 259 Koike, K. 83, 93 Leo, K. 245Kato, M. 197 Kondo, T. 259 Lev, M. 120Kavaliauskas, J. 234 Korpijärvi, V. - M. 222 Li, L. H. 234Kawabata, R. M. 103, 297 Köster, N. 139 Li, M. 295Khalil, H. M. 222 Kozlova, N. 295 Liang, C. - T. 114, 162Khanna, S. P. 234 K?ápek, V. 255 Liebig, A. 182Kharchenko, A. 63 Krenner, H. J. 106 Liedke, B. 43Khatab, A. 319, 320 Krokhin, A. 233, 395 Liedke, M. 43Khiar, A. 257 Kuboya, S. 259 Lilley, G. 198Khitrova, G. 139, 151 Kühl Teles, L. 399, 401 Lin, A. 351Khoshroo, L. R. 63 Kumar, D. 38 Lin, H. - D. 114, 162Kiba, T. 79, 237 Kumar, P. 48, 54, 354 Lin, H. - H. 114Kida, M. 190 Kumar, S. 247 Lin, H. E. 114Kim, B. K. 73 Kumar, V. 38 Lin, J. - C. 114Kim, G. - H. 356 Kunc, J. 331 Lin, T. - T. 143Kim, H. 57, 323 Kunold, A. 318, 321 Lin, W. - C. 310Kim, H. D. 111 Kuo, C. - C. 176 Linfield, E. H. 234Kim, J. 323 Kuwatsuka, H. 49 Liu, H. C. 146Kim, J. - H. 367 Kwak, Y. 356 Liu, R. - B. 218Kim, K. 343 Kyritsis, G. 263 Liu, Y. - L. 176Kim, K. - H. 367, 369, 371, 373 Liu, Z. 295Kim, N. 323 Lo, F. - Y. 310LKim, S. 343 Lo, S. - T. 114, 162Kim, S. - H. 73, 220 Lopes-Oliveira, V. 33, 319Ladrón de Guevara, M. L. 132Kim, S. H. 51 Lopez-Richard, V. 33, 187, 227,Lagarde, D. 339Kim, S. J. 51 230, 290, 375Lai, Y. - H. 109Kim, T. - Y. 36 López-Richard, V. 331, 332Lai, Y. - S. 176Kim, W. 355 Lorenz, M. 89Lange, M. 89Kim, Y. 291, 355 Lu, X. 253Lastovkin, A. 149Kim, Y. J. 27 Lustoza De Souza, P. 103Lausecker, E. 255Kira, M. 139 Lyssenko, V. 245Lavenus, P. 241Kirakosyan, A. A. 213 Lyu, H. - K. 355Lee, C. H. 250

408

Micha, D. N. 297 Neves, P. P. 309MMieko Abe, N. 269 Nguyen, C. T. 349Mihailov, N. 149 Nikiforov, A. 34Maamache, M. 111Mikhailov, I. D. 201, 202, 203, Nishimura, T. 250Madureira, J. R. 155

204, 205, 387, 388 Nóbrega, J. A. 313Magarill, L. 166, 208Mil'shtein, S. 266 Nourmohammadi, A. 65Mahapatra, S. 227Milekhin, A. 70 Nozaki, Y. 306Mahmoodi, A. 158, 160Miranda, G. L. 214 Nutku, F. 91, 268Mahmoodian, M. 165Mischok, A. 245Maia, A. 46Miserev, D. 164 OMaialle, M. Z. 155, 386Misiewicz, J. 93, 239Makarovsky, O. 247, 295Mittendorff, M. 192Malachias, A. 33 O'shea, K. 81Mityagin, Y. 145Malic, E. 192 Ochiai, Y. 120, 137, 190Miyamoto, K. 137Manjarres-Garcia, R. 201 Ogawa, M. 185Mizuno, S. 215Manjarres-García, R. 204 Oh, H. S. 27Mizushima, Y. 237Manjarres-Torres, J. 204 Ohkane, T. 197Moldoveanu, V. 119Mann, S. 295 Ohmi, Y. 185Momox, E. 303Marega Jr., E. 33, 375 Ohtani, N. 358Mora-Ramos, M. E. 207, 213,Maremyanin, K. 149 Ojeda, J. 123, 281

214, 217, 385Margapoti, E. 227 Okur, M. 303Morais Feu, W. H. 103Marie, X. 318, 321, 339, 349 Okur, S. 345Motyka, M. 83, 93, 239Mariette, H. 392 Oliveira, P. H. G. 401Mozume, T. 49Marin Cadavid, J. H. 205, 388 Omatsu, T. 137Muecklich, A. 43, 325Marín, J. 381, 383 Onabe, K. 259Mueller, T. 198Marques, G. E. 187, 227, 230, Orellana, P. 123, 130, 132, 174Mukherjee, A. 219 290, 313, 316, 319, 320, Orlita, M. 149, 192, 313, 331Mukherjee, S. 128, 129 331, 332, 375 Ospina, D. 381Müller, S. 178Marques, M. 399, 401 Ou, X. 43Murayama, A. 79, 237Massa Fernandes, F. 269 Özugur Uysal, B. 58, 61Myoung-Gu, K. 120Mathias Ribeiro, G. 122Myung-Oh, K. 243Matinaga, F. M. 307 P

Matsuoka, T. 259NMatsushita, T. 259 Pa, P. 71

Matthes, L. 194 Pacheco, M. 123, 130, 174, 272Maude, D. K. 313, 331 Nagashio, K. 250 Paek, J. 31Mazur, Y. 33, 375 Nakaji, K. 79 Paek, J. - H. 85Mazzucato, S. 222 Nakanishi, T. 190 Pal, A. K. 129Mendoza-Figueroa, M. G. 389 Nakayama, H. 324 Pamplona Pires, M. 103Mendoza, J. 203 Nasir, A. 247 Park, B. - J. 73Menéndez-Proupin, E. 227 Nazarov, Y. 286 Park, H. 355Mesquita, A. 309, 329 Nedzinskas, R. 234 Park, H. K. 373


409

Park, R. - M. 36 Rebello Sousa Dias, M. 290 Samuelson, L. 288Park, S. 343 Reily Rocha, A. 403 Samukawa, S. 79, 237Paspalakis, E. 384 Reinhardt, C. 245 Sandoval-Santana, J. C. 318Passaro, A. 269 Reininger, P. 261 Santiago-Perez, D. G. 394Patane, A. 295 Reithmaier, J. P. 67 Santos, P. 230Patanè, A. 247 Renucci, P. 349 Sarcan, F. 82, 265Pavlovic, G. 223 Restrepo, R. L. 213 Sari, H. 82, 377, 385Pchelyakov, O. 34 Reszka, A. 99 Saxena, N. 44Pedesseau, L. 240 Rey-González, R. R. 105, Schaff, W. 275Peeters, F. 184, 196 281, 357 Schäffler, F. 39, 41, 255Pela, R. R. 399, 401 Reyes, E. 395 Scheer, E. 291Penello, G. M. 297 Ribeiro Jr., M. 399, 401 Schell, A. W. 67Pereira, M. 184 Ribeiro Viana Junior, E. 122 Scherer, A. 220, 360Pereyra, P. 87, 279, 389 Richters, J. - P. 392 Schmidt, H. 325Pérez-Alvarez, R. 394 Rigutti, L. 241 Schmidt, J. 153Perrin, M. 397 Rim, T. 343 Schmidt, O. 276Picinin, A. 290 Rino, J. P. 290 Schmidt, O. G. 77, 101, 106,Pires, M. P. 297 Robert, C. 240, 392, 397 247, 390Pirota, K. R. 329 Rodrigues, S. C. P. 378 Schmidt, W. 103Placzek-Popko, E. 99 Rodrigues, W. 103 Schneider, H. 77, 146, 151, Pong, W. - F. 310 Rodriguez Prada, F. A. 387 153, 192Porras-Montenegro, N. 117 Rodriguez, R. D. 101, 178 Schönhöbel, A. 117Portnoi, E. 92 Rojas Bonilla, J. D. 357 Schrenk, W. 198, 261Pospischil, A. 198 Rojas-Cuervo, A. M. 357 Schuh, D. 327Potemski, M. 192 Roman-Taboada, P. E. 318 Schülein, F. J. R. 106Prucnal, S. 43, 94 Romero-Serrano, M. 321 Schulz, S. E. 178, 180, 182Puustinen, J. 82, 222, 265, 348 Rosales, L. 123, 124, 174, 272 Schulze, S. 182

Royall, B. 222, 362 Schwarzl, T. 257Royo Valls, M. 293 Scolfaro, L. M. R. 337, 378QRuiz, G. 195 Seidel, F. 101Ryczko, K. 83, 93, 239 Seifert, G. 283Quivy, A. 46Ryu, H. 36 Sek, G. 83, 93, 239

Seomoon, K. 367, 369, 371, 373R Shabat, M. 210, 236S

Shakfa, M. K. 253R. Connolly, M. 162 Shalimov, A. 325Sadeghi, M. 319R. Fulla, M. 381, 383 Sham, L. J. 218Sagong, H. - C. 346R. Johnson, S. 253 Sharma, P. 38Saitoh, E. 324Rajagopal, A. 220, 360 Shelykh, I. 223Sakiroglu, S. 377, 385Ramirez, H. 252, 338 Sheremet, E. 70, 101, 178Sakri, A. 240Ramos, A. C. A. 376 Shin, S. 369Salamo, G. 375Rastelli, A. 77, 106, 247, 276 Shivaprasad, S. M. 54, 354


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Sierra-Ortega, J. 201, 202, Teixeira Rabelo, J. N. 341 Vinck-Posada, H. 105203, 204 Telenkov, M. 145 Vitlina, R. 208

Silva, F. W. N. 299 Teodoro, M. 313, 375 von Ribbeck, H. - G. 77Simanjuntak, H. P. 87 Tepehan, F. Z. 29, 58, 61, 68Singh, A. K. 301 Tepehan, G. G. 29, 68 WSingh, F. 48 Teppe, F. 149Sipahi, G. M. 378 Teys, S. 34 Wacker, A. 288Skorupa, W. 43, 94 Thurmer, D. J. 101 Wagner, M. 151Soares de Sousa, J. 206 Tiedje, T. 253 Walavalkar, S. 360Soares Guimaraes, P. S. 103, Timofeev, V. 34 Walker, D. 200

104 Tiras, E. 339 Walther, M. 146Soares Vieira, G. 269 Tiwary, S. K. 28 Wang, B. - Y. 310Sobanska, M. 99 Toader, M. 178, 180 Wang, J. 218Sobolev, M. 92 Tolea, M. 119 Wang, S. 319Sohn, C. - W. 346 Toriumi, A. 250 Wang, S. - W. 114Sökmen, I. 377, 385 Toropov, A. 70 Wang, W. 135Song, A. 156, 301 Trallero-Giner, C. 187, 394 Wee, A. 351Souma, S. 185 Tsai, B. H. 96 Weiss, D. 279, 327Souza, P. L. 297 Tsai, C. - J. 310 Winnerl, S. 77, 153, 192Souza, T. E. 309 Tsutsui, K. 306 Winzer, T. 192Spirin, K. 149 Tsvetkov, D. 241 Witzan, M. 257Spisak, B. 282 Turyanska, L. 295 Wixforth, A. 106Springholz, G. 257 Wolf, J. 291Sprinkle, M. 192 U Wo?oszyn, M. 282Statkuté, G. 52 Woo, S. 355Stehr, D. 151, 153 Uchida, K. - I. 324 Worschech, L. 227Steiner, H. 255 Ulloa, J. M. 225 Woscholski, R. 139Strasser, G. 198, 261 Ungan, F. 82, 377 Wu, K. Y. 96Studart, N. 297, 386 Ünlü, H. 211, 212 Wu, S. - L. 284Su, F. 133 Unterrainer, K. 198 Wu, T. 351Suárez-Forero, D. G. 105 Urich, A. 198Suemitsu, M. 36 Utz, M. 327 XSuzuki, A. 85

V Xavier, L. 184TXiao, S. 120

Valusis, G. 234 Xiao, Y. M. 75, 141, 172Takahashi, R. 324 Vasco, J. P. 103, 104 Xu, W. 75, 133, 135, 141, 167,Tanatar, B. 119 Vasilchenko, A. 326 169, 172Taylor, D. 313, 316, 332 Villegas-Lelovsky, L. 187Tchernycheva, M. 241 Vinck Posada, H. 104Teich, M. 151, 153


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Zhao, D. 250Y ZZhao, X. 197Zheng, R. - T. 284Yaguchi, H. 259 Zadiranov, Y. 92Zholudev, M. 149Yamaguchi, M. 31, 85 Zahn, D. R. T. 70, 101, 178Zhou, S. 43, 94, 325Yamamoto, N. 55 Zakhidov, A. 245Zhu, B. - F. 218Yang, H. D. 128, 129 Zakhleniuk, N. 263, 303Zielony, E. 99Yang, Z. P. 96 Zallo, E. 106Zogg, H. 257Yano, M. 93 Zanchi, B. 266Zuerbig, V. 67Yeon, K. H. 111 Zapata-Herrera, M. 98Zytkiewicz, Z. 99Yeryukov, N. 70 Zapata, A. 217

Yesilgul, U. 385 Zederbauer, T. 261Yokoyama, T. 286, 306 Zhang, J. 276Yoon, Y. 120 Zhang, L. 301Yoshino, T. 324 Zhang, S. 135, 167, 169, 172Yu, C. - C. 176 Zhang, T. 284, 349Yuji Tanaka, R. 269 Zhang, W. 325Yun, H. 57 Zhang, Y. 75, 141, 172

Zhao, C. 135, 167


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