my encounter with nanotechnology
DESCRIPTION
This Presentation is based on our Research work carried out in GNDU Amritsar and DAVIET, Jallandhar. We fabricated Ion track filters; nanowires and some Exotic Patterns for the first time in India using simple Techniques.TRANSCRIPT
My Encounter with NANOTECHNOLOGY
Hardev Singh VIRKVisiting Professor
Sri Guru Granth Sahib World University, Fatehgarh Sahib (Pb.)India
Birth of Nanotechnology“There's Plenty of Room at the Bottom” • On December 29, 1959, Richard P. Feynman
gave the seminal talk at a meeting at Caltech of the American Physical Society. He presented a vision of the precise manipulation of atoms and molecules so as to achieve amazing advances in information technology, mechanical devices, medical devices, and other areas.
Changing Idea into Reality
Eric Drexler of MIT, the Chemist, established the modern field of nanotechnology, with a draft of his seminal Ph.D. thesis in the mid 1980s. His 1991 doctoral thesis at MIT was revised and published as the book "Nanosystems, Molecular Machinery Manufacturing and Computation" (1992), which received the Association of American Publishers award for Best Computer Science Book of 1992.
NANONANO
• “NANO” means “DWARF” in Greek.
• Mathematically nano is ten to the power of minus nine …….. Make sense?
• If the size of your shoe was one nano meter, then a meter would be the distance that you would cover round the world and the sun and back.
• One hydrogen atom is 0.1nm. Five atoms of carbon would occupy a space of about 1 nm wide.
• The nano world comes just after the femto world (10-15 m) of NUCEI and pico world (10-12m) of atoms.
• The nano marks the boundary between the classical and quantum mechanical worlds
• Most of the bulk substances behave differently from nanosize particles. A coin of gold is golden yellow in color, but nanoscale gold is red; bulk gold is inert, but nanogold can be a catalyst for chemical reactions.
• AFM Imaging of ATOMS of GOLD (Au 111)
Atomic Lattice Structure of HOPG in 3D Topography using Atomic Force Microscope
The Incredible Tininess of Nano
Billions of nanometersA two meter tall male istwo billion nanometers.
The pinhead sized dot is a million nm
Biological cells size isThousands of nm
DNA Molecules are about 2.5 nm in width
Hydrogen atom spans 0.1 nm2 Uranium atoms span 1 nm
Why Study Nanomaterials?
• Nanostructures (< 30 nm) have become an exciting research field.
• – New physics phenomena affect physical properties.
• – Unusual quantum effects and structural properties.
• – Promising applications in optics, electronics, thermoelectric, magnetic storage, NEMS (nano-electro-mechanical systems).
Quantum Confinement Effects
– Quantum dots (0-D): confined states, and no freely moving ones
– Nanowires (1-D): particles travel only along the wire direction
– Quantum wells (2-D): confines particles within a thin layer
There is no confinement effect in Bulk materials.Refer to energy distribution.
Routes to Nanotechnology
• Physical, chemical, biological and nature’s self assembly.
• Top-down and bottom-up approaches.• Chemical route to nanotechnology is simpler,
cheaper and allows fabrication at bench top conditions.
• Reverse micelles (microemulsions route) is a versatile method to produce a variety of nanoparticles.
My Route to Nanotechnology
• Ion Track Technology Route using Heavy Ion Beams from GSI, Darmstadt & JINR, Dubna.
• Chemical Route of Reverse micelles, co-precipitation, solvo-thermal, sol-gel and seed growth techniques.
• Quantum dots, nanorods and nanoneedles of Barium Carbonate, Barium Oxalate, Iron Oxalate, Barium hexaferrite, Zinc Oxide, Cadmium Sulphide, Cadmium Oxide and Silver prepared.
UNILAC at GSI Darmstadt (Germany)
Ion Track Technology Ion Track Technology • Ion Track Technology [1] was developed at GSI, Ion Track Technology [1] was developed at GSI,
Darmstadt. Ion Track Filters (ITFs) or Track-Darmstadt. Ion Track Filters (ITFs) or Track-etched membranes became precursors to etched membranes became precursors to development of nanotechnology during 1990s. development of nanotechnology during 1990s. ITFs were prepared by bombardment of thin ITFs were prepared by bombardment of thin polymer foils using heavy ions. One of the first polymer foils using heavy ions. One of the first applications of ITFs was separation of cancer applications of ITFs was separation of cancer blood cells from normal blood by making use of blood cells from normal blood by making use of Nuclepore filters. Author’s group used heavy ion Nuclepore filters. Author’s group used heavy ion beam facility available at GSI UNILAC, Darmstadt beam facility available at GSI UNILAC, Darmstadt during 1980s for Ion Beam Modification of during 1980s for Ion Beam Modification of Materials and to prepare ITFs in our laboratory. Materials and to prepare ITFs in our laboratory.
• [1] R. Spohr: [1] R. Spohr: Ion Tracks and Microtechnology: Principles and Applications Ion Tracks and Microtechnology: Principles and Applications (Vieweg Publications, Weisbaden Germany, 1990(Vieweg Publications, Weisbaden Germany, 1990
Ion Tracks as Structuring Tools Ion Tracks as Structuring Tools
• Ion tracks are created when high-energetic heavy Ion tracks are created when high-energetic heavy ions with energy of about 1 MeV/nucleon (e.g. ions with energy of about 1 MeV/nucleon (e.g. 140 MeV Xe ions) pass through matter. The 140 MeV Xe ions) pass through matter. The extremely high local energy deposition along the extremely high local energy deposition along the path leads to a material transformation within a path leads to a material transformation within a narrow cylinder of about 10 nm width. Unlike in narrow cylinder of about 10 nm width. Unlike in the more conventional lithographic techniques the more conventional lithographic techniques based on ion or electron beam irradiation, a based on ion or electron beam irradiation, a single heavy ion suffices to transform the single heavy ion suffices to transform the material. material.
Latent Pb-Ion Tracks in MicaLatent Pb-Ion Tracks in Mica
Size of Etched ION TracksSize of Etched ION Tracks
Large Etched Ion TracksLarge Etched Ion Tracks
Nanowire Fabrication
Template synthesis using polymer and anodic alumina membranes
Electrochemical deposition Ensures fabrication of electrically continuous
wires since only takes place on conductive surfaces
Applicable to a wide range of materials High pressure injection
Limited to elements and heterogeneously-melting compounds with low melting points
Does not ensure continuous wires Does not work well for diameters < 30-40 nm
Chemical Vapor Deposition (CVD) or VLS technique
Laser assisted techniques
Polymer Template Synthesis of Nanowires
Anodization of aluminum Start with uniform layer of ~1m Al Al serves as the anode, Pt may serve as the
cathode, and 0.3M oxalic acid is the electrolytic solution
Low temperature process (2-50C) 40V is applied Anodization time is a function of sample size and
distance between anode and cathode Key Attributes of the process (per M. Sander)
Pore ordering increases with template thickness – pores are more ordered on bottom of template
Process always results in nearly uniform diameter pore, but not always ordered pore arrangement
Aspect ratios are reduced when process is performed when in contact with substrate
Anodic Alumina Template Preparation
(T. Sands/ HEMI group http://www.mse.berkeley.edu/groups/Sands/HEMI/nanoTE.html)
Anodic alumina (Al2O3) Template
100nm
Si substrate
alumina template
(M. Sander)
Electrolytic CellElectrolytic Cell
Replica of Nanowires
Microtubule Fabrication
Electrochemical Synthesis
• Electrochemistry has been used to fabricate nanowires and heterojunctions of Cu, Cu-Se and Cd-S. The results of our investigations can be exploited for fabrication of nanodevices for application in opto-electronics and nano- electronics. During failure of our Experiments, exotic patterns ( nanoflowers, nanocrystals, nanobuds) were produced under nature’s self assembly.
Template Synthesis of Copper Template Synthesis of Copper NanowiresNanowires
The concept of electro-deposition of metals is The concept of electro-deposition of metals is an electrochemical process. The etched pores of ITFs The etched pores of ITFs used would act as a template. The electrolyte used used would act as a template. The electrolyte used here was CuSO4.5H2O acidic solution. The rate of here was CuSO4.5H2O acidic solution. The rate of deposition of metallic film depends upon: current deposition of metallic film depends upon: current density, inter-electrode distance, cell voltage, density, inter-electrode distance, cell voltage, electrolyte concentration, pH value and temperature electrolyte concentration, pH value and temperature etc. In our case, electrode distance was kept 0.5 cm etc. In our case, electrode distance was kept 0.5 cm and a current of 2mA was applied for 1 hour. The and a current of 2mA was applied for 1 hour. The developed microstructures were scanned under SEM developed microstructures were scanned under SEM for morphological and structural studies.for morphological and structural studies.
AFM image of hexagonal pores of AFM image of hexagonal pores of Anodic Alumina Membrane (AAM)Anodic Alumina Membrane (AAM)
SEM Images of Cu Nanowires using SEM Images of Cu Nanowires using Electrodeposition TechniqueElectrodeposition Technique
Copper Nanowire Bundles in AAMCopper Nanowire Bundles in AAM
Cu Nanowires under Constant CurrentCu Nanowires under Constant Current
Capping Effect of Current VariationCapping Effect of Current Variation
A Garden of Copper NanoflowersA Garden of Copper NanoflowersA Garden of Copper NanoflowersA Garden of Copper Nanoflowers
Copper Nanoflowers grown in Polymer Template (100nm pores)
Copper Lillies grown due to over- Copper Lillies grown due to over- deposition of Copper in AAM deposition of Copper in AAM
Copper Marigold Flower
SEM micrograph of Nanocrystals of SEM micrograph of Nanocrystals of Polycrystalline CopperPolycrystalline Copper
XRD Spectrum of polycrystalline XRD Spectrum of polycrystalline Copper nanocrystalsCopper nanocrystals
Position [°2Theta] (Copper (Cu))
10 20 30 40 50 60 70
Counts
0
20000
40000
60000
36.6
37 [
°]
38.2
83 [
°]
43.4
61 [
°]
45.4
48 [
°]
48.9
20 [
°]
50.5
80 [
°]
54.3
04 [
°]54.9
56 [
°]
64.8
09 [
°]
74.2
99 [
°]
KK1
XRD spectrum of Cu nanowiresXRD spectrum of Cu nanowires
Position [°2Theta] (Copper (Cu))
30 40 50 60 70 80 90
Counts
0
400
1600
Cu polycrystalline
SEM Image of CdS NanowiresSEM Image of CdS Nanowires
HRTEM image showing CdS Nanowire HRTEM image showing CdS Nanowire & Heterojunctions & Heterojunctions
I-V plot of CdS Nanowire arrays I-V plot of CdS Nanowire arrays showing RTD characteristics showing RTD characteristics
SEM image of Cu-Se NanowiresSEM image of Cu-Se Nanowires
Cu-Se nanowires exhibit p-n junction Cu-Se nanowires exhibit p-n junction diode characteristicsdiode characteristics
A Billion Dollar Question …
• What can nanowires offer for semiconductor nanoelectronics?
• Nonlithographic & extremely cost-effective• Reduced phonon scattering: High carrier
mobility but reduced thermal conductance(?) • Tunable electrical/optical properties• Large surface-to-volume ratio: Sensor
sensitivity & memory programming efficiency
Advantages of 1-D Nanowires
• High-quality single-crystal wires with nearly perfect surface
• Scalable nanostructure with precisely controlled critical dimensions
• Best cross-section for surround-gate CMOS• Very cost-effective materials synthesis• High transport low-dimensionality structure• May use as both device and interconnect for
ultra-compact logic (e.g., SRAM)
Nanowire Field-Effect Transistor
• Ambipolar transport• Carrier mobility study• Quantum effect
A single device for numerous applications
Device physics study
Role of Nanowires for Next-Generation Electronics
• The chemical and physical characteristics of nanowires, including composition, size,
electronic and optical properties, can be rationally controlled during synthesis in a predictable manner, thus making these materials attractive building blocks for assembling electronic and optoelectronics nanosystems.
Some Observations & Remarks
• Nanotechnology will be the driving force for next technology revolution.
• Nanowires open door to a wonderland where the next generation electronics would emerge.
• Scope for innovating new synthesis method and complex functional nanostructures.
• New device and interconnect concepts will emerge from horizon, driven by materials synthesis.
Reverse Miceller Route
Nanoparticle Synthesis (ME route)
TEM images of Barium Carbonate Nanorods
TEM images of Iron Oxalate and Barium Oxalate Nanocrystals
TEM image of CdO Quantum Dots
Conversion of Quantum Dots of CdO Conversion of Quantum Dots of CdO to Nanorods using EDA to Nanorods using EDA
CdS Nanocrystals(CTAB+n-butanol)
CdS Nanoneedles(CTAB+n-hexanol)
Ba-M Hexaferrite Crystals (ME)
Ba-M Hexaferrite Crystals (CP)
Ba-hexaferrite ME(after calcination)
Ba-hexaferrite CP(after calcination)
Hysteresis loops of Ba-hexaferrite nanoparticles (CP & ME samples)
SEM image of ZnO Nanocrystals in Ethanol and Nanorod(adding EDA)
TEM image of Ag quantum dots and embedded nano particles
Thank You !!!