Dvojrozmerne materialy:
ako lepiaca paska sposobila revoluciu
vo fyzike
Jaroslav Fabian
University of Regensburg
Veda v Centre, Bratislava 28.5.2015
Regensburg, Bayern
Universitt Regensburg
Arbeitsgruppe Prof. Fabian
Grafen:
od lepiacej pasky k
relativistickej fyzike
Grafen
Grafit (tuha)
Historia tuhy
1564 objavene lozisko v Borrowdale, Anglicko (cierne olovo, plumbago)
1779 chemik Carl W Scheele: je to forma uhlika
1789 geolog Abraham G. Werner: volajme to grafit, grecky graphein ()
= pisat
1795 chemik Nicolas-Jacques Cont: zmiesajme grafit, il (clay), a vodu = tuha
Uhlikova ZOO
? diamond
graphite
Carbon nanotube
Buckyball, C60
Nobel Prize in Chemistry 1996
Curl, Kroto, Smalley
Is there more?
Ako spravi objav easy way (a dosta Nobelovu cenu)
SiO2 substrate
Scotch tape
Tesa
graphite
Grafenovska revolucia
Nobel Prize 2010
Andre Geim Konstantin Novoselov
Mozu vobec 2-rozmerne materialy
existovat? Peirls, R.E, Bemerkungen ber Umwandlungs
temperature, Helv. Phys. Acta 7, 81-83 (1934).
Landau,L.D and Lifshitz, Statistical Physics (Pergamon, Oxford 1980).
Nekonecny 2-rozmerny krystal nemoze existovat v trojrozmernom
svete pri nenulovej teplote
Ale:
konecny krystal
substrat
zvlnenie (rippling)
Grafen na substrate
1.4
atomy uhlika
baza
Ako tenky je grafen?
1 = 0.000 000 000 1 m = 0.000 000 1 mm
Ako tenky je papier?
5 cm, 500 ks 5 cm : 500 = 0.1 mm
Ako tenky je grafen?
grafen = 0.000 000 1 mm
papier = 0.1 mm = 1 000 000 grafenov
papier grafenove
listy
Ako tenka je stopa ceruzky?
Ako tenka je stopa ceruzky?
priemerna ceruzka spravi ciaru 60 km
meranie courtesy
Ing. Slavomir Fabian
6e
2s2 1s2 2p2
elektronovy svet grafenu
atom uhlika
vazby
pevnost: 3 elektrony na atom
elektricke, opticke, spinove
vlastnosti
elektronovy oblak: 1 elektron na atom
Jemna relativita
= +
,
= +
=
=
Normalna castica Castica s nulovou hmotnostou
hybnost rychlost svetla 300 mil m/s
Jemna kvantova mechanika
= 2
elektron
gulicka
vlna
De Broglie
Schrdinger
Normalne vodice
energia
1
4
hybnost
1
2
elektron-vlna
Normalne vodice
kov
polovodic
Energeticka medzera
Grafene: exoticky vodic
Polokov
Dirakove spektrum,
Elektrony bez hmotnosti, neutrina
rychlost:
v = 1 000 000 m/s = c/300
energia
1
2
Skumame grafen:
elektricke a magneticke pole,
svetlo, deformacia
Napatie na hradle
Kims group Nature 438, 201-204 (2005)
Skumame grafen:
el. polom riadena vodivost
Kims group Nature 438, 201-204 (2005)
~ || ~ ( +0.5)
Skumame grafen:
magneticke pole
Normalny vodic Grafen
skenovaci tunelovaci mikroskop
(STM) Okno do sveta atomov
Courtesy Tobias Frank
N. Levy et al. Science 2010;329:544-547
Skumame grafen: Deformacia vytvara magneticke pole
nanobubliny
Efektivne
magneticke pole
300 Tesla!!!
Nair at al, Science, 320 (2008)
Kvantova elektrodynamika v grafene
=
= /
Feynman: You might say the "hand of God" wrote that number, and "we
don't know how He pushed his pencil."
JF: He pushed it such as to create graphene!
= . %
Absorpcia svetla
grafenom
Graphene highlights
hustota 0.77 mg/m2
opticka priesvitnost 97,7% vysoka mobilita pri izbovej teplote
vodivost ovladana polom
100 krat silnejsi ako ocel
tepelna vodivost 10 krat lepsia ako medi
uplna nepriepustnost voci plynom
vlastnosti menitelne povrchovymi primesmi
netoxicky, vo vode nerozpustny
moznost vyroby velkych ploch (1 meter)
CVD: chemicke naparovanie
http://www.science.oregonstate.edu/~minote/wiki
Dvojrozmerne materialove ZOO:
Ucime sa kvantovu mechaniku v 2
rozmeroch
graphene germanene,
silicene MoS2 NbSe2
hBN
phosphorene
supravodic
polovodic dielektrikum polokov
Spintronika
Elektrony maju spin: tocia sa
Pauli Bohr
The spintronics revolution
Nobel Prize 2007
Albert Fert Peter Grnberg
small resistance large resistance
10 nm
1947 Nobel Prize in Physics 1956
Bardeen, Brattain, Shockley
The transistor revolution
Ked sa zapnu relativisticke korekcie,
elektrony v grafene ziskaju (malu) hmotnost
Injekcia spinu do grafenu van Wees group,
Electronic spin transport and spin precession in single graphene layers at room temperature,
Nature 448, 571 (2007)
Zahada ultrarychlej spinovej relaxacie v grafene
Pre porovnanie: kremik ma spin-relaxacny cas 10 ns
Zname mechanizmy davaju mikrosekundy !!!
Co maju spolocne adatomy v
grafene a RH120?
orbity
minimesiac
Adatomy v grafene su ako zem,
a elektrony ako minimesiace: orbituju okolo a stracaju spin
Courtesy Martin Gmitra
Resonant spin-flip scattering by local moments
puddles
D. Kochan, M. Gmitra, and J. Fabian, PRL 112, 116602 (2014)
Dekorovany (funkcionalizovany)
grafen
, , ,
Courtesy Martin Gmitra
Najtensi feromagnet?
Courtesy Martin Gmitra
Materialove Lego
Courtesy Martin Gmitra
optospintronics:
graphene on TMC
Courtesy of Martin Gmitra
Graphene Flagship
> 100 EU partners
EU funding 10 years
1 Miliarda euro
Applications
Odsolovanie morskej vody
Mathematics is the language with
which God wrote the Universe
A pisal to grafenovou ceruzkou
(And He wrote it with graphene pencil)
JF