kitp teachers - grafeno
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GRAPHENE:magic of flat carbon
Andre Geim January 14, 2012, KITP Teachers' Conference
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ON THE IMPORTANCE OF CURIOSITY
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“FRIDAY NIGHT EXPERIMENTS”
magnetic water descaler
water in highmagnetic
fields?
ancient magnets:consume a lot of energyrequire extra cryostats
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A BIT OF LEVITY
water in highmagnetic
fields
ever present diamagnetismNOT as negligible as commonly believed 4
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KNOWLEDGE IS FUN
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official name:dwarf hamster
nickname: Tisha
job: levitator
KNOWLEDGE IS FUN
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SCIENCE TO THE MASSES
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PERCEPTION CHANGEeverything and everybody is magnetic;
ever present diamagnetism is NOT negligible
in many textbooks
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HOW COMES THAT GECKO CAN CLIMB WALLS?
“FRIDAY NIGHT EXPERIMENTS”
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sticky feet:geckos climb due to their hairy toes
courtesy of K Autumn
submicron size (!) - standard spatial scale in our work
PNAS 2002
“FRIDAY NIGHT EXPERIMENTS”
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GECKO TAPEproof of concept:
biomimetic dry adhesivebased on “gecko principle”
Geim, Sergey Dubonos, Irina Grigorieva et al Nature Mater 2003
PLACING EMPHASIS
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BRIEF HISTORYOF GRAPHENE
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polishing is dead,long live Scotch tape!
~2.5 cm
2002 PhD project of Da Jiang:make films of graphite
as thin as possible and study
their properties
graphite flakeson cellotape
optical image
THE LEGEND OF SCOTCH TAPE
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AFM
5x5 m2
UNTIL A SINGLE LAYER FOUNDa few
months later
SiO2
Si graphene
make devices
study properties CHANGE PROPERTIES
ASTONISHING ELECTRONIC QUALITY
shoot like bullets-100 -50 0 10050
gate voltage (V)
resis
tivity
(k
)
0
2
4
6
electrons
~1013 cm-2
holes
~1013 cm-2
by voltage from a battery
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N.B. twice rejected by Nature
And after a lot of hard work …
“the paper offers little new insights” - Nature‟s referee16
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WHY
THE INTEREST?
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hei
ght
Everything Has Three Dimensions
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growth of one atom thick materials is STRICTLY forbidden
Nature Hates Low Dimensions
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3D MATERIAL PULL OUT
INDIVIDUAL ATOMIC PLANES
What Can We Do About This?
forbidden in nature does not mean cannot be made artificially
1 mm
seen by a naked eye
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WHAT‟S SO SPECIAL
ABOUT GRAPHENE?
extremely simple structure21
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GRAPHENE‟S SUPERLATIVESthinnest imaginable material
largest surface area (~3,000 m2 per gram)
strongest material „ever measured‟ (theoretical limit)
stiffest known material (stiffer than diamond)
most stretchable & pliable crystal (up to 20% elastically)
record thermal conductivity (outperforming diamond)
highest current density at room T (thousands times of Cu)
completely impermeable (even He atoms cannot squeeze through)
conducts electricity in the limit of no electronslightest charge carriers (zero rest mass)
longest mean free path at room T (micron range)
highest ever mobility (>100 times more than in Si)
… … … … … 22
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NEW SCIENCE
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VERY SPECIAL
ELECTRONS
INSIDE GRAPHENE
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E
ky
kx
“Schrödingerfermions”
“CERN ON A DESK TOP”
metals and
semiconductors
ultra-relativistic particles
neutron starsand
accelerators
pcH ˆˆ
mpH 2/ˆˆ 2
masslessDirac fermions
monolayer graphene
pvHF
ˆˆ
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EXAMPLE #1:
„WHAT CERN CANNOT DO‟
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Klein Tunnelling
classic car
quantum car
graphene car
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EXAMPLE #2:
visualization of fine structure constant
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100 µm
bilayer
gra
phene
air
Manchester, Science ‟08
GRAPHENE OPTICS
one-atom-thick single crystal visible by naked eye
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GRAPHENE OPTICS
one-atom-thicksingle crystal
visible by naked eye
bilayer
gra
phene
air
white lig
ht
tra
nsm
itta
nce
(%)
98
100
96
500 25
distance (m)
2.3%
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coupling of light with relativistic-like chargesshould be described by
coupling constant =1/137a.k.a. fine structure constant
GRAPHENE OPTICS
2.52.0E (eV)
3.01.5lig
ht t
ransm
itta
nce (%
)
100
80
90
G(
e2/2
h)
(nm)
1.5
0.5
1.0
600 700500
2.3%
e2
c =
theory for 2DDirac fermions:
Peres „08
one-atom-thicksingle crystal
visible by naked eye
bilayer
gra
phene
air
white lig
ht
tra
nsm
itta
nce
(%)
98
100
96
500 25
distance (m)
2.3%
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EXAMPLE #3:
fundamental limits of the periodic table
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Z
Z137
1
Z
1371
Z
Positron emission
Atomic Physics
supercritical regime
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1
2
F
Gv
e
“artificial atoms”
easily become overcritical 1
1
G
Z
Z
Graphene Physics
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EXAMPLE #4
Chemistry of Individual Giga-Molecules
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Graphene as GigaMolecule
chemical reactions:C + X => CX
GRAPHENE
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Stoichiometric Derivative
fluorographene (“2D Teflon” )
chemical reactions:C + F => (CF) • chemically & thermally stable
(similar to Teflon)
• as strong as graphene
wide-gap semiconductor
exposure to atomic fluorine, using XeF2 38
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MESSAGE TO TAKE AWAY
CORNUCOPIA OF NEW SCIENCEalready found and
far from being exhausted
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EACH SUPERLATIVE OFFERS
SOMETHING NEW & COMPETITIVE
APPLICATIONS
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graphene as next Si
grapheneapplications
flexible
LCD and LED
wall lightning
ultra-high frequency
electronics;
optoelectronics
composites; 2D Teflon
medical
applications:
drug delivery;
lab-on-chip;
DNA
sequencing
MEMS; various sensors
batteries; supercapacitors
conductive inks; etc.
touch screens & similar41
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MESSAGE TO TAKE AWAY
APPLICATIONS ARE COMING
only their extent remains unclear
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HOW LITTLE WE KNOW
ABOUT THE WORLD AROUND US
MAIN MESSAGE TO TAKE AWAY
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Misha Katsnelson
(Nijmegen)Rahul NairSergey Morozov
(Chernogolovka)
F. SchedinP. Blake
Andrea Ferrari (Cambridge), Paco Guinea (Madrid), Leonid Levitov (MIT), Ernie Hill,
Roman Gorbachev, Alex Kuzmenko (Geneva), Sasha Zhukov, Sasha Grigorenko
Kostya Novoselov
D. EliasL.Ponomarenko A. Castro Neto
(Singapore)
Irina Grigorieva
for graphene reviews, see: Nature Mat „07; RMP ‟09; Science „09
Nuno Peres
(Braga)
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GRAPHENE IS JUST ONE PLANE
OF GRAPHITE
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NOT JUST ULTRA-THIN GRAPHITE
chemicallyless reactive
new materials:graphAne
fluorographeneCHEMISTRY
ELECTRONIC PROPERTIES
masslesscharges
massivechiral
quasiparticles
cleaves easilyMECHANICALPROPERTIES
ultimatestrength
STRONG SCREENINGELECTRIC FIELD GOES THRU47
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WHITHER
GRAPHENE?
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Many Other 2D Materials Possible
1m
0Å 9Å 16Å 23Å
0.5m
2D boron nitride in AFM
2D MoS2 in optics
1 m
1m
0Å 8Å 23Å
2D NbSe2 in AFM
1 m
2D Bi2Sr2CaCu2Ox in SEM
some are insulators,
some are metals,semiconductors,superconductors,
ferromagnets,etc.
Manchester, PNAS 200549
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New Layered Materials on Demand
Graphene Boron-Nitride
NbSe2
MoS2
what theirproperties would be?
mica
some other layered material
movie by Kostya Novoselov50
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EXAMPLE #1
Ultra High Frequency Transistors
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Manchester, Science ’04
-100 -50 0 10050
Vg (V)
(k
)
0
2
4
6
SiO2
Si graphene
2008:>$30M US military programs:
500 GHz transistors on sale by 2013 years
Y. Lin (IBM)
3 μm
ballistic transport
high velocity
great electrostatics
scales to nm sizes
“BALLISTIC” TRANSISTORS
2009: 1OO GHz (IBM & HRL)
2010: 300 GHz (UCLA & Samsung) scaling >1THz
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EXAMPLE #2:
OPTOELECTRONICS
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ULTRAFAST PHOTODETECTORS
eh
n-type dopingmetal
p-type dopingmetal
graphene
Avouris, Nature Photo 2010
ballistic transportof photo-generated carriers
in built-in electric field
transparent metal
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EXAMPLE #3:
Graphene instead of ITO
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WORKING 10 m
LCD-GRAPHENE PIXEL
graphene
electrodes
active
layer
transparent
polymer film
GRAPHENE AS SUBSTITUTE FOR ITOManchester, NanoLett 2008
liquid crystal
active layer
transparent: ~97%
conductive: <10/□
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graphene
electrodes
transparent
polymer film
liquid crystal
active layer
down to 40/□transparency ~90%
~5,000 cm2/VsHong+Ahn, Nature Nano 2010
reasonably cheap: ~$50/m2
GRAPHENE AS SUBSTITUTE FOR ITO
transparent: ~97%
conductive: <10/□
flexible: strain >15%
chemically inert
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TOUCH SCREENS & OTHERSbendable & wearable gadgets
Samsung‟s Graphene Road Map: first consumer products in 2012
Samsung‟s Advert
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