1. some things you might be interested in knowing about Graphene

2. All Natural Object/Materials Are 3D
quasi-2D
width
length
height 3D
quasi-1D
quasi-0D

3. Peierls; Landau; Mermin-Wagner; …
NO Bottom-Up Approach
400 carbon atoms at 2000 K
growth
means
temperature
violent
vibrations
in 2D
Fasolino (Nijmegen)
growth of macroscopic 2D objects is strictly forbidden
Peierls; Landau; Mermin-Wagner; …
(only nm-scale flat crystals possible to grow in isolation)

4. No Bottom-Up for 2D Crystals
largest known
flat hydrocarbon:
222atoms/37rings
(Klaus Müllen 2002)
graphene:
least stable configuration
for <24,000 atoms (Don Brenner 2002)
above this number (~20 nm), scrolls are most stable

5. ONE-ATOM-THICK OBJECTS, HUGE MACRO-MACROMOLECULES?
(not only graphene)

6. one atomic plane from a bulk crystal
Top-Down Approach?
just extract
one atomic plane from a bulk crystal

7. isolating individual atomic planes
starting point
in <<2004
suggested in print
Nature Mater 2007
epitaxial
growth
MANY MANY
DIFFERENT
EPITAXIAL SYSTEMS
including graphitic layers
Grant 1970 (on Ru)
Bommel 1975 (SiC)
McConville 1986 (on Ni)
Land 1992 (on Pt)
Nagashima 1993 (on TiC)
Forbeaux 1998 (SiC)
de Heer 2004 (SiC)
… …
let us remove
the substrate
chemically,
like SiN or C membranes
monolayer
is a part of the 3D crystal
GOAL: NOT EPITAXIAL LAYERS
but rather
ISOLATED ATOMIC PLANES

8. Poor Man Approach
3D LAYERED MATERIAL
extract individual
atomic planes

9. split into increasingly thinner “pancakes”
start with graphite
need strong in-plane bonds
Also: Kurtz 1990; Ebbesen 1995; Ohashi 1997
Ruoff 1999; Kim 2005; McEuen 2005
split into increasingly
thinner “pancakes”
SEM: down to
~ layers
1 mm
until we found
a single layer
called GRAPHENE
one atomic plane deposited on Si wafer
Manchester, Science 2004; PNAS 2005

10. extracting atomic planes en masse
SPLIT INTO
ATOMIC PLANES
ANY LAYERED MATERIAL
WHEN YOU KNOW THAT
ISOLATED ATOMIC PLANES CAN EXIST

11. INTERCALATED GRAPHITE
Splitting Graphite into Graphene
15 min centrifugation
Manchester, Nanolett ’08
Coleman et al, Nature Nano ’08
relevant literature:
INTERCALATED GRAPHITE
TEM observations
of ultra-thin graphite
from Ruess 1948 to
Boehm 1962 to Horiuchi 2004
graphene oxide paper
Brodie 1859
Kohlschutter 1918
few hours
sonication
in organic
solvent
(chloroform,
DMF, etc)
TEM
100 nm
RENAISSANCE
starting with graphene oxide:
Ruoff, Nature 2006
also, Kern’s, Kaner’s groups

12. CHEMICAL EXTRACTION chemically extract epitaxially grown atomic planes
S. Seo (Samsung 2010)
Kong ‘09
chemically remove the substrate
FIRST DEMONSTRATED
Kong et al, Nanolett 2009 on Ni
Hong, Ahn et al, Nature 2009 on Ni
Ruoff et al, Science 2009 on Cu
as suggested, Nature Mat 2007
graphene-on-Si wafers
uniform; no multilayer regions;
some cracks;  >5,000 cm2/Vs

13. EXTRACTION ONTO SAME SUBSTRATE
atomic planes decouple during cooling and/or intercalated
Mallet et al 2007
special case:
SiC as an insulator
RELATIVELY WEAK INTERACTION
WITH THE GROWTH SUBSTRATE
de Heer 2004; Rotenberg 2006; Seyller 2008
DECOUPLED FURTHER BY PASSIVATION
Starke 2010; Yakimova 2010

14. Many Other 2D Materials Possible
2D boron nitride in AFM
1m
0Å 8Å Å
2D NbSe2 in AFM
50 m
also,
2,3,4… layers
NOT ONLY
NATURALLY
LAYERED
MATERIALS!
THINK OF
EPITAXY!
1 m
2D Bi2Sr2CaCu2Ox in SEM
2D MoS2 in optics
1 m
Manchester, PNAS ’05

15. MATERIALS OF A NEW KIND: ONE ATOM THICK
MESSAGE TO TAKE AWAY
MATERIALS OF A NEW KIND:
ONE ATOM THICK
atomic planes of graphite and other materials
were KNOWN before as constituents of 3D systems
now we can ISOLATE, STUDY and USE them
- and importantly - they are worth of!

16. what is so special
about graphene?

17. GRAPHENE’S SUPERLATIVES
thinnest imaginable material
largest surface-to-weight ratio (~2,700 m2 per gram)
strongest material ‘ever measured’
stiffest known material (stiffer than diamond)
most stretchable crystal (up to 20% elastically)
record thermal conductivity (outperforming diamond)
highest current density at room T (106 times of copper)
highest intrinsic mobility (100 times more than in Si)
conducts electricity in the limit of no electrons
lightest charge carriers (zero rest mass)
longest mean free path at room T (micron range)
completely impermeable (even He atoms cannot squeeze through)

18. EXCEPTIONAL
ELECTRONIC
QUALITY & TUNABILITY

19. AMBIPOLAR ELECTRIC FIELD EFFECT
Manchester, Science 2004
SiO2 Si
graphene
CONTROL ELECTRONIC PROPERTIES
homogenous electric doping
from ~108 to ~1014 cm-2
ASTONISHING ELECTRONIC QUALITY
-100
-50
100 50
gate voltage (V)
resistivity (k) 2 4 6
ballistic transport
on submicron scale
under ambient conditions
holes
~1013 cm-2
electrons
~1013 cm-2
weak e-ph scattering
POSSIBLE ROOM-T MOBILITY
above 200,000 cm2/V·s
Manchester, PRL 2008
Fuhrer’s group, Nature Nano 2008
carrier mobility at 300K
routinely: ~15,000 cm2/V·s

20. CURRENT STATUS graphene on atomically flat boron nitride  BN
10 um BN
Si wafer
graphene
Hall bar  2 6 1 3
room-T mobility
> 50,000 cm2/V·s
also, Columbia group, arxiv 2010

21. CURRENT STATUS suspended graphene low-T mobilities few million cm2/V·s
2-terminal suspended devices:
first reported by Andrei, Kim & Yacoby
2 m
2 K
low-T mobilities
few million cm2/V·s
SdH oscillations start ~50G
level degeneracy lifted ~ 500G
Manchester, unpublished

22. UNIQUE
ELECTRONIC
STRUCTURE
Wallace 1947

23. massless massive Dirac fermions chiral fermions monolayer graphene
bilayer graphene
McClure 1958
McCann & Falko 2006

24. Finding Electronic Structure
B (T)
0.6
0.4
xx (k)
Vg = -60V 4 12 8
10K
Manchester, Science ’04 & Nature ‘05 1 25
100 50
xx (1/k)
12T
Vg (V) 75
80K
140K
20K
degeneracy f =4
two spins & two valleys
Vg (V)
100
-50 50
-100
xx (k) 4 6 2
n =4B/φ0
ωcτ =const 8T 4K 1
 (a.u.)
150
T (K)
+10V
+90V

25. Finding Electronic Structure
mass of charge carriers strongly
depends on concentration S ky kx
E=pvF
mc/m0 -3 -6 6
n (1012 cm-2) 3
0.02
0.04
0.06
vF = 1.0·106 m/s 5%
ZERO REST MASS:
effective mass
E = mcvF2
BF =(ħ/2πe)S and mc =(ħ2/2π)∂S/∂E
experimental dependences
BF ~ n and mc ~ n1/2
necessitates S ~ E(k)2 or E ~k
in agreement with theory:
Wallace 1947, McClure 1958, Semenoff 1984

26. massive & massless Dirac fermions
half-integer QHE
relativistic analogue of integer QHE
“anomalous” QHE
n (1012 cm-2) -2 -4 4 2 5 10
1.5
-1.5
-2.5
-3.5
-0.5
2.5
3.5
0.5
12T
xx (k)
xy (4e2/h)
xy (4e2/h)
xx (k)
n (1012 cm-2) -2 -4 4 2 6 1 -1 -3 3
12T 4K
Manchester, Nature ’05; Columbia, Nature ’05
Manchester+Lancaster, Nature Phys ’06

27. robust quantum Hall phenomena
zero LL directly
in the density of states
room-temperature QHE
250K
150K
100K
200K
B =16 T -1 1
0.4
0.6
quantum capacitance
gate voltage
(V)
30K
gate voltage (V)
xx (k) -6 2 4
-60
-30 60 30
xy (e2/h) 10 20 -4 -2
30T
300K
Manchester+Columbia, Science ‘07
Manchester, PRL 2010

28. NEW PHYSICS ACCESS TO RELATIVISTIC-LIKE PHYSICS
IN CONDENSED MATTER EXPERIMENT

29. EXAMPLE #1:
Klein Tunnelling

30. Klein Tunnelling Klein 1929 Katsnelson + Manchester 2006
Falko et al 2006
Gorbachev et al, Nanolett ’08
Stander et al, PRL ’09
Young et al, Nature Phys ‘09

31. conductivity “without” charge carriers EXAMPLE #2:
Manchester, Nature ’05

32. Minimum Quantum Conductivity
ρmax
-80
-40 80 40
Vg (V)
ρ (k) 2 4 6
10K
E =0
zero-gap
semiconductor
no localization
in the peak
down to 30mK
and
for million-range
mobilities

33. Minimum Quantum Conductivity
“quantized” conductivity
NOT conductance
(~e2/h per spin and valley)
data from 2007
min (4e2/h) 1
1/
 (cm2/Vs)
12,000
4,000
8,000 2
annealing
recent samples
with million mobility
one electron per sample makes it a metal
Fradkin 1986; Lee 1993; Ludwig 1994; Morita 1997; Ziegler 1998 …
Peres 2005; Gusynin 2005; Katsnelson 2006; Tworzydlo 2006; Cserti 2006; Ostrovsky 2006 …

34. Minimum “Mott” Conductivity
Mott’s argument:
not the case
of other materials
NO LOCALIZATION
AG & Allan MacDonald, Phys. Today 2007

35. fine structure constant
EXAMPLE #3:
visualization of
fine structure constant
Manchester, Science 2008

36. GRAPHENE OPTICS one-atom-thick single crystal visible by naked eye
Manchester, Science ’08
100 µm
bilayer
graphene
air
white light transmittance (%) 98
100 96 50 25
distance (m)
one-atom-thick single crystal
visible by naked eye

37. GRAPHENE OPTICS e2 c  = coupling of light with
100
bilayer
graphene
air
white light transmittance (%) 98
100 96 50 25
distance (m)
2.3%
e2 c
 =
G (e2/2h)
 (nm)
1.5
0.5
1.0
600
700
500
light transmittance (%) 90
theory of 2D
Dirac fermions:
Gusynin ‘06
Kuzmenko ‘08 80
1.5
2.0
2.5
3.0
E (eV)
coupling of light with
relativistic-like charges
should be described by
coupling constant 
a.k.a. fine structure constant
one-atom-thick
single crystal
visible by naked eye

38. relativistic fall on superheavy nuclei EXAMPLE #4:
Shytov et al PRL 2007
Castro Neto et al PRL 2007
…..

40. Atomic Physics Z Z supercritical regime Positron emission
slides courtesy
of Antonio Castro Neto

41. Graphene Physics
“artificial atoms”
easily become
overcritical Z

42. Manchester, Science ’09 & arxiv 2010
EXAMPLE #5:
New Graphene-Based
Materials
Manchester, Science ’09 & arxiv 2010

43. Graphene as GigaMolecule
both surfaces
available
(bi-surface chemistry;
chemistry of individual
gigamolecules)
chemical reactions:
C + X => CX

44. FluoroGraphene make large graphene membranes
expose them from BOTH side
to atomic F (using XeF2)
Raman, optics, TEM, XPS, transport

45. FluoroGraphene make large CHANGES IN RAMAN graphene membranes
expose them from BOTH side
to atomic F (using XeF2)
CHANGES IN RAMAN
1600
3000
1200
2600 2
intensity (a.u.) 4 6
Raman shift (cm-1)
pristine D G 2D
fluorographene
30h
20h
XPS & EDX:
C:F  1 9h 1h
Raman, optics, TEM, XPS, transport

46. Stoichiometric Derivative
fluorographene (“2D Teflon” )
optical gap of 3.0eV
chemical reactions:
C + F => (CF)
wide-gap semiconductor
chemically & thermally stable
mechanically strong
exposure to
atomic fluorine, using XeF2

47. CORNUCOPIA OF NEW SCIENCE
MESSAGE TO TAKE AWAY
CORNUCOPIA OF NEW SCIENCE
not only electronic properties
but optical, mechanical, chemical, etc.

48. INDUSTRIAL SCALE PRODUCTION
WHAT ABOUT
APPLICATIONS?
INDUSTRIAL SCALE PRODUCTION
IS A DONE DEAL

49. only realistic examples
APPLICATION
OVERVIEW
only realistic examples

50. EXAMPLE #1:
ON SALE ALREADY

51. best possible TEM support conductive ink production within
last 3 years:
from none to >100 ton pa
“multilayer graphene”
AVAILABLE from
Graphene Industries; Graphene Research;
Graphene Supermarket

52. CARBON NANOTUBES OR GRAPHITE
ANY APPLICATION
WHERE
CARBON NANOTUBES OR GRAPHITE
ARE CONSIDERED
can be MUCH BETTER
both sides bind
monolayers
cannot cleave
any further

53. EXAMPLE #2:
THz Transistors

54. THz TRANSISTORS ballistic transport high velocity great electrostatics
scales to nm sizes
Y. Lin (IBM)
3 μm
SiO2 Si
graphene
ultra high-f
analogue transistors;
HEMT design
Manchester, Science ’04
-100
-50
100 50
Vg (V)
 (k) 2 4 6
US military programs:
500 GHz transistors
on sale by 2013 years
demonstrated (IBM & HRL 2009):
~100 GHz even for low  & long channels

55. EXAMPLE #3:
OPTOELECTRONICS

56. ULTRAFAST PHOTODETECTORS
ballistic transport
of photo-generated carriers
in built-in electric field e h
n-type
doping
metal
p-type
graphene
Avouris, Nature Photo 2010
DESIRABLE TO IMPROVE:
only ~2.3% conversion
because a monolayer is transparent

57. Graphene instead of ITO
EXAMPLE #4:
Graphene instead of ITO

58. flexible: strain >15%
SUBSTITUTE FOR ITO
Manchester, NanoLett 2008
conductive:  <100/□
transparent: ~97%
flexible: strain >15%
chemically inert
transparent
polymer film
WORKING 10 m
LCD-GRAPHENE PIXEL
liquid crystal
active layer
active
layer
graphene
electrodes

59. SUBSTITUTE FOR ITO conductive:  <100/□ transparent: ~97%
flexible: strain >15%
chemically inert
transparent
polymer film
 ~40/□
transparency ~90%
 ~5,000 cm2/Vs
Hong, Nature Nano 2010
reasonably cheap: ~$50/m2
liquid crystal
active layer
graphene
electrodes
REMAINING PROBLEM:
stability of doping

60. Samsung Graphene Road Map: first products in 2012
TOUCH & OTHER SCREENS
bendable & wearable
transparent
polymer film
liquid crystal
active layer
graphene
electrodes
Samsung Graphene Road Map: first products in 2012

61. Little Considered Applications
EXAMPLE #5:
Little Considered Applications

62. ILLUMINATING WALL PAPER
perfect match for organic LED
transparent
polymer film
polymer
LED
graphene
electrodes
both anode & cathode
Robinson, ACS Nano 2010

63. STRAIN SENSORS graphene: cheaper & larger strains
SKKU + Samsung, NanoLett 2010
~$10 each
global market
~$60 billion
graphene:
cheaper & larger strains
compatible with existing tech
Samsung Graphene Road Map:
production in 2014

64. INCREDIBLY RAPID PROGRESS:
MESSAGE TO TAKE AWAY
INCREDIBLY RAPID PROGRESS:
AFTER ONLY 5 YEARS
APPLICATIONS
NO LONGER
A WISHFUL THINKING
only their extent remains unclear