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Some things you might be interested in knowing about Graphene.

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Presentation on theme: "Some things you might be interested in knowing about Graphene."— Presentation transcript:

1 some things you might be interested in knowing about Graphene

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

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

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

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

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

7 let us remove the substrate chemically, like SiN or C membranes GOAL: NOT EPITAXIAL LAYERS GOAL: NOT EPITAXIAL LAYERS but rather ISOLATED ATOMIC PLANES monolayer is a part of the 3D crystal epitaxialgrowth 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) … isolating individual atomic planes starting point in <<2004 suggested in print Nature Mater 2007

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

9 start with graphite need strong in-plane bonds Also: Kurtz 1990; Ebbesen 1995 ; Ohashi 1997 Ruoff 1999; Kim 2005 ; McEuen 2005 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 ANY LAYERED MATERIAL SPLIT INTO ATOMIC PLANES extracting atomic planes en masse WHEN YOU KNOW THAT ISOLATED ATOMIC PLANES CAN EXIST

11 Splitting Graphite into Graphene few hours sonication in organic solvent(chloroform, DMF, etc) 15 min centrifugation TEM 100 nm 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 RENAISSANCE starting with graphene oxide : Ruoff, Nature 2006 also, Kerns, Kaners groups

12 chemically remove the substrate as suggested, Nature Mat 2007 CHEMICAL EXTRACTION Kong 09 FIRST DEMONSTRATED Kong et al, Nanolett 2009 on Ni Hong, Ahn et al, Nature 2009 on Ni Ruoff et al, Science 2009 on Cu chemically extract epitaxially grown atomic planes graphene-on-Si wafers uniform; no multilayer regions; some cracks; >5,000 cm 2 /Vs S. Seo ( Samsung 2010)

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

14 50 m 2D boron nitride in AFM Many Other 2D Materials Possible 2D MoS 2 in optics 1 m 0Å 8Å 23Å 2D NbSe 2 in AFM 1 m 2D Bi 2 Sr 2 CaCu 2 O x in SEM NOT ONLY NATURALLY LAYERED MATERIALS! THINK OF EPITAXY! Manchester, PNAS 05 also, 2,3,4… layers

15 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 GRAPHENES SUPERLATIVES thinnest imaginable material largest surface-to-weight ratio (~2,700 m 2 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 (10 6 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 EXCEPTIONALELECTRONIC QUALITY & TUNABILITY

19 AMBIPOLAR ELECTRIC FIELD EFFECT CONTROL ELECTRONIC PROPERTIES CONTROL ELECTRONIC PROPERTIES gate voltage (V) resistivity (k ) SiO 2 Si graphene Manchester, Science 2004 ASTONISHING ELECTRONIC QUALITY ASTONISHING ELECTRONIC QUALITY carrier mobility at 300K routinely: ~15,000 cm 2 /V·s ballistic transport on submicron scale under ambient conditions weak e-ph scattering POSSIBLE ROOM-T MOBILITY above 200,000 cm 2 /V·s Manchester, PRL 2008 Fuhrers group, Nature Nano 2008 electrons ~10 13 cm -2 holes homogenous electric doping from ~10 8 to ~10 14 cm -2

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

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

22 UNIQUEELECTRONICSTRUCTURE Wallace 1947

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

24 xx (1/k ) 12T V g (V) K 140K 20K 1 0 (a.u.) 1500 T (K) +10V +90V V g (V) xx ( k ) n =4B/φ 0 ω c τ =const 8T 4K B (T) xx (k ) V g = -60V K degeneracy f =4 two spins & two valleys Finding Electronic Structure Manchester, Science 04 & Nature 05

25 B F =(ħ/2πe)S and m c =(ħ 2 /2π)S/E experimental dependences B F ~ n and m c ~ n 1/2 necessitates S ~ E(k) 2 or E ~k mass of charge carriers strongly depends on concentration mc/m0mc/m n (10 12 cm -2 ) S kyky kxkx E=pv F v F = 1.0·10 6 m/s 5% ZERO REST MASS: effective mass E = m c v F 2 Finding Electronic Structure in agreement with theory: Wallace 1947, McClure 1958, Semenoff 1984

26 n (10 12 cm -2 ) T xx (k ) xy (4e 2 /h) half-integer QHE relativistic analogue of integer QHE Manchester, Nature 05; Columbia, Nature 05 anomalous QHE xy (4e 2 /h) xx (k ) n (10 12 cm -2 ) T 4K massive & massless Dirac fermions Manchester+Lancaster, Nature Phys 06

27 robust quantum Hall phenomena gate voltage (V) xx (k ) xy (e 2 /h) T 300K Manchester+Columbia, Science 07 zero LL directly in the density of states 250K 150K 100K 200K B =16 T quantum capacitance gate voltage (V) 30K room-temperature QHE Manchester, PRL 2010

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

29 EXAMPLE #1: Klein Tunnelling

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

31 EXAMPLE #2: conductivitywithout charge carriers Manchester, Nature 05

32 no localization in the peak down to 30mK and for million-range mobilities ρ max V g (V) ρ (k ) K E =0 zero-gap semiconductor Minimum Quantum Conductivity

33 quantized conductivity NOT conductance (~ e 2 / h per spin and valley) one electron per sample makes it a metal data from 2007 min (4e 2 /h) 1 1/ (cm 2 /Vs) 0 12,000 4,000 8, recent samples with million mobility Fradkin 1986; Lee 1993; Ludwig 1994; Morita 1997; Ziegler 1998 … Peres 2005; Gusynin 2005; Katsnelson 2006; Tworzydlo 2006; Cserti 2006; Ostrovsky 2006 … annealing

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

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

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

37 coupling of light with relativistic-like charges should be described by coupling constant coupling constant a.k.a. fine structure constant GRAPHENE OPTICS GRAPHENE OPTICS E (eV) light transmittance (%) G ( e 2 /2h) (nm) % e 2 e 2 c = = theory of 2D Dirac fermions: Gusynin 06 Kuzmenko 08 one-atom-thick single crystal visible by naked eye bilayer graphene air white light transmittance (%) distance ( m)

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

39

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

41 artificial atoms easily become overcritical Z Graphene Physics

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

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

44 FluoroGraphene FluoroGraphene make large graphene membranes expose them from BOTH side to atomic F (using XeF 2 ) Raman, optics, TEM, XPS, transport

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

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

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

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

49 APPLICATIONOVERVIEW only realistic examples

50 EXAMPLE #1: ON SALE ALREADY

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

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

55 EXAMPLE #3: OPTOELECTRONICS

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

57 EXAMPLE #4: Graphene instead of ITO

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

59 graphene electrodes transparent polymer film SUBSTITUTE FOR ITO liquid crystal active layer ~40 / transparency ~90% ~5,000 cm 2 /Vs Hong, Nature Nano 2010 reasonably cheap: ~$50/m 2 conductive: <100 / transparent: ~97% flexible: strain >15% chemically inert REMAINING PROBLEM: stability of doping

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

61 EXAMPLE #5: Little Considered Applications

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

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

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


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