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2009.2.12. QMMRC-IPCMS
Synthesis and Applications ofLarge-Scale Graphene Films
Synthesis and Applications ofLarge-Scale Graphene FilmsLarge Scale Graphene Films
Byung Hee Hong
Large Scale Graphene FilmsByung Hee Hong
Department of Chemistry and Sungkyunkwan Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University,
2009.2.12. QMMRC-IPCMS
Toward All-Graphene Electronics Replacing Si-based Semiconductor Technology?
Theory Band-gap EngineeringEdge Control
Q t T tNanoscaleDevices
Quantum TransportTransistors
Large-scaleTransparentFlexible ElectrodesAll graphene Circuitg
DevicesAll graphene Circuit
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BackgroundBackground
Transparent?
No YES
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Non-Flexible Electronics
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Foldable-Stretchable Electronics
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ContentsContentsI. Introduction:
L f CNT- Lessons from CNTs- Importance of Graphene Edges- Necessity of Large-Scale Graphene Films
II. Synthesis and Manipulation of Graphene
III. Large-Scale Synthesis of Graphene Film
IV. IR Characterization of Graphene Edges
V. Summary & Future Directions
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Lessons from CNTsLessons from CNTs
Quantum Electron TransportQuantum Electron Transport
Ballistic TransportBallistic Transport
Molecular ElectrodesMolecular Electrodes
Large Scale SynthesisLarge-Scale Synthesis
Raman SpectroscopyRaman Spectroscopy
Electronic StructuresElectronic Structures
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S E T30 SWNT
Single Electron Transistors
20100
-10-20-30
Vsd
(mV)
continuous oscillations
-20 -15 -10 -5 0 5 10 15 20
30
Vg (V)
0 5 Coulomb potentials in QD are not harmonic!
0.3
0.4
0.5
Vg=30V
Vg=40V
Uni
t)
20
V)
0.1
0.2
Vg=5V
Vg=10V
Vg=20VdI
/dV
(Arb
. U0
-20
Vsd (mV
-0.2 -0.1 0.0 0.1 0.2
0.0
g
ΔVg (V)11.0 11.5 12.0 12.5 13.0
Vg (V)Vg (V)
0.03 0.05 0.06 0.08 0.10 0.12 Go (2e2/h)
Long-range Coulomb oscillation also indicates the high quality of CNTs.
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Quantum InterferencesQuantum InterferencesBallistic Transport
15.0
10.015
10 10.0
5.0
0.0
-5.0Vsd
(mV)
10
5
0
-5Vsd (mV)
6.0 8.0 10.0 12.0 14.0 16.0
-10.0
-15.0
-2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0
-10
-15
Vg (V)Vg (V)
G (2e2/h)
0.4 0.6 0.8 1.0 1.2 1.4 1.6Go (2e2/h)0.4 0.6 0.8 1.0 1.2
Go (2e /h)
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Precise cutting with an oxygen plasma
(A) Precise cutting of SWNTs with an oxygen plasma introduced through an opening in a window of PMMA defined with e-beam lithography.
(B) The results of oxidative opening of the tubes are point-contacts that are functionalized on their ends with carboxylic acids and separated by as little as 2 nm
(C) Scanning electron micrograph of a SWNT with Au on Cr leads that had been cut i b li h h d l using e-beam lithography and oxygen plasma.
(D) AFM image of the gap cut into the SWNT. Inset: height profile of the isolated tubes. The diameter of the SWNT is 1.6 nm, estimated from the height profile.
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Covalent CNT/Graphene-molecule bridgesCovalent CNT/Graphene-molecule bridges
Xuefeng Guo, et al. ãÖie^Öe 311, 356-35č (2006)
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Large Scale SynthesisLarge Scale Synthesis
2mm
Wafer lenčt5 = Max čNT lenčt5s = 10cm
čatalyst: 6rop-dried Fečl3 0.05M solution in water
Furnace lenčt5: 30cm / Growt5 time = ~3 5rs
The maximum length is limited by the size of the substrate and the length of the furnace rather than termination of growth!
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Room-Temperature Ballistic Transport in CNTCNTs
Multi-terminal Device with Pd contactcontact
* Scaling behavior of resistance: ì(L)
Scaling of Resistance and Electron Mean Free Path of Single-Walled Carbon NanotubesM. Purewal, B. H. Hong, A. Ravi, B. Chandra, J. Hone, and P. Kim, Phys. Rev. Lett, 98, 186808 (2007).
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Rise of Graphene
I. Introduction
T di i l f l Di f i i h
Rise of Graphene>300 SCI papers every year since 2006
Two-dimensional gas of massless Dirac fermions in graphene Novoselov, KS; Geim, AK; Morozov, SV, et al.NATURE Volume: 438 Issue: 7065 Pages: 197-200 Published: NOV 10 2005 Times Cited: 1080Times Cited: 1080
Experimental observation of the quantum Hall effect and Berry's phase in Experimental observation of the quantum Hall effect and Berry s phase in graphene Zhang, YB; Tan, YW; Stormer, HL, et al.NATURE Volume: 438 Issue: 7065 Pages: 201-204 Published: NOV 10 2005 gTimes Cited: 970
2009.2.12. QMMRC-IPCMS
Wh G h ?
I. Introduction
Why Graphene ?
High mobility(~10,000 cm2/Vs @RT).Superb heat conductor.Superb heat conductor.High current densities(~108 A/cm2).Transistors based on ribbons.Chemical StabilityMechanical FlexibilityQuantum Electronic TransportQuantum Electronic Transport
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Graphene Electronics I. Introduction
Replacing Si-based Semiconductor Technology?
All G h El t iAll G h El t iAll Graphene ElectronicsAll Graphene Electronics
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All Graphene Electronics I. Introduction
Replacing Si-based Semiconductor Technology?
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Electric Field Effect in Electric Field Effect in Atomically Thin Carbon Film
Science 306, 666 (2004)
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2D gas in Quantum Limit: Conventional Case2D gas in Quantum Limit: Conventional Case
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Quantum Hall Effect in GrapheneQuantum Hall Effect in Graphene
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Graphene Nanoribbons: Confined Dirac Particles
I. Introduction
Graphene Nanoribbons: Confined Dirac Particles
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No structural edge effect
I. Introduction
No structural edge effect in e-beam patterned GNRs
Edge-control is essential for practical applications.g p pp
Characterization Method – FT-IR L S l d dLarge Samples needed.
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Disordered Edge Structures of Graphene
Nature Nanotechnology 3, 3č7-401, (2008)
2009.2.12. QMMRC-IPCMSI. Introduction
Problems
- The scale of graphene layers are too small for practicalapplications.
Large-scale Synthesis and Transferring Methods
- The rough edge structure of graphene blocksthe band-gap engineering of graphene nanostructuresthe band-gap engineering of graphene nanostructures.
Controlling Edge Structures by Wet Chemistryg g y y
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Edge Structures of
I. Introduction
Edge Structures of Graphene
H H H H H H H HHH
zigzag edgeStructural EdgesH H H H
H N
H
H H H
H
HHH
H
H
HH
H
OH hydroxyl
H
H
HH
H
H
N
O
OH
H
H
Hamino
carboxyl
O
H
HH
H
H H
H
H
HH
aceto
alkylH H H
N OO
H
HHH H H H H
a y
nitroChemical Edges
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Higher Charge Density
I. Introduction
Higher Charge DensityOf Graphene Edges
Nano Lett 7, 2295 (2007)
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Band Gap Modulation by I. Introduction
Chemical modification of zigzag
Chemical Modification of Zigzag EdgesChemical modification of zigzag ribbons can break the spin degeneracy, resulting in the onset of a semiconducting-metal transition a semiconducting metal transition, while it doesn't affect much for armchair edge modification.
Phys. Rev. B 77, 165427 (2008) , arXiv:0711.1700
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II. Graphene Synthesis/Manipulation
Origin of Mechanical Property
- Mechanical Approach
- Origin of Mechanical Property
Mechanical Approach
- Chemical Approachpp
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Mechanical Properties of GrapheneMechanical Properties of GrapheneII-1. Origin of Mechanical Property
p pp p
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Planar Structures – sp2 hybridization
II-1. Origin of Mechanical Property
Planar Structures sp hybridizationsp3 Hybridization
= tetrahedral structures (3D)= tetrahedral structures (3D)
= 4 s bonds
sp2 Hybridization
= trigonal structures (2D)
= 3 s bonds + 1 unpared pz electron
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4n+2 rule and Aromaticity-Chemical Stability
II-1. Origin of Mechanical Property
4n+2 rule and Aromaticity Chemical Stability
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R D l li ti
II-1. Origin of Mechanical Property
Resonance – π - Delocalization
VB TheoryResonance Structure
MO Theory
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Circular Delocalization &
II-1. Mechanical Property
Circular Delocalization & Magnetismg
Circulation of electrons give rise to ring current opposing fieldCirculation of π-electrons give rise to ring current opposing field.
2009.2.12. QMMRC-IPCMSII-1. Origin of Mechanical Property
L li d El t
Delocalization & Friction
Localized Electrons
Frictionless Sliding
Delocalized Electrons
2009.2.12. QMMRC-IPCMS
The edge structures of GrapheneII-1. Origin of Mechanical Property
g p& Lateral Force Microscopy
AFM tip AFMAFM
Localized Electrons 2μmLocalized Electrons
AFM tip LFM LFM
1μm
LFM
2μm
Delocalized Electrons1μm
K. S. Kim et al. (to be submitted)
2009.2.12. QMMRC-IPCMSII-2. Mechanical Approach I
Nano Pencil MethodNano Pencil Method
Y. Zhang, J. P. Small, W. V. Pontius, and P. KimAppl. Phys. Lett. 86, 073104 (2005).
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Scotch-Tape Method
II-2. Mechanical Approach II
Scotch-Tape Method
++ ==
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Chemically Derived Ultrasmooth
II-3. Chemical Approach I
Chemically Derived, Ultrasmooth Graphene Nanoribbon Semiconductors
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Room-temperature graphene
II-3. Chemical Approach I
Room-temperature graphene nanoribbon FETs with high on-off ratios.
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Graphene Sheets reduced from Graphene Oxide
II-3. Chemical Approach II
Graphene Sheets reduced from Graphene Oxide
Graphite (Alpha Co.)Graphite (Alpha Co.)
Fumic acid treatmentFumic acid treatment
Dispersion in water
Carbon 44 (2006) 537
Dispersion in water with NaOH (pH = 10)
Reduction
Reduction with reducing agent (N2H4, NaBH4 etc)
Structure of GO
2009.2.12. QMMRC-IPCMSII-3. Chemical Approach III
Epitaxial Crystallization onSilicon-Carbide/Metal-Carbide Interface
Si-C Ru-C
Nature Materials 7, 406 - 411 (2008)Science 3012, 1191 (2006)
2009.2.12. QMMRC-IPCMS
O i S th i f G h N ibb
II-3. Chemical Approach IV
Organic Synthesis of Graphene Nanoribbons
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Substrate Free Gas Phase Synthesis of Graphene Sheets
II-3. Chemical Approach V
Substrate-Free Gas-Phase Synthesis of Graphene Sheets
100nm
2009.2.12. QMMRC-IPCMS
III. Large-Scale SynthesisIII. Large Scale Synthesis
- Reduction of Graphene Oxides & LB
E f li i f G hi C l & LB- Exfoliation of Graphite Crystals & LB
- Direct Synthesis &Transfer
2009.2.12. QMMRC-IPCMSIII-1. Reduction of GO & LB
Large-area ultra thin films of reduced graphene oxide as a transparent and flexible electronic material
The transparencies from 60 to 95%.
The sheet resistances
1 x 10 5 Ω/ㅁ~1 x 10 5 Ω/ㅁAnnealing at 200 ℃
in N2 (or Vacuum)
Lowest Rs ~ 48 kΩ/ㅁLowest Rs ~ 48 kΩ/ㅁ
Ref : Nature Nanotech. 3, 270 (2008).
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Highly Conducting Graphene Sheets
III-2. Exfoliation & LB
Highly Conducting Graphene Sheets and Langmuir-Blodgett Films
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Highly Conducting Graphene Sheets and
III-2. Exfoliation & LB
g y g pLangmuir-Blodgett Films
2009.2.12. QMMRC-IPCMSIII-2. Exfoliation & LB
Large-area ultra thin films of reduced graphene oxide as a transparent and flexible electronic material
Ref : Nature Nanotech. 3, 270 (2008)).The transparencies from 60 to 95%.
The sheet resistances
1 x 10 5 Ω/ㅁ~1 x 10 5 Ω/ㅁAnnealing at 200 ℃
in N2 (or Vacuum)
Lowest Rs ~ 48 kΩ/ㅁLowest Rs ~ 48 kΩ/ㅁ
2009.2.12. QMMRC-IPCMSIII-3. Direct Synthesis
Patterned growth of centimeter-scale graphene
Ni-C layerCVD of Carbon
Cooling ~RT
Patterned Ni layer (300nm)
g g p
SiO2 (300nm)
Etching by FeCl3 (aq)
Floating Graphene
PDMS
Ni layerEtching
Transfer
Etching by BOE(Buffered Oxide Etchant)
SiO2 layer Ni layer
Graphene on PDMSFloating Graphene on Ni
Etching(Short)
Etching(Long )
2009.2.12. QMMRC-IPCMSIII-3. Direct Synthesis
Patterned growth of centimeter-scale grapheneg g p
2009.2.12. QMMRC-IPCMSIII-3. Direct Synthesis
C t lli N b f G h LControlling Number of Graphene LayersOptical Microscope Images on 300 nm-thick SiO2/Si
Optical Microscope Images of Graphene grown on Ni layers
2009.2.12. QMMRC-IPCMSIII-3. Direct Synthesis
Patterned growth of centimeter-scale grapheneg g p
2009.2.12. QMMRC-IPCMSIII-3. Direct Synthesis
Nano & Microscale Ripplespp
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Etching & Tranfering Patterned Graphene
III-3. Direct Synthesis
g g p
2FeCl3+ Ni 2FeCl2+ NiCl2
FeCl3+ 3H2O Fe(OH)3+ 3HCl
2Fe3+ + Ni 2Fe2+ + Ni2+
c
2009.2.12. QMMRC-IPCMS
Structural Edges of Large-Scale Graphene Films
III-3. Direct Synthesis
Structural Edges of Large Scale Graphene Films
60°
120° 120°
100 μm
Implying the formation of very large crystalline domains.
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Electrical & optical properties of III-3. Direct Synthesis
p p pcentimeter-scale graphene films
80
100
ce (%
)
20
40
60
Tran
smitt
anc
~80% at 550 nm
400 600 800 10000
20
Wavelength ( λ nm)
Sh t R i t 278 /Sheet Resistance ∼ 278 Ω/sq
Crystalline graphene domains are connected mostly by covalent bonds.
Direct Synthesis > Exfoliation of GS > Reduction of GO
Low resistance
~300 Ω/sq ~10,000 Ω/sq ~50,000 Ω/sq
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UV-induced Thinning of Graphene Films
III-3. Direct Synthesis
UV induced Thinning of Graphene Films
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Electromechanical Failure Test
III-3. Direct Synthesis
Electromechanical Failure Test
Jay Lewis, Materials Today, 9, 38 (2008)
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Graphene Films for Foldable Substrates
III-3. Direct Synthesis
89
102
R x)
Graphene Films for Foldable Substrates
67
Ω)
101
sotr
opy
(Ry/R
45
ance
(kΩ
0.0 0.4 0.8 1.2100
Anis
Curvature κ (mm-1) Strain ~ 18%
234
Res
ista
RyRx
Strain 18%
012R x
bending recovery
flat 3.5 2.7 2.3 1 0.8 flat0
Bendig Radius (mm)g ( )
Sheet resistance can be restored after folding.
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Graphene transferred on Pre-Stretched Substrates
III-3. Direct Synthesis
Graphene transferred on Pre Stretched Substrates
Transferred onuniaxiallystretched PDMS.
Transferred onbiaxiallystretched PDMS.
Sheet resistance doesn’t change much against 10% stretching of substrates.
2009.2.12. QMMRC-IPCMS
Qunatum Hall Effect in CVD grown Graphene
III-3. Direct Synthesis
Qunatum Hall Effect in CVD-grown Graphene
The quality of CVD-grown graphene is as high as the mechanically cleaved graphenes.
2009.2.12. QMMRC-IPCMS
IV. IR Characterization of Edge Structuresusing large-scale graphene filmsusing large scale graphene films
10,000 graphene ribbons/mm2 are created by e-beam lithography
100μm
10,000 graphene ribbons/mm are created by e beam lithographyto increase the intensity of IR absorption by graphene edges.
2009.2.12. QMMRC-IPCMS
FT IR S t f Ch i l Ed
IV. IR Characterization
100
FT-IR Spectra of Chemical Edges
00
2909
rb. u
nit)
2909
17111800
Carboxylic C=O
Anhydride C=O
Carboxylic C=O
Carboxylic O-H
98
mitt
ance
(a
1432 3701
Carboxylic C=O
PristinePatterned (by O plasma)
Tran
sm
15953770O-H bending
3701
C-C with C=Oor Carboxylate C=O Aromatic C-C
with C=C
4000 3500 3000 2500 2000 1500 1000 50096
Patterned (by O2 plasma) Patterned and H2O treated
Wavenumber (cm-1)
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P d Ch i l St t f O
III-3. Direct Synthesis
Proposed Chemical Structures of O2
Plasma Etched Graphene Zigzag Edges after Water Treatment
-C=O-COOH
abu
-CH=O-C-OH
-COO-
undance
H
-COOR
e
S i d ti M t l T iti ?Semiconducting-Metal Transition?
2009.2.12. QMMRC-IPCMS
Applications- Ultra-Fast Transistor- Solar Cell- E-paper- THz Devices- Fuel Cell- Graphene Fibers- Volatile Memory- Flash MemoryFlash Memory- TFT- Touch Sensor- Environmental Sensor- Environmental Sensor- Biological Sensor
2009.2.12. QMMRC-IPCMS
V SummaryV. Summary-We have developed a simple method to grow and transfer hi h lit t t h bl h fil i ti t l high-quality stretchable graphene films in centimeter scale utilizing CVD on Ni layers.
-The patterned films can be easily transferred to t t h bl b t t b i l t t th d d th stretchable substrates by simple contact methods and the
number of graphene-layers can be controlled by the thi k f t l ti t l th ti f UV t t tthickness of catalytic metals or the time of UV treatment.
Th t t di ti l l t i l d ti f th - The outstanding optical, electrical and properties of the graphene films enable numerous applications to fl ibl / t t h bl /f ld bl l t iflexible/stretchable/foldable electronics.
2009.2.12. QMMRC-IPCMS
A k l d tAcknowledgement
– Sungkyunkwan University• Dr. Keun Soo Kim, Jung-Hee Han, Jin-Ho Kim, Hoosung Lim, g , , g• Profs. J.H. Ahn,
– Samsung Advanced Institute of Nanotechnology• Dr. Jae Young Choi
– Columbia University• Prof Philip Kim• Prof. Philip Kim
– POSTECH• Prof. Kwang S. Kimg• Dr. Chan-Cuk Hwang