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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,


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


BackgroundBackground

Transparent?

No YES


Non-Flexible Electronics


Foldable-Stretchable Electronics


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


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


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.


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)


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.


Covalent CNT/Graphene-molecule bridgesCovalent CNT/Graphene-molecule bridges

Xuefeng Guo, et al. ãÖie^Öe 311, 356-35č (2006)


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!


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).


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


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


Graphene Electronics I. Introduction

Replacing Si-based Semiconductor Technology?

All G h El t iAll G h El t iAll Graphene ElectronicsAll Graphene Electronics


All Graphene Electronics I. Introduction

Replacing Si-based Semiconductor Technology?


Electric Field Effect in Electric Field Effect in Atomically Thin Carbon Film

Science 306, 666 (2004)


2D gas in Quantum Limit: Conventional Case2D gas in Quantum Limit: Conventional Case


Quantum Hall Effect in GrapheneQuantum Hall Effect in Graphene


Graphene Nanoribbons: Confined Dirac Particles

I. Introduction

Graphene Nanoribbons: Confined Dirac Particles


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.


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


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


Higher Charge Density

I. Introduction

Higher Charge DensityOf Graphene Edges

Nano Lett 7, 2295 (2007)


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


II. Graphene Synthesis/Manipulation

Origin of Mechanical Property

- Mechanical Approach

- Origin of Mechanical Property

Mechanical Approach

- Chemical Approachpp


Mechanical Properties of GrapheneMechanical Properties of GrapheneII-1. Origin of Mechanical Property

p pp p


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


4n+2 rule and Aromaticity-Chemical Stability


4n+2 rule and Aromaticity Chemical Stability


R D l li ti


Resonance – π - Delocalization

VB TheoryResonance Structure

MO Theory


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


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).


Scotch-Tape Method

II-2. Mechanical Approach II

Scotch-Tape Method

++ ==


Chemically Derived Ultrasmooth

II-3. Chemical Approach I

Chemically Derived, Ultrasmooth Graphene Nanoribbon Semiconductors


Room-temperature graphene

II-3. Chemical Approach I

Room-temperature graphene nanoribbon FETs with high on-off ratios.


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)


O i S th i f G h N ibb

II-3. Chemical Approach IV

Organic Synthesis of Graphene Nanoribbons


Substrate Free Gas Phase Synthesis of Graphene Sheets

II-3. Chemical Approach V

Substrate-Free Gas-Phase Synthesis of Graphene Sheets

100nm


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).


Highly Conducting Graphene Sheets

III-2. Exfoliation & LB

Highly Conducting Graphene Sheets and Langmuir-Blodgett Films


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 )


Patterned growth of centimeter-scale grapheneg g p


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


Patterned growth of centimeter-scale grapheneg g p


Nano & Microscale Ripplespp


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


Structural Edges of Large-Scale Graphene Films


Structural Edges of Large Scale Graphene Films

60°

120° 120°

100 μm

Implying the formation of very large crystalline domains.


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


UV-induced Thinning of Graphene Films


UV induced Thinning of Graphene Films


Electromechanical Failure Test


Electromechanical Failure Test

Jay Lewis, Materials Today, 9, 38 (2008)


Graphene Films for Foldable Substrates


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.


Graphene transferred on Pre-Stretched Substrates


Graphene transferred on Pre Stretched Substrates

Transferred onuniaxiallystretched PDMS.

Transferred onbiaxiallystretched PDMS.

Sheet resistance doesn’t change much against 10% stretching of substrates.


Qunatum Hall Effect in CVD grown Graphene


Qunatum Hall Effect in CVD-grown Graphene

The quality of CVD-grown graphene is as high as the mechanically cleaved graphenes.


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.


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)


P d Ch i l St t f O


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?


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


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.


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

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