Graphene

One of the most promising material

3

Andrei Geim and Kostya Novoselov extracted the graphene

from a piece of graphite such as is found in ordinary pencils by

playing with a sticky tape (University of Manchester).

Friday night experiments

Using regular adhesive tape they managed to obtain a flake of

carbon with a thickness of just one atom.

This at a time when many believed it was impossible for such

thin crystalline materials to be stable.

Andre Geim, Dutch citizen. Born

1958 in Sochi, Russia. Ph.D. 1987

from Institute of Solid State

Physics, Russian Academy of

Sciences, Chernogolovka, Russia.

Director of Manchester Centre for

Meso-science & Nanotechnology,

Langworthy Professor of Physics

and Royal Society 2010

Anniversary Research Professor,

University of Manchester, UK.

By the way ,he got another noble

prize named the most funny

noble prize.

Konstantin Novoselov,British and Russiancitizen. Born 1974 inNizhny Tagil, Russia.

Ph.D. 2004 fromRadboud UniversityNijmegen, TheNetherlands. Professorand Royal SocietyResearch Fellow,University ofManchester, UK.

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8

Carbon allotropes

9

WH

Y

GR

AP

H

ENE

(discovered 2004)

c

ab

Graphene: extraordinary thermal conductivity

~ 3000-5000 W/mK [Nano Lett. 8, 902–907, 2008]

(highest among materials – responsible for the high

thermal conductivity of graphite (ab-plane) and CNT!

• Graphene: building block

for most carbon materials

---incl. graphite and

carbon nanotubes(CNT)

• Recently, carbon materials

(incl. both graphite and CNT)

investigated as attractive

thermal interface material

(TIM) motivated by their

high thermal conductivity

Other advantages of graphene:

•High packing density [due to 2D]

•rich shapes/geometry

•Easily functionalized

•Possibilities to bond to surface

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12

Atomic force microscopy image of a graphene crystal on top of an oxidized Si

substrate. Folding of the flake can be seen. The measured thickness of

graphene corresponds to the interlayer distance in graphite. Scale

bar = 1 µm.

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First observations of graphene date back to at least 1962.

H. P. Boehm et al. Zeitschrift für Naturforschung B 17, 150 (1962).

With TEM

14

15

Single sheet of Carbon atoms: monolayer graphite.

Honeycomb structure.

Nearest neighbour distance a=1.42A.

Two Carbon sub-lattices.

Carbon → 4 valence electrons: 3 for sp2 bonds.

The 4th one is in a pz orbital ( band).

The pz orbital is perpendicular to the plane and rotational symmetric around z-axis.

Condensed-matter systems usually described accurately by the Schrödinger equation.

Quantum relativistic effects are usually minute.

Electron transport in graphene is governed by Dirac’s (relativistic) equation.

Charge carriers in graphene mimic relativistic particles with zero rest mass and effective speed of light vF≈106 m/s.

Variety of unusual phenomena characteristic of 2D Dirac fermions.

Graphene is a one-atom-thick planar sheet of sp2-bonded carbon atoms that are

densely packed in a honeycomb crystal lattice

The name ‘graphene’ comes from graphite + -ene = graphene

High resolution transmission electron microscope images

(TEM) of graphene

Introduction to graphene

Molecular structure of graphene

A. K. Geim & K. S. Novoselov. The rise of graphene. Nature Materials Vol . 6 ,183-191 (2007).

10/2004

10/2002

(Quoted from “Cambridge IP”)

“

”

Very stable

Even at room temperature, electrons in graphene are more than 100 times more mobile than in silicon.

97.3 percent transparent

Graphene is stronger and stiffer than diamond

Good thermal conductivity

The poperties of it.

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- Electronic properties

- Thermal properties

- Mechanical properties

- Optical properties

- Relativistic charge carriers

- Anomalous quantum Hall effect

Material Electrical Conductivity (S·m-1) Notes

Graphene ~ 108

Silver 63.0 × 106 Best electrical conductor of any known metal

Copper 59.6 × 106Commonly used in electrical wire applications due to

very good conductivity and price compared to silver.

Annealed Copper 58.0 × 106

Referred to as 100% IACS or International Annealed

Copper Standard. The unit for expressing the

conductivity of nonmagnetic materials by testing using

the eddy-current method. Generally used for temper and

alloy verification of aluminium.

Gold 45.2 × 106Gold is commonly used in electrical contacts because it

does not easily corrode.

Aluminium 37.8 × 106Commonly used for high voltage electricity distribution

cables[citation needed]

Sea water 4.8 Corresponds to an average salinity of 35 g/kg at 20 °C.[1]

Drinking water 0.0005 to 0.05This value range is typical of high quality drinking water

and not an indicator of water quality

Deionized water 5.5 × 10-6

Conductivity is lowest with monoatomic gases present;

changes to 1.2 × 10-4 upon complete de-gassing, or to 7.5

× 10-5 upon equilibration to the atmosphere due to

dissolved CO2[2]

Jet A-1 Kerosene 50 to 450 × 10-12 [3]

n-hexane 100 × 10-12

Air 0.3 to 0.8 × 10-14

MaterialThermal conductivity

W/(m·K)

Silica Aerogel 0.004 - 0.04

Air 0.025

Wood 0.04 - 0.4

Hollow Fill Fibre Insulation Polartherm 0.042

Alcohols and oils 0.1 - 0.21

Polypropylene 0.25 [6]

Mineral oil 0.138

Rubber 0.16

LPG 0.23 - 0.26

Cement, Portland 0.29

Epoxy (silica-filled) 0.30

Epoxy (unfilled) 0.59

Water (liquid) 0.6

Thermal grease 0.7 - 3

Thermal epoxy 1 - 7

Glass 1.1

Soil 1.5

Concrete, stone 1.7

Ice 2

Sandstone 2.4

Stainless steel 12.11 ~ 45.0

Lead 35.3

Aluminium237 (pure)

120—180 (alloys)

Gold 318

Copper 401

Silver 429

Diamond 900 - 2320

Graphene (4840±440) - (5300±480)

Thermal properties

We can make Super-Small Transistors with it .In this

way, the moore's law that have worked for 45 years

can effect for decades.

For example ,in 2010, IBM developed a Graphene FET

with a 100G （it can reach to 1T in theory) cut-off

frequency ,while cut-off frequency of FET made by

silicon is lower than 40G.

The university of Pennsylvania made out 4 inch Graphene wifer in recently.

SO

ME

PIC

TUR

ES

SECO

ND

Since this kind of material isstrong, stiff and light, somepeople suppose we can builda tower from earth to thespace.

In fact ,we can use it tomake many mechanicaldevices such as airplane,carand so on.

TH

IRD

We can use it to produce transparent conductive film that can use to make solar battery.

This kind of film have a high conductivity , high transparent rate.We needn't to protect this film because it's strong.

FO

UR

TH

We can develop small senor to

detect the small cell or graphene

quantum dots to detect even one

molecular in the air.

HO

WTO

MA

KE

IT?There are so many way to use

it ,but how can we product it? Nobody have a good way.

If you have one,you will be a billionaire.

The noble prize winner use garphite and tap.They succeed and win noble prize .

Preparation and characterization graphene

Preparation methods

Top-down approach(From graphite)

Bottom up approach (from carbon precursors)

- By chemical vapour deposition (CVD)

of hydrocarbon

- By epitaxial growth on electrically

insulating surfaces such as SiC

- Total Organic Synthesis

- Micromechanical exfoliation of graphite (Scotch

tape or peel-off method)

- Creation of colloidal suspensions from graphite

oxide or graphite intercalation compounds (GICs)

Ref: Carbon, 4 8, 2 1 2 7 –2 1 5 0 ( 2 0 1 0 )

Characterization methods

Scanning Probe Microscopy (SPM):

- Atomic force microscopes (AFMs)- Scanning tunneling microscopy (STM)

Raman Spectroscopy

Transmission electron Microscopy (TEM)

X-ray diffraction (XRD)

Atomic force microscopy images of a graphite oxide

film deposited by Langmuir-Blodgett assembly

Now,some companies or labs use different methods to get it .There are three main methods .

Top-down approach(From graphite)

Graphite oxide methodGraphite intercalation compoundDirect exfoliation of

graphite

Preparation methods and discussions

Direct exfoliation of graphite

Micromechanical exfoliation of graphite (Scotch tape or peel-off method). S

Graphene sheets ionic-liquid-modified by electrochemistry using graphite electrodes.

Liu, N. et al. One-step ionic-liquid-assisted electrochemical synthesis of ionicliquid-

functionalized graphene sheets directly from graphite. Adv. Funct. Mater. 18, 1518–1525 (2008).

Direct exfoliation of graphite

J. Mater. Chem. 2005, 15, 974.

Graphite intercalation compound

Graphite oxide method ( Most common and high yield method)

Graphite

Oxidation (Hummers’method)

H2SO4/ KMnO4

H2SO4/KClO3

Or H2SO4/HNO3

……………….H2O

Ultrasonication (exfoliation)

Graphite Oxide

Graphene Oxide

monolayer or few layers

Fuctionalization (for better dispersion)

Making composite with polymers

Chemical reduction to restore graphitic structures

Tung, V. C., Allen, M. J., Yang, Y. & Kaner, R. B. High-throughput solution

processing of large-scale graphene. Nature Nanotech. 4, 25–29 (2008).

Graphite oxide method

More intercalation for better exfoliation to monolayers

Graphite oxide

Graphite oxide method

Bottom up approach (from carbon precursors)

Yang, X. Y.; Dou, X.; Rouhanipour, A.; Zhi, L. J.; Rader, H. J.;

Mullen, K. J. Am. Chem. Soc. 2008, 130, 4216.

Total Organic Synthesis

Graphene nanoribbons(from carbon nanotube)

NATURE, Vol , 458, 16 , April (2009)

Potential application of graphene

- Single molecule gas detection

- Graphene transistors

- Integrated circuits

- Transparent conducting electrodes for the replacement of ITO

- Ultracapacitors

- Graphene biodevices

- Reinforcement for polymer nanocomposites: Electrical, thermally conductive nanocomposites, antistatic coating, transparent conductive composites..ect

Why graphene? Unusual properties

Surface EM waves in graphene

Radiation patterns: surface plasmons and free-space fields

A point source: the fundamental problem

Possible applications

Optical solutions: possible future of Electronics?

Thin metallic optical interconnectors

Graphene optical interconnectors

Atomic structure and electronic properties

• One atomic layer-thick

• Zero mass of electrons

• High electron mobility

• Pronounced response to external voltage

Graphene transistors and integrated circuits

H. B. Heersche et al., Nature 446, 56 (2007)

Y.-M. Lin et al. (IBM), Science 327, 662 (2010)

cutoff frequency of 100 GHz for a gate length of 240 nm supercurrent transistor

Unusual optical properties

Optical properties

Extremely thin, but seen with the naked eye

• It absorbs of white light

• Conductivity is sensible to external fields

• Saturable absorption

• Could be made luminescent

• Supports surface electromagnetic waves

F. Bonaccorso et al., Nature Phot. 4, 611 (2010)

Graphene-based optoelectronics

LEDSolar cell

Flexible smart window

2.3%

Unusual optical properties

Surface EM waves in graphene

Surface plasmons (SPs) in metallic surafces

W. L. Barnes et al., Nature 424, 824 (2003)

~ iqxe

~ x Le

q

qqq

Surface EM waves in graphene

Conductivity of graphene

300T K

0.2eV

Surface EM waves in graphene

Surface waves in graphene

~ iqxe

~ x Le

Im( ) 0

Im( ) 0

Surface EM waves in graphene

Graphene metamaterials and Transformation Optics

Spatial varying voltage 2D graphene plasmonic prism

2D graphene plasmonic waveguide Transformation Optics devices

Surface EM waves in graphene

A point source: the fundamental problem

A point source: the fundamental problem

Possible sources for local excitation

molecule

quantum dot

Josephson qubit

A point source: the fundamental problem

Electric dipole

( )?E r

A point source: the fundamental problem

Computational difficulties: asymptotic approach

2( )

1

iqx

zp

eE x dq

q q

polebranch cutpole

branch cut

L. P. Felsen and N. Marcuvitz, Radiation and Scattering of Waves (IEEE Press, Piscataway, NJ, 1994)

Radiowave propagation problems

graphene

oscillating factor

Radiation patterns: SPs and free-space fields

Density of electromagnetic states

( ) ~ iqxE x dq DOS e

0.024 1.12

Radiation patterns: surface plasmonsand free-space fields

Radiation patterns: SPs and free-space fields

Vertical dipole

0.31 , 0.97mm THz

SP characteristics:

SP 200L

Radiation patterns: SPs and free-space fields

Vertical dipole

41.3 , 7.2m THz

SP characteristics:

0.1SP 3L

Radiation patterns: SPs and free-space fields

Vertical dipole

1( 6.2 , 48.4 )m THz

2 ( 3.1 , 96.7 )m THz No SP excited

SP characteristics:

0.01SP 0.1L

No SP excited

Radiation patterns: SPs and free-space fields

Horizontal dipole

SP characteristics:• long propagation length• wavelength close to the vacuum one

0.31 , 0.97mm THz

Radiation patterns: SPs and free-space fields

Horizontal dipole

15.5 , 19.3m THz SP characteristics:

• medium propagation length (of order of several wavelengths)• wavelength is quite less than the vacuum one

Radiation patterns: SPs and free-space fields

Horizontal dipole

No SP excited

3.1 , 96.7m THz

Possible applications

Possible applications

A. Gonzalez-Tudela et al., PRL 106, 020501 (2011)

Qubits coupling through graphene SPs waveguides

A. Vakil et al.,arXiv: optics/1101.3585

EM fields created by apertures in graphene

A. Yu. Nikitin et al., PRL 105, 073902 (2010)