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1. Amity School of Engineering & Technology
Graphene: From fundamental
to future applications
Aman Gupta
B.Tech ECE 3 Sem

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Content
Introduction to graphene.
Preparation and characterization graphene
Potential application of graphene
Conclusions

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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

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

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- Electronic properties
- Thermal properties
- Mechanical properties
- Optical properties
- Relativistic charge carriers
- Anomalous quantum Hall effect
Properties of graphene
Electronic properties
Where υd is the drift velocity in m/s (SI units)
E is the applied electric field in V/m (SI)
µ is the mobility in m2
/(V·s), in SI units.

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- High Young’s modulus (~1,100 Gpa)
High fracture strength (125 Gpa)
- Monolayer graphene absorbs πα ≈ 2.3% of white light (97.7 % transmittance),
where α is the fine-structure constant.
Mechanical properties
Optical properties
A representation of a diamond tip with a two nanometer radius
indenting into a single atomic sheet of graphene (Science, 321 (5887):
385)
- Graphene is as the strongest material
ever measured, some 200 times stronger than
structural steel

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Preparation of 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)

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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

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Top-down approach
(From graphite)
Graphite oxide methodGraphite intercalation compoundDirect exfoliation of
graphite
Preparation methods and discussions

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Graphite oxide 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

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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).

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More intercalation for better exfoliation to monolayers
Graphite oxide

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Total Organic Synthesis

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Graphene nanoribbons
(from carbon nanotube)
NATURE, Vol , 458, 16 , April (2009)

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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.

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Transparent conducting electrodes

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FUTURE TRENDS IN GRAPHENE
Flexible Touch Screens-
The outstanding properties of graphene make it attractive for applications in flexible electronics.
Byung Hee Hong, Jong-Hyun Ahn and co-workers have demonstrated roll-to-roll production
and wet chemical doping of mostly monolayer graphene films grown by chemical vapors
deposition onto flexible copper substrates.
They also used layer-by-layer stacking to fabricate a doped four-layer film with properties
superior to those of commercial transparent electrodes such as indium tin oxides. The
photograph on the cover shows a flexible touch-screen device containing graphene electrodes.

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Magnetism and Graphene-
Given the great versatility of graphene’s properties and especially the ability to control
many of its characteristics by external electric field (gate voltage), graphene has a potential
to become an excellent material for spintronics.
Our current efforts concentrate on ‘making graphene magnetic’ by introducing point
defects, such as vacancies or adatoms. We have already demonstrated that vacancies in
graphene act as individual magnetic moments and lead to pronounced paramagnetism.

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Graphene Sensors-
University of Manchester scientists were the first to demonstrate single-atom sensitivity in
graphene Hall-bar devices. The most sensitive electronic detection is achieved by
constructing a Hall-bar with graphene. This transverse Hall resistivity is very sensitive to
changes in carrier concentration.

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CONCLUSION
Graphene has an interesting history, but many now wonder about its future. The
subject of considerable scholarly debate, it does seem reasonable to assert a few
things looking ahead:
First, the quality and availability of “synthetic” graphene will continue to
improve. Whether high quality material comes in the form of an alternative
chemical route to the complete exfoliation of graphite or from optimization of the
thermal processes required for substrate-based methods, there is no sign that
synthetic techniques are nearing their upper limit. This means that device
engineers will have ample access to improved materials for developing novel
structures and finding ways to integrate graphene into present-day electronic
devices.

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Second, chemical modification of graphene’s basal plane or its edges will substantially
influence graphene-based devices. For electronic applications, one can imagine the
attachment of functional groups aimed at self-assembly of simple circuits or the
incorporation of chemical dopants to limit leakage current under zero gate bias. For sensors,
lock and-key type binding sites could provide selective sensitivity to a wide variety of
analytes. These might include chemical warfare agents or even biological species.
Third, industrial use of graphene as a transparent conductor could have huge implications for
the solar industry. As synthetic routes improve, the prospect of replacing ITO with a low-cost
carbon-based coating seems feasible. This would not only remove significant uncertainty
about the availability and cost of indium but also enable non evaporative roll-to roll
processing of transparent conductors.

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