graphene presentation

Amity School of Engineering & Technology

Graphene: From fundamental

to future applications

Aman GuptaB.Tech ECE 3 Sem


Content Introduction to graphene.

Preparation and characterization graphene

Potential application of graphene

Conclusions


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).

Introduction


- 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.


- 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


Preparation of graphenePreparation 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)


Characterization methodsScanning 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


Top-down approach (From graphite)

Graphite oxide methodGraphite intercalation compoundDirect exfoliation ofgraphite

Preparation methods and discussions


Graphite oxide method

Graphite

Oxidation (Hummers’method)

H2SO4/ KMnO4

H2SO4/KClO3

Or H2SO4/HNO3

………………. H2O

Ultrasonication (exfoliation)

Graphite Oxide

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


More intercalation for better exfoliation to monolayers

Graphite oxide


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.


Transparent conducting electrodes


FUTURE TRENDS IN GRAPHENEFlexible 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.


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.


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.


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.


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.