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Graphene and its applications

Among the several different forms in which carbon exist, graphite is the most common form, which consists of stacked sheets of carbon with a hexagonal structure.


Graphene is a single layer of carbon packed in a hexagonal (honeycomb) lattice and its electronic structure is different from usual three-dimensional materials. Its Fermi surface is characterized by six double cones. In intrinsic (undoped) graphene the Fermi level is situated at the connection points of these cones. The electrical conductivity of intrinsic graphene is quite low, as density of states of the material is zero at the connection points of these cones.


But the Fermi level can however be changed by an electric field so that the material becomes either n-doped (with electrons) or p-doped (with holes) depending on the polarity of the applied field. Graphene can also be doped by adsorbing water or ammonia on its surface. The electrical conductivity for doped graphene is potentially quite high.


Graphene is practically transparent, maintains its 2D properties at room temperature and in the optical region it absorbs only 2.3 per cent of the light in contrast to low temperature 2D systems based on semiconductors. It is an ultimately thin, mechanically very strong, transparent and flexible conductor. Its conductivity can be modified over a large range either by chemical doping or by an electric field. The mobility of graphene is very high, which makes the material very interesting for electronic high frequency applications.Using near-industrial methods, large sheets of graphene with a width of 70 cm have been produced.

Since graphene is a transparent conductor it can be used in applications such as touch screens, light panels and solar cells, where it can replace the rather fragile and expensive Indium-Tin-Oxide (ITO). Flexible electronics and gas sensors are other potential applications. The quantum Hall effect in graphene could also possibly contribute to an even more accurate resistance standard in metrology. New types of composite materials based on graphene with great strength and low weight could also become interesting for use in satellites and aircraft.

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