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Graphene is a two dimensional crystal consisting of a single layer of carbon atoms arranged hexagonally. (Image Source: Lawrence Berkley National Lab)

Graphene is a one atom thick, two dimensional material which consists of carbon atoms densely packed into a honeycomb-like crystal lattice.  This is known as a single layer graphene.  Bi-layer and multi-layer graphenes have also been synthesized in the laboratory.

Graphene exhibits very interesting electrical, optical, mechanical, thermal and other properties.  Electrically, it is a semimetal or a semiconductor with zero bandgap.  Graphene shows a very low resistivity, for example, only 10-6 Wcm at room temperature.  A single lay er graphene film is highly opaque, it absorbs only 2% of the white light.  The mechanical properties are exceptional; for example, the Young’s modulus is about 1 Tera Pascal (one trillion or 1012 Pascal). 

This image of a single suspended sheet of graphene taken with Transmission Electron Aberration-corrected Microscope shows individual carbon atoms (yellow) on the honeycomb lattice. (Image Source: Lawrence Berkley National Lab)

The interesting properties of graphene have led to an explosion of research recently in their synthesis, characterization of their properties, and development of applications.  Promising applications include electronics devices, transparent conducting electrodes for solar cells and plasma displays, composites, energy storage devices, and chemical and biological sensors. 

Currently researchers are able to produce graphene by reducing graphene oxide.  This chemical synthesis approach can now yield gram quantities of the material.  It is also possible to deposit single layer of graphene on a silicon wafer.  A technique called chemical vapor deposition allows growth of single or multilayer graphene at 900-1000º C.