Graphite may work wonders with chips

Paul Boughton

At the Institute of Physics’ Condensed Matter and Materials Physics conference at the University of ExeterAndre Geim of the University of Manchester and his colleagues claim that graphitethe silvery blacksoft form of carbon known for thousands of yearscould yield a new generation of microelectronic devicesas well as unveiling unprecedented effects in quantum physics.

But this is no ordinary graphite. The stuff in ordinary pencils consists of stacked sheets of carboneach sheet made up of atoms linked together to form a hexagonal network like chicken wire. Geim and colleagues have discovered that interesting and potentially useful electronic behaviour appears when these sheets are separated and laid out one sheet at a time.

A single graphite sheet is called graphene. This same gossamer-thin material has attracted intense interest over the past 10 years or so when it is rolled up into longhollow cylinders called carbon nanotubes. Nanotubes are predicted to be extremely strongand they conduct electricity in ways that have already been exploited to make electronic devices smaller than any made by conventional silicon-chip fabrication methods.

But Geim and colleagues say that the appeal of this kind of carbon lies not with nanotubes in themselvesbut with the underlying fabric: the flat sheets of graphene. They have developed methods for splitting graphite apart into its separate layers and lying them down flat on a surfacewhere their electrical properties can be studied. A graphene sheet is electrically conductingbehaving essentially like a two-dimensional metal. But it is a strange kind of metalwith properties dictated by quantum mechanics. For exampleeven if there are no mobile electrons to carry an electrical currentthe electrical conductivity can never fall below a certain minimum value: it is like an electron gate that can never be fully closed. 

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