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Graphyne could be better than graphene

Mar 01, 2012

Graphene, a layer of graphite just one atom thick, isn't called a wonder material for nothing. The material is famed for its superlative mechanical and electronic properties. Yet new computer simulations suggest that the electronic properties of a little-known sister material of graphene called graphyne may in some ways be better.

The simulations show that graphyne's conduction electrons should travel extremely fast—as they do in graphene, but in only one direction. That property could help researchers design faster transistors and other electronic components that process one-way current, according to researchers at the University of Erlangen-Nuremberg in Germany.

Electrically, graphene's structure has been considered unique. In most materials, conduction electrons have an energy that depends on the square of their momentum. Graphene's electronic energy levels, however, stack into shapes called Dirac cones, which allow conduction electrons to travel with an energy that is directly proportional to their momentum. As a result, the electrons travel as though they were massless, the way particles of light do - in other words, very fast.

Graphyne is similar to graphene in that it is also a two-dimensional structure of carbon. Unlike graphene, though, graphyne contains double and triple bonds and its atoms do not always have a hexagonal arrangement. Indeed, there may be a vast number of possible graphynes, each with the double and triple bonds in slightly different arrangements. Theorists have been studying graphynes since the 1980s, but little work has been devoted to their electronic properties.

The team have now examined these electronic properties in computer simulations, using a technique called density functional theory. This is standard for mapping the energy levels of different possible forms of the material. The researchers discovered that in one particular graphyne — so-called 6,6,12-graphyne - Dirac cones should still exist but in a distorted, squashed form. As a result the material should conduct electrons in a preferred direction, according to the team.

Source: Science Magazine / Physical Review Letters


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