Tuesday, March 22, 2011

Graphene nanoribbons enable quantum switches

March 22, 2011

A new “templated growth” technique for fabricating nanoribbons of epitaxial graphene has produced structures just 15 to 40 nanometers wide that conduct current with almost no resistance, says Walt de Heer, a professor in the School of Physics at the Georgia Institute of Technology.

The graphene nanoribbons are being used to develop high-frequency transistors — perhaps even at the terahertz range — and lower power quantum devices.

The technique involves etching patterns into the silicon carbide surfaces on which epitaxial graphene is grown. The patterns serve as templates directing the growth of graphene structures, allowing formation of nanoribbons and other structures of specific widths and shapes without the use of cutting techniques that produce rough edges.

The width of the resulting nanoribbons is proportional to the depth of the contours, providing a mechanism for precisely controlling the nanoribbon structures. To form complex structures, multiple etching steps can be carried out to create complex templates.

The wave properties of epitaxial graphene allow electrons to be manipulated with techniques similar to those used by optical engineers. For example, switching can be carried out using interference effects –– separating beams of electrons and then recombining them in opposite phases to extinguish the signals.

De Heer’s research team hopes to demonstrate a rudimentary switch operating on this quantum interference principle within a year, and possibly a new generation of transistors.

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