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See Inside December 2006

Chicken-Wire Electronics

Carbon structures provide new devices and remarkable physics

Since the 1985 discovery of buckyballs (such as the buckminsterfullerene—a nanoscopic sphere of 60 carbon atoms connected in a pattern similar to a traditional soccer ball), researchers have focused intense attention on various chicken-wire-like carbon structures. The latest addition to the menagerie is graphene, a flat single layer of carbon atoms bonded together in the hexagonal pattern of graphite.

In November 2005 two independent research groups, one led by Andre K. Geim of the University of Manchester in England and the other by Philip Kim of Columbia University, experimentally confirmed some extraordinary electronic properties of graphene: the effective mass of electrons in graphene is zero, and they behave like elementary particles obeying a version of Einsteinian relativity instead of Newton's laws of motion. The results open up a remarkable new domain of relativistic physics that can be explored in tabletop experiments.

The development of graphene devices, which might eventually outperform silicon, took a major step forward when Walter de Heer of the Georgia Institute of Technology, along with his collaborators there and at the National Center for Scientific Research in France, used standard microelectronics-industry techniques to make graphene transistors and other circuitry. The ease with which graphene can be shaped to order could give it the edge over carbon nanotubes, which are much harder to build into complex devices.

Nanotube researchers are also continually breaking new ground. Prabhakar R. Bandaru of the University of California, San Diego, and his colleagues there and at Clemson University demonstrated a radically new kind of nanotube-based transistor. Its novel Y shape allows for the elimination of a metal electrode that controls current flow, enabling the transistor to be much smaller than previous designs.

In the field of macroscopic materials made of carbon nanotubes, Ray H. Baughman, Mei Zhang and Shaoli Fang of the NanoTech Institute at the University of Texas at Dallas, along with their collaborators there and at the Commonwealth Scientific and Industrial Research Organization in Belmont, Australia, developed an efficient new way to make thin sheets of nanotubes that might be rapidly adaptable to commercial production. The sheets are strong, lightweight, transparent, highly flexible and electrically conductive, ideally suiting them to be used as components of displays, solar cells, organic light-emitting diodes and artificial muscles, among other applications. Whether it is flat as in graphene or rolled up into nanotubes, the chicken-wire form of carbon continues to go from strength to strength.

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