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WASHINGTON, D.C. — For fifty years the silicon transistor has steadily grown smaller, allowing manufacturers to cram millions and millions more transistors onto their computer chips. But experts forecast that the silicon transistor will soon reach its physical limits, so a race to develop the next transistor technology is afoot. Phaedon Avouris, manager of IBM's Nanometer Scale Science and Technology Research Division, will present his team's cutting-edge alternative to silicon: transistors made of graphene, a one-atom-thick layer of carbon that is highly conductive to electricity and can be turned on and off very quickly. As recently reported in Science, the team has created high-frequency 100 gigahertz RF graphene transistors that could be useful for high-speed communications devices and faster than silicon devices of the same size.
They are also working to solve a problem that currently prevents graphene from being used in digital electronic devices -- its lack of a band gap, which means that current continues to flow in a graphene device even after it has been turned off. A computer chip packed with graphene transistors would have trouble reliably identifying which ones were on and which were off. To improve this situation, IBM's researchers stacked two parallel layers of graphene on top of each other, an arrangement theoretically predicted to provide a band gap upon application of a high perpendicular electric field. They achieved an on/off current ratio of 100:1 at room temperature, not quite good enough yet for digital electronics but about twenty times better than the typical on/off ratio of single-layer graphene. "Creating a band gap in graphene is probably one of the most important and tantalizing research topics in the graphene community since it may ultimately enable new applications in digital electronics, pseudospintronics, terahertz technology, and infrared nanophotonics," the researchers report.
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