Record-Breaking Speed for Flexible Silicon

Researchers at the University of Wisconsin, Madison, have made ultra-thin silicon transistors that operate more than 50 times faster than previous flexible-silicon devices. The advance could help make possible flexible high-end electronics that would be useful in a variety of applications, from computers to communication. Jack Ma, professor of electrical and computer engineering and lead researcher on the project, is interested in using flexible electronics to redesign large-scale antennas that could be molded in the shape of, say, an airplane. For instance, radar antennas could be made to cover a large area on an airplane, he says, increasing sensitivity and area of coverage.

Most flexible electronics, such as those used in e-paper and roll-up displays for mobile devices, rely on transistors made of either organic polymers, printed directly on a plastic substrate, or amorphous, or noncrystalline, silicon. However, transistors made of these materials can't perform at the gigahertz speeds needed for complex circuitry or antennas. "People have for some time been able to make slow flexible electronics," but the speed of the transistors has been limited, says Max Lagally, professor of materials science and physics at the University of Wisconsin and collaborator of Ma. The next step, he says, has been to make the transistors out of high-quality, single-crystal silicon instead of organic polymers and amorphous silicon because electrons simply move faster in single-crystal silicon.