Graphene to pave way for new generation of faster mobiles, computers

Engineers have paved the way for a new generation of faster, more powerful cell phones, computers and other electronics by developing a practical technique to replace silicon with carbon on large surfaces.The developers of this novel technique that harnesses the power of carbon for more powerful electronics are Princeton nanotechnologist Stephen Chou, professor of electrical engineering and graduate student Xiaogan Liang.Stephen Chou said that the capabilities of silicon, the material at the heart of computer chips, has been harnessed beyond its limits by engineers, and carbon has come up as an intriguing replacement for the same. The material called graphene which is a single layer of carbon atoms arranged in a honeycomb lattice, could let electronics to process information and produce radio transmissions 10 times better than silicon-based devices. However, switching from silicon to carbon has not been possible until now because technologists thought that they needed graphene material in the same form as the silicon used to make chips- a single crystal of material eight or 12-inches wide. Till date, the largest single-crystal graphene sheets made have not been wider than a couple millimeters, which is not big enough for a single chip. The researchers realized that a big graphene wafer is not needed, until they could place small crystals of graphene only in the active areas of the chip. A novel method was thus developed, in order to achieve this goal and demonstrated it by making high-performance working graphene transistors. "Our approach is to completely abandon the classical methods that industry has been using for silicon integrated circuits," said Chou. In the new method, the researchers made a special stamp consisting of a collection of tiny flat-topped pillars, each one-tenth of a millimeter wide. They pressed the pillars against a block of graphite (pure carbon), cutting thin carbon sheets, sticking to the pillars. The stamp was then removed, peeling away a few atomic layers of graphene. Finally, the stamp was aligned with and pressed against a larger wafer, leaving the patches of graphene exactly where transistors will be built. Chou said that the technique was just like printing. By repeating the process and using variously shaped stamps (the researchers also made strips instead of round pillars), all the active areas for transistors are covered with single crystals of graphene."Previously, scientists have been able to peel graphene sheets from graphite blocks, but they had no control over the size and location of the pieces when placing them on a surface," said Chou. The technique was possible through one innovation - to coat the stamp with a special material that sticks to carbon when it is cold and releases when it is warm, allowing the same stamp to pick up and release the graphene. Chou's lab took the next step and built transistors -- tiny on-off switches -- on their printed graphene crystals. Their transistors displayed high performance and were more than 10 times faster than silicon transistors in moving "electronic holes" which is a key measure of speed.This new technology could find almost immediate use in radio electronics, such as cell phones and other wireless devices that require high power output, Chou said. Chou predicted that the technique could be applied to wireless communication devices within a few year, depending on the level of interest from industries. "What we have done is shown that this approach is possible; the next step is to scale it up," said Chou.