March/April 2008

TR10: Graphene Transistors

Continued from page 1

By Kevin Bullis

In fact, the devices that de Heer announced in December were carved into graphene using techniques very much like those used to manufacture silicon chips today. "That's why industry people are looking at what we're doing," he says. "We can pattern graphene using basically the same methods we pattern silicon with. It doesn't look like a science project. It looks like technology to them."

Graphene hasn't always looked like a promising electronic material. For one thing, it doesn't naturally exhibit the type of switching behavior required for computing. Semiconductors such as silicon can conduct electrons in one state, but they can also be switched to a state of very low conductivity, where they're essentially turned off. By contrast, graphene's conductivity can be changed slightly, but it can't be turned off. That's okay in certain applications, such as high-frequency transistors for imaging and communications. But such transistors would be too inefficient for use in computer processors.

In 2001, however, de Heer used a computer model to show that if graphene could be fashioned into very narrow ribbons, it would begin to behave like a semiconductor. (Other researchers, he learned later, had already made similar observations.) In practice, de Heer has not yet been able to fabricate graphene ribbons narrow enough to behave as predicted. But two other methods have been shown to have similar promise: chemically modifying graphene and putting a layer of graphene on top of certain other substrates. In his presentation in Washington, de Heer described how modifying graphene ribbons with oxygen can induce semiconducting behavior. Combining these different techniques, he believes, could produce the switching behavior needed for transistors in computer processors.

Meanwhile, the promise of graphene electronics has caught the semiconductor industry's attention. Hewlett-­Packard, IBM, and Intel (which has funded de Heer's work) have all started to investigate the use of graphene in future products.

See All 10 Emerging Technologies 2008