Researchers Pencil In Graphene Transistors

Graphene's weird electrical properties allow for smallest transistor yet.

IMAGE: Anna Demian/Randi Silberman

Pushing Pencils: Graphene, found in pencil marks, is a candidate material for making future transistors. It's extracted from graphite crystals [right] using sticky tape.

The little smudges you leave behind whenever you use a pencil could be the key ingredient of the next revolution in computer circuitry, according to experts around the globe. Part of what shears off from the graphite in a pencil is a substance known as graphene, a one-atom-thick crystal with remarkable electrical properties that may overcome the physical limits silicon faces as transistors shrink to ever-smaller sizes.

Silicon's remarkable run as ruler of the chip world may be nearing an end as engineers eventually lose the ability to make faster silicon transistors by making them smaller. In the hunt for what comes next, carbon nanotubes have gotten a big chunk of the attention, but if the current explosion of research activity is any indication, it may be graphene that wins in the end. This spring saw a flurry of breakthroughs surrounding graphene, culminating in the creation of what may be the smallest transistor ever made—one atom thick by 10 to 50 atoms wide.

Like carbon nanotubes, graphene is a crystal structure of carbon atoms but arranged in a flat plane instead of a cylinder. The electrons in graphene behave as if they have no mass. Like photons—but unlike electrons in other materials—the electrons move at a constant speed, regardless of how much energy each one has.

A transistor built out of graphene, therefore, should operate much faster than a comparable one made from silicon. Michael S. Fuhrer, a physicist at the University of Maryland's Center for Nanophysics and Advanced Materials, recently showed that at room temperature electrons in graphene move at 200000 centimeters per second for every volt per centimeter of electric field, 100 times faster than in silicon. “All other things being equal, that would translate into a 100 times faster transistor,” he says.

Graphene has been known for decades as a single plane of graphite, but it was only in 2004 that Andre Geim and Kostya Novoselov of the University of Manchester, England, were able to isolate it by the simple act of pressing a piece of tape to a graphite crystal and placing it on a silicon substrate. In April, the two researchers described their transistor, 10 to 50 atoms wide and built by etching a pattern into graphene. [read more]