One of graphene’s promises for electronics is that it can transport electrons very quickly. Transistors made from graphene could run hundreds of times faster than today’s silicon transistors while consuming less power. Researchers are making progress toward such ultrahigh-radio-frequency transistors. But combining the transistors into circuits is a challenge because graphene is not an ideal semiconductor like silicon. Silicon transistors can be switched on and off between two different states of conductivity. Graphene, however, continues to conduct electrons in its off state. Circuits made from such transistors would be dysfunctional and waste a lot of energy.
One way to improve the on-off ratio in graphene transistors and bring them on par with those made of silicon is to cut the carbon sheet into narrow ribbons less than 100 nanometers wide. But making consistently good-quality ribbons is difficult.
Altering the material chemically may be an easier way to tailor its electronic properties and get the properties sought, Geim says. And that means that researchers could fabricate graphene circuits with nanoscale transistors that are smaller and faster than those made from silicon. “Imagine a wafer made entirely of graphene, which is highly conductive,” he says. “[You can] modify specific places on the wafer to make it semiconducting and make transistors at those places.” Areas between the transistors could be converted into insulating graphane, in order to isolate the transistors from each other.
The new work is just a preliminary first step. The researchers still need to thoroughly test the electronic and mechanical properties of graphane. Converting the material into a decent semiconductor might take a lot more chemical tinkering.
Besides, graphene researchers face one big challenge before they can do anything practical: coming up with an easy way to make large pieces of good-quality material in sufficient quantities. “For many applications, one needs a significant amount of material,” says Hannes Schniepp, who studies graphene at the College of William and Mary. “And that’s yet to be demonstrated for graphene or graphane.”