"We've been working on graphene high-frequency transistors for a while, so we took the natural next step to try to make integrated circuits," said Phaedon Avouris, an IBM fellow who led the project. "The challenge has been how to propagate integrated circuits on graphene, which has different characteristics than semiconductors such as silicon."
The researchers published their technique in this week's issue of Science.
The circuit that IBM built, a broadband frequency mixer, can operate at frequencies of up to 10GHz, or 10 billion cycles per second. The mixer can convert a wavelength of a higher frequency into a lower one. The circuit consists of a graphene transistor and a pair of inductors integrated on a silicon carbide (SiC) wafer.
Graphene is an ultrathin material consisting of a single layer of carbon atoms arranged in a honeycomb structure. The material has excellent electrical, mechanical and thermal properties. Until now, however, it has been difficult to fuse graphene transistors with other materials, such as silicon. Manufacturing techniques are still quite primitive as well.
Today's silicon-based circuits can scale to only about 40GHz, Avouris said. So circuits that can handle wavelengths of 10GHz could enhance a wide variety of electronic devices. They could be used in military wireless communications devices, providing a basis for short-range, ultra-secure communications that would be much more difficult to decrypt. In radar, the higher frequencies that graphene offers could be used to enhance the resolution of objects being tracked.
And because of its ultra-thin nature, graphene could be embedded into glass panels, providing the basis for low-cost, high-resolution television or phone screens.
The U.S. Defense Advanced Research Projects Agency, known as DARPA, helped fund the work.
