Researchers at IBM have made the fastest integrated circuits yet from graphene, a material that promises much faster components than silicon allows but which has proven difficult to work with.
The team showed that graphene could be used to make faster, more power-efficient versions of circuits that process and generate radio signals in cell phones and other wireless devices. They did so using existing manufacturing techniques, suggesting their designs could be affordable enough to commercialize.
“This is really exciting work and it points to the rapidly approaching future of graphene electronics,” says James Tour, professor of chemistry and computer science at Rice University in Houston, Texas, who was not involved with the work.
Graphene, a single-atom-thick mesh of carbon atoms, conducts electrons much faster than silicon. Its electronic properties are such that its greatest promise is not for the digital logic circuits found in microprocessors, but for speedy analog electronics, like those made by the IBM team.
Researchers first demonstrated graphene’s electrical promise in 2004 but engineers have since struggled to build graphene circuits using existing manufacturing technology. So far, researchers have made graphene transistors that can operate at speeds of 300 gigahertz, which means they switch on and off 300 billion times a second, thirty times faster than the best silicon transistors.
To make their integrated circuits the IBM researchers had to combine their graphene transistors with other materials, a challenge for two reasons. First, when graphene transistors are positioned too close to certain metals, the transistor performance degenerates. Second, putting graphene transistors and other elements on a single microchip is tricky. Today, in the journal Science, the IBM researchers report methods for making graphene integrated circuits on single chips using existing methods.
The IBM group made a type of circuit called a frequency mixer, combining one graphene transistor and two metal devices called inductors. “The frequency mixer is one of the basic building blocks of analog electronics, and wireless communications in particular,” says IBM researcher Yu-Ming Lin. These devices are used in cell phones to convert the radio signal used to transmit information into another signal in a frequency range that the human ear can hear. That’s accomplished by mixing the radio signal with a reference signal.