IBM designs new generation high-speed graphene circuits

The IBM advance, which the researchers reported in the Science, is a circuit known as a broadband frequency mixer that was built on a wafer of silicon. Widely used in all kinds of communications products, the circuits shift signals from one frequency to another.

In the Science paper, the IBM researchers describe a demonstration in which they deposited several layers of graphene on a silicon wafer, then created circuits based on graphene transistors and components known as inductors. They demonstrated frequency mixing up to speeds of 10 gigahertz. In the past IBM has created stand-alone graphene transistors but not complete electronic circuits.

Scientists began making flakes of graphene, an atomic-scale lattice of carbon atoms, in the 1970s. They have gradually refined the process so they can now produce films of the material that are just a single atom thick. The film arranges itself in a hexagon-shaped array of carbon atoms and has the advantages of being flexible, transparent and inexpensive to manufacture. But it is not yet a candidate to replace today’s CMOS transistors, which are the basis for the microprocessors and computer memories used in consumer electronics systems. Graphene does not have the same physical properties as semiconducting materials and cannot be used to completely switch on and off in the way that logic transistors are meant to do.

That has not tempered the industry’s excitement over potential applications for the material. In Europe and Asia, government and corporate investments are running far in advance of those in the US, said Phaedon Avouris, an chemical physicist who is a leader of the IBM’s research effort. “Outside the US there is a lot of interest,” he said.

Both the European Union and South Korea have recently started $1.5 billion efforts to build industrial-scale efforts using graphene as a next-generation display material, he said. Singapore has also recently started a major investment in the material. IBM’s research has been supported by a more modest effort financed by the Defense Advanced Research Projects Agency, the Pentagon office that supports futuristic science and technology. (Graphene is being explored as a substitute for materials like gallium arsenide, used in high-frequency military communications equipment.)

One promising application for graphene is in making new parts of the radio-frequency spectrum available for consumer electronics applications, said Richard Doherty, president of Envisioneering Inc., an industry consulting firm. For example, it might make possible a new class of Wi-Fi-style communications gear for wireless applications, or allow set-top cable boxes to be redesigned to send and receive ever-larger amounts of high-resolution video and data.

Doherty added that display manufacturers were especially interested in graphene because the current wave of displays based on OLEDs, or organic light-emitting diodes, have limited lifespans. Last year, researchers at Sungkyunkwan University in South Korea announced that they had scaled up a technique to make full-screen displays based on an approach to making graphene film pioneered at the University of Texas.

The promise of the low cost of the material could push graphene into today’s conventional consumer electronics systems. “In principle it can be made very cheap and it can be light-transparent and so even if we don’t go for high frequency, I think it can revolutionize the price of radio-frequency electronics,” said Avouris.

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