3 April 2009

New graphene chips much faster than silicon

By
Cosmos Online
With the use of a unique carbon material, researchers are hoping to significantly increase the speed of computers, mobile phones and other communication systems.
Graphene chip

Fast forward: MIT's graphene microhip could operate at much higher speeds than today's silicon chips. Credit: Donna Coveney

SYDNEY: With the use of a unique carbon material, researchers are hoping to significantly increase the speed of computers, mobile phones and other communication systems.

The technology could even have implications for how long Moore’s Law – which has so far accurately predicted the doubling of the number of transistors on microchips every two years – will continue to apply.

The material, called graphene, consists of sheets of carbon just one atom thick. Its unusual properties make it a promising material for future microchips that could transmit data much faster than existing silicon chips.

Upping the frequency

“Graphene will play a key role in future electronics,” said Tomás Palacios, an electrical engineer with the Massachusetts Institute of Technology (MIT) in Boston, USA. “We just need to identify the right devices to take full advantage of its outstanding properties.”

Palacios and his team have used graphene to build a chip known as a frequency multiplier. Frequency multipliers take an incoming electrical signal of a certain frequency and produce an output signal that is a multiple of that frequency.

The MIT graphene chip can double the frequency of an electromagnetic signal, showing the system is a viable way of generating high frequency signals. The next generation of graphene chips will be able to build upon this concept to achieve much higher frequencies, Palacios said.

Reaching higher frequencies is critical to faster computer systems, he said, because it allows data to be transmitted faster. With current technology, it is hard to create signals with frequencies above five gigahertz. Graphene could eventually lead to frequencies in the 500 to 1,000 gigahertz range.

Surpasses existing technology

Graphene holds such promise for increasing communication speed because of its unique electrical properties. It has, for example, very high mobility – the speed at which electrons start moving in the presence of an electric field. This quality is important to electronics, and graphene’s mobility is 100 times that of silicon.

As a result, the graphene chip surpasses existing frequency multipliers in several key ways, the researchers said. Current systems require multiple components, consume large amounts of power and produce signals that require filtering.

The new graphene system has only a single transistor, works more efficiently and produces clean signals that don’t need filtering. In short, Palacios said, the graphene system can multiply frequencies “with unprecedented levels of spectral purity and efficiency.”

He presented the work at an American Physical Society meeting in March, and it will appear in the May issue of Electron Device Letters.

Palacios said graphene will play an important role in the future. Already, it has been used to create prototype transistors, as well as ultracapacitors, storage devices for electrical energy (see, Super-thin material has massive energy storage potential).

“Researchers have been trying to find a use for this material since its discovery in 2004,” Palacios said. “I believe this application will have tremendous implications in high-frequency communications and electronics.”

Barry Cox, a member of the Nanomechanics Group at the University of Wollongong, in New South Wales, Australia, said improved frequency multipliers would have many practical benefits, but cautioned that certain problems still need to be addressed.

Still, he said, “the MIT project looks to be significant scientifically and with good prospects commercially as well.”

More Moore’s Law

John Stride, a chemist with the University of New South Wales, in Sydney, who studies graphene, said he was impressed by the work and its potential applications.

“There are small things to iron out, but they proved you can get higher frequencies with a simple graphene device,” he said. “They need to perfect it so it can be suitable for devices, but they proved the principles.”

Stride added that graphene could extend Moore’s Law if the material is used to improve transistors. First mooted in 1965 by Intel’s Gordon Moore, this predicts that the number of transistors able to be placed inexpensively on a microchip will double every two years.

The law still stands, but scientists debate how long it can last with current technology.

“New semiconductivity technology based on graphene may extend Moore’s Law further in the future,” Stride said.

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More information:
Palacios group – MIT
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