Graphene transistor could advance nanodevices

May 11, 2010 By Miranda Marquit feature
Graphene transistor. Image credit: Peking University

(PhysOrg.com) -- For years, scientists and researchers have been looking into the properties of carbon nanotubes and graphene for use in nanoelectronics. "There is no real mass application of devices based on graphene and carbon nanotubes," Zhenxing Wang tells PhysOrg.com. "This is really an opportunity for them to show their capabilities."

Wang is part of a group at the Key Laboratory for the Physics and Chemistry of at Peking University in Beijing. Along with Zhiyong Zhang, Huilong Xu, Li Ding, Sheng Wang, and Lian-Mao Peng, Wang tested a top-gate field-effect transistor based frequency doubler in order to gauge its performance. They were able to show that a graphene based frequency doubler can provide more than 90% converting efficiency, while the corresponding value is not larger than 30% for conventional frequency doubler. Their work is published in : “A high-performance top-gate graphene field-effect transistor based frequency doubler.”

“Our work focused on raising the gain and frequency response of the frequency doubler by utilizing top-gate geometry on the device,” Wang explains. “Only with a top-gate can people fabricate high-performance devices and integral circuits. This work paves the way to mass application of graphene transistors in the near future.”

Graphene is desirable as a transistor material due to its high performance. Wang points out that IBM recently showed that graphene transistor can operate up to 100 GHz, and the group at Peking University believes that the material may even still operate well in the THz regime. “This is very exciting,” Wang says, “because a frequency doubler with high frequency and high efficiency can be very expensive. Our device is cheaper - only consisted by one transistor - but with much higher efficiency.”

In Beijing, the group fabricated the device with standard lithography, layering the graphene on a silicon wafer, smaller than 1mm x 1mm. In order to test the performance, Wang and his colleagues used a digital oscilloscope. They also used a recent test method, developed at Peking University, to measure performance of the graphene doubler. “We developed a new test method with a spectrum analyzer, which can obtain direct frequency information and sense a much smaller signal that can’t be obtained by oscilloscope.”

Moving forward, this work could lead to the development of graphene transistors for . “In principle, this kind of device can be realized on a wafer scale, based on current lithography technology and wafer-scale graphene growth. Mass production can be realized once the graphene growth technology becomes mature,” Wang explains. “We are looking forward to the mass production of a graphene based frequency doubler with frequency response up to 100 GHz, gain larger than 1/10, and with low cost and low power consumption.”

This future, though, could still be five to 10 years away, and Wang is not overly concerned about the mass production end of it just yet. “I’m now focusing on improving the performance of the device in demonstration in order to show its potential. Possible optimization can be made through such means as replacing the substrate with insulating materials to reduce the parasitic capacitance.” At some point, though, graphene could help advance the development of nanoscale electronics, and the work done by the scientists at Peking University are providing a step in that direction.

Explore further: Toward making lithium-sulfur batteries a commercial reality for a bigger energy punch

More information: Zhenxing Wang, et. al., “A high-performance top-gate graphene field-effect transistor based frequency doubler,” Applied Physics Letters (2010). Available online: link.aip.org/link/APPLAB/v96/i17/p173104/s1

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trekgeek1
3.8 / 5 (5) May 11, 2010
Ready in 5 to 10 years? That's tomorrow! Really though, 5 to 10 years will be here very soon. THz would be nice for a computer processor. I'll say it again, I am seriously seeing the exponential technology growth. It seems like there is a breakthrough everyday whereas in the past it was months. In the past we imagined technologies far grander than were realized. I think this time the technology of the near future will surpass our expectations.
rincewind
not rated yet May 11, 2010
I am seriously seeing the exponential technology growth


Yeah there's certainly a lot of exciting research going on. There's a problem with all this frothing at the mouth though - I've started to watch science news with such an (exponential) interest that the pace of these advancements now look boringly linear :-)

Funny though how this article says that graphene transistors "could" advance devices, when on the right-hand sidebar I see a link to an article from 2007 that discusses the first series of these transistors - it's 3 year old news at the very least (http://www.physor...53.html)
PinkElephant
5 / 5 (1) May 11, 2010
One fly in the THz ointment: they're talking about a single transistor switching frequency. In a typical CPU pipeline stage, you have a certain number of transistors connected in series, and the entire chain must complete its computation in a single clock cycle. Thus, if you have longest chains of 10-deep in a given pipeline stage, implemented on 1 THz transistors, then your maximum clock frequency is "only" 100 GHz.
lengould100
1 / 5 (1) May 18, 2010
In a typical CPU pipeline stage, you have a certain number of transistors connected in series, and the entire chain must complete its computation in a single clock cycle.
Reference?
PinkElephant
not rated yet May 18, 2010
Anyone with a CS or EE degree, or more generally anyone who has taken an introductory computer architecture course, knows this. But here you go:

http://en.wikiped...pipeline