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Graphene Transistors Clocked At 26GHz
KentuckyFC writes "A team at IBM has built the first high quality graphene transistors and clocked them running at 26 GHz . That doesn't quite knock silicon off its perch. The fastest silicon transistors are an order of magnitude faster than that but the record is held by indium phosphide transistors which have topped 1000 GHz. But it's not bad for a new kid on the block. It took silicon 40 years to get this far. By contrast, the first graphene transistor was built only last year. IBM says 'the work represents a significant step towards the realization of graphene-based electronics.' (Abstract)."
IBM and Columbia are working together on this. Their grant calls for them to push this up to 50 THz.
Oh, and what was done last year was a single electron transistor... normal transistors were available just about as soon as graphene was, in 2004.
Although there is a practical limit to how far a single electron can go, electrical signals don't consist of a single electron going from one end of the wire to the other. Instead, it's like a game of miniature billiards, with electrons lined up in the wire. You pop one in one end, and another falls out the other end almost instantaneously.
There's a practical (and theoretical) limit to how fast this force propagates, too. Fortunately, that's quite high. I don't think electric propagation time is or will be the practical limit on transistor speed.
I searched for "clock" in the paper on arxiv and got no results! The abstract there is more informative:
ABSTRACT
Top-gated graphene transistors operating at high frequencies (GHz) have been fabricated and their characteristics analyzed. The measured intrinsic current gain shows an ideal 1/f frequency dependence, indicating an FET-like behavior for graphene transistors. The cutoff frequency f_T is found to be proportional to the dc transconductance g_m of the device, consistent with the relation f_T=g_m/(2piC_G). The peak f_T increases with a reduced gate length, and f_T as high as 26 GHz is measured for a graphene transistor with a gate length of 150 nm. The work represents a significant step towards the realization of graphene-based electronics for high-frequency applications.
Yes, but unless you can make them break the speed of light there is going to be a very hard limit on how far you can send the signal within an oscillation. At 1 Ghz the signal can travel around 30 centimeters before next cycle, at 5 Ghz you are down to 6 cm (compared to speed of light, since they are going slightly slower mileage will vary), when things go fast enough "almost instantaneously" is quite a long time.
OK, if you are an undergrad deciding on your choice for thesis and postgrad studies, graphene is great. There is a lot of companies, including Nokia, that pour tons and tons of money into graphene research. It's the easiest grant money to get these days.
That said, there's a reason you don't see much GaAS integrated circuits, even though GaAs has been around for decades, and has much higher carrier mobility (and therefore top speeds) than silicon: it's hard to devise a good IC technology for GaAs. For graphene the problems are way, way bigger than that even. I have seen some attempts of my colleagues (I research in nanosci) at fabricating graphene transistors, and while they can make discrete components with a certain limited rate of success, integration is not even on the horizon. Maybe other people around the world use technologies that are more promising, but it will take a great effort to knock silicon off the top spot for the time being. In fact, I predict a brighter immediate future for Si/Ge and some III/V group compounds as the successors of pure Si, as the next big thing in IC tech.
"The agriculture ministry is not in charge of Gundam" - Japanese ministry official.
The brain, we must never forget, consists of two independent hemispheres that work together--via the corpus callosum--but whose functions and methodology are different.
The left hemisphere, which is bigger and faster and evolved earlier, is mostly discrete storage locations, optimized towards the storage of individual bits of information. This same left hemisphere is optimized toward the processing of linear-sequential pattern-streams of information, such as those found in language and the maintenance of words.
Current computers work in a manner more similar to the way our older left brain hemisphere works.
The right hemisphere, which evolved later than the left, is smaller and consists more of axon/dendrite interconnections, making he right hemisphere better optimized towards the processing of visual-simultaneous pattern streams.
Virtually no current computer system even attempts to model the visual-simultaneous pattern stream processing that is done by the right hemisphere. That consists of taking in patterns of data points and comparing those to known shape and other sub shapes and the associations that are introduced and the recursive processing of gleaning information from images.
The human ear has about 30,000 neurons leading data to the brain. The human eye has about 1,000,000 neurons leading data to the brain. You can see it's an order-of-magnitude harder problem and so yes, it needs more speed!
Actually, the propagation speed can be pretty close to c. The speed of an electron is pretty darn slow (on the order of inches per hour, IIRC), but the propagation speed of an electromagnetic wave (which is what actually does stuff. it's like a hose full of marbles. you push a marble in, and another one pops out the other end.) is about 0.96c in good copper.
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