So... what does the clock rate look like when you've got a network of billions of those things? Propagation delay, rise times, fall times... have they managed to make a simple little CPU out of these graphene transistors yet? Because that would be really cool. The paper's abstract seems to imply that they've found (what they believe to be) a viable way to mass fabricate these, though it makes no mention of an actual network of transistors yet. I can't wait.
Graphene transistor clocked at 427 GHz [pdf]
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Re: Graphene transistor clocked at 427 GHz [pdf]
#22Great. Now we can finally convert heat radiation (300GHz-430THz) to DC using 1mm long antennas and graphene transistor rectifiers.
What about Maxwell demon http://en.wikipedia.org/wiki/Maxwell's_demon ?
Maxwell's Demon applies to heat in the form of brownian motion.
What donquichotte suggests applies to radio waves in the infrared band, basically creating a crystal radio running off light.
We colloquially equate infrared to thermal heat because the former induces physical motion in atoms.
And the suggestion is stark raving awesome.
Re: Graphene transistor clocked at 427 GHz [pdf]
#23That means nothing - IBM made a 350 GHz silicon transistor that can go up to 500 GHz at very low temps: http://www.techspot.com/news/21961-ibm-produces-500ghz-silic... On its own it's useless, though...
427GHz at room temperature isn't nothing.
Re: Graphene transistor clocked at 427 GHz [pdf]
#24The headline is quite misleading to folks with software backgrounds: "Clocked at 427 GHz" implies that the paper's authors measured something with a signal at 427 GHz. In truth, the authors measured up to 30 GHz and extrapolated a figure-of-merit f_T to be 427 GHz.
For comparison: InP-based HBTs were measured north of 400 GHz back in the 90s, which tells you that Graphene in this paper is behind where InP was 20 years ago. Of course, that doesn't make for sexy headlines.
If you're interest in what the figure-of-merit means: f_T is the theoretical maximum frequency that you can build an amplifier and still have the transistor provide gain. Practicalities limit amplifier design (or digital circuits) to frequencies much lower than f_T.
Re: Graphene transistor clocked at 427 GHz [pdf]
#25Great. Now we can finally convert heat radiation (300GHz-430THz) to DC using 1mm long antennas and graphene transistor rectifiers.
I suppose we could, but why would we want to?
Self-powered sensor chips? Micro-transmitters/cameras that don't run down? RFID tags printed onto clothing?
Re: Graphene transistor clocked at 427 GHz [pdf]
#26Earlier quoted context omitted.
Is this a plausible method of extracting useful amounts of energy, or are we talking about yoctowatts per cubic yottametre?
This look quite promising: http://en.wikipedia.org/wiki/Thermal_radiation#Selected_radi... We're speaking of radiant heat fluxes in the > 1kW/m^2 range for a sunny day.
I need more than theoretical maximums to tell me this is practical. At what efficiency could it be captured, and at what cost?
If 1 square meter of "thermal panel" were to cost as much as 1 square meter of modern CPU core, and then operate at 1% efficiency, I wouldn't see many practical applications.
Re: Graphene transistor clocked at 427 GHz [pdf]
#27Earlier quoted context omitted.
I suppose we could, but why would we want to?
We would no longer be slaves to the Carnot cycle. Also, you don't need a temperature gradient anymore. Everything warmer than 0K emits thermal radiation. Think free energy for everyone.
I guarantee you that these rectennas will not work if their temperature is equal to that of the source radiation, and that they will generate waste heat which has to be removed. As for slaves to the Carnot cycle, no one has ever built a Carnot cycle; it is merely an ideal which these rectennas might help us approach more closely.
Re: Graphene transistor clocked at 427 GHz [pdf]
#28Earlier quoted context omitted.
What about Maxwell demon http://en.wikipedia.org/wiki/Maxwell's_demon ?
Maxwell's Demon applies to heat in the form of brownian motion. What donquichotte suggests applies to radio waves in the infrared band, basically creating a crystal radio running off light. We colloquially equate infrared to thermal heat because the former induces physical motion in atoms. And the suggestion is stark raving awesome.
It's far from just colloquial. Infrared and thermal motion at the same temperature contain the same amount of exergy, meaning that the thermodynamic limits on how much work they can do are the same.
Re: Graphene transistor clocked at 427 GHz [pdf]
#29Earlier quoted context omitted.
I suppose we could, but why would we want to?
We would no longer be slaves to the Carnot cycle. Also, you don't need a temperature gradient anymore. Everything warmer than 0K emits thermal radiation. Think free energy for everyone.
Most likely before "free energy for all" you'll have strange IR oriented sensor apps that can analyze the spectrum not just measure total power.
Personally I think it would be fun to see a revival of IR spectroscopy outside of o-chem labs. Its been mostly superseded by NMR in the labs. But imagine an IR spectroscope on a chip. Perhaps for med purposes (what?) or maybe on oil well drilling down hole analysis or something like that.
Or just day to day appliances, like a "smart" household smoke alarm that analyzes the spectrum to identify and ignore tobacco and broiled/grilled meat combustion products but gets really excited about any measurable combustion products of burning furniture or burning paints or burning fabrics. I bet you could cut minutes off fire detection time with one of those, which doesn't sound like much but I bet it would save a lot of lives.
Re: Graphene transistor clocked at 427 GHz [pdf]
#30For anyone curious why this doesn't translate into a 427GHz computer, light can travel about 1.4mm in one cycle at 427GHz, meaning that all synchronized components would have to be located within 1.4mm of each other. The bottleneck for processor speed became the speed of light some years ago.