
Graphene transistor clocked at 427 GHz [pdf] - WestCoastJustin
http://www.pnas.org/content/early/2012/06/25/1205696109.full.pdf
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jpmattia
The 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.

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ChuckMcM
Nice result. As others have pointed out its not a record or anything, but it
is a solid indication that graphene transistors are, in fact, credible. An
example of a not really credible transistor are the various organic ones, they
have frequency limits in the high kHz to single digit MHz.

But workable graphene transistors gets us one step closer to an all carbon
device. Using diamond as a substrate for heat removal, Graphene-on-Diamond (oh
snap, those would be GoD devices) could provide for an interesting replacement
for more exotic silicon processes. (one could argue that an all carbon process
is more exotic still if one chose to).

The benefits over silicon would be faster operation at an equivalent
temperature, and the ability to operate at a higher temperature. Pretty much
all silicon products melt at a junction temperature around 175 degrees C but
carbon based devices should be able to continue to operate well into a few
hundred degrees C if I am reading the papers correctly.

Should be an interesting decade.

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donquichotte
Great. Now we can finally convert heat radiation (300GHz-430THz) to DC using
1mm long antennas and graphene transistor rectifiers.

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Filligree
I suppose we could, but why would we want to?

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donquichotte
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.

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nknighthb
Is this a plausible method of extracting useful amounts of energy, or are we
talking about yoctowatts per cubic yottametre?

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donquichotte
This look quite promising:
[http://en.wikipedia.org/wiki/Thermal_radiation#Selected_radi...](http://en.wikipedia.org/wiki/Thermal_radiation#Selected_radiant_heat_fluxes)

We're speaking of radiant heat fluxes in the > 1kW/m^2 range for a sunny day.

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nknighthb
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.

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rkangel
The interesting phrase here is "scalable fabrication". Like the many new
battery technologies, there are many ways you can make next-gen transistors,
but none of them yet has been manufacturable at large scale.

To me, it's not the transistor that's impressive in modern technology it's the
manufacturing process we use to make large scale silicon devices. It's those
that are becoming increasingly hard to advance and those that we need to find
replacements for.

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tcoppi
Funny, I've heard that one of the things making graphene exciting to industry
is that it may be easy to adapt existing photolithographic processes to it. I
don't know how true that is though.

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burke
For 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.

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cinquemb
I wonder if some the research going on at nasa right now about FTL
transportation can be applied at some point?

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burke
I doubt it. As far as I understand it, NASA's research centers around the
possibility of deforming spacetime to cause an object to fall through space
(sorta).

Deforming spacetime wouldn't really put components closer together, or cause
light to travel faster, or anything.

You never know with stuff this weird though. Maybe something else will fall
out of their research. It's been known to happen when pushing the boundaries
of our understanding of physics.

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cinquemb
Well if you treat light like an object (if you consider its particle like
properties), and deform space-time between the components (or more like deform
space-time around the light, so it is of regardless where the components are
in euclidean space), wouldn't that theoretically achieve the same thing as
making light "move" faster between the components?

Though the way I envision that the components would have be connected by or
lie in some kind of vacuum. I mean, these have to be the in the family of
tests NASA will have to be conducting on particles before "moving" ships
through free space becomes some kind of reality, right?

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anigbrowl
[http://www.technologyreview.com/view/518426/how-to-save-
the-...](http://www.technologyreview.com/view/518426/how-to-save-the-troubled-
graphene-transistor/)

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jotm
That 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...](http://www.techspot.com/news/21961-ibm-
produces-500ghz-silicon-germanium-cpu.html)

On its own it's useless, though...

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ctdonath
427GHz at _room temperature_ isn't nothing.

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aspensmonster
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.

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powertower
How would you even sample a signal like that in the real world?

The best Oscilloscopes you can get right now commercially go to about 65GHz
using hybrid chips
([http://youtu.be/dx596o8t_TY](http://youtu.be/dx596o8t_TY)) and cost $500K...

* [http://www.home.agilent.com/en/pd-2108888-pn-DSAX96204Q/infi...](http://www.home.agilent.com/en/pd-2108888-pn-DSAX96204Q/infiniium-high-performance-oscilloscope-63-ghz)

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gryphonic
I work in high frequency RF (10s to 100s of GHz). You can use mixers[0] to
down convert higher frequency signals and make measurements at lower
frequencies.

[0][http://rfic.eecs.berkeley.edu/~niknejad/ee142_fa05lects/pdf/...](http://rfic.eecs.berkeley.edu/~niknejad/ee142_fa05lects/pdf/lect15.pdf)
[pdf]

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Lewton
What are transistors in current gen cpus clocked at?

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alexwright
Intel have their gate delay graphed with 22nm vs. 32nm (and also the switch to
3D gates)... but I'm not sure what the units used here are. It's on page 21 of
this PDF:
[http://www.intel.co.uk/content/dam/www/public/us/en/document...](http://www.intel.co.uk/content/dam/www/public/us/en/documents/presentation/silicon-
technology-leadership-presentation.pdf)

picoseconds maybe?

Edit: Yea, pico, I think. From another PDF on Intel tech: "At 15nm, the gate
delay is 0.39psec, and for 10nm gate length, the gate delay has dropped to
0.11psec"

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hcarvalhoalves
If we could get a graphene CPU clocked at _10 GHz_ in the next few years I
would already consider it a success.

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constapop
While this is nice result, it still doesnt solve the biggest problem -
scalability. Also this graphene device doesnt turn off.

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luscious
Great. Year+ old. Thanks for Hacker -> News <-

