Graphene

KL7AJ

Joined Nov 4, 2008
2,229
Hi Bill:

This is EXACTLY the sort of stuff we need to be alert to...I think there are going to be entire universes of possibilities of applications (and cash!) that we haven't even touched on. I've always been a big fan of materials engineering....I think it will be the "next semiconductor" industry.

Eric
 

bituufg

Joined Jul 8, 2009
1
The answer to #1 is .074 because gravity is a constant.

The answer to #2 is "angular momentum = the sq root of velocity"

answer to #3, I have worked out but get 2 different answers, so you can email me on wednesday, and by then I'll have the definitive answer.
 

Thread Starter

Wendy

Joined Mar 24, 2008
23,798
Grahene makes a pretty decent lubercant, but I doubt they would notice. Still, brings some funny pictures to mind.
 

MrShhh

Joined Jul 7, 2009
24
A friend of mine is doing the final year of his phd on graphene...It's fascinating stuff! He was talking about charge within graphene moving at relativistic speeds the last time we spoke. And something about electron holes. Cool.
 

Thread Starter

Wendy

Joined Mar 24, 2008
23,798
There is a very good chance CPUs will be made out of graphene soon, if some other material doesn't push it out of the running. It is the best semiconductor form of carbon. Diamond is a close runner up, and bucky tubes are a wild card (with the very real potential for superconductivity). Carbon is like a universal building block, you can make almost anything from it.
 

b.shahvir

Joined Jan 6, 2009
457
There is a very good chance CPUs will be made out of graphene soon, if some other material doesn't push it out of the running. It is the best semiconductor form of carbon. Diamond is a close runner up, and bucky tubes are a wild card (with the very real potential for superconductivity). Carbon is like a universal building block, you can make almost anything from it.
But what makes the processor speed up data transfer? low resistance or low parasitic reactances? thanx
 

Thread Starter

Wendy

Joined Mar 24, 2008
23,798
Actually, nowdays it is the size of the transistor, as well as switching speed. The faster a transistor can go from on/off and off/on, the less heat it makes. The size enters into it because that limits how many transistors can fit on a die. Nowdays we are into the billions of transistors per die, so the little (and it is extremely small) amount of heat each transistor makes during switching adds up fast.
 

b.shahvir

Joined Jan 6, 2009
457
Actually, nowdays it is the size of the transistor, as well as switching speed. The faster a transistor can go from on/off and off/on, the less heat it makes. The size enters into it because that limits how many transistors can fit on a die. Nowdays we are into the billions of transistors per die, so the little (and it is extremely small) amount of heat each transistor makes during switching adds up fast.

Me thinks the on/off speed of solid state device depends on value parasitic capacitance across the depletion layers of the semicontuctor. The larger the value of parasitic capacitance, lower the switching speed and vice-versa.

Semiconductor resistance might not have anything to do with switching speed apart from heat dissipaton or power loss.

Best regards,
Shahvir
 

Thread Starter

Wendy

Joined Mar 24, 2008
23,798
Tell that to a transistor that lets only 1 or 2 electrons through. We are in the realm of quantum (which is one reason graphene shines), the rules aren't quite the same.


But even old tech, if a transistor switch has high impedance, and the output is low (but some finite), the semiconductor impedance also doesn't enter into it (I am assuming a really high input impedance). The only time there is conductance (ie, heat) is during the switching process when both transistors are on, which in turn only happens when they change states. A CPU that is not toggling draws pico amps or less.

Yes, there is parasitic capacitance on the input of a FET, but remember we are talking extremely small sizes, so the capacitance is also extremely small. The smaller the transistor, the less parasitic capacitance.
 
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