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Graphene as superconductor?

Posted: Fri Mar 21, 2008 1:13 pm
by drmike
There is an article in the April Scientific American about graphene. Several articles on the net point out that the electronic properties so far found are that the electrons have zero mass and appear to move at almost light speed, so relativistic quantum theory needs to be used to describe their motion.

There is no mention of superconductivity, but if the material has superior low resistance the main question is how much current it can carry in multiple layers. It may be that it has very low resistance, but no current carrying capability. Cool stuff to study at any rate.

Posted: Sat Mar 22, 2008 7:18 pm
by Isochroma
Carbon-based superconductors: Kyoto Price Winner Dreams of a Carbon Future

http://www.wired.com/science/discoverie ... 3/kyoto_qa

Posted: Sat Mar 22, 2008 8:53 pm
by drmike
thanks! I've been watching the Kibo module and the next stage will come up in a couple of months. I bet there are a few carbon experiments on it!

Posted: Tue Mar 25, 2008 5:59 pm
by Isochroma
Physicists Show Electrons Can Travel More Than 100 Times Faster in Graphene

https://www.newsdesk.umd.edu/scitech/re ... cleID=1621

Posted: Tue Mar 25, 2008 9:21 pm
by scareduck
I like the photo of UMD physicist Michael S. Fuhrer. He looks like he can't wait to get out of the office and shoot some curls off Trestles.

Posted: Wed Mar 26, 2008 1:04 am
by drmike
Thanks Isochroma! Looks like more research is being done and will continue.

My pony tail is almost as long as Fuhrer's, but it has a lot more grey in it :)

Posted: Wed Mar 26, 2008 11:39 am
by MSimon
drmike wrote:Thanks Isochroma! Looks like more research is being done and will continue.

My pony tail is almost as long as Fuhrer's, but it has a lot more grey in it :)
I don't know if you have seen a picture of Steve MacIntyre at Climate Audit, but I'm almost a dead ringer for him. Size, weight, current body shape, beard, facial features.

Think of it as one of those stock Civil War photos you sent back home when you couldn't afford your own sitting. :-)

Let me add - what is it with all the "hippies" focused on this? Tom Ligon, Dr. Mike, me?

Reminds me of the early days 1975 to 1980 of the computer revolution. Pictures of the early Microsoft crew are most interesting in that respect. In the early days of the computer revolution I'd say about 50% of the people involved were hippies.

Posted: Wed Mar 26, 2008 3:37 pm
by drmike
:D

Must be something to do with having fun. I've tried to explain to my wife
that "it's part of the uniform" - every group has one. Seems perfectly
natural to me!

Posted: Sat Mar 29, 2008 2:49 pm
by jmc
Isochroma wrote:Carbon-based superconductors: Kyoto Price Winner Dreams of a Carbon Future

http://www.wired.com/science/discoverie ... 3/kyoto_qa
Wasn't the word semi-conductors?

Posted: Sat Mar 29, 2008 4:39 pm
by Isochroma
read the topic my friend

Posted: Sat Mar 29, 2008 4:43 pm
by drmike
It's both. They want to build high speed transistors, so it is "almost" superconducting but allows trapping of electrons in quantum wells. I don't see how it can carry massive currents yet, but it will great if we can find a way to reduce resistance by a factor of 100 in all electronics. It may not be superconducting but that would really help with power use.

It's not a semi-conductor either - it's way too good a conductor. But it allows the construction of transistors, so I think that's the news spin. Everyone knows transistors are made of semi-conductors, so that's the mental translation.

It's neat stuff and the fact you can create it with a pencil and some tape makes it really fun too!

Posted: Sat Mar 29, 2008 6:44 pm
by MSimon
I was under the impression that what made semi-conductors work was the 4 valence bonds and the band gap. Of course it has been a very long time since I looked into the theory (I'm an applications guy), so I could be mistaken.

In any case I do know that diamond semiconductors are in the works. And SiC semiconductors are already here. Both SiC and diamond are high temperature materials. Very handy. Both have higher stand off voltages than Si. The high mobility in diamond helps heat conduction and frequency response. - Let me add that for very small Si structures the transistors are about as fast as the wires and the real hold up is the speed of light. Lower resistance should help a lot with the RC delay product.

I grew up when the CK722 was state of the art for hobbyists. Those were junction transistors and if you could get one to oscillate above 1 MHz it was a miracle.

Posted: Mon Mar 31, 2008 5:20 pm
by hanelyp
As I see it, the essence of a semiconductor for electronics work is having few charge carriers. As opposed to many charge carriers for a conductor, or no free carriers for an insulator. Having a small number of charge carriers, adding or removing a few carriers vastly changes conductivity. The 4 valence electrons of silicon, doped with a small amount of a 3 or 5 valence electron element, is a simple way of making a suitable material. GaAs and related compounds are also used.