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Graphene May be the New Silicon
esocid writes to share that University of Maryland physicists have demonstrated that the material of the future may be graphene rather than silicon. Electricity conduction through graphene is about 100 times greater than that of silicon and could offer many improvements to things like computer chips and biochemical sensors. "Graphene, a single-atom-thick sheet of graphite, is a new material which combines aspects of semiconductors and metals. [...] A team of researchers led by physics professor Michael S. Fuhrer of the university's Center for Nanophysics and Advanced Materials, and the Maryland NanoCenter said the findings are the first measurement of the effect of thermal vibrations on the conduction of electrons in graphene, and show that thermal vibrations have an extraordinarily small effect on the electrons in graphene."
...refers to electron mobility, a concept I hadn't previously encountered. But it's easy enough to understand: if I apply a unit electric field to a material, how fast does it make the electrons drift? This is the mobility.
Apparently graphene (also new to me ... a single-atom layer of carbon) is exciting because it has much higher electron mobility than silicon. Which leads to faster switching times, although they don't explain that part.
All this seems to be theoretical at the moment, due to insufficiently pure graphene. Still, 100th the switching delay is not a bad target to be aiming at... 100Ghz processing!
I recall that early compact discs had this problem, in which oxygen trapped in the plastic would oxidize the aluminum and reduce its reflectivity.
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Graphene is certainly a lot like carbon nanotubes, but is much easier to work with. Where you have to hope to get a semiconducting crystal structure in a nanotube (or make crappy transistors based on defects), you can pattern graphene to make a transistor. Which directions you cut the 2D sheet determine whether it is metallic or semiconducting. There are some problems with this, and practically speaking any small channel (10 nm, I think) of graphene is semiconducting. Fuhrer has shown (along with other people) that graphene can make pretty good transistors (very fast switching, thermally stable and I'm sure I'm missing some stuff).
It can be doped. This is another thing Fuhrer has done (as well as other people... but this is his article we're talking about). You don't want to insert something into the crystal structure (that ruins it), but you can layer the top of it with potassium ions (about 1 per 1000 carbons), which dopes it just fine. This isn't a bulk semiconductor though, and the addition of charged impurities (dopants) decreases device performance (in bulk, it's a metal). You can very easily electrostatically gate graphene in any direction you want; transistors and PN junctions are easy to make this way.
It is not hard to make graphene. The "scotch tape" method from Manchester is widely used, but there are a number of other ways to do it which may be commercially viable: oxidizing graphite, ultrasounding graphite with special polymers (Dai's method), growing it from SiC wafers. Of course, none of these really work yet, and may never be economical.
Graphene is stable in air (almost all devices are measured in air at some point), and liquids. It's not going to spontaneously dissolve on you just because it's only 1 atomic layer thick. It's actually very robust.
It can be used with silicon processing techniques. People are using SiO2, HfO2 and all the usual silicon processing with it.
Big companies are looking at this material. IBM has already reported results on their work at physics conferences, I'm fairly sure that the more secretive companies (Intel) are also working with graphene... just like they worked with nanotubes.