Graphene May be the New Silicon 115
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."
The "100 times greater"... (Score:5, Interesting)
...refers to electron mobility [wikipedia.org], 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!
Would oxidation be a problem? (Score:5, Interesting)
I recall that early compact discs had this problem, in which oxygen trapped in the plastic would oxidize the aluminum and reduce its reflectivity.
Re:The "100 times greater"... (Score:5, Interesting)
What took awhile (and was solved with a fairly low-tech solution : scotch tape) was how to make a single layer of graphene to measure, whereas graphite usually rolled off into multi-layer pieces.
Graphene is interesting for a number of reasons. Primarily is it's Minkowski lightcone-like density of states. The Fermi level lies right at the cone vertex, which makes this material a "zero-bandgap insulator", which brings about a huge number of interesting properties in itself.
Anyway, graphene has been hugely popular in condensed matter physics for a few years now, and people have studied the phonon spectra, I remember going to a seminar about the modes of graphene in a carbon nanotube a few years ago.
However, don't get your hopes up for mass-produced graphene tech anytime soon. While people will probably demonstrate small-scale single-electron transistors or other interesting graphene devices (if they haven't already), the ability to deposit and pattern graphene is still very crude, and it's hard to do anything other than one-off devices at this point.
Comment removed (Score:4, Interesting)
Re:The "100 times greater"... (Score:3, Interesting)
Re:The "100 times greater"... (Score:4, Interesting)
Re:The "100 times greater"... (Score:5, Interesting)
The increased mobility has little to do with gates. In fact, you want gates (in MOSFETs [wikpedia.org]) to be as resistive as possible, but still not attenuate the electric field that results from the gate voltage, hence the use of Halfnium dioixde instead of silicon dioxide (you can make it thicker, (and thus more resistive) while still having a strong enough field.)
Mobility results from the equation v=(mu)E, where mu is the mobility and v is the velocity of an charge carrier (electron or hole) The reason we use semiconductors is that we can easily control the number of electrons or holes. But by increasing the speed of electrons, we can allow them to switch faster since they will be able to cross the channel more quickly. That's why smaller transistors can switch more quickly, the channel length is shorter so it takes less time for carriers to traverse them.
I'm not sure why it's considered so amazing to discover that graphene has a good electron mobility. Since, the entire structure consists of delocalized pi orbitals, you would expect electrons to easily travel through graphene. I'm not sure how graphene would be doped either. I suppose you could use boron and phosphorous like in silicon, but it remains to see if they will still bond appropriately. Ah well, there's a reason, they're professors and I'm a student.
Question about "holes" (Score:3, Interesting)
An electron can move and fill a hole, but leaves another hole behind in the location it just departed. So a "hole" moving in one direction is entirely equivalent to an electron moving in the opposite direction, is it not?
If so, why does this term have any usefulness, if, instead of saying "the hole moved from point A to point B" you could just as easily say "the electron moved from point B to point A"?
Help me understand why much ado is made about holes.