Then along came Geim. Creator of a gecko-inspired adhesive that made headlines four years ago, Geim is the type of researcher who likes to try something totally new every few years. Jealous of all the attention that nanotubes received over the years—"It's a beautiful system," he says—he began hunting for graphene in autumn 2002. "Spite is a very important motivation for physicists," he deadpans.
Researchers knew how to expose flawless surfaces from graphite chunks by peeling away thick layers with Scotch tape. Geim decided to push the method to its limit.
He quickly achieved 10-atom-thick layers. "Then you always ask yourself a question," he says: "Let's try nine." In a 2004 Nature paper, he and his colleagues reported success. They had placed a single graphene layer on silicon, connected electrodes to it and measured the amount of charge it carried when they applied different voltages.
"That was of course a big deal," laughs Kim, who had wagered on the needle-dragging method. "We realized we were completely scooped."
Massless Electrons Attract the Masses
Few groups took notice, Geim says, even after his team showed how to make graphene layers using what amounted to a pencil.
The field would not really take off until late the following year, when he and Kim independently confirmed a prediction with roots dating to the 1940s. They applied a magnetic field to graphene and observed that its resistance (the drag on a current) increased in a stepwise pattern called the quantum Hall effect. The effect comes in two varieties, both of which have garnered Nobel Prizes. Graphene, they observed, supports yet a third kind.
Researchers were floored. It was as if someone had slapped a piece of tar paper onto an open phone book and ripped out a page, says nano researcher Philip Collins of the University of California, Irvine. "You would expect the page to be junk," he says, but instead, "you can still get the phone numbers off of it." Those who study nanotubes and the quantum Hall effect alike have flocked to graphene, says Pablo Jarillo-Herrero, a researcher in Kim's laboratory and one of the flock.
Even particle physicists are excited, says materials theorist Antonio Castro Neto of Boston University, one of those who predicted the new quantum Hall effect. The key to graphene's abilities, including its high conductivity, comes from something that particle physicists are very familiar with. Most particles, including the electron, have mass. Like billiard balls, they do not move until given an energy boost by some impetus (such as a pool cue). The more energy they get, the faster they fly.
In contrast are photons, particles of light, which have no mass and move ceaselessly at a constant speed—the speed of light. What Geim and Kim confirmed is graphene's electrons effectively lose their mass. No matter how much energy they carry, they scurry at one four-hundredth the speed of light.
To describe particles produced in accelerators or elsewhere in the cosmos moving at close to light speed, physicists have to bring in special relativity, Einstein's theory of motion. The same goes for graphene.
Nanotubes share this property; they are actually better conductors than graphene because they force electrons to zip along a straight line. Graphene's flatness, however, makes its relativistic behavior more pronounced and easier to probe, Kim says.
Hyper Powerful or Overhyped?
One consequence of graphene's massless electrons, Geim says, is that it conducts electricity equally well if it contains many electrons, a handful or only one. Electrons typically bounce off of surrounding contaminants, which slows or stops them. When traveling through silicon, for example, they make it an average of 10 nanometers before scattering.
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2 Comments
Add CommentWhy not use one half of a graphene hourglass as an electrical lead to a nanotube? Hence no bulky wire to attach to the elegant nanotube?
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Sounds like an ideal material to capture and conduct solar energy. GO BLUE!
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