The reigning darling of nanotech, and researchers' favorite form of carbon for the past decade, has been the nanotube. Lauded as an easy conduit for electricity, this slender, chicken wire–like roll of atoms had conjured dreams of ultraminiature circuitry that might someday stand in for silicon as the workhorse of computer technology.
But nanotubes always had their drawbacks: difficult to arrange precisely, they are also hard to wire to the outside world without losing much of their vaunted electrical conductivity.
Now a new carbon jewel has the caught the eyes of nanotech researchers, some of whom are already speculating that it might pick up where nanotubes left off in their bid to be the savior of electronics.
Oh, and by the way, you can make it with Scotch tape.
Called graphene, it is essentially a nanotube unrolled—a single layer of atoms arranged like a honeycomb. The difference may sound cosmetic, but when the goal is manipulating things that are a few atoms thick, going from tube to sheet makes a big difference.
Although graphene, too, faces many obstacles on the road to applications, its combination of exotic physics and high-tech potential is attracting scores of researchers. "For the moment there is at least a big hope that graphene might be the future," says physicist Andre Geim of the University of Manchester in England, who first isolated it in 2004.
The Great Carbon Hype
Today, Intel and other manufacturers stamp out microchips from dinner plate–size silicon wafers. By creating ever more detailed stamps, they cram chips with increasing numbers of the tiny switches known as transistors. But researchers believe that once silicon circuits slim down to 10 nanometers, which the semiconductor industry predicts will occur after 2020, they will start leaking electricity profusely. Already this year Intel and IBM announced that they would begin adding new materials to counteract leaky currents in their upcoming 45-nanometer transistors.
The question is what material comes next. Many have preened for the role. Graphene, like the carbon nanotube, meets the first requirement: it is a snappy conductor of electricity—better than many semiconductors. As in the nanotube, each carbon atom has three neighbors and an unused electron that is free to skitter around, hence conduction.
But nanotubes grow in dense thickets that are hard to separate and place with precision. To create circuits from them, researchers must attach relatively bulky wires that spoil much of their conductivity. "Carbon nanotube integrated electronics was hyped from the start," says nanotube-cum-graphene researcher Walter de Heer of the Georgia Institute of Technology. "Graphene is different."
With graphene, researchers envision stamping out circuits from large wafers, much as they already do with silicon. But perfecting those wafers has proved challenging. Another long-term "if," Geim says, is whether graphene can be carved into small pieces that actually work. But researchers are just learning. "Strictly two-dimensional materials didn't exist until 2004," he says.
Spite Turns Concept into Reality
As a concept, graphene is nothing new. A piece of graphite is simply a stack of graphene layers loosely stuck to each other, like a deck of cards. That is why scraping a pencil point across paper leaves a mark; the layers flake off in chunks and become caught in the paper fibers. And researchers had always thought of nanotubes as rolled up graphene sheets.
But most assumed that isolating a single pristine layer would be impossible. If the strain of being peeled from its neighboring layers did not shred it, they figured, its own heat would crumple it like newspaper on a campfire.
Nevertheless, some were game to try. Physicist Philip Kim of Columbia University began trying to flake off graphene layers in 2002 by dragging a tiny graphite rod with an atomic force microscope, which is like an exquisitely sensitive phonograph needle. In 2003 de Heer at Georgia Tech received a grant from chipmaker Intel to cook up graphene from a mix of silicon and carbon.