Graphene may be the most remarkable substance ever discovered. But what’s it for? BY JOHN COLAPINTO One atom thick, graphene is the thinnest material known and may be the strongest. One atom thick, graphene is the thinnest material known and may be the strongest. CREDIT ILLUSTRATION BY CHAD HAGEN Until Andre Geim, a physics professor at the University of Manchester, discovered an unusual new material called graphene, he was best known for an experiment in which he used electromagnets to levitate a frog. Geim, born in 1958 in the Soviet Union, is a brilliant academic—as a high-school student, he won a competition by memorizing a thousand-page chemistry dictionary—but he also has a streak of unorthodox humor. He published the frog experiment in the European Journal of Physics, under the title “Of Flying Frogs and Levitrons,” and in 2000 it won the Ig Nobel Prize, an annual award for the silliest experiment. Colleagues urged Geim to turn the honor down, but he refused. He saw the frog levitation as an integral part of his style, an acceptance of lateral thinking that could lead to important discoveries. Soon afterward, he began hosting “Friday sessions” for his students: free-form, end-of-the-week experiments, sometimes fuelled by a few beers. “The Friday sessions refer to something that you’re not paid for and not supposed to do during your professional life,” Geim told me recently. “Curiosity-driven research. Something random, simple, maybe a bit weird—even ridiculous.” He added, “Without it, there are no discoveries.” On one such evening, in the fall of 2002, Geim was thinking about carbon. He specializes in microscopically thin materials, and he wondered how very thin layers of carbon might behave under certain experimental conditions. Graphite, which consists of stacks of atom-thick carbon layers, was an obvious material to work with, but the standard methods for isolating superthin samples would overheat the material, destroying it. So Geim had set one of his new Ph.D. students, Da Jiang, the task of trying to obtain as thin a sample as possible—perhaps a few hundred atomic layers—by polishing a one-inch graphite crystal. Several weeks later, Jiang delivered a speck of carbon in a petri dish. After looking at it under a microscope, Geim recalls, he asked him to try again; Jiang admitted that this was all that was left of the crystal. As Geim teasingly admonished him (“You polished a mountain to get a grain of sand?”), one of his senior fellows glanced at a ball of used Scotch tape in the wastebasket, its sticky side covered with a gray, slightly shiny film of graphite residue. It would have been a familiar sight in labs around the world, where researchers routinely use tape to test the adhesive properties of experimental samples. The layers of carbon that make up graphite are weakly bonded (hence its adoption, in 1564, for pencils, which shed a visible trace when dragged across paper), so tape removes flakes of it readily. Geim placed a piece of the tape under the microscope and discovered that the graphite layers were thinner than any others he’d seen. By folding the tape, pressing the residue together and pulling it apart, he was able to peel the flakes down to still thinner layers. Geim had isolated the first two-dimensional material ever discovered: an atom-thick layer of carbon, which appeared, under an atomic microscope, as a flat lattice of hexagons linked in a honeycomb pattern. Theoretical physicists had speculated about such a substance, calling it “graphene,” but had assumed that a single atomic layer could not be obtained at room temperature—that it would pull apart into microscopic balls. Instead, Geim saw, graphene remained in a single plane, developing ripples as the material stabilized. Geim enlisted the help of a Ph.D. student named Konstantin Novoselov, and they began working fourteen-hour days studying graphene. In the next two years, they designed a series of experiments that uncovered startling properties of the material. Because of its unique structure, electrons could flow across the lattice unimpeded by other layers, moving with extraordinary speed and freedom. It can carry a thousand times more electricity than copper. In what Geim later called “the first eureka moment,” they demonstrated that graphene had a pronounced “field effect,” the response that some materials show when placed near an electric field, which allows scientists to control the conductivity. A field effect is one of the defining characteristics of silicon, used in computer chips, which suggested that graphene could serve as a replacement—something that computer makers had been seeking for years. Geim and Novoselov wrote a three-page paper describing their discoveries. It was twice rejected by Nature, where one reader stated that isolating a stable, two-dimensional material was “impossible,” and another said that it was not “a sufficient scientific advance.” But, in October, 2004, the paper, “Electric Field Effect in Atomically Thin Carbon Films,” was published in Science, and it astonished scientists. “It was as if science fiction had become reality,” Youngjoon Gil, the executive vice-president of the Samsung Advanced Institute of Technology, told me.
Posted on: Fri, 19 Dec 2014 08:16:31 +0000
Trending Topics
Recently Viewed Topics
© 2015