Saturday, February 4, 2012


Anyone want to reproduce a Nobel Prize-winning experiment? The materials list is quite extensive: a pencil and scotch tape. A pencil contains graphite, which consists of sheets of carbon in a hexagonal lattice. When you write on the sticky side of the tape, layers of graphite slide off the tip of the pencil and stick to the tape. 

The atomic structure of graphite. One sheet of graphite,
when isolated, is known as graphene.

   By folded the tape in half, you will cleave the flakes of graphite when you open it back up. If you repeat this procedure a few times you will create increasingly thin layers where some will be only a single atom thick. You have created graphene.
   Graphene is the thinnest material known to man. Not only that, it is the strongest. It conducts electricity as well as copper and it is also the best thermal conductor. 
   In 2004, Konstantin Novaselov and Andre Geim created graphene using this technique known as micromechanical cleavage. Their success was quite unexpected because it was thought a single layer of graphite would not be chemically stable. In 2010, Novaselov and Geim were awarded the Noble Prize in physics for their discovery. Apparently, creating a two-dimensional crystal is a big deal!
   Graphene conducts electrons faster than any other substance at room temperature, 100 times faster than silicon. This is because of the extraordinarily high quality of the graphene lattice where the atoms line up so regularly that there is not a single atom out of place. With no defects in the hexagonal lattice, the electrons do not scatter. They travel so fast that relativity must be used to fully understand how they move. The carbon atoms in the lattice create very strong yet flexible bonds, making graphene bendable and 200 times stronger than steel by weight.
   Welcome to nanotechnology, where very tiny devices are less than 100 nanometers in size. A nanometer is a billionth of a meter (1 nm = 1/1,000,000,000 m). That is roughly the size of 10 atoms. Scientists are exploring graphene’s unique material properties to create thin, mechanically tough, electrically conducting, transparent films. Such films are badly needed in a variety of electronics applications from touch screens to solar cells. We will finish up our discussion of graphene and other possible applications in next week’s column.

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