Scientists with the Ernest Orlando Lawrence Berkeley National Laboratory have confirmed the existence of atom-sized electronic devices on nanotubes, hollow cylinders of pure carbon about 50,000 times more narrow than a human hair in diameter. Nanotube devices have been predicted by theorists but this is the first demonstration that such devices actually exist. Alex Zettl, a physicist with Berkeley Lab's Materials Sciences Division (MSD) and a professor of physics on the University of California's Berkeley campus, led a study in which nanotubes of pure carbon were shown to function as a two-terminal electronic device known as a diode. "What we are seeing is the world's smallest room-temperature rectifier, one that is only a handful of atoms in size," says Zettl. "When we grow nanotubes, electronic devices naturally form on them." Carbon nanotubes are created by heating ordinary carbon until it vaporizes, then allowing it to condense in a vacuum or an inert gas. Depending upon its diameter, a pure carbon nanotube can conduct an electrical current as if it were a metal, or it can act as a semiconductor. Zettl does not expect nanotubes to replace silicon overnight in the electronics industry but can see this as a possibility down the road. For more information, e-mail Lynn Yarris at firstname.lastname@example.org.