Nanotube diode reverses itself

Researchers from GE Global Research Center have constructed from a single carbon nanotube a device that restricts the flow of electricity to a single direction and can electrically switch from one direction to the other.

Carbon nanotubes are rolled-up sheets of carbon atoms that can be narrower than a nanometer. A nanometer is one millionth of a milliliter, or the span of 10 hydrogen atoms.

This minuscule p-n junction diode could be used as a field-effect transistor or a light-emitting diode. The device is a step forward in the push to make nanoscale electronic components, which promise to be faster and lower-power than today's larger versions.

The device is made from a single-walled nanotube connected to electrodes at either end and with gate electrodes positioned beneath either end. Sending positive current to a gate electrode creates a positive electric field around a portion of the nanotube, making that area of the tube draw negatively charged current from the far contact electrode.

Electronic components are usually modified using chemicals rather than an electrical field; the chemical method is difficult to do with carbon nanotubes, according to the researchers.

Discrete electronic or sensor components made from the nanotube devices could be used practically within a few years, but it is likely to be a decade or more before nanotube devices can be used for electronic applications that require millions of interconnected components, according to the researchers. The work appeared in the July 5, 2004 issue of Applied Physics Letters.