Nanotubes on cloth fire electrons

Researchers from Boston College and Florida International University have found that nanotubes grown on rough surfaces like carbon cloth can be coaxed to emit electrons using extremely low electric fields.

Nanotubes are rolled-up sheets of carbon atoms that can be narrower than a nanometer. A nanometer is one millionth of a millimeter, or 75,000 times narrower than a human hair. The researchers' nanotube-strewn carbon cloth emitted electrons at the extremely low electric field of less than 0.2 volts per micrometer.

The discovery could lead to field emission lamps, x-ray sources and microwave power supplies that use low operating voltages and so would be more efficient and less expensive than current models, according to the researchers. Field emitters use an electric field to cause bits of metal or semiconductor material to emit a stream of electrons.

Key to the surprising and useful electrical property is the disorderly growth of the nanotubes on the rough surface of the cloth, according to the researchers. The nanotubes were bent and contained many defects; these points emit electrons. The nanotubes on carbon cloth formed a more efficient electron emitter than either carbon cloth alone or films of nanotubes.

The method could be used to make flat-panel displays if glass is used as the substrate instead of carbon cloth and the glass surface can be made as rough as the cloth, according to the researchers.

Nanotubes grown on a rough surfaces like carbon cloth could be used practically in two to five years, according to the researchers. The work appeared in the August 2, 2004 issue of Applied Physics Letters.