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
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.
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