Nanotube shines telecom light

Researchers are continually working to expand the usefulness of carbon nanotubes -- rolled-up sheets of carbon atoms found naturally in soot.

Scientists from IBM Research have found a way to make the microscopic tubes emit light, and have fashioned a nanotube transistor that emits 1.5-micron infrared light, a wavelength widely used in telecommunications.

Nanotubes can be smaller than one nanometer in diameter, and show promise as building blocks for fantastically small electronics and machines. A nanometer is one millionth of a millimeter, or about the length of a line of 10 hydrogen atoms.

Carbon nanotubes have already been used as wires to carry electricity and transistors to control electric current. Light-emitting nanotubes could be used to form efficient communications devices and, eventually, all-optical computer chips.

The researchers found that if they inject electrons, which carry negative charges, into one end of a nanotube, and holes, or positive charges, into the other end, the two combine to emit light whose wavelength is inversely proportional to the tube's diameter.

It will be about a decade before infrared nanotubes are used in practical devices, according to the researchers. The work is slated to appear in the the May 2, 2003 issue of Science.