http://www.physorg.com/news111683757.html

Good vibrations in nanotube research

IBM scientists have measured the distribution of electrical charges in tubes
of carbon that measure less than 2 nanometers in diameter, 50,000 times
thinner than a strand of human hair. This novel technique, which relies on
the interactions between electrons and phonons, provides a detailed
understanding of the electrical behavior of carbon nanotubes, a material
that shows promise as a building block for much smaller, faster and lower
power computer chips compared to today's conventional silicon transistors.
Credit: IBM

IBM scientists have measured distribution of electrical charges in tubes of
carbon that measure less than 2 nanometers in diameter, 50,000 times thinner
than a strand of human hair. The technique provides a better understanding
of the electrical behavior of carbon nanotubes, a material that could lead
to smaller, faster and lower power computer chips.
IBM scientists today announced that they have measured the distribution of
electrical charges in tubes of carbon that measure less than 2 nanometers in
diameter, 50,000 times thinner than a strand of human hair.

This novel technique, which relies on the interactions between electrons and
phonons, provides a detailed understanding of the electrical behavior of
carbon nanotubes, a material that shows promise as a building block for much
smaller, faster and lower power computer chips compared to today's
conventional silicon transistors.

Phonons are the atomic vibrations that occur inside material, and can
determine the material's thermal and electrical conductivity. Electrons
carry and produce the current. Both are important features of materials that
can be used to carry electrical signals and perform computations.

The interaction between electrons and phonons can release heat and impede
electrical flow inside computer chips. By understanding the interaction of
electrons and phonons in carbon nanotubes, the researchers have developed a
better way to measure their suitability as wires and semiconductors inside
of future computer chips.

In order to make carbon nanotubes useful in building logic circuitry,
scientists are pushing to demonstrate their high speed, high packing density
and low power consumption capabilities as well as the ability to make them
viable for potential mass production.

"The success of nanoelectronics will largely depend on the ability to
prepare well characterized and reproducible nano-structures, such as carbon
nanotubes," said Dr. Phaedon Avouris, IBM Fellow and lead researcher for
IBM's carbon nanotube efforts. "Using this technique, we are now able to see
and understand the local electronic behavior of individual carbon
nanotubes."

To date, researchers have been able to build carbon nanotube transistors
with superior performance, but have been challenged with reproducibility
issues. Carbon nanotubes are sensitive to environmental influences. For
example, their properties can be altered by foreign substances, affecting
the flow of electrical current and changing device performance. These
interactions are typically local and change the density of electrons in the
various devices of an integrated circuit, and even along a single nanotube.

A better understanding of how the local environment affects the electrical
charge of a carbon nanotube is needed to allow the fabrication of more
reliable transistors. Therefore, the ability to measure local electron
density changes in a nanotube is essential. A team of researchers from the
IBM's T.J. Watson Research Center in Yorktown Heights have just solved this
problem.

This achievement was published online October 14, 2007 in the journal Nature
Nanotechnology. The team monitored the color of the light scattered from the
nanotube (Raman Effect), and measured small changes in the color of the
light corresponding to changes in the electron density in the nanotube. The
technique takes advantage of the interaction between the motion of the atoms
and the motion of the electrons, so that electron density changes can be
reflected in changes of the frequency of the vibrational motion of the
nanotube atoms.

In March 2006, IBM announced that its researchers built the first complete
electronic integrated circuit around a single carbon nanotube molecule.

Source: IBM

-- 

Ken

"Buddhism elucidates why we are sentient."
"Buddhism follows thought throughout the Universe."
"Karma means that you don't get away with anything."