ATHENS,
Ohio — Molecular
electronics is the ultimate miniaturization of electronics.
In this area of research, scientists have been studying
the movement of electrons through individual molecules
in an effort to understand how they might control and
use the process in new technologies. Computers and
thousands of other devices could become vastly faster,
smaller and more reliable than conventional transistor-based
(wire-based) electronics.
A team of Ohio University and Brazilian physicists
has taken another step toward this goal. In the Rapid
Communication section of the Sept. 15 issue of the
journal Physical Review B , the researchers present
a new theory of how electrons interact in a molecule.
In
the new paper, the team describes what happens
to electrons when scientists put two molecules
between electrodes, which are bits of tiny conducting
wire. Existing theoretical models of molecular
electronics take into account that electrons avoid
each other, according to Nancy Sandler, Ohio University
assistant professor of physics and astronomy. The
scientists report that molecular vibrations, in
addition to strong electronic interactions, will
produce unexpected “transport
channels.” The electrons move through the molecule
while the molecule vibrates, said Sergio Ulloa, co-author
of the paper and Ohio University professor of physics
and astronomy.
“The electrons go through the molecule like a pinball
and they leave all the bells ringing (atoms moving)
as they pass by,” said Ulloa, adding that this model
focuses on the general behavior of short molecules.
Other scientists studying molecular electronics,
he noted, are using longer molecules, such as DNA
or carbon-based molecules, to serve as longer “wires” or
connectors.
The
collaborators on this project – which included
Ulloa, Sandler, Brazilian exchange student Edson
Vernek and professor Enrique Anda of the Pontifícia
Universidade Católica in Rio de Janeiro, Brazil – describe
another fascinating capability of the electrons: “The
electrons ‘remember' not only where they are, but
where they have been,” Ulloa said. “When the oscillations
of the molecules are ‘just right,' the electrons
are either pushed through more efficiently or trapped
momentarily in the molecule – a phenomenon physicists
call ‘Rabi-assisted tunneling.' The electrons can
really get trapped, like in the pinball machine.”
This
electron “trapping” could
make molecular transmission even more efficient
and help develop molecular switches and other applications.
Molecular electronics is a booming field in physics
right now. Scientists have been able to manipulate
molecules for only last 15 years, Sandler said, and
it may be at least another 20 years before consumers
see molecular technology in commercially available
devices.
The
research collaboration between Ohio University,
the Pontifícia Universidade Católica
in Rio de Janeiro, Brazil, and the Universidad de
Buenos Aires, Argentina, is supported by the National
Science Foundation through the project “Correlation
Effects and Transport in Nanostructured Materials.” The
Brazilian Coordination of Improvement of the Personnel
of Superior Level (CAPES) supported Vernek's visit
to Ohio University.
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