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Phoenix666 writes:

At the University of Zurich, chemists have ... synthesised organometallic molecular structures endowed with individual metal atoms of iron, ruthenium or molybdenum. These designer molecules, which are only around two and a half nanometres long, are then carefully connected using two gold contacts at the IBM research lab in Rüschlikon before voltage can be applied to them.

For one of the molecule types tested, which has a molybdenum atom placed at its core, some quite remarkable properties were observed: similarly to a silicon transistor, this molecule switches back and forth between two different states, which differ by three orders of magnitude as regards their conductivity. Complex computer simulations were required in order to understand the underlying process; these were carried out by Robert Stadler and his doctoral student Georg Kastlunger at the Vienna Scientific Cluster (VSC). This allowed the mechanism to be decoded at a quantum physical level.

"Directly on the molybdenum atom there is a certain space which can be occupied by an electron," says Robert Stadler. "The amount of current that can flow through the molecule at a certain voltage depends on whether or not there is actually an electron occupying this space or not." And this in itself can be controlled. If the space is occupied, relatively little current will flow at a low voltage. At a higher voltage, however, the electron can be dislodged from its special place on the molybdenum atom. As a result, the system switches to a new state with conductivity improved by a factor of around a thousand, causing a sharp increase in the current flow. Both a switching and selection process can therefore be carried out via the two gold contacts, between which the molecule is fixed. A third electrode, as is usually required for a conventional transistor, is no longer necessary, which simplifies the wiring process significantly.
...
organic molecules with integrated metal atoms can lead the way to ultra-small switches for new storage systems; in any case, there is the potential for exciting applications, particularly since the omission of the third electrode allows for unrivalled integration densities."

The organic molecule is thought to potentially replace conventional transistors.

Field-induced conductance switching by charge-state alternation in organometallic single-molecule junctions

Original Submission