An Electromechanical Transistor

An electromechanical transistor (EMT) developed at the University of Munich shuttles a single electron from one electrode to another at 100 MHz rates. There was a time when solid state devices, in which only electrons are moving, were preferable to mechanical devices with lots of moving parts. But this attitude is changing as new advances come about in the field of nanomechanical systems (NEMS).

Artur Erbe (artur.erbe@physik.uni-meunchen.de, 49-89-2180-3349) and his colleagues have succeeded in placing a metal island atop a swinging silicon pendulum oscillating at radio frequencies between two other electrodes. One can think of the pendulum as the clapper of a bell resonating at a frequency of 100 MHZ, or the whole device as a transistor in which a single electron is being shoveled from a "source" electrode to a "drain" electrode.

The Munich setup may afford a new way of establishing a high-precision current standard since although somewhat slower than some other single electron transistors (SET) it allows the single electron only one way (riding on the moving island) of getting from one electrode to the other, in comparison to other metallic SETs in which the electron can tunnel in a variety of paths, a habit which actually lowers the effective control one has over the electron. With the mechanical approach to transferring single electrons, the high sensitivity to environmental conditions may allow the SET to serve as an ultra-sensitive position, gas, or force sensor. (Erbe et al., Physical Review Letters, 27 August 2001.)