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PhysicsWeb - Single-electron transistor goes mechanical

PhysicsWeb - Belle Dume

Physicists in Germany and the US have built a single-electron transistor that operates using a nanometre-scale vibrating arm.

The device was built using a simple two-step process and does not need a surrounding cooled to cryogenic temperatures like previous devices of its kind. It could have a wide variety of practical applications and could also be used to study fundamental physics.

The transistor is a type of device known as a nanoelectromechanical system, or NEM. Unlike conventional electronic devices, NEMs can be potentially routinely manufactured to high tolerances on the scale of nanometres (10-9m), an important attribute in the quest to build ever smaller logic devices. Moreover, NEM devices can operate at and beyond radio frequencies making them ideal for applications in information technology.

The transistor, built by Dominik Scheible at the Ludwig-Maximilians University in Munich and Robert Blick at the University of Wisconsin-Madison, features a silicon arm about 200 nanometres long and only tens of nanometres across. The researchers covered the tip of the device with a gold "island" and then placed the tip between two electrodes, known as the source and drain. By applying an ac voltage to one of the electrodes with a frequency that matched the resonant frequency of the arm -- in this case between 350 and 400 megahertz -- they were able to make the arm vibrate between the electrodes. This resulted in a flow of electrons from the source to the island, from where the electrons then tunnelled towards the drain electrode.

The scientists say the device could have greater practical application than previous NEM transistors, which needed to be excited using high magnetic fields rather than an ac voltage. These fields were produced by superconductors that were kept very cold using liquid helium. In fundamental physics, the device could be used to study the mechanically-controlled transport of single electrons, and so potentially improve our understanding of how materials behave on the nanoscale.

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