Credit: © 2007 AAAS

As wires and surfaces shrink in size to the nanoscale, their electronic properties become increasingly sensitive to the displacement of just a few atoms. Unfortunately, the movement of atoms may be difficult to control in a useful manner. Now, Fumio Komori and colleagues1 from the University of Tokyo, Spring-8 and Tottori University in Japan show that they can make an atomic switch by manipulating the tilt of atoms on a germanium surface.

The atoms on a clean germanium surface cluster into pairs — or dimers — that are tilted with respect to the surface. A row of these dimers acts as a one-dimensional conducting pathway for electrons. When a sparse layer of tin atoms is deposited on the surface, the tin replaces some of the germanium sites in the dimers. The Japanese group shows that the tilt of a tin–germanium dimer can be reversed by applying a voltage to a scanning tunnelling microscope tip right above the tin atom, effectively opening or blocking conduction through the row of dimers.

This 'seesaw' switch is unlike conventional atomic switches because it does not require the mass transport of atoms. It is also one of only a few examples where scanning probe microscopy can 'see' the mechanism for conduction switching.