A reversible molecular switch based on pattern-change in chlorobenzene and toluene on a Si(111)-(7x7) surface.

A reversible molecular switch is proposed, based on an observed change in a physisorbed pattern of chlorobenzene or toluene at Si(111)-(7 x 7), from "triangles" to "circles". Electronic excitation, at an applied surface voltage of V s = -2.0 V, caused molecular migration, by one atomic site, from under the tip (switch "off"). Thereafter, the adsorbate pattern reverted thermally from circles to triangles (switch "on") across a measured activation barrier of E a = 0.3 eV for chlorobenzene and 0.2 eV for toluene.