Surface electronic structure of submonolayer to full-monolayer coverages of alkali metals on GaAs(110): K and Cs

The development of the electronic structure of two interfaces of alkali metals with semiconductors, K/GaAs(110) and Cs/GaAs(110), has been studied experimentally. Changes in the occupied states have been monitored with ultraviolet photoelectron spectroscopy while the unoccupied states have been investigated using angle-resolved inverse photoemission. It is found that K and Cs behave quite differently on GaAs(110). Potassium induces two surface states, one filled and one empty. The dispersion of the empty state is presented and shows the nonmetallic state of this surface. Cesium, on the other hand, yields an empty state, which beyond saturation exposure moves down to the Fermi level, thus rendering the surface metallic. © 1989 The American Physical Society.