Resonant inverse-photoemission study of layer-dependent surface states at the epitaxial GaAs(110)-Bi interface

Abstract

The unoccupied electronic structure of the ordered GaAs(110)1\ifmmode\times\else\texttimes\fi{}1-Bi system has been studied with use of inverse photoemission. In the Bi-coverage range from 1 to 2 monolayers, two unoccupied electronic surface states are observed, 0.9 and 1.9 eV above the valence-band maximum of GaAs at \ensuremath{\Gamma}. From their coverage-dependent intensities, they are assigned to the outer (Bi-Bi) and inner [Bi-GaAs(110)] interfacial layers, respectively. The states are characteristic of the bilayer and vanish for thicker, bulklike Bi films. A resonant enhancement of these two states, and an additional image state, is observed when the energy of the emitted photon coincides with the plasmon energy.