Electron Energy-Loss Spectroscopy of GaAs and Ge Surfaces

Abstract

The energy-loss spectra of ∼ 100-eV electrons were measured for (100) and ($\overline{1}\overline{1}\overline{1}$) GaAs and (111) Ge surfaces. The portion of the energy-loss spectra attributed to excitations of $d$ electrons is proportional to the density of states in the conduction bands and empty surface states. The GaAs surfaces stabilized into Ga-rich and As-rich conditions permit unambiguous identification of intrinsic surface states. Empty and filled surface states, attributed to dangling Ga and As bonds, are observed near the conduction-band and valence-band edges, respectively.