Electron energy-loss spectroscopy of GaAs and Ge surfaces

The energy-loss spectra of ∼ 100-eV electrons were measured for (100) and (1̄1̄1̄) 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. © 1974 The American Physical Society.