Selection-rule effects in electron-loss spectroscopy of Ge and GaAs surfaces

Low-energy electron-loss spectroscopy on Ge and GaAs surfaces reveals opticlike selection-rule behavior for transitions involving d-core states and empty dangling-bond surface states. From the observed breakdown of these rules at low incident primary electron energies the symmetry of the dangling-bond states may be estimated. The Ga dangling bond is found to be largely s like on all surfaces, whereas the Ge dangling bond exhibits p-like character on the (111)-(8×8) surface, and mixed s-p character on the (100)-(2×2) surface. © 1975 The American Physical Society.