Selection-Rule Effects in Electron-Loss Spectroscopy of Ge and GaAs Surfaces

Abstract

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.