Prelude to etching: The surface interaction of chlorine on GaAs(110)

The interaction of ${\mathrm{Cl}}_2$ with GaAs(110) was studied with photoelectron spectroscopy at 300 K. The results show that ${\mathrm{Cl}}_2$ dissociates and prefers ${\mathrm{Ga}}^{1+}$ bonding at low coverage and chemically distinct states can be correlated with structural information obtained from scanning tunneling microscopy. This Cl-Ga state was characterized by a distinct surface bonding configuration as Ga atoms lost charge, As atoms gained charge, and the surface bonds became less ${\mathit{sp}}^3$-like. The result was a chemical shift for both Ga and As. Cl-Ga islands developed as the Cl coverage increased and subsequent adsorption of Cl within those islands enabled the formation of Cl-As bonds and an ${\mathrm{As}}^{1+}$ state.