Structure of the Cl-passivated GaAs(111) surface

Cl $1s$ (K-shell) near-edge and extended x-ray-absorption fine-structure spectroscopy has been used to study the chemistry and structure of the Cl passivated GaAs(111) surface. The Cl passivation is achieved in ambient atmosphere by wet chemical methods. It is found that Cl forms a stable monochloride structure with Cl bonded to Ga. Strong polarization dependence was observed both in the Cl 1→s3p {σ}-resonance and in the extended fine-structure region. Quantitative analysis, including numerical calculations using the multiple-scattering method on an 85-atom cluster, show that the Ga-Cl bond is oriented along the 〈111〉 surface normal with a Ga-Cl bond length of 2.17±0.02.