A chemical-state-resolved x-ray standing-wave analysis using the chemical shift in photoelectron spectra was performed for a GaAs(001) surface treated with a (${\mathrm{NH}}_4$${)}_2$${\mathrm{S}}_{\mathit{x}}$ solution. The sulfur atoms in the S-Ga chemical state on the surface are at the bridge site but are not highly ordered. The degree of ordering of the sulfur atoms in the S-Ga chemical state is improved, and randomly distributed sulfur atoms in the S-As and S-S chemical states disappear as a result of post annealing.

• Received 21 December 1994

DOI:https://doi.org/10.1103/PhysRevB.51.14778