(NH${}_4{)}_2{\mathrm{S}}_x$-treated InAs(001) surface studied by x-ray photoelectron spectroscopy and low-energy electron diffraction

The chemical state of sulfur on (NH${}_4{)}_2{\mathrm{S}}_x$-treated InAs(001) and thermal stability of the surface have been studied by high-resolution x-ray photoelectron spectroscopy and low-energy electron diffraction. We find sulfur bonded to In and As atoms but no elemental sulfur for the as-treated surface. The binding energies of S $2p$ for sulfur bonded to In and As are very close. Only one chemical state in sulfur bonded to In is found, in contrast with treated GaAs(001), GaP(001), and InP(001) with two. The sulfur bonded to As atoms is desorbed upon annealing the sample at $300°$C in a vacuum. A diffuse $(1\mathrm{}\times 1)$ surface observed on the as-treated sample is reconstructed to a $(2\mathrm{}\times 1)$ structure upon annealing at $350°$C, which is different from a $(1\mathrm{}\times 2)$ structure for GaP(001) and InP(001).