(NH4)2SX-TREATED INP(001) STUDIED BY HIGH-RESOLUTION X-RAY PHOTOELECTRON-SPECTROSCOPY

The chemical state of sulfur on (NH4)2Sx-treated InP(001) surfaces has been studied by high-resolution x-ray photoelectron spectroscopy. We find three kinds of chemical states of sulfur (S2p3/2 lines at 161.2, 162.0, and 163.4 eV) on the sample treated at RT. It is suggested that they correspond to sulfur in phosphorus sites (in the second layer of the InP(001) surface), to sulfur bonded to indium on the first layer, and to elemental sulfur on sulfide, respectively. One (S2p3/2 = 162.0 eV) of them becomes predominant with long-time exposure to atmosphere at RT. Upon annealing the sample at 400-degrees-C, the 163.4 eV line disappears, while the lines at 162.0 and 161.2 eV remain on the surfac e. A model of the treated surface is presented.