Soft X-ray photoemission studies of S/InP(100)

High-resolution soft X-ray photoemission spectroscopy has been applied to study the clean and H2S-covered InP(100) surface. The clean surface is In-rich and forms a (4 x 2) reconstruction. The In 4d core levels and the P 2p levels show surface shifts which in general terms are consistent with existing models [1]. The P 2p level shows only a small surface shift, suggesting that most atoms are in a bulk-like configuration. The In 4d peak shows three surface and subsurface peaks and one bulk peak whose energies are extracted by fitting. When hydrogen sulphide is adsorbed, and the surface then annealed, a single sulphur peak is observed. The small shift of the P 2p core level is not changed significantly in contrast with the In 4d surface peaks, which change their energy and relative intensity, indicating that the sulphur adsorbs predominantly on the metal sites.