Adsorption of H2S on InP(001) studied by photoemission spectroscopy

Adsorption of H2S on InP(001) at 140 K has been studied by valence-band and core-level synchrotron-radiation-induced photoemission spectroscopy (SRPES). Peaks were found in the SRPES spectra after the H2S exposure at EF -6.7, -9.4, and -12.4 eV upon adsorption of H2S. They correspond to the 2b1, 5a1, and 2b1 orbitals of H2S gas, considering the intensity ratios and energy separations. This indicates that H2S adsorbs molecularly on the surface at 140 K. We find two kinds of chemical state for sulfur: S2p at 162.0 and 160.8 eV for H2S strong interaction with surface In atoms and physisorption, respectively. This is consistent with the changes in S2p and In4d spectra upon adsorption of H2S. Phosphorus atoms on the surface are scarcely interacting with H2O.