SURFACE RECONSTRUCTION OF INP(001) UPON ADSORPTION OF H2S STUDIED BY LOW-ENERGY-ELECTRON DIFFRACTION, SCANNING-TUNNELING-MICROSCOPY, HIGH-RESOLUTION ELECTRON-ENERGY-LOSS, AND X-RAY PHOTOELECTRON SPECTROSCOPIES

Reconstruction of an InP(001) surface structure upon H2S adsorption ha s been studied by low-energy electron diffraction (LEED), scanning tun neling microscopy (STM), high-resolution electron energy loss (HREELS) , and x-ray photoelectron spectroscopies (XPS). The HREELS result indi cates that H2S is dissociated on the surface even at RT, leading to ev olution of hydrogen from the surface. LEED patterns show (2x4) and (2x 1) structures for the surface with sulfur coverages, 0 and 0.5-1 ML, r espectively. A complex pattern appears at 0.25 ML. We find in STM imag es that the (2x1) structure starts to form even at 0.1 ML sulfur cover age at 350 degrees C. The (2x1) structure is almost established at 0.5 ML although the protrusions of about two atoms in size exist on the s urface. The new (2x1) structure begins to grow from protrusions above 0.5 ML on the (2 x 1) surface found at 0.5 ML and it is established at about 1 ML where the c(2 x 2) structure with small domain is found. X PS result shows one chemical state of sulfur at 0.55 ML with the bindi ng energy (BE) at 161.8 eV. Above 0.55 ML, S 2p spectra contain two co mponents with the BE at 161.8 and 162.2 eV. Based on the angle depende nce of the spectrum and the result of the STM images, these can be asc ribed to sulfur on and under the surface, respectively. Sulfur is foun d not to be bonded to phosphorus atoms at 350 degrees C. (C) 1998 Amer ican Institute of Physics.