ADSORPTION OF H2S ON GAP(001) SURFACE AND PASSIVATION EFFECTS STUDIEDBY AES, LEED AND XPS

Adsorption of H2S on the GaP(001)-(4 x 2) clean surface and passivatio n of the surface to oxidation have been studied using Auger electron s pectroscopy (AES), low energy electron diffraction (LEED) and X-ray ph otoelectron spectroscopy (XPS). The amount of sulfur adsorbed on the s urface is increased by electron-beam irradiation. It is suggested that the increase is caused by activation of H2S and the breaking of Ga-P bonds. The multi-layers of sulfur on the surface are formed during the irradiation. Three kinds of chemical states of adsorbed sulfur at the multi-layers are suggested to correspond to a S-Ga bond at the first and second layers, and a S-S bond. The surface with a (1 x 1) structur e and with multi-layers of sulfur are reconstructed to a (1 x 2) struc ture by annealing at about 450 and 600 degrees C, respectively. It is found that the amount of oxygen adsorbed on a GaP(001)-(1 x 2)S surfac e is much lower than on the clean surface, which implies that the GaP( 001) surface is well passivated by H2S adsorption.