Dissociative and selective adsorption of H2S on the GaAs(001)-(4x2) surface

The adsorption of H2S on the GaAs(001)-(4x2) surface has been studied using high-resolution electron energy loss spectroscopy and temperature-programmed desorption. The H2S adsorption is predominantly dissociative at 100 K, producing mercaptan (HS-) and H- species, the latter of which are bonded only to As. After annealing to 700 K, vacant gallium sites, which are available for further sulfur chemisorption, are monitored by post-exposure of atomic hydrogen. Several cycles of H2S exposure and thermal annealing build up more S-Ga bonding on the surface and yield a completely sulfur-saturated layer on which only sulfur is available for post-hydrogenation. (C) 1996 American Institute of Physics.