Adsorption of solvated hydrosulfide ions at a GaAs(100) surface: The role of a solvent in surface structure modification

Adsorption of HS- hydrosulfide ions solvated by different amphiprotic solvents (water, alcohols) at the oxide-free GaAs(100) surface was studied by photoemission spectroscopy. The adsorption was carried out from ammonium sulfide solutions in an inert oxygen-free ambient. In the core-level spectra, the chemical shift of the component stemming from the As-S bonds in reference to the component related to As-Ga bulk emission is shown to increase as the permittivity of the solvent used decreases. This fact points to the increase in the ionicity of forming As-S bonds. The ionization energy of the semiconductor after adsorption also depends on the solvent from which the adsorption occurs. Such a dependence is retained after annealing of the surface and disappearance of the As-S bonds, which indicates that the solvent affects the surface atomic structure. It is shown that the solvent modifies the ion chemical properties and reactivity via solvation, which results in a change in the mechanism of interaction of ions with semiconductor surface atoms. (C) 2004 MAIK "Nauka / Interperiodica".