Adsorption and Surface Potential of Semi-conductors. Part 1.

Photo-enhanced Adsorption of Oxygen and Change of Contact Potential of ZnS Phosphors with Illumination

Abstract

When ZnS phosphor containing 10⁻² Mol% of Cu was irradiated in oxygen gas by light with wavelengths lying within the characteristic absorption band of the host crystal, photo-enhanced adsorption and increase of the surface potential (decrease of the work function) of the crystal were observed. If we assume that the lowering of the potential energy of adsorption of oxygen is equal to the increased amount of surface potential, the photo-enhanced adsorption can be explained semi-quantitatively. The change of the surface potential of ZnS with illumination, (Δc.p.)_L, increased with pressures of oxygen and decreased with temperature.