AES observation of electron-beam-induced layer formation on ZnS in the presence of water vapor

Electron-beam-induced formation of a reacted layer was observed on a ZnS (110) cleaved surface. The layer was formed in the presence of 6.7×10 ^-6 Pa of water vapor. The layer was studied by Auger electron spectroscopy (AES) using an electron-beam energy and current density of 3 keV and 1.4×10^-2 A/cm², respectively. An approximately 200-Å-thick reacted layer was grown after 40 min exposure to the electron beam. Oxygen diffusion into the bulk during the formation was found. The oxygen diffused layer was twice as thick as the initially formed layer. The zinc concentration beneath the layer was 3% less than that of the original cleaved surface. The disappearance of characteristic energy loss structures indicated the reduction of ZnS bonds in the layer. The formed layer may play an important role in the surface degradation process of the ZnS phosphors.