The influence of substrate crystalline structure on DAES profiles of ultrathin silver layers on a Cu(001) face

Abstract

The influence of the substrate crystalline structure on DAES profiles for ultrathin silver (111) layers deposited on a Cu(001) substrate was investigated. For Ag MNN Auger electrons and for primary electron energies E P ≥ 800 eV, the DEAS profiles characteristic of the substrate structure were observed for a 0.8 ML silver layer, while for E P = 600 eV such a profile was flat. On the other hand, DAES profiles characteristic of the silver layer structure were observed for thicker silver films, for E P ≥ 600 eV. This can be explained if one takes into account that the Auger electrons are excited in the silver layer by primary electrons and by electrons backscattered in the substrate. The flux of the Auger electrons is determined by the forward focusing and channelling of primary electrons in the substrate. For E P = 600 eV the backscattering factor is close to unity and only the primary electrons are responsible for the Auger electron emission from the overlayer. Thus, as low as possible energies E P should be used to eliminate the influence of the substrate crystalline structure on the DAES profiles of ultrathin adsorbed layers.