THE INFLUENCE OF SUBSTRATE CRYSTALLINE-STRUCTURE ON DAES PROFILES OF ULTRATHIN SILVER LAYERS ON A CU(001) FACE

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 ene rgies E(p) greater than or equal to 800 eV, the DEAS profiles characte ristic of the substrate structure were observed for a 0.8 ML silver la yer, while for E(p) = 600 eV such a profile was flat. On the other han d, DAES profiles characteristic of the silver layer structure were obs erved for thicker silver films, for E(p) greater than or equal to 600 eV. This can be explained if one takes into account that the Auger ele ctrons are excited in the silver layer by primary electrons and by ele ctrons backscattered in the substrate. The flux of the Auger electrons is determined by the forward focusing and channelling of primary elec trons 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 substra te crystalline structure on the DAES profiles of ultrathin adsorbed la yers. (C) 1997 Elsevier Science Ltd.