Effect of annealing of Ag ultrathin films on Co/Pt(111) surface

Low-energy electron diffraction was used to study the annealing effects of Ag ultrathin films on the surface of one monolayer Co/Pt(111). The intensity of the specular beam versus temperature has an unusual minimum point and maximum point. Further studies by Auger electron spectroscopy indicate that the adatoms of Ag become a best ordered state after the formation of Co-Pt alloy is complete. The new order state comes from the structure change of Co/Pt(111) and the smaller lattice mismatch between Ag and Pt. The electron density of states of d band shifts to a lower binding energy when the system starts to form the Co-Pt alloy measured by ultraviolet photoelectron spectroscopy. The chemical compositions at interfaces of the thin film were investigated by a depth profile before and after the annealing. The sputtering rates of Ag on the topmost layer of the unannealed film and the annealed film were calculated and comparatively studied. A shadow effect causes the different sputtering rates of these two ultrathin films.