Stabilization of Co/Pt(111) against surface alloying by Ag overlayers

The initial growth and annealing effects of Ag ultrathin films on the surface of 1 ML Co/Pt(111) were investigated by low-energy electron diffraction (LEED), Auger electron spectroscopy, and ultraviolet photoelectron spectroscopy. The Ag atoms are in a layer-by-layer growth only of the first two atomic layers. Within these coverages, the adatoms of Ag are in instability when the substrate starts Co-Pt alloying. The intensity of the specular beam of LEED versus temperature increases dramatically after the alloy formation is complete. The temperature of the formation of the Co-Pt alloy becomes higher as the coverage of Ag increases. These unusual phenomena are, to our knowledge, the first observation in the systems containing three-component ultrathin films. The stress of overlayers causing the change of the alloying temperature is proposed.