Growth surface alloy formation of Ag on Pt(111)

Low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and ultraviolet photoelectron spectroscopy (UPS) were used to study the growth mode and the surface structure of a silver ultra-thin film deposited on a Pt(111) surface at 360 K. The AES and LEED results show that the growth of Ag/Pt(111) belongs to the Stranski-Krastanov mode. The growth mechanism is discussed. The electron density of states in the growth process was investigated by UPS. A splitting of Ag 4d_5/2 and Ag 4d_3/2 was observed as the absorbed Ag atoms changed from an atomic state to a solid state. In the LEED study, the intensity of the specular beam versus the surface temperature has an abnormal change and is irreversible between 550 K and 650 K, as the coverage is in the submonolayer range. These phenomena, and the Auger-intensity ratio of Ag and Pt varying with the temperature, show that a two-dimensional surface alloy develops at a temperature above 550 K, as the coverage is within one monolayer.