An AES, XPS and TDS study on the growth and property of silver thin film on the Pt(1 1 0)-(1×2) surface

Silver thin film growth on the Pt(1 1 0)-(1×2) surface was investigated by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and CO thermal desorption spectroscopy at various temperatures. At room temperature, the silver thin film growth follows the Stranski–Krastanov mode, i.e., layer-by-layer growth up to 1.5 monolayer (ML) followed by 3D island growth. During the initial 1.5 ML layer-by-layer growth, the first 0.5 ML silver atoms fill in the missing-row sites of the Pt(1 1 0)-(1×2) surface and form a pseudo Pt(1 1 0)-(1×1)–0.5 ML Pt–0.5 ML Ag surface structure, then the subsequent and the last 0.5 ML silver atoms grow on the Ag sites and the Pt sites of the pseudo (1×1) surface, respectively. AES and XPS results reveal that the 3D Ag islands are not so stable as the 1.5 ML silver thin film. It is also found that interactions occur between Pt and Ag, in which electrons are transferred from Pt to Ag, causing the Ag 3d binding energy to shift to the lower binding energy, compared with that of bulk silver. At 600 K, the formation of surface Ag–Pt compound follows the 2.25 ML layer-by-layer growth of the silver thin film on Pt(1 1 0)-(1×2).