Surface analysis of the nanostructured W-Ti thin film deposited on silicon

The W-Ti thin films are deposited by the dc Ar+ sputtering of W(70%)-Ti(30%) a.t. target on silicon substrates. The surface composition and structure of the thin film, previously exposed to air, was carried out. The surface structure was undertaken using grazing incidence X-ray diffraction (GIXRD), and compared to that of the thin film interior. The surface morphology was determined by the Scanning Tunneling Microscopy (STM). The surface composition and chemical bonding of elements on the Ti-W film were analyzed by X-ray photoelectron spectroscopy (XPS) and Low Energy Ion Scattering (LEIS). The measurements show that the overlayer of metallic oxides TiO2 and WO3 is formed. The first atomic layer is occupied by TiO2 only, and its thickness is estimated to about 3.2 ± 0.4 nm. The strong surface segregation of Ti is triggered by the surface oxidation, which is confirmed by the thermodynamical considerations.