Modification of surface properties of SnO2 gas sensor by Cu and Pt overlayers

The surface properties and chemical composition of SnO2 thin film gas sensors modified with Cu and/or Pt overlayers were studied by XPS, AES, SIMS and optical UV-VIS spectroscopy. The electrical conductivity controlled by surface interaction with gases (GO, H-2, Cl-2) was also investigated experimentally. Obtained depth profiles demonstrate that the surface doping with Cu results in nearly uniform Cu distribution through the whole thickness of SnO2 film, whilst the Pt-doping modifies only the surface of the sample. The origin of different Cu and Pt distributions in depth and their influence to the surface chemical reactions during gas treatments are discussed. The chemical state of Cu-dopant and its effect to the valence band (XPS) and optical (UV-VIS) spectra is analysed.