INFLUENCE OF CU OVERLAYER ON THE PROPERTIES OF SNO2-BASED GAS SENSORS

The series of gas sensors based on SnO2 thin films and doped with diff erent amount of Cu was prepared by using de magnetron sputtering. The surface properties and chemical composition of the sensors covered wit h Cu and Pt overlayers were studied by XPS, SIMS and optical UV-VIS sp ectroscopy. The electrical conductivity controlled by surface interact ion with gases (CO, H-2, Cl-2) was also investigated experimentally. O btained depth profiles demonstrate that the surface doping with Cu res ults in nearly uniform Cu distribution through the whole thickness of the SnO2, film, while the Pt-doping modifies only the surface of the s ample, The origin of different Cu and Pt distributions in depth and th eir influence to the surface chemical reactions during gas treatments are discussed. The chemical stale of Cu-dopant and its effect to the V alence band (XPS) and optical (W-VIS) spectra are analysed. (C) 1998 E lsevier Science S.A.