AN OPTICAL AND ELECTROCHEMICAL INVESTIGATION OF ZRO2 THIN-FILMS (FROMNM TO MM THICKNESS)

Zirconium dioxide thin films and yttria stabilised zirconia (YSZ) thin films prepared by various techniques were characterised by optical an d electrochemical techniques. Zirconium oxide films were prepared anod ically (2-250 nm) and by sputtering (0.3-3 mum). YSZ films were prepar ed by a CVD/EVD process (approximately 3 mum), by electrophoretic depo sition (200 mum) and by tape casting (130 mum). These YSZ films are co mpared to single crystal YSZ. Characterisation techniques include phot oelectrochemistry (for the anodically prepared films), transmittance a nd reflectance spectroscopy, and impedance spectroscopy. From the phot oelectrochemical studies, the changes in the bandgap were followed for films prepared under increasing electric fields. The transmittance an d reflectance spectra yield information about the film thickness (for thin films) and for thicker films, information was collected about the relative quantity of localised states and their position in the bandg ap; both for the bulk material and the surface. Impedance spectroscopy for thin films of ZrO2 can be used to determine their dielectric prop erties. For thicker YSZ films at low temperatures (less than 500 K), i mpedance experiments were used to gain information about the intra-gra in, inter-grain, and polarisation resistances.