Low temperature synthesis of TiO2/SrTiO3 films on Ti substrate

The low temperature synthesis of TiO2/SrTiO3 films on Ti substrate was examined focusing on the thickness, the adherence and the surface morphology of the films. The Ti substrate is superior to other ones such as glass, ITO etc from the viewpoint of electrical conductivity and formability. An amorphous-like (amo.) TiO2 film was prepared on the surface of Ti substrate by chemical treatment with H2O2/HCl aqueous solution. The thickness of the amo.TiO2 film increased almost linearly with the period of the chemical treatment, it had ranges of up to 1.5-2.0 mu m by the 120min treatment. When the period of chemical treatment was shorter than 60min, which corresponded to the thickness of about 1 mu m, the uniform and adhesive amo.TiO2 film could be obtained on the substrate. The chemical treatment longer than 60min resulted in inducing cracks in the amo.TiO2 film, they became clear by extending the treatment time. By annealing at 773-873K for 60min in air, the amo.TiO2 transformed mainly to the anatase-type TiO2 showing high crystallinity, while a small amount of the rutile-type also appeared. On the other hand, the SrTiO3 film could be obtained on the Ti substrate by annealing the amo.TiO2 coated with Sr(NO3)(2) above 773K in Ar. The adherence of the films was also kept after the heat treatments. The synthesis of such films hardly changed the thickness and the surface morphology. Thus, the TiO2, SrTiO3 films could be easily synthesised at low temperature on the Ti substrate by using the amo.TiO2 film prepared by the chemical treatment. In addition, the formation of TiO2 thin films on the SrTiO3 phase was also discussed.