Preparation of highly c-axis-oriented Bi₄Ti₃O₁₂ thin films and their crystallographic, dielectric and optical properties

Bismuth titanate (Bi₄Ti₃O₁₂) thin films with a high c-axis orientation up to 99% were prepared on (100)-oriented silicon wafers by r.f. planar magnetron sputtering using a Bi₂TiO₅ ceramic target at a substrate temperature of 600°C. From the Auger electron spectroscopy depth profile of the film, there is no evidence of interdiffusion of a specific element between the film and the substrate. Relative dielectric constant of these films depends on film thickness. The behavior was explained assuming a low-dielectric-constant interface layer. Using this assumption, the relative dielectric constant of Bi₄Ti₃O₁₂ film was estimated to be approximately 140. This value is close to that along the c axis in a bulk form. The remanent polarization and the coercive field were 0.8 μC cm^-2 and 20 kV cm^-1, respectively.