The influence of structure on the piezoelectric properties of BaTiO 3 and (BaSr)TiO 3 thin films with a diffuse phase transition

Abstract

Polycrystalline thin films of BaTiO 3 and (BaSr)TiO 3 in the thickness range d w = 2 × 10 -6−10 -5m were obtained using the r.f. sputtering method. Depending on the growth conditions, the films exhibit an axial texture of type 〈001〉 or 〈101〉 and also various degrees of structural perfection. The measure of the structural perfection of the thin films was taken to be the mean dimension D of the crystallites and the mean value 〈Δ d/ d〉 of the lattice strains in the crystallites in the direction normal to the substrate. Values of D and 〈Δ d/ d〉 and the type of texture determine the dielectric and piezoelectric properties of the films, and in particular the degree of diffuseness of the ferroelectric phase transition. It was ascertained that resputtering effects played an important role in the thin film growth process. This was found from investigations of the dependence of structure and growth rate of the thin film on the substrate-to-target distance, on the pressure of the working gas and on the angle of slope of the substrate relative to the stream of plasma particles bombarding the substrate.