THE INFLUENCE OF GRADIENT STRESS ON THE DIELECTRIC PROPERTIES OF PEROVSKITE FERROELECTRIC FILMS

Abstract

ABSTRACT In the application of a set of position-thickness-dependent stress to modified Landau-Devonshire theory, the distribution of dielectric constant and the dependence of effective dielectric constant on the film thickness and the temperature have been studied in BaTiO3 films with fine grains. The results show that both the transition temperature and dielectric constant are dependent with positions. When T < T cfmax , for both a-phase and c-phase, a layer with small dielectric constant exists near the interface between the film and the substrate, which is the dead-layer in “series capacitor model.” For c-phase, when T cfmax > T > T c , a layer with giant dielectric constant appears in the film. And when T > T cfmax , the dielectric constant near the interface is higher than that near the center. The “series capacitor model” is invalid at high temperature for c-phase. The theoretical results agree with the experiment.