Dielectric Property of c-axis Oriented Epitaxial BLSF Films

Abstract

Thin films of c-axis-oriented Bi-layer-structure ferroelectrics (BLSF) of SrBi₄Ti₄O₁₅ and CaBi₄Ti₄O₁₅ with film thickness ranging from 20-170 nm were epitaxially grown on (100)SrRuO₃//(100)SrTiO₃ substrates by metalorganic chemical vapor deposition (MOCVD). The relative dielectric constants of both films kept constant at approximately 200 for the film thickness down to 20 nm. The dependence of capacitances on the applied electric field was negligible, and the leakage current densities on the order of 10^-8 A/cm² at 150 kV/cm were almost unchanged against the film thickness. Surface flatness of these films were also the same irrespective of the film thickness. These characteristics are very attractive for high-capacitance condenser application. Therefore, c-axis-oriented BLSF thin films, whose capacitances are independent of the applied electric field and film thickness, are novel candidates for high-capacitance condenser application.