Thickness dependence of in-plane dielectric and ferroelectric properties of Ba[sub 0.7]Sr[sub 0.3]TiO₃ thin films epitaxially grown on LaAlO₃

Abstract

The authors have studied the effects of film thickness on the lattice strain and in-plane dielectric and ferroelectric properties of Ba[sub 0.7]Sr[sub 0.3]TiO₃ thin films epitaxially grown on LaAlO₃ (001) single crystal substrates. With increasing film thickness from 20 to 300 nm, the in-plane lattice parameter (a) increased from 0.395 to 0.402 nm while the out-of-plane lattice parameter (c) remained almost unchanged, which led to an increased a/c ratio (tetragonality) changing from 0.998 to 1.012 and consequently resulted in a shift of Curie temperature from 306 to 360 K associated with an increase of the in-plane remnant polarization and dielectric constant of the film.