High tunability in compositionally graded epitaxial barium strontium titanate thin films by pulsed-laser deposition

Abstract

Compositionally graded barium strontium titanate [(Ba[sub x]Sr[sub 1-x])TiO₃—BST, x=0.75, 0.8, 0.9, and 1.0] thin films are fabricated by pulsed-laser deposition on a LaAlO₃ substrate with (La[sub 0.7]Sr[sub 0.3])MnO₃ as the bottom electrode. A high dielectric permittivity and temperature characteristic without Curie-Weiss law are obtained. A tunability of over 70% is obtained at frequency of 1 MHz, which is higher than that of single BST layer with the same compositions. All the results indicate that the graded thin films have better electrical properties than a single-layer film.