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

Compositionally graded barium strontium titanate [(BaxSr1−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 (La0.7Sr0.3)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.