Influence of the vicinal surface on the anisotropic dielectric properties of highly epitaxial Ba_0.7Sr_0.3TiO₃ thin films

Epitaxial thin films of Ba_0.7Sr_0.3TiO₃ (BST) were grown on the designed vicinal single-crystal LaAlO₃ (001) substrates to systematically investigate the evolution of microstructures and in-plane dielectric properties of the as-grown films under the strains induced by surface step terraces. Anisotropic dielectric properties were observed, which can be attributed to different tetragonalities induced by vicinal LaAlO₃ substrates with miscut orientations along the [100] and [110] directions with different miscut angles of 1.0°, 2.75° and 5.0°. A terrace geometric model with both compressive and tensile strained domains in the BST film was established, which is in good agreement with the experimental results. Our experimental studies not only shed new light on the heteroepitaxial growth mechanism, but also provide a promising platform for the design and integration of high performance device applications.