Influence of oxygen partial pressure on the structural and dielectric properties of Ba(Zr0.3Ti0.7)O3 thin films grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) using pulsed laser deposition

Epitaxial Ba(Zr_0.3Ti_0.7)O₃ thin films were grown on (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.35 (001) single-crystal substrates by pulsed laser deposition at 700 °C in different oxygen partial pressures ranging from 6.7 Pa to 40.0 Pa. A strong correlation is observed between the structure and dielectric properties for the Ba(Zr_0.3Ti_0.7)O₃ thin films. The tetragonal distortion (ratio of in-plane and out-of-plane lattice parameter, a/c) of the films depends on the oxygen partial pressures. a/c varies from 0.989 at 6.7 Pa to 1.010 at 40.0 Pa, indicating the in-plain strain changes from compressive to tensile. The in-plain strain (either compressive or tensile) shifts the Curie temperature of the Ba(Zr_0.3Ti_0.7)O₃ thin films dramatically. Surface morphology and dielectric properties of Ba(Zr_0.3Ti_0.7)O₃ thin films have a strong dependence of the oxygen partial pressure. The film grown 26.7 Pa, which corresponds to a moderate in-plain tensile strain and a Curie temperature of ~ 30 °C, shows the largest relative permittivity, tunability and the best figure of merit in a broad frequency range (1 kHz-500 MHz), which may be a promising candidate for room-temperature microwave device applications.