Low-temperature growth of epitaxial Ba0.5Sr0.5TiO3 films applicable to microwave tunable devices

Ba0.5Sr0.5TiO3 (BST-0.5) thin films with thickness of 300 nm have been deposited on MgO(001) single-crystalline substrates by on-axis rf-magnetron sputtering at 650 .deg. C. X-ray diffraction data indicate that the BST-0.5 thin films are epitaxially grown on MgO(001) substrates. The orientation relationships are determined to be BST-0.5(001)//MgO(001) and BST-0.5[100]//MgO[100]. The typical dielectric tunability and dielectric loss measured at room temperature and 1 MHz are 33 % and 0.0057, respectively. In order to understand the origin of the relatively low tunability, we have investigated the chemical and structural properties of our BST-0.5 films by using Rutherford back-scattering and high-resolution X-ray diffraction, respectively.