Structural and electro-optic properties of Ba0.7Sr0.3TiO3 thin films grown on various substrates using pulsed laser deposition

Epitaxial Ba0.7Sr0.3TiO3 (BST) thin films were deposited on various single crystal substrates, including LaAlO3 (LAO) (001), (LaAlO3)(0.3)(Sr2AlTaO6)(0.35) (LSAT) (001), and SrTiO3 (STO) (001), using pulsed laser deposition in order to study their structural and electro-optic properties. All the films exhibit a good crystalline quality and a pure perovskite phase with a distorted lattice structure. The in-plane temperature dependence of relative permittivity of the films was measured on interdigital electrodes. The films grown on LAO and LSAT exhibited an obvious room-temperature ferroelectric state, while the film grown on STO showed a broad phase transition peak near room temperature. Correspondingly, large linear electro-optic effects were observed in the BST films grown on LAO and LSAT in a transverse geometry at a wavelength of 632.8 nm using a modified Senarmont method. The linear electro-optic coefficient r(c)of the BST films grown on LAO and LSAT was found to be 82.7x10(-12) and 125.0x10(-12) m/V, respectively. Nevertheless, a predominantly quadratic and slightly asymmetric electro-optic behavior is observed for the film grown on STO with the quadratic electro-optic coefficient R-c of 12.9x10(-18) m(2)/V-2.