Structural and electro-optic properties of Ba[sub 0.7]Sr[sub 0.3]TiO₃ thin films grown on various substrates using pulsed laser deposition

Abstract

Epitaxial Ba[sub 0.7]Sr[sub 0.3]TiO₃ (BST) thin films were deposited on various single crystal substrates, including LaAlO₃(LAO) (001), (LaAlO₃)[sub 0.3](Sr₂AlTaO[sub 6])[sub 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 Sénarmont method. The linear electro-optic coefficient r[sub c]of the BST films grown on LAO and LSAT was found to be 82.7 x 10ˉ¹² and 125.0 x 10ˉ¹² 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[sub c] of 12.9 x 10[sup -18] m²/V².