Electrode effects on the low-frequency dielectric properties of (Ba, Sr)TiO3 thin films prepared by pulsed laser ablation

(Ba, Sr)TiO3(BST) thin films were prepared by pulsed laser deposition on th e perovskite conductive oxide LaNiO3 (LNO), YBa2Cu3O7-delta(YBCO) films, an d Pt as a bottom electrode. The crystalline structures and surface microstr ucture of the BST deposited on several substrates were characterized by x-r ay diffraction measurement and scanning electron microscopy, respectively. The electrode effects on low-frequency dielectric behavior of BST thin film s were investigated. The complex dielectric constants of the films were mea sured as a function of frequency in the frequency range from 0.1 Hz to 10 M Hz. BST films grown on metallic oxide substrates exhibited marked dielectri c relaxation below 10 MHz. This low frequency dielectric relaxations is att ributed to the ionized space charge carriers such as the oxygen vacancies a nd cation defects in BST film, and the interfacial polarization in the grai n boundary region and the electrode/film interface.