Electrical properties and extension mechanism of Ohmic region of sol–gel derived Ba_0.7Sr_0.3TiO₃ thin films by Zn doping

Undoped and 3 mol% Zn-doped barium strontium titanate thin films were deposited on Pt/Ti/SiO₂/Si substrates using a sol–gel method. The microstructure and morphology of the films were characterized by X-ray diffraction and atomic force microscopy. It showed that both films are polycrystalline with a perovskite structure and smaller grains were observed for the Zn-doped thin films. Dielectric measurements showed that the dielectric loss at 500 kHz was reduced from 0.042 to 0.019 by Zn doping, which was accompanied by a slight decrease of the dielectric constant from 303 to 273. At an applied electric field of 60 kV/cm, the leakage current density of the Zn-doped Ba_0.7Sr_0.3TiO₃ thin films was 2.5 × 10⁻⁸ A/cm², which was by two orders of magnitude lower than that of the undoped films. The leakage current characteristics also indicated that the Ohmic conduction region of barium strontium titanate thin films was extended by Zn dopant. The microstructure, electrical properties and extension mechanism of Ohmic conduction region of the Zn-doped barium strontium titanate thin films were discussed in relation to the effect of Zn doping.