The effect of Bi_(1.5)Zn_(0.5)Nb_(0.5)Ti_(1.5)O_7 cover layer on the dielectric and tunable properties of Ba_(0.6)Sr_(0.4)TiO_3/Bi_(1.5)Zn_(0.5)Nb_(0.5)Ti_(1.5)O_7 bilayered thin films

摘要

Bi_(1.5)Zn_(0.5)Nb_(0.5)Ti_(1.5)O_7 (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba_(0.6)Sr_(0.4)TiO_3 (BST) thin films on the Pt/Ti/SiO_2/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces.