Effects of CeO₂ buffer layer on the dielectric properties of Ba_0.6Sr_0.4TiO₃ thin films prepared by sol–gel processing

Abstract

The Ba_0.6Sr_0.4TiO₃ (BST60) thin films were deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by a sol–gel method. The thickness of CeO₂, serving as a buffer layer, was varied from 0 to 75 nm, in order to optimize the dielectric tunable property. X-ray patterns analysis indicates that all the thin films exhibit good crystalline quality with a pure perovskite phase and insertion of the CeO₂ buffer layer does not change the crystal structure of BST60. Dielectric properties of the thin films were investigated as a function of both temperature and direct current electric field. The results show that dielectric constant and loss are modified by insertion of the CeO₂ buffer layer. The BST60 thin films with 25 nm thickness CeO₂ buffer layer have the highest figure of merit, low dielectric loss, and suitable dielectric constant, which render them attractive for the tunable microwave device applications.