Microstructure and electric properties of BCZT thin films with seed layers

Abstract

Lead free Ba_0.99Ca_0.01Ti_0.98Zr_0.02O₃ (BCZT) thin films with seed layers were prepared by using sol–gel processing technique. The seed layers, ranging from 10 nm to 40 nm, were introduced between the BCZT films and the Pt(111)/Ti/SiO₂/Si substrates. The effects of seed layer thickness on the structure and dielectric properties of the thin films were investigated. With the increase of seed layer thickness, the grain size of the BCZT thin films increases from about 100 nm to 300 nm, accordingly, the dielectric constants decrease at lower frequency. The highest dielectric tunability is 34.5% for the films with a 20 nm-thick seed layer. Improved effective piezoelectric coefficients (d₃₃) were observed in the BCZT thin films. The maximum d₃₃ value of BCZT thin films with a 30 nm-thick seed layer is approximately 70 pm V⁻¹, which is comparable to that of polycrystalline PZT thin films. The seed layer thickness dependence of the electric properties is attributed to the dipole polarization. This demonstrated the possibility to control the microstructure and improve properties of BCZT thin films, which could be exploited for functional devices that demand high quality.