Physical and electrical characterization of sol-gel derived BaxSr1-xTiO3 thin films of various composition ratios and thicknesses

Abstract

Among the various dielectric materials, barium strontium titanate has been extensively studied due to its high dielectric constant, low dielectric loss and high tunability. Barium strontium titanate is a composition dependent to Curie temperature, which decreases linearly with the increasing of Sr amount in the composition. In this study, barium strontium titanate thin films with four different compositions; Ba0.5Sr0.5TiO3, Ba0.6Sr0.4TiO3, Ba0.7Sr0.3TiO3 and Ba0.8Sr0.2TiO3 and four different thicknesses were prepared by using sol-gel technique and deposited on Pt/SiO2/Si substrates. The wellcrystallized,dense, smooth and crack-free thin films are obtained through annealing process at temperature of 800 C. The dielectric constant, tunability and dielectric loss shows strong relationship with the films microstructure. The dielectric constant, tunability and dielectric loss increases as the grain size and film thickness increases. The variations of dielectric constant as a function of voltage for Ba0.5Sr0.5TiO3 and Ba0.6Sr0.4TiO3 thin films are devoid of any spontaneous polarization, which indicates that the thin film is paraelectric in room temperature. However, Ba0.7Sr0.3TiO3 and Ba0.8Sr0.2TiO3 thin films with butterflyshaped curves show the existence of ferroelectric nature. The highest dielectric constant and tunability, 485.02 and 34.75 % were observed in Ba0.7Sr0.3TiO3 composition at thickness of 447.6 nm due to the Curie temperature of Ba0.7Sr0.3TiO3 is close to room temperature. This work demonstrates successful physical and electrical characterization of multiple layers of BaxSr1-xTiO3 thin films to its different composition ratios of Ba and Sr.