Improved characteristics of Bi4Ti3O12 thin film on ITO glass by using excess Bi2O3-added Bi4Ti3O12 ceramic as source target

Bi4Ti3O12 thin films are deposited on ITO/glass substrates by RF magnetron sputtering at room temperature using ceramic targets of Bi4Ti3O12+4 wt% Bi2O3 and Bi4Ti3O12, respectively. Thin films of thickness 600–700 nm are deposited and then annealed using rapid thermal annealing (RTA) technique conducted in an oxygen atmosphere at temperatures ranging from 625 to 725 °C with a heating rate of 900 °C/min. XRD analysis reveals that the crystallization temperature of the films deposited using the Bi4Ti3O12+4 wt% Bi2O3 target is 25 °C lower than that of films deposited using Bi4Ti3O12 target. Moreover, the crystallinity of the former films is superior to that of the latter under the same fabrication conditions. The EDS results indicate that the Bi/Ti atomic ratio decreases with an increasing annealing temperature, which suggests that evaporation loss of the bismuth occurs during the heating process. The relative dielectric constant and the polarization charge density of the films deposited using the Bi4Ti3O12+4 wt% Bi2O3 target are found to be 295 and 12 μC/cm2, respectively, which are approximately 70% and 25% higher than the respective values of the films deposited using the stoichiometric Bi4Ti3O12 target. Although the leakage current density of the former films is somewhat higher than that of the latter, it is more stable and remains constant at approximately 1×10−5 A/cm2 under 360 kV/cm without breakdown.