Characterization of ferroelectric SrBi2Ta2O9 thin films prepared from alkoxide solutions

SrBi2Ta2O9 thin films prepared by chemical liquid deposition using alkoxide precursor solutions, followed by annealing at various temperatures, were c haracterized with a focus on the correlation between composition, microstru cture, and ferroelectric properties. P-E hysteresis loops of the films exhi bited well-defined shapes at temperatures above 700 degrees C, and the leak age current decreased with increasing annealing temperature, except for a f ilm annealed at 750 degrees C. The crystal growth proceeded and ferroelectr ic properties of the films improved with increasing annealing temperature, whereas a large leakage current was observed for the film annealed at 750 d egrees C. Quantitative X-ray photoelectron spectroscopic analysis and high- resolution transmission electron microscopic observation indicated the pres ence of a substantial amount of metallic bismuth in all films, predominantl y in microcrystallite regions and on film surfaces, including the inner sur face of cavities. The atomic fraction of metallic bismuth increased upon sl ight argon etching; however, the total bismuth content was significantly re duced. The metallic bismuth was amorphous and detected as vibrating spheric al particles measuring approximately 5 nm under electron irradiation. The d iscontinuity in morphology, such as cavities at the interface between large single-crystal grains and microcrystallite regions, was most remarkable in the film annealed at 750 degrees C. The condensation of metallic bismuth a t the cavities is believed to increase the leakage current when the path fo rmed by cavities penetrates through the him. (C) 1999 The Electrochemical S ociety. S0013-4651(98)03-078-X. All rights reserved.