Correlation between composition, microstructure, and ferroelectric properties of SrBi₂Ta₂O₉ thin films

SrBi₂Ta₂O₉ thin films prepared by a solution-deposition process were formed at various annealing temperatures. P-E hysteresis loops of the fims exhibited well-defined shapes, and the leakage current decreased with increasing annealing temperature except for one annealed at 750°C. The considerable amount of metallic Bi on the film surface diffused from the inner part was evaluated by a quantitative x-ray photoelectron spectroscopic analysis. A discontinuity in morphology such as cavities detected by transmission electron microscopic observation at grain boundaries between large single-crystal grains and microcrystallite regions, which was pronounced in the film annealed at 750°C, is suggested as inducing an increase in leakage current by the condensation of metallic Bi at the cavities.