Effect of annealing method to crystalize on Sr0.9Bi2.3Ta2O9+α thin film properties formed from alkoxide solution

Sr0.9Bi2.3Ta2O9+alpha (SBT) thin films were formed from a mixed alkoxide solution and were heat-treated by various annealing methods. The SET thin film heat-treated with the standard temperature rising at a rate of 10 degrees C/min (standard thermal annealing: STA) showed higher squareness (effective remanent polarization/effective saturation polarization) and effective remanent polarization values than those of the film heat-treated with a rapid temperature rise at a rate of 125 degrees C/s (rapid thermal annealing: RTA). This difference was large in the region of low applied voltage. The low values of the SET film with RTA treatment were caused by lower crystal continuity in the direction of film thickness than that of the SET film with STA treatment. The SET film with RTA treatment showed a higher leakage current density for the entire applied voltage region than that of the film with STA treatment. The higher leakage current density was caused by fine nonstoichiometric (Bi-rich) particles which exist at grain boundaries of large grains. Therefore, it was concluded that the high squareness ratio and low leakage current density are obtained in SBT film which has only one grain in the film thickness direction and does not have nonstoichiometry fine particles around grain boundaries.