Aging behavior and recovery of polarization in Sr_0.8Bi_2.4Ta₂O₉ thin films

Ferroelectric thin films of bismuth-containing layered perovskite Sr_0.8Bi_2.4Ta₂O₉ (SBT) have been prepared by both metalorganic decomposition (designated as MOD-SET film) and magnetron sputtering (designated as sputtering-SBT film) processes. SBT thin films are well known to exhibit free-fatigue behavior with electrical field cycling. However, it was found that after the SBT films were applied with electrical field display, the polarization reduction with time was observed. The aging rate was related to microstructure, which in turn was dependent on the film processing. The sputtering-SBT films show a slower degradation rate than MOD-SBT films. The suppressed polarization can be near-completely recovered by applying either thermal treatment above 150°C or electric-field cycling. There exists a minimum required thermal energy to restore the polarization. The easy recovery exhibited by SBT films in suppressed polarization reveals that a relatively weak domain pinning may exist between domain wall and electronic defects in SBT. The SBT shows little fatigue behavior during electric field cycling but exhibits an aging phenomenon after applied electric field.