Increase in switching charge of ferroelectric SrBi2Ta2O9 thin films with polarization reversal

The increase in switching charge of as-grown SrBi2Ta2O9 (SBT) capacitors wi th polarization reversal was investigated. We call this phenomenon wake-up. The switching charge was increased and the rectangularity of the D-E hyste resis loops was improved with polarization reversal. The switching pulse wi th larger amplitude, longer width and shorter period generated a larger inc rease in the switching charge with polarization reversal. At the same time, the capacitors came to exhibit a rapid increase in leakage current at a ce rtain applied field after the switching. Furthermore, the D-E hysteresis lo op of the capacitors with wake-up shifted toward the positive- or negative- bias field according to the sweeping direction of the applied voltage. We h ave concluded that some spontaneous polarizations locked by localized space charges at the interface layer in the wake-up-exhibiting SET capacitors we re freed by the application of numerous switching pulses, and trap levels g enerated in the interface layer by the switching rendered the rapid increas e in leakage current and the voltage shift of D-E hysteresis easy.