Studies of electrical polarization fatigue in SrBi₂Ta₂O₉ thin films

The polarization suppression and electrical properties directly associated with the electrical polarization fatigue in SrBi₂Ta₂O₉ system were systematically investigated using Pt/SBT/Pt capacitors. Three general observations were made after 10⁹ switching cycles: (i) approx. 95% of the remanent polarization was conserved, (ii) both high and zero bias field capacitance decreased, and (iii) leakage current density increased from approximately 10^-7 to 10^-5 A/cm² at approx. 30kV/cm². In addition, the 'knee' field, at which the leakage abruptly increases, assumed smaller values with cumulative switching cycles. Temperature dependent leakage data was collected for both as-deposited and field-cycled samples. Based on these results, we propose the possibilities of enhanced concentration of charge carriers or additional reductions in interfacial conduction barriers. Motion of oxygen vacancies to less-shallow energy levels near electrode/ferroelectric interface may allow this mechanism to occur.