Origin of the enhanced polarization in la and Mg co-substituted BiFeO ₃ thin film during the fatigue process

We have studied the polarization fatigue of La and Mg co-substituted BiFeO ₃ thin film, where a polarization peak is observed during the fatigue process. The origin of such anomalous behavior is analyzed on the basis of the defect evolution using temperature-dependent impedance spectroscopy. It shows that the motion of oxygen vacancies (V _O ^••) is associated with a lower energy barrier, accompanied by the injection of electrons into the film during the fatigue process. A qualitative model is proposed to explain the fatigue behavior, which involves the modification of the Schottky barrier upon the accumulation of V _O ^•• at the metal-dielectric interface.