Origin of the Enhanced Polarization in La and Mg Co-substituted BiFeO3 Thin Film during the Fatigue Process

TL;DR

This study investigates the unusual polarization peak during fatigue in La and Mg co-substituted BiFeO3 thin films, attributing it to defect dynamics, especially oxygen vacancies and electron injection, affecting the film's electrical properties.

Contribution

It provides a new understanding of polarization fatigue in BiFeO3 thin films by linking defect evolution, particularly oxygen vacancies, to anomalous polarization behavior.

Findings

Oxygen vacancy motion has a low energy barrier during fatigue.

Electron injection occurs concurrently with oxygen vacancy migration.

A model explains the polarization peak via Schottky barrier modification.

Abstract

We have studied the polarization fatigue of La and Mg co-substituted BiFeO3 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 (VO..) 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 VO.. at the metal-dielectric interface.