RELATIONSHIPS AMONG FERROELECTRIC FATIGUE, ELECTRONIC CHARGE TRAPPING, DEFECT-DIPOLES, AND OXYGEN VACANCIES IN PEROVSKITE OXIDES

Using electron paramagnetic resonance, it is shown that the reduction of the switchable polarization in BaTiO3 crystals by repeated polariza tion reversals (fatigue) is accompanied by the trapping of electronic charge at isolated acceptor impurities and atomic scale distortions in the perovskite oxygen octahedron. The distortions are proposed to ent ail nearby oxygen vacancies. Our results suggest that the suppressed p olarization state arises by trapping electronic charge carriers at dom ain walls; the trapped electronic charge can become thermally stabiliz ed by fatigue-induced distortions in the oxygen octahedron. The octahe dron distortions are shown to be unique to fatigue-induced degradation ; they are not observed in BaTiO3 capacitors that have an optically-in duced suppressed polarization state.