The capacitance dispersion in La and Mg co-substituted BiFeO3 thin film was studied at different stages of polarization switching. A negative capacitance (NC) behavior was observed in the sample that was fatigued above 109 switching cycles. The origin of the NC was investigated through analyzing relaxation processes and charge transport kinetics by admittance spectroscopy. An activation energy of ∼0.6eV and a zero field mobility μ0 = 5.33x10−13m2/Vs were thus obtained. A physical mechanism was proposed to explain this behavior. It involves a redistribution of oxygen vacancies, which were trapped at the film/electrode interface during the fatigue process.

Negative Capacitance Induced by Redistribution of Oxygen Vacancies in the Fatigued BiFeO3-Based Thin Film. Q.Ke, X.Lou, H.Yang, A.Kumar, K.Zeng, J.Wang: Applied Physics Letters, 2012, 101[2], 022904