Oxygen-vacancy-related dielectric relaxation in BiFeO₃ films grown by pulsed laser deposition

Two kinds of BiFeO₃ (BFO) thin films with different oxygen stoichiometry are fabricated on (La, Sr)CoO₃ coated silicon substrates. A Debye-like dielectric relaxation was observed in the samples thermally treated at 3 Pa oxygen. The frequency dependence of permittivity of the samples treated at 3 Pa oxygen can be fitted by a model containing the Debye-like dielectric response and the universal dielectric response. According to the model, the dielectric relaxation can be ascribed to the oxygen vacancy, and the possible influences from the interfacial polarization between BFO and electrodes have been excluded by the measurement of the dielectric responses of BFO films at different dc biased voltages. The calculated value of dc electric conductivity in BFO films from this model has the same order of magnitude as the published results. These results indicate that the existence of oxygen vacancy not only influences the leakage performance of BFO films but also affects the dielectric properties of BFO. The electrical performance of BFO films and devices can be improved by decreasing the density of oxygen vacancy.