Defect-mediated ferroelectric domain depinning of polycrystalline BiFeO₃ multiferroic thin films

The ferroelectric domain depinning in a polycrystalline BiFeO₃ film is studied by a defect-mediated diffusion mechanism driven by a secondary re-oxidation anneal. The presence of defect complexes (oxygen-vacancy-associated dipoles) responsible for pinning is discussed from the current-voltage (I-V) characteristics of the film. Dissociation of these complexes by re-oxidation anneal produces the effective depinning of domains in the material. The released oxygen vacancies would be compensated at the re-oxidized state due to the valence change of Fe²⁺ to Fe³⁺. Improvement on domain mobility results in a larger contribution to ferroelectric switching, showing a room-temperature remanent polarization of 67 μC cm⁻².