Electronic and local structures of BiFeO3 films

The electronic structure of BiFeO3 (BFO), BiFeO3-PbTiO3 solid solution (BFO-PT), and Mn-doped BFO-PT (BFM-PT) films fabricated by chemical solution deposition was investigated by x-ray absorption fine structure (XAFS). The BiFeO3 shows a large leakage current owing to the mixed valance state of Fe2+ and Fe3+. The BFO film has a blunt absorption edge jump indicating the charge fluctuated state of the iron ions. The BFO-PT and BFM-PT films have sharp absorption edges, and the absorption energy of these films shifted to opposite energy. The valence fluctuation of the iron ions was closely connected with the leakage current properties. The charge fluctuated BFO film showed a leaky feature, and the charge unfluctuated BFO-PT and BFM-PT films had improved leakage current properties. The valence fluctuation of the iron ions can be controlled by Mn substitution and by making solid solutions.