Orbital Reconstruction in a Self-assembled Oxygen Vacancy Nanostructure

We demonstrate the microscopic role of oxygen vacancies spatially confined within nanometer inter-spacing (about 1 nm) in BiFeO 3 , using resonant soft X-ray scattering techniques and soft X-ray spectroscopy measurements. Such vacancy confinements and total number of vacancy are controlled by substitution of Ca 2+ for Bi 3+ cation. We found that by increasing the substitution, the in-plane orbital bands of Fe 3+ cations are reconstructed without any redox reaction. It leads to a reduction of the hopping between Fe atoms, forming a localized valence band, in particular Fe 3 d -electronic structure, around the Fermi level. This band localization causes to decrease the conductivity of the doped BiFeO 3 system.