Orbital Reconstruction in a Self-assembled Oxygen Vacancy Nanostructure

TL;DR

This study reveals how spatially confined oxygen vacancies in BiFeO3 influence its electronic structure and conductivity, using advanced X-ray techniques to understand orbital reconstruction without redox reactions.

Contribution

It demonstrates the microscopic role of oxygen vacancy confinement and its control via Ca doping in BiFeO3, revealing orbital band reconstruction and electronic localization.

Findings

Increased Ca doping reconstructs Fe 3d orbitals without redox changes.

Vacancy confinement reduces electron hopping, localizing the valence band.

Doping decreases the material's conductivity due to orbital localization.

Abstract

We demonstrate the microscopic role of oxygen vacancies spatially confined within nanometer inter-spacing (about 1 nm) in BiFeO3, 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 Ca2+ for Bi3+ cation. We found that by increasing the substitution, the in-plane orbital bands of Fe3+ 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 3d-electronic structure, around the Fermi level. This band localization causes to decrease the conductivity of the doped BiFeO3 system.