Impact of Fe doping on the electronic structure of SrTiO3 thin films determined by resonant photoemission

Epitaxial thin films of Fe doped SrTiO3 have been studied by the use of resonant photoemission. This technique allowed to identify contributions of the Fe and Ti originating electronic states to the valence band. Two valence states of iron Fe2+ and Fe3+, detected on the base of XAS spectra, appeared to form quite different contributions to the valence band of SrTiO3. The electronic states within the in-gap region can be attributed to Fe2+, Fe3+ and Ti3+ ions. Fe2+ originating states which can be connected to the presence of oxygen vacancies form a broad band reaching binding energies of about 0.5 eV below the conduction band while Fe3+ states form in the gap a sharp feature localized just above the top of the valence band. It has been shown that Fe doping induced Ti originating states in the energy gap which can be related to hybridization of Ti and Fe 3d orbitals.