Electronic structure evolutions driven by oxygen vacancy in SrCoO3−x films

Ionic defects, such as oxygen vacancies, play a crucial role in the magnetic and electronic states of transition metal oxides. Control of oxygen vacancy is beneficial to the technological applications, such as catalysis and energy conversion. Here, we investigate the electronic structure of SrCoO3−x as a function of oxygen content (x). We found that the hybridization extent between Co 3d and O 2p increased with the reduction of oxygen vacancies. The valence band maximum of SrCoO2.5+δ has a typical O 2p characteristic. With further increasing oxygen content, the Co ions transform from a high spin Co3+ to an intermediate spin Co4+, resulting in a transition of SrCoO3−x from insulator to metal. Our results on the electronic structure evolution with the oxygen vacancies in SrCoO3−x not only illustrate a spin state transition of Co ions, but also indicate a perspective application in catalysis and energy field.