Electronic structure evolutions driven by oxygen vacancy in SrCoO 3− 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 SrCoO 3− 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 SrCoO 2.5+ δ has a typical O 2p characteristic. With further increasing oxygen content, the Co ions transform from a high spin Co 3+ to an intermediate spin Co 4+ , resulting in a transition of SrCoO 3− x from insulator to metal. Our results on the electronic structure evolution with the oxygen vacancies in SrCoO 3− x not only illustrate a spin state transition of Co ions, but also indicate a perspective application in catalysis and energy field.