Oxygen Vacancy Linear Clustering in a Perovskite Oxide.

Oxygen vacancies have been implicitly assumed isolated ones, and understanding oxide materials possibly containing oxygen vacancies remains elusive within the scheme of the isolated vacancies, although the oxygen vacancies have been playing a decisive role in oxide materials. Here, we report the presence of oxygen vacancy linear clusters and their orientation along a specific crystallographic direction in SrTiO3, a representative of a perovskite oxide. The presence of the linear clusters and associated electron localization was revealed by an electronic structure represented in the increase in the Ti2+ valence state or corresponding Ti 3d2 electronic configuration along with divacancy cluster model analysis and transport measurement. The orientation of the linear clusters along the [001] direction in perovskite SrTiO3 was verified by further X-ray diffuse scattering analysis. Because SrTiO3 is an archetypical perovskite oxide, the vacancy linear clustering with the specific aligned direction and electron localization can be extended to a wide variety of the perovskite oxides.