It was found, using a local density approximation method, that O vacancies tended to cluster in a linear way in SrTiO3; accompanied by strong electron localization at the 3d state of the nearby Ti transition-metal ion. The vacancy clustering and the associated electron localization had a marked impact upon materials properties with regard to a reduction in free-carrier densities, the appearance of characteristic optical spectra and a decrease in vacancy mobility. The high stability against the vacancy migration also suggested the physical reality of the vacancy cluster.

Oxygen Vacancy Clustering and Electron Localization in Oxygen-Deficient SrTiO3: LDA+U Study. D.D.Cuong, B.Lee, K.M.Choi, H.S.Ahn, S.Han, J.Lee: Physical Review Letters, 2007, 98[11], 115503 (3pp)