Vacancies were the dominant point defects in perovskite oxides, however, detecting and identifying the nature of vacancy defects in thin films remained challenging. This could be achieved using electron-beam methods but concentrations of several percent were required. Here a high-flux positron beam, providing high statistics positron lifetime measurements, was used to identify vacancies in laser-ablated SrTiO3 on SrTiO3. The method was capable of subparts per million sensitivity and when combined with density-functional theory provided local structure information. The positron lifetime spectrum depth profile detects the presence of large vacancy clusters in a surface layer, a uniform distribution of Sr vacancies through the bulk of the film and resolves the interface with the substrate.

Identification of Vacancy Defects in a Thin Film Perovskite Oxide. D.J.Keeble, R.A.Mackie, W.Egger, B.Löwe, P.Pikart, C.Hugenschmidt, T.J.Jackson: Physical Review B, 2010, 81[6], 064102