Vacancies are the dominant point defects in perovskite oxides, however, detecting and identifying the nature of vacancy defects in thin films remains challenging. This can be achieved using electron-beam methods but concentrations of several percent are required. Here we use a high-flux positron beam, providing high statistics positron lifetime measurements, to identify vacancies in laser ablated SrTiO3 on SrTiO3. The method is capable of subparts per million sensitivity and when combined with d... »