Oxygen vacancy induced photoluminescence and ferromagnetism in SrTiO ₃ thin films by molecular beam epitaxy

SrTiO₃ thin films were epitaxially grown on (100) SrTiO ₃ substrates using molecular beam epitaxy. The temperature for growth of the films was optimized, which was indicated by x-ray diffraction and further confirmed by microstructural characterization. Photoluminescence spectra show that oxygen-vacancy contributes to red and blue luminescence of oxygen-deficient post-annealed films, and a red shift was observed in blue region. On the other hand, ferromagnetism in film form SrTiO₃ was observed from 5 K to 400 K and could be further enhanced with decreasing oxygen plasma partial pressure in annealing processes, which might be explained by the theory involving d⁰ magnetism related to oxygen-vacancy. From the cooperative investigations of optical and magnetic properties, we conclude that intrinsic defects, especially oxygen-vacancy, can induce and enhance luminescence and magnetism in SrTiO₃ films.