Oxygen vacancy induced photoluminescence and ferromagnetism in SrTiO3 thin films by molecular beam epitaxy

SrTiO3 thin films were epitaxially grown on (100) SrTiO3 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.