A novel structural expansion in SrTiO3 tuned by electric field and visible-light

SrTiO3 is a model perovskite oxide of abundant physical properties, which are closely associated with internal oxygen vacancy (VO) defects. Through in situ X-ray diffraction measurements, we observed a remarkable structural expansion in the near-surface region of (001)-SrTiO3 induced by an external electric field. By repeated scanning and consistently monitoring the 002 reflections, forming process of the unique structural distortion was obtained and considered to be the results of electromigration and redistribution of VOs. Peculiarly, it was found that a much greater lattice distortion would occur rapidly in SrTiO3 under the illumination of visible light, and be effectively tuned depending on wavelength. We propose that the light effect stems from photo-excitation, which generates extra carriers and remarkably speeds up the diffusion of VOs. This work provides a feasible way towards tuning the kinetics of VOs and structure of SrTiO3 by combined stimuli of electric field and light illumination, yielding novel properties in above films as well as hetero-interface at SrTiO3-based oxide system.