Complex oxide materials, especially the ABO₃-type perovskite materials, have been attracting growing scientific interest due to their unique electro-optical properties, leading to photorefractive effects that form the basis for such devices as holographic storage, optical data processing and phase conjugation. The optical and mechanical properties of non-metals are strongly affected by the defects and impurities that are unavoidable in any real material. Nanoscopically sized surface effects play an important role, especially in multi-layered ABO₃ structures, which are...