Thermal stability of artificial SrTiO3/SrO superlattice epitaxially grown on SrTiO3 single crystal

A post-annealed artificial (SrTiO3)(5)/SrO superlattice frown on a (100) Sr TiO3 single crystal substrate was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), to investigate the thermal stab ility of inserted rock-salt layers of SrO, the so-called Ruddlesden-Popper (RP) layers, in the epitaxial thin film. The intensities of XRD satellite p eaks stemming il um the superstructure decreased with increasing annealing temperature and almost disappeared at 1000 degrees C. The high-resolution c ross-sectional TEM image of the superlattice after annealing at 1000 degree s C showed that RP layers perpendicular to the film surface appeared, which was predominant over in-plane RP layers. The predominant formation of the vertical RP layers may be attributed to the strain release of RP layers at the film surface.