Microstructure and misfit relaxation in SrTiO3/SrRuO3 bilayer films on LaAlO3(100) substrates

We studied the microstructure of SrTiO3/SrRuO3 bilayer films on (001) LaAlO3 substrates by high-resolution transmission electron microscopy. At the SrRuO3/LaAlO3 interface a defect configuration of stacking faults and nanotwins bounding either Frank partial dislocations or Shockley partial dislocations and complex interaction between these planar defects were found to be the dominant means of misfit accommodation. The misfit in the SrTiO3/SrRuO3 system, however, is mainly accommodated by elastic strain. Most of the observed defects in the SrTiO3 layer can be related to the [111] planar defects in the SrRuO3 layer propagating and reaching the SrTiO3/SrRuO3 interface. Furthermore, a [110] planar defect can also be introduced in the SrTiO3 layer due to the structure change of the SrTiO3/SrRuO3 interface.