Microstructure of dielectric LaLuO₃ films on (001) SrTiO₃ substrates

The microstructure of dielectric LaLuO₃ films grown on SrRuO₃-buffered (001) SrTiO₃ substrates is investigated by means of transmission electron microscopy. A multi-domain structure is observed at the film areas close to the interface between the LaLuO₃ and SrRuO₃ layers in both cross-section and plan-view samples. In these areas, the domains grow with either the <110> or the [001] crystallographic direction parallel to the normal of the film. With increasing film thickness, the [001] domains are found to grow over the other types, resulting in a microstructure of [001]-orientated domains with 90° in-plane rotation in the top part of the film. Lattice defects such as dislocations and lattice strain at the domain boundaries are studied and discussed in the light of the difference between the lattice parameters.