Conservative antiphase boundary in SrTiO₃ films on LaAlO₃ substrates with SrRuO₃ buffer layers

We have studied the microstructure of SrTiO₃ films on LaAlO₃ substrates with the SrRuO₃ buffer layer using high-resolution transmission electron microscopy. While high density of defects due to lattice mismatch were found at the SrRuO₃/LaAlO₃ interface, no misfit dislocation was observed at the SrTiO₃/SrRuO₃ interface. The {111} stacking fault in the SrRuO₃ buffer layer propagates into the SrTiO₃ film, giving rise to a type of antiphase boundary on the {110} plane with a crystallographic shear vector of a/2{001}!!!!. The boundary is a conservative one which does not lead to any charge defects. A model based on dislocation interactions is proposed to explain the generation mechanism of the antiphase boundary.