Atomistic structure of misfit dislocations in SrZrO3/SrTiO3 interfaces

The atomistic structure of misfit dislocations at heterointerfaces between two ionic crystals with the perovskite structure, SrZrO3 and SrTiO3, is investigated. The interfaces were fabricated by metal-organic deposition of SrZrO3 layers on (001) SrTiO3 single crystal substrates. Under appropriate conditions the SrZrO3 layer grows epitaxially, with its crystal lattice parallel to the lattice of the substrate (cube-on-cube orientation relationship). In the layer/substrate interface a square network of dislocations accommodates the misfit between corresponding spacings in the two crystals. These misfit dislocations have edge character, <010> line directions, and <100> Burgers vectors parallel to the interface. The SrZrO3/SrTiO3 interface has been imaged with the misfit dislocations in end-on projection by high-resolution transmission electron microscopy and also by high-resolution scanning transmission electron microscopy. Quantitative image analysis has shown that a (002) layer of TiO2 terminates the SrTiO3 crystal, and the SrZrO3 crystal commences with a (002) layer of Sr-O. Concerning the {200} layers normal to the interface it was found that in interface regions of good match, between the misfit dislocations, the perovskite structure continues straight through the interface: Sr-O layers of SrTiO3 continue as Sr-O layers of SrZrO3, and TiO2 layers continue as ZrO2 layers. Where the misfit dislocations reside, however, in regions of poor match, a lateral offset exists between the two crystals and disrupts the perovskite structure on the core plane (the symmetry plane) of the misfit dislocations a (200) TiO2 layer of SrTiO3 continues as a (200) SrO layer in SrZrO3