Atomistic structure of misfit dislocations in SrZrO 3/SrTiO 3 interfaces

Abstract

The atomistic structure of misfit dislocations at heterointerfaces between two ionic crystals with the perovskite structure, SrZrO 3 and SrTiO 3, is investigated. The interfaces were fabricated by metal–organic deposition of SrZrO 3 layers on (001) SrTiO 3 single crystal substrates. Under appropriate conditions the SrZrO 3 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 SrZrO 3/SrTiO 3 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 TiO 2 terminates the SrTiO 3 crystal, and the SrZrO 3 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 SrTiO 3 continue as Sr–O layers of SrZrO 3, and TiO 2 layers continue as ZrO 2 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) TiO 2 layer of SrTiO 3 continues as a (200) SrO layer in SrZrO 3.