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 inv estigated. The interfaces were fabricated by metal-organic deposition of Sr ZrO3 layers on (001) SiTiO3 single crystal substrates. Under appropriate co nditions the SrZrO3 layer grows epitaxially, with its crystal lattice paral lel to the lattice of the substrate ("cube-on-cube" orientation relationshi p). In the layer/substrate interface a square network of dislocations accom modates the misfit between corresponding spacings in the two crystals. Thes e 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-reso lution transmission electron microscopy and also by high-resolution scannin g transmission electron microscopy. Quantitative image analysis has shown t hat a (002) layer of TiO2 terminates the SrTiO3 crystal, and the SrZrO3 cry stal commences with a (002) layer of Sr-O. Concerning the {200} layers norm al to the interface it was found that in interface regions of good match, b etween the misfit dislocations, the perovskite structure continues straight through the interface: Sr-O layers of SrTiO3 continue as Sr-O layers of Sr ZrO3; and TiO2 layers continue as ZrO2 layers. Where the misfit dislocation s reside, however, in regions of poor match, a lateral offset exists betwee n the two crystals and disrupts the perovskite structure: on the core plane (the symmetry plane) of the misfit dislocations a (200) TiO2 layer of SrTi O3 continues as a (200) SrO layer in SrZrO3. (C) 1998 Acta Metallurgica Inc . Published by Elsevier Science Ltd. All rights reserved.