Lattice mismatch accommodation in perovskite films on perovskite substrates

Cubic perovskite films with different compositions were grown on perovskite substrates to investigate the influence of a large lattice mismatch on growth phenomena via the chemical solution deposition method, using toluene solutions of different 2-etyhlhexanoates and neodecanoates. The films were pyrolyzed to crystallize the perovskite of the desired composition and then heated to 1000 degrees C to promote epitaxial grain growth. Pole figures obtained via X-ray diffraction as well as selected area diffraction (SAD) of TEM specimen with lattice mismatches of 2.5% (SrTi0.5Zr0.5O3 on SrTiO3), 5% (SrZrO3 on SrTiO3), 7.4% (BaZrO3 on SrTiO3) and 8.2% (SrZrO3 on LaAlO3) reveal only the epitaxial orientation [100](001) film parallel to [100](001) substrate. The XRD and TEM results also indicate increasing polycrystallinity with increasing lattice mismatch. High resolution electron microscopy (HREM) of films on SrTiO3 demonstrated that an array of misfit dislocations is present al the interface. The misfit dislocations have line vectors 1 of (100) type and Burgers vectors b of [010] type. Dislocation separation distances obtained with HREM and XRD lattice parameter measurements show that the strain energy within the films, owing to lattice mismatch, is nearly fully relaxed. The mechanisms of epitaxial growth and dislocation formation are discussed. (C) 1998 Acta Metallurgica Inc.