Thermally induced structural changes in epitaxial SrZrO3 films on SrTiO3

Epitaxial, continuous, approximately 40-nm-thick films of SrZrO3, on SrTiO3, substrates prepared by a chemical solution deposition method including a postdeposition heat treatment at 900-1000 degrees C were subjected to further heat treatments at higher temperatures (approximately 1200-1300 degrees C) to investigate their high temperature stability. Experimental investigations included scanning electron microscopy, atomic force microscopy, and conventional transmission electron microscopy. The investigations have demonstrated a morphological instability of the films. Concentration profiles of the cations determined by energy dispersive x-ray spectroscopy, as well as investigations by x-ray diffraction, revealed that the film islands consisted of a solid solution. As shown by high-resolution electron microscopy, the reaction between film and substrate also led to an increase in the separation distance of the misfit dislocations that were introduced during the lower temperature heat treatment to relax the lattice mismatch strain. The morphological and structural changes of the films are reported and discussed in this paper.