The microstructures of strained epitaxial La0.7Sr0.3MnO3 films on an AlLaO3(001) substrate were investigated by means of electron diffraction and high-resolution electron microscopy in cross-sectional and plan views. Fourier transforms of the high-resolution images permitted the deduction of the local lattice parameters at increasing distances from the interface. The evolution of stress in the film was studied as a function of the film thickness and heat treatment. It was found that, close to the interface, both the film and the substrate were elastically strained in opposite senses; such that the interface was perfectly coherent for films which did not exceed a thickness of 30 to 35nm. In thicker films, inhomogeneities developed in the as-grown films. In films of about 120nm, the stress was partially relieved after annealing by the formation of misfit dislocations with an edge character. In the case of annealed thick films, some evidence was found for the formation of coherent precipitates which contributed to stress relief. It was suggested that part of the mismatch strain was accommodated by the isomorphous substitution of ions having a different size and/or different charge.

High-Resolution Electron Microscopy Study of Strained Epitaxial La0.7Sr0.3MnO3 Thin Films. O.I.Lebedev, C.Van Tendeloo, S.Amelinckx, H.L.Ju, K.M.Krishnan: Philosophical Magazine A, 2000, 80[3], 673-91