Misfit accommodation of epitaxial La1−xAXMnO3 (A=Ca, Sr) thin films

Abstract

Thin film of La1−xAxMnO3 (A=Ca, Sr) grown epitaxially on substrates give a unique opportunity to induce different types of perovskite distortions by creating different stress fields resulting from lattice mismatch with the substrate. Thin films of La0.67Ca0.33MnO3 on a SrTiO3(100) substrate, with a misfit of 1.54% (aF<aS), exhibit a remarkable microstructure. In direct contact with the SrTiO3 substrate a thin perfectly coherent La1−xCaxMnO3 layer, which exhibits a slightly distorted monoclinic symmetry, is formed. On top of this first layer a second thicker layer is grown; it has a columnar microstructure. For epitaxial La0.7Sr0.3MnO3(LSMO) films on a LaAlO3(001) substrate the evolution of stress (2.77%, aF>aS) in the film is function of film thickness and thermal treatment. Thin films (20 nm) are accommodated elastically. In thicker films the stress is partially relieved after annealing by the formation of a network of misfit dislocations with an edge character. For epitaxial La0.9Sr0.1MnO3 films on SrTiO3 (100) the small misfit (aF≈aS) is accommodated either purely elastically (for thin film) or by the formation of periodic microtwins.