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Issue 19, 2013
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Thickness evolution of the twin structure and shear strain in LSMO films

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X-ray diffraction analysis and orientation contrast scanning electron microscopy imaging of La0.7Sr0.3MnO3 epitaxial layers grown on (001)-SrTiO3 substrates have been used to track the shear strain and twin domain period as a function of the thickness of the films, t. To this end, the diffraction by a periodically modulated twinned structure is analyzed in detail. In contrast with current equilibrium models, here we demonstrate the occurrence of a critical thickness, tτ ∼ 2.0–2.5 nm, for twin formation in rhombohedral perovskite films. The absence of twinning below tτ is explained by the formation of a monoclinic interfacial phase presumably driven by electronic interactions between film and substrate not taken into account in theoretical models. Above tτ, twin domains develop concomitantly with the build-up of misfit shear strains associated with the formation of the rhombohedral structure. At a thickness ∼10 nm, the in-plane and out-of-plane shear strain components exhibit similar values, as imposed by the rhombohedral symmetry. However, upon increasing the film thickness, both strain components are found to follow divergent trajectories indicating a progressive perturbation of the octahedral framework which allows the in-plane lattice parameters to remain fully strained within the explored thickness range (up to 475 nm). Despite these structural perturbations, the twin size follows a t1/2 dependence as predicted for homogeneous films by equilibrium models.

Graphical abstract: Thickness evolution of the twin structure and shear strain in LSMO films

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Article information

15 Jan 2013
08 Mar 2013
First published
08 Mar 2013

CrystEngComm, 2013,15, 3908-3918
Article type

Thickness evolution of the twin structure and shear strain in LSMO films

J. Santiso, L. Balcells, Z. Konstantinovic, J. Roqueta, P. Ferrer, A. Pomar, B. Martínez and F. Sandiumenge, CrystEngComm, 2013, 15, 3908
DOI: 10.1039/C3CE40085A

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