Microstructure and electrical transport mechanisms of the Ca-doped LaMnO3 films grown on MgO substrate

Abstract

La0.7Ca0.3MnO3 (LCMO) thin films have been grown on MgO substrate using the metal organic deposition process. The lattice mismatch between LCMO and MgO is relatively large around 8.14% imposing large in-plane-tensile strain and out-of-plane-compressive strain on the film. Hence the structural, microstructural and electrical properties have been found to be strongly correlated to the strain degree and relaxation. Cross-section transmission electron microscopy observations demonstrate the presence of microstructural defects due to the large lattice mismatch between the LCMO and MgO. In addition to structural and microstructural defects, X-ray diffraction and Raman spectroscopy measurements show the existence of a minor phase of MnO in the film. Magnetization versus temperature measurement show a relatively low Curie temperature around 75 K. The electrical behavior is found to be semiconducting over a large temperature interval. The electrical transport mechanisms have been investigated using the small polaron hopping and variable range hopping models and correlated to their microstructural properties. Keywords: Manganite, Thin film, Epitaxy, Electric transport mechanism