Correlation between magnetoresistive properties and growth morphology of La1-xMnO3-delta thin films deposited on SrTiO3, LaAlO3 and MgO
Résumé
A new metal-organic chemical vapour deposition (MOCVD) technique was used for fabrication of epitaxial La-manganite thin films La1-xMnO3-delta with both lanthanum and oxygen deficiencies. Three kinds of substrates, i.e. SrTiO3 (001), LaAlO3 (012) and MgO (001), were chosen for comparison. Electrical and magnetic property measurements revealed that the amplitude of the colossal magnetoresistance (CMR) is dependent on the nature of the substrate whereas the electrical and magnetic transition temperatures are not sensitive to the substrate type. In order to correlate the physical properties of the films to their crystallization quality and their growth morphology, scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as high-resolution transmission elect:ron microscopy (HRTEM), were employed. Cross-sectional TEM investigations showed that the La1-xMnO3-delta is generally in good epitaxy with all three kinds of substrate. The orientation relationships between the film and substrate are rather well defined at the vicinity of the interface but not at the surface of the film. Deposition of La1-xMnO3-delta on SrTiO3 produces the best interfacial match since these two have the least lattice misfit. This is consistent with the best magnetoresistive property measured for the investigated systems. (C) 2001 Elsevier Science B.V. All rights reserved.