Structural study of lanthanum nickelate thin films deposited on different single crystal substrates

Fabrications of La2NiO4+delta thin film layers by liquid-injection metalorganic chemical vapor deposition were tried on different single crystals substrates: (001)Si, (001)MgO, (001)LaAlO3 and (001)SrTiO3. As results of structural characterizations, polycrystalline dendritic layers of La2NiO4+delta tetragonal (or orthorhombic) phase were observed on (001)Si substrates while layers of a perovskite-like cubic structure were observed on the other single crystal substrates. From a high-resolution TEM study of a layer deposited on (001)MgO, such a perovskite-like cubic structure exhibits many planar structural faults likely similar to planes of oxygen vacancies of the La(2)Nio(4+delta) orthorhombic structure. A thin intermediate epitaxial layer of NiO phase was also identified. Using a X-ray texture diffractometer, the layer structure on (001)MgO, (001)LaAlO3 and (001)SrTiO3 was confirmed to be of cubic structure with <100> axes parallel to those of the substrate. The T dependence of the resistivity of a layer deposited on (001)MgO substrate was found to be of a semi-conducting behavior. (C) 2004 Elsevier Inc. All rights reserved.