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

Abstract

Fabrications of La 2 NiO 4 + δ thin film layers by liquid-injection metalorganic chemical vapor deposition were tried on different single crystals substrates: (001)Si, (001)MgO, ( 001 ) LaAlO 3 and ( 001 ) SrTiO 3 . As results of structural characterizations, polycrystalline dendritic layers of La 2 NiO 4 + δ 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 + δ 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) LaAlO 3 and (001) SrTiO 3 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.