Surface stability of epitaxial LaNiO3−δ thin films

Anotacija

Thin LaNiO 3−δ films with pseudocubic (100) preferred orientation were prepared by reactive DC magnetron sputtering and in situ annealed in O2 and vacuum. X-ray photoelectron spectroscopy (XPS) was used to determine the variation in composition of the films under high temperature annealing. The experimental O 1s and La 3d – Ni 2p3/2 spectra of LaNiO3−δ films was analysed in terms of O2−, O−/(OH)−, and weakly adsorbed oxygen species. It was shown that the change in the type of conductivity from metallic to semiconducting one is accompanied by a marked increase in the intensity of the lateral (~531 eV) peak of oxygen. The quantitative analyses of La 3d – Ni 2p3/2 spectra show that the Ni/La concentration ratio significantly decreases after heating above the dehydration temperature. These variations in conductivity and surface composition were attributed to the loss of lattice oxygen with subsequent adsorption of O− and (OH)− anions and weakly adsorbed oxygen species from ambient air. Keywords: rare earth alloys and compounds, oxide materials, XPS, surfaces and interfaces, LaNiO3 thin film