Effect of annealing on electrical and structural properties of LaNiO3−δ thin films

Thin LaNiO3−δ films with pseudocubic (1 0 0) 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 spectrum of LaNiO3−δ films was analyzed in terms of “O2−”, “O−”/“(OH)−”, and weakly adsorbed oxygen species. It was shown that the change in the type of conductivity from the metallic to the semiconducting one is accompanied by a marked increase in the intensity of the lateral (∼531 eV) peak of oxygen. These variations in conductivity and surface composition were attributed to the loss of lattice oxygen with subsequent adsorption from ambient air “O−” and “(OH)−” anions and weakly adsorbed oxygen species.