Investigation of epitaxial LaNiO3−x thin films by high-energy XPS

Epitaxial thin films of LaNiO3−x were deposited by using a reactive d.c. magnetron sputtering technique. High-energy X-ray photoelectron spectroscopy was used to analyze the composition and valence states of La and Ni in the films after long time aging in atmosphere. The obtained results show the existence lanthanum and nickel in oxide and hydroxide chemical states. The oxygen exists in four chemical states: lattice oxides, hydroxyl groups and in adsorbed water. Comparison of the spectra recorded at normal emission and grazing emission angle revealed that the hydroxyl group's concentration is mostly present at the surface of the film.