LAUSR

This work focus on the oxidation states of nickel in NdNiO3, Nd2NiO4, and NiOx thin films deposited by reactive magnetron sputtering. Thin films with a high Ni3+ content have been reached in the ternary oxides using a soft subsequent annealing in air. In order to understand the presence of Ni3+ oxidation state, the present work establishes a comparative study between the NiOx and Nd–Ni–Ox thin films deposited at room temperature in reactive conditions using different oxygen partial pressures. Crystallographic phases have been systematically identified by X-ray diffraction showing crystallized NiOx and amorphous thin films in the case of Ni and Nd cosputtering. The ionization state of Ni ions has been tracked by X-ray photoelectron spectroscopy. Analyses confirm the presence of Ni2+ in NiOx films whereas Ni3+ is systematically observed in Nd–Ni–Ox films highlighting the key role of Nd element during the deposition. The electron donor character of Nd3+ on Ni3+ via O 2p states by an inductive effect is clear...