Direct observation of oxygen vacancy and its effect on the microstructure, electronic and transport properties of sputtered LaNiO3 − δ films on Si substrates

Highly (100)-oriented LaNiO3 films with different oxygen content were deposited on Si substrates by radio frequency sputtering and post-annealed in oxygen and vacuum conditions. The formation of oxygen vacancies is directly observed by a decrease of lattice oxygen ratio in O 1s core-level photoelectron spectroscopy. X-ray diffraction measurement indicates that low oxygen pressure during the deposition or annealing process has a significant influence on the lattice constant of LaNiO3 films. Further valence-band spectra and transport measurements demonstrate that the oxygen vacancies also have a significant influence on the electronic structure and transport behaviors of final LaNiO3 films.