Characterization of DC reactive magnetron sputtered NiO films using spectroscopic ellipsometry

► Ni-rich NiO films and relatively pure NiO film were prepared by magnetron sputtering. ► The partial pressure of oxygen is a key condition for growing NiO films. ► Optical properties of the NiO films were investigated by spectroscopic ellipsometry. ► The partial pressure of oxygen influences the thickness and roughness of NiO films. ► Direct gap energy and indirect gap energy of the NiO films are also influenced.