Modulation of Ni valence in p-type NiO films via substitution of Ni by Cu.

10 and 18 at. % copper incorporated NiO films were deposited by reactively sputtering from Ni targets covered with Cu strips of different sizes. A change in the valence of Ni from Ni2+ to Ni3+ is found by x-ray absorption near edge structure analysis after incorporating Cu into the films. All NiO films exhibit p-type conductivity, either without or with Cu additives. However, as compared with the pure NiO films, the carrier concentration of the films incorporating Cu increases, while the resistivity and mobility decrease. This study not only discusses the connections among the physical properties of the NiO films with different Cu contents but also clarifies the role of Cu additives in the NiO films. [ABSTRACT FROM AUTHOR]