Copper nickel oxide (CuNiO2) films were deposited on glass and silicon substrates using RF magnetron sputtering of equimolar Cu50Ni50 alloy target at different sputter powers in the range of 3.1–6.1？W/cm2. The effect of sputter power on the chemical composition, crystallographic structure, chemical binding configuration, surface morphology, and electrical and optical properties of CuNiO2 films was investigated. The films formed at sputter power of 5.1？W/cm2 were of nearly stoichiometric CuNiO2. Fourier transform infrared spectroscopic studies indicated the presence of the characteristic vibrational bands of copper nickel oxide. The nanocrystalline CuNiO2 films were formed with the increase in grain size from 75 to 120？nm as the sputter power increased from 3.1 to 5.1？W/cm2. The stoichiometric CuNiO2 films formed at sputter power of 5.1？W/cm2 exhibited electrical resistivity of 27？？cm, Hall mobility of 21？cm2/Vsec, and optical bandgap of 1.93？eV. 1. Introduction Cuprous oxide (Cu2O) is a p-type semiconducting oxide material with a direct bandgap of about 1.9–2.2？eV and has a wide range of applications in the field of gas sensors, solar cells, thin-film transistors, and catalysts [1–4]. Cu2O is the base for many p-type transparent conducting oxides (TCOs) to form CuMO2 delafossites (M = Al, Cr, B, In, Ga, etc.), which are thought to retain the valence band features and conduction mechanism of Cu2O [5]. Nickel oxide (NiO) thin films are very much attractive for the antiferromagnetic layers, electrochromic devices, and p-type transparent conducting oxide and functional layers in chemical sensors [6–8] because of their chemical stability along with suitable optical, electrical, and magnetic properties. Chen et al. [9] studied the change in the valence of Ni from Ni2+ to Ni3+ by incorporating copper into the NiO films formed by reactive sputtering of nickel target with varied copper concentrations of 10 and 18？at%. Moghe et al. [10] noticed that the crystallite size of the films decreased from 18.1 to 15.2？nm and that the optical bandgap decreased from 3.20 to 2.96？eV with the increase of copper concentration from 0 to 10% in NiO films formed by spray pyrolysis. The electrical resistivity of the films also decreased with the increase in the content of copper in NiO films. Yang et al. [11] reported electrical resistivity of 0.19？？cm and optical bandgap of 3.7？eV in p-type Ni0.9Cu0.1O films formed by pulsed plasma deposition. Miyata et al. [12] deposited p-type Cu2O–NiO films with various concentrations of Cu2O by RF magnetron sputtering and found electrical
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