Study of the effects of annealing temperature on the properties of CuO/NiO thin films grown by Physical Vapor Deposition (PVD) technique for photovoltaic applications

Copper oxide/nickel oxide (CuO/NiO) thin films were deposited on glass substrates by the Physical vapor deposition (PVD) Technique and then annealed at different temperatures of 280°C, 320°C, and 360°C for 2 hours. The effects of the annealing temperature on the optical and structural properties of the CuO/NiO thin films were studied. X-ray diffraction suggests that a Monoclinic and cubic structure with a strong (1 1 1) and (2 2 0) for each of CuO and NiO respectively preferred orientation which remained the same with different heat treatments. And the crystallite size increases with annealing temperature, and the lattice constants of CuO/NiO thin films were also obtained from XRD data.  Also, it is found that with the increase of different heat treatments, the optical absorption spectra showed that with increasing annealing temperatures, the absorption coefficient decreases, and the edge absorption shifts to longer wavelengths. The direct optical band gap decreases from 2.88 eV, 2.84ev to 2.74 eV for as-deposited and annealed CuO/NiO thin film at 280 °C, 320 °C, and 360 °C respectively.