In this work, we study the optical properties of the Nickel doped cupric oxide Ni-CuO thin films with Ni various doping concentrations (0, 20, 30, 50, 70, and 80%), at two different annealing temperatures; 200 and 400 °C. The absorbance and optical bandgap for the films are calculated
and compared. We find that all films exhibit clear peaks in the visible range, with the increase in the absorptivity via increasing both annealing and Ni concentration. We also find that the annealing affects the shape of the absorbance peaks to be narrowed and blue shifted. Investigation
on the direct bandgap energy shows that all films exhibit large direct gap; ranging from 3.87 to 4.01 eV. For non-annealed films, direct bandgap increases with increasing the Ni concentration, while for the annealed samples, the direct bandgap generally decreases by annealing, and with increasing
the doping concentration. For the indirect bandgap analysis, the calculated values of the bandgap are ranging from 0.62 to 1.96 eV. We find that for non-annealed films, the indirect bandgap increases with increasing the doping concentration, while after annealing, the bandgap decreases with
increasing the doping concentration for the annealing at 200 and 400 °C, with more decreasing in the gap at 400 °C.
