The free carriers loss, free carriers susceptibility, and optical VEL and SEL functions in ZnO films doped by Cu, Al, and Cu-Al composite nanoparticles

The purpose of this work is to investigate the optical constants of ZnO films doped by Cu, Al, and Cu-Al nanoparticles. The reflectance and the transmittance spectra measurements were applied for calculating these optical constants in the range of 200–2500 nm. It can be seen that ZnO films doped with Al nanoparticles have a maximum value nanoparticles size of about 23.73 nm. With increasing annealing temperature for all wavelength range, due to the improvement of crystalline structure and hence decreasing defects, the extinction coefficient of films decreased. The theoretical extrapolation of e1 versus λ2 at low wavelengths values provides the dielectric constant e∞ and for the ZnO films doped with Cu nanoparticles, it has a maximum value of 4.61. The ZnO films doped by Al nanoparticles have a minimum value of $${\chi }_{c}$$ in all energy range. The dissipation factor tan δ of ZnO films doped by Cu nanoparticles especially in high energy has a maximum value. SEL functions in ZnO films doped by Cu nanoparticles have the maximum value.