Influence of annealing processing on dissipation electrical energy, volume, and surface energy loss functions of CZO films

The present study was conducted to investigate the optical constants of copper (Cu)-doped zinc oxide (ZnO) films annealed at different temperatures. The absorption coefficient of the films increased by changing the annealing temperature. The lattice dielectric constant $$ \varepsilon_{L} $$ , concentration of the free-charge carriers, plasma frequency, Spitzer–Fan model, and the waste heat of electrical energy in the films were analyzed using the refractive index n and extinction coefficient k spectra. The results of the study showed that changing the annealing temperature values significantly influences the refractive index and extinction coefficients of CZO films. The increase in the electrical susceptibility $$ \chi_{c} $$ in annealed films can be due to the increased concentration of free-charge carriers in these films. The maximum electrical energy loss (tan δ) in the films as a function of photon energy occurred at 400 °C. The as-deposited films showed minimum volume and surface energy loss functions in their range of optical band gaps. The variations in the phase and group velocity of the films with post-annealing temperature were consistent with the variations in the reduction of the density of free-charge carriers for these films. Films annealed at 600 °C had the maximum root mean square roughness of about 5.62 nm. Films annealed at 400 °C had the maximum extinction coefficients k such that they increased for all ranges of wavelength. $$ \chi_{c} $$ had the maximum values in the films annealed at 600 °C, for all ranges of wavelength, and they increased by increasing the wavelength. The increase in $$ \chi_{c} $$ of the films annealed at 600 °C can be attributed to the increase in the density of free-charge carriers in these films.