In this paper, optical constants, surface topology, and fractal dimensions of zinc oxide films under different post-annealing temperatures from 400 °C to 600 °C especially were investigated near optical band gap of films so that the maximum value of fractal dimension belongs to film annealed at 500 °C with the value of 2.07. In addition, the relaxation time of dielectric were estimated using their high-frequency dielectric constant while optical band gap were calculated through the cross-point between the tangent of lower and higher values of the photon energy in the plot of relaxation timeenergy. The high-frequency dielectric constant has the maximum value of 21 for film annealed at 400 °C. It can be seen that the free carriers electric susceptibility of films near optical band gap were increased with temperature. Moreover, the film annealed at 400 °C has high dissipation factor.
