Sol-gel Growth of Ni-doped CdS on Glass Substrates: Effect of Spin Coating Speed and Dopant Concentration

Background: In this work, CdS thin films were synthesized by the sol-gel method (spin coating technique) on glass substrates to investigate the optical behavior of the film. Methods: Different substrate spin coating speeds of 2400, 3000, 3600 rpm and different Ni dopant concentrations of 0 wt.%, 2.5 wt.%, and 5 wt.%) were investigated. The optical properties of thin films, such as the refraction index, extinction coefficient, dielectric constant, and optical bandgap energy of the layers were discussed using spectroscopic ellipsometry method in the wavelength range of 300 to 900 nm. Results: It can be deduced that substrate rotation speed and dopant concentration have an influence on the optical properties of thin films by decreasing the rotation speed of the substrate, which results in films with more thicknesses, and more optical interferences were observed in the results. Conclusion: The samples doped with Ni, when compared to pure ones, were found to have more optical bandgap energy.