Background: In this work, CdS thin films were synthesized by 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.%, 5 wt.%) were investigated. The optical properties of
thin films such as refraction index, extinction coefficient, dielectric constant and optical band gap
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 has influenced
the optical properties of thin films. By decreasing rotation speed of the substrate which results in
films with more thicknesses, more optical interferences were appeared in the results.
Conclusion: The samples doped with Ni comparing to pure ones have had more optical band gap