Optical Characterization of Sputter Deposited CdS Thin Films and Measurement of Deposition Rate

Thin film Cadmium Sulfide (CdS) is a common n-type heteropartner for thin film Cadmium Telluride, Copper Indium Gallium Selenium and Copper Tin Zinc Sulfide based solar cells. This work reports the optical properties of CdS thin films which were synthesized onto soda-lime glass substrate by RF magnetron sputtering technique for different RF power. Analyzing the interference fringe pattern of the transmittance spectra and using the methodological framework of Swanepoel method, the film thickness as well as the deposition rate versus RF power characteristics has been deduced. The estimated thickness of the deposited CdS films were compared with the measured thickness by Dektak profilometer and found satisfactory. The deposition rate versus RF power characteristics offers an optimized recipe for fabricating CdS thin films of controlled thickness. In addition, optical energy bandgap, absorption coefficient and wavelength dependent complex refractive index have been calculated. The calculated bandgap energy values of the as-grown CdS films are around 2.42 eV to 2.44 eV and the complex refractive index lies the range of 2.35 to 2.50. Using this data researchers will be able to deposit CdS films of controlled thickness according to the needs.