Effects of Concentration on the Properties of Zn-doped Cadmium Sulphide Thin Films

Thin films of cadmium sulphide (CdS) were grown using the SILAR (successive ionic layer and reaction) technique. The films were then doped using Zinc (Zn) impurities at different concentrations. The effect of the different concentrations on the properties of the films are reported. The films were characterised using a X-ray diffractometer to investigate the structural properties of the layers. The results show that an increase in the doping concentrations resulted in a corresponding increase in the crystallinity of the layers. The layers crystallised with the cubic structure. Data extracted from the XRD analysis were used to deduce other important structural parameters such as the grain size, strain, and the number of crystallites in the films. These structural parameters deduced from the XRD studies where found to decrease with an increase in the doping concentrations. The film thickness measured using the gravimetric method were found to increase with an increase in the concentration of the dopants. The film thickness was in the range 0.414 nm to 0.546 nm. The refractive index varied between 1.0 to 1.6, increasing with an increase in the photon energy at the different concentrations up the critical wavelength and then decreased.