Optical and transport properties of Cd0.8Zn0.2S:Cu compounds prepared by modified chemical co-precipitation method

Cd_0.8Zn_0.2S bulk compound doped with different concentrations of copper have been prepared by chemical co-precipitation (CCP-I) and modified CCP method (CCP-II). The structural, optical and electrical properties of Cd_0.8Zn_0.2S:Cu compounds grown by these methods have been investigated by using XRD, SEM, EDAX, UV spectroscope and DC electrical conductivity techniques. X-ray diffraction studies on Cd_0.8Zn_0.2S compounds doped with various mole% of copper revealed that they possessed polycrystalline nature with hexagonal structure. SEM micrographs taken on samples grown by CCP-I showed that the crystallites have needle like shape and no such regular shape was observed on CCP-II grown samples and in both of them the crystallite size varied differently with the variation in the concentration of copper. The energy gap of a sample grown by CCP-II, evaluated from optical absorption studies, are more than that of the sample grown by CCP-I. This may be attributed to the variation observed in the crystallite sizes of the respective sample grown by two methods. Further, the electrical conductivity variations in CCP-I and II samples were explained based on E_g value, crystallite size and grain boundary conduction in the samples. The activation energies of both CCP-I and II samples were explained on the basis of the differences in their preparation methods. Finally, it was concluded that the CCP-II method is more suitable to grow Cd_0.8Zn_0.2S:Cu compounds with uniform average crystallite size and energy gap for low doping concentration of Cu (∼4 mole%).