STRUCTURAL AND OPTICAL-PROPERTIES OF CD1-XZNXS MIXED THIN-FILMS

Thin films of the general configuration Cd1-xZnXS have been produced b y a chemical deposition process from a reaction mixture consisting of cadmium sulphate, zinc chloride and thiourea. The samples having unifo rm composition have been obtained covering the whole range of Zn-conce ntration from 0 to 0.9. The dependence of energy gap and crystal habit on the composition parameter X has been investigated. The X-ray diffr actograms (XRD) show the most intense reflection as (002) hexagonal or (111) cubic for all the samples. A gradual transformation of cubic la ttice of CdS into the hexagonal has. been observed for the range of co ncentration 0 less than or equal to X less than or equal to 0.3. For X > 0.3, formation of separate phases of both CdS and ZnS have been obs erved. A decrease in grain size with an increase in zinc concentration in CdS has been observed. The optical examination of these samples sh owed a high coefficient of absorption with a shift in absorption edge from 520 to 400 mm and the mode of allowed transition is direct type. A linear increase in the band gap has been observed for lower value of X (X less than or equal to 0.3) whereas a nonlinear dependence is obs erved beyond X = 0.3.