Formation of mixed phases and mutual chemical analogs in ZnTe–CdS films

Structure and band gap studies on ZnTexCdS1−x films (x=0.0, 0.6, 0.5, 0.6 and 1.0) formed on glass substrates by vacuum evaporation (Ts=303) are reported. All films were polycrystalline in nature with wurtzite structure. However, in films of mixed compositions two wurtzite mixed phases were observed indicating the presence of solvus region in ZnTe–CdS system. The lattice parameters obtained from XRD studies and the band gaps obtained from transmission studies were found to lie outside the range of those of the end compounds. Interestingly, both the lattice parameter and band gap values of films of mixed compositions were found to lie in the range of ZnS and CdTe indicating that ZnTe–CdS system has been converted into its mutual chemical analog ZnS–CdTe system. The results of the present investigation also demonstrate that CdTe and ZnS are miscible in the middle composition region.