Composition and substrate temperature dependence of structural and opticalstudies on ZnSexCdS1-x alloy films

Thin (t - 0.60 mum) films of ZnSexCdS1-x were formed by vacuum evaporation on glass substrates held at 350 and 470 K. XRD studies showed that all the films were polycrystalline in nature. Films with x less than or equal to 0. 70 were hexagonal whereas films with x greater than or equal to 0.80 were c ubic in structure. The structural transition was in the range 0.70 < x < 0. 80. The lattice parameter was higher in films formed at a higher temperatur e. The lattice parameter followed Vegard's law. Grain size increased with s ubstrate temperature. From the optical transmission spectra recorded in the wavelength range 300-2500 nm, the extinction coefficient, refractive index and band gaps were obtained. Band gap values showed a downward bowing with 'x' with a bowing parameter of similar to0.40 eV. (C) 2001 Elsevier Scienc e B.V. All rights reserved.