Optical Properties of ZnxCd1-xSe Single Layers Prepared by Thermal Vacuum Evaporation

Single layers from Zn_xCd_1-xSe with four different compositions and thickness of 400 nm were prepared by thermal vacuum evaporation through alloying of ZnSe and CdSe layers with an equivalent thickness of 0.12, 0.25 and 0.37 nm. The deposition was carried on rotating substrates kept at room temperature. The variation of the layer composition was achieved by changing the ratio of the deposition rates of ZnSe and CdSe. Optical transmission measurements have been carried out in the 400-2.500 nm spectral range and the Swanepoel's approach has been applied in order to obtain the dispersion curves of the absorption coefficient and refractive index. The values of the refractive index determined are equal or a bit higher than those reported by other author for epitaxial layers. Values between 2.0 and 2.31 eV have been determined for the optical gaps which correspond to x-values in the range 0.3-0.6. The obtained results indicate that preparation of films with desired compositions is possible at a precise control of the deposition rate of both materials.