Infrared Lattice Reflection Spectra of II-VI Compounds

Abstract
The reflection spectra of cubic ZnS, ZnSe, ZnTe and CdTe, hexagonal CdS, CdSe and ZnS were measured in the spectral region from 20 µm up to about 100 µm. The Reststrahlen bands thus obtained were analysed using Drude dispersion relation and the following values of transverse optical mode frequency (νt) at the zone center were determined: cubic ZnS, 282 cm-1; ZnSe, 207 cm-1; ZnTe, 177 cm-1; hexagonal CdS, 234 cm-1and 241 cm-1for the vibrations parallel and perpendicular to thecaxis respectively; hexagonal CdSe, 167 cm-1for unpolarized radiation; hexagonal ZnS, 274 cm-1for the vibrations of both polarizations. The longitudinal optical mode frequency at the zone center, the Szigeti effective charge and the other dispersion parameters were also obtained. νtwas also obtained from the transmission spectrum of an evaporated thin film and was found to be in good agreement with the value obtained from the reflection analysis.

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