Infrared analysis of clustering in the II-VI-VI compoundCdSexTe1−x

Infrared reflectivity spectra at 82 K for Bridgman-grown ${\mathrm{CdSe}}_{\mathit{x}}$ ${\mathrm{Te}}_{1\mathrm{-}\mathit{x}}$ crystals (x=0.05–0.35) show the two expected transverse-optical phonon modes and an unexpected third mode. Analysis of the data, using the cluster model of Verleur and Barker, shows that these spectra represent substantial nonrandom clustering of the anions around the cations. The magnitude and x dependence of the clustering is similar to that seen in the related compound ${\mathrm{CdSe}}_{\mathit{x}}$ ${\mathrm{S}}_{1\mathrm{-}\mathit{x}}$ grown at the same temperature, although by a different growth method.