Infrared-active phonons in cubic zinc sulfide

We take advantage of the availability of chemically vapor-deposited zinc sulfide for the purpose of investigating the infrared absorption spectrum of cubic ZnS, at room temperature, and extend the range of currently available measurements into the three-phonon regime. A critical-point analysis of two-phonon events yields a set of accurate zone-edge mode frequencies; they are shown to be consistent with second-order Raman spectral characteristics. The gross features of the three-phonon absorption edge are described in terms of four characteristic frequencies (LO=330, TO=295, LA=193, TA=89 cm−1) and attributed to optical-branch overtones.