Raman Effect in Wurtzite- and Zinc-Blende-Type ZnS Single Crystals

Raman spectra of wurtzite- and zinc-blende-type ZnS single crystals were excited by a He-Ne laser (6328 \AA{}) and an argon-ion laser (4880 \AA{} and 5145 \AA{}). All the Raman-active long-wavelength phonon frequencies were determined. These are (i) for the cubic modification, TO=276 ${\mathrm{cm}}^{\ensuremath{-}1}$ and LO=351 ${\mathrm{cm}}^{\ensuremath{-}1}$; and (ii) for the hexagonal modification, ${E}_{2}=72$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${E}_{2}=286$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${A}_{1}(\mathrm{TO})={E}_{1}(\mathrm{TO})=273$ ${\mathrm{cm}}^{\ensuremath{-}1}$, and ${A}_{1}(\mathrm{LO})={E}_{1}(\mathrm{LO})=351$ ${\mathrm{cm}}^{\ensuremath{-}1}$. The lowest-frequency ${E}_{2}$ mode of the mixed crystal system ${\mathrm{Cd}}_{x}{\mathrm{Zn}}_{1\ensuremath{-}x}\mathrm{S}$ was studied as a function of $x$, and was found to vary monotonically. The intensity ratio of the LO to the TO band seems to be dependent on the wavelength of the exciting radiation.