Raman and infrared spectra of the(CuInSe2)1−x−(2ZnSe)xsystem

Abstract

The effects of crystal symmetry and disorder on the infrared and Raman spectra of the solid solution ${\left(\mathrm{Cu}\mathrm{In}\mathrm{Se}\right)}_{1-x}-{\left(2\mathrm{}\mathrm{Zn}\mathrm{Se}\right)}_x$ were studied. This system crystallizes in the chalcopyrite structure for $x\le 0.43$ and in the zinc-blende structure for $x\ge 0.48$. Significant differences were found for the spectra of the mixtures and the spectra of the end compounds. Large shifts and broadening in the infrared reststrahlen and Raman bands indicate the excitations of vibrational modes with $\overrightarrow{\mathrm{k}}\ne 0$ induced by substitutional disorder. As a result, the spectra of the mixtures reveal the density of vibrational states throughout the Brillouin zone. The symmetries of the observed modes were assigned from the polarization and composition dependences.