1977/02/15 by H. R. Chandrasekhar, R. G. Humphreys, R.G. Humphreys +3 · 2 citations
Engineering · Materials Science · #Chalcogenide Semiconductor Thin Films #Phase-change materials and chalcogenides #Solid-state spectroscopy and crystallography
paper · doi:10.1103/physrevb.15.2177
openalex publication_date 1977/02/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
The results of Raman scattering and infrared reflectivity measurements on the IV-VI layer-type semiconductors SnS and SnSe are presented. The infrared-active TO, the associated LO-phonon frequencies, and the dielectric constants for all three principal polarizations have been determined from a Kramers-Kronig analysis of the reflectivity data. The symmetries of the zone-center phonons observed in the different polarization configurations are in agreement with the group-theoretical analysis of the D2h16 space group of these compounds. Despite the center of inversion symmetry in this structure, some infrared- and Raman-active modes are found to be nearly degenerate, suggesting the importance of the layerlike character in these compounds as in the isomorphic GeS and GeSe. A comparison of the phonon frequencies of the corresponding modes in the spectra of SnS and SnSe, or GeS and GeSe, indicates that the frequencies vary as a power (-2.2) of the lattice constant.