Infrared Vibrational Modes and Anisotropy of the Effective Ionic Charge in CuAlSe₂, CuAlS₂, and CuGaSe₂ Crystals

Abstract

Abstract Reflectivity spectra of CuAlS 2 , CuAlSe 2 , and CuGaSe 2 crystals have been investigated in the wave number range 50 to 600 cm −1 for the polarizations E ‖ c and E ⊥ c . The fundamental phonon parameters, the limiting dielectric constants ε ∞ and ε S and the reflectivity spectra contours have been calculated by using classical dispersion relations for both E ‖ c and E ‖ c configurations. The Szigeti effective charges and the relative ion charges of Cu, Al, Ga, Se, S anions and cations have been calculated in dependence on the incident light polarization.