Infrared lattice vibration study of CuIn5S8

Abstract

Infrared reflectivity spectra of the spinel compound CuIn5S8 are measured at room temperature in the wavenumber range from 180 to 4000 cm−1. It is found that the spectra are dominated by two strong modes with frequencies and oscillator strengths that are practically equal to those of the corresponding modes in the normal spinels of type AIIIn2S4. A very weak additional mode at 357 cm−1 is ascribed to a secondary tetragonal phase previously observed in as-grown CuIn5S8 single crystals.