Infrared lattice vibrations of CdIn2Se4

Infrared reflectivity spectra of CdIn₂Se₄ single crystals are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹ for the polarization directions E ⟂ c and E ‖[112]. The spectra reveal two vibrational modes with nearly the same frequencies for both polarization directions. The frequencies of the modes with highest energy compare well with the corresponding mode frequencies in ZnIn₂Se₄, CuInSe₂ and AgInSe₂. It is concluded that these modes are sphalerite-like in nature and that their frequencies are essentially determined by the properties of the In Se bond.