STUDY OF LATTICE VIBRATIONAL MODES IN CUGAS2 BY USING FOURIER-TRANSFORM SPECTROSCOPY

The lattice dynamics of a single crystal of CuGaS2, grown by iodine transport technique, have been studied by using far IR absorption spectroscopy. All the absorption maxima caused by the phonon excitation are compared with the lattice vibrational modes obtained by Raman spectroscopy and by IR reflection techniques. An absorption maximum located at 175 cm-1 cannot be explained with the help of phonon excitation; however this peak can be attributed to the defect frequency originating from the replacement of gallium atom by sulphur in the v17 mode of vibration. The frequency of this defect-induced vibrational mode is calculated by taking a modified molecular model approach, and is found to be 166.9 cm-1, which is in reasonably good agreement with the experimentally observed value of 175 cm-1. © 1979.