Raman scattering and X-ray diffraction study in Cu2GeSe3

Abstract A combined study of X-ray diffraction data and micro-Raman scattering of Cu 2 GeSe 3 is presented. From the analysis of the X-ray data it is confirmed that this compound crystallizes in an orthorhombic cell, space group I m m 2 . From Raman spectra, optical modes are identified and their possible symmetry assignments are suggested. Peaks at 212, 266 and 300 cm −1 , tentatively assigned to B 2 modes, agree well with those reported from infrared reflectivity. The most strong peak at 189 cm −1 which is only Raman active is assigned to one of the two A 2 modes. Lines at 135, 235 and 254 cm −1 are attributed to A 1 or B 1 modes. The highest phonon frequency band, observed at 385 cm −1 , probably comprises the remaining A 2 mode and an overtone from the strong line at 189 cm −1 .