Raman scattering and X-ray diffraction study in Cu2GeSe3

A combined study of X-ray diffraction data and micro-Raman scattering of Cu2GeSe3 is presented. From the analysis of the X-ray data it is confirmed that this compound crystallizes in an orthorhombic cell, space group Imm2Imm2. 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 B2 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 A2 modes. Lines at 135, 235 and 254 cm−1 are attributed to A1 or B1 modes. The highest phonon frequency band, observed at 385 cm−1, probably comprises the remaining A2 mode and an overtone from the strong line at 189 cm−1.