Pressure-dependent Raman spectra of Cu2GeS3 and Cu2SnS3

Cu2GeS3 and Cu2SnS3 crystalline samples with monoclinic (space group Cc) structures were fabricated using Bridgman method. The lattice constants, determined from the powder X-ray diffraction pattern, were a= 6.44 angstrom, b= 11.30 angstrom, c= 6.42 angstrom, and beta = 108.44 degrees for Cu2GeS3 and a= 6.65 angstrom, b= 11.57 angstrom, c= 6.66 angstrom, and beta = 109.30 degrees for Cu2SnS3. Cu2GeS3 exhibited eight Raman-active vibration modes at 255 cm(-1), 281 cm(-1), 299 cm(-1), 317 cm(-1), 339 cm(-1), 359 cm(-1), 397 cm(-1), and 422 cm(-1), while Cu2SnS3 showed only four modes at 294 cm(-1), 316 cm(-1), 354 cm(-1), and 374 cm(-1) at ambient conditions. The Raman spectra were also measured at pressures up to 5.31 GPa, and the effects of high pressure on the observed Raman modes were discussed. (C) 2018 Elsevier B.V. All rights reserved.