Raman scattering from GaSxSe1-x

The non resonant Raman scattering spectra of GaSe, GaS and of eight different mixed crystals GaS_xSe_1-x are presented. The frequencies of some vibrational modes shift continuosly from GaSe to GaS indicating that the mixed crystals are homogeneous. The discontinuous shift of some other modes is explained either by the change of the stacking of the layers, or by a ‘two mode’ behaviour as previously observed in other types of mixed crystals. Moreover, local vibrational modes are observed.