Optical reflection and Raman studies on mixed crystals of misfit layer compounds

Abstract We have performed optical reflectivity measurements on the mixed crystals of misfit layer compounds (M x La 1− x S)NbS 2 (M: metal = Sn, Pb; 0≤ x ≤1) to estimate the carrier density in conducting NbS 2 layers. The carrier density monotonically increases with the metal content x . The variation of the carrier density with x can be explained in terms of the charge transfer from M x La 1− x S to NbS 2 layers. The influence of the charge transfer on the vibrational properties in the mixed crystals is studied by Raman scattering measurements. The peak frequencies of the A modes confined to the NbS 2 layer shift to the higher energy side with decreasing x . The frequency shifts of the phonon modes suggest that the inter- and intralayer interactions increase with increasing the degree of the charge transfer.