STAGE DEPENDENCE OF PHONONS IN MISFIT LAYER COMPOUNDS (MS)(NBS2)(N) (M=SN,PB N=1,2)

Misfit layer compounds (MS)(NbS2)(n) (M = Sn,Pb; n = 1, 2) are compose d of two types of layers MS and NbS2. Raman spectra of these compounds have been measured for stage-1 (n = 1) and stage-2 (n = 2) compounds and compared with those of pristine NbS2 and other misfit layer compou nds. The intralayer E modes of the NbS2 layer for (MS)(NbS2)(n) shifts upwards relative to 2H- and 3R-NbS2 and the amount of the shift is la rger for the stage-1 compounds than the stage-2 compounds. This result is interpreted in terms of the charge transfer (CT) from the MS layer to the NbS, layer. The extra phonon modes observed for (RS)(NbS)(2) ( R = La,Ce) which become Raman active by the breakdown of the mirror sy mmetry of the NbS2 layer are not observed for (PbS)(NbS2)(2) because t he amount of CT is considerably smaller for the Pb compounds than the La and Ce compounds.