Conduction and localization in incommensurate misfit layer compounds

We investigated transport properties and optical reflectivity of incommensurate misfit layer compounds (LaS)(1.16)VS2 and (CeS)(1.19)(TiS2)(n) (stage index n = 1,2). Electrical conduction measurements revealed that (CeS)(1.19)(TiS2)(n) is metallic while (LaS)(1.16)VS2 is non-metallic. The existence of a short-range scattering process of the order of 10 Angstrom was indicated for both electrons and phonons in (CeS)(1.19)(TiS2)(n), suggesting that the local lattice modulation induced by the incommensurate structure has an important contribution to the conduction of electrons and phonons. Optical reflectance spectra for (LaS)(1.16)VS2 exhibited the enhancement of the carrier scattering, indicating a different character of the conduction band of (LaS)(1.16)VS2 in comparison with metallic (CeS)(1.19)(TiS2)(n). We propose the possibility of carrier localization in (LaS)(1.16)VS2 in relation to the incommensurate structure of these compounds.