ELECTRONIC-STRUCTURE OF THE MISFIT-LAYER COMPOUNDS PBTIS3 AND SNNBS3

The compounds PbTiS3 and SnNbS3 may be classified as misfit-layer compounds with compositions (PbS)1+xTiS2 or (SnS)1+xNbS2. Their structure is such that a double layer of PbS or SnS with the TlI structure is inserted into each van der Waals gap of a layered transition-metal disulfide. They may be regarded as intercalation compounds or as materials having a one-dimensional superlattice with an atomic-scale repeat distance. X-ray-photoemission-spectroscopy, x-ray-absorption-spectroscopy, and reflection-electron-energy-loss-spectroscopy spectra are presented and the electronic structures are discussed. It is found that charge transfer occurs from the PbS or SnS layers to the transition-metal disulfide slabs, but the interlayer interaction is so small that the overall features of the valence and conduction bands of each layer are considered to be almost unchanged from those of the bulk compound.