Photoelectron spectroscopy study of the electronic structure of the incommensurate intergrowth compounds (SbS)1.15(TiS2)n with n=1,2

Abstract

The electronic structure of the inorganic misfit-layer compounds (SbS)1.15(TiS2)n (n=1,2) has been investigated using X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and X-ray absorption spectroscopy (XAS). These compounds are built of alternating modulated double-layers of SbS with the NaCl-type structure and sandwiches TiS2 (for n=1) or paired sandwiches TiS2 (for n=2) with IT-TiS2 structure. The XPS spectra of the Sb 3d core levels show a splitting of 1.1 eV, indicating two states for Sb, corresponding to the two types of Sb atoms present in the crystal structure. The XPS of 2s and 2p of sulphur atoms are a superposition of the spectra of S in SbS and in TiS2. The valence band spectrum is mainly from the S 3p bands; a small peak just below the Fermi energy is attributed to electrons in the Ti 3d t2g conduction band. The Ti 2p X-ray absorption spectrum shows structure, due to multiplet and crystal field interactions. The electronic structures of the misfit-layer compounds can be considered to be a superposition of the electronic structures of the two subsystems SbS and TiS2, but with energy bands broadened due to the incommensurate modulation.