Photoemission experiments on the valence band of transition metal trichalcogenides

Presents a synchrotron radiation photoemission study of the upper-valence-band states of four ZrSe3-structure compounds: ZrS3, ZrSe3, ZrTe3 and HfSe3. The sulphide and selenide spectra exhibit a characteristic five-peak structure in agreement with the calculated ZrSe3 density of states by Myron et al. (1981) and by Bullett (1979). The nature of these features is established by an interplay between the rehybridization of paired-anion ligand orbitals and the hybridization of unpaired-anion states with cation states. The spectrum of ZrTe3 exhibits only three peaks that appear related to three of the sulphide and selenide spectral features. The differences between the sulphide, selenide spectra and the telluride spectra are discussed in terms of the very large distance between paired-anion ligands and neighbour cations in the latter compound