Modifying the electronic structure of TiS2 by alkali metal intercalation

Angle-resolved photoelectron spectroscopy has been used to study in situ in tercalation of the layered compound TiS2 with Na and Cs. The intercalation was verified by core-level spectroscopy. The valence bands of pure TiS2 and the intercalated compounds NaxTiS2 and CsxTiS2 were characterized and comp ared to self-consistent LAPW band-structure calculations. Remarkable agreem ent between experimental and calculated bands was found for the dispersion along the layers. The calculations predicted perpendicular dispersion also for the intercalation compounds, although significantly reduced. No signifi cant perpendicular dispersion was seen in normal-emission spectra, which mi ght be an effect of intercalation-induced stacking disorder. Charge transfe r to the TiS2 host layers was evident from the much increased conduction ba nd emission, and from the asymmetric S 2p core-level lineshape after interc alation. The intercalation produced electronic structure changes which are not well described by the rigid-band model, but as these changes occur at a n early stage, the model can still be used, with modified bands, to describ e the continued intercalation.