OPTICAL AND ELECTRICAL-TRANSPORT STUDIES ON LITHIUM-INTERCALATED TIS2

Optical and electrical-transport measurements carried out on pure and lithium-electro-intercalated TiS2 single crystals are presented. Results for equilibrated samples are shown as a function of temperature and lithium concentration. Resistivity and Hall-coefficient measurements show that upon intercalation there is an increase in the carrier concentration and a temperature-independent Hall coefficient, in good agreement with previously reported transport measurements. The infrared-reflectivity spectra clearly show a large shift of the Drude edge. An analysis of the optical data using a single-carrier Drude model gives various parameters, such as the plasma frequency, the damping factor, and the high-frequency dielectric constant. The carrier concentration and mobility are deduced and compared with electrical data. The results are consistent with the assumption of an increased d-band filling and a high degree of charge transfer.