Abstract
The authors have performed weight-gain resistivity Hall effect and room-temperature optical transmission measurements on the layered-structure group IV transition-metal dichalcogenides, TiS2, TiSe2 and ZrS2 and on there hydrazine (N2H4) intercalation complexes. They find good metallic behaviour for the intercalated compounds, with room-temperature carrier concentrations of the order of 1022cm-3. This increase in carrier concentration over that in the pristine materials is explained in terms of a charge transfer process from the intercalated hydrazine molecules to the 'd' band of the host, within the framework of a rigid-band model. The mechanism of the charge transfer process is discussed and is thought to be through covalent bonding between the nitrogen lone-pair orbitals of the hydrazine molecules and some host layer states which are probably the chalcogen 'p' states. Apart possibly from the hydrazine intercalation complexes of ZrS2, which show a weak anomaly at about 275 K in the resistivity data, no firm evidence has been found for any charge-density-wave distortions in these intercalation complexes.