Localization and charge density wave transformation in Cs intercalated 1T–TaSe2

Cs was adsorbed at room temperature onto the (0001) cleavage planes of 1T–TaSe2. The deposited Cs forms no metallic overlayer, but intercalates after an initial adsorption stage into the van der Waals gap of the layered crystal. A limit of the relative concentration ratio cCs/cTa of ca. 60% is observed. Due to the electron transfer associated with the intercalation the charge density wave induced p(13×13)R13.89° superstructure exhibits a phase transition to a c(23×4)rect. structure. As a further consequence of the intercalation a metal to semiconductor transition occurs. The change in the electronic structure could not be interpreted within the rigid band model, but is tentatively explained by an localization effect, caused by the charge density wave phase transition.