IN-SITU INTERCALATION OF THE LAYERED COMPOUNDS TIS2, ZRSE2 AND VSE2

We report photoelectron spectroscopy studies of the valence band struc ture of the layered compounds TiS2, ZrSe2, and VSe2, and of changes in duced by in situ intercalation with Cs. The pure compounds crystallize with the same structure, the 1T-CdI2 structure, but their electronic properties are different; TiS2 is a narrow-gap semiconductor (E(g) sim ilar to 0.2 eV), ZrSe2 is a semiconductor (E(g) similar to 1 eV) and V Se2 is a semimetal. Despite their different electronic properties, the results show that the character of their valence bands changes from 3 D to 2D upon intercalation with Cs. The observed changes, supported by LAPW band calculations, go far beyond the rigid band model.