Chemical bonds in intercalation compounds CuTiCh (Ch = S, Te).

A thorough study of the chemical bonding between intercalated copper and host lattice TiCh (Ch = S, Te) was performed. In order to separate the contributions of the copper, titanium, and chalcogen states into the electronic structure of the valence band, photoelectron spectroscopy in nonresonant and resonant (Cu 3p-3d and Ti 2p-3d) excitation modes was used. It is shown that the ionicity of the chemical bond between copper and host lattice is decreased in the TiS → TiSe → TiTe row. In CuTiS, copper atoms form the chemical bond with TiCh host lattice, while in CuTiTe directly with tellurium atoms.