Spectroscopie photoelectronique ESCA (XPS) de chalcogenures de thallium

Abstract The thallium chalcogenides Tl 2 S, TlS, Tl 2 Se, TlSe, Tl 5 Te 3 , TlTe, and Tl 2 Te 3 have been investigated by using the X-ray photoelectron spectroscopy approach. Measurements from both the core and the valence levels are reported. In the thallium telluride series the relative variations of the core level binding energies and the evolution in the valence band structure are consistent with an increase of ionic contribution from Tl III to Tl I compounds. Valence band structures of thallium sulfides and thallium selenides are analyzed with regard to the crystallographic structures and particular attention is devoted to the structure derived in major part from the Tl6 s level. An explanation of the variations observed for this structure in various compounds is advanced, taking account of the peculiarity of Tl6 s level participation in the chemical bonds.