X-RAY PHOTOELECTRON-SPECTROSCOPY OF ZNCL2 BASED GLASSES

X-ray photoelectron spectra of Cl and Zn core electrons have been obtained for crystals (ZnCl2, Cs2ZnCl4, CsCl and BaCl2) and glasses (ZnCl2 and modified ZnCl2 systems containing CsCl and BaCl2). Binding energies of the Cl core electrons of the crystals decrease by about 1 eV in the order ZnCl2, CS2ZnCl4 and CsCl or BaCl2. This is attributed to the difference in bonding nature between Zn-Cl and M-Cl bonds where M = Cs or Ba. Therefore, Cl- ions in different bonding states, i.e. bridging, nonbridging and isolated, are discriminated from each other by the XPS of Cl core electrons; here, the term ''bridging'', ''nonbridging'' or ''isolated'' represent Cl ions which are bound to two Zn2+, one Zn2+, or no Zn2+, respectively. The Cl core electron binding energies of ZnCl2 glass are the same as those of ZnCl2 crystal. However, a decrease is seen in ZnCl2-CsCl-BaCl2 glasses. This is because nonbridging Cl- ions are introduced into the modified glasses. The Cl2p spectra of the modified glasses are successfully decomposed into four Lorentz Gaussian lines, the peak positions of which are close to 2p3/2 and 2p1/2 of bridging and nonbridging Cl- ions in crystals. The binding energies of Zn core electrons decrease for CS2ZnCl4 and the modified glasses. This is explained by the change informal charge of ZnCl4 tetrahedra and the relaxation of the final state.