ELECTRONIC-STRUCTURE OF ZNF2, CDF2, AND HGF2 STUDIED BY ULTRAVIOLET PHOTOELECTRON-SPECTROSCOPY

The results of a photoelectron study using 40.81-eV photons of the outermost bands of the group-IIB-metal fluorides ZnF2, CdF2, and HgF2 are reported. The relaxation-corrected experimental values for the energy separation and absolute binding energies of the outermost levels and the corresponding values given by the fully ionic crystal model are found to be in good agreement for CdF2 and approximate agreement for HgF2. Assignment of relaxation energies for ZnF2, of similar magnitude to those for HgF2, also results in approximate agreement between experimental data for this compound and the corresponding ionic-model predictions. The valence-band widths of a number of MF and MF2 compounds, including rocksalt, fluorite, rutile, and tetragonal crystal types, are shown to be a function of d-2 (d is the bond length) and are characterized by a valence-band index that is independent of crystal type. © 1979 The American Physical Society.