INVERSE-PHOTOEMISSION AND PHOTOEMISSION SPECTRA OF THE PBS(001) SURFACE

The inverse photoemission spectra of lead sulphide have been investiga ted in the energy range 15 - 33 eV of normal incidence electrons. In a ddition the angle-resolved photoemission spectra have been studied usi ng synchrotron radiation. The sample crystals have been cleaved in UHV and the crystal structure has been observed by LEED to correspond the (1x1) surface geometry. The band structure to the direction Gamma - X has been determined below and above the Fermi-level from the photoemi ssion and the inverse photoemission spectra. The prominent dispersion of one occupied band is clear but the others are markedly flat. The un occupied bands show quite well behaving dispersion. There are no bands crossing the Fermi-level in the Gamma X direction displaying the band gap 3.6 eV. General shapes of the experimental band dispersions agree satisfactorily with those predicted by theoretical calculations, but the binding energies of the bands show clearly some disagreement, espe cially for the lowest bands.