HIGH-ENERGY ANGLE-RESOLVED SECONDARY-ELECTRON EMISSION-SPECTROSCOPY OF HIGHLY ORIENTED PYROLYTIC-GRAPHITE

The angle-resolved secondary-electron emission (ARSEE) spectra of highly oriented pyrolytic graphite have been measured in the 7-70 eV electron kinetic energy range. A peak observed at approximately=59 eV with K/sub ///=1.35-1.65 AA-1 was tentatively explained within a semiempirical approach based on a free electron parabola with an inner potential of -16.2 eV (relative to the vacuum level) which crosses the M point at 59 eV. From the crossing of the free electron parabola with the zone centre peaks at 16 eV and 28.5 eV were independently described. These results suggest that the empty density of states for large kinetic energies are well described by a free electron parabola. In the energy range below 30 eV good agreement was obtained with previously published ARSEE experiments. XPS and AES measurements were performed to verify that the 59 eV peak did no originate from an impurity level. After argon ion bombardment the fine structure observed in the ARSEE spectra of HOPG was completely removed.