Angle-resolved ultraviolet photoelectron spectroscopy of the unoccupied band structure of graphite

The energy dispersion of conduction (or unoccupied) bands of graphite has been studied by angle-resolved ultraviolet photoelectron spectroscopy. Photoemission peaks originating in the conduction bands were successfully separated from those of the valence bands by comparing two sets of angle-resolved ultraviolet photoelectron spectra excited by the He and He resonance lines. Three conduction bands were found in the energy range of 7–13 eV above the Fermi level and one of them showed a remarkable energy dispersion in the ΓKHA plane in the Brillouin zone. The present experimental results have been compared with the results of earlier experiments using photoelectron, secondary-electron, electron-energy-loss, photoyield, and inverse photoelectron spectroscopies as well as with some theoretical calculations. The usefulness of angle-resolved (secondary) photoelectron spectroscopy to study unoccupied band structure has been demonstrated.