Conduction-band structure of graphite studied by combined angle-resolved inverse photoemission and target current spectroscopy

The dispersion of the conduction states parallel to the basal plane of highly oriented pyrolitic graphite was investigated up to 28 eV above the Fermi level by inverse photoemission with the use of a new highly efficient band-pass photon detector. The remarkable modulation of the absorbed target current as a function of the kinetic energy of the incident electrons is interpreted as an elastic reflection phenomenon. As in inverse photoemission, the current spectra show a strong dependence on the angle of incidence and provide additional information about the conduction-band structure from the vacuum level up to 38 eV above the Fermi level. The results of both methods are compared with recent band-structure calculations. Besides several {π} and {σ} bands, an image-potential state is observed just below the lowest {σ} band. The extraordinary width of this {σ} band along the c axis was directly examined by current spectroscopy.