Unoccupied electronic states of graphite as probed by inverse-photoemission and tunneling spectroscopy

Abstract

The unoccupied electronic bulk and surface states of graphite are probed by inverse photoemission at hν=9.7 eV and by tunneling spectroscopy, and the results from each method are found to agree very well with each other. In particular, ${\pi }^{\mathrm{*}}$ bands at the bulk Q point are found at $E_F$+1.7 eV. Extrinsic surface states (or defect states) are found around $E_F$+2.5 eV, which can be quenched by activated hydrogen or oxygen and by water at low temperatures, but are also dependent on surface preparation. In contrast, the feature at $E_F$+3.5 eV is left unaffected, questioning an interpretation in terms of intrinsic surface states. Rather, we associate it with the bottom of the three-dimensional interlayer band.