Electronic structure of single crystal and highly oriented pyrolytic graphite from ARPES and KRIPES

We present a comparative study of the near fermi-level electronic structure of single crystal and highly oriented pyrolytic graphite (HOPG). Angle resolved photoelectron spectroscopy and angle resolved inverse photoelectron spectroscopy have been used to probe the occupied and unoccupied electronic states, respectively. The band dispersions showed by single crystal graphite along its ΓKΓK and ΓMΓM symmetry directions were found to be in agreement with calculated band structure of graphite. The ππ bands of single crystal graphite were found to have a splitting of ∼0.5eV at the K-point. We also observe the presence of a quasiparticle peak below EF at the K point at low temperature which indicates a strong electron–phonon coupling in graphite. In HOPG, the M and K   points like features were found to be present in the same radial direction due to the superposition of the ΓMΓM and ΓKΓK directions. Results from our angle resolved inverse photoemission spectroscopy present the dispersion of the conduction band states, particularly the lower π⁎π⁎ band. We have also found the presence of some non-dispersive features in both the valence and the conduction bands.