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

Abstract

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 Γ K and Γ M symmetry directions were found to be in agreement with calculated band structure of graphite. The π bands of single crystal graphite were found to have a splitting of ∼ 0.5 eV at the K-point. We also observe the presence of a quasiparticle peak below E F 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 Γ M and Γ K directions. Results from our angle resolved inverse photoemission spectroscopy present the dispersion of the conduction band states, particularly the lower π ⁎ band. We have also found the presence of some non-dispersive features in both the valence and the conduction bands.