Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 13: Electronic structure II

O 13.7: Vortrag

Montag, 23. März 2009, 16:30–16:45, SCH A216

Electron and Phonon Density of States of HOPG by Scanning Tunnelling Spectroscopy — •Norbert Maurer, Carsten Tröppner, and M. Alexander Schneider — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen

Motivated by the current interest in few-layer graphene and the widespread use of graphite as substrate we investigated the electronic structure of highly ordered pyrolytic graphite (HOPG) by low-temperature Scanning Tunnelling Spectroscopy in liquid Helium at 4.2K.

We find that the main features of the differential conductance (dI/dV) signal can perfectly be explained by a total density of states calculation as e.g. obtained from a TB-fit to the graphite band structure [1]. However, some of these features induce a structure in the second derivative (d²I/dV²) signal. Hence both, first and second derivative signals have to be evaluated carefully to extract signatures of inelastic excitations [2]. We discuss the spatial dependence of electronic and inelastic contributions to the tunnelling conductance at step edges and within the HOPG unit cell.

[1] A. Grüneis, et al., arXiv:0808.1467v2 [cond-mat.mtrl-sci] [2] L. Vitali, et al., Phys. Rev. B 69, 121414 (2004)