Heteroepitaxial graphite on 6HSiC(0001): Interface formation through conduction-band electronic structure

I. Forbeaux, J.-M. Themlin, and J.-M. Debever
Phys. Rev. B 58, 16396 – Published 15 December 1998
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Abstract

When annealed at elevated temperatures under vacuum, silicon carbide surfaces show a tendency towards graphitization. Using the sensitivity of empty conduction-band states dispersion towards the structural quality of the overlayer, we have used angular-resolved inverse photoemission spectroscopy (KRIPES) to monitor the progressive formation of crystalline graphite on 6HSiC(0001) surfaces. The KRIPES spectra obtained after annealing at 1400 °C are characteristic of azimuthally oriented, graphite multilayers of very good single-crystalline quality. For lower annealing temperatures, the ordered interface already presents most of the fingerprints of graphite as soon as 1080 °C. The observation of unshifted π* states, which reveals a very weak interaction with the substrate, is consistent with the growth of a van der Waals heteroepitaxial graphite lattice on top of silicon carbide, with a coincidence lattice of (63×63)R30° symmetry. The growth of the first graphene sheet proceeds on top of adatoms characteristic of the (3×3)R30° reconstruction. These adatoms reduce the chemical reactivity of the substrate. A strong feature located at 6.5 eV above the Fermi level is attributed to states derived from Si vacancies in the C-rich subsurface layers of the SiC substrate. This strongly perturbed substrate can be viewed as a diamondlike phase which acts as a precursor to graphite formation by collapse of several layers. In this framework, previously published soft x-ray photoemission spectra find a natural explanation.

  • Received 10 August 1998

DOI:https://doi.org/10.1103/PhysRevB.58.16396

©1998 American Physical Society

Authors & Affiliations

I. Forbeaux, J.-M. Themlin*, and J.-M. Debever

  • Groupe de Physique des Etats Condensés, UMR CNRS 6631, Case 901, Faculté des Sciences de Luminy, F-13288 Marseille Cedex 9, France

  • *Author to whom correspondence should be addressed. Electronic address: themlin@gpec.univ-mrs.fr

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Vol. 58, Iss. 24 — 15 December 1998

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