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O: Oberflächenphysik

O 13: Postersitzung (Adsorption auf Oberfl
ächen, Oberfl
ächenreaktionen, Elektronische Struktur, Epitaxie und Wachstum, Halbleiteroberfl
ächen und Grenzfl
ächen, Oxide und Isolatoren)

O 13.76: Poster

Montag, 26. März 2001, 19:00–22:00, Foyer zu B

Dynamic Properties of SiC Surfaces — •F.S. Tautz¹, T. Balster², H. Ibach², and J.A. Schaefer¹ — ¹Institut für Physik, TU Ilmenau, PF 100565, 98684 Ilmenau — ²Institut für Grenzflächenforschung und Vakuumphysik, Forschungszentrum Jülich, 52425 Jülich

In this contribution, we present our comprehensive experiments concerning the dynamical properties of SiC surfaces, as revealed by the inelastic surface scattering of electrons (high resolution electron energy loss spectroscopy or HREELS). We have investigated surfaces of three different polytypes, namely the cubic 3C-SiC(100) and the hexagonal 4H- and 6H-SiC(0001) surfaces, and four of the most common reconstructions, the cubic (2×1) and c(2×2) and the hexagonal (3×3) and (√3×√3)R30^∘ phases. We present a systematic investigation of the dispersion of the Fuchs-Kliewer phonon in the vicinity of the Γ-point, including the dependence on surface reconstruction for which a semi-quantitative model is suggested. Furthermore, the adsorption properties of atomic hydrogen on the various surfaces are discussed. On hydrogen exposure, backfolded surface phonons are suppressed and Si-H stretching, bending and rocking vibrations are observed for the Si-terminated surfaces, while a frequency-split C-H stretching vibration is registered for the C-terminated c(2×2) phase. The experiments on the (√3×√3)R30^∘, (3×3) and (2×1) phases moreover reveal systematic chemical shifts of Si-H stretching frequencies which are discussed in terms of the respective structural models.