Regensburg 2002 – wissenschaftliches Programm
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O: Oberflächenphysik
O 13: Postersitzung (Adsorption an Oberfl
ächen, Elektronische Struktur, Magnetismus in reduzierten Dimensionen, Epitaxie und Wachstum, Halbleiteroberfl
ächen und -grenzfl
ächen, Organische Dünnschichten)
O 13.61: Poster
Montag, 11. März 2002, 18:00–21:00, Bereich C
Surface phonons and adsorbate vibrations on silicon surfaces — •M. Eremtchenko1, D. Bauer1, F. S. Tautz2, and J. A. Schaefer1 — 1Institut für Physik, Technische Universität Ilmenau, PF 100565, 98684 Ilmenau — 2School of Engineering and Science, International University Bremen, PF 750561, 28725 Bremen
We have investigated clean and hydrogen-covered Si(100) and Si(110) surfaces by high resolution electron energy loss spectroscopy (HREELS), both in specular and off-specular scattering geometries. For the clean Si(100)2x1 surface, we observe a set of surface phonons, including a structure near 8 meV which we assign to the Rayleigh wave, in good agreement with a range of ab-initio calculations. At 25 meV and 60 meV two dimer-related phonons can be identified. Utilising selection rules both for dipole and impact scattering, we determine mode polarizations experimentally. On the hydrogen covered surfaces, we use the same technique to distinguish symmetric and antisymmetric vibrations, thereby unambigously assigning all observed features to predicted stretching, bending, wagging, and rocking modes. Finally, the issue of the dispersion of Si-H stretching and bending modes at the Si(110) surface is discussed.