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O: Oberflächenphysik

O 12: Struktur und Dynamik reiner Oberfl
ächen

O 12.5: Vortrag

Montag, 11. März 2002, 16:15–16:30, H45

Surface Phonon Dispersion of the 10-fold d-AlNiCo Surface — •H. R. Sharma¹, K. J. Franke¹, W. Theis¹, P. Gille², and K. H. Rieder¹ — ¹Fachbereich Physik der Freien Universität Berlin — ²Ludwig-Maximilians-Universität München

Surface phonons of the 10-fold surface of decagonal-Al_71.8 Ni_14.8Co_13.4 were investigated by inelastic He-atom scattering. In experiments with cooled and heated samples and He-atom kinetic energy ranging from 8 to 35meV the (acoustic) Rayleigh mode was observed. In d-AlNiCo surface, the measured velocity of sound of the surface wave is isotropic and in good agreement with prediction based on experimental elastic constants [1]. As the diffraction from the 10-fold surface is dominated by the specular beam, a relatively unambiguous assignment of momentum transfer to the phonon gains and losses observed in the time-of-flight spectra is possible. Strong single phonon signatures are limited to wave vectors q<0.5Å⁻¹ and the phonon line widths are resolution limited up to q ≈ 0.25Å⁻¹, beyond which they increases rapidly, similar to the behaviour recently observed in the corresponding bulk phonons [2].

[1] M. A. Chernikov et al., PRL 80, 321(1998)

[2] F. Dugain et al., Eur. Phys. J. B. 7, 513 (1999)