Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 59: Oxides and Insulators: Clean Surfaces

O 59.8: Vortrag

Donnerstag, 29. März 2007, 17:30–17:45, H41

Tensor LEED study of the dynamics of the NaCl(100) surface — •Jochen Vogt — Chemisches Institut der Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg

A wealth of theoretical studies dealt with the dynamics of the NaCl(100) surface, e.g. in relation to its melting behaviour, friction, or the simulation of image contrast in atomic force microscopy. Accurate experimental information on the temperature dependent vibrational amplitudes of ions in different layers is missing so far, although it could serve as a critical test for the various potential models applied to this prototype material. This contribution reports LEED experiments at various temperatures between 25 K and 300 K, in which beam intensities were recorded as a function of electron energy. The experimental I(E) data were analyzed using the tensor LEED approach. At all investigated temperatures the NaCl(100) surface exhibits the same relaxation, characterized by a static inward shift of the topmost Na⁺ ion of 0.09±0.03Å. The dynamics of the topmost layer is significanlty higher than those of the second layer, where the measured amplitudes are close to literature bulk values. Above 100 K, Na⁺ and Cl⁻ ions in the topmost layer have nearly the same amplitudes, while the amplitudes of the cations in the second layer are larger than those of the anions. In this temperature range the mean square amplitudes of the ions at the surface are in good agreement with previously reported lattice dynamics studies.