Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 24: Postersitzung (Epitaxie und Wachstum, Oxide und Isolatoren, Elektronische Struktur, Oberfl
ächenreaktionen, Adsorption an Oberfl
ächen, Organische Dünnschichten)

O 24.21: Poster

Mittwoch, 26. März 2003, 14:30–17:30, P1

Relaxation and Debye temperature of the (111) surface of CaF₂ revealed by low energy electron diffraction (LEED) — •Jörn Henning, Jochen Vogt, and Helmut Weiss — Chemisches Institut der Universität Magdeburg, Abteilung Physikalische Chemie, Universtitätsplatz 2, 39106 Magdeburg

Up to now, informations regarding the surface relaxation of the CaF₂(111) cleavage plane were experimentally obtained only indirectly by the measurement of the surface dynamics of this technically relevant insulating material [1]. A well-suited technique for the determination of surface structures is LEED, which, however, is difficult to apply to insulators. By using a channelplate LEED optics it is possible to minimize charging problems due to the electron irradiation. Using this instrument on cleaved CaF₂(111) single crystal planes, we were able to obtain sharp diffraction patterns over a broad temperature and electron energy range. The experimentally revealed surface Debye temperature was consequently used in the I(V) analysis of the diffraction spot intensities, which yields no rumpling and a very small inward relaxation of the topmost layer. The result of this analysis is in very good agreement with calculations based on shell models [2].

[1] A. Lehmann et al., Surf. Sci. 331-333 (1995) 1430

[2] A. Jockisch et al., J. Phys.: Condens. Matter 5 (1993) 5401