Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 58: Poster Session III (Solid/liquid interfaces; Metals; Semiconductors; Oxides and insulators)

O 58.57: Poster

Wednesday, March 28, 2012, 18:15–21:45, Poster B

LEED and PIRS study of SF₆ physisorption on NaCl(100) — •Mirko Langer, Stephan Härtel, Jochen Vogt, and Helmut Weiss — Chemisches Institut der Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany

The interaction of the antropogenic greenhouse gas SF₆ with the NaCl(100) surface was investigated using low-energy electron diffraction (LEED) and polarization infrared spectroscopy (PIRS) under ultrahigh vacuum conditions and cryogenic temperatures. Consistent with the results of a previous study of SF₆ adsorption on NaCl thin films [1], SF₆ exhibits a complicated Stranski-Krastanov film growth behavior on NaCl(100): pronounced 3D nano crystal formation occurs at a substrate temperature of 64 K, indicated by strong absorptions in the region of the asymmetric S-F stretch mode. The observed characteristic Davydov splitting of about 100 cm⁻¹ is consistent with the large vibrational polarizability of SF₆ and its bcc bulk structure. In contrast to many other physisorption systems, a 2D adsorbate of SF₆ is formed only at lower temperatures below 45 K, indicated by the appearance of superstructure spots in the LEED patterns. The unusual growth behavior is attributed to the strong lattice mismatch between adsorbate and substrate.
A. Klekamp, E. Umbach, Surf. Sci. Lett. 284 (1993), 291