Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 21: Quasicrystals

MM 21.1: Vortrag

Dienstag, 26. Februar 2008, 11:45–12:00, H 0111

The (010) Surface of the T-Al3(Mn,Pd) Complex Metallic Alloy — •Thalia Deniozou¹, Rafik Addou¹, Marc Heggen², Michael Feuerbacher², Oliver Gröning³, Vincent Fournée¹, Julian Ledieu¹, and Jean-Marie Dubois¹ — ¹1LSG2M, UMR 7584 CNRS-INPL Ecole des Mines, F-54042 Nancy, France — ²Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany — ³3EMPA, Materials Science and Technology, Nanotech at Surfaces, Feuerwerkerstraße 39, CH-3602 Thun, Schweiz

The discovery of quasicrystals modified the basic concept of solid state physics, as they lack periodicity but still have long-range order and forbidden rotational symmetries. There is currently a broad interest in related systems, called complex metallic alloys, presenting a similar local order but recovering periodicity, though on a large scale compared to regular crystals. The orthorhombic phase T-Al3(Mn,Pd) is an example of such large unit cell crystal, approximant of the decagonal Al-Mn-Pd quasicrystal. Here we report the first study of the (010) surface of the T-Al3(Mn,Pd) phase, using scanning tunnelling microscopy (STM) and low energy electron diffraction (LEED). The surface is prepared by sputtering and annealing to 900 K. The characteristic pseudo-decagonal symmetry and the orthorhombic unit mesh of the (010) T-Al3(Mn,Pd) surface could be observed with LEED. STM images reveal flat terraces separated by a unique step height (6.3 +0.3 Å). High-resolution images show a pattern of pentagonal chains characteristic of the bulk structure. We found that the contrast in STM images strongly depends on the bias voltage.