Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 59: Metal Substrates I

O 59.11: Vortrag

Mittwoch, 2. April 2014, 18:30–18:45, WIL A317

Role of stacking, bonding and interaction with substrate in formation of bilayer silicene — •Paul Pflugradt, Lars Matthes, and Friedhelm Bechstedt — Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität and European Theoretical Spectroscopy Facility (ETSF), Max-Wien-Platz 1, 07743 Jena, Germany

The properties of the two-dimensional systems of group-IV materials are of increasing interest. Unlike graphene, the corresponding silicon-based honeycomb crystal, silicene, is claimed to be experimentally realized as monolayer on silver substrate. However, such conclusions are controversially debated in literature, because of the strong adsorbate-substrate interaction. Very recently promising bilayer silicene has been prepared, whose geometry and properties are widely unknown.

We predict an atomic geometry for this bilayer system, in contrast to the suggestions of experimentalists. Based on ab-initio density functional theory including van der Waals interaction, we make a comprehensive analysis of this new structure. We find a suprising silicene configuration, not stable as monolayer. The translational symmetry, the resulting lattice spacing, and the height of the topmost monolayer are in agreement with the STM findings. The band structure of the complete adsorbate system but also of the peeled-off silicene do not show conical linear bands near the Fermi level, as expected for freestanding 2D crystal.