Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Poster Session II (Metals; Nanostructures at surfaces; Surface or interface magnetism; Spin-Orbit Interaction at Surfaces; Electron and spin dynamics; Surface dynamics; Methods; Theory and computation of electronic structure)

O 36.26: Poster

Dienstag, 15. März 2011, 18:30–22:00, P4

Monolayer formation and electronic structure of tetracyanoethylene on Ag(111) and Ag(100) studied by scanning tunneling microscopy — •Hasmik Harutyunyan, Tatjana Walth, Tobias Allmers, and Daniel Wegner — Physikalisches Institut and CeNTech, WWU Münster, Germany

Tetracyanoethylene [TCNE, (CN)₂C=C(CN)₂] is a very strong π-electron acceptor that easily forms metal-organic charge-transfer complexes. Particular interest exists for TCNE-based complexes involving transition-metal atoms because they are promising candidates for molecular magnets [1]. Recent studies showed that TCNE adsorbs quite differently on various noble metal surfaces due to a varying ratio of molecule-molecule vs. molecule-substrate interaction [2]. Here we present new results of the growth of TCNE on Ag(100) and Ag(111) studied by low-temperature STM and STS. We show that, different from previous results, TCNE can form closed-packed monolayer patterns on both surfaces. In case of Ag(100), we find local order in shifted rows that form zig-zag patterns with (3 × 5n) unit cells (n = 1 … 4). On Ag(111), TCNE forms an ordered porous network with a (√67 × √67)−R12.1^∘ unit cell containing six molecules. The arrangement of the molecules leads to chirality. STS reveals molecular orbitals as well as vibrations whose dependence on molecule-molecule and molecule-substrate interaction will be discussed.

[1] D. Wegner et al., PRL 103, 087205 (2009).

[2] D. Wegner et al., Nano Lett. 8, 131 (2008).