Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 38: Adsorption V
O 38.8: Vortrag
Donnerstag, 30. März 2006, 16:45–17:00, TRE Phys
Robust hydrogen bonding plus molecular backbone flexibility: step-crossing allowed! — •Joachim Schnadt1,2, Eva Rauls1, Wei Xu1, Jan Knudsen1, Ronnie T. Vang1, Bjørk Hammer1, and Flemming Besenbacher1 — 1Interdisciplinary Nanoscience Center and Department of Physics, University of Aarhus, Building 1520, Ny Munkegade, 8000 Aarhus C, Denmark — 2Department of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund, Sweden
On perfect single crystal surfaces small organic molecules can self-assemble to form extended one- or two-dimensional networks using hydrogen bonding as the network-determining interaction. Real surfaces, however, are defect-afflicted and often it will be desirable that the self-assembled structures are tolerant with respect to the defects, a subject which has not been explored in detail to-date.
We have studied the self-assembly of 2,6-naphtalene-dicarboxylic acid (NDCA) on a Ag(110) surface by STM and XPS. We find that NDCA forms macroscopic-scale one-dimensional hydrogen-bonded structures up to the µm range. These structures extend over the step edges, which can be regarded as surface defects. We have used DFT to investigate the detailed structure of the assembly on both the terraces and at the step edges. The results show that NDCA indeed can form hydrogen bonds across the step edges, with the assembly having similar binding energies and geometries on the terraces and at the step edges. This behaviour can be traced back to an appropriate balance of the different interactions as well as a combination of molecular backbone flexibility and directionality of the hydrogen bonds.