Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 28: Organic-Inorganic Systems I: PTCDA

O 28.3: Talk

Tuesday, March 8, 2016, 11:15–11:30, S054

Surface crystallography by LEED-IV of large organic adsorbates on Ag — •Ina Krieger^1,3, Georg Held², Christian Kumpf³, and Moritz Sokolowski¹ — ¹Institut für Physikalische und Theoretische Chemie, Universität Bonn, 53115 Bonn, Germany — ²Department of Chemistry, University of Reading and Diamond Light Source, UK — ³Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52428 Jülich, Germany

LEED-IV is a powerful technique for surface crystallography which supplies detailed experimental structure information on the adsorption geometry of large organic molecules on surfaces revealing important insights in inter-atomic interactions and chemical bonding. Using data from different angles of incidence and optimizing the program code we were able to overcome the challenges given by the limitations of the experimental data set and the calculation times required for the complex and large unit cells.

Here we will report on a recent LEED-IV analysis of PTCDA on Ag(100), at present yielding a good Pendry R-factor of about 0.23. The calculation is based on a unit cell containing 156 atoms and experimental curves for five angles of incidence with an energy-to-parameter ratio over 200 eV. We were able to derive structural information about the surface geometry, in particular with regards to vertical distortions of the molecule core and the buckling of the substrate surface, which could so far not be obtained by other structure methods and are in good agreement with results from DFT and NIXSW studies. Supported by the DFG.