Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 12: Morphology Prediction at Interfaces
O 12.1: Vortrag
Montag, 7. März 2016, 15:00–15:15, S051
Flexible 2D crystals of polycyclic aromatics stabilized by static distortion waves — Matthias Meissner1, Falko Sojka1, Lars Matthes2, Friedhelm Bechstedt2, Xinliang Feng3, Klaus Müllen3, Stefan C. B. Mannsfeld4, •Roman Forker1, and Torsten Fritz1 — 1Institute of Solid State Physics, Friedrich Schiller University Jena, Germany — 2Institute of Condensed Matter Theory and Solid State Optics, Friedrich Schiller University Jena, Germany — 3Max Planck Institute for Polymer Research, Mainz, Germany — 4Center for Advancing Electronics, TU Dresden, Germany
The epitaxy of many organic films on inorganic substrates can be classified by established lattice match conditions. Yet, there are material-substrate combinations for which this classification fails and cannot be exploited to understand reproducible azimuthal alignments between adsorbate and substrate lattices. For decades it has been hypothesized in the literature that so-called static distortion waves (SDWs) could be responsible for the observed orientational epitaxy in such cases. By means of STM and LEED experiments we demonstrate unequivocally SDWs in films of hexa-peri-hexabenzocoronene on graphite, which manifest as sub-Ångström local molecular displacements from an ideal rigid adsorbate lattice, being itself incommensurate with graphite in contrast to previous reports. We present a model that consistently explains these displacements in both size and direction. Based on DFT we calculate for realistically large domains the energy gain due to the SDWs, thereby proving their crucial role for the observed epitaxy, and we successfully reproduce the measured domain angle.