Dresden 2011 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 62: Organic Thin Films I
DS 62.4: Vortrag
Freitag, 18. März 2011, 11:00–11:15, GER 38
Structure solution of organic surface-induced polymorphs by x-ray diffraction reciprocal-space mapping — •Ingo Salzmann1, Dmitrii Nabok2, Martin Oehzelt3, Steffen Duhm4, Armin Moser5, Georg Heimel1, Peter Puschnig2, Claudia Ambrosch-Draxl2, Jürgen P. Rabe1, and Norbert Koch1 — 1Humboldt-Universität zu Berlin, Germany — 2Montanuniversity Leoben, Austria — 3Johannes Kepler Universität Linz, Austria — 4Chiba University, Japan — 5Graz University of Technology, Austria
Thin films of pentacenequinone (PQ) and perfluoropentacene (PFP) on silicon oxide (SiOx) and highly oriented pyrolytic graphite (HOPG) were investigated by x-ray diffraction reciprocal space mapping (RSM) providing the unit cell parameters of the respective substrate induced polymorphs (SIPs). In contrast to the monoclinic single-crystal phases (SCPs), RSM yields triclinic unit-cells for PQ and PFP on HOPG and for PQ on SiOx, the latter with only one molecule per unit cell. Therefore, in contrast to its SCP, PQ does not exhibit a molecular herringbone arrangement in the SIP. It is shown that the same PFP SIP as found on HOPG grows on Au(111), Ag(111) and Cu(111), therefore demonstrating that, owing to the fiber texture of HOPG, growth investigations on HOPG can act as technique for SIP determination on metallic single crystalline substrates, where RSM cannot be applied. For both SIPs on SiOx full structure solutions are derived via force-field calculations and used for comparative electronic structure calculations of the two PQ polymorphs demonstrating significantly wider dispersion of the lowest unoccupied molecular orbital-derived band.