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CPP 102.3: Vortrag
Donnerstag, 19. März 2020, 15:30–15:45, WIL B321
One-dimensional molecular chains of Quinacridone on Ag(100) and Cu(111): STM- and SPA-LEED-investigations — •Niklas Humberg1, Rémi Bretel2, Alexander Eslam1, and Moritz Sokolowski1 — 1Institut für Physikalische und Theoretische Chemie der Universität Bonn, Germany — 2University of Paris-Saclay, Institut des Sciences Moléculaires D’Orsay, France
One-dimensional molecular aggregates are of high interest because they often show specific and pronounced coupling effects for electronic excitations, e.g. in optical spectra. Here, we report a structural analysis of two such systems, quinacridone (QA) on Ag(100) and Cu(111), by STM and SPA-LEED.
On Ag(100) QA grows in homochiral domains of parallel one-dimensional chains at room temperature (RT), forming a metastable structure. Within these chains the molecules are parallel and linked pairwise via two hydrogen bonds. The distance between chains varies with coverage. After annealing at 500 K, a 2D commensurate heterochiral structure is formed. It consists of homochiral dimers forming periodically indented and closely packed chains. On Cu(111), QA grows in similar fashion at RT, but compared to QA/Ag(100) the structure shows stronger disorder in form of kink-like defects in the chains. Annealing at different temperatures between RT and 600 K leads to different chain-like structures, that are stable at RT. The comparison to the similar system QA/Ag(111)  indicates that the structures of QA/Cu(111) at RT are determined by kinetic limitations.
 Wagner et al, J. Phys. Chem. C 2014, 118, 20, 10911-10920.