Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 41: Inorganic/Organic Interfaces
O 41.43: Poster
Tuesday, March 17, 2015, 18:15–21:00, Poster B
Forced assembly of functional molecules — •Knud Seufert1,2, Felix Bischoff1, Yuanqin He1, Auwärter Willi1, Johannes V. Barth1, and Leonhard Grill2 — 1Physik-Department, Technische Universität München, Deutschland — 2Institut für Chemie, Karl-Franzens-Universität Graz, Österreich
The self-assembly of molecules is essential en route to ordered and utile organic structures - a groundwork of molecular electronics. An archetype of such a functional building block is the porphyrin as it plays a key role in several fundamental processes in nature.
Here we present a study on porphin molecules, the parent compound of all porphyrins, adsorbed on smooth noble metal single crystals. A partial filling of the lowest unoccupied molecular orbital (LUMO) results in a charge redistribution at the porphin/Ag(111) interface and a dominating repulsive intermolecular interaction [1]. This repulsion can be overcome by coadsorption or a modification of the substrate. In the first case well-ordered mixed layers can be produced where small gas molecules between the porphines stabilize a self-assembly process via dipole-dipole interaction [2]. A reduced interaction to the metal surface can be achieved by adding a thin insulating interlayer or a complete exchange of the support resulting in the lack of charge transfer. This leads to a suppression of the main repulsive intermolecular force and the formation of islands.
[1] Bischoff et al., ACS Nano (2013) 3139-3149
[2] Buchner et al., ACS Nano (2009) 1789-1794