Dissertation / PhD Thesis

FZJ-2015-02741

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Interacting Interactions: A Study on the Interplay of Molecule-Molecule and Molecule-Substrate Interactions at Metal-Organic Interfaces

Willenbockel, M. (Corresponding Author)FZJ*

2014
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-018-0

Please use a persistent id in citations: http://hdl.handle.net/2128/8567

Abstract: In this work a surface science study on metal-organic interfaces is presented to resolve their geometric and electronic properties and study the interplay of molecule molecule and molecule-substrate interactions. The organic molecules benzene, azobenzene, 3,4,9,10-perylenetetracarboxylic acid dianhydride (PTCDA), and terephthalicacid (TPA) are deposited on low index Ag and Cu surfaces to form monolayer andsub-monolayer structures which are investigated by normal incidence X-ray standing waves and angle resolved photoemission spectroscopy, which leads to several surprising findings. Investigating the adsorption of benzene, we find it physisorbed in a flat geometry for benzene on Ag(111). Enhancing the molecule-substrate interaction by exchanging Ag(111) with the stronger interacting Cu(111) is expected to simply lower the adsorption height. However, we find flat molecules at an elevated adsorption height forbenzene/Cu(111), which seem to be stabilized via intermolecular interactions due to the coexistence with upright standing benzene molecules. The interplay of molecule-molecule and molecule-substrate interactions is further explored on a metal-organic network formed by codeposition of TPA and Fe atoms on Cu(100). The coordination of TPA molecules by the Fe atoms reduces the TPA substrate interaction. An additional sitespecific adsorption of oxygen again alters this balance. In case of PTCDA a comprehensive study for its adsorption on low index Ag surfacesis presented. From linking the geometric and electronic stucture properties, it is understood that the electron density spill-out of the surface and its uptake by the adsorbing molecule is a decisive molecule-substrate interaction channel. This explains the finding that the resulting binding energies of the lowest unoccupied molecular orbital (LUMO) as well as the adsorption height of PTCDA on Ag are determined by the work function. Moving to the archetypal molecular switch azobenzene, which is studied on Cu(111), three different azobenzene monolayer phases which are formed along with a coverage dependent dissociation of the molecule are revealed. The higher the density of molecules get, the stronger molecule-molecule interactions become and force the molecule to bend. However, its strong molecule-substrate bond prevents a conformational change and the resulting stress ultimately leads to a dissociation. The surprising results of this work show that the understanding of interactions at metal-organic interfaces is still only rudimentary and stress the importance of further fundamental research.

Keyword(s): Dissertation

Note: RWTH Aachen, Diss., 2014

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Contributing Institute(s):

1. Funktionale Nanostrukturen an Oberflächen (PGI-3)
2. Zentralinstitut für Elektronik (ZEA-2)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

Appears in the scientific report 2015

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Database coverage:

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