N-Heterocyclic Olefins on a Silicon Surface |
| |
Authors: | Dr Mowpriya Das Dr Conor Hogan Robert Zielinski Milan Kubicki Dr Maximilian Koy Canan Kosbab Simone Brozzesi Ankita Das Mike Thomas Nehring Viktoria Balfanz Juls Brühne Prof Dr Mario Dähne Dr Martin Franz Prof Dr Norbert Esser Prof Dr Frank Glorius |
| |
Institution: | 1. Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149 Münster, Germany;2. Istituto di Struttura della Materia-CNR (ISM-CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy;3. Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstrasse 36, D-10623 Berlin, Germany;4. Dipartimento di Fisica, Università di Roma ‘Tor Vergata', Via della Ricerca Scientifica 1, 00133 Rome, Italy |
| |
Abstract: | The adsorption of N-heterocyclic olefins (NHOs) on silicon is investigated in a combined scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory study. We find that both of the studied NHOs bind covalently, with ylidic character, to the silicon adatoms of the substrate and exhibit good thermal stability. The adsorption geometry strongly depends on the N-substituents: for large N-substituents, an upright adsorption geometry is favored, while a flat-lying geometry is found for the NHO with smaller wingtips. These different geometries strongly influence the quality and properties of the obtained monolayers. The upright geometry leads to the formation of ordered monolayers, whereas the flat-lying NHOs yield a mostly disordered, but denser, monolayer. The obtained monolayers both show large work function reductions, as the higher density of the flat-lying monolayer is found to compensate for the smaller vertical dipole moments. Our findings offer new prospects in the design of tailor-made ligand structures in organic electronics and optoelectronics, catalysis, and material science. |
| |
Keywords: | Density functional calculations Monolayers N-heterocyclic olefins Scanning tunneling microscopy Silicon |
|
|