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O: Fachverband Oberflächenphysik

O 14: Poster Session I: Nanostructures at surfaces I

O 14.2: Poster

Montag, 1. März 2021, 10:30–12:30, P

Thermally vs. Light-Induced On-Surface Polymerization — •Christophe Nacci and Leonhard Grill — Department of Physical Chemistry, University of Graz, Austria

Covalent on-surface polymerization via Ullmann coupling is one of the preferred chemical reactions to produce novel, and potentially functional, structures in the two-dimensional confinement of a surface. The dissociation of specific substituents and the formation of new covalent bonds can be induced by using different external stimuli, for instance heat, light and inelastic electron scattering. While plenty of examples exist on the thermal control of the reaction, only very few studies have reported a photochemical approach to form polymers at single-crystal surfaces. We compare the reaction pathways of individual molecular species to one-dimensional polymers by driving the reaction of the same precursor on Au(111) either by heat or by illumination with UV light. The results obtained by low-temperature scanning tunneling microscopy under ultrahigh vacuum conditions show that both stimuli are successful to induce the desired reaction on the surface. However, very different polymer length distributions are found, which will be discussed in view of the experimental conditions. Interestingly, under UV illumination the molecular coverage changes across the surface as it increases at the position of laser spot on the sample.