Talk given by Dr. Uta Schlickum Max Planck Institute for Solid State Research Stuttgart, Germany Abstract: Numerous properties of organic molecules are highly sensitive to the precise conformation and local environment of the system. Gaining control on the structure at the sub-molecular level therefore provides atomically precise tuning knobs to tailor molecular properties. An ideal tool to study such phenomena is scanning tunneling microscopy (STM) since it allows characterizing and manipulating the structural, electronic and mechanical properties of a single entity on surfaces with highest spatial resolution. In this talk I will focus on two examples illustrating the potential of such studies, individual molecular switches and chemical reactions in an organic subunit. In the first example we demonstrate a perfect bipolar switch exploiting a bistability of molecular conformations stabilized by different charge transfers between molecule and metal substrate. Single molecular switches can be addressed individually but also entire ensembles can be switched by a single STM induced stimulus. In the latter case hot charge carrier injection into a surface state and the long mean free path of this specific state allows switching for distances of the order of 100 nm. In a second example we study a desulfurization process of one thiophene unit embedded in a molecular back bone on a Cu(111) surface. The chemical reaction is triggered by the electric field confined between sample and tip apex. The precise control of the external stimulus allows determining two elementary reactions taking place before the end-product is reached that can be attributed to the breaking of two C-S bonds. The opened C-bonds react with the Cu surface atoms resulting in a strong anchoring that among others leads to an increase of the maximum conductance through a single molecule by 50%. At the end I will give a brief outlook providing future perspectives in the field of structural analysis, control and manipulation of “macromolecules” of more biologic relevant systems like peptides.

This event is part of the eventgroup INT Talks

Homepage
https://www.int.kit.edu/events.php

Speaker
Dr. Uta Schlickum

Max Planck Institute for Solid State Research
http://www.fkf.mpg.de/employees/31645/5017348

Organizer
Prof. Wulf Wulfhekel
Institut für Nanotechnologie
KIT
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen
Mail: wulf wulfhekel ∂does-not-exist.kit edu
https://www.phi.kit.edu/english/wulfhekel.php

Targetgroup
Interested / Everyone