Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 40: Methods: Scanning probe techniques I
O 40.2: Vortrag
Mittwoch, 25. März 2009, 15:15–15:30, SCH A316
Investigation of isolated single molecules on an insulating substrate — •Knud Lämmle1, Alexander Schwarz1, Marc Prosenc2, and Roland Wiesendanger1 — 1Universität Hamburg - Institut für Angewandte Physik, Jungiusstrasse 11a, 20355 Hamburg — 2Universität Hamburg - Department Chemie, Martin-Luther-King Platz 6, 20146 Hamburg
To tailor new molecular based devices, it is important to understand the characteristic features of their building blocks, i.e., the properties of individual molecules. Here, we utilized non-contact atomic force microscopy (NC-AFM) to study isolated Co-Salen molecules on NaCl(001). On this large band-gap insulator hybridization effects, which strongly alter the properties of molecules if adsorbed on metallic surfaces, are eliminated.
Immobilization of the rather small molecule is achieved by evaporating them in situ onto a 20 K cold substrate and by performing subsequent measurements at 8.2 K. NC-AFM images acquired on wide terraces reveal randomly distributed isolated banana-shaped objects with long and short axis of about 1.5 and 0.6 nm, respectively. By comparison with the known structure of the molecule, they can be identified as individual molecules adsorbed in a planar configuration. Surprisingly, the bananas appear asymmetric, i.e., the 60 pm high maximum is considerably shifted away from the center. Details of the orientation with respect to the underlying substrate as well as the exact adsorption site will be discussed by evaluating images, were isolated molecules and atomic resolution on the substrate are visible simultaneously.