Hamburg 2001 – scientific programme

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O: Oberflächenphysik

O 9: Organische Dünnschichten und Festkörper

O 9.8: Talk

Monday, March 26, 2001, 18:00–18:15, B

Adsorption of chiral aromatic hydrocarbon on metal surfaces — •Karl-Heinz Ernst, Roman Fasel, and Yvette Kuster — EMPA, Ueberlandstr. 129, CH-8600 Duebendorf, Schweiz

We studied the interaction of heptahelicene ([7]H), a helically shaped, polyaromatic phenanthrene derivative, with well-defined single-crystal metal surfaces under ultra high vacuum (UHV) conditions. The molecules, racemate as well as the pure enantiomers, were deposited via molecular beam technique and subsequently characterized with surface sensitive techniques like temperature programmed desorption (TPD), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), time-of flight secondary mass spectrometry (ToF-SIMS), X-ray absorption spectroscopy (NEXAFS), and X-ray photoelectron diffraction (XPD). Adsorption of racemic [7]H on Cu(111) leads to self-alignment in domaines on the surface, which are mirror images of each other. After exposure to the pure enantiomers no domaines are observed. This is explained by a lateral self-separation of the enantiomers on the surface. On the stepped Cu(332) surface, an azimuthal alignment of the molecular spirals is observed. Models for the monolayer structure and the local adsorption geometry will be discussed.