Authors: T. Soubiron, F. Vaurette, B. Grandidier, X. Wallart, J.P. Nys and D. Stiévenard
Affilation: IEMN (UMR8520, CNRS), Dpt ISEN, France
Pages: 383 - 386
Keywords: molecules, silicon, surface, STM, XPS
Submonolayer coverages of perylene-tetracarboxylic-dianhydride (PTCDA) molecules have been investigated with scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). At high coverage, X-ray measurements indicate that only a fraction of the molecules are chemisorbed and that the bonding occurs through the dicarbonyl functional groups, preserving the _-conjugation of the molecules. At lower coverage, comparison between the STM images and calculations of the electronic structure of the molecule show that the molecule adsorbs mostly in a planar configuration with its axis parallel to the Si dimers. Different configurations are observed and associated with physisorbed and chemisorbed states of the adsorbates. Finally, we have studied low coverage of PTCDA on passivated silicon surfaces : on hydrogenated silicon (100) surface, PTCDA molecules are physisorbed and are mobile on the surface. At room temperature, self-assembled 2D clusters are observed.