Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 8: Metal Substrates: Adsorption of Organic/Bio Molecules I

O 8.4: Vortrag

Montag, 25. Februar 2008, 12:45–13:00, MA 041

Tuning the interaction at an organo-metallic interface: PTCDA on epitaxial Ag on Au(111) — •Johannes Ziroff, Frank Forster, and Friedrich Reinert — Universität Würzburg, Experimentelle Physik II , 97074 Würzburg

PTCDA (3,4,9,10-perylene-tetracarboxylic acid dianhydrid) monolayers on Au(111) and Ag(111) are widely used model systems in the field of organo-metallic interfaces, featuring the basic adsorbtion types of physisorption and chemisorption respectively. By the growth of epitaxial layers of Ag on Au(111), the electronic states of the substrate can be modified (depending on the thickness of the Ag film) to become more and more "silver-like", up to the point where they resemble the (111) surface of bulk silver. This process includes the formation of quantum well states with well charcterised charge distribution and electronic properties. Therefore, this system enables experiments in which we control the substrates physical properties in small discrete steps, meanwhile tuning the molecular bonding from van der Waals to covalent.

We will show angle-resolved photoemission spectra of PTCDA monolayers on Ag films of various thicknesses on Au(111), focusing on the valence band and its electronic features, namely the Shockley surface state, higher molecular orbitals (HOMO, HOMO-1) and the so-called former LUMO. We will comment on correlations between the substrates distinctive electronic features and the appropriate interface structure, thus fathoming their role in the bonding mechanism and the formation of new valence electronic states.