Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Poster Session II (Organic films and electronics, photoorganics; Nanostructures; Plasmonics and nanooptics, Surface chemical reactions and heterogeneous catalysis, Surface dynamics )

O 36.61: Poster

Dienstag, 12. März 2013, 18:15–21:45, Poster B2

PTCDA adsorption on KCl and NaCl(100) surfaces studied from first principles — •Hazem Aldahhak, Wolf Gero Schmidt, and Eva Rauls — Theoretische Physik, Universität Paderborn

In recent years, various highly regular supramolecular architectures of self-organized molecules on crystals have been designed and used in the bottom-up device technology.

In the past, metal surfaces have frequently been used as substrate. However, metal substrates induce screening and quenching effects and thus hamper the detailed spectroscopy of the adsorbed overlayer. In contrast, molecular adsorption on ionic crystals like sodium or potassium chloride opens the possibility to study electronically decoupled molecules.

Here we present density-functional theory calculations on the adsorption of PTCDA on KCl and NaCl (100) surfaces. Thereby the adsorption on flat surfaces as well as stepped substrates steps is investigated. Experimentally, both flat-lying (P-type) as well as standing molecules (S-type) are observed depending on the preparation conditions. In order to understand and rationalize the adsorption mechanisms leading to the formation of these structures, a large variety of interface geometries was studied and analyzed with respect to the contribution of ionic, covalent and van-der-Waals interactions between adsorbates and substrates. The influence of the substrate and bonding mechanism on the molecular electronic structure is investigated in detail and compared with the experimental data available.