Abstract by: Aldo Ugolotti

Strong Adsorption at Metal-Organic Interface: the Case of Pentacene on Pt(111)

The functionalization of a metallic surface with an organic overlayer is an important method of tuning its physical and chemical properties and it is of paramount importance either for optoelectronic devices and catalysis. The properties of such an interface are strongly dependent on the characteristics of the metal, the molecule and their mutual interaction and the strength of the absorption is one of the key parameters. In particular two regimes are usually distinguished, namely physisorption and chemisorption, as opposite extremes yielding some distinct features.

Here we investigate the adsorption of pentacene on the (111) surface of platinum, which is an archetypal system for a junction with a low charge-injection barrier, by either experimental and theoretical methods. We probe the structural and electronic configurations of pentacene by scanning tunnelling microscopy (STM), X-ray photoemission spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy measurements. We simulate the interface by means of ab initio methods based on the density functional theory (DFT) framework, while including the dispersion forces.

We derive the absorption site and geometry of the molecule, briefly an almost flat configuration, aligned with the substrate's <110> directions. We also show that such result is accompanied by a set of features in the electronic properties which point out a strong interaction regime at the interface, that can be defined as chemisorption.

Work in collaboration with: S.S. Harivyasi, A. Baby, M. Dominguez, A.L. Pinardi, M.F. López, J.A. Martín-Gago, G. Fratesi, L. Floreano and G.P. Brivio