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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 53: Inorganic/organic interfaces: Electronic properties II (joint session O, CPP)
CPP 53.6: Vortrag
Mittwoch, 18. März 2015, 16:30–16:45, HE 101
Integer versus fractional charge transfer at metal/organic and metal/insulator/organic interfaces: Cu(/NaCl)/TCNE — •Oliver T. Hofmann1,2, Patrick Rinke1,3, Viktor Atalla1, Georg Heimel4, and Matthias Scheffler1 — 1FHI Berlin, Germany — 2TU Graz, Austria — 3Aalto University, Helsinki, Finland — 4Humboldt University Berlin, Germany
We use semilocal and hybrid density functional theory to study the charge transfer and level alignment at a representative interface between a metal and an organic molecule. To reduce the hybridization strength between the adsorbate and the substrate, we also insert thin insulating NaCl buffer layers. We find that upon direct adsorption on the metal, charge is perfectly delocalized across all molecules, leading to a laterally homogenous layer. However, when the hybridization between metal and organic is prevented by an insulating interlayer, charge localizes on individual moieties, creating laterally inhomogenous charge distributions. This spontaneous breaking of the translation symmetry is reflected in several observables, such as the molecular geometry or the valence and core densities of states. We find that the amount of charge transfer is determined, to a significant extend, by the ratio of the lateral spacing of the molecules and their energetic distance to the electron reservoir, i.e., the metal. Therefore, the amount of charge transfer does not only depend on the electronic structure of the individual components, but also on the interface geometry. Furthermore, we discuss the impact of the lateral charge distribution on the coverage dependence of the work function for different growth models.