Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 45: Organic-Inorganic Hybrid Systems and Organic Films

O 45.3: Poster

Tuesday, March 21, 2017, 18:30–20:30, P1A

Transition from fractional to integer charge transfer at the inorganic-organic interface via alloying — •Elisabeth Wruss, Egbert Zojer, and Oliver T. Hofmann — Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Austria

When investigating interfaces consisting of an organic layer on an inorganic substrate, two different types of charge transfer toward the adsorbate can arise. Either all molecules get fractionally charged or the charge localizes on individual molecules. While fractional charge transfer appears mostly in case of pristine metals, coexistence of charged and uncharged molecules occurs on more unreactive surfaces. In this work we address the transition between these two situations via DFT simulations. Starting with an acceptor molecule on a metallic substrate, we continuously decrease the density of states at the Fermi edge via alloying of the substrate until an integer charge transfer situation is established. By investigating the system at different alloying concentrations we analyze the properties of this transition. As a model system we have chosen the acceptor molecule TCNE on copper, which can be converted into the semiconducting cupric oxide Cu2O. To adequately model the charge transfer within DFT, large unit cells containing a sufficient number of molecules and hybrid functionals are needed. Therefore these simulations are computationally very demanding. This is one of the main reasons why the possibility of integer charge transfer has often been neglected in computational studies, although its consideration can be of uttermost importance for the understanding of the electronic properties of many inorganic-organic interfaces.