Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 51: Organic-Inorganic Systems II: Energy Level Alignment
O 51.9: Vortrag
Mittwoch, 9. März 2016, 12:45–13:00, S054
Work function tuning and electrostatic effects: embedded dipoles in aromatic self-assembled monolayers — Swen Schuster1, Tarek Abu-Husein2, David A. Egger3, Iris Hehn3, Martin Kind2, Egbert Zojer3, Andreas Terfort2, and •Michael Zharnikov1 — 1Angewandte Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg, Germany — 2Institut für Anorganische und Analytische Chemie, Universität Frankfurt, 60438 Frankfurt, Germany — 3Institute of Solid State Physics, NAWI Graz, Graz University of Technology, 8010 Graz, Austria
Self-assembled monolayers (SAMs) are frequently used as intermediate films to modify charge-carrier injection from metal-electrodes into an organic semiconductor. This is usually achieved by use of the terminal dipolar groups comprising the SAM-ambient interface, affecting, however, the growth chemistry of the semiconductor. Here we suggest an alternative approach, viz. embedding dipolar element into the molecular backbone, decoupling the dipole control and the chemistry at the SAM-ambience interface. In this context, using a representative model system, we studied electronic and structural properties of aromatic SAMs that contain an embedded, dipolar group, viz. pyrimidine. Using a number of complementary characterization techniques combined with quantum-mechanical modeling, we show that such mid-chain substituted monolayers are highly interesting from both fundamental and application viewpoints, as the dipolar groups induce a potential discontinuity inside the monolayer, electrostatically shifting the energy levels in the regions above and below the dipoles relative to one another.