Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 69: Nanostructures at surfaces: 1D and 2D structures and networks II
O 69.6: Talk
Wednesday, March 14, 2018, 16:15–16:30, MA 141
Light assisted charge spreading and charge trapping in organic semiconductors needles supported by 2D materials — •Aleksandar Matković1, Markus Kratzer1, Jakob Genser1, Daniel Lüftner2, Peter Puschnig2, Zhongrui Chen3, Olivier Siri3, Conrad Becker3, and Christian Teichert1 — 1Institute of Physics, Montanuniversität Leoben, Franz Josef Strasse 18, 8700 Leoben Austria — 2Institute of Physics, University of Graz, NAWI-Graz, Universitätsplatz 5. 8010 Graz, Austria — 3Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
In this study we investigate the growth of an oligoacene derivate dihydrotetraazaheptacene (DHTA7), which - due to nitrogen containing groups - forms solids through H-bonding and dipolar interactions between neighboring molecules. As a result of H-bonding networks, the molecules form in-plane rows with subsequent layers exhibiting π-π stacking. Crystalline needles of DHTA7 were grown by hot wall epitaxy on the surfaces of graphene and hexagonal boron nitride, which act as van der Waals electrodes and gate dielectrics. Using photo-assisted electrostatic force microscopy we demonstrate charge trapping and light-assisted charge spreading within the networks of DHTA7 needles. We found that in the dark these needles are not conductive, while visible light linearly polarized parallel to the long axis of the needles allows spreading of the charges across the network for tens of micrometers. Results indicate that - due to the inverse population created by the laser - charges that were trapped in the localized defects can spread through the bands of the organic semiconductor.