Authors Bittrich, E. ; Domke, J. ; Jehnichen, D. ; Bittrich, L. ; Malanin, M. ; Janke, A. ; Uhlmann, P. ; Eichhorn, K.-J. ; Papamichail, A. ; Stanishev, V. ; Darakchieva, V. ; Al-Hussein, M. ; Levichkova, M. ; Fritz, T. ; Walzer, K.
Title Morphology of thin films of aromatic ellagic acid and its hydrogen bonding interactions
Date 17.07.2020
Number 58443
Abstract Ellagic acid (EA), an antioxidant from fruits or other plants, has recently evoked interest in the field of organic electronics because of its weak electron donor properties. In this work, the preparation of uniaxial p-stacked EA films by thermal evaporation on different surfaces is reported for the first time. The (102) lattice plane of the p-electron system was confirmed as the contact plane for one monolayer equivalent on Ag(111) by low-electron energy diffraction. X-ray and atomic force microscopy measurements revealed nanocrystalline grains with an average in-plane size of 50 nm and considerably smaller average out-of-plane crystallite sizes (16–25 nm) in films of 16–75 nm thickness. The influence of different substrates was minor compared to the effect of the film thickness. An increase in the in-plane density of grains at larger film thicknesses was deduced from the trend in their uniaxial optical properties. Weak and strong intermolecular H-bonding interactions were identified in the EA crystal lattice, while a surplus of weak H-bonding was observed for the nanocrystallites in thin films, as compared to bulk EA. Finally, EA was coevaporated with the semiconducting thiophene molecule DCV4T-Et2 to demonstrate principle interactions with a guest molecule by H-bonding analysis. Our results illustrate the feasibility of applying EA films as alignment layers for templating other semiconducting organic films used in organic electronic devices.
Publisher Journal of Physical Chemistry C
Citation Journal of Physical Chemistry C 124 (2020) 16381-16390

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