Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 46: Poster: Molecular Films - Photovoltaics, Electronics and Morphology
O 46.4: Poster
Dienstag, 13. März 2018, 18:15–20:30, Poster A
Growth morphologies of dipolar nitrogen based oligoacene derivatives on (0001) sapphire — •Aydan Çiçek1, Aleksandar Matković1, Markus Kratzer1, Zhongrui Chen2, Olivier Siri2, Conrad Becker2, and Christian Teichert1 — 1Institute of Physics, Montanuniversität Leoben, Franz Josef Strasse 18, 8700 Leoben Austria — 2Aix Marseille Universitè, CNRS, CINaM UMR 7325, 13288 Marseille, France
Oligoacenes (as pentacene) and their derivatives are promising candidates for applications in organic electronics, due to molecular packing that favours charge transport and thus high field-effect mobilities. This study explores growth morphologies of thin-films and sub-monolayers of dihydro-tetraaza-acenes on the surface of sapphire, a technologically relevant gate dielectric. In particular, dihydro-tetraaza-penatacene (DHTA5) and -heptacene (DHTA7) molecules are considered, both exhibit a similar dipolar momentum. The molecules are deposited using a hot wall epitaxy system. As substrate, vicinal (0001) sapphire is used with an average step distance of 50 nm, and step height of 0.2 nm. The morphology of the grown films is investigated ex-situ by atomic force microscopy. Coverages from sub-monolayers to several layers are analysed, and evolution of needle-like and island-like crystallites is examined as a function of the deposition temperature. Moreover, stability of the crystallites is investigated under prolonged exposure to ambient conditions. Our results show that ambient stability, π-π stacking, and layer-by-layer growth all favor DHTA7 for organic field effect transistor applications.