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O: Fachverband Oberflächenphysik

O 60: Organic Molecules on Inorganic Substrates IV: Electronic Properties, Excitations, Dynamics

O 60.8: Vortrag

Mittwoch, 3. April 2019, 16:45–17:00, H24

Molecular dynamics simulation of transport and nucleation of conjugated organic molecules on inorganic surfaces — •Mila Miletic^1,3, Karol Palczynski¹, Matheus R. Jacobs³, Ana M. Valencia³, Caterina Cocchi³, and Joachim Dzubiella^1,2 — ¹Helmholtz-Zentrum Berlin, Berlin, Germany — ²Physikalisches Institut, Albert-Ludwigs-Universität, Freiburg, Germany — ³Physics Department, Humboldt-Universität zu Berlin, Berlin, Germany

We analyze the influence of polarity on the surface transport of single conjugated organic molecules on the inorganic (1010) zinc oxide surface by all-atom molecular dynamics simulations at room temperature and above. In particular, we study the effects of partial fluorination of the para-sexiphenyl p-6P molecule with chemical modifications of one head group p-6PF2 or both head and tail p-6PF4. We show that quantum and classical simulations both find consistent and highly distinct dipole moments for the three studied molecules. The diffusion of both p-6P and its fluorinated derivatives is Arrhenius-like, governed by thermally activated energy barrier crossings. Also, p-6P has a lower diffusion energy barrier compared to its fluorinated derivatives in the nonpolar direction of the anisotropic surface, while the barrier in the polar direction is about 20 kJ/mol higher. This rather unexpected behaviour is governed by a subtle balance of electrostatic attractive and repulsive molecule-substrate interactions as well as substantial entropic contributions coming from orientational and internal molecular degrees of freedom. Our findings can help to control the kinetics of nucleation and growth in the future design of hybrid organic-inorganic interfaces.