Regensburg 2022 – scientific programme

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O: Fachverband Oberflächenphysik

O 28: Organic Molecules at Surfaces 3: Theory

O 28.9: Talk

Tuesday, September 6, 2022, 12:30–12:45, S051

Polymorph trapping by optimized deposition conditions: A first-principles prediction for TCNE/Cu(111) — •Anna Werkovits, Andreas Jeindl, Lukas Hörmann, Johannes J. Cartus, and Oliver T. Hofmann — Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria

Physical properties of small-molecule organic semiconductors are strongly determined by their polymorphs. Depending on the orientation in which molecules adsorb on the substrate, properties can significantly vary, as is the case, e.g. for tetracyanoethylene (TCNE) on Cu(111).

We propose conditions under which TCNE remains in the energetically less favorable lying position also for higher coverages. This requires fulfilling two prerequisites: To enable ordered growth, the temperature must be high enough to allow for sufficient diffusion of lying molecules, whereas the temperature must be low enough to inhibit the reorientation to the upright-standing position.

In this work, we utilize the nudged elastic band method and density functional theory to compute energy barriers. By means of the harmonic transition state theory temperature-dependent diffusion and reorientation rates are obtained for predicting a temperature range where the kinetic stabilization is attained.