Regensburg 2022 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Poster 2

CPP 17.9: Poster

Tuesday, September 6, 2022, 11:00–13:00, P2

Laser control over crystallization and morphology of tetracene thin films — •Stefan Kowarik¹, Andika Asyuda², Linus Pithan³, and Andreas Opitz⁴ — ¹Physical Chemistry, University of Graz, Austria — ²Institute for Physical Chemistry, Universität Heidelberg, Germany — ³Institut für Angewandte Physik, Universität Tübingen, Germany — ⁴Institut für Physik, Humboldt-Universität zu Berlin, Germany

Nucleation and crystallization in thin-film growth are notoriously difficult to steer, but optical control offers exciting new possibilities for selecting specific polymorphic forms [1] or aligning the crystallite orientation in thin films [2]. Here we report an increase in crystallite size in vacuum-deposited tetracene thin films under illumination with a wavelength tuned to a specific absorption band of tetracene crystals. The morphological changes are induced with linearly and circularly polarized light and the larger crystallite size is accompanied by higher photoluminescence of tetracene. We propose a mechanism based on optical heating of specifically oriented crystals during growth, which leads to enhanced surface migration processes in these crystals and consequently larger crystals via Oswald ripening effects. The light-induced temperature effects are distinct from substrate heating both for linearly and circularly polarized light. Laser illumination, therefore, is a novel control parameter of growth and enables high crystallinity even for low substrate temperature deposition.

[1] L. Pithan, et al., Crystal Growth & Design 15.3 (2015): 1319-1324. [2] L. Pithan, et al., Advanced Materials 29.6 (2017): 1604382.