Morphological and structural investigation of alpha-sexithiophene grown on KCl (100)

Günther Schwabegger; Tatjana Djuric; Helmut Sitter; Roland Resel; Clemens Simbrunner

doi:10.1117/12.2023017

19 September 2013 Morphological and structural investigation of α-sexithiophene grown on KCl (100)

Günther Schwabegger, Tatjana Djuric, Helmut Sitter, Roland Resel, Clemens Simbrunner

Proceedings Volume 8818, Nanostructured Thin Films VI; 88180U (2013) https://doi.org/10.1117/12.2023017
Event: SPIE NanoScience + Engineering, 2013, San Diego, California, United States

Abstract

α-sexithiophene was deposited on KCl (100) by hot wall epitaxy technique at different substrate temperatures (60 °C 135 °C). The morphological investigation was performed by AFM and optical microscopy, revealing terraced islands and needle-like anisotropic structures. Structural investigations were performed by specular XRD scans. Upright standing molecules have been detected, which could be related to the terraced islands ((100) crystal contact plane). Furthermore, (010) and (-411) crystal planes have been observed, which explains the observed nano-needles (flat lying molecules). The texture was investigated by XRD pole figures, showing that all three crystal types exhibit a well defined azimuthal alignment with respect to KCl high symmetry directions. Interestingly, the epitaxial orientation of the islands could be explained by ledge directed epitaxy, which describes the nucleation of crystallites on existing topographic features on the substrate (nano-needles). A real space model of the crystallites was developed with the help of XRD pole figures and single crystal data. Surprisingly, the azimuthal orientation of the long moleculear axis is exactly the same for needles with (010) and (-411) contact planes. This observation represents a hint that the adsorption geometry of single molecules seems to be decisive for the organic crystal nucleation. Additionally, the substrate surface symmetry is nicely reflected by the multiplicity of formed needle orientations.

Citation Download Citation

Günther Schwabegger, Tatjana Djuric, Helmut Sitter, Roland Resel, and Clemens Simbrunner "Morphological and structural investigation of α-sexithiophene grown on KCl (100)", Proc. SPIE 8818, Nanostructured Thin Films VI, 88180U (19 September 2013); https://doi.org/10.1117/12.2023017

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