Dresden 2009 – scientific programme

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DS: Fachverband Dünne Schichten

DS 22: Organic Thin Films II

DS 22.3: Talk

Wednesday, March 25, 2009, 11:45–12:00, GER 38

Crystalline to semi-crystalline phase transitions in thin n-Dotriacontane films on solid surfaces — Edgardo A. Cisternas¹, Tomás Corrales¹, Valeria del Campo¹, •Ulrich G. Volkmann¹, Haskell Taub², and Flemming Y. Hansen³ — ¹Surface Lab, Facultad de Física, Pontificia Universidad Católica de Chile, Chile — ²Department of Physics and Astronomy, University of Missouri-Columbia, USA — ³Department of Chemistry, Technical University of Denmark, Denmark.

We present evidence from ellipsometric measurements of crystalline to semi crystalline or rotator transitions on molecularly thin films of the intermediate length alkane n-Dotriacontane (n-C₃₂H₆₆), grown on Si(100) substrates covered with their native oxide layer. We are able to grow films with three different morphologies: 1) submonolayer coverage with the molecules perpendicular to the surface, 2) multilayered films with high coverage of the first perpendicular layer without bulk and 3) multilayered films with bulk particles. For submonolayer coverage films we found one step in the ellipsometer signal at ∼331 K which can be correlated to a rotator phase transition. For multilayered films we observe additional steps in the ellipsometric signal which are correlated to changes in upper molecular layers and to rotator phases in bulk crystallites, respectively. A theoretical interpretation of the ellipsometric data is presented to explain these steps in the signal as changes in the anisotropy of the polarizability tensor of the alkane molecules.