Regensburg 2013 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 40: Focus: Van der Waals at soft matter interfaces: structure and dynamics

CPP 40.4: Talk

Thursday, March 14, 2013, 10:45–11:00, H39

Influence of van der Waals interactions on morphology and dynamics in ultrathin liquid films at silicon oxide interfaces — •Daniela Täuber and Christian von Borczyskowski — nanoMA, TU-Chemnitz, Institut für Physik

Liquids show molecular layering close to interfaces with solids [1]. Its extend is influenced by substrate roughness, humidity and the type of liquid. From studies on wetting behavior, the influence of substrate material on film thickness is known, while also structure formation and dynamics in thin liquid crystal films appeared to depend on the type and thickness of the silicon oxide [2]. Single molecule tracer diffusion studies of evaporating ultrathin tetrakis-2-ethyl-hexoxysilane (TEHOS) films on silicon with 100 nm thermal oxide reveal a slowdown of the tracer mobility 1-2 nm above the substrate [3]. An ellipsometric study of thinning TEHOS films on silicon with 100 nm thermal or 2 nm native oxide yields further information. On the thermal oxide, a lateral flow of the liquid is observed, while the film on the native oxide forms an almost flat surface and shows negligible flow. In addition, we found a significantly smaller initial film thickness in case of the native oxide. We ascribe these differences to van der Waals interactions with the underlying silicon in case of the native oxide, whereas the thermal oxide suffices to shield those interactions [3].

[1] M. L. Forcada, C. M. Mate, Nature 363 (1993) 527. [2] B. Schulz, D. Täuber, J. Schuster, T. Baumgärtel, and C. von Borczyskowski, Soft Matter 7 (2011) 7431. [3] D. Täuber, I. Trenkmann, and C. von Borczyskowski, submitted.