Dresden 2009 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 3: Focus Session: Interactions of Molecules with Dielectric Surfaces

DF 3.2: Topical Talk

Monday, March 23, 2009, 15:05–15:25, WIL A317

Studying terephthalic acid on dielectric surfaces using non-contact atomic force microscopy — •Philipp Rahe, Markus Nimmrich, and Angelika Kühnle — Fachbereich Physik, Universität Osnabrück, Germany

Self-assembly of organic molecules is a promising route to fabricating devices on the nanometer scale. While the interaction of molecules with metallic surfaces has been investigated extensively, dielectric surfaces have been studied rather rarely due to both experimental as well as theoretical challenges. For obtaining real-space information on insulators, atomic force microscopy has been established as this technique is not limited to conducting substrates compared to scanning tunnelling microscopy.

Here, we have studied the adsorption characteristics and self-assembly of terephthalic acid (TPA) on two different substrates, namely titania and calcite, using non-contact atomic force microscopy operated under ultra-high vacuum conditions.

On the (110) surface of rutile titania we observe an ordered (2×1) structure at coverages of about 1 ML, which we attribute to an upright adsorption geometry of TPA. At lower coverages single molecules are observed. In contrast, on the (1014) surface of calcite the molecules are mobile at room temperature at coverages less than a monolayer. Experiments at 115 K reveal stable, well-ordered islands. Upon increasing the coverage to 1 ML, we observe a well-ordered structure, which is stable at room temperature. Comparing these two substrates we can evaluate the influence of the dielectric substrate on molecular self-assembly.