Regensburg 2004 – scientific programme

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O: Oberflächenphysik

O 32: Nanostrukturen III

O 32.1: Talk

Thursday, March 11, 2004, 11:15–11:30, H38

STM, TDS and LEED examinations of trimesic acid on single crystal surfaces — •Lorenz Kampschulte, Robert Kraus, Stefan Griessl, and Wolfgang Heckl — Department für Geo- und Umweltwissenschaften, LMU München, Theresienstr. 41, 80333 München, www.nano.geo.uni-muenchen.de

The adsorption of trimesic acid (TMA) on single crystal surfaces was studied by STM (Scanning Tunnelling Microscopy), TDS (Thermal Desorption Spectroscopy) and LEED (Low Energy Electron Diffraction). Trimesic acid consists of a benzene ring with three carboxylic groups in symmetric 1,3,5-positions. Three different single crystals were used as substrates: graphite(0001), silver(111) and gold(111).

The measurements were done under Ultra High Vacuum (UHV) conditions, the trimesic acid was evaporated on different substrates using an effusion cell. The preparation of a TMA monolayer was observed and adjusted with thermal desorption spectroscopy. From these measurements it was possible to deduce the binding conditions. In all cases characteristic periodically arranged structures could be demonstrated. In the monolayer regime the structure is characterized by non-dense-packing of molecules on the surface. It was shown that, depending on the substrate material and the preparation method, different network structures could be assembled. These networks are induced by directed hydrogen bonding (self assembly), forcing the organic molecules to build a two-dimensional grid architecture with small cavities.