Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 59: Poster Session II (Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: arrays; Nanostructures at surfaces: Wires, tubes; Nanostructures at surfaces: Other; Plasmonics and nanooptics; Metal substrates: Epitaxy and growth; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsoprtion of organic / bio molecules; Metal substrates: Adsoprtion of inorganic molecules; Metal substrates: Adsoprtion of O and/or H; Metal substrates: Clean surfaces; Density functional theory and beyond for real materials)

O 59.75: Poster

Wednesday, March 24, 2010, 17:45–20:30, Poster B1

A Nanocalorimeter for Adsorption Studies of Organic Molecules — •H.-J. Drescher, F. Bebensee, O. Lytken, H.-P. Steinrück, and J. M. Gottfried — Lehrstuhl für Physikalische Chemie II, Egerlandstraße 3, 91058 Erlangen

Surface nanocalorimetry (SNC) is an UHV based technique for the measurement of adsorption enthalpies on well defined substrates. It is the only technique that provides access to adsorption enthalpies in cases of non-reversible adsorption, i.e., if decomposition occurs at lower temperature than desorption. Typical examples are large organic molecules on metal substrates. SNC relies on the direct measurement of very small temperature changes induced by the adsorption of molecules on single-crystal surfaces. Its outstanding sensitivity in the nanojoule and picomole regimes is achieved by pyroelectric detectors in combination with pulsed molecular beams and highly accurate flux, sticking probability and reflectivity measurements. The adsorption enthalpy is a direct measure for the strength of the adsorbate-substrate interaction and thus one of the most important parameters for the quantitative characterization of chemical bonds at surface and interfaces. We focus especially on metal/organic interfaces, which occur in organic electronic devices. The character of the interfacial bond determines crucial parameters for the device performance, such as the charge injection rate. A setup of an advanced adsorption calorimeter is presented, which is optimized for the studies of π-conjugated molecular semiconductors on metal single-crystal surfaces. It features several new technical developments, which lead to improved sensitivity and accuracy.