Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 78: Poster: Surface Dynamics - Reactions, Elementary Processes and Phase Transitions

O 78.15: Poster

Mittwoch, 14. März 2018, 18:15–20:30, Poster A

Analysis and interpretation of TPD measurements of organic molecules — •Karolina Stoiber, Peter Deimel, Julian Lloyd, Francesco Alegretti, Joachim Reichert, Hartmut Schlichting, and Johannes V. Barth — Physics Department, Technical University of Munich, James-Franck-Straße 1, 85748 Garching, Germany

In surface science, thermal programmed desorption (TPD) is one of the most traditional measuring techniques for the investigation of adsorbed species. Typically, a well-defined substrate covered with the molecules under investigation is heated up with a constant heating rate. Depending on kinetic parameters and the arrangement on the surface, desorption occurs at distinct temperatures with characteristic rates, until the substrate is depleted. Moreover, the interpretation of TPD spectra requires additional information gathered from methods like scanning tunnelling microscopy (STM). We realized a setup consisting of a TPD chamber flanged to a STM unit and a controlled ion beam deposition (CIBD) system to investigate large functional molecules and their assemblies on clean substrates. The TPD chamber provides a STM-compatible sample holder which can be cooled down to liquid nitrogen temperatures and heated up to some 1500 K for measuring. A quadrupole mass spectrometer, with a Feulner cup enhancing the desorbing flux of molecules, monitors the desorption rate. Together with the recorded temperature, binding energies and preexponentials of bisphenol A and diethylstilbestrol on Cu(111) are extracted and the TPD spectra are simulated with analytical and Monte Carlo methods.