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MM: Fachverband Metall- und Materialphysik

MM 65: Nanomaterials - II

MM 65.4: Vortrag

Donnerstag, 19. März 2020, 18:15–18:30, IFW D

Atom Probe Tomography of self-assembled Monolayers — •Helena Solodenko and Guido Schmitz — Institute for Material Science, Heisenbergstr. 3, 70569 Stuttgart

In order to achieve molecular heterogeneous catalysis in confined geometries, catalyst molecules are linked to nanometer-sized pores within a matrix. The linkage of catalyst to the pores is crucial and therefore this project focuses on this aspect. We utilize simple model molecules which form by self-organization, so-called self-assembled monolayers (SAM), and investigate them by atom probe tomography (APT). This technique excels at chemical sensitivity and provides furthermore three-dimensional spatial information of the probed samples. The goal is to achieve physical understanding of field desorption of organic molecules under high electric fields. Experiments are conducted by preparation of nanometer-sized metallic needles, which are cleaned by field-evaporation and then coated by dipping in the according solution of thiol-based SAMs for several hours. The resulting monolayer has a thickness of less than two nanometers and is analyzed by laser-assisted APT. The carbon chains break under the influence of the high electric fields and corresponding molecular fragments are detected by time-of-flight mass spectrometry. The reconstruction reveals an ordered evaporation sequence of the molecule chain down to the substrate and provides information of surface coverages of the SAMs. Furthermore, SAMs of phosphonic acids are used, which bind to oxide materials like SiO2, Al2O3 and their evaporation behavior is compared to thiol-based SAMs.