Regensburg 2022 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 35: Nanomaterials: Structure & Properties

MM 35.2: Vortrag

Donnerstag, 8. September 2022, 16:00–16:15, H46

Atom Probe Study of self-assembled Monolayers — •Helena Solodenko, Patrick Stender, and Guido Schmitz — University of Stuttgart, Institute for Materials Science, Heisenbergstr. 3, 70569 Stuttgart

Atom probe tomography is a well-established characterization technique for metals, semiconductors, oxides and minerals. However, measurement of organic matter and biological materials is still challenging. Field evaporation of organic species leads to detection of CxHy groups, instead of single atoms. The fragmentation of the molecules possibly depends on the applied electric field strength and the nature of chemical bonding. Self-assembled monolayers (SAMs) represent a suitable model system to study the fundamental questions about field evaporation of such systems, since they represent a well-defined molecular film with a limited number of possible molecular fragments. Furthermore, a chemical bond is formed between substrate surface and the headgroup the SAM. By variation of the field strength, we expect to learn more about the field evaporation process and thus about the binding energies of the SAMs. We present measurements of alkane-thiolates on Pt and silanes on ZnO by laser-assisted APT. The backbone evaporates in the form of small hydrocarbon fragments consisting of one to four C atoms, while S evaporates exclusively as single ions. With increasing laser power, a significant trend towards larger fragment sizes is observed. Furthermore, comparison with liquid alkanes and cross linked alkane networks is insightful which demonstrates a continuous transition from evaporation of complete molecules to single atoms.