Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 47: Topical Session Modern Atom Probe Tomography III - Functional and Nanostructured Materials

MM 47.2: Talk

Thursday, March 29, 2012, 10:45–11:00, H 0107

Laser-assisted atom probe tomography of self-organized surface layers — Andreas Stoffers, Martin Lütkemeier, and •Guido Schmitz — Institut für Materialphysik der Westf. Wilhelms-Universität, Münster, Germany

The availability of femtosecond lasers opened analysis of new material classes by atom probe tomography (APT). Laser-assisted APT has even the potential to give microstructural and chemical information on organic materials at an atomic scale. We investigated the model cases of polyelectrolyte multilayers (PEM) and self-assembling monolayers (SAM). PEMs are deposited step by step as a multilayer of poly-anions and poly-cations to sharp gold tips. SAMs are adsorbed in a self-assembling process to the apex of gold tips, but offer only a limited volume for analysis.

We could successfully analyze multilayers of the polyions poly(acrylic acid), poly(diallyldimethyl-ammonium chloride), poly(styrene sulfonate) and poly(allylamine hydrochloride). Also the chemical structure of perfluorodecanethiol and alcanethiolate SAM was studied. In all cases, mass spectra are complex, indicating different molecular fragments. We could determine the polyanion/polycation stoichiometry in polyelectrolytes, also the amount of counterions. Mass spectra of fluorinated SAM are easily identified. Even the evaporation sequence of molecule fragments could be determined in this case. It appears to be remarkably different to that of structurally similar alcanethiolate monolayers.