| AVS 62nd International Symposium & Exhibition | |
| Atom Probe Tomography Focus Topic | Tuesday Sessions |
| Session AP+AS-TuM |
| Session: | New Applications of Atom Probe Tomography |
| Presenter: | Stephan Gerstl, ETH Zürich, Switzerland |
| Authors: | S.A. Gerstl, ETH Zürich, Switzerland B. Scherrer, ETH Zürich, Switzerland J.M. Cairney, University of Sydney, Australia R. Spolenak, ETH Zürich, Switzerland R. Wepf, ETH Zürich, Switzerland |
| Correspondent: | Click to Email |
Atom probe tomography has progressively engaged the world of materials characterization with 3-dimensional nanometer-level maps of various dense materials. These atom maps have been the attraction of the technique because they enable new perspectives and analysis of solid materials literally atom by atom. The analysis of soft organic materials, even aqueous solutions, has however been a long-standing issue as it is impaired by contamination, uncertain phase formation, and questionable observed states. These outcomes have been interrogated, retested, and re-analyzed to better understand the artifacts involved. Here we present the development steps achieved together with the APT results obtained of three aqueous based solutions: a water-based citrate solution, a 1:1 water-ethanol mixture, and a commercially available marginally alcoholic beverage. These aqueous solutions were chosen so as to exhibit differences in their mass-spectrum response due to their dissimilarities. The methodologies enabling these analyses require arresting the liquids so they are stable in vacuum environments, sharpening them to a needle geometry, and transporting them between chambers whilst not altering their structural integrity; all steps being done close to LN2 temperatures. The main challenge was with contamination, which needs to be minimized and separated from the material of interest in the analysis. The cryo-fixation method involves plunge freezing the region of interest (ROI) in cryogenic liquids, sharpening the ROI in a FIB fitted with a cryogenically cooled stage, and field evaporating it in a retrofitted cryo-transfer enabled LEAP 4000X-HR.
All aqueous specimens could be analyzed successfully; with the resulting amounts of ROI analyzed being small (only a thin film is probed due to sample geometry), trends and fluctuations in ion concentrations have been interrogated and will be presented.
The application space of this technique will be considered in terms of using fluids as matrices and designing the experiments to increase the volume of soft materials analyzed.