Investigation of atomic-scale decorations on mixed conducting oxides via time-of-flight secondary ion mass spectrometry (ToF-SIMS)

• Published in: Applied surface science Vol. 640; p. 158312
• Main Authors: Fahrnberger, Florian, Siebenhofer, Matthäus, Hutter, Herbert, Kubicek, Markus
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-12-2023
• Subjects: Mixed ionic electronic oxides; Oxidic decorations; Secondary ion formation; Surface-near dipoles; ToF-SIMS; Mixed ionic electronic oxides; Secondary ion formation; ToF-SIMS; Oxidic decorations; Surface-near dipoles
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2023.158312

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•Novel ToF-SIMS investigations of La0.6Sr0.4CoO3-δ (LSC) and its decoration oxides.•Decoration acidity reveals surface dipoles and differences in total ion yield.•The cationic radius impacts the secondary ion (SI) generation critically.•Stoichiometric variations based on decoration oxide-perovskite interaction.•Insights into localized electrostatic effects and non-trivial surface changes.
Sub-nanometer modifications of mixed ionic electronic conducting (MIEC) materials, like the perovskite La0.6Sr0.4CoO3-δ (LSC), represent a promising approach to improving their oxygen exchange kinetics and degradation stability. The complex interactions between decoration layers and the host material are still not fully understood and are a subject of current research. Under these circumstances, a novel approach using time-of-flight secondary ion mass spectrometry (ToF-SIMS) was developed to gain deeper insight into the electronic and chemical interactions of LSC with different oxidic decorations. The investigated samples were prepared by pulsed laser deposition (PLD) on YSZ single crystals, starting with a 100 nm thin LSC layer, which was then modified by sub-nm decorations of CaO, TiO2, and SnO2 (nominally 0.05–0.5 nm) on top. By using ToF-SIMS with a sampling depth of 1–2 nm, it was possible to extract information simultaneously on the decoration layer and the host oxide. Significant differences in secondary ion (SI) intensities of the host material LSC were found that can be attributed to the formation of surface-near dipoles as a consequence of the acidic or basic nature of the decoration oxide. Further, relative stoichiometric variations of the La+, Sr+, and Co+ signals depending on the decoration oxide were observed, suggesting different preferential decoration sites on the LSC surface.