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| Home > Publications database > Detection of hydrogen in thin films through resonant neutron reflectometry via a magnetic layer |
| Conference Presentation (After Call) | FZJ-2023-00967 |
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2023
Abstract: The study of hydrogen diffusion and storage in different materials is crucial in the challenge of an actual implementation of sustainable energy sources, but also to explore the possible modification of electronic, magnetic and optical properties of the host material. Amongst the most widely used techniques to study hydrogen absorption in thin films are neutron (NR) and X-ray reflectometry (XRR). XRR allows to track the thickness changes of the absorbing layer, while NR gives in addition direct information about the absorbed hydrogen content. Nonetheless, NR is a relatively time-consuming measurement, with a sensitivity limit that greatly depends on the counting time. The detection limit is at about 5% atomic concentration.In this contribution we propose to apply resonant neutron reflectometry (RNR) [1]. The method is model-free and allows to measure smaller (<5%) concentrations of hydrogen absorbed in situ, with smaller counting times and with a higher sensitivity. Inserting a magnetic layer into the hydrogen absorbing layer a magnetic wave guide for neutrons is formed. On hydrogen loading the scattering potential of the system is modified which is seen in the position of the resonance formed due to the contrast between the scattering potential of the absorbing layer and its neighbours. The requirements for the magnetic thin film and the absorbing layer are discussed. We will present experiments performed on Al2O3/Nb(x)/Co(3nm)/Nb(x)/Pt(3nm) thin films demonstrating that hydrogen concentrations below 1% and absorption kinetics of few seconds can be measured using this method.Furthermore by combining information given by in situ XRR and RNR performed at NREX, a neutron reflectometer at the Heinz Maier-Leibnitz Zentrum in Garching, Germany we were able to observe peculiarities in the absorption process of niobium. In this contribution we will discuss the current results and give an overview on how magnetic properties of thin films like the depth resolved magnetic moment can be studied with polarized neutron reflectometry.[1] L. Guasco, Yu. N. Khaydukov, S. Pütter, L. Silvi, M. A. Paulin, T. Keller, and B. Keimer, Nat. Comms. 13 (2022) 1486
Keyword(s): Magnetic Materials (1st) ; Magnetism (2nd) ; Condensed Matter Physics (2nd)
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