Regensburg 2025 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 35: Transport in Materials: Diffusion, Charge or Heat Conduction

MM 35.2: Talk

Friday, March 21, 2025, 10:30–10:45, H22

Investigation of lateral hydrogen diffusion in polycrystalline molybdenum trioxide thin films — •Tim K. Hecker, Martin Becker, and Peter J. Klar — Institute of Experimental Physics I and Center for Materials Research, Justus Liebig University Giessen, Giessen, Germany

Molybdenum trioxide thin films were prepared by RF sputter deposition exploring a wide range of growth parameters. To characterise the thin films, electrochemical, Raman, and XRD experiments were conducted. In order to gain a deeper understanding of the diffusion of hydrogen in these thin films, the samples were microstructured with a PMMA film in a way that restricts the contact surface with the electrolyte to a narrow stripe-like gap. This enables the lateral diffusion of hydrogen beneath the PMMA film to be studied using a transmission experiment, making use of the electrochromic properties of molybdenum trioxide. This increases the accessible spatial and temporal scale by several orders of magnitude, significantly improving the spatial and temporal resolution of the in-situ transmission measurement. Spatially resolved transmission measurements in the wavelength range of 633±55 nm demonstrate that the investigated diffusion is dependent on the hydrogen concentration. The results are also supported by a spatially and temporally resolved diffusion simulation. Furthermore, the measurement method presented here is universally applicable to electrochromic thin film samples.

Keywords: concentation dependent diffusion; hydrogen diffusion; in situ transmission spectroscopy; RF sputter deposition; molybdenum trioxide