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MM: Fachverband Metall- und Materialphysik

MM 17: Postersession I

MM 17.3: Poster

Montag, 16. März 2015, 18:00–20:00, Poster E

Kinetics of Hydrogen uptake in epitaxial thin films of Niobium — •Niklas Teichmann, Vladimir Burlaka, Stefan Wagner, and Astrid Pundt — Univ. Göttingen, IMP, Friedrich- Hund-Platz 1, 37077 Göttingen, Germany.

Hydrogen located in interstitial lattice sites changes physical properties of the host metal, such as the resistivity or the lattice parameter.[1,2] Even though both physical properties are not linearly coupled to the hydrogen content, strong changes occur upon phase transitions. Therefore, they can be used to determine the concentration change and the onset of phase transition in thin films. In this paper we report on in-situ studies on the kinetics of the hydrogen uptake in thin Nb films (8 nm - 40 nm ) with different Pd capping layers (0,2 nm - 20 nm). All experiments are performed without breaking the UHV conditions. Hydrogen is loaded step-wise from the gas-phase. It will be shown that even down to a Palladium capping layer thickness of 2 nm the kinetics of Hydrogen uptake is fast. It is dramatically reduced below that thickness. This effect is attributed to an island-like Pd-layer morphology that arises for the thinnest capping layer thicknesses. Also, the unloading kinetics is reduced when island-like capping layers are used.

Financial support by the DFG via projects PU131/9-1 and PU131/12-1 is gratefully acknowledged.

[1] A. Pundt, R. Kirchheim, Ann. Rev. Mater. Sci. 2006

[2] K. Nörthemann, & A. Pundt, (2008). Coherent-to-semi-coherent transition of precipitates in niobium-hydrogen thin films. Physical Review B, 78(1), 014105.