Dresden 2009 – scientific programme

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DS: Fachverband Dünne Schichten

DS 18: Layer Properties: Electrical, Optical and Mechanical Properties II

DS 18.4: Talk

Wednesday, March 25, 2009, 12:00–12:15, GER 37

Mechanical stress impact on thin film thermodynamic properties - investigated by hydrogen loading — •Stefan Wagner and Astrid Pundt — Institut für Materialphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

Thermodynamic properties of thin films deviate strongly from those of bulk. The deviations are reported to originate from microstructure and from mechanical stress, while the contribution of both is unknown in particular. Focussing on the mechanical stress impact and applying PdHx and PdyFe1-yHx as model systems, it is shown that mechanical stress strongly changes phase transition pressures. Hydrogen absorption and hydride formation are monitored by in situ four point resistance measurement. For PdHx films the hydride formation pressures shift up to 400 mbar in contrast to 18 mbar for bulk. These shifts relate to the films adhesion to the substrate and can be affected by film detachment. It will be shown that freestanding PdHx films down to 30 nm film thickness behave bulk-like.