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DS: Fachverband Dünne Schichten
DS 29: Poster: Molecular Spintronics, Biomolecular and Functional Organic Layers, Organic Electronics and Photovoltaics, Plasmonics and Nanophotonics, Organic Thin Films, Nanoengineered Thin Films, Thin Film Characterisation,
DS 29.41: Poster
Mittwoch, 24. März 2010, 15:00–17:30, Poster A
Formation of palladium hydrides in low temperature Ar/H2-plasma — •Harm Wulff, Marion Quaas, Heiko Ahrens, Oxana Ivanova, and Christiane A. Helm — University of Greifswald, Institute of Physics, F.-Hausdorff-Str. 6, 17487 Greifswald
A specific challenge in low temperature plasma science is the investigation of chemical reactions in solid surface layers as a response to external plasma parameters.
20 nm thick palladium films were exposed to argon-hydrogen microwave plasma using different negative substrate voltages to study the hydride formation. The palladium hydride films were investigated by grazing incidence x-ray diffractometry (GIXD, Hasylab, Hamburg - Surface layers in reactive plasmas - project I-20080137)), in-situ high temperature x-ray diffractometry (HT-GIXD), x-ray reflectometry (XR) and atomic force microscopy (AFM).
The effect of hydrogen plasma depends on the applied negative bias voltage. Up to -50 V we observe an increase of the fcc Pd unit cell volume. Hydrogen atoms occupy octahedral interstices to form PdH0.55. However, bias voltages of -100 V and -150 V cause a shrinking of the fcc Pd unit cell in two steps to fcc PdVacI and fcc PdVacII. Subsequent reactions under long time plasma exposure form cubic PdH1.33. HT-GIXD experiments confirm the existence of different palladium hydrides. PdH0.55 lost its hydrogen at temperatures > 600 K. From the phase transformations PdH1.33 (> 700 K) –> PdVacII (1000 K) –> PdH1.33 we draw the conclusion that PdVac is a hydride compound. The formation mechanisms of palladium hydrides will be discussed.