Regensburg 2007 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 32: Diffusion and point defects I

MM 32.1: Talk

Thursday, March 29, 2007, 10:15–10:30, H6

Diffusion of Hydrogen in Amorphous Ceramics of the System Si-B-C-N — •Wolfgang Gruber, Günter Borchardt, and Harald Schmidt — TU Clausthal, Institut für Metallurgie, Thermochemie und Mikrokinetik - AG Materialphysik

Non-oxide ceramics of the system Si-B-C-N have potential applications as high temperature structure materials, surface coatings and dopable semiconductors. Materials produced from polymeric precursors which are transformed into amorphous covalent ceramics by solid state thermolysis are separated in a silicon rich phase and a carbon rich phase. Diffusion of hydrogen plays an important role in the investigation of the mobility and the kind of defects in the amorphous state. Therefore we measured the diffusivities of hydrogen in amorphous ceramics of the system Si-B-C-N with different compositions. For the diffusion measurements we used deuterium as a tracer which was introduced into the samples via isotope exchange from the gas phase. Depth profiling was done with secondary ion mass spectrometry (SIMS). Depending on the composition the diffusion path for hydrogen is the carbon rich phase or the silicon rich phase. A direct interstitial diffusion mechanism accounts for the diffusion of hydrogen in the carbon rich phase and a trap limited diffusion mechanism accounts for the diffusion of hydrogen in the silicon rich phase.