Dresden 2006 – scientific programme
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MM: Metall- und Materialphysik
MM 27: Diffusion I
MM 27.4: Talk
Thursday, March 30, 2006, 11:00–11:15, IFW B
Self-diffusion in Amorphous Silicon Nitride — •Harald Schmidt1, Mukul Gupta2, and Michael Bruns3 — 1Fakultät für Natur- und Materialwissenschaften, TU Clausthal, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld, Germany — 2Laboratory for Neutron Scattering, ETH Zürich & PSI, Villigen, CH-5232, Switzerland — 3Institut für Instrumentelle Analytik, Forschungszentrum Karlsruhe GmbH, D-76021 Karlsruhe, Germany
Amorphous silicon nitride is a model system for a covalently bound amorphous solid with extremely low atomic mobilities where reasonable values of self-diffusivities are still lacking. We used neutron reflectometry on isotope enriched Si314N4/Si315N4 multilayers to determine nitrogen self-diffusivities ranging from 10−24 to 10−21 m2/s between 950 and 1250 oC. Time dependent diffusivities observed at 1150 oC indicate the presence of structural relaxation. For long annealing times (relaxed state) the diffusivities follow an Arrhenius law with an activation enthalpy of 3.6 eV. Possible diffusion mechanisms are discussed and the results are compared to the Si and N diffusivities in polycrystalline silicon nitride as obtained by Secondary Ion Mass Spectrometry.