Nitrogen diffusion in amorphous silicon nitride isotope multilayers probed by neutron reflectometry.
Amorphous silicon nitride is a model system for a covalently bound amorphous solid with a low atomic mobility where reasonable values of self-diffusivities are still lacking. We used neutron reflectometry on isotope enriched Si3 14N4/Si3 15N4 multilayers to determine nitrogen self-diffusivities ranging from 10(-24) to 10(-21) m2/s between 950 and 1250 degrees C. Time dependent diffusivities observed at 1150 degrees C 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 +/- 0.4) eV. The results are indicative of a direct diffusion mechanism without the involvement of thermal point defects.
AG Thermochemie und Mikrokinetik, Fakultät für Natur-und Materialwissenschaften, TU Clausthal, D-38678 Clausthal-Zellerfeld, Germany.
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Schmidt
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Gupta
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Bruns