Non-Standard Fickian Self-Diffusion of Isotopically Pure Boron Observed by Neutron Reflectometry and Depth Profiling

ABSTRACTNeutron reflectometry (NR) studies1 of thin films of amorphous 11B/l0B on silicon indicate that a non-standard form of Fickian diffusion occurs across the boron interface upon annealing. In order to verify this observation, the samples were examined by neutron depth profiling (NDP). Comparison of the results from models of a step function, standard Fickian diffusion and Fickian diffusion with a fixed composition at the interface were made and compared to the previous NR results. The diffusion constant resulting from the non-standard Fickian model for the NDP data differs slightly from that obtained from the commonly used Fickian diffusion model and is not inconsistent with the NR results. This finding suggests that more information regarding diffusion at interfaces can be gained from these higher resolution neutron scattering techniques.