Motion of a substitutional impurity via a fast-diffusing intermediate species is discussed. An analytical solution is given for the case of low impurity concentration. For short times, few atoms migrate and the solution behaves exponentially. We observe this exponential signature in the diffusion of nanometer-scale B-doping profiles in Si. The migration frequency during oxidation-enhanced diffusion is consistent with diffusion-limited kickout of an interstitial-type B species. This is the first direct experimental evidence for dopant diffusion in Si via an intermediate species.
Interactions between self-interstitials (I) and {113} interstitial defects during annealing of Si implant damage have been studied. At low damage levels diffusion is ultrafast, driven by I released direct from the ion collision cascade. At higher damage levels, free I are quenched by nucleation of {113} defects. We show that the transient enhanced diffusion seen in most previous studies arises from the subsequent dissolution of the {113} defects.
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