Dissociative diffusion of nickel in silicon, and sinks and sources of vacancy annihilation and generation in the crystal bulk

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In-diffusion and annealing processes of substitutional nickel atoms in dislocation-free silicon are studied at 960°C to distinguish between the site exchange mechanisms of the nickel atoms. The concentration of substitutional nickel atoms varies exponentially with time according to the theory of dissociative mechanism in both processes. Interstitial nickel atoms in dislocation-free silicon precipitate in the bulk as confirmed by an infrared microscopy. Nickel precipitates play an important role in the vacancy generation and annihilation. It is suggested that, in dislocation-free silicon, nickel diffuses under the dissociative mechanism, the dominant point defects mediating the site exchange of nickel atoms are vacancies, and that the crystal surfaces, and nickel precipitates or precipitate-induced lattice defects play a role as the sinks and sources of vacancy annihilation and generation. The rate-limiting step for the site exchange of substitutional nickel atoms is the diffusion of vacancies in the silicon crystal.