  Vacancy-mediated diffusion of impurities under strong impurity-vacancy (I-v)
attraction has been studied in the framework of the five-frequency model (5FM)
for the FCC host. The system of impurities and tightly bound I-v pairs has been
treated in the framework of the rate-equations approach of Cowern et al., Phys.
Rev. Lett. 65, 2434 (1990), developed for the description of the non-Gaussian
diffusion profiles (NGDPs) observed in dopant diffusion in silicon. In the
present study this approach has been extended to derive a three-dimensional
(3D) integro-differential equation describing the pair-mediated impurity
diffusion. The equation predicts the same 1D NGDPs as in Cowern et al. but can
be also used for the simulation of 3D profiles of arbitrary geometry in the
systems where the diffusion proceeds via a mobile state. The parameters of the
theory has been calculated within the 5FM on the basis of available literature
data. The database on impurities in aluminum host has been analyzed and
promising impurity-host systems for the observation of NGDPs has been
identified. The diffusion profiles for an impurity where NGDPs are expected to
be easily detectable have been simulated. It has been argued that with the
input parameters calculated on the basis of experimental diffusion constants
the simulated NGDPs can be accurate enough to serve as a quantitative test of
the 5FM.
