Segregation-controlled kinetics of fast impurity diffusion in polycrystalline solids

Commonly, the presence of grain boundaries in crystalline solids leads to enhanced atomic transport because atoms can move faster along such two-dimensional lattice defects than through the lattice itself. Recent experiments on gold diffusion into silicon, however, showed for the first time a retardation of the metallic impurity incorporation in polycrystalline material compared to that of monocrystals of the same host. The present paper provides a new model that accounts for the experimental findings with regard to Si:Au. In addition, it may apply to other systems in which a high mobility of the impurity in the lattice goes along with extremely strong segregation effects.