Correlation between the gettering efficiencies and the energies of interfaces in silicon bicrystals

A comparative study of the gettering efficiency of the twin grain boundaries ∑ = 25, ∑ = 13, and ∑ = 9 has been carried out by means of electron-beam-induced current measurements performed on quenched silicon bicrystals precontaminated by Cu or Ni. The extent of the denuded zone appearing on both sides of each interface type has been considered as the "rating" of its gettering efficiency. For both contaminants, the same scaling of the gettering efficiencies of the boundaries has been observed and was found to be in the ∑ = 9 ≪ ∑ = 13 < = 25. To account for this ranking, we have correlated the gettering efficiency to the excess energy of the grain boundary with respect to the bulk energy, as the theoretically calculated. The computational procedures have been performed by means of molecular-dynamics simulations using several potentials. On the basis of the specific disorder affecting the ∑ = 25 structure upon heat treatment, our calculations provided the same progression for the interfacial energies as that observed experimentally for the gettering efficiencies of the corresponding grain boundaries according to the extents of the appropriate denuded zones. Calculations of the strain fields developed by the three grain boundaries also support this view.