Single crystals with a <11•0> orientation were implanted with 300keV Bi ions, to doses of between 1014 and 1.3 x 1015/cm2, at temperatures of 5.5, 77 or 293K. Rutherford back-scattering and channelling with 1.5MeV He ions was used to determine the lattice locations of the implanted species. In the case of low-dose implantation at 293K, the octahedral interstitial sites were occupied. With increasing dose, the octahedral fraction decreased and a random distribution of Bi atoms was observed. The post-implantation of Mn shifted the Bi back to octahedral sites, while the Mn was entirely substitutional. A depth dependence of the octahedral fraction was observed in all cases, with the concentration being larger in near-surface regions. The implantation of Bi at 5.5K resulted in a substitutional fraction of 0.2; together with a random fraction. No change was observed after warming to 77K. However, upon warming to 293K the Bi shifted to octahedral sites. The implantation of Bi at 77K resulted in a substitutional fraction which was similar to that after 5.5K implantation. The shift of Bi atoms from random to octahedral sites during post-implantation and annealing, and the depth-dependence of the octahedral fraction, were attributed to the interaction of Bi atoms with vacancies so as to form Bi complexes (especially BiV6) on octahedral sites.

J.Hanssmann, O.Meyer: Materials Chemistry and Physics, 1996, 46[2-3], 118-22