LATTICE LOCATION OF BISMUTH IMPLANTED INTO BERYLLIUM SINGLE-CRYSTALS

Bi ions have been implanted into [11 (2) over bar 0] Be single crystal s at T = 5.5, 77 and 293 K using doses between 1 X 10(14) atoms/cm(2) and 1.3 x 10(15) atoms/cm(2) and an ion energy of 300 keV. In situ Rut herford backscattering (RES) and channeling with 1.5 MeV He ions was u sed to determine the lattice location of the implanted species. For lo w dose implantation at 293 K we observed occupation of octahedral inte rstitial sites. With increasing dose the octahedral fraction decreased and a random distribution of Bi atoms was observed. By postimplantati on of Mn, Si shifted back to octahedral sites, while Mn was totally su bstitutional. In all cases a depth dependence of the octahedral fracti on was observed being larger in near surface regions. Implantation of Bi at 5.5 K resulted a substitutional fraction of f(s) = 0.2, together with a random fraction. No change was observed after warming up to 77 K; however upon warming up to 293 K, Bi shifted to octahedral sites. Implantation of Bi at 77 K resulted in f(s) values similar to those fo r 5.5 K implantation, The shift of Bi atoms from random to octahedral sites during postimplantation and annealing and also the depth depende nce of the octahedral fraction are attributed to the interaction of Bi atoms with vacancies (V) forming BiVx complexes and especially BiV6 f or Bi on octahedral sites.