Lattice location by channeling angular distributions: Bi implanted in Si

Measurements of 1-MeV He⁺ channeling have been used to study the lattice location of ion-implanted Bi in Si. Single-alignment 〈110〉 and 〈111〉 angular distributions for He scattering from both the Si and Bi atoms at the same depth were measured as a function of implant conditions at 296 and 80 K. Double-alignment angular distributions were also measured for uniaxial and 90° biaxial channeling along 〈110〉 axes. For both single- and double-alignment measurements, the widths of the Bi distributions show significant narrowing relative to those for Si. Also, the Bi minimum yield is reduced from 16% for 〈110〉 single alignment to 5% for 〈110〉 uniaxial double alignment. Angular-distribution calculations based on the average-potential model were made for single-alignment axial channeling as a function of equilibrium displacement of an atom from a substitutional lattice site. The best agreement with the data is obtained for the case of ≈ 50% of the Bi displaced 0.45 \AA{} from Si lattice sites and the remaining Bi atoms located substitutionally on Si lattice sites.