Lattice site location of clustered boron atoms in silicon

Si crystals were doped with 11B by ion implantation followed by ruby laser annealing. Displacement of B atoms from lattice sites was induced by proton irradiation at 35 K, followed by thermal annealing at 300 K. The resultant defect configuration was studied by ion channeling. Angular scans for Si and B were measured through several major axes, for irradiated samples, before and after the anneal, using RBS and the 11B(p, α)8Be reaction at Ep = 0.7 MeV. The experiments were compared with simulated scans, calculated with the use of both Monte Carlo and analytical methods, for a variety of assumed lattice sites. The results show that the fraction of displaced B atoms increases from ≈ 15% to ≈ 40% by the annealing process. The lattice site of these B atoms may either be a position displaced by 0.85 Å along the 〈110〉 direction, or 0.9 Å along the 〈100〉 direction, or a combination of positions, such as a fraction shifted in the 〈100〉 direction and a fraction at the bond center position. Despite considerable differences in the shape of channeling profiles predicted by the two models used, the results regarding the lattice position of the B atoms are consistent