Lattice location ofB12in germanium and silicon at 300 K

Polarized ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ was produced in the reaction ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}(d,p){}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ and recoil implanted in single-crystal wafers of Ge and Si. Resonance depolarization spectra taken in the presence of an externally applied field gave linewidths in good agreement with the values expected from second-moment calculations for ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ occupying a substitutional crystallographic site. The measured polarization of ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ was considerably lower than that for several fcc metals. This was attributed to some of the boron occupying a low-symmetry nonsubstitutional site. With this interpretation the substitutional fraction of ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ in Ge = 0.42 ± 0.04 and in Si = 0.67 ± 0.06.