Investigation of ion-implanted boron in diamond

The fraction of boron atoms that take up defect-free sites on ion implantation in diamond has been investigated in beta-NMR measurements. Polarized B-12 nuclei were produced in the reaction B-11(d,p)B-12 with 1.5 MeV deuterons and recoil implanted into a diamond Ib sample. Depolarization resonance spectra were measured in an external magnetic field of 1.0 kG at sample temperatures ranging from 300 K to 800 K, showing that the polarised B-12 atoms retain their polarisation on implantation in diamond. The polarization asymmetry at the Larmor frequency yielded a fraction of boron atoms at defect-free tetrahedrally symmetric sites of 12(1)% at 300 K, increasing to 17(2)% at 800 K. The resonance spectra also showed evidence that some of the implanted boron atoms were at low symmetry sites. Measurements after pre-implantation of the diamond sample with 50 - 220 keV Li+ ions showed no significant change of the fraction of boron atoms that are implanted at defect-free symmetric sites in the diamond lattice.