Ion Implantation of Boron in Diamond

It has been a challenge to inject dopant atoms onto diamond lattice sites by ion implantation, because of the complications of ion damage and defect clustering during annealing. We re-investigated this topic by implanting boron ions into an insulating natural diamond ( type II-A ) which was pre-damaged by carbon ion implantation. Both of the implantations were performed at liquid nitrogen temperature. The amount of pre-damage was adjusted to produce enough vacancies and interstitials in diamond to promote boron substitutionality during subsequent annealing. Samples were characterized by optical absorption and electrical measurements. It was found that optical absorption of the implanted samples strongly depends on the post implant annealing sequence. The activation energies obtained from electrical measurements match very closely to those due to boron atoms in natural p-type diamonds. Photoconductivity measurements showed that the fraction of remaining electrically active radiation defects in the implanted and annealed samples depends on the relative fluences of boron and carbon.