Observation of boron bound excitons in boron-implanted and annealed natural IIa diamonds

Cathodoluminescence at 77 K was used to study the optical properties of ion-implanted and annealed natural type IIa diamonds. The substrates were implanted at room temperature with C12+, B11+, P3+, and As75+ -ions with energies of up to 350 keV and doses of up to 13×1013cm−2. After annealing at 1200 °C, the cathodoluminescence spectra show a number of transitions which are induced by the radiation damage independent of the implanted ion species. Only in the BHe3implanted samples are there two transitions related to the implanted ion species: the 4.5 eV band and the boron bound exciton. The appearance of the bound exciton spectrum demonstrates the presence of isolated boron on substitutional lattice sites implying electrical acceptor activity. Our annealing studies indicate a minimum annealing temperature of 1000 ° for the activation of the implanted boron atoms onto the acceptor states.