Annealing of monovacancies in electron and γ-irradiated diamonds

Diamonds were irradiated by either 23 MeV electrons or by Co-60 gamma-rays. In the case of electron irradiation, positron annihilation and optical absorption showed that 30-35% of the monovacancies (positron lifetime of 145 ps) were removed by interstitials between 700 and 1020 K. Above 1020 K, divacancies were formed giving rise to TH 5 optical absorption and a positron lifetime of 185 ps. Above 1120 K, TH5 absorption was replaced by absorption at 507/517 nm, but no change in the positron lifetime was observed. Annealing of the gamma-irradiated type Ib diamonds differed substantially from that for the electron irradiated samples; 60% of the monovacancies where removed between 350 and 525 K. (C) 2001 Elsevier Science B.V. All rights reserved.