Optical absorption and electron spin resonance measurements were performed on Ia-, Ib-, IaA- and IaB-type diamonds which had been irradiated with 3MeV electrons. Optical absorption revealed that the GR1 system was usually accompanied by an underlying broad background band. The latter was tentatively attributed to strained neutral vacancies(V°). Photochromic changes in the optical absorption suggested that the concentration calibration constants for the V°, H3 and H4 defects should be halved, that the 3H and 5RL centers could be different charge states of a di-interstitial related defect and that the di-interstitial (R1, 3H, 5RL) centers were stable to annealing at up to at least 800C. The generation and annealing of interstitials and vacancies were studied as a function of the N concentration and aggregation state. The results suggested that single substitutional N (NS) efficiently trapped C interstitials, but released them upon annealing at 400C. Defects which were related to N aggregation in IaB diamond also trapped interstitials, but did not release them upon annealing. The C interstitials were not trapped by NS–NS pairs. Instead, an increase in the concentration of NS–NS centers enhanced the production rates of vacancies and interstitials, reduced their annealing temperatures and favored the formation of 3H rather than R1 di-interstitials.

Annealing of Vacancies and Interstitials in Diamond. K.Iakoubovskii, I.Kiflawi, K.Johnston, A.Collins, G.Davies, A.Stesmans: Physica B, 2003, 340-342, 67-75