Diamonds containing N in different forms were irradiated by 3MeV electrons or 60Co γ photons and characterized by optical absorption and electron spin resonance. An unusually low production rate of vacancies, V, and interstitials, I, was observed in γ-irradiated Ib-type diamonds (those containing isolated N) and pure IIa-type diamonds as compared to Ia diamonds (containing N clusters). Post-irradiation annealing at above 300C strongly increased the V and I concentrations in Ib diamond, but not in IIa diamond. These results were explained as γ-irradiation of diamond predominantly produced V–I complexes instead of individual V and I defects. Strong effect of charge state on V–I recombination was revealed: In Ib diamond, V–I complexes were negatively charged and dissociate upon annealing. On the contrary, V–I pairs were neutral in IIa diamond, and they annihilated during irradiation. The optical absorption, electron spin resonance, and positron annihilation signatures of the V––I pairs were identified.

Evidence for Vacancy-Interstitial Pairs in Ib-Type Diamond. K.Iakoubovskii, S.Dannefaer, A.Stesmans: Physical Review B, 2005, 71[23], 233201 (4pp)