Positron annihilation studies of γ-irradiated type Ib and IIa diamonds

Cobalt-60 gamma irradiation readily created vacancy-type defects in type Ib diamond whereas none were found in type Ha. The defect is characterized by a positron lifetime of 130 ps and a main annealing stage centered at 270 degreesC. The vacancy is not a free vacancy, and is suggested to be a vacancy-self-interstitial complex. None of the optical absorption features in the experimentally accessible wavelength range of 400-1100 rum could be correlated with the positron data. Statement of novelty. Gamma irradiations of type Ib diamond is shown to produce a vacancy-interstitial complex observable by positron lifetime spectroscopy, and with characteristics very different from those of the isolated monovacancy. (C) 2004 Elsevier B.V. All rights reserved.