Defects in synthetic and natural samples were studied by using positron annihilation techniques. In synthetic type-IIa specimens, the lifetime of positrons which annihilated from the free state was deduced to be 98.7ps. In synthetic type-Ib specimens, the effects of the annihilation of positrons which were trapped by the open spaces that were introduced by substitutional N atoms were considered. After electron irradiation, the major vacancy-type defects were found to be neutral and/or negatively charged monovacancies. In natural type-IIa and type-IIb specimens, the annihilation of positrons which were trapped by vacancy clusters was observed. In natural type-IIb specimens, the temperature dependence of the trapping rate of vacancy clusters was explained by assuming that these clusters acted as compensators for acceptor impurities such as B.

Defects in Synthesized and Natural Diamond Probed by Positron Annihilation. A.Uedono, S.Fujii, N.Morishita, H.Itoh, S.Tanigawa, S.Shikata: Journal of Physics - Condensed Matter, 1999, 11[20], 4109-22