Defects insynthesized and natural diamond probed by positron annihilation

Abstract

Defects in synthesized and natural diamond were studied using the positron annihilation technique. For a synthesized type IIa specimen, the lifetime of positrons annihilating from the free state was determined to be 98.7 ps. For a synthesized type Ib specimen, the effects of the annihilation of positrons trapped by open spaces introduced by substitutional nitrogen atoms on the positron parameters were discussed. After electron irradiation, the species of the major vacancy-type defects was identified to be a neutral and/or negatively charged monovacancy. For natural type IIa and IIb specimens, the annihilation mode of positrons trapped by vacancy clusters was observed. For the natural type IIb specimen, the temperature dependence of the trapping rate of the vacancy clusters was explained assuming that these clusters act as compensators for acceptor impurities (boron).