Annealing behaviours of defects in electron-irradiated diamond probed by positron annihilation

Annealing behaviours of defects in electron-irradiated diamond were studied using the positron annihilation technique. For a type IIa specimen after 3 MeV electron irradiation with a dose of 1 x 10(18) cm(-2), the major species of vacancy-type defects was determined to be neutral monovacancies, V-0. The trapping rate of positrons by V-0 decreased above 600 degrees C annealing, but the annihilation mode of positrons trapped by vacancy-type defects was observed even after 900 degrees C annealing. For a type Ib specimen after the irradiation, the major species of vacancy-type defects was determined to be negative monovacancies, and the formation of nitrogen-monovacancy pairs, N-V, was observed after 650 degrees C annealing. The annihilation probability between positrons and electrons with a broad momentum distribution was found to be increased by the trapping of positrons by N-V.