Defect characterization in diamonds by means of positron annihilation

Positron lifetime measurements on type Ia diamonds have shown that divacancies and larger vacancy clusters (>10 vacancies) have been retained in these stones. Upon irradiation with 3.5 MeV electrons, monovacancies are formed in their neutral state of charge. Some divacancies are also formed. The monovacancies are introduced at a rate of 0.3 cm−1 and no charge transfer involving monovacancies was found at thermal equilibrium up to temperatures …