Transformation of GR1 defects in annealed natural type IIa diamonds

Abstract

A sample of the natural type IIa diamond was pre-irradiated in a nuclear reactor and then annealed under isothermal conditions at 550°C. The experimental data were used to calculate a decrease in concentration of the neutral vacancy defect called GR1, corresponding to a phononless band (PLB) at 741 nm, and an increase in concentration of the derivative defect H3 with PLB at 503.2 nm for a broad range of annealing times (0–300 h) and temperatures (100–900°C). Calculations performed using a single activation energy E _m=2.43 eV for both fast and slow components of the GR1 defect transformation process indicate that the annealing of GR1 and the production of H3 are really observable above 450°C (400°C being the threshold temperature). At 700–900°C, the fast component contributes over the annealing time interval 0.002–0.251 h, after which the annealing of GR1 is determined by the slow component alone.