It was recalled that it had been reported that higher densities of vacancies were formed during the electron irradiation of type-IaA diamonds than of high-purity type-IIa diamonds, and that a fraction of these vacancies decayed slower than the remainder during annealing. The experimentally observed double-decay equation was deduced here from basic physical postulates. It was assumed that the strain fields, which surrounded the A-centers, attracted vacancies towards these defects and repelled interstitial atoms. This reduced the correlated recombinations that would have occurred in the absence of such forces, and thus caused an increase in vacancy density. These forces were modelled in terms of so-called capture-volumes which surrounded the A-centers. Once within such a volume, a vacancy could not escape and finally arrived at the A-center. The increase in the fast fraction with annealing temperature, which had been attributed to up-hill diffusion, was modelled in terms of smaller so-called catch-volumes that also surrounded the A-centers. When a vacancy entered the latter, it combined with the A-center to form an H3-center, and this required the scaling of a larger activation barrier than in the case of vacancy diffusion. Previously published experimental results were well-explained for capture-volumes which (when added together) occupied less than 10% of the total volume of the diamond, and for an initial fraction (greater than 90%) of vacancies within them. This implied that, outside of these volumes, the density of vacancies was far lower than it would have been in a pure diamond that did not contain A-centers. It was therefore suggested that the interstitial atoms which formed within the volumes were, at some stage, ejected from these volumes by strain-assisted diffusion. This increase, in the density of interstitials outside of the volumes, enhanced vacancy annihilation when the annealing temperature at which these interactions occurred was reached.

Vacancy Diffusion and Trapping in Electron-Irradiated Type-IaA Diamonds. J.F.Prins: Diamond and Related Materials, 2001, 10[1], 87-93