It was reported that larger densities of vacancies were formed during electron irradiation of type IaA diamonds than in the case of high-purity type IIa diamonds, and that a fraction of these vacancies decays slower than the rest during annealing. In this paper the latter, experimentally observed, double-decay equation was derived from basic physical postulates. It was assumed that the strain fields, surrounding the A-centers, attracted vacancies towards these defects and repelled interstitial atoms; in this way reducing the correlated recombinations that would have occurred without such forces being present, and thus causing an increase in vacancy density. These forces were modelled in terms of 'capture-volumes' V surrounding the A-centers. Once within such a volume, a vacancy could not escape and had to end up finally at the A-center. The increase in the fast fraction with annealing temperature that had been ascribed to 'uphill' diffusion was modelled in terms of smaller 'catch-volumes' that also surrounded the A-centers. Once a vacancy entered the latter, it combined with the A-center to form an H3-center, and this process required the scaling of a larger activation barrier than in the case of vacancy diffusion. The previously published experimental results were well modelled for capture-volumes V that, when added together, occupied less than 10% of the total volume of the diamond, and for an initial fraction of vacancies larger than 90% within them. This meant that outside of these volumes the density of vacancies was far less than would were the case in a pure diamond that did not contain A-centers. It was therefore postulated that the interstitial atoms that formed within the volumes V were, at some stage, ejected from these volumes by strain-assisted diffusion. This increase in density of the interstitials outside of the volumes, enhanced vacancy annihilation when the annealing temperature was reached at which these interactions occurred.

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