The precipitation of O was studied at temperatures of between 500 and 600C by using infra-red absorption measurements of the 0.0195mm band. The data were fitted to Ham's theoretical models for the diffusion-limited growth of randomly distributed particles. Values of the equilibrium O concentration, Cs, were obtained directly. Assuming the usual diffusion coefficient for interstitial O, the number density of the precipitates and their spherical radii were determined. These results were linked to previous data obtained at higher and lower temperatures, and yielded a self-consistent model. It was found that the value of Cs decreased to 8 x 1015 at 650C, but then increased again to 2 x 1017/cm3 at 450C. This previously unreported behavior was attributed to the importance of the surface energy to very small agglomerates. The results implied that, if the thermal donors and coesite precipitates which were observed at low temperatures arose from O aggregation, they could not form unless an O complex, such as a di-oxygen species, had a much larger diffusion coefficient than an isolated interstitial O atom.

S.Messoloras, R.C.Newman, R.J.Stewart, J.H.Tucker: Semiconductor Science and Technology, 1987, 2[1], 14-9