An infra-red spectroscopic study was made of neutron-irradiated Czochralski-grown material and, in particular, of the evolution of the well-known 828/cm band of the A-center during isochronal annealing between room temperature and 700C. The strength of the VO band began to increase above about 200C, continued gradually up to 300C (stage-I), and then began to decrease up to about 400C (stage-II). It then stabilized up to about 550C (stage-III). Upon re-irradiating under the same conditions, and repeating the annealing process, the increase in the VO signal in stage-I disappeared. This was attributed to the existence of defect aggregates, labelled as Xi centers, which were related to impurity-defect clusters that competed with Oi in capturing vacancies. The presence of Xi centers was related to the thermal annealing. A comparison of the evolution of VO (828/cm) and VO2 (887/cm) bands, in irradiated and re-irradiated materials during stage-II, was made and the results were explained in terms of known reaction behaviors. The stabilization of the 828/cm line in stage-III was attributed to a fraction of the A-centers, in neutron-irradiated material, which acquired a greater thermal stability by relaxing in the vicinity of larger defects.

Infra-red studies of defects formed during post-irradiation anneals of Czochralski silicon C.A.Londos, N.V.Sarlis, L.G.Fytros: Journal of Applied Physics, 1998, 84[7], 3569-73