The defect accumulation and irradiation-induced lattice strain in Si at high-dose neutron irradiation

The accumulation of structural defects in neutron-irradiated silicon with different impurity contents is studied by the method of IR spectroscopy. It is shown that the annihilation of vacancies and interstitial silicon atoms on oxygen is essential in the accumulation of radiation defects during this kind of irradiation. Vacancy-oxygen complexes are preferably formed near the disorder regions (DR). This may be explained on the basis of concepts of radiation-accelerated diffusion of oxygen to the DR. The nature of elastic stresses in DR containing silicon crystals at different stages of irradiation is discussed. The estimations of elastic stresses made on the basis of data of optical measurements give ≈ 10⁴ to 10⁵ N/cm². It is shown that the quantities of one-phonon and near-edge absorption are determined by the available gradients of distribution of defects arising during the neutron irradiation.