Four-vacancy damage clusters in neutron-irradiated silicon

Abstract

The production of vacancy clusters in neutron-damaged n-type float zone silicon was investigated using electron paramagnetic resonance (EPR). The irradiation conditions in the reactor channel provided different doses of fast neutrons, Φ N , whereas the thermal neutron dose was kept constant for all the samples studied. The four-vacancy cluster (P3) was found to be the dominant defect centre identified in the EPR spectrum. It was shown that its concentration increased almost linearly with Φ N within the range studied, indicating that these defects are formed in the primary cascades induced by fast neutrons. it is estimated that approximately two P3 centres are produced per primary cascade, irrespective of the fast neutron dose. This suggests that these defects are mainly associated with the displacement spikes which terminate the cascades. Generation of P3 centres was found to depend only on the fast neutron dose and to be quite independent of the fast neutron spectra.