Effect of beam flux on radiation damage accumulation in ion-bombarded Si

The effects of ion flux on radiation defect production are studied for single crystal silicon bombarded by 6.7 MeV carbon ions. The resultant damage was characterized by X-ray diffraction analysis and positron annihilation Doppler broadening spectroscopy. The results showed that lattice shrinkage occurs after irradiation although the amount of shrinkage decreases with increasing flux at a fixed fluence. This implies that defect concentration is decreased at higher flux. The major defect is identified as a divacancy. To evaluate this flux effect, we consider the flux dependence of defect recombination by defect reaction rate theory. The calculation suggests that the experimental results can be explained by considering the flux effect on the defect recombination process except thermal annealing. This suggests that the reaction rate constant varies by ion flux i.e., the rate of displacements per atom.