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We study the ion-irradiation-induced deformation of free-standing ultrathin Si wafers with a thickness of 8 [Formula: see text]m. The time-response spectrum of the deformation was measured using a laser displacement meter with a time resolution of 1 ms. The results showed that the deformation appeared during irradiation and disappeared after irradiation. The deformation was composed of a fast deformation with a millisecond time constant and a slow deformation with a second time constant. We performed a model calculation to identify the deformation mechanisms. We found that the fast deformation originated from expansion or shrinkage of crystal lattice caused by beam heating and deduced that the slow deformation resulted from the topological defect formation in Si crystals. The relaxation time of the slow deformation is related to the coordination number of disappeared topological defects. In this experiment, we conclude that the deformation of Si crystals maintains reversible behavior in the formation of topological defects up to the coordination number 5.

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.

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.