Formation of aggregated defects in metals by ion bombardment

The formation process of defect clusters in Ni due to the irradiation by H+, D+ and He+ ions was investigated at the relatively low fluence. Especially, the role of gas atoms in this process was discussed. The experimental procedure and the results of 20 keV D+ irradiation, 25 keV He+ irradiation, 1.8 MeV He+ irradiation and 1.5 MeV H+ irradiation are reported. The feature of the radiation damage by gas ions was the cascade damage associated with the introduction of gas atoms and point defects at the same time with a strong depth dependence. The depth distribution of defect clusters at room temperature, 310 deg C and 400 deg C fairly agreed with the calculated damage and gas atom distribution. Another interesting feature of 25 keV He+ irradiation was that the volume number density of clusters at the fluence of about 1014 ions/cm2 had little temperature dependence. The number density of clusters in the D+ irradiation was much smaller than that in the He+ irradiation, and strongly depended on irradiation temperature. (Kako, I.)