Implantation profiles of low-energy helium in niobium and the blistering mechanism

The depth profiles of 1.5–15-keV 3He ions implanted into a Nb single crystal at doses of 5×1016–7×1018/cm2 have been measured using the 3He (d,p) 4He reaction. A comparison of the results with theoretical predictions for the range and the damage distribution of 3He in amorphous material shows reasonable agreement. Furthermore, the Deckeldicke (i.e., thickness of the covers of the blisters) was determined by Rutherford backscattering in double alignment. The results indicate that stress release rather than explosion of gas bubbles is the dominant mechanism in blister formation.