Determination of the he pressure in bubbles formed during α-implantation of Ni

Abstract

At T−90°C, Ni single crystals were uniformly implanted to a depth of 10 μm with multi-energy He ions (E≤5.2 MeV), to concentrations from 0.06 to 1.1 at.%. From a small-angle X-ray scattering study, helium was found to be trapped in small bubbles with radii of 5.6 to 12 Å. The average distance between bubbles of about 80 Å was found to be independent of the implantation dose. At the higher concentration, CH_c 1.1%, the bubbles were found to be strongly over-pressurized, i.e. the He pressure in the larger bubbles was determined to be as high as 300 kbar with a He atom/vacancy ratio of 2.