A new technique for the measurement of implanted He profiles in nickel

A new technique of measuring the range of helium ions implanted at low concentrations into nickel is described. The residual amount of helium in a foil is measured by a combination of gas release and selective vibro-polishing. The method, illustrated by the results of some preliminary experiments, is sufficiently sensitive to enable the range, to be measured with peak implanted gas concentrations of the order of 10−7atoms per nickel atom (i.e. a sensitivity limit of 10−8 atom/atom) where bubble formation is unlikely. The mean projected range of 100 keV helium ions in nickel was found to be 2800 Å, together with a second peak at 5250 Å which is thought to be due to channelling. A significant fraction of the helium diffused interstitially to depths greater than 1 μm.