Oxygen and hydrogen profiles in metal surfaces following plasma immersion ion implantation of helium

Helium ion implantation into metals can be used to form nanoscale cavities in high concentration in the surface. These cavity structures have unique features which offer potential for applications such as catalysis. Most previous studies have used ion accelerators to carry out the helium implantations. Here helium implantation using pulsed plasma immersion ion implantation (PI3 TM) is investigated. Previously we have reported results for PI3 implantations of 40-keV helium, and 20-keV oxygen, into Ti metal and two Ti alloys (including Ti–6Al–4V). Here we extend this work and examine in detail the depth profiles, determined by HERDA, of helium, hydrogen and oxygen in these metals following implantations of helium only, at several helium dose levels and two helium energies. It is found that the profiles for casual hydrogen and oxygen are strongly influenced by the depth profile and fluence of the implanted helium. The effect on the profiles of subsequent PI3 oxygen implantation is also reported.