Ion beam analysis of nanoporous surfaces produced by He-implantation and oxidised by plasma-immersion ion-implantation

Helium ion implantation into metals can lead to ordered bubble structures that develop into nanoporous cavity structures at high dose levels. Such cavity structures, and the oxides that can be formed on them, have been investigated previously for materials implanted using ion accelerators. These materials have unique features that offer potential for applications. Here, we investigate pulsed plasma-immersion ion-implantation (PI³ ) as a means of forming nanoporous oxide surfaces on a larger scale. 40 keV helium, and 20 keV oxygen, is implanted into Ti metal and two Ti alloys (including Ti-6Al-4V), and NRA, RBS, HERDA, TEM and Raman spectroscopy are used to characterise the resulting cavity structure and surface oxides. He implantation at a temperature of 160 degrees Celsius produces cavities approx. 2 nm across, in close-packed, apparently random structures. Oxygen implantation into substrates that are not pre-implanted with He, causes significant formation of TiO2 (rutile). Pre-implantation with He causes an increase in the amount of oxide and in the proportion of oxide that is amorphous

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