Uptake of light elements of nanoporous layers formed by helium ion implantation

Nanoporous cavity structures can be formed in surfaces by He ion implantation. In modifying materials by diffusing desired dopant atoms into the nanoporous structures, several complicating factors arise. To clarify these factors we have used pulsed plasma-immersion ion-implantation (PI3TM) and accelerator implantation techniques with Ti, Mo, Co and Si as targets. When studying the uptake of light elements in nanoporous layers it is necessary to consider the effects from the casual loading of O, C and N into the structures from the laboratory environment. The results suggest that significant ingress of O and N from the atmosphere can take place at ambient temperature especially for the more chemically active substrate Ti. Helium ion implantation to high fluence enhances the formation of oxide at the surface of Co, in a buried layer below the surface in Mo, and throughout the depth of the He implantation in Ti