EVOLUTION OF PROFILES OF IMPLANTED NITROGEN IN METAL BILAYERS

Samples consisting of bilayers of Ni or Pd on Al or Ti were produced. The top Ni or Pd layers were implanted with N-15(2)+ at fluences up to 1.5 x 10(17) N/cm2 at different temperatures. The concentration depth profiles of N-15 were determined with nuclear reaction analysis (NRA) before and after vacuum annealing. Transient diffusion of N atoms in Ni and Ti was observed during implantation at temperatures > 25-degree s-C. Under suitable conditions some of the N atoms penetrate the inter metallic interface and become trapped in the Ti or Al layer. In this w ay N can be introduced into these metals to concentrations far exceedi ng the solid solubilities, without introducing radiation damage. A mod el is proposed to explain the observed phenomena.