Dynamic behavior of implanted nitrogen in zirconium at various stages of implantations

Abstract

Abstract Depth profiles of nitrogen implanted into Zr with an energy of 50 keV were calculated by dynamic SASAMAL code with three different assumptions for the diffusion of excess atoms over stoichiometry, i.e., ‘no diffusion', ‘both-sides-diffusion’ and ‘upward-diffusion'. To distinguish nitrogens implanted certain stage of implantations, alternate implantations of 15N and 14N were used. The results were compared with the experimental results by the resonance nuclear reaction analysis, NRA. For 15N implantation with fluences from 1 × 1017 to 1 × 1018 ions/cm2, the calculated results with ‘upward-diffusion’ agreed very well with the NRA results for all fluences. For the depth profile of pre-implanted 15N (1 × 1017 ions/cm2), which was changed by the subsequent 14N implantation with fluences of 1 ∼ 10 × 1017 ions/cm2, the agreement with the NRA results was satisfactory until the 14N fluence did not exceed 5 × 1017 ions/cm2, but for higher fluences, the retained probabilities of 15N obtained by the ‘upward-diffusion’ code were too low compared with the experimental value obtained by NRA. For the depth profiles of 15N (1 × 1017 ions/cm2) implanted following after implantations of 14N with fluences of 1 ∼ 10 × 1017 ions/cm2, the agreement with the NRA results was quite good for all 14N fluences. It is concluded that the approximation of ‘upward-diffution’ is proper satisfactorily for the treatment of atoms implanted at the final stage of implantations, but a problem is left for the treatment of atoms implanted at the early stage of implantations.