Nitrogen diffusion in stainless steel at elevated temperatures during low-energy N ion implantation was studied. Stainless steels in the temperature range from room temperature to 600C were irradiated by isotopically mass selected 1keV 15N+ ion beams (less than several 10μA/cm2) in an ultra-high vacuum chamber. The depth profile of implanted N atoms as a function of substrate temperature was investigated by nuclear reaction analysis in order to evaluate the diffusion coefficient and activation energy of N atoms in the stainless steel. The results demonstrated that the N diffusion during irradiation with low current density (less than several 10μA/cm2) N ions was faster than that during a post-annealing process after N ion irradiation at room temperature and was slower than that during higher current density (mA/cm2) N implantation previously reported. The activation energy of the N diffusion here was 1eV, which was comparable to that of the ion irradiation experiment performed using higher current density beams, e.g., mA/cm2, and was lower than that of the post-annealing process.

Nitrogen Diffusion in Stainless Steel during Irradiation with Mass-Selected Low-Energy N+ Ion Beams. N.Tsubouchi, Y.Mokuno, A.Chayahara, Y.Horino: Surface and Coatings Technology, 2005, 196[1-3], 271-4