Nitride layers formed by nitrogen implantation into metals

For nitrogen implantation into several kinds of metals (Al, Ti, V, Fe, Co, Ni, Zr, Nb, Mo, Ta, Hf, W) with a dose up to 2 x 10(18) ions cm(-2), dose dependence of the nitrogen depth profile, retained nitrogen dose and sputtering yield were calculated by Monte Carlo simulation using the dynamic SASAMAL code for the energy rage of 1 keV to 1 MeV. The calculated results were compared with the experimental results obtained by a resonant nuclear reaction analysis using N-15(p, alpha gamma)C-12 reaction. In the simulation, it was assumed that the nitrogen concentration could not exceed that of saturated nitride phase and that the excess nitrogen migrated towards the surface depending on the radiation damage. The depth dependence of the chemical state measured by XPS and the crystalline structure of the surface layer obtained by a glancing angle XRD are also presented for Zr implanted with 50 keV nitrogen at room temperature and at high temperature or with post implantation annealing. The depth dependence of microhardness was also measured by an ultra-micro indentation tester. In order to find the method to overcome the limited thickness and the severe radiation damage problem at high dose implantation necessary for the saturation, the nitrogen depth profiles for an energy scanning implantation with a uniform and a non-uniform energy distribution were calculated and compared with those of monoenergetic implantation. (C) 1998 Elsevier Science S.A. All rights reserved.