DEPTH PROFILE OF NITROGEN CONCENTRATION AND NANO-HARDNESS IN NITROGEN-IMPLANTED ZR AT RT AND AT 600 DEGREES-C

To study the property changes of Zr induced by high dose nitrogen impl antation at RT and at 600 degrees C, the depth profiles of nanohardnes s were measured and compared with those of nitrogen concentration and chemical states of nitride phase. The implantation was performed with 100 keV N-2(+) ions and doses from 1 x 10(16) to 1 x 10(18) N/cm(2). T he nanohardness was measured by an ultra micro indentation tester. The nitrogen depth profile was measured by NRA using N-15(alpha, gamma)C- 12 reaction and RBS, Depth dependence of chemical state was measured b y XPS combined with Ar sputtering. Dose and temperature dependence of the crystalline structure were measured by glancing angle XRD. There w as no difference in the XPS spectra between RT and 600 degrees C, and the spectra indicated that ZrN was formed at the depth where nitrogen existed. Since the heat of formation of ZrN is rather high, the depth profile of the implanted nitrogen in Zr was hardly changed up to 600 d egrees C. But the XRD patterns showed the increase of crystalline nitr ide phase with the increase of implantation and annealing temperatures . From the dose and temperature dependence of nanohardness profile, th e hardness increase by low dose implantation around 1 x 10(17) ions/cm (2) at both RT and 600 degrees C is attributed to point defects and in terstitial hardening and the increase by high dose implantation above a dose around 5 x 10'7 ions/cm(2) at 600 degrees C is attributed to th e formation of ZrN phase. (C) 1998 Elsevier Science S.A.