Thermal Behaviour of Implanted Nitrogen and Accumulated Hydrogen in Titanium
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Mat. Res. Soc. Symp. Proc. Vol. 504 © 1998 Materials Research Society
EXPERIMENTAL Sample preparation and implantation Commercially available Ti (H impurity 0.3 at.%) was used as sample material. The surface of the samples (thickness 1 mm) was mechanically polished using 3 lam diamond paste in the final polishing step and treated for 10 sec with a mixture of HF and HNO 3 -acids (1:4) to guarantee a near surface region with less H concentration [11]. l 5N-ions were implanted with an 2 15 energy of 150 keV. Ion fluences range from I x 10"7 to 1 x 10'S N-ions/cm and the ion flux amounts to 20pA/cm2 . The samples were mounted on a water-cooled sample holder for room temperature (RT) implantation. Post-annealing experiments (PA) were carried out under high vacuum conditions at 700 'C for one hour. Samples implanted at high temperature (HT) were heated from the back side by a heating wire. The temperature was measured with a thermocouple in contact with the sample holder. The temperature was controlled with an accuracy of ±10 'C. The HT-implantations were carried out in the range of 300 to 700 0 C. During RT- and HTimplantation a total pressure of 6 x 10' mbar was maintained in the implantation chamber. H determination by NRA H in the samples was profiled using the resonant nuclear reaction 'H(I5N, cX,)1 2C at EBr =6.396 MeV [12]. H depth distribution was obtained by measuring the yield of y-rays (E. = 3 5 to 5 MeV) as a function of the ' N ion energy. The emitted `-rays were measured with two 8"x4" NaI(T1) detectors. No alteration of the H distribution caused by the analysing ' 5N-beam was observed. NH 4Cl-standard was used for H calibration. The uncertainty of the measured H concentration is about 5%. Stopping power data were taken from [7,13]. N determination by NRA "5N depth profiles of the implanted Ti were measured using the resonant nuclear reaction "SN(p, c`)12C (Tr~e=129 eV) at a proton energy of 429 keV [14]. The proton beam hit the target surface at normal incidence. The 4.432 MeV y-rays emitted by the excited 12C nucleus were detected with a 6 x 4 inch NaI(T1) scintillation detector. A ' 5N-implanted glassy carbon sample with a known ' 5N-dose served as calibration standard. The N depth profiles were measured by varying the proton energy in steps of 1 keV. The uncertainty of the N concentration values in the samples was estimated to be less than 3%. X-ray diffractometry Phases formed by N implantation in Ti were characterised by GIXD with an equipment using a 0-20 goniometer with an option for grazing incident angle and scintillation counter for peak detection. The radiation used was Cu Ka. The dispersion of the X-ray beam is limited to 0.30 by a diaphragm system and Soller slits. To obtain well-detected interference signals the measurements with a focused Bragg-Brentano configuration and fixed incident angle 0=20 were done with a step scan of 0.02) and a step time of 5s. The penetration depth of the radiation (1/e intensity) ranged up to 380 nm. The peaks were identified with the peak-fitting program
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