Rutile formation and oxygen diffusion in oxygen PIII-treated titanium

Using oxygen plasma immersion ion implantation (PIII) into pure titanium with 30-kV pulses at different temperatures between 265 and 550 degreesC, pure, stoichiometric rutile without oxygen vacancies was obtained with Raman spectroscopy. Ion beam analysis - elastic recoil detection analysis (ERDA) and Rutherford backscattering spectroscopy (RBS) - was employed to determine the oxygen depth profiles. A thermally activated growth of this stoichiometric rutile layer is observed with a sharp interface to the bulk titanium. No broadening of the interface beyond 15-20 nm, the depth resolution of the profiling methods, accompanies this process. In contrast, at temperatures above 400 degreesC a deep tail of oxygen diffusing into the titanium is found, reaching more than 0.5 mum within 1 h. This oxygen depth distribution can be described by a complementary error function. Again, the diffusion constant and the activation energy were derived from the measurements. For the second process a higher activation energy of 0.85 eV, compared with 0.5-0.6 eV for the bulk growth of TiO2 is found. (C) 2001 Elsevier Science B.V. All rights reserved.