Effects of MeV energy titanium ion implants on the oxygen related defects centers in silica

Silica samples were implanted with 4 MeV Ti²⁺ ions at nominal doses ranging from 0.1 to 5.0×10¹⁵ cm^-2. Optical absorption was measured from 3.5 to 6.5 eV and in all spectra a local maximum at 5.0 eV and a shoulder at 5.9 eV were observed. A second series of samples was implanted with 4 MeV Si²⁺ ions at nominal doses ranging from 0.5 to 3.0×10¹⁵ cm^-2. Based on the literature we assumed that Gaussian bands at 4.8, 5.01, 5.17, 5.88, and 7.15 eV comprised the observed spectra. Using Gaussian functions as basis states, linear fits to the data were performed yielding amplitudes for each band. Between 3.5 and 5.5 eV the fits were within ±3%. At larger energies the fits were unsatisfactory. Non-linear fits with an additional, fully adjustable Gaussian function yielded a band at 6.4 eV with full width at half maximum approximately 0.5 eV and reduced the difference between the fit and the data to <2% over the full range of the measurements.