Oxygen related defect center formation in MeV energy boron implanted silica

Silica samples were implanted with 1.6 and 4 MeV B2+ at nominal doses rangi ng from 0.5 to 5.0x10(15) ions/cm(2). Sample temperatures during implantati on were either 100, 300 or 673 K. Optical absorption was measured from 2.7 to 6.5 eV and in all spectra two maxima were resolved at 5.0 and 5.8 eV. Ba sed on the literature we assumed bands at 4.8, 5.01, 5.17, 5.88, and 7.15 e V comprised the observed spectra. Assuming that the shapes of these bands w ere Gaussian functions, the data was fitted by allowing the maximum amplitu de to be a free parameter. The fit between 2.5 and 5.5 eV was within +/-3%. At larger energies the fit was worse. Assuming that there was a band at 6. 35 eV reduced the difference between the fit and the data to <+/-2% from 2. 5 to 6.5 eV. The same accuracy of fit was achieved with all spectra, irresp ective of energies, doses or sample temperatures. Each of the bands had a d ifferent dependence on dose, on energy, and on sample temperature. A band a t 5.5 eV which has been observed in the spectra of some silicas when irradi ated and photons of differing energies was not required for the fitting. Th is band is absent from the spectra of as implanted B samples. (C) 1999 Else vier Science B.V. All rights reserved.