CHEMICAL INTERACTIONS IN TITANIUM-IMPLANTED AND TUNGSTEN-IMPLANTED FUSED-SILICA

Silica glasses were implanted with titanium at energies of 30 and 190 keV at a dose of 5 x 10(16) CM-2 and with tungsten at 200 keV and dose of 1.6 x 10(16) CM-2 and 5 x 10(16) CM-2 . A set of titanium- and tungsten-implanted samples was also subsequently implanted with nitrogen in the energy range of 15-100 keV and dose of 2 x 10(17) 17 CM-2. Samples were characterized by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, Rutherford backscattering spectrometry, nuclear reaction analysis and, partially, IR-diffuse reflectance. Titanium silicide and titanium oxide compounds were observed in titanium-implanted samples. Subsequent nitrogen implantation destroys the titanium silicide species, inducing the formation of titanium metallic clusters and substoichiometric silicon nitrides: titanium oxides are transformed to titanium oxynitrides. Tungsten implantation causes the formation of metallic tungsten precipitates and the presence of tungsten oxides was observed. Nitrogen implantation favours the formation of tungsten oxynitrides. Thermodynamic considerations were applied to explain the chemical interactions between implanted species and substrate.