EPR of silica and fluoride glasses implanted with titanium and zirconium

Abstract

Abstract Silica substrates were implanted with Ti+ ions to nominal doses (D) ranging from 5×1016 to 6×1017 ions/cm2 at an energy of E=160 keV. The lines of electron paramagnetic resonance (EPR) with g=1.938 to 1.944 are attributed to Ti3+ with ground state |xy〉 located in tetragonally compressed oxygen octahedron. Computed spectra of some samples implanted with Ti, besides the line at g=1.94, contain two isotropic lines with (g=1.968 and g=1.972) which are assigned to Ti3+ ions entering clusters or compounds of titanium with silicon or oxygen. The greater fraction of implanted Ti exists in non-paramagnetic states. In silica glass implanted with Zr+ (E=195 keV, D=5×1016 and 1017 ions/cm2) Zr3+ ions in the amount of 0.5–1% of implanted Zr are in distorted octahedral environment producing an asymmetric line with g∼1.916 and width ∼14 mT. For fluoroaluminate glass (FAG) implanted with Ti+ (E=150 keV, D=2×1016,5×1016 and 10 17 cm −2 ) EPR line at g=1.944 and optical absorption band at ∼475 nm similar to those observed earlier for FAG doped with TiO2 were assigned to Ti3+ ions in tetragonally compressed octahedron. In the EPR spectra of FAG coimplanted with Ti+ (E=150 keV) and F+ (E=90 keV) the triplet centered at g=1.9375 with ratio of intensities of components equal to 1:2:1 and the separation between adjacent components equal to 1.1 mT was observed and attributed to TiF+2 molecular ions. The integrated intensity of this triplet in relation to that of the g∼1.94 single line varies from 0.6% to 2% depending on F+ dose. The decrease in the content of Ti3+ ions with increasing implantation dose is interpreted in terms of chemical sputtering of Ti–F molecules. The g-values of Zr3+ ions incorporated into fluorozirconate glass (FZG) after the implantation of Zr+ ions differ from those obtained earlier for F-center near Zr4+ in X- or γ-ray irradiated FZG. We conclude that some part of the implanted zirconium is incorporated into FZG as Zr3+ in distorted octahedral environment. Structural defects produced in silica and fluoride glasses by Ti+- and Zr+-ion implantation are not discussed.