Ion implantation effects in glasses

Ion implantation can be used to introduce network damage and to alter the chemical composition in glasses. Structural changes can be inferred from IR measurements near 1000 cm-1 and by optical absorption near 2150 A. Implantation-induced damage decreases the implanted volume in fused silica with consequent changes in the refractive index, the near-surface hardness, and the tensile surface stress. Prior work in these areas is reviewed. Implantation into alkali silicate glasses depletes the alkali content in the implanted region. These changes allow preferential surface crystallization in Li2O.2SiO2 glasses. Crystallization of amorphous SiO2 can be induced by implantation of Li. Insight into the crystallization process is obtained by following the associated ion movement by elastic recoil detection and optical techniques. Implantation of 20 keV H shows that saturation of implanted H-sites in fused silica occurs at about 2.2 x 1021 H/cm3 in agreement with free volume estimates of the maximum number of available interstitial sites. Details of H and D interactions in fused silica were studied as a function of fluence and temperature. Results are of interest in studies of corrosion in glasses considered for nuclear waste encapsulation and for components in fusion reactors. (author)