Abstract
A chemically durable glass containing a large amount of phosphorus is useful for in situ irradiation of cancers. It can be activated to β-emitter with 14.3d half-life by neutron bombardment. Microspheres of the activated glass injected to the tumors can irradiate β-ray directly to the tumors without giving radiation to neighboring normal tissues. In order to examine possibility for obtaining such a glass by ion implantation, P+ ion was implanted into a pure silica glass in a plate form under 50keV to different doses. This implantation energy is estimated to give the maximum concentration of P+ ion at 48.6nm in depth from the surface. Structural damage was produced near the surface of the glass by the ion implantation for all the doses in the range from 5×1016 to 1×1018cm-2. The phosphorus was localized only in the regions deeper than 1.2nm from the surface, taking a form of phosphorus colloids, for a dose of 5×1016cm-2, whereas it was distributed up to the glass surface and a part of it near the surface was oxidized for doses above 1×1017cm-2. The former glass little released both P and Si into water at 95°C even after 7d, whereas the latter glasses released appreciable amounts of these elements. At implantation energy of 20keV, even a dose of 5×1016cm-2 formed an oxidized phosphorus at the glass surface and gave appreciable releases of P and Si from the glass into water. This indicates that a chemically durable glass containing a larger amount of phosphorus could be obtained if P+ ion is implanted at higher energies and localized in a deeper region, even if the surface structure of the glass is damaged by the ion implantation.
