The near-surface regions of high-purity fused silica disks (Corning 7940) were modified by implantation with 160keV Bi2+ ions, at room temperature, to a nominal dose of 6 x 1016/cm2 at about 5A/cm2. The specimens were then annealed in oxidizing or inert atmospheres, at temperatures ranging from 500 to 1100C. The doses which were retained before and after annealing were deduced by means of Rutherford back-scattering. A broad optical absorption band was detected at about 5eV (248nm) and was attributed to surface plasmon resonance from colloidal Bi particles that precipitated after implantation, and could be observed by using transmission electron microscopy. After annealing in O for 1h at temperatures above 1000C, the Bi content decreased by about 70%. Annealing in an oxidizing atmosphere oxidized the precipitates, and changed the optical absorption of the samples. When samples were annealed in Ar, a relatively small decrease in the retained dose (about 12%) was observed for annealing temperatures above 1000C. The differences in the effects of annealing in O and Ar suggested that Bi atoms in samples that were annealed in Ar were not oxidized, and remained in the particles. Small changes in the distribution of Bi after annealing in Ar were attributed to the diffusion of Bi atoms from colloidal particles to larger particles (Ostwald ripening) and to evaporation from the surface of the fused silica.

S.Y.Park, R.A.Weeks, R.A.Zuhr: Journal of Applied Physics, 1995, 77[12], 6100-7