STRUCTURAL FACTOR CONTROLLING NANASIZE COPPER FORMATION IN DOPED AMORPHOUS SILICA BY ION-IMPLANTATION

Colloid formation of Cu particles by ion implantation was examined in SiO2 glass substrates doped with F, P or Ge ions. Doping of phosphorus strikingly reduced intensities of an optical band peaking at 2.2 eV, which is due to plasma oscillation of nanosized copper colloids, while no or a faint effect was seen for fluorine and germanium-doped substrates. Doping of 1.3 mol% P2O5 reduced the absorption intensities to similar to 1/4 and diameters of Cu-colloid particles to similar to 2/3 compared with those in the P-free substrate. On the other hand, F-doping up to 8 mol% gave no perceptible changes and Ge-doping of 6 mol% resulted in similar to 10% decrease in the absorption intensity. It was considered that the primary factor controlling Cu-colloid formation in the implanted glasses is not the change in the continuity of silica network structure but the change in the strength of solvation of charged states of implanted ions. A close similarity was found between the present conclusions and codoping effects on the cluster formation of rare-earth oxides in silica glasses.