Importance of Implantation Sequence in the Formation of Nanometer Size Colloid Particles Embedded in Amorphous Si${\mathrm{O}}_2$: Formation of Composite Colloids with Cu Core and a ${\mathrm{Cu}}_2$O Shell by Coimplantation of Cu and F

A striking difference in the properties of nanosized colloid particles between amorphous Si${\mathrm{O}}_2$ substrates implanted with Cu and F ions in a differing sequence is reported. No significant change in an optical band peaking at 2.2 eV due to plasma oscillation of Cu nanosize colloids is observed by implanting F and then Cu. The 2.2 eV band is not perceived with implantation of F ions into Cu-implanted substrates. Although colloid particles identified are Cu in the former sequence, those formed in the latter have a dual structure composed of Cu (core) and ${\mathrm{Cu}}_2$O (shell). This is explained by oxidation of the outer part of Cu colloids by energetic O recoiled from the silica structure by implanted F.