COALESCENCE OF NANOSIZED COPPER COLLOID PARTICLES FORMED IN CU-IMPLANTED SIO2 GLASS BY IMPLANTATION OF FLUORINE IONS - FORMATION OF VIOLET COPPER COLLOIDS

Fluorine ions were implanted at an energy of 40 keV at room temperature into Cu-implanted (160 keV, 6 x 10(16) ions/cm2) SiO2 glass substrates in which implanted coppers occur in the form of nanosized metallic colloid particles with spherical shape. After the F implantation, the peak position of a band due to plasma oscillation shifted from 2.21 eV (562 nm) to 2.10 eV (591 nm) and the color changed from bulk copperlike to deep violet, visually. The bimodal distribution of depth Cu concentrations became distinct after the implantation. Cross-sectional transmission electron microscopy observation revealed that the distribution of copper colloid particles remains bimodal in shape and the particles coalesce with each other to form larger colloid particles with nonspherical shape. Fourier transform IR attenuated total reflection spectra showed that implanted F ions are incorporated in the form of O3Si-F units breaking continuity of the Si-O-Si network, suggesting that reduction of local viscosity in collision cascade regions during the implantation plays an important role in the observed coalescence.