Characterization of zinc implanted silica: Effects of thermal annealing and picosecond laser radiation

Abstract

Zinc ion implanted silica with controlled thermal treatments and pulsed laser radiation has been investigated. Optical spectra of the as-implanted silica at higher doses (>3×1016 ions/cm2) and/or the samples annealed in a reducing atmosphere show both Zn clusters and Zn metal colloid formation. The absorption peak at ∼5.3 eV is attributed to the surface plasmon absorption of Zn metal colloids in silica. The oxidized samples with the ion dose ⩾3×1016 ions/cm2 show an absorption peak in 4.3–4.7 eV region implying ZnO quantum dot formation. It is expected that the average size of the ZnO nanoparticles becomes smaller for lower ion dose. Therefore, a blueshift of the absorption peak with lower ion dose can be attributed to the quantum confinement effects. Pulsed laser radiation at 266 nm with energy density of 30 mJ/cm2 causes a brownish coloration in these optically transparent Zn implanted silica substrates. The color formation is an irreversible process. Therefore, it is believed that new chemical species may have formed through photochemical reactions. The results also show that the coloring process is photon energy dependent.