Absorption spectra of Ni nanoparticles in silica glass (SiO<sub>2</sub>) fabricated by negative-ion implantation of 60 keV Ni to 4x10<sup>16</sup> ions/cm<sup>2</sup> were determined from three sets of spectra, i.e., transmittance, reflectance of implanted-surface side and that of rear-surface side, of the same samples, to exclude incoherent multiple reflection (ICMR) due to substrates. Although the absorption spectrum of as-implanted state is smeared with defect absorption, two absorption bands at 3.3 and 6.0 eV due to Ni nanoparticles are observed after annealing at 800°C in vacuum. However, a predicted peak energy from a criterion for surface plasmon resonance (SPR), ε<sub>m</sub>'(ω) + 2 ε<sub>d</sub>'(ω) = 0, was in 2.8 eV, far away from the observed peaks. Another criterion, (ε<sub>m</sub>' + 2ε<sub>d</sub>')<sup>2</sup> + (ε<sub>m</sub>'')<sup>2</sup> = minimum, gives the peak energy of 5.9 eV. From decomposition of the dielectric constants into free- and bound-electron contributions, we conclude that the 3.3 eV peak is SPR-like, although the contribution of the bound-electrons to the 3.3 eV peak is not small. Size dependence also supports the assignment of the 3.3 eV peak. The large contribution of the bound electrons is due to a nature of the partially filled <i>3d</i> orbitals of Ni. This is contrast to the closed <i>3d</i> orbitals of Cu, and probably is the origin of the broad peak width.
The magnetic nanoparticles are fabricated in silica glass (SiO<sub>2</sub>) using high-flux implantation of nickel negative-ions of 60 keV. Photo-absorption measurements and the cross-sectional transmission electron microscopy (XTEM) observation confirm formation of metallic Ni nanoparticles in SiO<sub>2</sub>, and exclude possible formation of Ni silicides (Ni<sub>3</sub>Si, Ni<sub>2</sub>Si, NiSi) and oxides (NiO) as major products. The mean diameter of the nanoparticles was in ~2.9 nm, and the depth distribution was similar to the prediction from the TRIDYN code with taking account of the sputtering. Temperature- and field- dependences of magnetization show that the nanoparticles are in the super-paramagnetic state with a blocking temperature of ~27 K.