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Local vibrational modes of boron ͑B͒ in silicon nanowires ͑SiNWs͒ synthesized by laser ablation were observed at about 618 and 640 cm −1 by Raman scattering measurements. Boron doping was performed during the growth of SiNWs. Fano ͓Phys. Rev. 124, 1866 ͑1961͔͒ broadening was also observed in the Si optical phonon peak. These results prove that B atoms were doped in the SiNWs. Hydrogen ͑H͒ passivation of B acceptors in the SiNWs was also investigated. A broad peak was observed at around 650-680 cm −1 after hydrogenation, demonstrating that B dopants were passivated by the formation of the well-known H-B passivation centers.

A purification procedure for single-walled nanotubes is presented in this report. A novel purification method that incorporates the hydrothermal treatment along with other treatments such as extraction of fullerenes and oxidation and dissolution of metal particles is used in this study. The effects of each treatment in the purification process is also discussed by characterizing the intermediate products using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy.

A gradual downshift and asymmetric broadening of the Si optical phonon peak were observed by Raman scattering measurements of continuously thermally oxidized silicon nanowires ͑SiNWs͒ synthesized by laser ablation. This downshift and broadening can be interpreted by the phonon confinement effect. Further thermal oxidation produced a reverse change; namely, an upshift of the optical phonon peak. This is considered to be due to compressive stress since this stress was relieved by removing the oxide layers formed around the SiNW cores, resulting in a downshift of the optical phonon peak.

Pure (unstabilized) zirconia nanoparticles in the fluorite-type cubic phase are observed by transmission electron microscopy. Microscopic observations at a pressure of 5 × 10 -5 Pa suggest that the phase transition from the cubic to tetragonal phase arises for particles near 2 nm in diameter. First principles computer simulations of large zirconia clusters show that the critical size of the transition could occur for a diameter of 2.05 ± 0.15 nm, which is in good agreement with the experimental value.