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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 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.

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The phonon confinement and self-limiting oxidation effects of silicon nanowires ͑SiNWs͒ synthesized by laser ablation were investigated. The size of SiNWs was controlled by the synthesis parameters during laser ablation and the subsequent thermal oxidation. Thermal oxidation increases the thickness of the SiNWs' surface oxide layer, resulting in a decrease in their crystalline Si core diameter. This effect causes a downshift and asymmetric broadening of the Si optical phonon peak due to phonon confinement, while excess oxidation causes an upshift due to compressive stress. The compressive stress retarded the oxidation of the SiNWs by self-limiting oxidation effect. This result shows that the Si core diameter can be controlled by compressive stress.