Silicon nanowires (SiNWs) were prepared by laser ablation at high temperature and studied by electron microscopy and optical spectroscopy. As-synthesized SiNWs are found orderly aligned on the silica substrates, exhibiting uniform shape with a silicon crystalline core and an amorphous silicon oxide sheath. Asymmetrically broadened Raman spectral peaks downshifted from 520 cm(-1) were observed, which related to the confinement effects of optical phonon by nanowire boundaries. The SiNWs showed strong photoluminescence (PL) bands peaked at 455 and 525 nm, which quenches rapidly with an increase in temperature and may arise from the defects surrounding the silicon nanowire crystalline core. (C) 2003 Elsevier Science B.V. All rights reserved.