Photoluminescence of hexagonal-shaped SiC nanowires prepared by sol-gel process

New hexagonal-shaped SiC nanowires were synthesized through a sol-gel and direct heating process. Electron microscopy, X-ray diffraction and Raman spectrum indicate the nanowires possess a β-SiC structure and have typical diameters of 50-100 nm and length up to several tens of micrometers. Two strong broad ultraviolet light emission peaks at about 290 and 396 nm are observed at room temperature from the hexagonal-shaped nanowires, which are excitated by 250 nm ultraviolet fluorescent light. Compared with the previous reports, the synthesized nanowires exhibit two larger buleshifts in the photoluminescence (PL) spectrum. The buleshift of former PL peak is attributed to the oxygen defects in SiO_x layer and the second one is due to morphology and size confinement effects of the SiC nanowires. Memory effect may be responsible for the hexagonal shape formation of SiC nanowires during vapor-solid growth process.