Synthesis and Raman scattering of β-SiC/SiO₂ core-shell nanowires

The β-SiC/SiO₂ core-shell nanowires have been synthesized with the presence of iron catalyst by chemical vapor reaction using a mixture of milled Si and SiO₂ powders and C₃H₆ as the raw materials in a graphite reaction cell at lower temperature. The as-prepared nanomaterials are characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, and infrared spectroscopy. The results show that the nanowires consist of a 30-50 nm diameter single-crystalline β-SiC core wrapped with a uniform layer of about 10 nm thick amorphous SiO₂, and their lengths are up to several tens of micrometers. The nanowire axes lie along the [1̄ 1 1] direction and possess a high density of planar defects. Some unique properties are found in the Raman scattering from β-SiC/SiO₂ core-shell nanowires, which are different from previous observations of SiC materials. The vapor-liquid-solid (VLS) mechanism was proposed to elucidate the growth process.