Synthesis of beta-SiC/SiO2 core-sheath nanowires by CVD technique using Ni as catalyst.

Cubic silicon carbide (beta-SiC)/SiO2 nanowires with uniform and knotted-core structures have been synthesized on nickel-coated Si(111) substrates at 1150 degrees C by using hexamethyldisilane (HMDS) as the source material in a hot wall atmospheric pressure chemical vapor deposition (APCVD) system. The nanowires consist of a single crystalline beta-SiC core wrapped with an amorphous SiO2 shell. The as-prepared SiC nanowires and the deposited Ni films were characterized by field emission scanning electron microscopy, X-ray diffraction, high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, micro-Raman spectroscopy, infrared spectroscopy and atomic force microscopy. The results show that the nanowires are random in direction and have diameter ranges from 25 nm to 70 nm. The core of the nanowires has a cubic zinc blend structure and a high density of planar defects is often found. The twin plane defects are suspected to be the main reason for the formation of the knotted-core SiC nanowires. A possible growth mechanism based on vapor-liquid-solid (VLS) by base growth technique is proposed.