Structural characterization and photoluminescence properties of SiC nanowires prepared by microwave method

SiC nanowires were synthesized by a microwave-heating method at 1480 degrees C for 80 min under vacuum, using silicon powder, silica dioxide powder and artificial graphite as raw materials. SEM, TEM and XRD were used to investigate the microstructure of the samples and excitation light with wavelength of 240 nm was used to test the photoluminescence properties of the products. Results indicated that beta-Sic can be synthesized directly without using a catalyst by the vapor-solid growth mechanism. The samples exhibited different morphologies and sizes at different zones due to the temperature differences. The products in an upper crucible were bright-green, relatively pure SiC, consisting of mainly nano-rods with a diameter of about 150 nm and small amount of SiC micro-crystals, and surface oxidation was not obvious. The products in other zones were grey-green with lots of SiC/SiO2 coaxial nanowires with a diameter around 20-50 nm and a SiO2 surface layer of thickness about 2 nm, and there was also some un-reacted graphite and silica dioxide. Both the SiC nano-rods and SiC/SiO2 coaxial nanowires exhibited a strong broad photoluminescence peak at a wavelength of about 390 nm and a high degree of blue-shift compared with the reported luminescence of beta-SiC nano-materials.