Ultra-violet emission from one dimensional and micro-sized SiC obtained via microwave heating

Micro-sized and one-dimensional SiC were synthesized via microwave heating method, without using any metal impurity. The morphologies and micro-structures of the products were characterized by comprehensive methods, including scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). One-dimensional SiC has diameters of 10-200 nm and lengths up to several micrometers, while micro-sized SiC was mainly composed of micro-particles with diameters of 500-1000 nm. The difference on morphology between the two kinds of products may be caused by different growth rates along various crystal directions of SiC. The photoluminescence properties and band gap were characterized by fluorescence spectrophotometer and UV-VIS spectrophotometer at room temperature, respectively. Both the one-dimensional and the micro-sized SiC can emit ultra-violet light with similar wavelength range centered at 390 nm. The modified UV-VIS spectra from the Kubelka-Munk theory and Tauc's law suggested that the SiC products were not direct band gap semiconductors, but indicated that the two kinds of SiC products have different band gap types. The ultra-violet emission could not be attributed to the quantum confinement effect, while may be caused by the point defects on the surface or interface of the products.