The Research On Synthesis And Properties Of SiC Nanowires

Silicon carbide (SiC) materials have excellent properties, such as wide energy band gap, high thermal conductivity, high breakdown electric field, high saturation drift velocity. It makes SiC can be used in high temperature, high frequency, high power and radiation-resistance application. There are two semiconductor generartions before SiC. First generation is element semiconductors, such as Si. Second generation is compound semiconductor, such as GaAs, InP, GaP. Therefore, SiC is called third generation which was considered as new generational microelectronic device and integrated circuit. SiC nanowires become more important, when it was found that nanowires had better properties than bulk materials. Now lots of approaches have been developed, for example, arc-discharge, laser ablation, sol–gel method, carbon thermal reduction, and chemical vapor deposition. In most of these methods, expensive raw materials and complicated techniques were used, or catalyst impurities may exist. These drawbacks may limit the massive fabrication and application of SiC nanowires. It is still a challenge for scientists and industrials to synthesize large-scale SiC nanowires by using a simple and rapid method. So, we propose high frequency induction heating method to synthesize SiC nanowires.There are two kinds of fabrication processes we used in the high frequency induction heating method. First one is called“perpendicular fabrication process”. Reaction graphite tube was perpendicular placed and heated by high frequency induction cooper coil. SiO is vaporized and going down with the Ar gas used as protection gas, then react with carbon felt that surround the graphite tube. Finally, purity SiC nanowires are synthesized by this kind of process. But it can not always synthesize nanowires because the reaction atmosphere and condition is hard to control. Second process is called“horizontal fabrication process”. Reaction graphite tube was horizontal placed and the mixture of carbon source (coke) and silicon source (SiO) materials was heated by high frequency induction cooper coil. Although the SiC nanowires synthesized by this kind of process are not purity because of the existence of residual carbon and SiO2, easily control of the reaction condition make this process more useful for industrial fabrication.SiC nanowires have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Then a“nucleation, precipitation and growth”process was proposed to explain the growth of SiC nanowires, according to“VS”and“oxide-assisted cluster-solid”mechanisms.In the end, we prove the fact that SiC nanowires can easily dissolve in the deionized water by testing the Zeta potential (about -15mV). Some microelectrodes were fabricated through MEMS process. Then SiC nanowires are bridged on the microelectrode by dielectrophoresis method. The electrical properties of SiC nanowires were studied by Agilent model 4156C semiconductor parameters measuring instrument. We have the conclusion that the I-V curve of SiC nanowires is different from the normal materials which follow the ohm low. There is only a small current when in a range of voltage. But the current rapidly increase when voltage exceed a critical value.