Research Of Controlled Growth, Growth Mechanism And Properties Of SiC Nanoarray And Heterostructure

As one of the third generation of wide bandgap semiconductor, silicon carbide(SiC) has been attracting extensive interest due to its outstanding properties, such as high breakdown critical electric field strength, high electron saturation drift velocity,high electron mobility, high thermal conductivity, low dielectric constant,high resist radiation, good mechanical property and so on. It is suitable for fabricating high power device, high frequency device, high temperature device, high pressure and anti-radiation device. One dimensional SiC nanostructures with controlled synthesis can be used to construct SiC nanomaterials with different dimension, morphology and properties. It is considered necessary to conduct intensive study on synthesis, microstructure, growth mechanism and properties of SiC nanostructures for their future application. With the change of morphology and dimension of the nanostructure, the properties of nanostructure materials can evidently be different from the bulk. The aim of this research is to provide ideas and guidance for further study on micro-nano devices at the atomic or molecular level. The dissertation develops the following research on the problems of the controlled growth, growth mechanism and properties SiC based nanomaterials:1. Silica xerogels and nanocarbon powder were used as Si source and C source. Different Si C one-dimensional periodic nanomaterials were synthesized on single crystal Si(100) substrate by using Ag NO 3 and Ni(NO3)2 as catalyst respectively. The reaction was carried out by a carbothermal, chemical-vapor-deposition method(CVD) at 1400 ℃ for 6 h under argon atmosphere. And the structural characterization and growth mechanism was also studied. Si C nanowire quasi-arrays were also grown on Si substrate at 1470 ℃ for 3 h by using Ni(NO3)2 as catalyst. Under high temperature condition, the oriented array was formed by Si C intercrossing nanowires with diameters of about 50~200 nm, which were uniformly distributed and nearly parallel or orthogonal to each other. B y adjusting different substrates, the concentration of the Ni catalyst, reaction temperature, and reaction time, the growth of Si C nanowire quasi-arrays can be controlled. The SLS growth model was used to explain Si C nanocraystal at the initial stage. The continuous epitaxial growth of Si C nanow ries on Si C nanocraystal was governed by metal-catalyzed VLS mechanism. The photoluminescence emission peak of Si C nanowire quasi-arrays is about 316 nm and 430 nm, respectively. Si C nanowire quasi-arrays show the enhanced ?eld emission property with low turn-on electric field of 2.2 v/μm.2. Si C nanowire networks were also prepared by using carbothermal reaction between silica xerogels and nano carbon powder at 1400 ℃ for 2 h. Si C nanowires were grown on the Si substrate by VLS mechanism using Ni(NO3)2 as catalyst. The construction of networks were mainly depended on single-crystalline Si C nanowire branched growth processes and the welding processes by amorphous Si O 2 layer deposition on adjacent nanowires to form junctions. The formation mechanism of Si C nanowires was dominated by the VLS mechanism. The PL spectrum reveals that Si C nanowire networks have two broad emission bands centered at 369 nm and 400~600 nm. Si C nanowire networks have excellent photocatalytic ability for the degradation of M B under visible light. The degradation rate of MB is 90.164 % when the irradiation time is 6 hours.3. Novel Si C@CNT coaxial nanocables were successfully fabricated in large scale by using a carbothermal, chemical vapor deposition method. Silica xerogels containing multi-wall carbon nanotubes(M WCNT) were used as silicon source and carbon source. The coaxial nanocables were composed by 40~100 nm diameter carbon nanotube as the core, thick Si C out layer as shell. The morphology of Si C@CNT coaxial nanocable s was controlled by altering pre-treatment of substrate, catalyst type, the concentration of Ni catalyst, reaction temperature, reaction time and Ar carried gas flow. The formation of Si C@CNT coaxial nanocables was dominated by VLS growth mechanism and CNT spatially confine. Si C@CNT coaxial nanocables exhibit photoluminescence emission peaks at 461 nm and 573 nm. Si C@CNT coaxial nanocables are hydrophobic and the contact angle is 132.8°. Si C@C NT coaxial nanocables show higher photocatalytic activity to degrade MB under visible-light irradiation. The degradation rate of MB is 98.24 0% when the irradiation time is 6 hours. Si C@CNT coaxial nanocables show the enhanced ?eld emission property with low turn-on electric field of 1.1 v/μm and low threshold electric ?eld of 2.3 v/μm.