Catalyst-Free Chemical Vapor Deposition for Synthesis of SiC Nanowires with Controlled Morphology

Abstract

Chemical vapor deposition hydrogen reduction of methyltrichlorosilane (MTS) is most prominent method for production of silicon carbide (SiC) nanowires with controlled morphology. In a typical SiC nanowire synthesis process the cracking of MTS is carried out in reducing atmosphere of hydrogen using chemical vapor deposition technique at high temperature and normal atmospheric pressure. Taguchi method is very useful to design experiments specially in the cases where large numbers of variables are to be considered. This statistical method has been used to design the experiments to get the optimum parameters for bulk production of silicon carbide wires of uniform diameter in nanometer range. Further the effect of different parameters on the morphology of SiC deposit has been discussed. XRD and SEM analysis showed the growth of crystalline $$\upbeta $$ -SiC wires having different morphology. From the analysis of variance (ANOVA) of data it has been observed that growth temperature and hydrogen to MTS ratio in carrier gas are the two important parameters which decide the final growth morphology of SiC deposition. At higher temperature ( $$\ge $$ 1400 $$^{\circ }$$ C), the SiC nuclei prefer to grow as SiC grains rather than wires. The optimum deposition conditions have been obtained by analyzing Signal to Noise (S/N) ratio corresponding to lowest deposition rate and minimum growth diameter of SiC wires. The optimum deposition conditions have been used for uniform diameter growth of SiC nanowires, smoothness of the surface, and homogeneous growth of SiC on the surface. It has been observed that the hydrogen to MTS flow rate ratio value should be above 20 for the growth of SiC wires of nanometer diameter. The deposition temperature for the growth of crystalline SiC wires should be 1100–1300 $$^{\circ }$$ C. The total flow rate of carrier gas comprising of argon and hydrogen should be in moderate range for particular hydrogen to MTS ratio. The effect of H $$_{2}$$ /MTS mole ratio on morphology of SiC deposition by varying H $$_{2}$$ /MTS mole ratio from 0 to $$\sim $$ 80 has been discussed in detail. This detail process study has given a new perspective to produce SiC nanowires of high purity and homogeneous diameter by a simple atmospheric pressure CVD method without using a metallic catalyst. Even manipulation of growth parameters can be done to get desired morphology of SiC deposit.