Synthesis of carbon coated beta-SiC nanofibers by microwave plasma assisted chemical vapour deposition in CH_4/H_2 gas mixture

摘要

A simple and direct synthesis method was used to grow silicon carbide nanofibers in CH4/H2 mixture on silicon substrates covered by Fe thin film catalyst using microwave plasma assisted chemical vapour deposition. The silicon source is the substrate itself. The samples have been characterized by field emission scanning electron microscopy and transmission electron microscopy combined with electron energy-dispersive X-ray spectroscopy. These characterizations revealed that fibrous nanostructures having stacking faults planes perpendicular to the growth direction coexist with fibrous with no stacking fault. These two types have a core-shell structure, with a diameter of 25-65 nm, and were both assigned to 3-SiC. Selected area electron diffraction pattern shows that the faulted SiC structures exhibit streaks indicating defects (irregular layers) while the other ones have a single crystal pattern. One can also observe that the SiC nanofibers grow along (111) orientation. The formation of SiC nanofibers can be explained by the diffusion of Fe in the silicon substrate due to the high temperature during the process which is around 900 deg C. The combination of the etching of the surface by atomic hydrogen and the interaction with carbon radicals and carbon atoms allows then the growth of SiC nanofibers.