Microstructure and mechanical property of high growth rate SiC via continuous hot-wire CVD

An average growth rate of SiC at 3.4-28.5 μm/min can be achieved via continuous hot-wire CVD method with input powers of 300-380 W. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) analysis, and X-ray diffraction (XRD) method, combined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied to investigate the microstructure of deposits. At 300 W, amorphous SiC and Si were main products in deposit, which were rapidly replaced by crystallite SiC containing high density stacking faults at 340 W and above. Moreover, with the grain size of SiC increasing from ~25 to ~420 nm, the stacking faults probability decreasing from 0.179 to 0.125, as well as the surface morphology changed from loose-packed granules to a well-defined faceted structure with strong (111) texture. Structural changes led to the increase of deposit's Young's modulus from 266.3 to 341.5 GPa, and the mean tensile strength of SiC filament from 1.57 to 3.03 GPa. The successive growth of W/SiC interfacial layer above 360 W resulted in the reduction in mean tensile strength and Weibull moduls of SiC monofilaments, which agrees with the prediction from critical interfacial layer thickness theory.