Effects of Deposition Temperature on the Microstructures of SiC Coatings by CVD

The coatings of SiC were prepared from the methyltrichlorosilane (MTS) by low pressure chemical vapor deposition from 950℃to 1300℃. SEM was used to characterize the surface and cross-sectional morphologies of the as deposited coatings. The effects of temperature on the microstructures of SiC coatings were investigated. At 950℃, the as-deposited SiC coating is loose and the grains of the coating are fine. In the temperature range of 1000-1100℃, CVD SiC coatings show a dense and smooth surface morphology. However, in the temperature range of 1150-1300℃, the surface morphology of SiC coatings changes to rounded hillocks and the as-deposited coatings are very rough. Factors influencing the surface morphologies and structures of SiC coatings were studied through thermodynamics and nucleation-growth theory. The relationship between deposition temperature and SiC coatings' cross-sectional morphologies can by listed as follows, the as deposited coatings are very dense and there are no holes when the deposition temperature is lower than 1200℃, however, the as deposited coatings become very loose at 1300℃. The inside structures of SiC coatings were interpreted by the island growth model.