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

Abstract

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.