Growth of SiC thin films on graphite for oxidation-protective coating

Abstract

We have deposited thick SiC thin films on graphite substrates in the temperature range of 700–850 °C using single-molecular precursors by both thermal metal–organic chemical-vapor deposition (MOCVD) and plasma-enhanced MOCVD (PEMOCVD) methods for oxidation-protection wear and tribological coating. Hexamethyldisilane (HMDS), (CH3)3Si–Si(CH3)3, was used as a single-source precursor, and hydrogen and Ar were used as a bubbler and carrier gas. A highly oriented polyerystalline cubic SiC layer in the [111] direction was successfully deposited on graphite at temperatures as low as 800 °C with HMDS by PEMOCVD. For thermal MOCVD, on the other hand, only amorphous SiC layers were obtained at 850 °C. From this study, we confirmed that PEMOCVD was a highly effective process in improving the characteristics of the SiC layers compared to those grown by thermal MOCVD. The mechanical and oxidation-resistant properties have been assessed. The optimum SiC film was obtained at 850 °C and rf power of 200 W. The maximum deposition rate and microhardness are 2 μm/h and 4336 kg/mm2 Hv, respectively. The hardness was strongly influenced by the composition ratio of the SiC protective layers.