Growth of SiC protective coating layers on graphite using single molecular precursors

摘要

We have deposited thickn SiC thin films on graphite substrates at temperature range of 700 approx 850 deg C using single molecular precursors by thermal MOCVD and PEMOCVD methods for oxidation protection wear and tribological coating. Two organosilicon compounds such as diethylmethylsilane (DEMS), (Et)_2SiH(CH_3), and hexamethyldisilane (HMDS), (CH_3)_3Si-Si(CH-3)_3, were utilized as ingle source precursors, and hydrogen and Ar were used as a bubbler and carrier gas. Polycrystalline cublic SiC protective layers in [110] direction were successfully grown on graphite substrates at temperature as low as 800 deg C from HMDS by PEMOCVD. In the case of thermal MOCVD, on the other hand, only amorphous SiC layers were obtaind with either HMDS or DEMS at 850 deg C. We compared the difference of crystal quality and physical properties of the SiC protective layers grown by thermal MOCVD and PEMOCVD methods. PEMOCVD was highly effective process in improving the characteristics of film compared to those of thermal MOCVD. The optimum SiC film was obtained at 850 deg C and RF power of 200 W. The maximum deposition rate and microhardness are 2 mu m/h and 4,336 kg/mm~2Hv, respectively. The hardness was strongly influenced with the stocihiometry of SiC protective layeers. During CVD, the plasma diagnositcs and residual gas analysis were in situ carried out usikng optical emission spectroscopy (OES) and quadrupole mass spectrometer at various RF powers. The asgrown SiC protective layers were ex situ characterized with XRD, XPS, and SEM. the mechanical and oxidation-resistant properties have been checked with Knoop microhardness tester and TGA.