A study of the effect of excessive free carbon on mean whisker diameters grown by chemical vapor deposition

Silicon carbide whiskers were grown by chemical vapor deposition without a metallic catalyst at a temperature ranging between 1000 and 1100 °C, and at a constant pressure of 5 Torr with input gas ratios, α [H2/MTS (methyltrichlorosilane)], of 30 to 50. The mean diameter of the whiskers changed as temperature and input gas ratios were varied. To determine why the diameter of the whiskers changed, we investigated the effect of these two parameters, temperature and gas ratio, on the stoichiometry of the deposit, both from thermodynamical calculations and from XPS measurements on the as grown whiskers. We demonstrated that the amount of free carbon increases as the temperature increases and the input gas ratio decreases. We showed the correction between the amount of free carbon and the mean whisker diameter.