Oxidation of Silicon Carbide

Most of the available studies of the oxidation of SiC (e.g., [1,2]) find that although the rate of oxidation decreases with time, it does so at a rate somewhat less than would be expected from the normal thickness controlled parabolic rate law. This higher than anticipated rate of oxidation suggests the possibility of small cracks or other such imperfections in the surface which will locally increase the rate of oxidation. In order to explore this phenomenon further, several samples of fully dense SiC were oxidized in air at 1500°C. After oxidation scanning electron micrographs were taken of the surface and, as can be seen in Figure 1 the oxide surface appears to be covered with crater-like or pock-like features. Figures 2a and b, enlarged portions of 1, clearly show these features to be bubbles which apparently are perculating up through the oxide to the surface.