A Mixed Interface Reaction/Diffusion Control Model for Oxidation of Si3 N 4

The observed parabolic rate constants for the oxidation of at 1100 to 1400°C are 10 to 1000 times lower than those for the oxidation of silicon. Calculations are performed to determine parabolic rate constants from the existing oxygen tracer diffusivity values and from the diffusivity and solubility values of the dissolved diatomic oxygen. These calculations suggest that the rate of oxidation is not controlled by oxygen diffusion. Instead, it is controlled by a mixed process involving reaction at the interface and nitrogen diffusion through . A detailed analysis indicates that the rate law can be nearly parabolic for this mixed control process.