THE SIO2-SI3N4 INTERFACE, .1. NATURE OF THE INTERPHASE

Recent reports in the literature have suggested that Si2N2O forms in the oxidation of Si3N4 as a buffer suboxide below the silica crust, and that equilibrium between SiO2 and Si3N4 requires the presence of this buffer. Here we report the examination of SiO2/Si3N4 boundaries of different genesis, by a variety of techniques, all of which failed to detect Si2N2O. What was found in each case is a graded suboxide whose composition merges seamlessly with the higher oxide above and the Si3N4 below. Part I presents the results of compositional depth profiling across the suboxide. In Part II a model is proposed to explain how O-2 diffusion in the graded suboxide limits Si3N4 oxidation kinetics.