High-resolution elemental profiles were obtained from SiO2(N)∕4H-SiC structures by spatially resolved electron energy-loss spectroscopy (EELS) performed in the scanning transmission electron microscopy mode. The results show that following annealing in NO, N was exclusively incorporated within ∼1nm of the SiO2(N)∕4H-SiC interface. Mean interfacial nitrogen areal densities measured by EELS were ∼(1.0±0.2)×1015cm−2 in carbon-face samples and (0.35±0.13)×1015cm−2 in Si-face samples; these results are consistent with nuclear reaction analysis measurements. Some of the interface regions in the C-face samples also showed excess carbon that was not removed by the NO annealing process, in contrast with previous results on Si-face samples.

Nitrogen incorporation at the SiO2∕SiC interface due to annealing in NO is measured and shown to be a strong function of crystal face. The annealing process involves two major solid-state chemical reactions: nitrogen uptake at the interface and N loss associated with second-order oxidation. An ad hoc kinetics model explains the experimental observations of anisotropy and nitrogen saturation.

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