Structural identification of the silicon and nitrogen dangling-bond centers in amorphous silicon nitride

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Abstract
We report the observation of both silicon and nitrogen paramagnetic defect centers using X-band and Q-band electron spin resonance microwave excitation frequencies. By using two different microwave frequencies along with a computer analysis of the resonance lineshapes, we have been able to confirm and extend earlier observations regarding the chemical identity of these paramagnetic defects. Specifically, we provide additional evidence that the silicon dangling bond, i.e., K center, is an unpaired electron on a silicon atom bonded to three nitrogen atoms in stoichiometric silicon nitride. We further demonstrate that the g tensor of the K center exhibits very little anisotropy and that the lineshape is broadened primarily by hyperfine interactions of the nitrogens bonded to the silicon atom. We also confirm that the recently observed nitrogen dangling-bond resonance in silicon nitride is indeed due to a hyperfine interaction with a nitrogen nucleus. This improved understanding of these two important paramagnetic defects may be of importance in eliminating or perhaps exploiting their chemical properties.