This article presents a low-temperature plasma-assisted approach for the preparation of Si-SiO2 interfaces with monolayer concentrations of bonded nitrogen atoms (N atoms) at that interface. Localization of N atoms at Si-SiO2 interfaces has been established by on-line Auger electron spectroscopy (AES), off-line secondary ion mass spectrometry, and optical second harmonic generation. On-line AES studies have established that excess suboxide bonding in interfacial transition regions occurs during plasma-assisted oxidation using N2O and O-2 source gases, and that a postoxidation rapid thermal anneal at 900 degrees C for 30 s in an inert ambient reduces the concentration of these suboxide bonding groups. Defect generation at plasma nitrided interfaces in field effect transistor devices is reduced compared to similar devices in which Si-SiO2 interfaces are formed by furnace oxidation in O-2.