NITROGEN INCORPORATION AT SI(001)-SIO2 INTERFACES - RELATION BETWEEN N 1S CORE-LEVEL SHIFTS AND MICROSCOPIC STRUCTURE

Using a first-principles approach, we study the incorporation of nitro gen at the Si(001)-SiO2 interface by calculating N Is core-level shift s for several relaxed interface models. The unusually large shift with oxide thickness of the principal peak in photoemission spectra is exp lained in terms of a single first-neighbor configuration in which the N atom Is always bonded to three Si atoms, both in the interfacial reg ion and further in the oxide. Core-hole relaxation and second nearest neighbor effects concur in yielding larger binding energies in the oxi de than at the interface. The calculations do not support the occurren ce of N-O bonds at nitrided Si(001)-SiO2 interfaces.