SiO 2 surface defect centers studied by AES

Abstract

A theoretical model is proposed on how a Si dangling bond associated with an oxygen vacancy on a SiO 2 surface (E s′ center) should be observed by Auger electron spectroscopy (AES). The Auger electron distribution N A( E) for the L 23VV transition band is calculated for a stoichiometric SiO 2 surface, and for a SiO x surface containing Si-(e −O 3) coordinations. The latter is characterized by an additional L 23VD transition band, where D is the energy level of the unpaired electron e −. The theoretical N A( E) spectra are compared with experimental N( E) spectra for a pristine, and for an electron radiation damaged quartz surface. Agreement with the theoretical model is obtained if D is assumed to lie ≈2 eV below the conduction band edge. This result shows that AES is uniquely useful in revealing the absolute energy level of localized, occupied surface defect states. As the L 23VD transition band (main peak at 86 eV) cannot unambiguously be distinguished from a SiSi 4 coordination L 23VV spectrum (main peak at 88 eV), supporting evidence is presented as to why we exclude a SiSi 4 coordination for our particular experimental example. Application of the Si-(e −O 3) model to the interpretation of SiO 2Si interface Auger spectra is also discussed.