SIO2 SURFACE DEFECT CENTERS STUDIED BY AES

A theoretical model is proposed on how a Si dangling bond associated with an oxygen vacancy on a SiO2 surface (Es′ center) should be observed by Auger electron spectroscopy (AES). The Auger electron distribution NA(E) for the L23VV transition band is calculated for a stoichiometric SiO2 surface, and for a SiOx surface containing Si-(e-O3) coordinations. The latter is characterized by an additional L23VD transition band, where D is the energy level of the unpaired electron e-. The theoretical NA(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 L23VD transition band (main peak at 86 eV) cannot unambiguously be distinguished from a SiSi4 coordination L23VV spectrum (main peak at 88 eV), supporting evidence is presented as to why we exclude a SiSi4 coordination for our particular experimental example. Application of the Si-(e-O3) model to the interpretation of SiO2Si interface Auger spectra is also discussed. © 1978.