SPATIALLY-RESOLVED EELS FINE-STRUCTURES AT A SIO2 TIO2 INTERFACE/

SiO2/TiO2 multilayers stacks used in optical coatings have been studie d by Electron Energy Loss Spectroscopy (EELS). The line-spectrum mode has been used: the incident electron probe of the STEM is scanned unde r digital control on the specimen surface in the direction perpendicul ar to the layers, while the whole spectrum is acquired. The selected e nergy range contains Ti L(23) and O K edges, in order to study the evo lution of the fine structures visible on these edges. Every experiment al spectrum is then fitted with a linear combination of the two refere nce spectra (TiO2 and SiO2) extracted from the same sequence. It is po ssible to identify in the neighbourhood of the interface some EELS fin e structures which cannot be fitted to a combination of reference spec tra, but are representative of hybrid environments, such as Si-O-Ti in the present study. A quantitative analysis of the changes in differen t fine structures on the titanium and oxygen edges enables to clearly discriminate different levels of interdiffusion at the boundary.