Free Access
Microsc. Microanal. Microstruct.
Volume 7, Number 3, June 1996
Page(s) 161 - 174
Microsc. Microanal. Microstruct. 7, 161-174 (1996)
DOI: 10.1051/mmm:1996112

Spatially Resolved EELS Fine Structures at a $\bf SiO_2/TiO_2$ Interface

Nathalie Brun1, Christian Colliex1, Josette Rivory2 et Yu-Zhang Kui3

1  Laboratoire de Physique des Solides, URA CNRS 002, Université Paris-Sud, Bât. 510, 91405 Orsay Cedex, France
2  Laboratoire d'Optique des Solides, URA CNRS 781, Université P. et M. Curie, 4 Place Jussieu, Tour 13-12, 75252 Paris Cedex 05, France
3  Laboratoire de Reconnaissance des Matériaux dans leur Environnement, Université Marne-la-Vallée, 2 rue de la Butte Verte, 93166 Noisy-le-Grand Cedex, France

$\rm SiO_2/TiO_2$ multilayers stacks used in optical coatings have been studied by Electron Energy Loss Spectroscopy (EELS). The line-spec trum mode has been used: the incident electron probe of the STEM is scanned under digital control on the specimen surface in the direction perpendicular to the layers, while the whole spectrum is acquired. The selected energy range contains Ti $\rm L_{23}$ and O K edges, in order to study the evolution of the fine structures visible on these edges. Every experimental spectrum is then fitted with a linear combination of the two reference spectra ($\rm TiO_2$ and $\rm SiO_2$) extracted from the same sequence. It is possible to identify in the neighbourhood of the interface some EELS fine structures which cannot be fitted to a combination of reference spectra, but are representative of hybrid environments, such as Si-O-Ti in the present study. A quantitative analysis of the changes in different fine structures on the titanium and oxygen edges enables to clearly discriminate different levels of interdiffusion at the boundary.

6848 - Solid solid interfaces.
6822 - Surface diffusion, segregation and interfacial compound formation.

Key words
chemical interdiffusion -- electron energy loss spectra -- interface structure -- scanning transmission electron microscopy -- silicon compounds -- surface diffusion -- titanium compounds -- spatially resolved EELS fine structures -- SiO sub 2 TiO sub 2 interface -- multilayers stacks -- optical coatings -- line spectrum mode -- incident electron probe -- STEM -- interdiffusion -- SiO sub 2 TiO sub 2

© EDP Sciences 1996