Spatially Resolved EELS Fine Structures at a SiO₂/TiO₂ Interface

Abstract

Abstract. 2014 SiO2/TiO2 multilayers stacks used in optical coatings have been studied by Electron Energy Loss Spectroscopy (EELS). The line-spectrum 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 L23 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 (TiO2 and SiO2) 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.

The Influence of Oxygen on Single Contact Resistance Studied by Electron Energy Loss Spectroscopy

“…As the fine structure of the oxygen peak is not comparable to TiO 2 from the literature the films seem to be amorphous or of nonstoichometric Ti x O y . 7,8 The lack of oxygen for sample 1 is correlated to a broad peak within the energy range of 470-490 eV which is missing for the oxygen-rich layers of sample 2a and b. At present it is not clear if this spectrum feature reflects a change in the titanium coordination, and thus the bandstructure, or if it is due to multiple scattering (plasmon plus Ti white lines).…”

The chemical state vector: a new concept for the characterization of oxide interfaces

“…The interaction of small moieties of a deposited oxide with the surface of another oxide implies the development of specific electronic and chemical interactions that may contribute to modify the physicochemical properties of the atoms at the interface. These changes, in turn, may be of the utmost importance for control of the performance of real systems such as catalysts, 5 the growth mode of oxide heterostructures, 6 etc. In previous papers we have approached the problem of describing the electronic interactions at a MO/M 0 O interface by x-ray photoelectron spectroscopy (XPS 13 In most cases the relaxation mechanism of the photoholes in the metal cations of these oxides is non-local.…”

Independent component analysis: A new possibility for analysing series of electron energy loss spectra

“…Here we consider the problem raised in [22] of a Si-SiO 2 interface where the two spectra far from the interface are known and a third unknown component is suspected close to the interface. 6 The aim of the study is to infer the shape of the unknown spectrum and to deduce the variation of composition across the interface, i.e., the weights of the different spectra in the mixture.…”