The use of XPS for characterisation of glass fibre coatings

We present the results of an investigation of the use of X-ray photoelectron spectroscopy (XPS) as a tool for the rapid characterisation of glass fibre coatings. XPS data have been obtained from a wide range of commercial and experimental glass fibres using three different XPS instruments. By developing a protocol to plot ratios of appropriate atom concentrations, XPS analysis has been shown to give new insights into the in situ nature of the coating on glass. We show how these plots of atom ratios can be used to estimate the surface coverage of the coating on the glass fibres and obtain information on the chemical composition of the coating. Relationships between the XPS data and coated glass fibre parameters are clarified with the aid of a patchy overlayer model. We discuss the use of the XPS Si peak as a glass reference atom in different coverage regimes, and the effect of different XPS detector exit angles. In comparing data from three XPS instruments excellent correlation was obtained after correcting for differences in spectrometer sensitivity factors. (C) 1999 Elsevier Science Ltd. All rights reserved.