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RESEARCH PRODUCT

Quantitative XPS analysis of leached layers on optical glasses

subject

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The corrosion of optical glasses often reduces the utility of uncoated glasses as well as the adhesion of resistive coatings deposited onto corroded glasses. Photoelectron spectroscopy (XPS) was applied to study glass surfaces with respect to their surface corrosion. In particular, leaching by the influence of polish slurries, pure water, air and even residual gases inside a vacuum device was studied in detail. Pure quartz glass and different sodium and barium silicate glasses were broken in ultrahigh vacuum (4 × 10−10 mbar) for the determination of sensitivity factors of the different XPS signals. It was found that a quantitative determination of the surface composition of corroded and leached layers is possible by determination of the intensities of the XPS O 1s, Si 2p, Si 2s, B 1s, Na 1s, Na 2s, Na 2p, Ba 3d and Ba 4d signals. After leaching in aqueous solutions, the barium is exchanged by hydrogen via an interdiffusion mechanism, resulting in an enrichment of different hydrogen bonds (H2O/H3O+, OH−, SiOH) in the leached layer. An iterative algorithm is shown, which allows, in addition to the content of all other elements, the hydrogen content to be determined quantitatively in the leached layers. Furthermore, the calculation of the density of surface layers becomes possible. For an exact analysis of the leached layers the intensity loss by contamination layers is considered and the calculated density is used to perform matrix-dependent intensity corrections for the attenuation length.