QUANTITATIVE XPS ANALYSIS OF LEACHED LAYERS ON OPTICAL-GLASSES

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 stud y glass surfaces with respect to their surface corrosion. In particula r, leaching by the influence of polish slurries, pure water, air and e ven residual gases inside a vacuum device was studied in detail. Pure quartz glass and different sodium and barium silicate glasses were bro ken in ultrahigh vacuum (4 x 10(-10) mbar) for the determination of se nsitivity factors of the different XPS signals. It was found that a qu antitative determination of the surface composition of corroded and le ached layers is possible by determination of the intensities of the XP S O 1s, Si 2p, Si 2s, B 1s, Na 1s, Na 2s, Na 2p, Ba 3d and Ba 4d signa ls. After leaching in aqueous solutions, the barium is exchanged by hy drogen via an interdiffusion mechanism, resulting in an enrichment of different hydrogen bonds (H2O/H3O+, OH-, =Si-O-H) in the leached layer . An iterative algorithm is shown, which allows, in addition to the co ntent of all other elements, the hydrogen content to be determined qua ntitatively 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 consi dered and the calculated density is used to perform matrix-dependent i ntensity corrections for the attenuation length.