Contamination of fused silica surfaces polished with alumina suspensions of different concentrations

The chemical-mechanical polishing (CMP) of glass remains a complex and not fully understood process due to the brittle nature of glass and its material flow under load. To gain deeper insights into polishing suspension-glass interactions, fused silica samples were polished using aluminum oxide suspensions of varying concentrations. The resulting surfaces were analyzed via X-ray photoelectron spectroscopy (XPS), revealing distinct contamination trends: aluminum and sodium surface concentrations increased with suspension concentration and pH value, respectively, while calcium and carbon content decreased. These trends are attributed to concentration-dependent interactions between the polishing pad, water, and polishing agent grains with the glass surface. XPS spectral deconvolution confirmed notable adhesion of aluminum oxide and modifications in the near-surface silicon oxide structure. Depth-resolved sputtering analysis further indicated that contamination mainly occurs at the outermost surface, but also extends into deeper regions of the material. Such impurities may significantly affect optical performance, reducing laser-induced damage threshold through absorption, degrading imaging quality via scattering, and impairing coating performance and adhesion. These findings enhance the understanding of CMP mechanisms and provide insights for improving the precision machining of optical components.