Depth-resolved XPS analysis of classically manufactured glass surfaces: suggesting the impact of polishing-induced modifications on the performance of optical systems

During classical polishing, glass surfaces are inevitably chemically modified. Against this background, the composition of conventionally manufactured crown and flint glass surfaces was analyzed via depth-resolved X-ray photoelectron spectroscopy in this work. It is shown that essential glass-forming elements are reduced up to a depth of a few tens of nanometers, depending on the glass type. This indicates the inderdiffsuion of elements between the glass material and the aqueous polishing suspension. Moreover, contaminants from the suspension were detected at the glass surface. The results also suggest a gradient-like growth of a hydrated silica layer. Hence, the index of refraction of the glass surfaces is notably decreased by polishing as verified via ellipsometry. Ray tracing simulations show that this might lead to a decrease in imaging quality of optical systems.