XPS analysis of metallic trace contaminations on fused silica surfaces induced by classical optics manufacturing

Abstract

Impurities on glass surfaces, such as metallic trace contaminations induced by manufacturing processes, can cause severely disturbing effects as for example, a reduction in laser resistance or optical performance. Both the amount and nature of such impurities was thus investigated in the present work. For this purpose, fused silica surfaces were produced by classical optics manufacturing consisting of cutting, grinding or lapping and polishing with different pad materials. After each production step, the amount and the chemical binding state of the trace contaminations of interest–calcium, cerium and sodium, originating from the used operating materials–were determined via X-ray photoelectron spectroscopy. It is shown that in the course of manufacturing the chemical bonds of these elements and its compounds are modified. The polished fused silica optics feature the trace elements sodium, cerium and calcium bound in the form of NaOH, Ce2O3 and CaF2. Such surfaces moreover feature the lowest grade of contamination in the range of 0.2–0.5 atom-%.