Investigation on morphology and chemistry of the Beilby layer on polished fused silica

The Beilby layer that exists on the polished fused silica surface, not only contains elevated levels of polishing contaminants, but also cloaks the subsurface damage (SSD), which SSD and polishing contaminants are the vital factors leading to the decrease of laser induced damage threshold of fused silica. Herein, the morphology of the Beilby layer on fused silica after chemical mechanical polishing (CMP) is characterized, and polishing contaminant, namely CeO2, exists as an atom in the Beilby layer is proved. Besides, we investigate the chemical valence state of CeO2 embedded in the Beilby layer for the first time. The results certify that the chemical reaction between CeO2 and fused silica during CMP, and Ce3+ in CeO2 is the main reactant reacts with fused silica. Furthermore, combined with the measurement of Time-of-flight secondary ion mass spectrometry, we directly demonstrate the existence of the physical adsorbed and chemisorption water in the Beilby layer from a novel perspective that the effect of adsorbed water removal by heat post-treatment on surface morphology.