DETERMINATION OF NEAR-SURFACE FORCES IN OPTICAL POLISHING USING ATOMIC-FORCE MICROSCOPY

An atomic force microscope was used to measure near-surface forces between individual metal-oxide polishing agent particles and planar optical glass surfaces immersed in aqueous fluids of carefully controlled chemistry. For a given polishing agent, the fluid pH was found to significantly influence the magnitude of the near-surface forces. Generally, if the fluid pH equals the isoelectric point of the polishing agent, then the attractive force between the polishing agent particle and the glass surface is maximized. The pH-driven modulation of near-surface forces was found to be completely reversible, indicating the need to control surface change during aqueous polishing of optical glass through manipulation of the slurry chemistry.