Effect of argon cluster ion beam on fused silica surface morphology

The gas cluster ion bombardment technique is promising for low-damage surface smoothing of optical materials. In this work, the morphology evolution of fused silica surfaces during argon cluster ion beam processing was investigated. To characterize the surface roughness, power spectral density functions (PSD) were obtained from a wide spatial frequency range of measurements. The power spectral density function dependencies on the depth of the removed material and cluster ion parameters are shown. Based on the experimental results, it is demonstrated that the use of gas clusters of different sizes and specific energy allows a fused silica surface to be smoothed in the middle spatial frequency (0.01–1 μm⁻¹) and high spatial frequency (1–100 μm⁻¹) ranges.