Surface processing of amorphous optical materials by argon cluster ion beam

The production of a high-quality surface of fused silica is an important task for advanced optical technologies. In this work, the surface of fused silica has been processed by argon cluster ion beam having mean cluster size N _mean ranged from 180 to 1000 atoms/cluster and energy E ranged from 5 to 23.5 keV. The analysis of surface morphology using atomic force microscopy and the spectral power density (PSD) function shows a noticeable smoothing of roughness in different spatial frequency ranges, depending on the cluster ion parameters. To evaluate the processing efficiency, the dependence of the etching rate of SiO₂ on the parameters of cluster ions has been investigated. It is shown that the etching rate v _etch is determined by the energy per atom in the cluster E/N _mean and it varies from 0.2 to 20 nm/min with an energy change from 5 to 130 eV/atom.