Investigation of roughness evolution of ion sputtered fused silica surface

Ion beam polishing (IBP) has been widely used in smooth surface manufacturing. Nevertheless, the evolution of the process and mechanisms of the change in surface roughness have not yet been fully clarified. In this paper, the evolution of surface morphology at the micrometer scale under IBP is studied. First, a series of experimental results indicate that the results at the nanometer and micrometer scales are not consistent. Second, a two-step positioning method that can accurately acquire a contour location before and after polishing is proposed to improve the reliability of the experimental results at the micrometer scale. This method can help analyze the effect of surface morphology on the amount of material removal and can eliminate errors introduced by the method of averaging measurements at different positions selected randomly. Furthermore, a correlation analysis is conducted between the profiles of the amount of material removal and the initial contours, at the micrometer scale. A similarity is revealed between the removal amount and the initial morphology. Finally, a simulation of the evolution process of morphology is performed, based on the dominant smoothing mechanism. It is consistent with the experimental results. The simulation reveals that the mass redistribution of surface atoms, induced by the ion beam, plays an important role in the evolution of the micromorphology of the surface. The analysis helps to further research on roughness optimization at the micrometer scale.