ABSTRACT
The very low-energy irradiation effect that is characteristic of GCIB can be employed to substantially reduce surface defects
on almost any highly polished material. Chemical mechanical polishing (CMP) techniques used for preparation of optical surfaces can result in numerical surface roughness values of only a few angstroms, but the surfaces typically still contain high densities of shallow scratches and other defects. These flaws, which cannot be corrected by additional processing using conventional ion beams or electron beams, can often be eliminated easily by GCIB bombardment. A representative example is shown in Figure 9.1 for the case of the surface of a lens made of CaF2, a relatively soft optical material upon which it is normally exceptionally difficult to eliminate scratches caused by mechanical polishing action. The atomic force microscope (AFM) images before and after polishing by Ar-GCIB clearly illustrate the characteristic smoothing behavior of GCIB [1].
