Damage-free tribochemical polishing of diamond at room temperature: a finishing technology

Polished surfaces are characterized by a geometric shape and a surface finish, the latter being defined by surface roughness (smoothness) and subsurface damage. In general, mechanically polished surfaces have a high geometric precision and are optically smooth, but they are subjected to surface and subsurface damage. Tribochemical polishing gives smooth surfaces and damage-free subsurfaces, but the surface geometric precision is often poor at the submicron level. Diamond is the hardest material known, and the standard polishing technique for such hard materials is mechanical polishing, causing surface and subsurface damage. In this paper a novel method of tribochemical polishing of natural and synthetic monocrystalline diamond at room temperature is described, which gives very smooth surfaces of, at least, (100) planes, free from surface and subsurface damage within the instrumental detection limits. Such diamond surfaces are van der Waals bondable to other materials. With this novel technology only low material removal rates can be achieved. Therefore, it is mostly adapted as a finishing technique. The described polishing technology can be applied to other (hard) materials as well.