Superpolishing of diamond

Abstract

On the basis of our successful experiments with sapphire, we have investigated the mechanochemical superpolishing of diamond. Whereas the conventional pure mechanical polishing with 0.25 μm diamond abrasive produces a residual roughness of about 1 nm r.m.s. on diamond (110) faces, measured by a Talystep profilometer, we achieved in dry polishing with a tin lap in air a residual roughness of less than 0.1 nm r.m.s. with a lateral resolution of about 100 nm. In our first experiments, we applied a circular saw equipped with a tin blade 0.6 mm wide running freely on a diamond face with a polishing speed of about 6 m s −1, charged by a normal force of 2 N which corresponds to a mean pressure of 3–10 N mm −2. Within 20 min a groove of 1 μm depth could be cut into diamond without remarkable wear of the tin blade. An investigation of various blade materials was undertaken, but best results were achieved with tin. Experiments were also done in several liquids and gases. With tin, no abrasion could be observed in nitrogen gas or with hydrogenated diamonds. Mechanochemical polishing by oxidation is suggested as mechanism for the dry superpolishing of diamond with tin in air.