Fabrication of Smooth and Ultra-Sharp Diamond Knives of Lower than 60 nm Tip Diameter by Low Energy Oxygen Ion Beam Machining

Abstract

Conventional grinding and polishing mechanisms for fabricating ultra-sharp diamond knives often cause subsurface damage and micro-chipping at the cutting edge. Compared to mechanical methods, ion beam machining (IBM) is considered more suitable for nano-scale machining of diamond materials. But the problems associated with IBM are facet formation, ripples formation and high irradiation damage. In order to overcome all theses problems, we proposed a 500 eV O + /O + 2 ion beam machining for the fabrication of smooth and ultra-sharp diamond knives from mechanically coarse finished samples. In our method, the knives are irradiated at tilted condition to avoid facet formation at the cutting edge. To suppress ripples formation and obtain isotropic smoothening of the surface, the stage is simultaneously rotated around the axis of ion beam incidence. To reduce the irradiation damage, a low energy reactive ion species is used in this method. A simulation model is developed to predict the profile change of knives at different tilted conditions and then compared with experimentally obtained results. We achieved sharpening down of the apex angle from 90• to 68• and from 60• to 48• by 5 hrs of machining. We also successfully reduced down the diameter of tip from 5 µm to lower than 60 nm with an average cutting edge irregularity 20-40 nm.