High-precision mechanical polishing method for diamond substrate using micron-sized diamond abrasive grains

To remove subsurface damage and surface irregularities, we demonstrated a high-precision mechanical polishing technique with a polishing plate charged with micron-sized diamond abrasive grains. First, we prepared a polishing plate with a uniform protrusion height of the diamond abrasive grains and evaluated its geometrical structure with a scanning laser microscope. Subsequently, to determine the influence of the protrusion height of the diamond abrasive grains on polishing performance, we performed the mechanical polishing of a single-crystal diamond (100) substrate using two types of polishing plates. The obtained results showed that, using our mechanical polishing technique, the polishing plate with a uniform protrusion height of the grains could be fabricated and a high surface quality of the diamond substrate could be achieved. Moreover, the polishing plate significantly influenced the surface roughness of the polished diamond surfaces. During mechanical polishing, an average roughness (Ra) ranging from ~0.1 nm to 0.3 nm was obtained easily by controlling the process parameters.