A new nano-diamond based mechanical polishing process has been developed and optimized for polishing super hard materials such as SiC, sapphire and diamond samples. The nano-diamond based process uses specially engineered nano-diamond particles that has ability to react with super hard materials when used for polishing. Such a reactive nano-diamond process leads to removal rates of about an order higher than the base particles and yields ultra-smooth surfaces (RMS <0.5nm) on the super hard materials along with very low sub-surface damage. The process yielded surface roughness less than 1 nm for silicon carbide, sapphire and diamond materials. The process has been studied for single crystalline, poly-crystalline and composite materials. The removal rates for different materials with the newly developed nano-diamond process compared to base nano-diamond particles and the surface finish obtained with the use of atomic force microscope, optical interferometer and tropel flat master will be presented. The mechanism of nano-diamond process will be explained in the conference.
A new reactive chemical mechanical polishing process has been developed and optimized for polishing CVD SiC mirror samples. The studies show that the abrasives, chemical nature of the slurry, and other additives play an important role in the material removal rate and surface finish of the SiC mirror. The use of different abrasive types and sizes resulted in differing roughness and removal rates. The smaller abrasives created surface defectivity or higher roughness. This can be explained by different polishing rates of different orientations of SiC grains, resulting in the grain enhancement. Under optimal conditions with appropriate abrasive particles, roughness RMS as low as 0.2 nm was achieved on CVD SiC samples. The process also did not show any scratch-like features in the optical interferometry measurements.
Sapphire is uniquely suitable for sensor windows of electro-optical systems due to its high transparency, high mechanical strength, and chemical inactivity. Unfortunately, these same characteristics also cause polishing of sapphire windows to be extremely difficult and slow. Hence the challenge is to develop a process for affordable production of large area sapphire windows with low-roughness, low-stress and without surface and subsurface damage. Here we report a novel rapid chemical mechanical polishing process that increases the material removal rate during polishing of sapphire by greater than twofold over conventional processes. Such a process can also produce angstrom level surface finish.