High-rate ultrasonic polishing of polycrystalline diamond films

• Polishing of polycrystalline CVD diamond with big rate is achieved using an ultrasonic machining (USM) with a diamond slurry.
• The surface roughness Ra can be reduced from ≈ 5 μm down to ≈ 0.5 μm just for 5 min treatment.
• Defects are formed in a sub-surface layer (< 6 μm) upon erosion damage by diamond particles impacts.
• A combination of the USM with other finishing methods could rationalize the entire polishing process

We report on fast polishing of polycrystalline CVD diamond films by ultrasonic machining in a slurry with diamond particles. The material removal mechanism is based on diamond micro-chipping by the bombarding diamond particles subjected to action of an ultrasonic radiator. The treated samples were characterized with optical profilometry, SEM, AFM and micro-Raman spectroscopy. The developed method demonstrates the polishing rate higher than those known for mechanical or thermo-mechanical polishing, particularly, the surface roughness of 0.5 mm thick film can be reduced in a static regime from initial value Ra ≈ 5 μm to Ra ≈ 0.5 μm for the processing time as short as 5 min. No appearance of amorphous carbon on the lapped surface was revealed, however, formation of defects in a sub-surface layer of a few microns thickness was deduced using Raman spectroscopy. The polishing of a moving workpiece confirmed the possibility to treat large-area diamond films.

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