Photocatalysis assisting the mechanical polishing of a single-crystal SiC wafer utilizing an anatase TiO2-coated diamond abrasive

This study introduces a new technique for depositing photocatalytic TiO2 thin layers on a nanodiamond (ND) abrasive to polish a single-crystal 6H-SiC wafer with sol-gel tools. A controllable and simple method is utilized to prepare ND/TiO2 composite abrasives by isothermal hydrolysis without conventional post-heating treatment for crystallization. The composites are characterized by X-ray diffraction and transmission electron microscopy. The TiO2 layer appears on the ND surface completely and continuously, and anatase TiO2 can be synthesized directly in this manner. An electrochemical experiment is performed to oxidize NaNO2 utilizing an ND/TiO2 electrode. Results indicate that ND/TiO2 with a hydrolysis reaction time of 18 h exhibits the best oxidative activity. The generation of hydroxyl radical (OH) from the ND/TiO2 composite has increased upon exposure to UV irradiation. A comparative polishing experiment revealed that an ultra-smooth surface and a higher MRR were achieved when applying the ND/TiO2 composite abrasives, superior to those of pristine diamond abrasives. This scenario is due to the SiC being oxidized by ·OH and forming a relatively soft SiO2 layer.