A novel visible-light catalyzed assisted single crystal diamond chemical mechanical polishing slurry and polishing mechanism

Abstract

Single crystal diamond has significant chemical and mechanical stability, which makes it challenging to efficiently obtain high quality single crystal diamond surface. In this study, the effect of four different sets of chemical mechanical polishing (CMP) slurries on the surface roughness Ra and the material removal rate MRR was investigated. The optimum slurry consisted of hydrogen peroxide, diamond micro-powder, synthesis product of nanodiamond and CuFe-layered double hydroxide (ND/LDH), oxalic acid and deionized water. After CMP by the optimum slurry, the average Ra value of three scanning ranges of 868 µm× 868 µm was 0.112 ± 0.003 nm and the average MRR value of three measurements was 416 ± 5 nm/h. High efficiency to obtain high quality single crystal diamond surface was achieved. The variation of hydroxyl radicals (·OH) concentration in the optimum slurry with time was measured. The optimum slurry CMP mechanism was elucidated by X-ray diffractometry (XRD) and X-ray photoelectron spectrometer (XPS). Visible-light photoelectrons and the rapid oxidation of C2O4·- radicals were accelerated the redox cycle of Fe3+/Fe2+ and Cu2+/Cu+ to produce·OH. The·OH oxidised the C atoms on the single crystal diamond surface to form -C-O-C-, -C-O-H and -CO. Finally, they were removed by diamond micro-powder abrasive, obtaining an ultra-smooth surface.