Atomic surface of diamond induced by novel green photocatalytic chemical mechanical polishing with high material removal rate

Atomic surfaces are strictly required by high-performance devices of diamond. Nevertheless, diamond is the hardest material in nature, leading to the low material removal rate (MRR) and high surface roughness during machining. Noxious slurries are widely used in conventional chemical mechanical polishing (CMP), resulting in the possible pollution to the environment. Moreover, the traditional slurries normally contain more than four ingredients, causing difficulties to control the process and quality of CMP. To solve these challenges, a novel green CMP for single crystal diamond was developed, consisting of only hydrogen peroxide, diamond abrasive and Prussian blue (PB) /titania catalyst. After CMP, atomic surface is achieved with surface roughness Sa of 0.079 nm, and the MRR is 1168 nm·h⁻¹. Thickness of damaged layer is merely 0.66 nm confirmed by transmission electron microscopy (TEM). X-ray photoelectron spectroscopy, electron paramagnetic resonance and TEM reveal that •OH radicals form under ultraviolet irradiation on PB/titania catalyst. The •OH radicals oxidize diamond, transforming it from monocrystalline to amorphous atomic structure, generating a soft amorphous layer. This contributes the high MRR and formation of atomic surface on diamond. The developed novel green CMP offers new insights to achieve atomic surface of diamond for potential use in their high-performance devices.