Editor’s Note
This article highlights a significant advancement in materials science from Dalian University of Technology. Their novel polishing slurry achieves unprecedented smoothness and minimal subsurface damage on single crystal diamond, a notoriously hard material to process. This breakthrough could have wide-ranging implications for high-precision industries.
Researchers from Dalian University of Technology have developed a novel photocatalytic chemical mechanical polishing (PCMP) slurry tailored for Single Crystal Diamond (SCD) polishing, which achieves exceptionally smooth surfaces with minimal damage.
Within a 200 µm × 200 µm area, the Sa measures an impressive 0.079 nm, attesting to the surface’s superior quality finish. Additionally, the damage layer thickness stands at a remarkably thin 0.66 nm, highlighting the precision and minimal impact of the polishing process. The Material Removal Rate (MRR) peaks at 1168 nm·h⁻¹, further emphasizing the efficiency and effectiveness of this advanced polishing technique.
“The polishing efficiency of diamonds is one of the primary challenges impeding the advancement of diamond-based devices,” said professor Zhenyu Zhang, the corresponding author of this paper and a professor in DUT’s school of mechanical engineering, “It is challenging to balance the quality of polishing with efficiency when using a single energy field. Why not employ a multi-energy field-coupled polishing method to enhance the processing speed of diamond?”
SCD exhibits exceptional physical and chemical attributes, including superior thermal conductivity, an ultra-wide bandgap, and outstanding electronic properties. These qualities empower SCD to substantially elevate the performance and functionality of diverse systems and devices, thereby serving as a cornerstone in the advancement of modern technology.
However, the surface quality of SCD has a direct impact on the performance of SCD-based devices, with virtually all application fields demanding diamond surfaces of the highest quality. The formidable characteristics of SCD, such as its hardness, brittleness, wear resistance, and remarkable chemical stability, present significant hurdles in achieving high-quality surfaces. Therefore, efficiently achieving ultra-low damage and ultra-smooth SCD surfaces is of paramount importance.
In order to enhance the MRR of CMP and address the challenge of balancing polishing quality with efficiency in the diamond polishing process, the researchers from DUT selected PCMP as their preferred technique and utilized non-toxic PB and TiO₂ to prepare a novel green photocatalytic Fenton catalyst PB/TiO₂. Then, they applied this photocatalyst to the polishing process, which significantly enhanced both polishing efficiency and surface quality.
Within the PB/TiO₂ photocatalytic system, TiO₂ generates electrons under UV illumination that rapidly convert Fe³⁺ ions into Fe²⁺. This accelerates the Fenton reaction and significantly boosts the generation of •OH radicals, driving a swift oxidation process on the SCD surface. This process disrupts the orderly arrangement of carbon atoms, forming a soft, amorphous layer that is then efficiently removed by the abrasive action of the diamond.
Professor Zhang Zhenyu stated, “Although this novel polishing slurry has significantly improved polishing efficiency while achieving atomic-level diamond surfaces, it is currently limited to planar polishing. As technology advances, the demands for the shape and precision of diamond devices are becoming increasingly stringent, necessitating large-scale overall polishing treatments for these devices. Our future research will focus on the comprehensive polishing of diamond devices to enhance their surface quality and total performance.”
The researchers are continuing their work on the large-scale overall polishing of diamond devices. They aim to polish the device as a whole without compromising its shape or positional accuracy, while also reducing surface roughness and enhancing its overall performance.