For decades, silicon has been the main force in electronic products, because it is not only a common element, easy to process, but also has good electronic properties. The only limitation of silicon is that high temperature can damage it, which limits the operating speed of silicon-based electronic products.
Single crystal diamond is a possible substitute for silicon. Researchers have recently manufactured a single crystal diamond wafer, but the ordinary surface polishing method is very slow and damages the material.
In a study recently published in "Scientific Reports", researchers and partners from Osaka University polished single crystal diamond wafers to nearly atomically smooth. This process will help diamond replace some of the silicon components in electronic devices.
Diamond is the hardest substance known and basically does not react with chemical substances. Polishing it with the same hard tool will damage the surface, while the traditional polishing chemical reaction is slow. In this study, the researchers essentially modified the quartz glass surface first, and then polished the diamond with the modified quartz glass tool.
"Plasma-assisted polishing is an ideal technology for single crystal diamonds," explained lead author Nian Liu. "The plasma activates the carbon atoms on the diamond surface without destroying the crystal structure, so that the quartz glass plate gently smooths the irregularities on the surface."
The single crystal diamond before polishing has many step-like features, the whole is wavy, and the average root mean square roughness is 0.66 microns. After polishing, the structural defects disappeared and the surface roughness was greatly reduced, only 0.4 nanometers.
"Polishing reduces the surface roughness to close to atomic smoothness," said lead author Kazuya Yamamura. "There are no scratches on the surface, as seen in the mechanical smoothing method."
In addition, the researchers also confirmed that no chemical changes occurred on the polished surface. For example, they did not detect graphite, therefore, there was no damaged carbon. The only impurity detected was a very small amount of nitrogen from the original wafer preparation.
"Using Raman spectroscopy, the full width at half maximum of the diamond wire in the wafer is the same, and the peak position is almost the same." Liu said, "Other polishing techniques have significant deviations from pure diamond."
Through this research and development, high-performance power devices and heat sinks based on single crystal diamond can now be realized. This technology will greatly reduce the power consumption and carbon input of future electronic equipment and improve performance.
The title of the paper is "Damage-free highly efficient plasma-assisted polishing of a 20-mm square large mosaic single-crystal diamond substrate".