Investigation of metal-coating-assisted IR nanosecond pulsed laser ablation of CVD diamond

Laser ablation is demonstrated to be a competent approach to processing chemical vapor deposition (CVD) diamond which is admitted to own poor machinability and is accordingly arduous to machine using conventional techniques. Notwithstanding, initial laser absorption by defects typically precipitates undesirable ablation quality and an increment in internal defects. The strategy of metal-coating-assisted laser ablation, which applies a coating on the diamond prior to laser irradiation to curtail defects and advance the quality of the ablated surface, is proposed in this study. In addition, an absorptivity-based laser energy distribution model is established to evaluate surface roughness and ablation depth. It can be concluded that the metal coating prevents local graphitization during the early ablation stage. The laser ablation of Ti-coated diamond surfaces resulted in a maximum reduction in surface roughness of 42.6% and 53%, respectively, for 100 and 500 nm coating, in comparison to that with the uncoated surfaces. Besides, the ablation depth of the laser-ablated 500 nm coating surface abates and reaches 21% in comparison with the uncoated diamond, while the 100 nm coating has a negligible effect on the ablation depth. In summary, the application of thin coatings on diamond prior to laser ablation results in homogeneous graphitization and a better surface finish with a marginal reduction in ablation depth.