A Generic Interior Damage Free Approach for Nanosecond Pulsed Laser Ablation of Single Crystal Diamond Substrate Via Metal Film Induced Self-Maintaining Graphitization

When laser ablation was conducted on an uncoated single-crystal diamond (SCD) substrate, interior damage and random ablation were observed. Metal film induced self-maintaining graphitization (MISG) was proposed as a generic approach to solve this problem. MISG was realized through coating ~100 nm thick metal-film on SCD substrate. Experiments of the laser irradiation on the metal film, such as Au, Al, Ti, Pt, coated SCD substrate show that the material removal depths were the same with using the same output power, and surface was covered by graphite after laser irradiation. In addition, the laser-induced damage on the upper or lower surface in the case of uncoated SCD substrate disappeared. The semi-transparent model based on Beer-Lambert law and the opaque model based on modified Level-Set method were built to simulate the laser irradiation on the uncoated and metal-coated SCD substrate. In the case of uncoated one, laser energy was largely absorbed by the areas with high concentration defects, leading to the preferential graphitization. In the case of metal-coated one, a graphite layer was thermally induced on SCD surface via heat transition in the period of laser irradiation on metal film. In the following period of laser irradiation on the SCD substrate, the graphite layer was self-maintaining, and the material removal acted like a graphite piston sinking to the interior of SCD substrate. This study demonstrates the feasibility of MISG as a universal approach for avoiding interior damage during the laser ablation of SCD substrate.