An interior damage free approach for nanosecond pulsed laser ablation of single crystal diamond 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 a ∼ 100-nm-thick metal film on an SCD substrate. Experiments involving laser irradiation of metal films, such as Au-, Al-, Ti-, and Pt-coated SCD substrates, revealed that the material removal depths were the same when the output power was the same and that the surface was covered by graphite after laser irradiation. In addition, the laser-induced damage to the upper or lower surface in the case of the uncoated SCD substrate disappeared. A semitransparent model based on Beer-Lambert law and an opaque model based on modified Level-Set method were built to simulate laser irradiation on uncoated and metal–coated SCD substrates. In the case of the uncoated sample, the laser energy was largely absorbed by the areas with high-concentration defects, leading to preferential graphitization. In the case of the metal-coated sample, a graphite layer was thermally induced on the SCD surface via heat transition during the period of laser irradiation of the metal film. Subsequently, the graphite layer was self-maintaining, and the material removal acted like a graphite piston sinking to the interior of the SCD substrate. This study demonstrates the feasibility of MISG as a universal approach for avoiding interior damage during laser ablation of SCD substrates.