The crack propagation and surface formation mechanism of single crystalline diamond by a nanosecond pulsed laser

In this article, the surface formation mechanism of single crystalline diamond (SCD) by a nanosecond pulsed laser is performed, where surface cracking, phase transformation, and typical surface morphology are involved. The nanometric surface characteristics of the ablated micro-grooves on the diamond caused by the thermal effect are first studied, where the crack generation and propagation are discussed by the thermoelastic bending model for the laser irradiation process. In addition, the composed phases and the formation mechanism of the induced metamorphic layer (IML) and deposited metamorphic layer (DML) near the ablated groove are investigated, where the diamond/graphite transition layer is the coexistence of the distributed crystalline diamond and the oriented graphite, the direction of which is at an angle of 60°–80° to the laser scanning direction and toward the center of the ablated groove. Based on the subsurface exploration and the grain growth kinetics analysis, the formation process of the DML is proposed as follows: the nucleation → the formation of carbon islands → the combination of the carbon islands → the formation of the deposited metamorphic layer.