Anisotropic ablation mechanism of single crystal diamond surface in ultrafast laser processing: A molecular dynamics study

Ultrafast laser ablation mechanism of the single crystal diamond surface (SCD) is essential for controlling the micro-nanostructured morphology, but it has been unclear how the crystalline orientation affects the surface ablation mechanism. Hence, an improved two-temperature model is proposed in coupling molecular dynamics (MD) to perform the non-equilibrium energy conduction between diamond and ultrafast laser. The objective is to reveal the atomic-scale phase transition, surface structure evolution, and mechanical property on ultrafast laser processed SCD. Firstly, the atomic evolution of ultrafast laser ablation of SCD was studied by MD simulation. Then the ultrafast laser was performed on SCD surface. Finally, Raman spectra and X-ray photoelectron spectroscopy were employed to verify MD simulation. It is shown that the diamond (1 1 1) and (1 0 0) surfaces are mainly removed by graphitization and amorphous carbon, respectively. The ablation thresholds of diamond (1 1 1) and (1 0 0) surfaces were calculated by the proposed novel MD simulation prediction method to be 2.33J·cm⁻² and 3.29 J·cm⁻² respectively, which is consistent with the experimental results. The microgroove depth on diamond (1 1 1) surface is greater than that on (1 0 0) surface with the same laser power. Moreover, the elastic modulus and tensile strength decrease significantly with the increase of ablation degree.