Study of ablation depth of monocrystalline silicon irradiated by long pulse laser

In order to explore the erosion morphology and mechanism of monocrystalline silicon irradiated by a laser, an experimental system of millisecond pulsed laser acting on monocrystalline silicon sample was built, and corrosion model was established. The mass conservation of the fluid mechanics, the momentum conservation, and the energy conservation equations were used to describe the entire computational domain. The fluid volume method and the narrow-band level set method were combined to improve the level set control equation. The research shows that after the monocrystalline silicon melts, a molten pool is generated, and a protruding peak structure appears in its center. The laser energy is mainly concentrated at the bottom of the ablation pit. The higher energy density laser acts on the monocrystalline silicon by instantly generating a high temperature. A large recoil pressure is present at the bottom of the pit and causes the molten fluid to flow upward, whereas the viscous shear force and the surface tension make the fluid flow downward. The combination of the opposite flow and the collisions generated such peak structure in the pit. As the laser energy density increases, the presence of the crater shows the ablation morphology change on the sample, the degree of the ablation damage increases, as well as the ablation area. For a fixed laser energy density, as the pulse width increases, the laser power density decreases and the erosion depth and erosion radius decrease. During the re-coagulation process of monocrystalline silicon, ring ripples are formed on its surface. As the number of pulses increases, the laser damage area increases, and the ablation depth increases rapidly with the number of pulses. The experimental and the simulation results are in good agreement. The experimental research carried out verifies the simulation model. This study provides a reference for improving the laser system and broadening its application in scientific research and production.