Irradiation characteristics of nanosecond laser on silicon under vacuum conditions

To investigate the influence of the vacuum environment on the near-infrared nanosecond pulse laser irradiation of silicon materials, irradiation effects such as the distribution and evolution of the microstructure, as well as the erosion morphology of silicon under various vacuum levels, are investigated. The experimental results show that when the laser energy density is low, silicon's temperature rises and volume expands due to the laser energy absorption, resulting in thermal stress within the irradiation area and the appearance of cracks on the surface. As the laser energy density increases, a molten pit appears at the ablation center, and the size of the molten pit increases with the energy density, resulting in a significant increase in the damaged area. The damage diameter decreases with the vacuum level. However, the effect of vacuum level on the damage diameter is not significant when the excitation energy density is low. The damage area of monocrystalline silicon increases approximately linearly with the laser repetition rate. Laser absorption is primarily Finier absorption in high vacuum conditions, whereas reverse toughening absorption is predominant in low vacuum conditions. This study can be used as a reference for surface treatment, drilling, and development of new monocrystalline silicon materials.