The effects of optical absorption coefficient on dislocation behaviors of grain boundary induced by femtosecond laser ablation

摘要

Molecular dynamics simulations are conducted to study the influences of the optical absorption coefficient on the femtosecond laser ablation of polycrystalline materials in a nano-domain. Various parameters of laser incident energy and absorption coefficient are used to characterize the dynamical propagations and structural evolutions at the grain boundary (GB). Heterogeneous dislocation reactions induced by shock dynamics that nucleated from the solid-liquid interface and sequentially grew in target are observed. As the shock pressure penetrated through the GB, the dislocation emissions along various possible {111}<112> Shockley partials are examined via the quantitative dislocation-based analyses. The simulation results show that the large absorption coefficient produces a shallow ablation depth. Moreover, the large absorption coefficient can result in grain spallation and ejection in definite conditions, which significantly change the results of ablation yield and size distribution of the ejected clusters. The simulation results provide a better dynamic behavior characterization of how an ultra-fast laser interacts with polycrystalline materials. The presented model also embodies the notion inherent in short-pulsed laser spallation (or lift-off) techniques, and this is helpful for further investigations of the damage-free separation of various optoelectronic thin-films and heterostructures in semiconducting processes.