Microscopic spallation mechanisms induced by a pulse laser at the solid-state interface

This paper presents a study of the transient behavior of structural dynamics and the associated innovatory microscopic spallation mechanism at the solid-state interface, induced by an incident femtosecond pulse laser. By detailed structural dynamic analysis, using the technique of molecular dynamics simulation, the spallation mechanism at the solid–solid interface is observed. The occurrence of structural spallation is mainly characterized by extraordinary expansion dynamics and tensile stress that induces interior structural void defect coalescence, eventually leading to cracking. The microscopic phenomenon of moderate ductile fracturing at the solid–solid interface is identified. A high strain rate in the order of 10⁹ s^-1 is observed. Both aforementioned phenomena are analogous to the experimental results of metal-film spallation excited by a pulse laser. Moreover, it is also shown that the critical value of the stain rate is one of the dominant factors that influences the occurrence and mechanism of structural spallation. The results of simulations reveal that the thin-film structure is safe if the strain rate is below certain critical values. The critical damage threshold is evaluated and technical suggestions to avoid interfacial fracture are also presented. PACS 02.70.Ns; 42.62.-b; 64.60.Ht; 61.72.Cc; 64.60.-i