Effects of laser fluence on near-field surface nanostructuring

In this work, molecular dynamics simulation is performed to explore the long-time (up to 5 ns) behavior of argon crystal in surface nanostructuring with an extremely localized near-field laser beam. The surface nanostructuring region is limited to tens of nanometers in diameter, although the simulated systems are much larger (comprised of more than 770,000 atoms). This study focuses on the long-time solidification and crystallization procedure, which is driven by the heat conduction in the material. The effect of the computational domain on the final nanostructure is studied in detail. Different laser fluences are used in the simulation to explore how and to what extent the energy input affects the dynamic melting behavior and the final dimension and profile of the surface nanostructure. In-depth theoretical investigation gives satisfactory explanation of the effect of the laser fluence on the melting depth. Spot-like structural defects in the sub-surface region are observed and investigated until full solidification.