Microscopic and macroscopic modeling of femtosecond laser ablation of metals

ME Povarnitsyn and VB Fokin and PR Levashov, APPLIED SURFACE SCIENCE, 357, 1150-1156 (2015).

DOI: 10.1016/j.apsusc.2015.09.131

Simulation of femtosecond laser ablation of a bulk aluminum target is performed using two complementary approaches. The first method is single-fluid two-temperature hydrodynamics (HD) completed with a two- temperature equation of state (EOS). The second approach is a combination of classical molecular dynamics (MD) and a continuum model of a free electron subsystem. In both methods, an identical and accurate description of optical and transport properties of the electron subsystem is based on wide-range models reproducing effects of electron heat wave propagation, electron-phonon/ion coupling and laser energy absorption on a time-dependent profile of the dielectric function. For simulation of homogeneous nucleation in a metastable liquid phase, a kinetic model of nucleation is implemented in the HD approach. The phase diagrams of the EOS and MD potential are in good agreement that gives opportunity to compare the dynamics of laser ablation obtained by both methods directly. Results of simulation are presented in the range of incident fluences 0.1-20 J/cm(2) and match well with experimental findings for an ablation crater depth. The MD accurately reproduces nonequilibrium phase transitions and takes into account surface effects on nanoscale. The HD approach demonstrates good qualitative agreement with the MD method in the dynamics of phase explosion and spallation. Other advantages and disadvantages of both approaches are examined and discussed. (C) 2015 Elsevier B.V. All rights reserved.

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