Research Activities > Programs >
Nonequilibrium Interface Dynamics > Workshop 1
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CSIC Building (#406),
Seminar Room 4122.
Directions: home.cscamm.umd.edu/directions
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Laser Ablation and Deposition of Metals: Large-Scale Molecular Dynamics Simulations
Dr. George H. Gilmer
Lawrence Livermore National Laboratory
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Abstract:
We have simulated short-pulse ablation of metals using continuum and molecular dynamics models, and
performed experiments to examine ablated surface structures. The interaction of the light with the
electrons and the subsequent equilibration of the electrons with the ions during the first picosecond
are modeled using a one-dimensional continuum model. The molecular dynamics model then takes the
output from the continuum, and follows the process for about 200 picoseconds, where the sudden heating
of the metal atoms leads to a variety of morphologies. Our purpose is to investigate the mechanisms
leading to the rough surfaces observed in the experiments, and to the ejection of micron-sized
particles. A rich diversity of phenomena is observed as a function of the pulse energy density,
including: (i) a low energy regime with a minute ablation flux corresponding to evaporation of atoms
from the hot metal surface; (ii) an intermediate regime where void nucleation and growth, or spall,
causes the ejection of a stable liquid layer and particles, and (iii) high pulse energies where
liquid droplets are ejected with a wide range of sizes. Experimental observations of interference
fringes during short-pulse ablation are in excellent agreement with our simulations that show the
ejection of a liquid layer. We discuss some implications of the experiments and simulations for the
laser machining of fine-scale surface features on metal objects. Pulsed laser deposition of thin
films is discussed, using Monte Carlo models of thin film growth to help understand the effects of
the ejected material on thin film structures. The simulations of the dynamics of short-pulse
ablation are illustrated by mpeg movies.
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