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Large-scale Atomistic Modeling of Laser-assisted Surface Nanostructuring

Large-scale Atomistic Modeling of Laser-assisted Surface Nanostructuring. Xinwei Wang Department of Mechanical Engineering The University of Nebraska – Lincoln Lincoln, NE 68588-0656 E-mail: xwang3@unl.edu Phone: 402-472-3089; Fax: 402-472-1465. Outline.

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Large-scale Atomistic Modeling of Laser-assisted Surface Nanostructuring

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  1. Large-scale Atomistic Modelingof Laser-assisted Surface Nanostructuring Xinwei Wang Department of Mechanical Engineering The University of Nebraska – Lincoln Lincoln, NE 68588-0656 E-mail: xwang3@unl.edu Phone: 402-472-3089; Fax: 402-472-1465

  2. Outline • Physical background: laser-assisted STM • Design and conduction of large-scale modeling • Unique physical phenomena discovered • Current and future work • Acknowledgment

  3. Physical background:laser-assisted STM STM tip Pulsed laser Enhanced optical field Si substrate ~10 nm

  4. Parallel Computation Enhanced optical field z y x .... ........ 1 2 3 36 4 35 18 19 Distribution of the computation domain on computing points. More than 200,000,000 atoms are modeled in the system to capture the physical process.

  5. Parallel Computation Prairie Wind 36 of the 52 computing points are used in the parallel MD simulation.

  6. Construction of Prairie Wind

  7. Completed and current projects • Thermal transport in nanoscale materials • Thermal transport in nanocrystalline materials • Thermophysical properties of single-wall silicon nanotubes • Surface nanostructuring using laser-assisted scanning tunneling microscope • Multi-laser beam open-air diamond coating • Long-time nanosecond-laser materials interaction

  8. Temperature Evolution (side view)

  9. Sub-surface Nanostructure

  10. Epitaxial re-growth

  11. Epitaxial re-growth

  12. Multi-scheme modeling of nanosecondlaser materials interaction thin Si (~nanometers) layer to provide the connection between the two domains Si wafer region experiencing phase change Si wafer domain I: finite difference method domain II: MD simulation Targeted computational time: 1 ms Targeted domain size: 2 mm

  13. Multi-laser energy open-airdiamond coating Velocity, pressure, specie concentration, and temperature are provided by the micro- to macroscopic modeling C atoms Diamond coating Substrate

  14. Acknowledgement • National Science Foundation (NSF) • Office of Naval Research • Air Force Office of Scientific Research • Office of Vice Chancellor for Research Nebraska Research Initiative (NRI) • Layman Foundation • Sumitomo Foundation

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