Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Large-scale Atomistic Modelingof Laser-assisted Surface Nanostructuring

Xinwei WangDepartment of Mechanical EngineeringThe University of Nebraska – Lincoln

Lincoln, NE 68588-0656

E-mail: xwang3@unl.edu

Phone: 402-472-3089; Fax: 402-472-1465

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Outline

Physical background: laser-assisted STM Design and conduction of large-scale

modeling Unique physical phenomena discovered Current and future work Acknowledgment

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Physical background:laser-assisted STM

STM tipPulsed laser

Si substrate

Enhanced optical field

~10 nm

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Parallel Computation

Enhanced optical field

x

y

z

1 2 3 36354 19.... 18 ........

Distribution of the computation domain on computing points.

More than 200,000,000 atoms are modeled in the system to capture the physical process.

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Parallel Computation

36 of the 52 computing points areused in the parallel MD simulation.

Prairie Wind

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Construction of Prairie Wind

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

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

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Temperature Evolution (side view)

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Sub-surface Nanostructure

Solid

Liquid

Nano-droplet

Stress-induced structural damageBent lattice structure

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Epitaxial re-growth

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Epitaxial re-growth

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Multi-scheme modeling of nanosecondlaser materials interaction

Si wafer

domain II: MD simulation

domain I: finitedifference method

thin Si (~nanometers) layer to provide the connection between the two domains

Si wafer region experiencing phase change

Targeted computational time: 1 s

Targeted domain size: 2 mm

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

Multi-laser energy open-airdiamond coating

Substrate

Diamondcoating

C atoms

Velocity, pressure, specie concentration, and temperature are provided by the micro- to macroscopic modeling

Micro/Nanoscale Thermal Science Laboratory • Department of Mechanical EngineeringURL: http://www.engr.unl.edu/~nanolab

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