1. Multiscale Modeling and Simulation of Nanoengineering:
Challenges and Opportunities
DISTANCE
TIME
Angstrom
meters
femtosec
hours QM MD
MESO
Continuum
Atoms Engineering

2. Computational Nanoscience and Nanoengineering
Nanotechnology:
Computational Nanoscience and Nanoengineering
Molecule Nano Micro Meso Macro
Length (m):
The physical systems are
too small for direct measurements,
too large to be described by current first principles QM
too few to be described by a statistical ensemble
Fundamental understanding and highly accurate predictive methods are critical to successful manufacturing of nanostructured materials, devices, and systems

3. Assembly of Nanostructures (Bottom-Up)
Quantum dots (AFM)
Nanowire
Nanowire network (STM)
Quantum dots
Unique physical and chemical properties are determined by their structural properties.

4. Nanoscale Electronic Devices (Top-Down)
Existing materials and technologies are approaching to their physical limits as device sizes decrease significantly below 100 nm
New Materials & Processes
Nanoscale devices (New Device Concepts):
single electron, quantum tunneling
Year of Production:
DRAM half-pitch (nm)
CD control (nm)
Oxide thickness (nm)
Junction depth (nm):
Inter-metal dielectric < <1.5
no known solutions

5. Complexity in Nanoengineering
Gas-solid and liquid-solid interactions
Solid-solid interfacial interactions
Defect-dopant dynamics
+ V
Vacancy annihilation
at the Si/SiO2 interface
Kirichenco & Hwang, to be submitted
gain B
H2O adsorption
on B-modified surface
Wang & Hwang, Surf. Sci., in press (2003) O Si
a-SiO2 on c-Si
Yu and Hwang, AVS (2002)

6. Ultrashallow Junction Formation
Computational Nanoengineering
Ultrashallow Junction Formation
Shallow vertical depth
Lateral abruptness
High doping level (> 1020 cm-3)
Technology :
node nm nm nm nm nm
Junction depth:
(nm)

7. Multiscale approach: strategy
Experiment
100 B+
200
300
400
500
600
700
Depth, Å
B concentration, cm-3
1021
1022
1020
1019
1018
as implanted
after annealing (> sec) Si
explanation/
prediction
Mesoscale simulation
Kinetic Monte Carlo
Continuum model
[long time (>1 sec)]
validation
fundamental data
density functional theory
tight binding MD
classical MD
[short time (< nsec)]
Atomic-scale calculation

8. Si Nanocrystal Synthesis in an Oxide Matrix:
Computational Nanoengineering
Si Nanocrystal Synthesis in an Oxide Matrix:
Size and shape
Spatial distribution
Si-SiO2 interface
SiO2
nc-Si
Yun et al, Thin Solid Films 375, 137 (2000)

9. nc-Si/Ge in SiO2 SiO2 Ge Si Flash memory
Electronic devices (floating gate)
Optical devices
10 nm Si Ge
SiO2
Flash memory
Source
Drain
Nano-
crystals
Tunnel oxide
Control oxide
Gate

10. Multiscale Modeling of Nanoengineering
Its success will offer tremendous opportunities for guiding the rational design and fabrication of a variety of nanosystems!
Atomistic
behaviors
physical
understanding
quantitative
prediction
Structural
Properties
Fundamental processes,
Atomic structures,
Energetics, ….
Shape, Size distribution,
Spatial distribution,
Interface structures, ….
Time (sec):
Length (m):
Molecular
Dynamics
Statistical
Mechanics
Continuum
Mechanics
Quantum
Mechanics

11. III. Metal growth on a binary metal-oxide
Au on TiO2 (110)
Pillay and Hwang

12. Ni, Fe, Co IV. Carbon Nanotube(fiber) Growth by PECVD Feed Gases:
C2H2, NH3
(100)
(110)
(111)
Ni, Fe, Co
C2H2 / NH3
(a) 0.38
(b) 0.50
(c) 0.59
(d) 0.75

13. V. Electrochemical Micro/Nano-machining
Kenney and Hwang + -
tool
workpiece
A: transport of solvated
molecules and ions
B: double layer physical
nature and its charging
and discharging dynamics
C: electrochemical reactions
on an electrode surface.