1. Sang-Pil Kim1,2, Kwang-Ryeol Lee1, Jae-Sung Kim3 and Yong-Chae Chung2
Conference on Computational Physics 2006
Molecular Dynamics Study on the Surface Structure Evolution of Au and Pd by High Energy Ar Bombardment
Sang-Pil Kim1,2, Kwang-Ryeol Lee1, Jae-Sung Kim3 and Yong-Chae Chung2
Future Technology Research Division, KIST, Seoul, Korea
Division of Advanced Materials Science Engineering, Hanyang University, Seoul, Korea
Department of Physics, Sook-Myung Women’s University, Seoul, Korea

2. Ion Bombardment (Sputtering)
Sputter deposition
Ion bombardment
Morphological evolution of the sputtered surface
 We focused on the structural evolution in Ion Bombardment
T.C. Kim et al., PRL 92, (2001).

3. Motivation
Makeev et al., Nucl. Instr. and Meth. in Phys. Res. B 197, 185 (2002).
From the value of a, σ and μ, morphology evolution could be generated from solving the continuum equations.
a : penetration depth of incident Ar atom
σ,μ : the widths of the distribution in directions parallel and perpendicular to the incoming beam
Atomic Mass
Crystal
Structure
Lattice
Parameter (Å)
Cohesive
Energy (eV)
Bulk Modulus (GPa)
Melting Point (K) Au
196.96
FCC
4.08
3.93
220
1337 Pd
106.42
3.891
3.91
180
1828
 We employed classical molecular dynamics simulation to investigated the details of the surface erosion behavior during high energy Ar bombardment on Au and Pd(001).

4. Calculation Procedure
81.6×81.6×102 (Å) for Au
77.8×77.8×97.28 (Å) for Pd
Dimension of Substrate
Incident angle ≈ normal angle
θ (tilt angle) = 1.3°, φ (twist angle) = 1.3°
Substrate : 300 K
 damping layer included
Ar : 0.5 keV
Force field
 EAM1) + ZBL2)
200 trials for each case
 Initial Ar positions were randomly selected within surface unit cell
LAMMPS3) (KIST modified)
S.M. Foiles et al., PRB 33, 7983 (1986).
J.F. Ziegler et al., The Stopping and Range of Ions in Matter, Pergamon, New York, (1985).

5. Penetration Depth* Au Pd Mean depth (Å) 6.12 5.52 Bounded Ar (%) 12.0
*Penetration Depth: maximum penetrated depth of Ar atom Au Pd
Mean depth (Å)
6.12
5.52
Bounded Ar (%)
12.0
4.0
Standard deviation
4.868
3.901

6. Impact Point Au(001) Pd(001) Bounded atoms: ◆  Top site
Unusual results: ▲  Off top site
Maximum depth: ●  Saddle site
Bounded atoms:★  Top site
Maximum frequency:▼  Off top site
Maximum depth:◆  Saddle site

7. Erosive Surface Distribution1 10 1 10
Frequencies at each point
Average sputtered atoms
 Au atoms, Pd atoms

8. Atomic Displacement Φ : normalized number of atoms
N(r) : number of atoms until distance r
S(r) : area until distance r

9. Calculation of Tm NPT ensemble Au: 1337 K, Pd: 1828 K
Experimental Value
Energy of melted atom
Au: 1337 K, Pd: 1828 K
Au: -3.4 eV, Pd: -3.2 eV

10. Energy Propagation  Melting region vanished very rapidly within 1 ps
0.5keV Ar on Au(001)
0.0
-3.4
Showing atoms only upper than -3.4 eV for Au, -3.2 eV for Pd of individual energy
0.1 ps
0.2 ps
0.3 ps
0.4 ps
1.0 ps
<001>
<110>
0.5keV Ar on Pd(001)
0.0
-3.2
0.1 ps
0.2 ps
0.3 ps
0.4 ps
1.0 ps
 Melting region vanished very rapidly within 1 ps

11. Energy Propagation: Au
Average melting atoms per each event
 Au atoms

12. Energy Propagation: Pd
Average melting atoms per each event
 Pd atoms

13. Summary > Au Pd 6.12 5.52 15.34 14.38 Energy propagation
Penetration depth (Å)
6.12
5.52
Surface diffusion length (Å)
15.34
14.38
> z x
Energy propagation
Au: Vertical direction > Horizontal direction
Pd: Vertical direction < Horizontal direction
Result in different surface erosion behavior
Distance from Ar stop position (A)