분자동역학을 이용한 금속표면의 Kinetic Roughening 현상에 대한 재 증착 효과 연구

1. 2007년 추계 금속재료학회 전산재료과학분과 심포지엄 분자동역학을 이용한 금속표면의 Kinetic Roughening 현상에 대한 재 증착 효과 연구 Sang-Pil Kim1,2, Kwang-Ryeol Lee1, Jae-Sung Kim3 and Yong-Chae Chung2 • Computational Science Center, 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, 246104 (2001).

3. Kinetic Roughening (Patterning)  “Quantum dots” on GaSb, fabricated by normal-incidence sputter patterning using 420 eV Ar+. Dots sizes ~ 15 nm. Under some conditions of uniform ion irradiation, spontaneously-arising sputter pattern topography arises that takes the form of 1-D ripple or 2-D arrays of dots. Facsko et al., SCIENCE (1999)

4. Theoretical Approach Sigmund’s theory • Limitation in linear theory Agreement: ripple formation/ orientation Disagreement: wavelength coarsening, multi-ion beam sputtering • Toward improvement Nonlinear terms considered New terms included to the equation (ex. shadowing effect, surface anisotropy, re-deposition effect…)

5. Ion Sputtered atoms Adatoms (or redeposited atoms) Re-deposition Effect Sputtering Process  Erosion (conventional concept) Sputtering Process  Erosion + Redeposition 10 keV Ar ion impacts on Au(001)

6. Ar+ Ion Au & Pd(001) Materials 0.5 keV Incident Energy 0, 30, 45, 60, 75° Incident Angle(Ө)  Φ = 0° Calculation Procedure • Temperature: 300 K  damping layer included • Force field •  EAM1) + ZBL2) • 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).

7. Sputter Yield & Redeposition

8. Sputter Yield vs. Redeposition

9. Redeposition Distribution Au

10. Redeposition Distribution Pd

11. Summary & Future works • The effect of redeposition clearly shown on Au, Pd surface. • From MD calculation, we could obtain quantitative parameters of redeposition effect (ratio, distribution). • Based on MD calculation, we could improve kinetic roughening equation. + α