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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 1. Computational Science Center, KIST, Seoul, Korea 2. Division of Advanced Materials Science Engineering, Hanyang University, Seoul, Korea 3. Department of Physics, Sook-Myung Women’s University, Seoul, Korea 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). Kinetic Roughening (Patterning) “Quantum dots” on GaSb, fabricated by normalincidence sputter patterning using 420 eV Ar+. Dots sizes ~ 15 nm. Facsko et al., SCIENCE (1999) 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. 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…) Re-deposition Effect Ion Sputtering Process Erosion (conventional concept) + Redeposition Sputtered atoms Adatoms (or redeposited atoms) 10 keV Ar ion impacts on Au(001) Calculation Procedure Ion Ar+ Materials Au & Pd(001) Incident Energy 0.5 keV Incident Angle (Ө) 0, 30, 45, 60, 75° Φ = 0° Temperature: 300 K damping layer included Force field EAM1) + ZBL2) 1) 2) 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). Sputter Yield & Redeposition 20 Redeposition Yield (atoms/ion) Sputtering Yield (atoms/ion) 4 3 2 0.5keV Ar 1 Au Pd 0 16 12 8 0.5keV Ar 4 Au Pd 0 0 10 20 30 40 50 60 Incident Angle (degrees) 70 80 90 0 10 20 30 40 50 60 Incident Angle (degrees) 70 80 90 Sputter Yield vs. Redeposition 6.0 5.5 Ratio = Yredeposition / YSputtering 5.0 Au Pd 4.5 Ratio 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0 10 20 30 40 50 60 Incident Angle (degrees) 70 80 90 Redeposition Distribution 60 Au 0.5keV Au 30 0.5keV Au Normal 40 Y 20 0 -20 -40 -60 60 -60 -40 -20 0 20 40 60 40 Y 20 0 -20 -40 0.5keV Au 60 0.5keV Au 45 -60 -60 -40 -20 0 X 20 40 -60 60 -40 -20 0 Y 20 40 60 Redeposition Distribution 60 Pd 0.5keV Pd Normal 0.5keV Pd 30 0.5keV Pd 45 0.5keV Pd 60 40 Y 20 0 -20 -40 -60 60 40 Y 20 0 -20 -40 -60 -60 -40 -20 0 X 20 40 -60 60 -40 -20 0 X 20 40 60 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