Molecular dynamics investigation to identify Al atomic behavior on various Cu surfaces

1. Molecular dynamics investigation to identify Al atomic behavior on various Cu surfaces 2007. 2. 6 김상필1,2, 김영근3, M. Sahashi4, 이광렬1, 정용재2 1한국과학기술연구원 계산과학센터, 2한양대학교 신소재공학부3고려대학교 신소재공학부, 4Dept. of Electronic Eng., Tohoku University

2. Downward funneling model PRL 62, 921 (1989). • Transient mobility model PRB 41, 5410 (1990). • Impact cascade diffusion model •  PRB 57, 6685 (1998). • Anomalously intermixing PRB 66, 104427 (2002). ES* barrier a b : Atomic-scale Thin Film Growth As the scale of device goes down to an atomic level… Conventional concepts Various & complex diffusion behaviors

3. Research Strategy Atomic scale deposition behavior Morphology & Diffusion path Fundamental understanding Surface diffusion barrier calculation  Using Molecular Dynamics & Statics method

4. EAM Potentials for Al-Cu System* “Simple analytic embedded-atom-potential model including a long-range force for fcc metals and their alloys”, J.Cai and Y.Y. Ye, Phys. Rev. B 54 8398 (1996). FCC L12 L10 *Al, Cu is the source material of GMR device

5. Simulation Procedure Deposition Behavior Calculation  Molecular Dynamics (MD) Normal incidence • Cu surface (100), (110), (111) • (clean & with plateau surface) • Substrate Temp. : 300K • Incident Energy with normal incidence 0.1 eV Diffusion Energy Barrier Calculations  Molecular Statics MD results (position, path) Following the diffusion path

6. Cu surface atoms Cu plateau atoms Al deposit atoms 0.5ML Al on Cu(100) With plateau Clean surface

7. B3 B2 B5 B4 B1 B7 B8 B6 B9 Energy Barriers for Surface Diffusion* – (100) B1: Surface diffusion B2: Away from the step B3: Toward the step B4: Along the step B5: Upward diffusion B6: Away from the step on plateau B7: Along the step on plateau B8: Downward diffusion B9: Ehrlich-Schwoebel (ES) Energy Barrier [eV] W. Zhu et al., PRL 92, 106102 (2004), S. Durunkanoglu et al., PRB 73, 125426 (2006), X.F. Gong et al., TSF 493. 146 (2005), H. Yildirim et al., Surf. Sci. 600, 484 (2006). *Various Surface Barriers

8. Energy Barriers for Surface Diffusion Surface & Step B3 B2 B4 B1

9. Energy Barriers for Surface Diffusion Step & Plateau B5 B7 B8 B6 B9

10. Cu surface atoms Cu plateau atoms Al deposit atoms 0.5ML Al on Cu(111) Clean surface With plateau

11. Energy Barriers for Surface Diffusion – (111) B1: Surface diffusion for fcc hcp site B2: Surface diffusion for hcp  fcc site B3: Along the step B4: Away from the step (two steps) B5: Toward the step B6: Away from the step on plateau B7: Ehrlich-Schwoebel (ES) barrier B8: Downward diffusion B9: Upward diffusion B1 B7 B8 B4 B3 B6 B5 B9 Energy Barrier [eV] * Spontaneous reaction

12. Energy Barriers for Surface Diffusion Surface & Step B1 B4 B3 B5 * Spontaneous reaction

13. Energy Barriers for Surface Diffusion Step & Plateau B7 B8 B6 B9 * Spontaneous reaction

14. Cu plateau atoms & same height with plateau atoms Cu surface atoms Al deposit atoms 0.5ML Al on Cu (110) Clean surface With plateau

15. Energy Barriers for Surface Diffusion – (110) B1: Perpendicular to the open channel B2: Along the open channel B3: Along the step (perpendicular to the open channel) B4: Away from the step B5: Toward the step B6: Upward diffusion B7: Along the step (along the open channel) B8: Along the open channel on the plateau B9: Perpendicular to the open channel on the plateau B10: Downward diffusion B11: Ehrlich-Schwoebel (ES) B12: Exchange B1 B2 B4 B5 B3 B11 B10 B7 B6 B9 B12 B8 Energy Barrier [eV]

16. Energy Barriers for Surface Diffusion B1 B2 B4 B5 B3 B11 B10 B7 B6 B9 B12 B8 Diffuse along the open channel(B2, B7, B8) or exchange mixing behavior (B12)

17. Summary Deposition behavior and surface diffusion barrier calculation were investigated using by Molecular Dynamics, Statics. (111) (100) (110) • Along the step • Downward diffusion • Toward the step • Downward diffusion • Away from the step on plateau • Along the open channel • Exchange mixing  This set of results can be used as input in KMC simulations.