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금속이 혼입된 비정질 탄소막 (Me-DLC) 에서의 응력감소 거동 ; 실험적 분석과 제일원리계산

금속이 혼입된 비정질 탄소막 (Me-DLC) 에서의 응력감소 거동 ; 실험적 분석과 제일원리계산. 23, Sep., 2005 KAIST. 열역학분과 심포지엄. 한국과학기술연구원 미래기술연구본부 최정혜 , 안효신 , 이승철 , 왕애영 , 이광렬. Diamond-like carbon (DLC) films. High hardness High wear resistance Low friction coefficient Optical transparency Chemical inertness

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금속이 혼입된 비정질 탄소막 (Me-DLC) 에서의 응력감소 거동 ; 실험적 분석과 제일원리계산

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  1. 금속이 혼입된 비정질 탄소막(Me-DLC)에서의 응력감소 거동;실험적 분석과 제일원리계산 23, Sep., 2005 KAIST 열역학분과 심포지엄 한국과학기술연구원 미래기술연구본부 최정혜, 안효신, 이승철, 왕애영, 이광렬

  2. Diamond-like carbon (DLC) films • High hardness • High wear resistance • Low friction coefficient • Optical transparency • Chemical inertness • Smooth surface • Bio-compatibility • Protective coating • Bio materials Video Head Drum Coronary Artery Stent Hard disk Hip Joint

  3. Before deposition After deposition Disadvantages of DLC films High residual compressive stress (6~20 GPa) poor adhesion Hard disk Substrate bending Delamination M. W. Moon, Acta Mater., 50 219 (2002).

  4. Stress and sp3 bond fraction Hardness

  5. To reduce residual scomp in DLC films • Substrate biasing • Post-annealing • Metal atom incorporation ; Ti, W, Mo, Cr, Al….

  6. 1.9 at % W W-incorporated DLC films Mechanism ? Not fully understood yet !!! A.-Y. Wang APL 86 111902 (2005).

  7. 109.5o Diamond ; ideal sp3 bonding Purpose of this work ≠109.5o DLC ; distorted sp3 + sp2, sp bonding Known as a primary cause of the residual stress in DLC structure dependency of total energy of the system on the bond angle & the electron density distribution and its effects on the stress reduction behavior of DLC films

  8. 109.5o 109.5o Me C 90o~ 130o 90o~ 130o C Me Tetrahedron bond model • tetrahedral bonding of • carbon(or Me)-carbon • structure relaxation • total energy calculation ; reference state DEMe-C DEC-C • Bond angle distortion • bond distance relaxation • total energy calculation

  9. Calculation condition • Code; DMOL3 • Exchange-correlation potential; GGA (PBE) • Atomic orbital; double-zeta polarization basis set • Cutoff radiusof atomic orbitals; 9 Å • All electron calculation • Spin consideration

  10. Total energy change by the bond angle distortion

  11. Me Me Formation energy of Me-C tetrahedron DEfM-C = (EtotM-C + EatomC) - (EtotC-C + EatomM) DEfM-C

  12. 0.5 1.0 1.0 1.5 109.5o C 1.5 90o 0.5 C Isosurface of electron density; C-C-tetrahedron Inset values are the electron density [Å-3] of the isosurface

  13. Mn 0.70 Mo 0.72 109.5o Fe 0.82 Cr 0.72 C 1.50 Ni 0.67 Co 0.76 V 0.63 Si 0.72 Ti 0.64 W 0.70 Isosurface of electron density right before it is separated

  14. Ag 0.40 Au 0.40 109.5o Al 0.45 Cu 0.53 Cd 0.36 C 1.50 Pd 0.58 Ar 0.01 Zn 0.45 Isosurface of electron density right before it is separated

  15. Electron density right before its isosurface is separated (res) • Weaker bonding • Lower angular dependency • of total energy •  stress reduction • Lower res • Lower shape anisotropy • of electron density

  16. C 1.50 W 0.70 W-incorporated DLC films

  17. Hardness Residual stress Young’s modulus Me-DLC films; Experimental By FCVA P. Zhang, J. Vac. Sci. & Tech. A. 20 390 (2002).

  18. Mn 0.70 Au 0.40 Al 0.45 C 1.50 Conclusion

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