1. 분자동역학 모사를 통한 비정질 탄소 필름의 원자구조 해석 : RDF를 중심으로
이 승 협, 이 승 철, 이 광 렬
KIST 미래기술연구본부
KIST Beamline User Workshop ( )

2. Diamond-like Carbon Amorphous Solid Carbon Film
Mixture of sp1, sp2 and sp3 Hybridized Bonds
High Content of Hydrogen (20-60%)
Synonyms
(Hydrogenated) amorphous carbon (a-C:H)
i-Carbon
Tetrahedral Amorphous Carbon (ta-C)
Heart valve
Hard disk

3. 2-D Analogy of Structure
ta-C

4. High Residual Compressive Stress
Film Deposition

5. Stress Reduction by Si Incorporation
C.-S. Lee et al, Diam. Rel. Mater., 11 (2002)
S.-H. Lee et al, to be Submitted (2005)

6. Molecular Dynamics Simulation
Deposited atoms
created on this plane
Hybrid Force Field
Brenner force field for C-C bonds
Tersoff force field for C-Si and Si-Si bonds
Diamond substrate : 6a0 x 4.75a0 x 6a0
1,368 atoms with 72 atoms per layer
Deposition
Total 2,000 atoms
Incident Kinetic Energy : 75 eV for both C and Si
Si concentration : 0.5 % ~ 20 %
Fully
Relaxed
Layer
Fixed Layer

7. Snapshots after Deposition
0.0 %
3.0 %
0.5 %
5.0 %
1.0 %
10.0 %
2.0 %
20.0 %

8. Atomic Stress Analysis
300 K
Atomic Level Stress Tensor

9. Residual Compressive Stress
Experiment : C.-S. Lee et al, Diam. Rel. Mater., 11, 198 (2002).

10. Atomic Bond Structure MD Simulation Raman G-peak Position
Experiment : C.-S. Lee et al, Diam. Rel. Mater., 11 (2002)

11. Radial Distribution Function
Crystalline Diamond
2.54 Å
1.54 Å

12. Radial Distribution Function

13. Radial Distribution Function

14. Radial Distribution Function

15. Bond Angle Distribution

16. Conclusions
Various properties of a-C films generated by MD simulation agrees well with those of experimentally obtained a-C films.
Brenner force field for C-C bond
Tersoff force field for Si-Si and Si-C bond
Stress reduction mechanism was suggested based on the atomic scale structure analysis.
Small amount of Si incorporation in a-C network effectively relaxes the distorted bonds.
Direct comparison with experimental data will be possible if we obtain the radial distribution function of a-C films.