금속이 혼입된 비정질 탄소막 (me-dlc) 에서의 응력감소 거동 ; 실험적 분석과...
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23, Sep., 2005KAIST
금속이 혼입된 비정질 탄소막(Me-DLC) 에서의 응력감소 거동
; 실험적 분석과 제일원리계산
한국과학기술연구원 미래기술연구본부
최정혜 , 안효신 , 이승철 , 왕애영 , 이광렬
열역학분과 심포지엄
Diamond-like carbon (DLC) films
• High hardness
• High wear resistance
• Low friction coefficient
• Optical transparency
• Chemical inertness
• Smooth surface
• Bio-compatibility
• High hardness
• High wear resistance
• Low friction coefficient
• Optical transparency
• Chemical inertness
• Smooth surface
• Bio-compatibility
Hard disk Video
Head DrumCoronary
Artery Stent Hip Joint
• Protective coating • Bio materials
• Protective coating • Bio materials
Disadvantages of DLC films
Hard disk
Before deposition
After deposition
M. W. Moon, Acta Mater., 50 219 (2002).
High residual compressive stress
(6~20 GPa)
High residual compressive stress
(6~20 GPa)poor adhesionpoor adhesion
Substrate bending Delamination
Stress and sp3 bond fraction
2 4 6 8 10 1210
20
30
40
50
60
70
80
90
100
Fallon Weiler Xu Chhowalla
sp
3 f
ractio
n
Residual Compressive Stress (GPa)
Hard
nes
Hard
nes
ss
To reduce residual comp in DLC films
• Substrate biasing
• Post-annealing
• Metal atom incorporation
; Ti, W, Mo, Cr, Al….
W-incorporated DLC films
1.9 at % W
A.-Y. Wang APL 86 111902 (2005).
Not fully understood yet !!!
Mechanism ?
Purpose of this work
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
DLC; distorted sp3 + sp2, sp bonding
Diamond ; ideal sp3 bonding
109.5o
≠109.5o
Known as a primary cause of the residual stress in DLC structure
Known as a primary cause of the residual stress in DLC structure
Tetrahedron bond model
tetrahedral bonding of carbon(or Me)-carbon structure relaxation total energy calculation ; reference state
tetrahedral bonding of carbon(or Me)-carbon structure relaxation total energy calculation ; reference state
Bond angle distortion bond distance relaxation total energy calculation
Bond angle distortion bond distance relaxation total energy calculation
109.5o
Me
90o~130o
Me
90o~130o
C
109.5o
C
EC-C EMe-C
Calculation condition
Code; DMOL3
Exchange-correlation potential; GGA (PBE)
Atomic orbital; double-zeta polarization basis set
Cutoff radius of atomic orbitals; 9 Å
All electron calculation
Spin consideration
Total energy change by the bond angle distortion
3 4 5 6 7 8 9 10 11 12 13 14 15-1
0
1
2
Fe
Mn
V
ZnCd AlNi
Pd
Co
CuAgAu
MoCrW
Ti
Si
C
E90
o (e
V)
atomic group (# of valence e-)
2nd period 3rd period 4th period 5th period 6th period
Formation energy of Me-C tetrahedron
3 4 5 6 7 8 9 10 11 12 13 14 15
0
2
4
6
8
10
12
14
C
Si
Al
CdZn
AuAg
CuPd
NiCo
Fe
2nd period 3rd period 4th period 5th period 6th period
MnCrMoW
V
Ti
Ef M
e-C(e
V)
atomic group (# of valence e-)
EfM-C = (Etot
M-C + EatomC) - (Etot
C-C + EatomM)Ef
M-C = (EtotM-C + Eatom
C) - (EtotC-C + Eatom
M)
Me
Me
EfM-C
Isosurface of electron density; C-C-tetrahedron
90o
C
1.51.00.5
Inset values are the electron density [Å-3] of the isosurface
109.5o
C
0.5 1.51.0
Isosurface of electron density right before it is separated
Cr 0.72
109.5o
V 0.63 Ti 0.64 Ni 0.67 Si 0.72
Mo 0.72W 0.70Mn 0.70
Co 0.76 Fe 0.82 C 1.50
Isosurface of electron density right before it is separated
109.5o
Ar 0.01 Cd 0.36 Ag 0.40 Au 0.40
Pd 0.58Cu 0.53Zn 0.45Al 0.45
C 1.50
Electron density right before its isosurface is separated (e
s)
Lower es
Lower shape anisotropy of electron density
Lower es
Lower shape anisotropy of electron density
Weaker bonding Lower angular dependency of total energy stress reduction
Weaker bonding Lower angular dependency of total energy stress reduction
3 4 5 6 7 8 9 10 11 12 13 14 150.2
0.4
0.6
0.8
1.4
1.6
C
Al
Si
ZnCd
CuAg/Au
NiPd
CoFe
MnV
Cr/Mo WTi
Ti
2nd period 3rd period 4th period 5th period 6th period
atomic group (# of valence e-)
es (A
-3)
W-incorporated DLC films
W 0.70C 1.503 4 5 6 7 8 9 10 11 12 13 14 15
-1
0
1
2
Al
AgAu
W
Si
C
E90
o (e
V)
atomic group (# of valence e-)
Me-DLC films; Experimental
P. Zhang, J. Vac. Sci. & Tech. A. 20 390 (2002).
Residual stress
By FCVA
Hardness
Young’s modulus
Conclusion
3 4 5 6 7 8 9 10 11 12 13 14 15-1
0
1
2
Fe
Mn
V
ZnCd AlNi
Pd
Co
CuAgAu
MoCrW
Ti
Si
C
E90
o (e
V)
atomic group (# of valence e-)
2nd period 3rd period 4th period 5th period 6th period
C 1.50 Mn 0.70
Au 0.40 Al 0.45
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