1. 금속이 혼입된 DLC 박막의 응력감소 거동 ; 제일원리계산
17, Feb., 2006
광운대학교
제 30회 학술발표회
반도체 및 박막 T-13
금속이 혼입된 DLC 박막의 응력감소 거동 ; 제일원리계산
한국과학기술연구원 미래기술연구본부
최정혜, 안효신, 이승철, 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. Disadvantages of DLC films
High residual compressive stress
(6~20 GPa)
poor adhesion
Hard disk
Before deposition
After deposition
Substrate bending
Delamination
M. W. Moon, Acta Mater., (2002).

4. Stress and sp3 bond fraction
Hardness

5. To reduce residual scomp in DLC films
Substrate biasing
Post-annealing ; T-11 이영광 발표
Metal atom incorporation
; Ti, W, Mo, Cr, Al….

6. W-incorporated DLC films
Ion beam deposition &
Magnetron sputtering
1.9 at % W
Mechanism ?
Not fully understood yet !!!
A.-Y. Wang APL (2005).

7. Purpose of this work ; First Principles Calculation DLC Diamond
; ideal sp3 bonding
109.5o
≠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
; First Principles Calculation

8. First principles calculation
Quantum modeling
“first principle” or “ab-initio” calculation
Without any empirical parameters
For a given atomic number, coordination  Schroedinger eq HY = EY
Theoretically accurate
Cohesive energy
Charge density
Electronic structure
(band, DOS)
Nature of bonding
STM image simulation…….
femtosec
picosec
nanosec
microsec
sec
1 nm
0.1 nm
1 mm
1 cm
1 m
Quantum
modeling
Atomistic
min
Continuum

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

10. Calculation condition
Code; DMOL3 ; Density Functional Calculation
Exchange-correlation potential; Generalized Gradient Approximation (GGA-PBE)
Atomic orbital; double-zeta polarization basis set
Cutoff radius of atomic orbitals; 9 Å
All electron calculation
Spin consideration

11. Total energy change by the bond angle distortion

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

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

14. Isosurface of electron density right before it is separatedV Ti Ni Si Mn W Cr Mo Co Fe C
109.5o

15. Isosurface of electron density right before it is separatedAg Ar Cd Au Al Zn Cu Pd C
109.5o

16. 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

17. W-incorporated DLC films

18. Conclusion C Mn Au Al