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Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Seung-Hyeob LeeSeung-Hyeob Lee, Churl-Seung Lee, Seung-Cheol Lee, Kyu-Hwan Lee, and K, Churl-Seung Lee, Seung-Cheol Lee, Kyu-Hwan Lee, and K
wang-Ryeol Leewang-Ryeol Lee
Future Technology Research Division,Future Technology Research Division, Korea Institute of Science and Technology,Korea Institute of Science and Technology,P.O. Box, 131 Cheongryang, Seoul, KoreaP.O. Box, 131 Cheongryang, Seoul, Korea
Structural Evolutions of Amorphous Structural Evolutions of Amorphous Carbon Films by Molecular Dynamics Carbon Films by Molecular Dynamics
Simulation Simulation
The International Conference On Metallurgical Coatings And Thin The International Conference On Metallurgical Coatings And Thin FilmsFilms
ICMCTF 2003ICMCTF 2003
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
IntroductionIntroduction
Tetrahedral Amorphous Carbon (ta-C) FilmTetrahedral Amorphous Carbon (ta-C) Film
Non-hydrogenated amorphous carbon
High ratio of sp3 hybridized carbon bonds (60-80%)
High hardness, density, and wear resistance
Smooth surface, chemical inertness, optical transparency
RMS roughness = 0.95nm
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
MotivationMotivation
Problems of ta-C FilmProblems of ta-C Film High Residual Compressive Stress
6 – 20 GPa Deterioration of Adhesion
Self-delamination of a-C film Peeling off the a-C film
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
ApproachApproach
Atomic Scale Investigation using Computer SimulationAtomic Scale Investigation using Computer Simulation Investigation of structural evolutions and physical
properties Understanding of mechanical, chemical, thermal Understanding of mechanical, chemical, thermal
phenomenaphenomena Overcome the limitation of experiments Various conditions
Understanding the Relationship between Structure Evolution and Material Properties
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Structural Modeling for ta-C Film Structural Modeling for ta-C Film
Subplantation ModelSubplantation Model Generation rigid, dense phase by shallow subsurface implantation p
rocess by deposition of hyperthermal species Y. Lifshitz et al. Phys. Rev. Lett., 62 (1989) 1290
Thermal Spike ModelThermal Spike Model Generation stress state by localized melting due to adequate high in
cident beam energy and rapid chilling D. R. Mckenzie et al. Phys. Rev. Lett., 67 (1991) 773
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Purposes of This WorkPurposes of This Work
Growth of a-C Film by Molecular Dynamics Growth of a-C Film by Molecular Dynamics SimulationSimulation Deposition of carbon atom with high energy
Observation of Structural EvolutionObservation of Structural Evolution
Investigation of Material PropertiesInvestigation of Material Properties Pair correlation function, bonding structure, density
and stress
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
MethodologyMethodology
Empirical Potential Empirical Potential Tersoff Potential
J. Tersoff, Phys. Rev. Lett., 61 (1988) 2879.
DiamondDiamond SubstrateSubstrate Number of atoms : 608 Temperature : 300K Boundary condition : Y-Z axis
Carbon DepositionCarbon Deposition Number of deposited atoms : 500 atoms Incident kinetic energy : 1 ~ 300 eVIncident kinetic energy : 1 ~ 300 eV Time step : 0.155 ~ 0.5 fs Interval between carbon arrival : 1 ps Full dynamics except fixed layer In the case of 75 eV
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Deposition Behavior of a-C FilmDeposition Behavior of a-C Film
Incident atoms Substrate atoms
50 eV50 eV 150 eV150 eV1 eV1 eV
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
DensityDensity
0 50 100 150 200 250 300
0.65
0.70
0.75
0.80
Dens
ity [
]
Beam Energy [eV]
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
0 50 100 150 200 250 300
-6
-3
0
3
6
9
12
Stre
ss [G
Pa]
Beam Energy [eV]
Residual Stress and spResidual Stress and sp33 Bond Fraction Bond Fraction
0 50 100 150 200 250 300
0.1
0.2
0.3
0.4
0.5
sp3
Ratio
Beam Energy [eV]
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Distribution of Coordination NumberDistribution of Coordination Number50 eV50 eV 150 eV150 eV1 eV1 eV 100 eV100 eV
4321 5Coordination
Number
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Experimental Residual StressExperimental Residual Stress
J.-K. Shin et al, Appl. Phys. Lett., 27 (2001) 631-633.
Growth by Filtered Vacuum Arc Growth by Filtered Vacuum Arc MethodMethod
0 50 100 150 200 250 300
-6
-3
0
3
6
9
12
15
Stre
ss [G
Pa]
Beam Energy [eV]
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
1 2 3 4 50
5
10
15
300 eV
150 eV
100 eV
50 eV
10 eV
1 eV
Pair
Corr
elat
ion
Func
tion (
r)
r [A]
Pair Correlation FunctionPair Correlation Function
Satellite Site
0 50 100 150 200 250 3000.0
0.2
0.4
0.6
0.8
Peak
Inte
nsity
Beam Energy [eV]
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Comparison of Pair Correlation FunctionComparison of Pair Correlation Function
1 2 3 4 5
0
3
6
9
12
15
18
1.25 K/fs
2.5 K/fs6.25 K/fs
12.5 K/fs
Infinite Cooling
Pair
Corr
elat
ion
Func
tion (
r)
r [A]1 2 3 4 5
0
5
10
15
300 eV
150 eV
100 eV
50 eV
10 eV
1 eV
Pair
Corr
elat
ion
Func
tion (
r)
r [A]
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Conclusions Conclusions
The optimum incident energy for the highest residual stress, spThe optimum incident energy for the highest residual stress, sp33 bond ratio an bond ratio an
d density was in the rage from 50 to 75 eV, which is in good agreement with ed density was in the rage from 50 to 75 eV, which is in good agreement with e
xperimental observations.xperimental observations.
At the optimum incident energy, significant amount of carbon atom was placed At the optimum incident energy, significant amount of carbon atom was placed
at a meta-stable site of distance 0.21 nm. at a meta-stable site of distance 0.21 nm.
From the meta-stable site intensity, the atomic structure of the amorphous carFrom the meta-stable site intensity, the atomic structure of the amorphous car
bon film depended on the quenching rate of thermal spike due to the collision bon film depended on the quenching rate of thermal spike due to the collision
of energetic carbon atom.of energetic carbon atom.
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Potential Energy (Incident Energy Dependence)Potential Energy (Incident Energy Dependence)
0 1000 2000 3000 4000 5000-1.14E-011
-1.12E-011
-1.10E-011
-1.08E-011
300eV150eV100eV
50eV10eV
1eV
Ene
rgy
[erg
]
Time [fs]
Potential Energy
1 eV 50 eV 300 eV
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
0 1 2 3 4 5 6-7.2
-7.1
-7.0
-6.9
-0.1
0.0
0.1
0.2
0.3
Potential Energy
Total Energy
Kinetic Energy
Ener
gy [e
V]
Time Step [ps]
Behavior of System Energy during DepositionBehavior of System Energy during Deposition
1st Atom 2nd Atom
5th Atom3rd AtomBombardmentoccurs here!
In the case of 50 eV
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Snapshot of Coordination and Residual Snapshot of Coordination and Residual StressStress
Min
Max
43210
5
In the case of 75 eVIn the case of 75 eV
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Applications Applications
Industrial ApplicationsIndustrial Applications Head drum of VCR, CD-R pressing die, chip carrying tools, forming dies, EMC m
olding cavity and so on.
Biological and Medical ApplicationsBiological and Medical Applications Artificial valve of the heart, hip joint, stent and so on.
Korea Institute of Science and TechnologyKorea Institute of Science and Technology
Behavior of System Energy during DepositionBehavior of System Energy during Deposition
0 1 2 3 4 5 6-7.2
-7.1
-7.0
-6.9
-0.1
0.0
0.1
0.2
0.3
Potential Energy
Total Energy
Kinetic Energy
Ener
gy [e
V]
Time Step [ps]
Bombardmentoccurs here!
In the case of 75 eVIn the case of 75 eVDeposition atom added here