Korea Institute of Science and Technology Seung-Hyeob Lee, Churl-Seung Lee, Seung-Cheol Lee, Kyu-Hwan Lee, and Kwang-Ryeol Lee Future Technology Research

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


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


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


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


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


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


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


Deposition Behavior of a-C FilmDeposition Behavior of a-C Film

Incident atoms Substrate atoms

50 eV50 eV 150 eV150 eV1 eV1 eV


DensityDensity

0 50 100 150 200 250 300

0.65

0.70

0.75

0.80

Dens

ity [

]

Beam Energy [eV]


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]


Distribution of Coordination NumberDistribution of Coordination Number50 eV50 eV 150 eV150 eV1 eV1 eV 100 eV100 eV

4321 5Coordination

Number


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]


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]


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]


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.


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


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


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


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.


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

Documents

Korea Institute of Science and Technology Seung-Hyeob Lee, Churl-Seung Lee, Seung-Cheol Lee, Kyu-Hwan Lee, and Kwang-Ryeol Lee Future Technology Research