molecular dynamics investigation to identify al atomic behavior on various cu surfaces

Molecular dynamics investigation Molecular dynamics investigation to identify Al atomic behavior on to identify Al atomic behavior on

various Cu surfacesvarious Cu surfaces

2007. 2. 6

김상필 1,2, 김영근 3, M. Sahashi4, 이광렬 1, 정용재 2

1 한국과학기술연구원 계산과학센터 , 2 한양대학교 신소재공학부3 고려대학교 신소재공학부 , 4Dept. of Electronic Eng., Tohoku University

Atomic-scale Thin Film GrowthAtomic-scale Thin Film Growth

As the scale of device goes down to an atomic level…

a

b

ES* barrier

Various & complex diffusion behaviors

Conventional concepts

- Downward funneling model PRL 62, 921 (1989).

- Transient mobility model PRB 41, 5410 (1990).

- Impact cascade diffusion model PRB 57, 6685 (1998).

- Anomalously intermixing PRB 66, 104427 (2002).

:

Research Strategy Research Strategy

Atomic scale deposition behavior

Morphology&

Diffusion path

Fundamentalunderstanding

Surface diffusion barrier calculation

Using Molecular Dynamics & Statics methodUsing Molecular Dynamics & Statics method

EAM Potentials for Al-Cu System*EAM Potentials for Al-Cu System*

ao (Å) Ecoh (eV) Bulk M. (GPa)

Al (FCC)

4.05035 (~0.01%)

3.31876(-1.23%)

75.565(-0.57%)

Al3Cu(L12)

3.9025(-0.97%)

3.47614 84.542

AlCu(L10)

3.75912(-1.93%)

3.59907 98.7448

AlCu3

(L12)

3.65454(-1.87%)

3.64548 117.274

Cu(FCC)

3.61503(~0.001%)

3.5241(-0.45%)

139.8872(-0.08%)

L12

L10

FCC

“Simple analytic embedded-atom-potential model including a long-range force for fcc metals and their alloys”, J.Cai and Y.Y. Ye, Phys. Rev. B 54 8398 (1996).

*Al, Cu is the source material of GMR device

Simulation ProcedureSimulation Procedure

Deposition Behavior CalculationDeposition Behavior Calculation

• Cu surface (100), (110), (111) (clean & with plateau surface)

• Substrate Temp. : 300K

• Incident Energy with normal incidence 0.1 eV

Normal incidence

Diffusion Energy Barrier CalculationsDiffusion Energy Barrier Calculations

Molecular Statics

Molecular Dynamics (MD)

MD results(position, path) Following the diffusion path

0 5 10 15 20-2,402.95

-2,402.94

-2,402.93

-2,402.92

-2,402.91

-2,402.90

-2,402.89

-2,402.88

-2,402.87

-2,402.86

To

tal

En

erg

y [e

V]

Reaction Path

0.5ML Al on Cu(100)0.5ML Al on Cu(100)

With plateauClean surface

Cu surface atoms Cu plateau atoms Al deposit atoms

Energy Barriers for Surface Diffusion* – (100)Energy Barriers for Surface Diffusion* – (100)

B1: Surface diffusionB2: Away from the stepB3: Toward the stepB4: Along the stepB5: Upward diffusionB6: Away from the step on plateauB7: Along the step on plateauB8: Downward diffusionB9: Ehrlich-Schwoebel (ES)

B1 B2 B3 B4 B5 B6 B7 B8 B9

0.33 0.611 0.269 0.262 0.647 0.316 0.33 0.424 0.571

Energy Barrier [eV]

B1

B2

B4

B6

B7B8

B9

B5

B3

W. Zhu et al., PRL 92, 106102 (2004), S. Durunkanoglu et al., PRB 73, 125426 (2006),X.F. Gong et al., TSF 493. 146 (2005), H. Yildirim et al., Surf. Sci. 600, 484 (2006).*Various Surface Barriers

B1 B2 B3 B4 B5 B6 B7 B8 B9

0.33 0.611 0.269 0.262 0.647 0.316 0.33 0.424 0.571

B1

B2

B4

B3

Energy Barriers for Surface DiffusionEnergy Barriers for Surface Diffusion

Surface & Step

B1 B2 B3 B4 B5 B6 B7 B8 B9

0.33 0.611 0.269 0.262 0.647 0.316 0.33 0.424 0.571

B6

B7B8

B9

B5


Step & Plateau

0.5ML Al on Cu(111)0.5ML Al on Cu(111)

With plateauClean surface

Cu surface atoms Cu plateau atoms Al deposit atoms

B1: Surface diffusion for fcc hcp siteB2: Surface diffusion for hcp fcc siteB3: Along the stepB4: Away from the step (two steps)B5: Toward the stepB6: Away from the step on plateauB7: Ehrlich-Schwoebel (ES) barrierB8: Downward diffusionB9: Upward diffusion

B1 B2 B3 B4 B5* B6 B7 B8 B9

0.055 0.055 0.308 0.638 - 0.018 0.331 0.106 0.317

B1

B3 B4

B6

B7

B8

B9

Energy Barrier [eV]

* Spontaneous reaction

B5

Energy Barriers for Surface Diffusion – (111)Energy Barriers for Surface Diffusion – (111)

B1 B2 B3 B4 B5* B6 B7 B8 B9

0.055 0.055 0.308 0.638 - 0.018 0.331 0.106 0.317

B1

B3 B4


B5


Surface & Step

B1 B2 B3 B4 B5* B6 B7 B8 B9

0.055 0.055 0.308 0.638 - 0.018 0.331 0.106 0.317

B6

B7

B8

B9



Step & Plateau

Clean surface With plateau

0.5ML Al on Cu (110)0.5ML Al on Cu (110)

Cu surface atoms Cu plateau atoms & same height with plateau atoms

Al deposit atoms

B1: Perpendicular to the open channelB2: Along the open channelB3: Along the step (perpendicular to the open channel)B4: Away from the stepB5: Toward the stepB6: Upward diffusionB7: Along the step (along the open channel)B8: Along the open channel on the plateauB9: Perpendicular to the open channel on the plateauB10: Downward diffusionB11: Ehrlich-Schwoebel (ES) B12: Exchange

B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12

0.816 0.303 0.797 0.493 0.256 0.535 0.306 0.302 0.814 0.434 0.495 0.419

Energy Barrier [eV]

B10

B1

B2

B3

B4

B6

B8

B9

B11

B12

B5

B7

Energy Barriers for Surface Diffusion – (110)Energy Barriers for Surface Diffusion – (110)

B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12

0.816 0.303 0.797 0.493 0.256 0.535 0.306 0.302 0.814 0.434 0.495 0.419

B10

B1

B2

B3

B4

B6

B8

B9

B11

B12

B5

B7

Diffuse along the open channel(B2, B7, B8) or exchange mixing behavior (B12)


SummarySummary

Deposition behavior and surface diffusion barrier calculation were investigated using by Molecular Dynamics, Statics.

This set of results can be used as input in KMC simulations.This set of results can be used as input in KMC simulations.

(100) (111) (110)

• Along the step• Downward diffusion

• Toward the step• Downward diffusion• Away from the step on plateau

• Along the open channel• Exchange mixing

molecular dynamics investigation to identify al atomic behavior on various cu surfaces

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