Thermodynamics and Kinetics study of growth behavior of sono-electrodeposited Cu thin films

Sabita Rout, A. Mallik, B. C. RaySabita.swain1@gmail.com archananitrkl@gmail.com

drbcray@gmail.com ,

Department of Metallurgical and Materials EngineeringNational Institute of Technology, Rourkela

SEQUENCE OF PRESENTATION

Growth of thin films – an insight

The growth parable

Sono-electrodeposition technique

Experimental /Results and discussion

Conclusions

References

Harper et.al, Journal of applied Physics, 86 (1999) 2516-2524

(Property change with variation of grain size)

(Time bound Grain growth)

Growth of thin films

The growth Parable

Model 1Different sizes

Model 2Sequence of different sizes

Model 3Same sizes

Model 4Sequence of same sizes

Sources Grain boundaries Stacking faults Dislocations Surface energy Elastic strain Pinning particles

Grain growth mechanism Ostwald ripening Triple junctions Zener pinning

Two modes of grain growth Normal grain growth Abnormal grain growth

(Growth models)

Normal grain growth Abnormal grain growth

Follows a parabolic law

Diameter of grains comparable to the film thickness

Growth is slow and steady

A monomodal distribution of grain sizes after growth

Grain boundary velocity is given by

Diameter of grains exceeds ten times the film thickness

Growth is rapid and abrupt

A bimodal distribution of grain sizes after growth

)/exp()/( RTa

GmTVGCv KtDD 20

Normal vs. abnormal grain growth

• Extreme fast mass transport

• Affects the crystallization process

• Degassing at the electrode surface

Sono-electrodepositionThe coupled effect of electrochemistry and ultrasound

(A cavitation bubble)

(The equipment)

(The effects)

cavitation

Reaction kinetics - > cyclic voltammetry

Cyclic Voltammetry of copper deposits at (a)Sonicntion (b) Silent

Bath temp (°C) Oxidation potential (V)

Cathodic efficiency

5 +0.567 1.6

10 +0.626 0.79

15 +0.626 0.92

20 +0.626 0.72

25 +0.626 0.84

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2-0.12

-0.10

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

Cu

rren

t (A

)

Potential (V)

5C 10C 15C 20C 25C

ab

Portela et.al , Electrochimica Acta, 51 (2006) 3261-3268

(Deposition at -0.3V)

0 5 10 15 20

-0.035

-0.030

-0.025

-0.020

-0.015

Cur

rent

/A

Time/sec

5C 10C 15C 20C 25C

Nucleation mechanism - > Chrono amperometry analysis:

Mallik et.al , Electrochemical and Solid State Letters, 12 (2009) F46-F49 Han et.al, Electrochimica Acta, 54 (2009) 3419-3427

20 °CBath temp (°C)

Imax (A/cm2)

tmax(s) D x 10-9 (cm2 s-1 )

N x 1010 (cm-2 )

5 0.0228 1.726 1.1673 4.5604

10 0.0184 0.885 1.2246 3.273

15 0.0175 1.139 1.4257 2.1844

20 0.0162 1.349 1.447 1.8171

25 0.0238 1.685 3.9011 0.5396

Table: Characteristic kinetic parameters of current transients obtained for sonicated copper deposits

(Deposition at silent condition)

(DSC thermograms at scan rate of 5°/min )

Thermodynamics and Kinetics - > DSC analysis:

Copper deposition at (°C) Activation energy (eV/atom)

5 0.85

10 2.90

15 1.51

20 1.50

25 1.35

Kissinger equation

Heat release increases with decrease in temperature The exothermic peak observed around 320°C Activation energy is in the range, 0.85-2.9 eV

0.001500.001510.001520.001530.001540.001550.001560.001570.001580.001590.001600.001610.001620.00163

-11.4

-11.2

-11.0

-10.8

-10.6

-10.4

-10.2

-10.0

-9.8

5C 10C 15C 20C 25C

Ln

(/T

m2

)

1/Tm(1/K)

Table: Activation energies

Temperature (°C)

S. E (mN/m) Before DSC

S.E (mN/m)After DSC

5 59.92 55.62

10 51.58 34.24

15 45.84 67.86

20 41.77 43.21

25 30.48 32.30

Growth mode - >surface energy

Table: Surface energy values

Decrease in temperature – increase in SE Fluctuations in SE after thermal treatment – abnormal to normal growth behavior

(Water on deposit )

(SE determination by Owens-Wendt &

Kaelble (OW) method)

40 50 60 70 80 90 100

0100200300400500600700800900

1000110012001300140015001600

Inte

ns

ity

(arb

.un

its

)

2(degree)

Cu(111)

Cu(200)Cu(022) Cu(113)

5C

10C

15C

20C

25C

C(1011)S(0214)

Cl(721)S(062)

XRD plots of copper deposits (a) before DSC (b) after DSC

XRD analysis

Size and strain calculated from XRD plots for copper thin film (A) before DSC (B) after DSC

Bath temperatur

e (°C)

Size (nm) Strain x 10-3

5 12.4416 5.5025

10 22.3809 4.0702

15 53.159 2.1285

20 65.5048 1.815

25 182.5815 0.2787

40 50 60 70 80 90 100

0

50

100

150

200

250

300

350

400

450

500

Inte

ns

ity

(arb

.un

its

)

2(degree)

15C 20C 25C

Cu(111)

Cu(200)

Cu(022) Cu(113)S(062) S(0214)

Cl(721)

C(1011)

Bath temperature

(°C)

Size (nm) Strain x 10-3

15 102.119 1.81075

20 116.4013 1.0675

25 230.5810 0.0475

a b

A B

SEM analysis both before and after DSC:

a

c d

(SEM images of copper deposited at 5°C, 10°C, 15°C, 20°C, 25°C under sonication condition (a-e) as

deposited (f-j) after DSC)

a b c d e

f g h i j

Model-4Model-1

Model-1

i j

Conclusions

Better adherence of deposit by sono-electrodeposition.

The appearance of exothermic peak signifies occurrence of grain growth.

Determination of activation energy provides information about the kinetics of grain growth.

Whether proposed growth mechanism are the correct way to explore grain growth, will remain unclear until further investigations down to single grain or monolayer films

References

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