Growth and Characterization of Co nanoparticles and nanowires

劉全璞劉全璞

國立成功大學 國立成功大學 材料科學及工程學系材料科學及工程學系

半導體奈米材料實驗室半導體奈米材料實驗室

Outline

1. Introduction : Nanoparticle; nanowire; and PVD

2. Co nanoparticle by magnetron sputtering

3. Co nanoparticle and nanotube by ion-beam deposition

4. Conclusions

Traditional PVDs for nanopaticle fabrication

• Clusters by free jet expansion

• Nanoparticle by low temperature deposition

• Quantum dot by epitaxial growth

Clusters by free jet expansion

Nanoparticle by low temperature deposition

Quantum dot by epitaxial growth

Stranski-Krastanow growth mode

What happen when together?

Shape evolution

Traditional VLS for nanowire growth

Objectives

Si substrate

native SiO2

Co nanoparticles

These can be used for catalysts.

Various types of CNT can be grown.

(a) (b) (c)

(d) (e) (f)

Deposition distance vs surface morphologyAFM PW = 8 mtorr、 PDC = 50 W、 Vbias = -100 V、 tD = 10 sec

60mm 70mm 80mm

90mm 100mm 110mm

Size =60-120nm Size =120-150nm

Size = 130-170nm

-50V(b)

0V(c)

+250V(d)

+525V(e)

0 nm

17.5 nm

35 nm-100V

(a)

500 nm

Substrate bias vs surface morphologyAFM PW = 8 mtorr、 PDC = 50 W、 DT, Sub = 110 mm、 tD = 10 sec

(b)

Substrate bias vs size and height

Substrate bias vs island density

positive Vbias

obvious

particles

uniform

distribution

1μm 100 nm

100 nm

Substrate bias vs surface morphologySEM plan view

-100V -50V

+250V

20 nm 20 nm

fcc structure

BF DF

Substrate bias vs nanoparticle microstructureTEM plan view

1010 0111

1101

2020

200

020

220

220

20 nm

100 nm 40 nm

Substrate bias vs nanoparticle microstructureTEM cross section Vsub = +250 V

Substrate bias – nanoparticle growth mechanismCoulomb force self-limited growth

deposition

e- e-

crevice filling

SiO2

Si substrate

repulsion

deposition

e- e-

repulsion

SiO2

Si substrate

island growth

Si substrate

deposition

e- e-

SiO2

-100 V

-50 V

+525 V

+250 V

0 V

Substrate bias vs nanoparticle magnetic property

Growth time vs surface morphologyAFM PW = 8 mtorr、 PDC = 50 W、 DT, Sub = 110 mm、 tD = 10 sec、 Vsub = +525 V

(a)

20.1 ML

(b)

39.8 ML

(c)

59.6 ML

10 sec 20 sec 30 sec

(a)

20 nm

(b)

20 nm

(a)

100 nm

(c)

50 nm

(b)

100 nm

20 secfcc

30 secfcc

Growth time vs nanoparticle microstructureTEM cross section Vsub = +250 V

1： ANODE grid2： A/D grid3： Ground grid

solenoid coilPwaveguide

gas

ECR zone

1

2

3

E

θ

target

watercooling

Cu backing plate

resputtered atom

sputtered atom

fast Ar

substrate

sputter voltage (positive bias)

Mechanism of ion beam deposition

Co nanoparticle and wire by ion beam depositionSEM

2sec、 RT

2sec、 400℃

( c ) ( d )

2sec、 950℃

1012 cm-2 1011 cm-2 5*108 cm-2

Co nanoparticle with various density

Co nanowire growth by ion beam depositionAFM

0.5m

Nucleation of Cobalt silicide nanowireOn Si(001)

0.5m

Cobalt magnetic quantum dots on Si(001)

100nm100nm

402111

111

513

311622

222

531220

402

222131

440751

660351

042 333

-

-

-

-

-

351

000311

622

220531

751440

713

- - -

131 -

- -

- -

- -- -

- --

- -

-

-

-

-

- - -

- - -

- - -

042 -

Co nanowire growth by ion beam depositionTEM

Conclusions

Nanoparticle can be formed under negative bias at suitable conditions, however, damaged. Due to Coulomb force self-limited growth, Co nanoparticle is of very uniform distribution without obvious damage. Co nanoparticle as small as 10nm can be prepared by sputtering and exhibit superparamagnetic property

Conclusions

By IBS, the Co dot density can be varied by 1000 with very uniform size distribution EPitaxial Cobalt silicide nanowire can be fabricated by IBS

Acknowledgements

1. Students : 鍾秉憲 ; 王志欽

2. 國科會 NSC 91-2120-E006-003