growth and characterization of co nanoparticles and nanowires...
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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
Quantum dot by epitaxial growth
Stranski-Krastanow growth mode
What happen when together?
Shape evolution
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
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
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 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
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