vii
TABLE OF CONTENTS
CHAPTER
1
2
TITLE
PAGE
DECLARATION
DEDICATION
ACKNOWLEDGEMENTS
ABSTRACT
ABSTRAK
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF ABBREVIATIONS / SYMBOLS
LIST OF APPENDICES
ii
iii
iv
v
vi
vii
x
xi
xiv
xviii
INTRODUCTION
1
1.1
Background of Research
1
1.2
Research Objectives
4
1.3
Research Scopes
4
1.4
Research Problems
5
1.5
Layout of Thesis
6
THEORETICAL CONSIDERATION
7
2.1
Introduction
7
2.2
Self-assembly (Bottom-up Nanotechnology)
8
2.3
Silicon Nanodots
9
2.4
Theory of Nucleation and Growth
15
2.4.1
Quantitative Description of Nucleation
17
2.4.2
Growth Modes
22
viii
2.5
2.6
3
Physical Vapor Deposition (PVD)
25
2.5.1 Evaporation
26
2.5.2 Sputtering
27
2.5.3 Ion Plating
27
Radio Frequency (RF) Magnetron Sputtering
28
METHODOLOGY
33
3.1
Introduction
33
3.2
Theoretical Computing Program
33
3.3
High Vacuum Coater (HVC)
36
3.4
Setting up of High Vacuum Coater System
39
3.4.1
Substrate Holder
39
3.4.2
Film Thickness Monitor (FTM7)
40
3.4.3
Substrate Temperature Thermocouple
41
and Monitor
3.5
4
Substrate Preparation
42
3.5.1
Substrate Pre-clean
43
3.5.2
Ionic Cleaning
44
3.5.3 Pre-sputtering Process
44
3.6
Radio Frequency (RF) Sputtering Deposition Process
44
3.7
Deposition Parameters
46
3.8
Analytical Tools
47
3.8.1
48
Atomic Force Microscope (AFM)
3.8.2 Photoluminescence Spectroscopy (PL)
49
3.8.3 Energy Dispersive X-ray Spectroscopy (EDX)
50
3.8.4 X-ray Diffraction (XRD)
51
RESULTS AND DISCUSSIONS
53
4.1
Introduction
53
4.2
Nucleation and Growth
54
ix
4.3
Surface Morphology using Atomic Force
61
Microscopy (AFM)
4.4
4.5
4.6
5
4.3.1 Sapphire Substrate
61
4.3.2 Effect of Deposition Time
62
4.3.3
Effect of RF power
67
4.3.4
Effect of Substrate Temperature
69
Energy Dispersive X-ray Spectrometry (EDX)
71
4.4.1 Effect of Deposition Time
71
4.4.2
Effect of RF power
74
4.4.3
Effect of Substrate Temperature
75
Photoluminescence (PL)
76
4.5.1 Effect of Deposition Time
76
4.5.2
Effect of RF power
80
4.5.3
Effect of Substrate Temperature
81
X-ray diffraction (XRD)
84
SUMMARY AND CONCLUSION
88
5.1
Summary and Conclusion
88
5.2
Recommendation
93
REFERENCES
95
APPENDICES
107
x
LIST OF TABLES
TABLE NO.
TITLE
PAGE
3.1
Typical physical properties for 304 stainless steel
39
3.2
The samples preparation condition with argon flow
47
rate 5 sccm
4.1
Data obtained from the simulation and experimental
57
4.2
Atomic and weight compositions of silicon grown on
73
sapphire prepared under different deposition times
xi
LIST OF FIGURES
FIGURE NO.
2.1
TITLE
Difference energy bandgap between bulk material and
PAGE
11
quantum dots refer to the size of Exciton Bohr Radius
2.2
Basic SET structure and the equivalent circuit
12
2.3
Dome-like shape of a nucleus, showing the related
20
parameters
2.4
Equlibrium phase diagram for self-assembled nanodot
23
formation
2.5
Three types of growth mode
24
2.6
The process of Volmer-Weber Growth
25
2.7
Basic variant of Physical Vapour Deposition Techniques
28
2.8
Principle of sputtering process
30
3.1
Flow chart showing the simulation process
34
3.2
Basic Diagram of the computing program
35
3.3
Example of output graph
36
3.4
High Vacuum Coater
38
3.5
The customized stainless steel substrate holder with screws
40
3.6
The location of Film Thickness Monitor added
41
3.7
Configuration of thermocouple to substrate holder
42
3.8
Delta Ultrasonic Cleaner
43
3.9
The principle of AFM
48
3.10
SPI3800N Scanning Probe Microscope System
49
3.11
PLM 100 Accent System
50
3.12
The Philips XL-40 SEM
51
3.13
Principle of GIXRD
52
xii
4.1
AFM image of silicon nanodots deposited on sapphire
55
substrate at 3 mins depsosition time
4.2
The cross sectional area of a dome shape silicon nanodot
55
(marked ‘X’ in Figure 4.1 of diameter 39.42 nm, with
a possible non-wetting oval shape (dotted) shown for
comparison
4.3
Graph of r* and ΔG* as function of temperature (T)
59
4.4
Graph r* and ΔG* as function of γNS
59
4.5
Graph of r* and ΔG* as function of contact angle (θ)
60
4.6
AFM images of blank sapphire substrate with RMS
62
of 0.228 nm
4.7
The 1μm x 1μm AFM images for samples deposited at
63
a fixed substrate temperature of 400 oC and RF power of
100 W with different deposition times: (a) 3 minutes,
(b) 5 minutes, (c) 7 minutes and (d) 10 minutes
4.8
Graph of average dot size (nm) and RMS (nm) as a function
65
o
of deposition time at a fixed 400 C substrate temperature
and 100 W RF power
4.9
The 5μm x 5μm AFM images for the sample grown using
66
400 oC substrate temperature, 100 W RF power and 15
minutes deposition time
4.10
The 5μm x 5μm AFM images for samples deposited at a
68
o
fixed substrate temperature of 400 C and deposition time
of 5 min with different RF powers: (a) 50 W, (b) 100 W,
(c) 150 W and (d) 200 W
4.11
The 5μm X 5μm AFM images for samples deposited at a
70
fixed RF power of 100 W and deposition time of 5 minutes
with different substrate temperatures: (a) 100oC, (b) 200oC,
(c) 300oC and (d) 400oC
4.12
EDX spectrum of silicon nanodots grown on sapphire with
400 oC substrate temperature and 100 Watt RF power at:
(a) 3 minutes, (b) 5 minutes, (c) 7 minutes and
(d) 10 minutes
72
xiii
4.13
Graph of silicon at.% as function of RF power at 5 minutes
74
deposition time and 400 oC substrate temperature
4.14
Graph of silicon at.% as function of substrate temperature
75
at 5 minutes deposition time and 100 Watt RF power
4.15
Photoluminescence spectra for samples deposited at a
77
o
fixed substrate temperature of 400 C and RF power of
100 Watt with different deposition times
4.16
Photoluminescence spectra for samples deposited at a
78
fixed substrate temperature of 200oC and RF power of
100 Watt with different deposition times
4.17
Photoluminescence spectra for samples deposited at a
81
fixed substrate temperature of 400 oC and deposition
time of 5 minutes with different RF powers
4.18
Photoluminescence spectra for samples deposited at a
83
fixed deposition time of 5 minutes and RF power of
100 Watt with different substrate temperatures
4.19
Photoluminescence spectra for samples deposited at a
84
fixed deposition time of 15 minutes and RF power of
100 Watt with different substrate temperatures
4.20
Grazing incidence X-ray diffraction pattern of the sample
85
deposited at 5 minutes deposition time, 400 oC substrate
temperature and RF power of 100 W using 0.1o grazing
angle
4.21
Grazing incidence X-ray diffraction pattern of the sample
86
deposited at 10 minutes deposition time, 400 oC substrate
temperature and RF power of 100 W using 0.1o grazing
angle
4.22
Grazing incidence X-ray diffraction pattern of the sample
o
deposited at 5 minutes deposition time, 400 C substrate
temperature and RF power of 200 W using 0.5o grazing
angle
86
xiv
LIST OF ABBREVIATIONS / SYMBOLS
ax
-
The lateral size of the nanodots
at.%
-
Atomic percentage
a-Si
-
Amorphous Silicon
AFM
-
Atomic Force Microscope
Al2O3
-
Aluminium Oxide or Sapphire
Ar
-
Argon
B
-
Magnetic field
c
-
Velocity
ΔCp
-
Difference in specific heat
CVD
-
Chemical vapour deposition
DC
-
Direct Current
eV
-
Electron volt
Ee
-
Energy of the electron
E
-
Electric Field
EDX
-
Energy Dispersive X-Ray Spectroscopy
F-M
-
Frank-van der Merwe
FESEM
-
Field Emission Scanning Electron Microscope
FTM7
-
Film Thickness Monitor
FWHM
-
Full Wave Half Maximum
ΔG
-
Net change of energy (Gibbs Work)
ΔG*
-
Critical energy
ΔGhom
-
Net change of energy for homogeneous nucleation
xv
*
ΔGhom
-
Critical energy for homogeneous nucleation
ΔGhet
-
Net change of energy for heterogeneous nucleation
*
ΔG het
-
Critical energy for heterogeneous nucleation
ΔGv
-
Free energy change per unit volume
GIXRD
-
Grazing Incidence X-ray Diffraction
GaN
-
Gallium Nitride
Δhv
-
The changes in enthalpy
ΔHf
-
Enthalpy of fusion
h
-
Planck constant = 6.6260755 × 10-34 Js
H2
-
Hydrogen
HRTEM
-
High Resolution Transmission Electron Microscopy
Hz
-
Hertz
k
-
Boltzmann constant
La
-
Lattice constants for Silicon
Lb
-
Lattice constants for Sapphire
Lf
-
Latent heat of fusion of the material per unit volume
LPCVD
-
Low-Pressure Chemical Vapour Deposition
LSI
-
Large-Scale Integration
m
-
Mass of electron
n
-
Principal Quantum Number
N2
-
Nitrogen
p
-
Vapour pressure
pe
-
Saturation vapor pressure
PECVD
-
Plasma-Enhanced Chemical Vapour Deposition
PL
-
Photoluminescence
PVD
-
Physical Vapour Deposition
Q
-
The scattering vector
r
-
The radius of the nucleus
r*
-
Critical radius
xvi
*
rhom
-
Critical radius for homogeneous nucleation
*
rhet
-
Critical radius for heterogeneous nucleation
R
-
Gas constant
RF
-
Radio Frequency
RMS
-
Root mean square
S
-
Supersaturation ratio
Δsv
-
The changes in entropy
SET
-
Single Electron Transistor
SEM
-
Scanning Electron Microscope
Si
-
Silicon
SiH4
-
Silane
SiO2
-
Silicon dioxide
S-K
-
Stranski-Krastanov
T
-
Temperature
Tm
-
Solidification temperature
ΔT
-
Undercooling temperature
vo
-
Atomic volume
V-W
-
Volmer-Weber
wt.%
-
Weight percentage
XPS
-
X-Ray Photoelectron Spectroscopy
XRD
-
X-ray Diffraction
λ
-
The Peak Wavelength Emission
π
-
Pi = 3.1415926
α
-
Incidence angle
β
-
Exit angle
γ
-
Surface energy per unit area
γ LN
-
Surface energy per unit area at liquid-nucleus interface
γ NS
-
Surface energy per unit area at nucleus-solid interface
xvii
γ LS
-
Surface energy per unit area at liquid-solid interface
θ
-
Contact angle
ε
-
Lattice mismatch
ϑ
-
Number of monolayers deposited
xviii
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
Quantitative Description of Nucleation Theory
107
B
Unit Convertion (Liquid-solid transition)
112
C
Publications
113