vii
TABLE OF CONTENTS
CHAPTER
TITLE
PAGE
DECLARATION
DEDICATION
iii
ACKNOWLEDGEMENTS
iv
ABSTRACT
v
ABSTRAK
TABLE OF CONTENTS
1
2
ii
vi
vii
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF ABBREVIATIONS
xiv
LIST OF SYMBOLS
xvi
INTRODUCTION
1.1 Background o f Research
1
1.2 Statement o f Problems
7
1.3 Objectives o f Research
8
1.4 Significant o f Research
8
1.5 Scope of Research
9
1.6 Thesis Outline
10
LITERATURE REVIEW
2.1 Introduction
11
2.2 Quantum Structure
2.2.1
Surface Effect
12
2.2.1. 1 Dispersion o f atoms on structure
14
2.2.1.2 Surface energy
16
2.2.2 Quantization Effect
2.3 Nucleation
19
22
2.3.1 Homogeneous nucleation
23
2.3.2 Heterogeneous nucleation
26
2.4 Lattice Constant in III-V Material System
28
2.5 Quantum Wire
31
2.6 Fabrication o f Quantum Structure
32
2.7 Vapour-liquid-solid (VLS) Growth Method
35
2.6.1
3
12
Gold (Au) for metal catalyst
37
RESEARCH METHODOLOGY
3.1 Introduction
39
3.2 Metal-Organic Chemical Vapour Deposition
40
(MOCVD)
3.3 Experimental Procedure
41
3.3.1 Growth Procedure
42
3.3.2 Growth Parameters
43
3.4 Analysis and Characterization Techniques
45
3.4.1 Scanning Electron Microscopy
45
(SEM) and Field Emission
Scanning Electron Microscopy (FE-SEM)
3.4.2 Transmission Electron Microscopy (TEM)
46
3.4.3 Energy Dispersive X-ray Spectroscopy
47
(EDX)
ix
4
RESULTS AND DISCUSSION
4.1 Introduction
49
4.2 Effect o f Growth Temperature on the InGaP
50
Quantum Wires
4.3 Effect o f Substrate Orientation on the InGaP
62
Quantum Wires
CONCLUSIONS AND SUGGESTION
REFERENCES
5.1 Conclusions
68
5.2 Suggestion
70
71
x
LIST OF TABLES
TABLE NO.
2.1
TITLE
Lattice
constant, bandgap
and
PAGE
absorption
edge
of
30
The diameter o f InGaP quantum wire for its body and
53
different semiconductors and alloys
4.1
head (Au) for growth temperature 380°C, 410°C, 440°C,
470°C and 500°C
xi
LIST OF FIGURES
FIGURE NO.
Figure 2.1
TITLE
PAGE
Dispersion, F, as a function o f n for cubic clusters up to
16
n = 100 (N = 106). On top is the structure o f the first
four clusters displayed with the corner atom being the
least saturated atoms on the right, followed by atoms on
the cubic edge, the in-plane surface and on the left is the
atoms in the interior (Roduner, 2006)
Figure 2.2
(From left to right) Schematic show evolution o f the
21
band gap and the density o f states (DOS) as the numbers
of atoms in a system decrease. kT is the thermal energy
and S is the Kubo gap, gap between the highest
occupied and the lowest unoccupied state (Roduner,
2006)
Figure 2.3
Graph o f the change o f volume free energy (A^v),
25
interfacial or surface energy (A^s) and the total free
energy (AG) as a function o f nucleus radius (Cao, 2003)
Figure 2.4
Schematic o f heterogeneous nucleation on a substrate
26
showing related parameters (Cantor, 2003)
Figure 2.5
Illustration
of
overall
excess
free
energy
for
28
homogeneous and heterogeneous nucleation as function
of nucleus size (Zeng et. al., 2011)
Figure 2.6
Energy bandgap versus lattice constant for material
alloys from group III-V, II-VI and IV elements
(Zeghbroeck, 1996)
29
xii
Figure 2.7
Lattice constant versus composition, x for some III-V
29
elements (Zeghbroeck, 1996)
Figure 2.8
Schematic
o f top-down
approach
and
bottom-up
33
approach in producing quantum structures (Cavallini et.
a l, 2004)
Figure 2.9
Schematic o f catalyst-assisted quantum wire growth
36
process in vapour-liquid-solid (VLS) method. (a) Au
nanoparticle deposited onto a substrate. (b) The sample
is heated above eutectic temperature and growth
materials introduced and alloy with the particle-crystal
interface.
(c) When appropriate
supersaturation is
achieved, nucleation occurs at the Au seed. (d) Quantum
wire growth occurs at particle-wire interface (Dick,
2008)
Figure 3.1
Figure 4.1
Graph o f temperature, T agains time, t for InGaP
quantum wires growth
43
FE-SEM images o f InGaP quantum wires seeded by Au
51
colloids on GaAs (100) substrate and grown for 30
minutes at (a) 380°C, (b) 410°C, (c) 440°C, (d) 470°C
and (e) 500°C
Figure 4.2
The points where the body and the head o f InGaP
52
quantum wire were measured
Figure 4.3
Graph o f growth temperature (°C) versus InGaP
54
quantum wire diameter (nm)
Figure 4.4
FE-SEM images o f InGaP quantum wire diameter at (a)
380°C, (b) 410°C, (c) 440°C, (d) 470°C and (e) 500°C
respectively
57
Figure 4.5
Diagram o f growth mechanisms for InGaP quantum
wires.
(a)
Direct
impinging
mechanism.
58
(b)
Combination o f direct impinging and reactant species
atoms diffusion mechanism
Figure 4.6
TEM image o f InGaP quantum wire grown at 410°C; to
60
show point (a) bottom part o f the wire, point (b) middle
of the wire and point (c) top o f the wire
Figure 4.7
EDX results o f the elements percentage in InGaP
61
quantum wire grown at 410°C taken from point: (a)
bottom, (b) middle and (c) top o f the wire
Figure 4.8
FE-SEM images o f InGaP quantum wires grown on
62
substrate GaAs (100) at growth temperature (a) 380°C
and (b) 470°C
Figure 4.9
FE-SEM images o f InGaP quantum wires grown on
63
subtrate GaAs (111) at growth temperature (a) 380°C
and (b) 470°C
Figure 4.10
Structure o f epilayer under biaxial compression: (a)
64
pseudomorphic and (b) relaxed with misfit dislocations
(Jain et. al., 1996)
Figure 4.11
(a) TEM images o f a single InGaP quantum wire. (b)
Close-up image o f InGaP quantum wire with growth
direction (-1,-1,-1). Twin boundary can be observed. (c)
Crystal structure for InGaP quantum wire is ZincBlende (ZB). (d) Lattice spacing d o f InGaP quantum
wire is 0.3342 nm or 3.342A
65
xiv
LIST OF ABBREVIATIONS
InGaP
-
Indium Gallium Phosphide
QWR
-
Quantum wire
QWRs
-
Quantum wires
0D
-
Zero-Dimensional
1D
-
One-Dimensional
2D
-
Two-Dimensional
3D
-
Three-Dimensional
Si
-
Silicon
Ge
-
Germanium
ZnO
-
Zinc Oxide
GaAs
-
Gallium Arsenide
InP
-
Indium Phosphide
ZB
-
Zinc Blende
GaAsP
-
Gallium Arsenide Phosphide
SETs
-
Single-Electron Transistors
SHTs
-
Single-Hole Transistors
LEDs
-
Light Emitting Diodes
VLS
-
Vapour-Liquid-Solid
VSS
-
Vapour-Solid-Solid
Au
-
Aurum (Gold)
AlGaAs
-
Aluminium Gallium Arsenide
MOCVD
-
Metal-Organic Chemical Vapour Deposition
SEM
-
Scanning Electron Microscopy
FE-SEM
-
Field Emission Scanning Electron Microscopy
TEM
-
Transmission Electron Microscopy
xv
EDX
-
Energy Dispersive X-spectroscopy
FCC
-
Face-Centred Cubic
DOS
-
Density o f States
CNT
-
Classical Nucleation Theory
CVD
-
Chemical Vapour Deposition
MBE
-
Molecular Beam Epitaxy
PLD
-
Pulsed Laser Deposition
SiI2
-
Silicon DiIodide
SiCl4
-
Silicon Tetrachloride
Be
-
Beryllium
U
-
Uranium
N2
-
Nitrogen
H2
-
Hydrogen
TMIn
-
Trimethylindium
TMGa
-
Trimethylgallium
TMAl
-
Trimethylaluminium
PH3
-
Phosphine
AsH3
-
Arsine
RF
-
Radio Frequency
PLL
-
Poly-L-Lysine
ADP
-
Adsorption, Diffusion and Precipitation
eV
-
Electron Volt
ZB
-
Zinc-blende
WZ
-
Wurtzite
xvi
LIST OF SYMBOLS
F
-
Dispersions o f atoms on structure
A
-
Surface area o f a sphere
r
-
Radius o f a sphere
V
-
Volume o f a sphere
d
-
Diameter o f a sphere
n
-
Number o f atoms
N
-
Total number o f atoms
y
-
Surface energy
G
-
Gibbs free energy
T
-
Temperature
P
-
Pressure
Nb
-
Number o f broken bonds
£
-
Bond strength
pa
-
Surface atomic density
a
-
Lattice constant/lattice parameter
Df
-
Number o f degrees freedom o f electron
motions
Dc
-
Number o f confinement directions o f electrons
kT
-
Thermal energy
5
-
Gap between the highest occupied and lowest
unoccupied state
AGr
-
Change in Gibbs free energy
AGV
-
Gibbs free energy difference per unit volume
between solid and liquid phases at same
temperature
xvii
Ysl
-
Substrate-liquid surface energy
Yns
-
Nucleus-solid surface energy
Lv
-
Latent heat o f fusion per unit volume at
equilibrium melting temperature
Tm
-
Melting temperature
AT
-
Undercooling temperature
r*
-
Critical nucleus radius
AG*
-
Critical nucleation barrier
Amv
-
Change o f volume free energy
AMs
-
Change o f interfacial or surface energy
AG
-
Total free energy
J
-
Rate o f nucleation
Jo
-
Available nucleation sites availability
k
-
Boltzman n ’s constant
9
-
Contact angle
Cs
-
Solubility limit in the solid phase
Cl
-
Solubility limit in the liquid phase
D
-
Diffusion coefficient in gaseous phase
U
-
Chemical potential
n
-
Volume per atom
a
-
Surface energy
Mot
-
Bulk chemical potential (infinite radius)
L
-
Length o f the wire
Amot
-
Steady-state supersaturation
vot
-
Steady-state growth velocity at infinite radius
p
-
Pressure o f the system
po
-
Equilibrium pressure
b
-
Coefficient independent o f supersaturation
Z
-
Atomic number
t
-
Time