ABSTRACT
CuS:ZnS, CdS:ZnS, AlS:ZnS and SnS:ZnS multilayer thin films were synthesized on glass substrates using two solution based methods: successive ionic layer adsorption and reaction (SILAR) and solution growth technique(SGT). The deposited alloyed samples were annealed between 373K and 523K using Master Chef Annealing Machine. The crystallographic studies were done using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The XRD pattern of CuS:ZnS alloyed thin films of samples P5 and P6show well defined peaks. The XRD pattern of CdS:ZnS alloyed thin films of sample Q5 show well defined peaks. The XRD pattern of AlS:ZnS alloyed thin films of samples R1 and R6 show well defined peaks. The XRD pattern of SnS:ZnS alloyed thin films of sample T6 show well defined peaks which reveals the samples are polycrystalline in nature. Their grain sizes were calculated. Rutherford backscattering spectroscopy (RBS) analysis confirmed the percentage of the elements of copper, cadmium, aluminium, tin, zinc and sulphur in the alloyed thin films. The surface electron microscopy result indicates the microstructure of the deposited alloyed thin films. The optical characterization was carried out using spectrophotometer. The spectral transmittance of samples P0, P1, P2, P3, and P4 show maximum transmissions of 44%, 98%, 78%, 96% and 57% at wavelength of about 900nm throughout the studied region and band gap of 3.98eV, 4.20eV, 4.18eV, 4.21eV and 4.15eV respectively. The spectral transmittance of samples Q0, Q1, Q2, Q3, and Q4 show maximum transmissions of 80%, 90%, 95%, 88% and 97% at wavelength of about 900nm, 900nm, 400nm, 650nm and 470nm within the studied region and band gap of 4.20eV, 4.21eV, 4.15eV and 4.19 respectively. The spectral transmittance of samples R0, R2, R3, R4, and R5 show maximum transmissions of 67%, 82%, 88%, 97% and 70% at wavelength of about 900nm within the studied region and band gap of 4.02eV, 4.20eV, 4.25eV, 4.35eV and 4.15eV respectively. The spectral transmittance of samples T0, T2, T3, T4, and T5 show maximum transmissions of 35%, 40%, 37%, 80% and 82% at wavelength of about 900nm within the studied region and band gap of 3.68eV, 3.8eV, 3.7eV, 3.98eV and 3.9eV respectively. Other optical properties that were investigated are; absorbance, reflectance, absorption coefficient, extinction coefficient, refractive index, optical conductivity and dielectric constants. From the qualities, these sulphide multilayer thin films may be found useful in window coating, vulcanization, etc.
TABLE OF
CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of Content vi
List of Tables ix
List of Figures x
Abstract xiii
CHAPTER
1: INTRODUCTION
1.1 Preamble 1
1.2 Alloy 2
1.3 Aim/Objectives 3
1.4 Motivation of Study 3
1.5 Significance
of the Study 4
1.6 Scope of Study 4
CHAPTER
2: LITERATURE REVIEW
2.1 Energy Bands 6
2.1.1 Conduction energy band 6
2.1.2 Insulator energy bands 7
2.1.3 Semiconductor energy band 7
2.2 Solar energy 12
2.2.1 The solar spectrum 13
2.2.2 Solar Radiation 15
2.3 Photovoltaic Effect 16
2.3.1 Solar cell 17
2.3.2 Types of solar cells 18
2.3.3 The solar panel 18
2.4 Thin Film Science 19
2.4.1 Description of thin film materials 19
2.4.2 Types of thin film 20
2.4.3 Applications
of thin films 23
2.5 Deposition Techniques of Sulphide Alloy
Thin Films 27
2.5.1 Chemical deposition techniques 28
2.5.1.1 Chemical bath deposition (CBD) 28
2.5.1.2 Successive ionic layer adsorption and reaction
(SILAR) method 29
2.5.1.3
Chemical vapor deposition (CVD) 30
2.5.1.4 Plating 31
2.5.1.5 Spray pyrolysis
31
2.5.1.6
Electrodeposiition 32
2.5.2 Physical deposition 34
2.5.2.1 Sputtering 35
2.5.2.2 Pulsed laser deposition 35
2.5.2.3 Thermal
evaporatoion 35
2.5.2.4
Electron beam evaporation 36
2.5.2.5 Electrohydrodynamic
deposition 36
2.6 Description of Materials Characterization
Techniques 37
2.6.1 Structural and morphological property
studies 37
2.6.1.1 X-ray diffraction (XRD) 37
2.6.1.2 Scanning
electron microscopy (SEM) 38
2.6.2 Optical property studies 39
2.6.2.1 UV- Visible
spectroscopy 39
2.7 Annealing 44
2.8 Effect of Material Properties on
Transmitting Thin Films 45
CHAPTER
3: MATERIALS AND
EXPERIMENTAL METHODS
3.1 Description of Deposition Techniques Used 47
3.2 Preparation of Sulphide Alloy Thin Films 47
3.2.1 Apparatus used for the deposition 47
3.2.2 Substrate preparation 48
3.2.3 Deposition of sulphide multilayer thin films
using dual solution synthesis
(SGT and SILAR) 48
3.2.3.1 Deposition of CuS:ZnS thin films 49
3.2.3.2 Deposition of CdS:ZnS thin films 50
3.2.3.3 Deposition of AlS:ZnS thin films 50
3.2.3.4 Deposition of SnS:ZnS thin films 51
3.3 Characterization of Deposited Thin Films 52
3.3.1 Optical
characterization 52
3.3.2 X-ray diffractometer (XRD) 52
3.3.3 Scanning electron microscopy (SEM) 52
3.3.4 Rutherford backscattering spectrometry (RBS) 53
CHAPTER
4: RESULTS AND
DISCUSSION
4.1 Composition and Thickness of the
Deposited Thin Films 54
4.2 Structural Properties 82
4.2.1 Crystallographic studies of the deposited
samples 82
4.2.2 Microstructure of the Deposited Samples 91
4.3 Optical Properties 95
4.3.1 CuS:ZnS thin films 95
4.3.2 CdS:ZnS
thin films 103
4.3.3 AlS:ZnS thin films 111
4.3.4 SnS:ZnS thin films 118
4.4 Possible Areas of Application of the
Deposited Thin Films 125
CHAPTER
5: CONCLUSION AND
RECOMMENDATIONS
5.1 Conclusion 126
5.2 Recommendations 127
5.3 Contribution to Knowledge 127
REFERENCES 128
LIST OF TABLES
4.1: The elements in sample P1 of CuS:ZnS 55
4.2: The
elements in sample P2 of CuS:ZnS 57
4.3: The
elements in sample P3 of CuS:ZnS 59
4.4: The elements in sample Q2 of CdS:ZnS 62
4.5: The
elements in sample Q3 of CdS:ZnS 64
4.6: The
elements in sample Q4 of CdS:ZnS 66
4.7: The elements in sample R3 of AlS:ZnS 69
4.8: The elements in sample R4 of AlS:ZnS 71
4.9: The
elements in sample R5 of AlS:ZnS 73
4.10: The elements in sample T2 of SnS:ZnS 76
4.11: The
elements in sample T3 of SnS:ZnS 78
4.12: The elements in sample T4 of SnS:ZnS 80
4.13: XRD results of CuS:ZnS alloyed thin film 83
4.14: XRD results of CuS:ZnS alloyed thin film 85
4.15: XRD
results of AlS:ZnS alloyed thin film 87
4.16: XRD
results of SnS:ZnS alloyed thin film 89
LIST OF FIGURES
2.1: Schematic energy bands of (a) a conductor,
(b) an insulator, and (c) a semiconductor 10
2.2(a): Schematic Diagram of a p-n junction 11
2.2(b): Energy band diagram of a p-n junction 11
2.3: The
Spectral irradiance 14
2.4: Path length of sunlight through the
atmosphere 15
2.5:
Schematic diagram of chemical bath
deposition (CBD) 29
2.6: Schematic
diagram of CVD technique 30
2.7: Schematic diagram of spray pyrolysis 32
2.8(a): Typical set-up of three electrode system of
electrodeposited technique(wikipedia.org, 2021) 33
2.8(b): Pictorial
view of a typical two electrode set-up of electrodeposited
technique 33
2.9: Thermal
evaporation technique set-up 36
2.10: Basic schematic diagram for construction of
a spectrophotometer 39
4.1: The
composition of sample P1 with thickness 247.5nm, of CuS:ZnS
measured by RBS 56
4.2: The composition of
sample P2 with thickness 238nm, of CuS:ZnS
measured by RBS 58
4.3: The
composition of sample P3 with thickness 247.5nm, of CuS:ZnS
measured by RBS 60
4.4: The
composition of sample Q2 with thickness 298.6nm, of CdS:ZnS
measured by RBS 63
4.5: The
composition of sample Q3 with thickness 160nm, of CdS:ZnS
measured by RBS 65
4.6: The
composition of sample Q4 with thickness 190nm, of CdS:ZnS
measured by RBS 67
4.7: The composition of sample R3 with
thickness 140nm, of CdS:ZnS
measured by RBS 70
4.8: The
composition of sample R4 with thickness 171nm, of CdS:ZnS
measured by RBS 72
4.9: The
composition of sample R5 with thickness 300nm, of CdS:ZnS
measured by RBS 74
4.10: The composition
of sample T2 with thickness 360nm, of SnS:ZnS
measured by RBS 77
4.11: The composition
of sample T3 with thickness 440nm, of SnS:ZnS
measured
by RBS 79
4.12: The composition
of sample T4 with thickness 440nm, of SnS:ZnS
measured
by RBS 81
4.13: XRD
pattern of CuS:ZnS alloyed thin films of samples P5 and P6
annealed at 150◦C and 200◦C respectively 84
4.14 XRD
pattern of CdS:ZnS alloyed thin film of samples Q5 annealed at 200◦C 86
4.15: XRD
pattern of AlS:ZnS alloyed thin films of samples R1 and R6
annealed at 200◦C and 250◦C respectively 88
4.16: XRD
pattern of SnS:ZnS alloyed thin film of samples T6 annealed at
200◦C 90
4.17: Optical
micrograph of CuS:ZnS alloyed thin films of samples P5 and P6 91
4.18: Optical
micrograph of CdS:ZnS alloyed thin films of samples Q5 and Q6 92
4.19: Optical
micrograph of AlS:ZnS alloyed thin films of samples R1 and R6 93
4.20: Optical
micrograph of SnS:ZnS alloyed thin films of samples T1 and T6 94
4.21: Transmittance
spectra of CuS:ZnS thin films annealed at different
temperatures 97
4.22: Absorbance
spectra of CuS:ZnS thin films annealed at different
temperatures 97
4.23: Reflectance
spectra of CuS:ZnS thin films annealed at different
temperatures 98
4.24: Plot
of real dielectric constant versus photon energy for CuS:ZnS
thin films 98
4.25: Plot
of optical conductivity versus photon energy for CuS:ZnS thin
films 99
4.26: Plot of optical imaginary dielectric
constant versus photon energy for
CuS:ZnS thin films 99
4.27: Plot
of extinction coefficient versus photon energy for CuS:ZnS thin
films 100
4.28: Plot of (αhυ)2 versus photon
energy for CuS:ZnS thin films 101
4.29: Plot
of absorption coefficient versus photon energy for CuS:ZnS thin
films 102
4.30: Plot
of refractive index versus photon energy for CuS:ZnS thin films 102
4.31: Transmittance
spectra of CdS:ZnS thin films annealed at different
temperatures 105
4.32: Absorbance
spectra of CdS:ZnS thin films annealed at different
temperatures 105
4.33: Reflectance
spectra of CdS:ZnS thin films annealed at different
temperatures 106
4.34: Plot
of real dielectric constant versus photon energy for CdS:ZnS thin
films 106
4.35: Plot
of optical conductivity versus photon energy for CdS:ZnS thin
films 107
4.36: Plot
of optical imaginary dielectric constant versus photon energy for
CdS:ZnS thin films 107
4.37: Plot
of extinction coefficient versus photon energy for CdS:ZnS thin
films 108
4.38: Plot of (αhυ)2 versus photon
energy for CdS:ZnS thin films 109
4.39: Plot
of absorption coefficient versus photon energy for CdS:ZnS thin
films 110
4.40: Plot of refractive index versus photon
energy for CdS:ZnS thin
films 110
4.41: Transmittance
spectra of AlS:ZnS thin films annealed at different
temperatures 112
4.42: Absorbance
spectra of AlS:ZnS thin films annealed at different
temperatures 112
4.43: Reflectance
spectra of AlS:ZnS thin films annealed at different
temperatures 113
4.44: Plot
of real dielectric constant versus photon energy for AlS:ZnS
thin
films 113
4.45 Plot
of optical conductivity versus photon energy for AlS:ZnS thin
films 114
4.46 Plot
of optical imaginary dielectric constant versus photon energy for
CuS:ZnS thin films 114
4.47: Plot
of extinction coefficient versus photon energy for AlS:ZnS thin
films 115
4.48: Plot
of (αhυ)2 versus photon energy for AlS:ZnS thin films 116
4.49: Plot
of absorption coefficient versus photon energy for AlS:ZnS thin
films 117
4.50: Plot
of refractive index versus photon energy for AlS:ZnS thin films 117
4.51: Transmittance
spectra of SnS:ZnS thin films annealed at different
temperatures 119
4.52: Absorbance spectra of SnS:ZnS thin films
annealed at different
temperatures 119
4.53: Reflectance
spectra of SnS:ZnS thin films annealed at different
temperatures 120
4.54: Plot
of real dielectric constant versus photon energy for SnS:ZnS
thin films annealed at different temperatures 120
4.55: Plot
of optical conductivity versus photon energy for SnS:ZnS thin films 121
4.56: Plot of optical imaginary dielectric
constant versus photon energy for
SnS:ZnS thin films 121
4.57: Plot
of extinction coefficient versus photon energy for SnS:ZnS thin films 122
4.58: Plot
of (αhυ)2 versus photon energy for SnS:ZnS thin films 123
4.59: Plot
of absorption coefficient versus photon energy for CuS:ZnS thin
films 124
4.60: Plot
of refractive index versus photon energy for CuS:ZnS thin films 124
CHAPTER
1
INTRODUCTION
1.1 PREAMBLE
Thin films now occupy a
prominent place in research and solid state technology. In an expanding variety
of applications in the various electronic and optoelectronic devices, much
interest has been attracted as a result of the use of thin film semi-conductors
due to their low cost of production. A variety of methods has been used to
prepare a high quality transition metal chalcogenides. Each technology has its
limitation. Therefore, in order to grow sulphide multilayer thin films with
desirable shape and structure, solution growth and successive ionic layer
absorption and reaction technique were employed, which combine simplicity and
low cost with potential for large scale production (it does not require
sophisticated equipment)
Transition metal
chalcogenites: oxides, sulfides, selinides and tellurides are important technological
materials. In this study the effect of varying annealing temperature was
investigated in order to broaden the range of application. Although there have
been numerous papers published reporting the preparation of chalcogenide thin
films using solution growth and successive ionic layer absorption and reaction
technique respectively, Kaur et al.
pointed out that the process has remained recipe oriented with little
understanding of the kinetics of the process. There is therefore, a need for
careful investigation of a substrate using two techniques - solution growth
technique and successive ionic layer absorption and reaction to identify the condition
that favours high quality coherent deposits.
1.2 ALLOY
An alloy is a mixture of
metal(s) and another element. The metal is usually called the primary metal or
the base metal, and the name of this metal may also be the name of the alloy.
Alloys are defined by metallic bonding character. An alloy may be a solid
solution of metal elements (a single phase) or a mixture of metallic phases
(two or more solutions). An alloy is distinct from an impure metal in that, with
an alloy, the added elements are well controlled but are often considered
useful. The mechanical properties of alloys will often be quite different from
those of its individual constituents. Although the elements of an alloy usually
must be soluble in the liquid state, they may not always be soluble in the
solid state (Callister and Rethwisch, 2010). If the metals remain soluble when
solid, the alloy forms a solid solution, becoming a homogeneous structure
consisting of identical crystals, called a phase. As the mixture cools, the
constituents becomes solids, they may separate to form two or more different
types of crystals, creating a heterogeneous microstructure of different phases,
some with one or more constituent than the other phase has.
However, in other alloys,
the insoluble elements may not separate until after crystallization occurs. If
cooled very quickly, they crystallize as a homogeneous phase, but they are
supersaturated with the secondary constituents. As time passes, the atom of
these supersaturated alloys can separate from the crystal lattice, becoming
more stable, and form a second phase that serve to reinforce the crystals
internally. Some alloys such as electrum which is an alloy consisting of silver
and gold, occur naturally.
The primary metal is
called the base, the matrix, or the solvent. The secondary constituents are
often called solutes. If there is a mixture of only two types of atoms (not
regarding impurities) such as copper-nickel alloy, it is called a binary alloy.
If there are three types of atoms forming the mixture, such as iron, nickel and
chromium, then it is called a ternary alloy. An alloy with four constituents is
a quaternary alloy, while a five part alloy is termed quinary alloy.
1.3 AIM/OBJECTIVES
The aim of this study is
the to investigate the influence of varying annealing temperature on solution
growth and successive ionic layer absorption and reaction depostited multilayer
sulphide (CuS:ZnS, CdS:ZnS, AlS:ZnS and SnS:ZnS)thin films to deduce a suitable
thin film for possible applications.
In order to achieve the
aim of this study, the following objectives were adopted:
i prepare
ZnS bath by Solution growth technique.
ii grow
other sulphide alloy (CuS, SnS, CdS, AlS) thin films by Successive ionic layer
absorption and reaction technique and dip into already prepared ZnS bath.
iii anneal
the deposited samples at various temperatures.
iv characterize
the deposited samples.
v study the influence of varying annealing temperature.
vi identify possible applications of the films deposited.
1.4 MOTIVATION OF STUDY
Energy is the pre-requisite for creation of wealth and
sustainability of development. The importance of energy in economic development
has been recognised historically but the equitable distribution of energy
amongst the masses has always been a matter of great concern. Sustainability of
development can be ensured by use of sustainable energy resources which are
environment-friendly and available in abundance. And the only possible answer
to this problem is Renewable Energy. Renewable Sources include wind, biomass,
geothermal, hydro-power, ocean thermal and last but not the least solar energy.
Owing to the exponential growth of global population, the need for energy is going
to be doubled in coming fifty years. But this huge demand can be met by solar
energy alone if properly harnessed. With the advancement in the field of
nanotechnology and material science, a huge number of motivated researchers are
exploring this vast area of science and making great contribution towards
different fabrication techniques to produce a cheap, sustainable, environment friendly,
highly efficient solar cell and other nanoelectronic devices.
1.5 SIGNIFICANCE OF THE STUDY
The need and the desire to produce high quality
sulphide thin films with combinational qualities in the areas of applications
led to the choice of the study on dual solution synthesis and characterization
of CuS:ZnS, CdS:ZnS, AlS:ZnS and SnS:ZnS multilayer thin films for possible
applications.
The outcome of the study will provide appropriate
process for large scale production of high quality multilayer thin films.
1.6 SCOPE OF STUDY
This study encompasses the preparation of multilayer
sulphide (CuS:ZnS, CdS:ZnS, AlS:ZnS and SnS:ZnS) thin films using two solution
based methods: solution growth and SILAR technique. Reagents required include:
copper sulphate (CuSO4), cadmium chloride (CdCl2),
aluminium chloride (AlCl2), tin chloride (SnCl2), zinc
chloride (ZnCl2), ammonia (NH3) and thiourea (CS(NH3)).
The deposited samples were annealed using Master Chef annealing machine at
varying temperatures. X-ray diffractometer (XRD) and scanning electron
microscope (SEM) were used to determine the structural properties of the
samples, Rutherford Backscattering Spectroscope (RBS) was used to determine the
composition and thickness of the deposited samples and spectrophotometer was
used to determine the optical properties of the samples.
Click “DOWNLOAD NOW” below to get the complete Projects
FOR QUICK HELP CHAT WITH US NOW!
+(234) 0814 780 1594
Login To Comment