Description
ABSTRACT
Zinc sulfide thin films were grown by the successive ionic layer adsorption and reaction method on soda lime glass and on indium tin oxide covered glass, using diluted solutions of ZnCl2 complexed with triethanolamine (TEA) or ethylenediamine as the cation precursor and a diluted solution of Na2S as the anion precursor. The growth rate of the ZnS film varied between 0.13 and 0.27 nm/cycle. The refractive indices were from 1.95 to 2.23, and the packing densities were from 72 to 90%. The highest refractive indices and packing densities were found in films grown on indium tin oxide with TEA-complexed zinc chloride as the cation precursor. The Zn:S ratio in the films was from 0.89 to 1.08. According to the X-ray diffraction study, the films were polycrystalline and presumably cubic. The EXAFS studies revealed that the crystallinity of the thin film deposited with TEA-complexed ZnCl2 was similar to that of the films deposited with ZnCl2 as the precursor. Annealing slightly improved the quality of the successive ionic layer adsorption and reaction grown ZnS films.
TABLE OF CONTENTS
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRCT
TABLE OF CONTENT
CHAPTER ONE
- INTRODUCTION
- AIM/OBJECTIVE OF THE STUDY
- SCOPE OF THE STUDY
CHAPTER TWO
LITERATURE REVIEW
2.0 LITERATURE REVIEW
2.1 DESCRIPTION OF THIN FILM
2.2 THIN-FILM DEPOSITION
2.3 DIFFERENT KIND OF THIN-FILM DEPOSITION
2.4 GROWTH MODES OF THIN FILMS
2.5 APPLICATIONS OF THIN FILMS
2.6 OVERVIEW OF ZINC SULPHIDE
2.7 APPLICATIONS OF ZINC SULFIDE
2.8 HISTORY BACKGROUND OF ZINC SULPHIDE
2.9 PRODUCTION OF ZINC SULPHIDE
2.10 LABORATORY PREPARATION OF ZINC SULPHIDE
CHAPTER THREE
3.0 METHODOLOGY
3.1 MATERIAL AND METHODOLOGY
CHAPTER FOUR
4.1 RESULT AND DISCUSION
CHAPTER FIVE
5.1 CONCLUSIONS
5.2 REFERENCES
CHAPTER ONE
1.1 INTRODUCTION
In recent times, thin films of metal chalcogenides (selenides, sulphides and tellurides) are currently gaining more interest for applications in various electronic, optoelectronics, nanotechnology and in photonic devices. This because of their tunable properties and ease of fabrication. Nickel selenides has been widely used in different devices including solar cells, photoconductors, coatings and IR detectors. Thin film surface coating are mostly used for efficient conversion of solar radiation into many useful applications. Nickel pigmented aluminum oxide on aluminum is also gaining prominence in the markets because it exhibit advantageous properties like; high tensile strength, low density and corrosion resistance at high temperatures. In the literature, it has been reported that NiSe thin films can be grown using low cost deposition methods including chemical bath deposition, electro-deposition, nano-wire arrays, solvothermal synthesis, hydrothermal synthesis and chemical vapour deposition.
Solution growth technique is more widely used in thin film deposition, compared to other deposition techniques because it is cost effective and also produce high quality thin films. Reports on nickel selenides thin films grown by different methods are relatively rare in the literature hence, the major aim of the present investigation are: (i) To grow thin films of nickel selenides by using a low cost deposition technique, (ii) To characterize the layers using standard characterization techniques, (iii) Investigate the dependence of the optical properties of the films on different concentrations and (iv) To establish their suitability for applications in optoelectronics and photonic devices. The study reported herein is a fundamental step towards improving the properties of nickel selenide thin films hence the dependence of the optical properties on the deposition variable (concentration) are presented.
1.2 OBJECTIVE OF THE STUDY
Zinc sulfide is a wide band gap semiconductor with a range of potential applications in optoelectronic devices. ZnS nanocrystalline thin films are prepared by solution growth technique. The basic principle behind the solution growth technique involves dissolving a material to be grown in an appropriate solvent and then precipitating the crystals out from the supersaturated solution in a controlled manner. Large crystals can be grown by adjusting the rate of crystallization. Various approaches can be utilized to create the supersaturated solution such as isothermal evaporation of the solvent or a gradual cooling of the saturated solution.
1.3 SCOPE OF THE STUDY
The basic principle behind the solution growth technique involves dissolving a material to be grown in an appropriate solvent and then precipitating the crystals out from the supersaturated solution in a controlled manner. Large crystals can be grown by adjusting the rate of crystallization. Various approaches can be utilized to create the supersaturated solution such as isothermal evaporation of the solvent or a gradual cooling of the saturated solution.
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