Institut Penyelidikan dan Teknologi Nano Optoelektronik (INOR) - Tesis

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Synthesis And Characterization Of Lanthanum Oxide-Polyvinyl Alcohol Phosphor Nanofibers For White Light-Emitting Diode (Wled)
(2022-01)
Abdul Wahab, Hasmaifarahatul Hidayah
This study involves the novel application of La2O3-PVA as phosphor nanofibers for white light-emitting diode (WLED). The synthesized of La2O3-PVA phosphor nanofibers by electrospinning process were then applied as phosphor to produce white light. The chromaticity coordinates (CIE), correlated color temperature (CCT) and color rendering index (CRI) value were obtained. The potential of La2O3-PVA phosphor nanofiber was investigated by using three parameters which are different sizes of needle diameter, different thicknesses of nanofiber, and different annealing temperatures. The La2O3-PVA phosphor nanofibers were synthesized on glass substrates using electrospinning process at a distance of 17 cm from the nozzle tip, 11.7 mm diameter of the syringe, 17 kV of voltage supply with a flow rate of 0.5 ml/hour. Five different sizes of needle diameter were used to obtain the most stable and uniform nanofiber. Different thicknesses of La2O3-PVA phosphor nanofibers were prepared using 2, 4, 6, and 10 ml volume of precursor solution with thickness of 2.0, 6.0, 13.0, and 59.0 μm, respectively.
Design Optimization And Characterization Of White Light For Led Street Light Application
(2022-06)
Ying, Jocelynn Kee Xiao
The aim of this study was to evaluate the effects of lens type and shape on the light performance from surface mounted device light emitted diode (SMD LED) street light. Another factor considered was the influence of various shapes of the light emitting surface (LES) on the SMD LEDs and size of the SMD LED on light distribution. Besides, the effects of varying correlated colour temperature (CCT) of the LEDs were also investigated. Optical characterization was carried out using the Goniophotometer (GO-2000) and Integrating Sphere (PCE-200A). DIALux Evo software was used to perform the simulation. Road parameters, such as pole distance of 35 m and pole heights of 8 m on a 7 m width road were used. The road requirement was according to the Tenaga Nasional Berhad (TNB), whereby the street lights must comply with ME4A road classification requirements. The findings showed that Lens E demonstrated a better light performance as compared to Lens A, Lens B, Lens C and Lens D, owing to the rectangular shape of Lens E. The smaller shape of the rectangular lens with classification of Type II-M has lesser light pollution problems. A study comparison between the different CCTs was conducted. Warm White was selected for further investigation into the different shape and size of SMD LEDs as well as key colour for colour mixing.
Deposition And Characterization Of Polyfluorene / Cerium Oxide Organic-Inorganic Thin Films
(2022-07)
Farah Hayati, Haji Ahmad
The investigation of a novel approach by applying an organic polyfluorenes (PFs) layer on inorganic high dielectric constant (k) cerium oxide (CeO2) film for potential use as passivation of silicon (Si)-based metal-oxide-semiconductor (MOS) devices was carried out. Initially, the effects of post-deposition annealing temperatures (400, 600, 800, and 1000 °C) was carried out onto the CeO2 films in order to investigate the changes of temperatures onto structural, morphological, optical and electrical characteristics of the CeO2 films. Subsequently, different composition of PFs was dissolved in toluene and deposited onto indium tin oxide glass substrate to examine the effects of varying PFs composition onto the optical, structural, morphological and electrical properties of the PFs. The optimised PFs composition was then applied as an overlayer stacked on CeO2 films post-deposition annealed at different temperatures to fabricate functional Al/PFs/CeO2/Si/Al hybrid organic-inorganic Si-based MOS device, which was relatively new. Structural, morphological, optical, and electrical properties demonstrated by the stacking PFs on CeO2 films were compared with the samples consisting of single CeO2 films. Outcome of the study revealed that the samples having stacking of PFs on CeO2 films could not surpass the performance provided by single CeO2 films. Nonetheless, the stacking of PFs on CeO2 films provided a breakthrough in the context as a potential high k passivation layer to replace the conventional low k silicon oxide (SiO2) due to the adequately higher k value and comparable current-voltage characteristics with CeO2.
Growth Of Fluorine Doped Zinc Oxide Nanostructures For Ultra-Violet Photodetector Using Modified Chemical Bath-Hydrothermal Method
(2022-09)
Aminu, Muhammad
The main aim of this research work was the use of modified chemical bath- hydrothermal method for the synthesis of undoped and fluorine doped zinc oxide (FZnO) for ultra-violet (UV) photodetector (PD) application. The effect of fluorine (F) concentration in ZnO properties was investigated on Si substrate, which resulted in enhancement of the crystal quality, optical and electrical properties of ZnO at low F concentration. Subsequently, UV metal-semiconductor-metal (MSM) PD was fabricated based on the undoped ZnO and optimized FZnO. When compared to an undoped ZnO device, the photodetection properties of the optimized FZnO device were enhanced appreciably using the UV-light of 395 nm. The value of photocurrent, responsivity, sensitivity, detectivity, rise time and fall time of the undoped ZnO device were 3.61 μA, 0.22 A/W, 9.7 x103%, 2.2 x1019 Jones, 1.9 s and 1.7 s, respectively. The parameters for the FZnO device on the other hand, were increased to 10.52 μA, 0.66 A/W, 1.1x105%, 1.3x1010 Jones, 90 ms and 110 ms, respectively. Hence, FZnO nanorod (NRs) synthesized using modified hydrothermal method revealed outstanding findings which could be extremely beneficial in the design and manufacture of inexpensive UV MSM PD devices for a variety of optoelectronic applications. In addition,
Deposition And Characterisation Of Solution Processed Indium Gallium Zinc Oxide Thin Film On Silicon Substrate
(2022-09)
Nabihah Binti Kasim
This research was conducted with an objective to deposit optimum polycrystalline indium gallium zinc oxide (IGZO) on silicon (Si) substrate by using solution processed method. Specifically, sol-gel method was selected to prepare IGZO precursor solution and spin coating method was used to deposit the film.
Epitaxial Growth Of Gan On Gan Multi Quantum Well For The Deep Green Light Emitting Diode
(2022-10)
Abdul Rais, Shamsul Amir
This work has focused on the effort of fabricating the deep green light emitting diode (LED). First, the multi-quantum well (MQW) that was expected to be able to emit a deep green wavelength was designed and fabricated. The MQW was first grown on a patterned sapphire substrate due to nucleation layer and lattice match which are nearest to the gallium nitride (GaN) substrate. The growth of six pairs of GaN/ InxGa1−xN layer that has 12.16/3.35 nm thickness was successfully carried out. The MQW has low crystal defect even when the indium ratio for InxGa1−xN layer growth was 9 times more than gallium. Previous research shows that a high indium ratio in GaN crystal growth would yield high strain but none of these have been observed. The MQW was later inserted into the full LED structure. The LED was grown on the GaN substrate. The resulting LED has good crystal quality, with dislocation of 8.7x107cm-2 . The photoluminescence (PL) spectrum also gives a good result, 568 nm which is in the deep green region. However, the device needed to be annealed to activate the p-type, and the wavelength blue-shifted greatly, 45nm after the annealing process. This prompted the introduction of the indium pre-flow technique to the later growth of the LED samples.
Epitaxial Growth Of Iii-V Nitrides Based Light Emitting Diodes By Metal Organic Chemical Vapor Deposition
(2023-03)
Samsudin, Muhammad Esmed Alif
This research aims to improve the performance of indium gallium nitride (InGaN) based LEDs and to demonstrate a working aluminum gallium nitride (AlGaN) based LEDs through metal organic chemical vapour deposition epitaxy. The effect of gallium nitride (GaN) nucleation growth temperature, superlattice period, and indium composition on InGaN based LED performance was studied. It was found that growing GaN nucleation at 570°C reduced threading dislocations (TDs) in the overgrown GaN layer (which served as the LED base layer). At 570°C nucleation, larger 3D growths (islands) formed, promoting dislocation inclination, and thus reducing TDs. Subsequently, 20 periods of In0.04Ga0.96N/GaN SLs led to reasonable V-pits size. This increased holes injection into the multiquantum well and hence, improved the LED performance. This research also attempted to find out factors which limit the use of GaN substrates in InGaN based LEDs development over sapphire substrates, particularly pattern sapphire substrate (PSS), which is widely used in many studies, including in this research.
Modelling Of Inhomogeneous Vertical Underwater Optical Wireless Communication Links
(2023-03)
Sabril, Muhammad Safiy
Underwater optical wireless communication (UOWC) is becoming increasingly widespread, moving beyond its former restriction to military and defense applications to now also being used in commercial fields. Despite its growing popularity, designing UOWC systems is challenging due to the complex interaction of light with water. To overcome these challenges, this thesis proposes using inhomogeneous medium in UOWC channel modeling, as opposed to the traditional homogeneous medium model which assumes a single constant value for the ocean’s physical and chemical properties. The thesis presents two inhomogeneous models: Model II, based on the variation in chlorophyll concentration, and Model III, which includes the variation in both chlorophyll concentration and refractive index. These models are compared to Model I, the homogeneous model. To estimate the received power, channel bandwidth, and delay spread, the Monte Carlo (MC) technique was improved to account for medium inhomogeneity.
Spin Coated Gallium Oxide Thin Films And The Effect Of Mo-Doping Concentration On Luminescence Properties
(2023-07)
Wang Tiankun
Beta-type gallium oxide (β-Ga2O3) with ultra-wide band gap energy and good emission property is suitable for optoelectronic applications such as luminescence devices. However, the growth of good quality β-Ga2O3 films using low cost and simple techniques, particularly the sol-gel spin coating technique, is still remains challenging. For luminescence features, undoped and doped β-Ga2O3 emit multicolour emissions due to the multi-energy level of intrinsic vacancies, which is unsuitable for the display application. From the fundamental and engineering point of view, it is worth investigating the above topics. In this project, the β-Ga2O3 thin films synthesized by the sol-gel spin coating method and their photoluminescence were investigated. For the fabrication, the sol-gel spin coating growth conditions, and processes of the β-Ga2O3 thin films on Si and Al2O3 substrates were investigated. Special treatments on the substrate and the coated layer were conducted to improve the uniformity and smoothness of each coated layer and the final deposited film. Different spin coating cycles, and annealing temperatures were also investigated from the morphologic and optical aspects. Finally, a set of samples with 6-layers spin-coated films and annealed under different temperatures, i.e., from 900 °C, to 1100 °C were prepared. These samples were then subjected to an in-depth X-ray diffraction analysis. The results show that the micro strain is not the key factor for the Bragg peaks broadening. To investigate luminescence properties, a series of Mo-doped β-Ga2O3 on Al2O3 were synthesized. A green luminescence band associated with the Mo ion dxz-dyz band transition appeared slowly with the increase of the Mo-doping concentration.
Synthesis And Characterization Of Organic-inorganic Bismuth Halide Perovskites For Photonics Applications
(2023-09)
Heng, Han Yann
The study focused on synthesizing organic-inorganic Bi-halides perovskite compounds using different halides (iodide, bromide, and chloride) in a low-toxic and eco-friendly manner. The aim was to develop Pb-free perovskite materials that are less hazardous for workers in the photonics industry and that can be produced using inexpensive and less complicated processes. In this regards, a hydrophobic phenylammonium cation ([(C6H5)NH3]+) was selected, which is known to contributed to a better sample stability. The synthesis methods involved three different approaches: one step solvent (OSS), OSS added oleic acid (OA), and a non-coordinated solvent method at different temperatures. The stability of the samples were evaluated, and it was observed that the ones synthesized at 60 °C exhibited the best stability for most of the solvents and types of halides. The strong ionic interaction between the BiX63- anion and the short short PhA+ cations in the 0D structure greatly contributed to its stability. In general, the PhA4BiCl6 sample showed the highest stability among the halides due to the stronger attraction between nucleus and electron. The study also involved the growth of a single crystal of PhA4BiI6 using a solvent evaporation technique from which the structure of the zero-dimensional (0D) perovskite compounds was determined, supported by field emission scanning electron microscopy with energy-dispersive X-ray (FESEM-EDX) and Fourier transform infrared (FTIR) spectroscopy results

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