Mohd Fairus Ahmad
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Preferred name
Mohd Fairus Ahmad
Official Name
Mohd Fairus , Ahmad
Alternative Name
Shahimin, Mohd Faidz Mohamad
Mohamad Shahimin, M. F.
Main Affiliation
Scopus Author ID
57006554500
Researcher ID
B-9547-2018

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Effect of indium pre-flow on wavelength shift and crystal structure of deep green light emitting diodes

2021-01-01 , Shamsul Amir Abdul Rais , Hassan Z. , Bakar A.S.A. , Rahman M.N.A. , Yusuf Y. , Md Taib M.I. , Sulaiman A.F. , Hussin H.N. , Mohd Fairus Ahmad , Mohd Natashah Norizan , Nagai K. , Akimoto Y. , Shoji D.

To produce a deep green (530 nm–570 nm) LED, the suitable indium (In) composition in the InxGa1−xN/GaN multi-quantum well (MQW) structure is crucial because a lower indium composition will shift the wavelength of emission towards the ultraviolet region. In this paper, we clarify the effects of an indium-rich layer to suppress such blue shifting, especially after the annealing process. According to characterizations by the uses of XRD and TEM, narrowing of the MQW layer was observed by the indium capping, while without the capping, the annealing results in a slight narrowing of MQW on the nearest layer to the p-type layer. By adding an indium capping layer, the blue shift of the photoluminescence was also suppressed and a slight red shift to keep green emission was observed. Such photoluminescence properties were consistent with the tiny change of the MQW as seen in the XRD and TEM characterizations.

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Optimization of MEH-PPV Based Single and Double-Layer TOLED Structure by Numerical Simulation

2021-01-01 , Kersenan T. , Zakaria N.F. , Shaari S. , Norhayati Sabani , Juhari N. , Mohd Fairus Ahmad , Rahim A.F.A.

In this work, we simulated and characterized Poly [2-methoxy-5-(2’-ethylhexyloxy)-1, 4-phenylene vinylene] (MEH-PPV) based single and double-layer TOLED by using Silvaco ATLAS device simulator to achieve prominent values of electrical and optical properties of the device. MEH-PPV were used as the emitting layer (EML) in the single-layer, while addition of Poly [(3,4-ethylene dioxythiophene)-poly(styrene sulfonate)] (PEDOT-PSS) as the electron transport layer (ETL) were conducted in double-layer TOLED simulation. The EML and ETL thickness in both structures were varied between 10 – 150 nm, respectively, to observe and understand the underlying physics of the relation in the layer thickness to the electrical and optical characteristics. Furthermore, variation of the EML/ETL thickness ratio from 1:1 to 5:1 (with thickness in between 10 to 50 nm) had also been conducted. From this work, it is understood that the thickness of the EML layer plays the most important role in TOLED, and by balancing the carrier injections and recombination rate in appropriate EML/ETL thickness ratio, the electrical and optical properties can be improved. By optimizing the EML/ETL thickness and thickness ratio, an optimal forward current of 1.41 mA and luminescent power of 1.93e-18 W/μm has been achieved with both MEH-PPV and PEDOT-PSS layer thickness of 10 nm (1:1 ratio), respectively. The results from this work will assist the improvement of TOLED device to be implemented widely in low power and transparent electronic appliances.

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Fabrication of Strontium Titanate thin film with pre-crystallized layer via sol-gel spin coating method

2022-12 , Kelvin Voon Yan Jie , Mohd Fairus Ahmad , Muhammad Mahyiddin Ramli , Safizan Shaari , Arif Mawardi Ismail , Yusran Sulaiman

The technique of pre-crystallized layer is introduced in the strontium titanate (STO) thin film fabrication to improve the coating thickness and the crystallinity. The STO thin films were fabricated on glass substrates via the spin coating method with STO precursor solution that was synthesized through the sol-gel process. The characteristics of the thin films were analyzed through X-ray diffraction (XRD) analysis, profilometry, UV-Vis spectra analysis and scanning electron microscopy (SEM) analysis. In the present study, the samples of 20 layers and 25 layers (deposited on the pre-crystallized layer) exhibited better crystallinity as compared with the samples of 5 layers, 10 layers and 15 layers (without the pre-crystallized layer). The samples of 25 layers exhibited the highest film thickness (224 nm), highest absorbance intensity and the highest XRD peak intensity at 32, 40, 47 and 58°, which represent the planes (110), (111), (200) and (210), respectively. The pre-crystallized layer served as the mechanical support for further layer deposition.

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Temperature effects on electrical and structural properties of MEH-PPV/PEIE OLED Device

2020-06-16 , Nurul Afiqah Nor Ismail , Safizan Shaari , Mohd Fairus Ahmad , Norhayati Sabani , Nurjuliana Juhari , Nor Farhani Zakaria

This paper explores the performance of configuration ITO/MEH-PPV/PEIE/Al OLED under the variations of temperature. The MEH-PPV and MEH-PPV/PEIE thin film were deposited on ITO substrates using spin coating technique with fixed spin speed of 3000 rpm and baked at low temperature ranging from 90 °C to 180 °C, respectively. The surface roughness values for MEH-PPV and MEH-PPV/PEIE films were analysed using AFM with 5 μm ' 5 μm scanning area. The roughness of MEH-PPV thin films were reduced from 2.825 nm to 1.625 nm when temperature increased. Contrary to MEH-PPV/PEIE films where the roughness increased linearly up to 3.397 nm when the temperature increased. The maximum absorption peak spectrum obtained from UV-Visible (UV-Vis) was found at 500 nm to 510 nm when baked temperature were varied. Furthermore, the turn on voltage from J-V characteristics gives no specific pattern across different temperature and agreed with the trend of surface roughness values. The turn-on voltage at T = 150 °C gives the lowest value of 3 V. Overall, the variations of low temperature gives an effects on structural and electrical properties of this OLED configuration.

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The effect of solvents on the performance of organic light-emitting diodes

2020-01-08 , Ismail N.A.N. , Safizan Shaari , Juhari N. , Norhayati Sabani , Mohd Fairus Ahmad , Zakaria N.F.

In this paper, we investigate the solvent effect on the performance of surface roughness, absorption spectrum of MEH-PPV thin films and J-V characteristics for MEH-PPV OLED device. The 5 mg emissive layer of poly [2-methoxy-5(2' -ethylhexyloxy)-1, 4-phenylenevinylene), MEH-PPV was diluted with 1ml toluene and 1 ml different mixture of solvent (80% toluene+20 % chloroform) which gives the concentration of 5 mgml-1 respectively. The surface roughness of MEH-PPV film was reduced to 0.3 nm and the red-shifted maximum peak wavelength value were obtained when mixture solvent was used. However, J-V gives higher turn on voltage ∼17 V for the device used mixture solvent compared to device prepared by toluene solvent. Apparently, the two different combination of aromatic and non-aromatic solvent significantly gives an effect on thin films properties and electrical properties of MEH-PPV OLED device.

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A study on electrical performance of SiC-based self-switching diode (SSD) as a high voltage high power device

2023-12 , N. Z. A. A. Sha’ari , Nor Farhani Zakaria , Shahrir Rizal Kasjoo , Mohd Natashah Norizan , Ili Salwani Mohamad , Mohd Fairus Ahmad , Shamsul Amir Abdul Rais , Banu Poobalan , Norhayati Sabani , A. F. A. Rahim

The Self-switching Diodes (SSDs) have been primarily researched and used in low-power device applications for RF detection and harvesting applications. In this paper, we explore the potential of SSDs in high-voltage applications with the usage of Silicon Carbide (SiC) as substrate materials which offers improved efficiency and reduced energy consumption. Optimization in terms of the variation in the interface charges, metal work function, and doping concentration values has been performed by means of a 2D TCAD device simulator. The results showed that the SSD can block up to 600 V of voltage with an optimum interface charge value of 1013 cm-2, making them suitable for higher voltage applications. Furthermore, it also found that the work function of the metal contact affected the forward voltage value, impacting the current flow in the device. Variation in doping concentrations also resulted in higher breakdown voltages and significantly increased forward current, leading to an increased power rating of 27 kW. In conclusion, the usage of 4H-SiC-based SSDs shows a usable potential for high-voltage applications with optimized parameters. The results from this research can facilitate the implementation of SSD in the development of high-power semiconductor devices for various industrial applications.

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Production of low temperature synthetic graphite

2023-04 , Anis Syafiqa Rosman , Ranjitha Navalan , Muhammad Mahyiddin Ramli , Norizah Abd Karim , Mohd Fairus Ahmad , Shazlina Johari , Norshamsuri Ali @ Hasim , Nurul Huda Osman

Synthetic graphite is a material consisting of graphitic carbon which has been obtained by graphitizing a non-graphitic carbon. The growth in demand, particularly in customizing properties for certain usage has brought about research on viable alternative, low-cost, and environmentally pleasant synthetic graphite production. Biomass wastes are amongst appealing carbon precursors which have been broadly checked out as replacement carbon for graphite production. This research aimed to synthesize synthetic graphite from oil palm trunks at low temperatures (500 °C, 400 °C and 300 °C) under controlled conditions to determine the physical properties and properties of the graphite obtained. After the heat treatment process, the obtained samples were then characterized by using XRD, SEM and RAMAN characterizations. Based on SEM and RAMAN characterization, it can be seen that graphite that undergoes a 500 °C pyrolysis process shows the best results compare to graphite that undergoes a pyrolysis process at the temperatures of 300 °C and 400 °C. The graphite flakes and the peaks obtained for 500 °C graphite are obviously present. For XRD characterization, the best samples at 500 °C were chosen to be characterized. From the results, the sample shows slight behavior imitating the commercialized graphite. Hence, from the characterizations of the samples, it can be concluded that the best synthetic graphite produced was from the oil palm trunks heated at 500 ° C

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A Study on Electrical Performance of SiC-based Self-switching Diode (SSD) as a High Voltage High Power Device

2023-12-01 , Sha’ari N.Z.A.A. , Nor Farhani Zakaria , Shahrir Rizal Kasjoo , Ahmad M.F. , Mohd Natashah Norizan , Ili Salwani Mohamad , Mohd Fairus Ahmad , Shamsul Amir Abdul Rais , Banu Poobalan , Norhayati Sabani

The Self-switching Diodes (SSDs) have been primarily researched and used in low-power device applications for RF detection and harvesting applications. In this paper, we explore the potential of SSDs in high-voltage applications with the usage of Silicon Carbide (SiC) as substrate materials which offers improved efficiency and reduced energy consumption. Optimization in terms of the variation in the interface charges, metal work function, and doping concentration values has been performed by means of a 2D TCAD device simulator. The results showed that the SSD can block up to 600 V of voltage with an optimum interface charge value of 1013 cm-2, making them suitable for higher voltage applications. Furthermore, it also found that the work function of the metal contact affected the forward voltage value, impacting the current flow in the device. Variation in doping concentrations also resulted in higher breakdown voltages and significantly increased forward current, leading to an increased power rating of 27 kW. In conclusion, the usage of 4H-SiC-based SSDs shows a usable potential for high-voltage applications with optimized parameters. The results from this research can facilitate the implementation of SSD in the development of high-power semiconductor devices for various industrial applications.

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The structural and electrical characterization of PEDOT:PSS/MEH-PPV doped with PEIE OLED fabricated using spin coating technique

2020-01-08 , Juhari N. , Shukri N.I.A. , Norhayati Sabani , Safizan Shaari , Mohd Fairus Ahmad , Nor Farhani Zakaria

This paper investigates the performance of the uniformity and absorption spectrum of MEHPPV+PEIE thin films also the electrical properties for configuration of ITO/PEDOT: PSS/MEH+PEIE/Al. The sample used 0.5 wt % of PEDOT: PSS solution while 5 mgml-1 concentration of MEH-PPV solution was doped with four different concentrations of PEIE with values of 0.1 wt%, 0.3 wt%, 0.5 wt% and 0.7 wt% respectively. The untreated PEDOT: PSS and MEH-PPV+PEIE was deposited using spin coating technique at a fixed spun speed of 3000 rpm to obtain smooth surface roughness thin film. The root mean square (RMS) value, absorption spectrum and current density (A/cm-2) of the PEDOT: PSS and MEH-PPV+PEIE films were analyzed using Atomic Force Microscope (AFM), UV-Visible (UV-Vis) Spectrophotometer and Semiconductor Parametric Analyzer (SPA), respectively. The surface roughness of the films were linearly increased when the dopant concentration increased with the maximum RMS value of ∼4.74 nm. Besides, absorption peak wavelength also was red-shifted from 500 nm to 551 nm under an influence of PEIE dopant concentrations. However, the turn on voltage gives no significant trend when dopant concentration was increased but the emission of the light was emitted when the voltage was below 8 V. Among four different dopant concentrations of MEH-PPV+PEIE, the brighter light emission was observed at 0.3 wt% of PEIE. Apparently, the concentration of dopant solution gives a significant contribution to the performance of OLED in terms of structural, optical and electrical properties.

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Photoluminescence measurement of triplet sensitizer-emitter solution using a customized 3D-printed sample holder

2024-06 , Kelvin Voon Yan Jie , Safizan Shaari , Mohd Fairus Ahmad , Nor Farhani Zakaria , Norhayati Sabani

This study explores the photoluminescence (PL) measurement of triplet sensitizer-emitter (TSE) solutions using a custom 3D-printed sample holder, within the context of triplet-triplet annihilation based molecular photon upconversion (TTA-UC) systems targeting the Vis-to-UV spectral region. TTA-UC converts low-energy visible photons to higher-energy ultraviolet (UV) photons, holding promise for solar energy harvesting and photonics applications. Two TSE couples, 4CzIPN/TP and 4CzIPN/QP, were investigated, and their upconverted fluorescence spectra showed peaks at 344 nm and 354 nm / 370 nm, respectively, confirming efficient upconversion capabilities. The 3D-printed sample holder facilitated reproducible PL measurements, enabling the calculation of quantum yields (ΦUC). The 4CzIPN/TP and 4CzIPN/QP couples exhibited low quantum yields (0.028% and 0.043%, respectively), suggesting the need for improved deoxygenation methods to enhance the triplet-triplet annihilation process and overall quantum efficiency. Despite modest yields, successful UV upconverted fluorescence observation underscores the feasibility of the Vis-to-UV TTA-UC system. This study provides insights into TTA-UC optimization and demonstrates the utility of the 3D-printed sample holder for affordable and precise PL measurements, paving the way for future advancements in photonics and solar energy applications.

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