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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  • Publication
    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.
  • Publication
    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.
  • Publication
    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.
  • Publication
    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.
  • Publication
    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.
  • Publication
    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.
  • Publication
    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.
  • Publication
    Development of varied CMOS ring oscillator topologies in 0.13-μm CMOS technology
    ( 2013)
    Sohiful Anuar Zainol Murad
    ;
    Mohamad Shahimin Mukhzeer
    ;
    Rizalafande Che Ismail
    ;
    Mohd Fairus Ahmad
    ;
    Sapawi Rohana
    This paper presents varied CMOS ring oscillator topologies using Silterra 0.13-µm Process. Three topologies of ring oscillators have been designed which is the single-ended ring oscillator, differential ring oscillator and ring oscillator based variable resistor for 2.4 GHz wireless applications. The proposed designs consist of five stages delay cell. The simulation results show that a single-ended ring oscillator obtained the lowest power consumption of 0.41 mW, while differential oscillator achieves phase noise of −64.44 dBc/Hz at 1 MHz offset frequency. However, ring oscillator based variable resistor did not achieve any significant improvement. The proposed design is oscillates at 2.4 GHz.
  • Publication
    Copper doping effect in the back surface field layer of CdTe thin film solar cells
    ( 2024-02-01)
    Nur Irwany Ahmad
    ;
    Kiong T.S.
    ;
    Doroody C.
    ;
    Rahman K.S.
    ;
    Mohd Natashah Norizan
    ;
    Mohd Fairus Ahmad
    ;
    Kar Y.B.
    ;
    Harif M.N.
    ;
    Amin N.
    In this work, the Solar Cell Capacitance Simulator (SCAPS-1D) is employed to evaluate the characteristics of CdTe thin films with ZnTe as the Back Surface Field (BSF) layer and estimate the effective copper doping ratio at both the atomic scale and the device operational response perspective. The electrical characteristics of ZnTe, at varying levels of copper doping, were derived using density functional theory (DFT) by applying the generalized gradient approximation (GGA) and Hubbard U corrections (DFT+U). The performance of ZnTe with different Cu concentrations as a BSF layer was evaluated by analysing the values of four key parameters that are open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF), and conversion efficiency (η). The results indicate that an increase in Cu concentration from 0% to 3%, 6%, 10%, and 12% resulted in a reduction of the energy band gap. Specifically, the energy band gap decreased from 2.24 eV to 2.10 eV, 1.98 eV, 1.92 eV, and 1.88 eV, respectively. Optimal Cu doping promotes the favourable shift in the valence band maxima (VBM) and formation of p + -ZnTe, lowering thermionic emission and improving carrier lifetime, which results in an improved ohmic contact, η = 18.73% for 10% of Cu content. Excessive doping in contrast degraded the overall device performance by forming an unmatched carrier band offset at the front interface with CdS, increasing the acceptor type defect and CdTe compensation rate. Overall, the findings suggest that incorporating a controlled level of Cu, which in this case is around 10%, promotes the efficiency and stability of the proposed CdTe device configuration to a certain extent.
  • Publication
    Low-cost tilt monitoring system for spin coater calibration
    ( 2024-02-08)
    King C.Y.
    ;
    Mohd Fairus Ahmad
    ;
    Norhayati Sabani
    ;
    Mohd Natashah Norizan
    ;
    Nor Farhani Zakaria
    ;
    Nurjuliana Juhari
    ;
    Shamsul Amir Abdul Rais
    ;
    Amin M.R.R.M.
    The spin coating process became the most widely used technique in the fabrication industry for thin film coating on a substrate by centrifugal force. Unfortunately, frequent usage of spin coater might induce a tilted surface of the chuck (i.e. the sample holder). A tilted chuck might induce inhomogeneity of the coating layer. Among the machine's calibration techniques, nullifying the tilt before the spin coating process is the most important step. However, to our knowledge, none of the spin coaters was introduced with the chuck's tilt monitoring during the spin coating process. Thus, investigating the discrete condition during the spin coating process is necessary. In this work, the tilt monitoring system for the spin coater was implemented based on an Arduino Uno microcontroller and distance sensor. A spin coater has been implemented to test the tilt surface monitoring during spinning ranges from 350rpm to 1000rpm. The measurement was done under two conditions: flat (0.00 degrees) and tilted (5.71 degrees). The setup was able to measure up to 0.01 degrees of the tilt.