Mohd Fairus Ahmad
Thumbnail Image
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

Research Output

Filters

24
Reset filters

Settings
Now showing 1 - 10 of 24
  • 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
    The efficiency effect of dye sensitized solar cell using different ratio of organic polymer doped titanium dioxide at different annealing process temperature
    ( 2020-01-08)
    Norhisamudin N.A.
    ;
    Norhayati Sabani
    ;
    Rosli N.
    ;
    Mohd Fairus Ahmad
    ;
    Juhari N.
    ;
    Safizan Shaari
    ;
    Zakaria N.
    Titanium Dioxide (TiO2) is one of the main materials in Dye Sensitized Solar Cell (DSSC). It is well known with its property of good optical transmittance and its mesoporous surface that can absorb generous amount of dye. In this study, TiO2 is fabricated using spin coating technique that leads to the uniform thickness of TiO2 layer. The thickness of the TiO2 can be controlled layer by layer using same technique to get an optimized surface that can lead to better performance of DSSC. In order to achieve this, the surface roughness of TiO2 must be as high as possible. Therefore, the organic material which is Poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene-vinylene (MEH-PPV) is used as medium to increase the mesoporous roughness structure of TiO2 nanocrystal film for DSSC. MEH-PPV is doped into the TiO2 using 0.5 mg/ml with different temperatures of 100°C and 450°C. Different temperatures of MEH-PPV will lead to the different surface structures for TiO2 thin film. The ratio of TiO2:MEH-PPV used were 1:1 and 2:1. The surface of TiO2 thin film was characterized using Atomic Force Microscope (AFM). The efficiency was obtained using Solar Simulator based on the voltage and current flow. Based on the results, the increment of surface roughness is about 21% for the different ratio at various temperatures. The optimum temperature and suitable ratio of TiO2:MEH-PPV was obtained via annealing process at 450°C with the ratio of 2:1. It gives the highest efficiency which is 0.1266%. These two important findings yield good mesoporous surface of TiO2 thin film.
  • Publication
    Modified CMFB circuit with enhanced accuracy for data converter application
    ( 2013)
    Mohd Fairus Ahmad
    ;
    Sohiful Anuar Zainol Murad
    ;
    Mukhzeer Mohamad Shahimin
    ;
    Shamsul Amir Abdul Rais
    ;
    Ahmad Fariz Hasan
    Enhanced feedback voltage of common mode feedback (CMFB) circuit is designed in this work for CMOS data sampling application using 0.18-μm Silterra process technology. The double error detecting point circuit is employed to associate with the feedback point in order to prevent the undesired voltage common mode at the output of operational transconductance amplifier (OTA). The PMOS input transistor for injecting the common mode voltage is used to fit in the limitation of voltage division in low power design. The feedback voltage is strongly pushed to have a stable value as to make the outputs of differential amplifier circuit swing at a nearly constant voltage at 1.2 V for enhancing accuracy of data converter.
  • Publication
    Characterization of doped ZnO thin film for Ammonia gas sensing application
    (Institute of Physics, Polish Academy of Sciences, 2023)
    Shazlina Johari
    ;
    Fatin Amira Hasbullah
    ;
    Anis Syafiqa Rosman
    ;
    Muhammad Mahyiddin Ramli
    ;
    Mohd Fairus Ahmad
    ;
    Norizah Abd Karim
    ;
    Nurul Huda Osman
    ;
    D. Darminto
    ;
    Ali Hussain Reshak
    ;
    Sebastian Garus
    This paper reports on the characterization of Sn- and Al-doped zinc oxide thin film for potential ammonia gas detection. The sol–gel method has been used to deposit the dopant onto the glass substrate at an annealing temperature of 500◦C for three different doping concentrations, which are 0.5, 1.0, and 1.5 at.%. The method used to produce this thin film is sol–gel, as it is cheap, easy, and can be employed at low temperatures. The studies involve the investigation of the morphological structures and electrical and optical properties of doped ZnO. In terms of structural properties, scanning electron microscope images of Sn- and Al-doped ZnO change as the dopant concentration is increased. The doped thin film response and recovery towards 200 ppm of ammonia were observed and recorded. Both dopants show good gas sensing response. The recorded resistance reading suggests that Al is the superior dopant in gas sensing as it produces a low resistance reading of 230 Ω as opposed to 140 kΩ produced by Sn-doped ZnO thin film.
  • Publication
    Characterization of Excimer Laser Micromachining Parameters to Derive Optimal Performance for the Production of Polydimethylsiloxane (PDMS)-based Microfluidic Devices
    ( 2024-01-01)
    Shazlina Johari
    ;
    Ting Z.K.
    ;
    Mazlee Mazalan
    ;
    Yufridin Wahab
    ;
    Anas Mohd Noor
    ;
    Mohd Fairus Ahmad
    ;
    Muhammad Mahyiddin Ramli
    Laser micromachining has been used as an alternative to producing microfluidics structures and simplifying the conventional soft lithography process. In this paper we characterize the excimer laser micromachining parameters and demonstrate its application by producing several microfluidic structures in polydimethylsiloxane (PDMS). The parameters include the number of laser pulses, laser energy and rectangular variable aperture (RVA) in both x- and y-directions. We found that the laser energy and pulse rate affect the depth of micromachining d channels, while RVA in both x- and y-directions affects the width of the channels. Repetition of laser scan does not change the channel width but significantly changes the channel depth. Proper adjustment for laser energy and pulse rate is required to fabricate a desired channels depth. In order to demonstrate the microfabrication capability of an excimer laser with the optimal operating parameters, several microfluidic structures were micromachining d into PDMS with a KrF excimer laser.
      1
  • Publication
    Visible Light-Assisted Charge Extraction in High-Band-Gap SrTiO3 through the Integration of a Triplet Sensitizer-Emitter Thin Film
    ( 2024-01-22)
    Jie K.V.Y.
    ;
    Mohd Fairus Ahmad
    ;
    Mohmad A.R.
    ;
    Ismail A.M.
    ;
    Mohd Natashah Norizan
    ;
    Ramli M.M.
    ;
    Safizan Shaari
    ;
    Sulaiman Y.
    ;
    Shamsul Amir Abdul Rais
    ;
    Shazlina Johari
    A challenge in PV designs, including those with an electron transport layer (ETL), is the presence of ‘parasitic absorbers’. These are layers that absorb light without significantly converting it to electrical current, impacting the total external quantum efficiency (EQE). Strontium titanate (STO), a high-band-gap (3.20 eV) perovskite metal oxide, holds promise as an electron transport layer (ETL) for solar energy harvesting. Despite STO’s potential, it primarily operates in the UV spectrum, not fully utilizing the broader light range, and hence can be the source of parasitic absorbers. In this study, we report a significant enhancement in the EQE of STO through the integration of a triplet sensitizer-emitter (TSE) system, designed to upconvert the visible spectrum into UV light and improve the charge extraction from STO. The TSE system uses carbazolyl dicyanobenzene (4CzIPN) as a sensitizer and p-terphenyl (TP) as an emitter. To investigate the EQE of such a system, we fabricate STO as a PV cell. The revised PV cell architecture (ITO/TiO2/STO/TSE/PEDOT:PSS/Al) is a modification of the conventional configurations (ITO/TiO2/STO/PEDOT:PSS/Al). With the TSE thin film, the modified STO PV cell shows better charge extraction under sunlight compared to the standard STO PV cell, indicating that the upconversion process can enhance the hole conductions from STO to PEDOT:PSS through the TSE system. We noted an EQE increase with intense light of λ > 345 nm in thicker TSE layers and a decrease in the EQE under similar light intensity in thinner TSE layers. The Kelvin probe force measurement (KPFM) data showed that the TSE layer receives holes from STO under illumination. Additionally, time-resolved photoluminescence (TRPL) experiments showed that the TSE/STO thin film is able to produce UV emission after irradiation with lower energy light. Then, the EQE variation in thicker TSE layers under intense irradiation can be attributed to the solid-state upconversion, indicating its thickness-dependent performance. These findings underline the strategies for maximizing the utilization of the solar spectrum in PV applications.
      30  1
  • Publication
    Fabrication of deep green light emitting diode on bulk Gallium Nitride substrate
    (IOP Publishing, 2020)
    Shamsul Amir bin Abdul Rais
    ;
    Zainuriah Hassan
    ;
    Ahmad Shuhaimi bin Abu Bakar
    ;
    Muhammad Nazri bin Abdul Rahman
    ;
    Yusnizam bin Yusuf
    ;
    Muhamad Ikram bin Md Taib
    ;
    Abdullah Fadil bin Sulaiman
    ;
    Hayatun Najiha binti Hussin
    ;
    Mohd Fairus Ahmad
    The indium composition in InxGa1-xN/GaN multi-quantum well structure e(MQW) is crucial because lower indium composition will shift the wavelength towards ultraviolet region. Nevertheless, at certain indium content in MQW, it will out diffuse from the MQW resulting in the wavelength shift from green to much shorter wavelength, after the annealing process for p-type activation. In this study, we had grown a full Light Emitting Diode device with the MQW layer at a relative high temperature for green LED with indium pre-flow at the top of n-type layer just beneath the MQW using Metal Organic Chemical Vapor Deposition (MOCVD). Transmission Electron Microscopy (TEM) image of the MQW prior and post the activation of p-type had been observed, which resulted in good contrast, showing the abruptness of the MQW layer of the device. Homogenous layers of InxGa1-xN/GaN has been observed. We also managed to reduce the wavelength shift of the device significantly. The optical, crystal properties of grown devices had been studied.
      2  1
  • 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.
    ;
    Kar Y.B.
    ;
    Mohd Natashah Norizan
    ;
    Mohd Fairus Ahmad
    ;
    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.
      3  21
  • Publication
    Modification of Photoanode Surface Structure via Image Analysis on Organic Polymer Material based for Dye-Sensitized Solar Cell (DSSC) Applications
    ( 2021-12-01)
    Nur Liyana Mohd Rosli
    ;
    Norhayati Sabani
    ;
    Mohd Fairus Ahmad
    ;
    Mohd. Azarulsani Md. Azidin
    ;
    Nurjuliana Juhari
    ;
    Nor Farhani Zakaria
    ;
    Mohd Natashah Norizan
    ;
    Safizan Shaari
    In this study, the experiment on the modification of the photoanode with organic polymer material as copolymer template for dye-sensitized solar cell (DSSC) applications has been conducted. The two organic copolymer templates are polystyrene sphere (PS) and poly[2-methoxy-5(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). The modification photoanodes were made using Dr. Blade’s method. These organic copolymer templates were added to improve the surface of the mesoporous titanium dioxide (TiO2) layer, which is used as the main component in DSSC photoanode. The unmodified TiO2 photoanode has poor aggregation and porosity of TiO2. The addition of either MEH-PPV or PS sphere to the photoanode layer was found to affect the surface of mesoporous TiO2 in terms of porosity, particle size distribution and shape. The analysis of the TiO2 modification was conducted using an image analysis processing method via a 2D scanning electron microscope (SEM) image. The image analysis processing method used was the ImageJ program. The DSSC of modified photoanode is fabricated using metal complex dye, Ruthenium (N719) dye. The data collected from the ImageJ program showed that by adding organic copolymer templates into TiO2, the porosity of TiO2 decreased from 45 % to 42 %. From the photovoltaic analysis obtained, the J-V characteristic is recorded with the photoanode of TiO2 mixed with 1.00 wt% MEH-PPV gave the highest efficiency, which is 0.01 % with the following parameters – Voc = 0.43 V, Jsc = 0.17 mA/cm2 and FF = 0.20. Meanwhile, the photoanode of TiO2 mixed with 0.50 wt% PS sphere gave the highest efficiency which is 0.08 % with the following parameters – Voc = 0.39 V, Jsc = 0.86 mA/cm2 and FF = 0.25.
      1
  • Publication
    Design of a low-power CMOS operational amplifier with common-mode feedback for pipeline analog-to-digital converter applications
    ( 2017-01-01)
    Sohiful Anuar Zainol Murad
    ;
    Izatul Syafina Ishak
    ;
    Mohd Fairus Ahmad
    ;
    Shaiful Nizam Mohyar
    This paper proposes a design of a low-power operational ampliér (op-amp) for pipeline analog-to-digital converter (ADC) applications using a 0.13-μm CMOS process. The folded-cascode topology with NMOS input types is employed for the op-amp design due to a larger output gain compared to PMOS input types. Furthermore, the op-amp is designed with a double detection structure of a common-mode feedback circuit to provide stable feedback voltage. The simulation results show that the proposed op-amp achieved a gain of 64.5 dB and a unity gain bandwidth of 695.1 MHz with a low power consumption of 0.14 mW. In addition, by applying ±1.2 V of input voltage, the output voltage generated by the proposed op-amp design remains at 1.2 V with a constant feedback voltage of 1.3 V. Moreover, the proposed circuit was implemented and simulated successfully in a 1.5-bit per stage pipeline ADC.
      5  27