Research Output
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PublicationCost effective negative Plenum Cleanroom for Microelectronic Engineering undergraduate( 2005)he Negative Plenum Cleanroom which is design and built by KUKUM is primarily used for the teaching of the undergraduate microelectronic course. The cleanroom is approximately 115m² in size. The level of cleanliness in the cleanroom ranges from ISO Class 5 (Yellow Room) to ISO Class 8 (Grey Area/Utility Chase). The cleanroom is constructed with a negative plenum to house the fan filter units, which make it different from other commercially available cleanrooms. With negative plenum, maintenance work cost will be reduced and make the cleanroom life longer. The main intention of this project is to expose and teach students to appreciate the stringent cleanroom protocols, health and safety requirement in addition to the formal course works.
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PublicationElectrical Properties of GaN Cap Layer for AlGaN/GaN HEMT( 2023-01-01)Metal organic chemical vapor deposition (MOCVD) was used to grow AlGaN/GaN HEMT on a sapphire substrate with a 3.0 nm GaN cap and a sample without a GaN cap. High resolution Xray diffraction (HRXRD) was utilized to investigate the structural characteristics of the materials. The relationship between the electrical properties and two-dimensional electron gas (2DEG) I-V and Hall Effect measurement. The I-V measurement was used to investigate the resistance properties of AlGaN/GaN heterostructures. Hall Effect measurement was used to quantify electron mobility and sheet carrier concentration in both samples. The sample with a 3.0 nm GaN cap exhibited excellent electrical properties with 436.8 Ω/sq sheet resistivity and possessed a high value of sheet carrier concentration 3.46E+14 per cm2.
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PublicationTop-Down Fabrication of Silicon Nanogap for Detection of Dengue Virus (DENV)( 2020-01-01)In this work, a highly sensitive Silicon nanogap biosensor was demonstrated for Deoxyribonucleic acid (DNA) detection related to Dengue virus (DENV). The Silicon nanogap was fabricated using the top–down conventional lithography approach followed by reactive ion etching (RIE) to further thin down the nanogap. The inspections of Silicon nanogap structures were carried out using the scanning electron microscope (SEM) and atomic force microscopy (AFM). The surface of the fabricated Silicon nanogap was functionalized by means of a three-steps procedure involving surface modification, immobilization and hybridization. This procedure acts as a liquid gate control to establish the electrical detection targets of the dengue virus. The electrical detection is based on the changes in the current of the sensor due to the accumulation of the negative charges by the immobilized probe and hybridized target Deoxyribonucleic acid. The limit of detection (LOD) achieved was recorded at 10 pM with a 207 nm of fabricated Silicon nanogap and its sensitivity at 1.5 × 10−10 AM−1. The demonstrated results show that the Silicon nanogap has the excellent properties for detection of dengue virus as biosensor devices.
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PublicationFabrication and Characterizations of Poly-Si Nanowire Biosensor using Conventional Photolithography Technique for Detection of Dengue Virus DNA Type 2 (DENV-2)( 2020-07-09)Nowadays, nanotechnology has become a vast expanding application which can be used all across the science field such as chemistry, biology, physic, material science and engineering. In this paper, a poly-Si nanowire biosensor was fabricated by using the conventional photolithography technique. In addition, this technique is used to define the initial poly-Si with the dimension of 1 μm. After the conventional photolithography process, the photoresist undergone the development using resist developer and etched with reactive ion etching (RIE). Meanwhile, for the electrical part, it was observable that there was an increase in current when the nanowire has been hybridized with Dengue DNA type-2 (DENV-2) ranging from 10 fM - 10 μM. The morphology of the poly-Si nanowire was characterized by optical microscopy whilst electrically characterized by measuring the two-terminal current-voltage (I-V) characteristic.
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PublicationFaradaic electrochemical impedimetric analysis on MoS2 /Au-NPs decorated surface for C-reactive protein detection( 2022-09-01)Background: A label-free Faradaic electrochemical impedimetric was developed for a highly sensitive detection of C-reactive protein using a gold interdigitated microelectrode bio-sensing platform enhanced by a gold nanoparticle-decorated molybdenum disulfide (Au-NPs/MoS2) nanosheet via selected chemical linking processes. C-reactive protein (C-RP), a crystalline protein, generates by the liver and hikes when there is inflammation throughout the patients’ body. The concentrations of C-RP plasma levels tend to increase rapidly when the patient facing major injury which will lead to cardiovascular disease (CVD). Methods: The 5 µm microelectrode and gap size g-IDE with the nanostructured materials was demonstrated to increase the impedimetric detection response in Faradaic-mode electrochemical impedance spectroscopy high performance detection environment. The high surface area-to-volume ratio of the modified Au-NPs/MoS2 nanocomposite increased the probes loading onto the transducer and enhanced the impedimetric detection response of the C-RP target post-binding due to an amplified net change in the charge transfer resistance. The developed immunoassay revealed a linear detection of C-RP biomarker in a logarithmic-scale from as low as 1 fg/mL up to 1 µg/mL, and a limit of detection of 0.01 fg/mL. The sensor shows great potential as an early warning risk for cardiovascular disease at a threshold concentration value of C-RP at 1 µg/mL. Significant findings: The biosensor demonstrates an excellent discrimination against other competing proteins in serum, exhibiting the highest predilection to C-RP spiked human serum target. The sensor's reproducibility is reported within an acceptable range of relative standard deviation of 1–4% for n = 3.
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PublicationField-Effect Transistor-based Biosensor Optimization: Single Versus Array Silicon Nanowires Configuration( 2020-01-01)This paper demonstrated the effect of different number of silicon nanowire transducer channels, in other word single, double, and triple channels towards the performance of field-effect transistor-based biosensor through simulation tool. These silicon nanowire field-effect transistor biosensors were designed and simulated in device simulation modelling tool, Silvaco ATLAS with fixed length, width, and height of the silicon nanowire. Different negatively interface charge density values were applied on the transducer channels’ surface of the biosensors to represent as detected target biomolecules that will bind onto the surface of the transducer regions. Based on the results, more negatively interface charges density values presented on the sensing channels had reduced the electron carrier accumulation at the channel’s interface, therefore, reduced drain current flow between the source and drain terminal. With the increase number of the transducer channels, significant change in drain current for every applied negatively interface charges became more apparent and increased the sensitivity of the biosensor. The triple transducer channels silicon nanowire field-effect transistor biosensor had demonstrated highest sensitivity, that is 2.83 µA/e∙cm2, which indicates it has better response for the detection of interface charges, thus increases chances for transducer channels reaction to the target biomolecules during testing or diagnosis.
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PublicationNanomanipulation of Functionalized Gold Nanoparticles on GaN( 2023-01-01)Gold nanoparticles (AuNPs) are known for their high surface area to volume ratio, which acts as an excellent receptor when placed in between electrodes in sensor applications. Microelectrodes with bar and needle-shaped pointed ends in two configurations, comb and castle wall, were designed to be used for the fabrication of electrodes to observe the relation between the geometry of electrodes and the dielectrophoretic behaviour of AuNPs on p-gallium nitride (p-GaN) substrates. The electrical properties were analyzed before and after the drop cast of AuNPs using current-voltage (I-V) curve method with manual probing. Resistance values of each sample were calculated under reverse bias condition. The effect of the design configurations of the electrodes on the nanomanipulation of AuNPs will be discussed.
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PublicationMolybdenum disulfide—gold nanoparticle nanocomposite in field-effect transistor back-gate for enhanced C-reactive protein detection( 2020-11-01)Nanofabricated gold nanoparticles (Au-NPs) on MoS2 nanosheets (Au-NPs/MoS2) in back-gated field-effect transistor (BG-FET) are presented, which acts as an efficient semiconductor device for detecting a low concentration of C-reactive protein (C-RP). The decorated nanomaterials lead to an enhanced electron conduction layer on a 100-μm-sized transducing channel. The sensing surface was characterized by Raman spectroscopy, ultraviolet–visible spectroscopy (UV-Vis), atomic force microscopy (AFM), scanning electron microscopy (SEM), and high-power microscopy (HPM). The BG-FET device exhibits an excellent limit of detection of 8.38 fg/mL and a sensitivity of 176 nA/g·mL−1. The current study with Au-NPs/MoS2 BG-FET displays a new potential biosensing technology; especially for integration into complementary metal oxide (CMOS) technology for hand-held future device application. [Figure not available: see fulltext.]
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PublicationSilicon nanowire biosensors for diabetes mellitus monitoring( 2024-10)The main goal of this research is the development of a label-free biosensor for the detection of diabetes mellitus (DM) using the target molecule retinol-binding protein 4 (RBP4). The enzyme-linked immunosorbent assay (ELISA) approach, currently used to detect DM, is time-consuming and difficult. As a result, label-free biosensors are being considered as an alternative. In this research, silicon nanowires (SiNWs) were selected as the transducer for this biosensor due to their low cost, real-time analysis capability, high sensitivity, and low detection limit. The SiNWs were created using conventional lithography, reactive ion etching (RIE), and physical vapor deposition (PVD), and then dripped with a gold nanoparticle solution to create gold-decorated SiNWs. The surface of the gold-decorated SiNWs was functionalized using 3-aminothiophenol and glutaraldehyde solutions before being immobilized with DM RBP4 antibodies and targets. The electrical characterization of the gold nanoparticle decorated SiNWs biosensor revealed good performance in DM detection. The pH tests confirmed that the SiNWs acted as a transducer, with current proportional to the DM RBP4 concentration. The estimated limit of detection (LOD) and sensitivity for detecting DM RBP4 binding were 0.076 fg/mL and 8.92 nA(g/mL)-1, respectively. This gold nanoparticle decorated SiNWs biosensor performed better than other methods and enabled efficient, accurate, and direct detection of DM. The SiNWs could be used as a distinctive electrical protein biosensor for biological diagnostic purposes. In conclusion, gold nanoparticle deposition offers effective label-free, direct, and high-accuracy DM detection, outperforming previous approaches. Thus, these SiNWs serve as novel electrical protein biosensors for future biological diagnostic applications.
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PublicationNumerical Simulation on the Impact of Back Gate Voltage in Thin Body and Thin Buried Oxide of Silicon on Insulator (SOI) MOSFETs( 2023-10-01)Silicon-on-Insulator (SOI) technology provides a solution for controlling Short-Channel Effects (SCEs) and enhancing the performance of Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs). However, scaling down SOI MOSFETs to a nanometer scale does not necessarily yield further scaling benefits. Introducing multiple gates, such as a double gate configuration, can effectively mitigate SCEs. Nonetheless, fabricating a flawless double gate structure is an exceedingly challenging endeavor that remains unrealized. The adoption of a back gate bias, with an asymmetrical thickness arrangement between the front and back gates, mimicking the behavior of a double gate, offers an alternative approach. This approach has the potential to modify the electrical characteristics of the device, thus potentially leading to improved control over SCEs. In this study, we employed 2D simulations using Atlas to investigate the influence of back gate biases, namely,-2.0 V, 0 V, and 2.0 V on a 10 nm silicon thickness at the top and a 20 nm buried oxide thickness for n-channel MOSFETs. We focused on key parameters, including threshold voltage (VTh), Drain Induced Barrier Lowering (DIBL), and Subthreshold Swing (SS). The results demonstrate that a negative back gate bias is the most favorable configuration, as it yields superior performance. This translates into more effectively controlled SCEs across all the parameters of interest.