Theses & Dissertations

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https://hdl.handle.net/20.500.14170/2003

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  • Publication
    Development of nanoparticle sensors for the detection and quantification of swine DNA in mixed biological and commercial samples for halal authentication
    ( 2011)
    Md. Eaqub Ali
    Verification of declared components in meats and meat products is essential to ensure transparency in food labeling and to safeguard consumers’ trusts, religious faiths, health, and hard earned fortunes. The annual turnover of the global Halal food market has reached USD 661billion in 2011 and will be proliferating in the coming years. To coup up in highly competitive market and to make an excessive profit, fraudulent labeling of Halal brand is frequently occurring. As pork and pork-derivatives are easily available at cheaper prices, replacement of higher priced Halal meats in commercial meat products with lower valued pork has become quite prevalent. However, the mixing of pork and pork-derived materials in the Halal and Kosher foods is a serious matter as they are not allowed to be consumed by the followers of Islam and Judaism by respective religious laws. Thus, sensitive, dependable, and easy performable analytical tools have long been desired to detect and quantify the minute level of adulterated pork in Halal and Kosher foods. Conventional methods based on polymerase chain reaction (PCR)-based DNA analysis has reached a ceiling stage and has limitations in detecting shorter-length DNA markers which are proven to be survived in the harsh conditions of food processing. Further, PCR-based methods are not only expensive but also needs product authentication to eliminate ambiguity in certain instances. DNA detection using gold nanoparticles (GNPs) is very promising because it does not need any complex and expensive instrumentations and allows rapid and reliable detection of very short-length (15-30 bp) DNA sequences. In this report, we have developed two types of GNP-based sensors. The first one is the colorimetric sensor that allowed visual detection of PCR amplified and non-amplified swine DNA markers (27 and 25 nucleotides) within 10 min without any instrumental aids in a mixed background of processed and unprocessed meat products. It also permitted the verification of the visually determined results by the distinct features of the absorption spectra of the aggregated and non-aggregated GNPs. The detection limit (DL) of this method varied between 4-6 ng μL-1 of porcine genomic DNA. The second one was the hybrid nanobioprobe that covalently integrated a fluorophore labeled 27-nucleotide AluI-fragment of swine mitochondrial cytochrome b (mt-cytb) gene. It allowed simultaneous detection and quantification of porcine muticopy mt-DNA targets within 60 min with the help of a cost-effective fluorescent spectroscopy. The DL of this method was 0.42 ng μL-1 of contaminated pork in severely autoclaved pork-beef binary mixture in which longer-size PCR template were broken down to smaller fragments leading to detection failure by the PCR- methodology. The shorter-lengths DNA markers (15-30 bp) suitable for biosensor application were developed by in-silico digestion of swine mt-genome with AluI restriction enzymes. Prior to biosensor applications, the swine specificity of the developed mt-DNA markers was tested by developing a very short (109 bp) PCR-restriction fragment length polymorphism (RFLP) assay as well as a TaqMan probe quantitative real-time PCR (qPCR) assay containing appropriate AluI-sites within the amplicon. Both the PCR-RFLP and qPCR assays were effective to detect as low as 0.0001 ng of pure swine-genomic DNA and 0.001 ng of pork contamination in readyto- eat commercial meat products.
      5  18
  • Publication
    Fabrication and characterization of silicon and polysilicon nanogaps electrodes using size reduction technique for chemical and biomolecules detection
    ( 2012)
    Thakra. S. Dhahi
    Nanogap electrodes may be defined as a pair of electrodes separated by nano-scale spacing. Two important studies enabled the non-scientists to envision the development of nanogap-based electrical and electronic sensors and devices for the ultrasensitive detection of DNA. In the first study DNA can transport charges and can bridge the electrodes separated by a nanoscale gap whereas for second study, charge transport is interrupted when the molecule undergo denaturation from double-stranded to single-stranded conformation. The aim of this research work is to design, fabricate, characterize, and test nanogap-electrode based device for biochemical detection and DNA immobilization and hybridization detection. However, the focus of this research is to investigate electrically and chemically the effect of different materials and gap sizes on the nanogap electrodes design. Fabrication and characterization of less than 10 nm gap for both silicon and polysilicon nanogap electrodes structures being the main target in this research. Two masks were designed for the fabrication of nanogap and electrodes pad on silicon (Si) and silicon-on-insulator (SOI) wafers as a starting substrate to fabricate polysilicon and silicon nanogap devices respectively. Nanogap electrodes devices were fabricated using a size reduction technique which involves sequential and repeated thermal oxidation and wet etching processes. A thick layer of silicon and polysilicon materials were used to provide device stability throughout the fabrication process. The surface morphology of the fabricated nanogap structure was characterized using SEM and FESEM. The observed results showed the gap size of a 6-nm and 5-nm for silicon and polysilicon electrodes structure respectively. Gold pad electrodes were then fabricated on the silicon and polysilicon nanogap structures to increase the electrical conductivity and permittivity of the devices especially during bio-molecules detection. Capacitance, permittivity and conductivity are measured electrically to characterize the fabricated nanogap structures using a dielectric analyzer. However, sourcemeter equipment was first used to measure the current and characterize the resistivity of the nanogap structures as a function of applied voltage. It was found that the resistivity decreases with the reduction in gap sizes to aid the passage of current flow between the electrodes. Furthermore, the devices were chemically tested for the measurement of pH and yeast concentrations. It was found that the capacitance, permittivity and conductivity increased with pH and decreased with yeast concentrations. Finally, the devices were used as a DNA sensor for nucleic acid hybridization detection which is a key step in molecular diagnostics, gene profiling and environmental monitoring. Amine functionalized group from APTES were used to modify the silicon and polysilicon electrodes surface. Amine- groups (NH2) were labeled with gold nanoparticles to tag a thiol-modified DNA probe onto the nanogap surfaces. The developed biosensors clearly differentiated complementary, noncomplementary and single mismatched DNA targets through the measurements of capacitance, conductance and permittivity. The detection limit of the sensors was 5 nmol/L of target DNA. As a conclusion, this research successfully demonstrated the process to design, fabricate, characterize and test nanogap based biosensor using size reduction technique for DNA hybridization detection.
      2  11
  • Publication
    Design and fabrication of SWNT-FET based biosensor
    ( 2012)
    Mohd Syamsul Nasyriq Samsol Baharin
    Nanotubes have generated intense research activities from scientists of various disciplines because they represent a new class of materials for the study of one-dimensional physics. Single-walled carbon nanotubes (SWNTs) have many other magnificent properties and it has impressive properties in three aspects, mechanical, electrical, and biological due to ability of single-walled carbon nanotubes (SWNTs) to exhibit self-assemble monolayer (SAM0. The main objective of this project is to design and fabricate carbon nanotube based biosendor for future application medical diagnostics. The electrical transport of semiconducting single-walled carbon nanotubes with the diameter of ~1.5 nm and length of 2 μm to 6 μm for its applications as biomolecules detection was investigated. Single-walled carbon nanotubes field effect transistors (SWNT-FET) were fabricated in house using three masks designed. Initially backgated field effect transistor (FET) was formed and followed with the growth of oxide as insulation layer. Multilayer metal of platinum,Pt and gold,Au were grown on top of oxide layer and finalized with the integration of single-walled carbon nanotubes (SWNTs). The oxide thickness achieved is ~18nm and multilayer metal of platinum,Pt and gold,Au thickness is ~10nm and ~90nm respectively. The integration of single-walled carbon nanotubes (SWNTs) with field effect transistor (FET) was performed using AC dielectrophoresis nanomanipulation technique resulting promising results of integration proven via Scanning Electron Microscope (SEM). Fabricated device resulting conductance of G ~ 0.03 x 4e2/h and hole mobility of μp ~ 3060 cm2/V.s in saturation mode. This device also shows resemblances with conventional p-type metal-oxide-semiconductor FETs (MOSFETs) through IDS-VDS curve and appears to be gate voltage dependence through conductance-gate voltage curve. Thus, these results prove that fabricated device functioned as p-type metal-oxide-semiconductor FETs (MOSFETs) and can be used for the application of biomolecules detection such as protein by monitoring the device changes of IDS-VDS characteristics.
      2  36
  • Publication
    Portable electronic embedded system ISFET based pH meter test kit for harumanis ripeness detection
    ( 2012)
    Muhammad Naim Haron
    Measurement of pH in terms of Ionic Sensitive Field Effect Transistor (ISFET) and integration with the electronic embedded system is essential in agriculture processes especially in fruit ripeness monitoring, pH data analysis and fruit ripeness control applications. This research project is an alternative for determining the states of ripeness or maturity for harumanis using ISFET technology. The idea for implementing this research is based on the concept of determination of pH for harumanis by using conventional glass pH meter test kit. The kit shows that a sample of harumanis stores ions sensitive signal in terms of electrical signal. Therefore, the pH meter indicates that the harumanis has analog value and the embedded system converts this analog value to be displayed as digital value on the LCD display. As it turns out, there is a correlation between these pH properties and the maturity of harumanis. The pH of different types of harumanis maturity has been measured using pH meter test kit which is connected to an embedded system. This pH meter setup consists of ISFET pH sensor with a reference electrode for calibrating different types of harumanis sample. The ISFET pH sensor has shown that detection of different types of maturity levels for harumanis is feasible hence the sets of pH reading obtained are observed on LCD display. The sets of pH reading are analyzed in identifying time duration for harumanis maturity. Therefore a graph of pH for harumanis against duration of harumanis maturity can be produced, thus the process of harvesting harumanis is easier than as expected. ISFET provides a method to view the analog input from the impedance provided by the oscillator circuit. For digital display purpose, the data acquisition is sent to a personal computer via serial link. It displays digital pH meter by processing the digital output signal. Since the ISFET sensor has proved to give accurate and reliable measurements of the pH properties for harumanis, it is chosen as the standard measurement device in determining harumanis maturity level; under ripe, ripe or over ripe.
      4  45
  • Publication
    Fabrication and characterization of ZnO nanostructures for DNA detection
    ( 2013)
    Foo Kai Loong
    Zinc oxide (ZnO), a representative of group II-IV metal-oxide semiconductor material is widely studied in the current research community. ZnO with its wide direct band-gap (3.37eV) and high exciton binding energy (60meV) providing the advantages of their electrical and optical properties. Due to these unique properties and easiness to grow using bottom-up approach combines with high isoelectric point, toxic-free, high surface-area-to-volume ratio, biosafe, and biocompatible, ZnO nanostructures have great interest in the application of biosensor. The aim of this research work is to synthesis, fabricate, and characterize ZnO nanostructures based sensor for DNA immobilization and hybridization detection. Two types of ZnO nanostructures were studied, namely thin films and nanorods (NRs). Highly transparent ZnO thin films were successfully synthesized using ease and low-cost sol-gel spin-coating method. ZnO NRs with nanoscale possessed high crystalline structure was further grown from the asprepared thin films through low-temperature hydrothermal growth. In this thesis, we studied the influence of different solvents on the structure, optical and electrical properties of the ZnO nanostructures. Four types of solvents namely methanol, ethanol, isopropanol, and 2-methoxyethanol had been chosen for ZnO seed solution preparation. The observed results using FESEM indicated that the nanoparticles and nanorods with the size less than 40 nanometer and 60 nanometer, respectively were successfully synthesized. The investigation on optical properties using UV-Vis-NIR spectrophotometer confirmed ZnO is classified as a wide band gap semiconductor material. In order to fabricate a biosensor with high sensitivity and selectivity, a gold nanoparticles (GNPs) were selected for the surface modification of ZnO nanostructures which later formed gold-thiolate conjugation with thiol-modified ssDNA probes. Two approaches were used for the immobilization and hybridization of DNA detection, which were dielectric analysis and electrochemical analysis. DNA detection using dielectric analyzer was done on interdigitated electrodes gold modified ZnO thin films. The developed sensor clearly differentiated complementary and non-complementary of target DNA through the measurement of capacitance, permittivity, and impedance. DNA detection using electrochemical analysis with cyclic voltammetry confirmed surface ZnO NRs modified with (3-Aminopropyl)triethoxysilane (APTES) and gold nanoparticles provided better detection of target DNA in comparison with those only contained gold nanoparticles.
      9  4
  • Publication
    Design and fabrication of n-ISFET using Si₃N₄/SiO₂ structure for pH measurement
    ( 2013)
    Nur Syuhada Md. Desa
    The design and fabrication of n-ISFET using Si₃N₄/SiO₂ structure for pH measurement has been carried out. In general Ion Sensitive Field Effect Transistor (ISFET) is a potentiometric pH sensor which widely used in chemical, biochemical and biomedical applications due to its advantages such as small size, low power consumption, robustness, and fast response time over the ion-selective electrode (ISE). In this study, the ISFET was designed and fabricated in-house in Micro Fabrication Cleanroom Laboratory using a standard Complementary Metal Oxide Semiconductor (CMOS) processes fabrication except the gate area was replaced by reference electrode, sensing membrane and electrolyte under test. The main objective of this study is to present a concept, the design, fabrication and testing appropriate to process flow in fabricating the n-ISFFET on silicon wafer, which will finally be characterized using a suitable test methodology. Hence, fabrication on p- type <100> 4 inch silicon wafer by photolithography, wet chemical etching, thermal oxidation, diffusion and metallization with focus on a pH measurement has been executed.The n-ISFET was operated when the surface absorption of the charges in the electrolyte under test simultaneously interact with both reference electrode and surface sensing membrane. Overall process has 5 mask levels consist of source mask and drains mask, gate mask, contact mask and metallization mask. The fifth mask was used to find the best thickness of silicon nitride for sensing membrane layer and 50 nm was selected. For sensing material, SiO2 insulator layer was used and later deposited on top with Si3N4 insulator layer by Plasma Enhanced Chemical Vapor Deposition (PECVD). The latter layer serves as a pH sensitive membrane. The electrical tests were performed using buffer solutions with varying pH values, indicated that the transistor can be employed to measure the pH of solutions at room temperature. The interaction between these methods will modulate a threshold voltage and simultaneously will extracted the output (IdVd) and transfer (IdVg) characteristic curves at three differences channel length; 250μm, 300 μm and 500 μm respectively.The best pH sensitivity achieved at the channel length 500 μm with the measurement value equal to 54.43 milivolt per pH (mV/pH).
      4  37
  • Publication
    Synthesis of ZnO nanostructures for gas sensing applications
    ( 2013)
    Muhammad Kashif
    Research on nanotechnology has become increasingly popular because of their unique physical, chemical, optical and catalytic properties compared to their bulk counterparts. Nanotechnology revolutionize many technology and industry sectors such as energy, food safety, environmental sciences, medical sciences and medical instrumentation, homeland security, and many others. Among II-VI semiconductor materials, ZnO is a unique and distinguish material with wide band-gap (3.37 eV) and the large exciton binding energy (60 meV) at room temperature. ZnO nanostructures have attracted great attention among the researchers due to its peculiar properties such as high electron mobility, high thermal conductivity, good transparency, and easiness to fabricate different type of nanostructures. The objective of this research is to synthesize different ZnO nanostructures using low-cost sol-gel spin coating method for gas sensing applications. A thin seed layer of ZnO was deposited to provide the nucleation sites for the growth of ZnO nanostructures. The surface morphology, structural, optical and electrical properties of the synthesized ZnO nanostructures was characterized using SEM, XRD, PL, Raman, XPS and sourcemeter. Gold and silver interdigitated electrodes were thermally evaporated on the surface of ZnO nanostructures using stainless steel shadow mask. The current research successfully demonstrated the application of sol-gel method to synthesize different nanostructures. Moreover, the fabricated ZnO based nano-sensors have also been applied for gas sensing applications. In this thesis, we have studied the effect of precursor molar concentrations (0.0125- 0.075 M) on the morphology of ZnO nanostructures. It was observed that the ZnO nanorods tend to grow along with the ZnO nanoflakes and the density of ZnO nanorods increases as the molar concentrations increased from 0.05 M to 0.075 M. The PL and Raman spectra also redshifted and the redshifting were attributed due to local heating. The effect of different solvent for the seed solution preparation was also studied. It was observed that different seed solution greatly affects the growth direction of ZnO nanorods as well the conductivity of the device. The detailed study was conducted to investigate the effect of UV exposure time on the device current stability and it was observed that after 60 min of UV exposure a stable current flow was observed. Thedetermination of stable current after UV exposure is important for UV-based gas sensing and optoelectronic applications. Finally, we fabricated the Pd-doped ZnO nanorods, and pure ZnO nanorods for gas sensing applications. The fabricated sensors were successfully tested for a wide range of hydrogen and acetone concentrations 40-360 ppm, and 0.05- 457 ppm, respectively. It was observed that the sensor was at least 25 fold more sensitive over the literature documented Pd-doped ZnO nanorods in detecting hydrogen at room ambient temperature. The fabricated sensor displayed the decrement in grain boundary resistance from 11.95 to 3.765 KΩ when the hydrogen concentration was increased from 40 to 360 ppm. The acetone sensor based on ZnO nanorods exhibited excellent acetone sensing over a wide range of acetone concentrations (0.05- 457 ppm). The sensor exhibited the response and recovery times of 8 s and 428 s, respectively, for 183 ppm of acetone. The sensor also displayed good repeatability under the exposure of 183 ppm of acetone
      4  14
  • Publication
    Development and fabrication of carbon nanotube (CNT) based pH sensor
    ( 2013)
    Low Foo Wah
    The development, fabrication and characterization of single-walled carbon nanotubes (SWCNTs) based pH sensor using aligned SWCNT were reported. The SWCNT alignment is defined by a single carbon nanotube aligned between the fabricated electrodes. This research involves the study of SWCNTs dispersion, alignment of SWCNT between microgap electrodes and characterization on the effect of change in the pH level on the impedance, conductance and capacitance of the aligned SWCNT. In the SWCNT dispersion study, the SWCNTs were dispersed in Isopropyl Alcohol (IPA), Dichloromethane (DCM), Acetone and Triton-X 100. It was found that SWCNT disperse best in the IPA solution because the dispersed SWCNTs have remained dispersed which can be observed from the clear solution even after 14 days as compared to DCM, acetone and Triton-X 100. On the other hand, the SWCNTs in DCM, acetone and Triton-X 100 have shown a thick mass of coagulated SWCNT after 14 days of dispersion. A chrome mask which consists of 6 groups with different gap measurement was designed. Each group has 5 different designs to facilitate the SWCNT alignment. After that, the devices were fabricated using gold material as electrode to increase the electrical conductivity and permittivity of the device. The SWCNT was then aligned on the fabricated devices using AC dielectrophoresis method. The AC dielectrophoresis method involved control in the voltage and frequency to increase the chance of SWCNT alignment between the microgap. The devices were brought to electrical characterization before and after SWCNT alignment to compare the effect on the device capacitance. It was found that the capacitance before SWCNT alignment is higher than after SWCNT alignment of the device. Before SWCNT alignment, the dielectric of the capacitive device is air which is a better insulator than SWCNT that is a semiconductor material. This phenomenon is due to the fact that dielectric decrease electric field and capacitance is inversely proportional to electric field. On the other hand, the device was tested for its impedance using pH buffer solutions. As pH value was decreased, impedance has also decreased. The hydrogen ions were found to bind to the carboxyl group of the SWCNT creating positive holes in the SWCNT hence increasing its conductivity. As a conclusion, this research successfully demonstrated the process to design, fabricate and characterize the SWCNT based sensor.
      30  3
  • Publication
    Development and fabrication of Ion-sensitive Field Effect Transistor (ISFET) for pH detection, DNA immobilization and hybridization
    ( 2013)
    Chong Soon Weng
    The fabrication of ion sensitive field-effect transistor (ISFET) using silicon nitride (Si3N4) as the sensing membrane is reported. The operation of ISFET is based on the surface charge adsorption of the membrane-solution interface. This thesis describes the design, fabrication and characterization of ISFET for pH detection, DNA immobilization and hybridization. Four photomasks were utilized in the fabrication process to create the ISFET device. The fabricated ISFET device was first brought to morphological characterization before proceeding with the electrical characterization. For the analysis of ISFET in test solution, the Ag/AgCl electrode was used as the reference electrode immersed in different values pH buffer. The results were generated by LabTracer 2.0 measurement system which shows that IV characteristic of ISFET devices gives linear response. The acidic pH buffers contains H+ ions which attract more electron into the conduction channel lowering the channel resistance giving higher value of current flow. While the alkaline pH buffers contains OH- ions which pushed away the electrons from the conduction channel generating more positive holes increasing the channel resistance, thus giving a lower value of current flow. When tested with phosphate buffer solution (PBS), the curves show a decreasing trend of drain current with decreasing concentration of the PBS. It was found that the device has a sensitivity of 43.13 mV/pH. The ISFET device has undergo DNA processes after the electrical characterization with pH and PBS. The DNA immobilization and hybridization processes were detected through a drop in the drain current of the device. Prior to DNA immobilization, the silicon nitride surface was chemically modified to enable the ISFET sensing membrane for DNA probes coupling. It was also observed that with decreasing concentration of DNA complimentary targets in the hybridization process has contributed to the decreasing drain current detected. As a conclusion, the silicon nitride ISFET is a flexible device which can be used to detect pH as well as to perform DNA immobilization and hybridization.
      4  20
  • Publication
    Synthesis and characterization of ZnO nanostructures for ultraviolet (UV) light sensing application
    ( 2014)
    Qazi Muhammad Humayun
    Nanotechnology has strong influence over many known technologies with plenty of advantages, such as low-cost and larger surface-area-to-volume ratio compared with their bulk counterpart. Among II-IV semiconductor materials zinc oxide (ZnO) is an ntype semiconductor with band gap energy of 3.37 eV and having large exciton binding energy of ~ 60 meV. ZnO and its alloys have vast device applications mainly in manufacturing of light emitting diodes (LEDs), solar cells, optical waveguides and Ultraviolet (UV) photodetectors. Ultraviolet (UV) photodetectors are widely used in various commercial and military applications, especially to secure space-to-space communications, pollution monitoring, water sterilization, flame sensing, and early missile plume detection. In contrast to gallium nitride (GaN), ZnO has a highest electron saturation velocity thus, photodetectors equipped with ZnO can perform at a maximum operation speed. The objective of research is to deposit ZnO thin film and ZnO nanorods by sol-gel method at selective area of microgap electrodes spacing and characterization for ultraviolet (UV) sensing application. Therefore the Zerogap structure of butterfly topology was designed by AutoCAD software, and to achieve the better resolution during photo masking process the design was transferred to commercial chrome glass photomask. All the area selective deposited ZnO based nanosensors were further tested for ultraviolet (UV) sensing application. On exposure of ultraviolet (UV) light the current gains, response/recovery times, repeatability, sensitivity, reproductivity and responsivity of the fabricated ZnO based microgap electrodes sensors displayed the promising application for UV light detection. Moreover the signal detection at low operating voltage (1 V) revealed that fabricated sensors can be used for miniaturized devices with low power consumption. The surface morphologies structural, optical and electrical properties of the synthesized nanostructures ZnO were characterized using SEM, XRD, and sourcemeter respectively. To study the doping effect on ZnO nanostructures finally, tin (Sn) was selected, and successfully synthesized on glass substrate by low temperature sol-gel hydrothermal growth process. The as synthesized Sn-doped ZnO nanorods were post annealed at three different temperatures and investigated the effect of post-annealing temperatures on structural, optical, electrical and photoresponse properties by using Xray diffraction, UV-Vis spectroscopy, I-V and i-t measurements. The crystallinity and c-axis orientation of Sn-doped ZnO nanorods were increased with annealing temperatures. As post-annealing temperature increased the Sn-doped ZnO nanorods showed noticeable variations having agglomerated and spherical shape at surface morphology than those at a lower post-annealing temperature; this result indicates that the samples are highly crystalline in nature. The optical bandgap energy of Sn-doped ZnO nanorods decreased as annealing temperature increases. Electrical characteristics reveal the effect of annealing temperature on resistivity and photoresponse properties of Sn-doped ZnO nanorods. Hence, the proposed Herve and Vandamme model and the improved ultraviolet (UV) photoresponse of post-annealed samples are applicable in optoelectronic device applications.
      12  3
  • Publication
    Characrerization, analysis and optical studies of cadmium sulfide nanostructures deposited on different substrates for optoelectroninc applications
    ( 2014)
    Abdul Wahab Salem Z. Lahewil
    Recently the research on nanotechnology has become increasingly popular due to their unique physical, chemical, optical and catalytic properties compared to their bulk counterparts. Nanotechnology revolutionizes many technology and industry sectors such as energy, environmental science, safety, medical sciences, medical instrumentation and many others. An II-VI semiconductor material, CdS nanostructure with a band gap of about 2.45 eV, has attracted great attention among the researches due to the peculiar properties. The objective of this research is to synthesize CdS nanostructure thin films deposited on different type of substrates glass, quartz, n-type and p-type silicon using sol-gel spin coating technique for optoelectronic applications. The CdS nanostructure thin films was synthesized and characterized using XRD, AFM, SEM, UV-VIS, PL, FTIR, TGA, DTA, DSC and Keithley 2400 Source Meter. Silver electrodes were thermally evaporated on the surface of CdS nanostructure thin films using stainless steel shadow mask. For CdS nanostructure thin films deposited on glass substrates, the results have indicated that the CdS has hexagonal structure. The thickness of CdS nanostructure thin films as measured by AFM is found to be in the range of 150 nm and 10 nm at 1000 rpm and 5000 rpm spin coating speeds respectively. For CdS nanostructure thin films deposited onto quartz substrates and annealed at 800 ºC with different spin coating speeds 1000, 3000 and 5000 rpm, the structural, morphological and analytical studies were investigated and found that the grain size of CdS nanostructure thin films found to be in the range 1.81 nm to 4.35 nm. The band gap was measured with an indication of transmission within the visible range. It is found that the band gap changed due to small grain size of CdS nanostructure thin films. The morphology of CdS nanostructure thin films are found to be continuous, dense and well adhered. The films surface is much smoother and the particles are well distributed. For CdS nanostructure thin films deposited into n-type and p-type silicon substrates at different annealing temperatures in the range from 200 oC to 600 oC. The effects of annealing temperatures were investigated on the structural, morphological, optical and electrical properties to improve the CdS nanostructure thin films. The XRD analysis shows that the crystalline quality of CdS nanostructures can be improved by increasing the temperature to 400 oC, but further increase to 600 oC leads to degradation of the crystalline quality. The bulk modulus was calculated and showed good agreement with experimental and theoretical results for different substrates to be found in the range 27.6 to 281.3 GPa. The optical properties of absorption namely; reflection, transmission, extinction coefficient and the energy band gap were obtained by PL and UV-VIS spectroscopies. The calculated refractive index and optical dielectric constant, the results are in agreement with experimental data. The best results for CdS nanostructure thin films are found using p-type silicon substrates annealed at 400 oC. The thermal properties of CdS nanostructures also investigated and found to be evident that a good thermal treatment can largely decrease the film strain and improve its crystallinity.
      2  13
  • Publication
    Wearout reliability studies of bonding wires used in nano electronic device packaging
    ( 2014)
    Gan Chong Leong
    Conventional bare Cu bonding wires, in general, are more susceptible to moisture corrosion compared to gold (Au) and Cu wires. There is very limited knowledge based reliability studies which have been carried out on 1st level interconnect (ball bond in this matter) on nano device semiconductor packages. The objective of this project is to evaluate the wearout reliability, apparent activation energy and Intermetallic compound (IMC) thickness growth of Au, Pd-coated Cu wire and Pd-doped Cu wire used in semiconductor packaging. Methodology of this work include investigation on the effects of bonding wires on wearout reliability of flash component, characterization of the apparent activation energy of IMC and HTSL test and formulation of the failure mechanisms in different wires. Wearout reliability of biased Highly Accelerated Temperature and Humidity Stress (HAST), unbiased HAST (UHAST), Temperature Cycling (TC) and High Temperature Storage Life (HTSL) have been characterized. Samples are loaded into each reliability chambers and stressed until wearout open failure. Weibull plot is plotted for each reliability stresses and for three wire types. First failure (tfirst), median-time-to-failure (t50) and characteristic life (t63.2) and weibull slope (β) are calculated accordingly. Next study includes applying thermal storage conditions at 150 °C, 175 °C and 200 °C at various intervals time. The apparent activation energy (Eaa) has been investigated for HTSL and IMC thickness growth of Au, Pd-coated Cu wire and Pd-doped Cu wire. Dispatch oven is used in HTSL test. Results indicated that the obtained weibull slope (β) of three wire types are greater than 1.0 and belong to wearout reliability data point. Pddoped copper wire exhibits larger time-to-failure and cycles-to-failure in HAST, UHAST and TC tests. This proves Palladium (Pd)-doped copper wire has a greater potential and higher reliability margin compared to Au and Pd-coated copper wires. Bare Cu wire is not observed with lowest wearout reliability performance. Intermetallic compound (IMC) diffusion kinetics has been established among the different bonding wires. Eaa obtained of Au ball bonds are ranging from 0.92 ~ 1.10 eV and 0.72 ~ 0.83 eV for Pd-coated Cu ball bonds in HTSL test. For IMC thickness growth study, Eaa obtained for CuAl IMC are 1.08 eV and 1.04 eV respectively with EMC A and EMC B. Eaa obtained are 1.04 eV and 0.98 eV respectively on EMC A and EMC B on AuAl IMC. Wire pull and ball bond shear strengths have been analyzed and we found smaller variation in Pd-doped copper wire compared to Au and Pd-doped copper wire. In conclusion, Au bonds were identified to have faster IMC formation, compared to slower intermetallic compound thickness growth compared to Pd-coated Cu wire and Pd-doped Cu wire.
      10  3
  • Publication
    The optimization of multi-walled carbon nanotubes surface modification via nitric acid oxidation for DNA immobilization
    ( 2014)
    Shahidah Arina Shamsuddin
    This thesis discussed on the optimization of MWCNTs surface modification via nitric acid oxidation for DNA immobilization. After acid oxidation treatment, the impurities in multi-walled carbon nanotube (MWCNTs) such as carbonaceous and metal catalyst particles are successfully reduced as has been analyzed by energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD) and thermogravimetric analyzer (TGA). Acid oxidation will caused to the opening of MWCNTs tips and structural defects formed on the MWCNTs surface due to the acid attack. Oxygen containing functional groups, mainly, carboxylic group (COOH) has been introduced on the MWCNTs opened tips and at the defect sites which are useful to interact with other molecules, in this case, aminated-ssDNA probe. The results from fourier transform infrared spectroscopy (FTIR) and Raman Spectroscopy have shown that the COOH amount is depended on the MWCNTs structure defects. Meanwhile, cyclic voltammetry (CV) results have indicated that the immobilization current is directly proportional to the COOH amount. However, structure defect will affect to the immobilization current when ID/IG ratio is increased. The acid oxidation parameter should be optimized, thus the amount of COOH can be increased with the minimal structure defect. Therefore, the main goal to have a maximum immobilization current can be achieved. L9 Taguchi orthogonal array has been used to optimize the acid oxidation parameters. From the result, 5 M of nitric acid concentration, 120 °C of treatment temperature and 6 hours of treatment time are selected as the most optimum combination of acid oxidation parameters. The percentage influence of each main factor is also calculated to be 46% xvi 35% and 18% for nitric acid concentration, treatment time and treatment temperature, respectively. The improvement is happened to be 11.6% of increment in the immobilization current.
      3  19
  • Publication
    Nanohybrid mediated finely tuned novel ZnO/Au nanostructures for selective bio-capture towards nanodiagnostics
    ( 2015)
    Veeradasan A/L Perumal
    Nanoscale structures combined with noble metals are expected to yield novel materials that will create new avenues for diagnosis and therapeutics. Among various types of nanostructured metal/semiconductor hybrid that have been developed, nanostructured Zinc oxide (ZnO) has been intensively studied because of its unique nano-morphological, functional bio-compatible, chemical stability, sensitivity, non-toxicity, and high catalytic properties. The biocompatibility characteristics of ZnO make this material a convenient choice for conducting surface functionalization and interfacing with chemical and biological compounds at pH extremes. Nanohybrids that comprise ZnO and noble metal nanoclusters have attracted tremendous interest in recent years owing to their potential for improved catalytic activity, excellent surface area-to-volume ratio and several functionalities that are superior to those of pure ZnO nanomaterials. The objective of this research is to synthesize different type of Au doped ZnO nanostructures using simple solgel spin coating and low-temperature hydrothermal method to tract the profile of biomolecule (DNA) that lead to pathogenic leptospirosis and cholerae detection. Firstly, a thin seed layer of ZnO prepared by sol-gel method was deposited on the gold interdigitated electrode to provide the nucleation sites for growth of ZnO nanostructures. Next, ZnO NRs were grown using simple low temperature hydrothermal growth method. Consequently, ZnO NRs were sputtered with Au to form ZnO/Au nanostructures. Therefore, the fabricated ZnO/Au nanostructure was examined through various characterization for surface morphology (FESEM, TEM, AFM), structural (XRD, XPS), optical (PL, UV-VIS) and electrical properties (EIS, IV) investigation. Thus, the research has successfully demonstrated the application of novel two-step method, the combination of sol-gel and hydrothermal process to synthesize different nanostructures. Secondly, we have studied the effect of Au on the localized surface plasmonic of ZnO thin film. Incorporation through sputtering of Au into a ZnO thin film resulted in changes in the surface morphology as well as the optical and electrical behaviour. It was observed that the AuNPs tends to grow along with the ZnO thin film and the density of the AuNPs increases forming a continuous layer as the Au thickness increased from 10 nm to 50 nm. Based on the structural, optical and electrical analyses, incorporation of Au substantially improves the ZnO thin film. Furthermore, the effect of sputtered AuNPs on the conduction mechanism of ZnO Nanorods was also studied. It was observed that different sputtered thickness of AuNPs greatly affects the dielectric constant of ZnO Nanorods as well the conductivity of the device. Thirdly, we have selected novel spotted nanoflower structure among the different structure of nanowire fabricated to investigate the biosensing properties for impedance sensing to distinguish pathogenic and nonpathogenic leptospira species. Selective capture of molecular probes onto the seeded AuNPs was evidence for the specific interaction with DNA from pathogenic leptospirosis-causing strains via hybridization and mis-match analyses. The attained detection limit was 100 fM as determined via impedance spectroscopy. Furthermore, stability, reproducibility and regeneration of this sensing surface were demonstrated. Finally, we created a new worm like nanostructure with ZnO/Au hybrid through aqueous hydrothermal method, by doping Au-nanoparticle (AuNP) on the growing ZnO lattice. Further, the ability to create Au-decorated hybrid nano-worm structure for impedance sensing was proved to distinguish serovars of cholera. It was observed that the sensor was more sensitive over the literature documented AuNP incorporated doped ZnO nanorods xvii in detecting DNA at ambient temperature (10 fM). The fabricated sensor displayed the increment in grain boundary resistance from 0.17 to 1.13 MΩ when the target DNA concentration was increased from 1 μM to 10 fM. The biosensor based on Au-decorated hybrid nano-worm structure exhibited excellent linearity over a wide range of target DNA concentrations. Further, higher stability, reproducibility and regeneration on this sensing surface were demonstrated. The worm like nanostructure with ZnO/Au hybrid has superior sensitivity and selectivity compared to novel spotted nanoflower due to the improvement over structural defects such as Zinc- and/or Oxygen-vacancies. Such improvement facilitates the chemisorption of organic molecules towards the substrate, which is beneficial for the high loading of DNA during immobilization and hybridization processes. In addition, the AuNPs nano-radii in combination with the increased surface area due to random curving, significantly enhances the detection efficiency due to increased immobilization rates and enhanced hybridization efficiency. In conclusion, this research successfully demonstrated the process to synthesize, fabricate, characterize and validation of Au doped ZnO nanostructures based biosensor.
      7  13
  • Publication
    Development of silicon nanowire lab-on-chip microfluidics integrated biosensor for low concentration bio-molecules detection
    ( 2015)
    Tijjani Adam
    Lab-on-chip fabricated with one-dimensional nanowires offer excellent electrical properties where bio molecular analysis at very low concentrations is becoming increasingly relevant for medical and research communities. Good number of techniques and promising results has been established for detecting small concentrations; however, for high-throughput measurements and label-free detection are still area of fresh investigation. Many research groups have reported high level of bio recognition by using semiconductor nanowire. The semiconductors silicon nanowire biosensor utilizes a Nano wire between two conducting materials. The nanowire has its atoms concentrated on its surface. Thus, any small changes in the charges present on the nanowire will cause a change in the flow of current. In this thesis, a simulation study coupled with experimental approach to explain the change in wire surface behavior as function of the surface charge. The linear behavior of the conductivity to increase the sensitivity of a semiconducting nanowire biosensor is ascertained. The silicon wire should be between 5 to 20nm to allow mean distance between atoms, the oxide should be as thin as possible for optimum surface integrity, and the functional layer should be thin and have a high dielectric constant. The ionic concentration of the electrolyte should be kept low in order to have a large Debye screening length. To confirm these theoretical results, Silicon nanowire of ≈ 15nm was fabricated using conventional photolithography coupled with dry etching process. To determine the capability of the device, it subjected to various pH values and to achieve this, the device is being operated based on the principle of Field Effect Transistor (FET). The surface of the device is hole dominated (p-type material).
      6  11
  • Publication
    A computational analysis of interaction between inorganic semiconductor nanowire and molecular partial charge for DNA sensor application
    ( 2015)
    Abdulmohaimen W Fagri
    This research aimed to investigate the effects of partial charge due to DNA hybridization on the conductance of the silicon nanowire through finite element calculations. A biosensor was designed with the silicon nanowire of 15 nm radius at the core and surrounded by a silicon dioxide (2 SiO) layer of 2 nm thickness. The oxide layer was surrounded by a 5 nm thick functional bio-interface layer incorporating probe ssDNA and this whole system was immersed in an electrolyte of 80 nm radius. For the purpose of modeling and simulation, each of this layers was treated as a continuum medium characterized by the corresponding dielectric constant. In order to determine the effects of hybridization on nanowire conductance, the distribution of the electrostatic potential in the nanowire and other layers were first computed using Poisson equation with Boltzmann statistics without adding target DNA in the electrolyte layer. The conductance of the nanowire in this condition was computed by integrating the effect of the potential charge carriers within the nanowire and partial charge due to probe ssDNA. Then, the potential distribution was again calculated with the target DNA in the electrolyte and the conductance of the nanowire was re-calculated. Partial charge due to hybridization between probe and target DNAs was first computed using molecular dynamics simulation and integrated into the finite element calculation. The Finite element calculations showed that the nanowire conductance depended nonlinearly on the external charge (partial charge) of the bio-interface due to the hybridization of the target DNA with probe DNA in the functional layer.
      13  6
  • Publication
    Nano-diagnostics-on-chip: an innovative approach of quantifiable multi-analyte via tripartite polysilicon nanogap for prenatal care
    ( 2016)
    Sharma Rao A/L Balakrishnan
    “Everything grows rounder and wider and weirder, and I sit here in the middle of it all and wonder who in the world you will turn out to be”– Carrie Fisher. A quote portraying the dreams and emotions of every mother who wished to provide good health and life for the unborn. Current thesis has been motivated by the importance of providing early stage diagnosis and preventive healthcare to mother and child, which is one of the prime goals focused by the United Nation in Millennium Development Goals in 2015. Key importance has been given to the areas that have inadequate maternal healthcare, as rising numbers seen in maternal and fetal mortality and morbidity. Providing a rapid test result near patient is necessary to undertake safety precautions as well as reducing the patient’s anxiety of waiting time for the results. Herein, a novel, point-of-care nano-diagnostic device based on lab-on-chip biosensing is demonstrated using nanostructured polysilicon nanogap electrode, which assists a single drop fluid delivery by tripartite microchannels for multi-analyte diagnosis called ‘Prenatal-Care-on-Chip’. Polysilicon semiconducting material was chosen as the electrode for nanogap structure, and fine-tuned by varying deposition period and annealing process to facilitate a proper biosensing surface. The designing and fabrication of the lab-on-chip were performed in-house via conventional lithography and nanogap electrode structures by size reduction and expansion technique. Soft-lithography was employed to create microchannels by mold-casting. Another important aspect is the surface functionalization on the lectrode, which is crucial for selectivity and reliability of the biosensor. Various chemical modifications were examined in this study to analyze the performance (suitability, compatibility and sensitivity) of bio-receptor towards multi-analyte detection. Most crucial and healthcare demanding targets (analytes) for prenatal care were examined, such as Human Chorionic Gonadotropin for pregnancy assessment and Glucose for Gestational Diabetes Mellitus. Both prepared and clinically tested urine and saliva samples were investigated and analyzed by morphological, optical, structural and electrical studies to evaluate performance of the biochip.
      4  7
  • Publication
    Junctionless transistors: parametric study with conventional doping in MOSFETS
    ( 2016)
    Nurul Huda Abdul Rahman
    The advancement of today technologies has been aggressively developed as the needs of current technology that becoming competitive and demanding to accommodate human lifestyle. The electronic gadgets drive the market with the requirements to provide efficient chip functionality at higher speed and extra functionality. This has become more challenging as the transistor density and performance are aggressively increasing. Thus, continuous downscaling of the conventional transistor will lead to severe short-channel effect (SCE), and one of the solutions is a ultra-shallow junction. Ultra-shallow junction is very challenging as it increases in fabrication cost and difficulty in the fabrication process. In this study, the channel, drain, and source have the same type of doping where the ultra-shallow junction has been eliminated. Hence, it is called junctionless. There will be no diffusion will take place where it will remove the high cost for ultrafast annealing techniques. Besides that, it allows the transistor to be fabricated with a shorter channel if the gradient of the doping concentration is zero between drain and channel or source and channel. This operation principle of the junctionless transistor is investigated through numerical simulations using technology computer aided design (TCAD) simulation tools. Firstly, the device performance of 3-Dimensional (3D) silicon-on-insulator (SOI) junctionless transistor (JLT) with 100 and 10 nm gate lengths, have been compared to the 3D SOI junction transistor (JT) with the same gate length. In order to achieve full depletion, the parameters such as metal gate workfunction, doping concentration, drain bias, and dimension are considered in the simulation process. The digital figure-of-merits characteristics such as threshold voltage (VTH), on-current, subthreshold slope, and draininduced- barrier-lowering are the main parameters that have been investigated. Following next is the characterization on the analog and radio frequency (RF) figures-of-merit. Based on the simulations, 1) the designated JLT device is more suitable to the higher gate workfunction of more than 5.0 eV whereas the designated JT device is more suitable with mid-gap values of gate workfunction of 4.6 eV. 2) the JLT transistor requires high gate work-function to have control over the channel. 3) the JT device is less sensitive to the variation of silicon body thickness (TSi) and width (WSi) compared to JLT. Lastly, the device performance on analog and RF figures of merit shows that no significant different between JLT and JT with the latter case shows slightly better performance, related to lower gate-to-gate capacitance (Cgg).
      16  2
  • Publication
    Synthesis and characterization of Cu₂Zn₁-xCdxSnS₄ quinternary alloy structure nanostructures using sol-gel electrospining technique
    ( 2016)
    Authman Salim Ibraheam
    The principal aim of the research work presented in this thesis is to synthesise nanostructured Cu2Zn1-xCdxSnS4with different Cd concentrations (x=0 to 1)on glass, porous silicon (PS), oxidized silicon (SiO2) and GaN substratesusing different methods of spin coating and electrospinningtechniquesfor heterojunction, solar cell and Dengue type-2 DNA detector applications. In this work, we have studied the different effect copper (Cu) concentrations (0.3, 0.5, 0.7 and 0.9 mol/L) on the structural, morphological, optical and electrical properties of Cu2Zn0.8Cd0.2SnS4 quinternary alloy nanostructures prepared by spin coating technique. The direct band gap of Cu2Zn0.8Cd0.2SnS4quinternary alloy nanostructures decreases as Cu concentration increases from 1.81 eV at 0.3M to 1.60eV at 0.9M. The transmittance value in the range 63-49% was also dependent on Cu concentration. The refractive index and optical dielectric constant are calculated and gave good agreement with experimental and theoretical results. Electrical properties studied by Hall Effect measurement, showed ptype conductivity, with a carrier concentration between 7.819×1012 cm–3 and 3.76×1014 cm-3.It was observed a linear decreasing in the band gap of Cu2Zn1- xCdxSnS4/glassquinternary alloy nanostructures as Cd concentration increases.The transmittance value was 73% at x = 0 and 39% at x = 1. Hall Effect measurements suggest that all the grown nanostructures have p-type conduction. XRD results showed that Cu2Zn1-xCdxSnS4quinternaryalloy nanostructures has multiphase polycrystalline with preferential orientation along (112) and (312) directions with kesterite structure at x=0 and stannite structure at x=1.The Cu2Zn1-xCdxSnS4quinternary alloy nanostructures on PS (63.93%) substrate with different Cd concentration deposited via spin coating technique were successfully examined for heterojunction. The current-tovoltage (I-V) of Ag/n-PS/Cu2Zn1-xCdSnS4/Ag heterojunction at x= 0, 0.6, 1 was characterized. The photosensitivity increases as Cd concentration increases to of (3401.36) for x=0.6 compared with (282.40) for x=0 and (567.68) for x=1 respectively. Different method electrospinningtechnique is used to synthesise of Cu2Zn1- xCdxSnS4quinternaryalloynanofibres.
      3  8
  • Publication
    Optimization of P-I-N rectifier diode for yield and robustness improvement using DOE
    ( 2016)
    Cheh Chai Mee
    The Power Rectifier (P-i-N rectifier) is one of the widely used diode in high power semiconductor devices as circuit protection. This popularity comes from excellent reverse voltage blocking and fast switching time. As a result, the exploration on the power rectifiers to make the device more robust and competitive in the market is boundless, which aims for continuous improvement on the electrical characteristics. In general, the P-i-N rectifier is consists of a highly-doped P-N junction with a low doped intrinsic region sandwiched in between the regions. Such characteristics have made the design of as high as 1000 V reverse voltage diode is possible by lowering the switching time. This thesis describes the research work done on the power rectifier by exploring the device characteristics and optimizing the input responses using Design of Experiment (DOE) techinique. Parameter such as epitaxial layer specification, junction drive time and also other internal fabrication processes were optimized, to produce a desired device robustness and yield improvement. The main electrical characteristics namely reverse recovery lifetime, reverse voltage, reverse leakage current and such, were investigated and analyzed. The results show that with implementation of optimized epitaxial thickness and resistivity, the P-i-N power diodes were able to withstand high reverse voltage. The optimum epitaxial thickness for 600 V device is at 96 μm. The epitaxial thickness is a dominant factor as compared to epitaxial resistivity and boron diffusion time. Next, the variation in junction drive time shows a direct relationship between the junction depth of the P-i-N rectifier to the reverse voltage for 200 V device. Each additional 60 minutes in boron diffusion time will increase the device reverse voltage by 30 V. Lastly, the investigations are about reverse recovery lifetime and forward voltage of the power diode.
      12  6