Advanced Materials Research Vol. 832

Abstract: The effect of calcination temperature for Fe₂O₃/MgO catalysts on the formation of carbon nanotubes (CNTs) was examined. CNTs were synthesized over Fe₂O₃/MgO catalysts calcined at different temperatures by catalytic decomposition of methane at 1000°C. The synthesized CNTs were investigated by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results show that the effect of calcination temperatures greatly governed the diameter and the quality of the SWCNTs formed. The catalysts calcined at 500, 600 and 700°C produced CNTswith the diameters of 1.53, 1.95 and 2.97nm, respectively. Generally, an increase in the calcination temperature increases the average diameter and decreases the quality of the CNTs produced.

Abstract: Fe₃O₄ was used to synthesize narrow diameter of carbon nanotubes (CNTs). The effect of concentration of Fe₃O₄ on the diameters of carbon nanotubes (CNTs) synthesized by methane decomposition at 1000°C was investigated. We used conventional impregnation method to prepare Fe₃O₄/MgO catalysts. The results show that the concentration of Fe₃O₄ greatly affects the diameter distributions of produced CNTs. The CNTs formed by Fe₃O₄/MgO catalysts, with the mole ratio set at 0.25:9.75 and 1:9 had diameter of 3.23 ± 1.71 and 49.04 ± 33.62nm, respectively, showing that a decrease in concentration of Fe₃O₄ yields smaller diameter and narrower diameter distribution. A growth model explaining tip-growth and base-growth mechanism is proposed for understanding formation of CNTs.

Abstract: Main purpose of this research is to study the optical and electrical characteristic of zinc oxide material after undergoing annealing process at various time period. Hypothesis of this research have proved that the physical properties of zinc oxide material have changed by increasing time period for annealing process due to changes of optical and electrical characteristic of ZnO material. Morphological observation shows that, the transmittance properties of ZnO material on glass substrate varies after annealing at time period 5 hours compare to annealing time of 3 hours followed by annealing time of 1 hour. All the annealing process is conducted at temperature 200°C. Zinc oxide is synthesized through a facile method which is known as sol-gel method. Sol-gel solution is prepared based on mixture of zinc acetate dehydrate and stabilizer mono ethanolamine (MEA) with ratio 1:1 and the mixture solution is left for more than 24 hours for precipitation process to occur. The prepared solution is then coated with 3 layers on silicon oxide substrate and annealed at time period of 1 hour, 3 hours and 5 hours. The annealed samples with different period of time is further characterized through UV-Vis test and electrical test.

Abstract: The article describes the fabrication and characterization of silver microgap sensor on silicon substrate. By employing cheap photolithography process the proposed microgap sensor has been fabricated. The silver microgap sensor was used for pH sensing, by dropping different pH on microgap surface. To obtain the microgap sensor structure by using AutoCAD software, mask was designed. To maintain high accuracy in pattern transfer the AutoCAD design mask was transferred to chrome glass mask. The fabricated silver microgap pH sensor gap spacing was around 03μm. From the electrical data we conclude that when the pH value varies from acidic to basic (pH 1, pH 2 to pH 11, pH 13) the value of capacitance decreased from 33pF to 8pF. The result shows that the silver microgap pH sensor has the ability to differentiate the acidic pH form basic one. The next part of the research is to decrease the microgap spacing until reach to nanosize spacing, so that can easily used for biosensing application.

Abstract: In Micro/Nanowire fabrication, the alignment and exposure process are the most critical steps in photolithography process, and indeed for the whole biochip processing. This process determines the success of transferring the Micro/Nanowire design pattern on the mask to the photoresists on the wafer surface. Hence, the resolution requirementsand precise alignment are vital; each mask needs to be precisely aligned with original alignment mark in order to transfer the original pattern from mask onto photoresist layer. Otherwise, itcant successfully transfer the original pattern to the wafer surface causing device and circuit failure. Therefore, the UniMAPs Second Generation Mask Aligner is used for precise alignment and pattern transfer process. Thus, the paper present a preliminary study on fundamentals of resist exposure and development mechanisms for fabrication of Micro/Nanowire, We demonstrated significance of considering process parameters such as mask aligner, quality of resist, soft bake, exposure time and intensity, and development time. There was a very little room for alignment error; we were able to achieved error free design to the criticaldimension.

Abstract: A simple design and simulation of microwire, contact pad and microfluidic channel on computer aided design (CAD) for chrome mask fabrication are described.The integration of microfluidic and nanotechnology for miniaturized lab-on-chip device has received a large research attention due to its undisputable and widespread biomedical applications. For the development of a micro-total analytical system, the integration of an appropriate fluid delivery system to a biosensing apparatus is required. In this study, we had presented the new Lab-On-Chip design for biomedical application. AutoCAD software was used to present the initial design/prototype of this Lab-On-Chip device. The microfluidic is design in such a way, that fluid flow was passively driven by capillary effect. Eventually, the prototype of the microfluidics was simulated using Comsol Multiphysics software for design validation.The complete design upon simulation is then used for mask fabrication. Hence, three mask is fabricated which consist of microwire, contact pad and microfluidics for device fabrication using photolithography process.

Abstract: For a submicron photolithography process, there is little room for error. In this paper, an optimized technique for photoresist (PR) development is reported, to fabricate a nanogap biosensor for application in biomedical nanodiagnostics. The pattern transfer on the wafer substrate requires precise alignment and Deep Ultra-Violet (DUV) light exposure. This research describes the photolithography process to develop a standard manufacturing procedure for pattern transfer from chrome mask. The key factor for PR development is understood and the optimization is done based on the PR thickness, spin speed, spin time, exposure time, post-exposure bake (PEB) time, developer concentration and developing time to achieve the design feature size of 1 micron. The PR is coated and spun at 3000 rpm and 5000 rpm at 30s and 40s respectively to form a very thin layer. However, the UV exposure time is remained constant at 10s. After the pattern transfer, the wafer is immersed in different concentrations of RD6 developer to develop the PR. To further improve the resolution of image transfer, the PEB time is also optimized for a better throughput on feature size. These optimizations are important to reduce the dimension error and were able to achieve error free design to protect critical dimension and prevent device failure.

Abstract: One of the advantages of silicon substrate over other semiconductor substrate is the high temperature process capability of the silicon. In this work, silicon wafer is used for thermal processing which involves many high temperature processes such as oxidation and deposition. Thin films on the wafer surface are investigated for its thickness and uniformity. Silicon dioxide (SiO₂) is initially grown using wet oxidation method and characterized for its thickness using FilmetricsSpectrometer. The thickness of SiO₂ achieved is less than 300nm. Silicon Nitride (Si₃N₄) is then deposited by sputter method and its thickness is measured at 210 nm. For the electrode, polysilicon (PolySi) is deposited using Low Pressure Chemical Vapor Deposition (LPCVD) process. Silane (SiH₄) is used as the source forPolySi deposition and the thickness is measured at 160nm. Standard deviation is calculated based on the layer thickness and the uniformity is checked across 5 points on the wafer. Hence, it is very important to have a uniform layer across the wafer surface for a defect free device and at the same time it protects the sensitivity of the sensor.

Abstract: In this study, the effect of anodizing voltage on the morphology of porous anodic alumina and growth kinetics of anodizing of aluminium manganese alloy was reported. It was found that the increasing anodizing voltage affect the morphology and dimensional parameters of porous AAO. Both pore diameter and interpore distance increased as a function of anodizing voltage. The regularity of porous AAO was affected by anodizing voltage. Dielectric breakdown occurred at anodizing voltage of 70 V and led to protrusions and cracks of the porous anodic alumina. Moderate anodizing voltage promoted the formation of well ordered pore arrangement while disordered pore arrangement was observed when the anodizing voltage was too low or too high. The thickness of porous AAO increased as the anodizing voltage increased.

Abstract: The Efficiency of Energy and Exergy is Generally Used as the Mostimportant Parameter in Order to Introduce and Compare the Thermal Systems Offlat Plate Solar Collectors. the First Law of Thermodynamics is Not Solelycapable of Demonstrating Quantitative and Qualitative Performance of Suchsystems, so the Second Law is Required to Illustrate the Performances. in Thispaper, an Analysis was Done for Heat Transfer Performance and Exergy Efficiencyof Flat Plate Solar Collectors Using Four Types of Nanofluids, e.g. Zno/water,CeO₂/water, Nio and Coo/water. these Nanofluids were Used Withdifferent Nanoparticle Volume Fractions in the Range of 1% to 4%. Besides this,the Present Work also Focuses on the Performance of Solar Collector Withdifferent Volume Flow Rates. Investigation Consequences are also Compared Withthe Presently Available Literature for Conventional Solar Collectors. Thehighest Heat Transfer Performance and Exergy Efficiency were Obtained for CeO₂/waternanofluid among all Nanofluids. Nio/water and Coo/water Nanofluids Representalmost same Performance but Higher than Water. the Results Reveal that, CeO₂/waternanofluid Indicates Maximum Heat Transfer with Maximum Exergy.