Advanced Materials Research Vol. 925

Abstract: Reactive Ion Etching (RIE) is an important process in fabrication of semiconductor devices. Design Of Experiment (DOE) has been used to study the effect of Reactive Ion Etch (RIE) towards surface morphology of aluminum bond pad. Important RIE factors involved in this experimental study are ratio of Tetrafluoromethane (CF₄), Argon gas flow, BIAS, and ICP power. Different combinations of these factors produces different results of surface morphologies which was obtained using Atomic Force Microscopic (AFM). Produced results shows that overall surface roughness of the pad is affected by RIE and DOE offers a better way to optimize the desired outcome.

Abstract: Zinc doped nanoceria powders were prepared by a simple and fast microwave induced combustion method using cerium nitrate, zinc nitrate, glycine and sorbitol. The resultant powders were examined for their structure and microstructure by XRD, SEM, TEM and their optical properties were measured by UV-Vis spectroscopy. The lattice parameter of the ceria powders was found in the range of 5.399 Å to 5.370 Å. The average crystallite size calculated from XRD was in the range ~ 4 nm to ~ 2.5 nm. The TEM selected area diffraction pattern images clearly showed the ring pattern indicated the powders were polycrystalline nature and there is agglomeration of the particles. Optical band gaps of the powders were in the range 2.71eV to 2.58eV.

Abstract: Immobilized cell reactor (ICR) has been used widely for bioethanol production. It has been shown to improve the performance of fermentation efficiency. The immobilization of S.cerevisiae was simply performed by enriched cells cultured media harvested at exponential growth phase. Hydroxyapatite (HAp) was found to be a suitable candidate as a solid support of surface adsorption by S.cerevisiae. The strong affinity binding of phosphate backbone of S.cerevisiae and calcium ion in HAp had been proven the effectiveness of HAp as immobiliser, thus the yield from the fermentation process has been increased. However, specific characteristics for HAp-yeast complex such as size, porosity (pore size and pore volume), surface morphology and total surface area are the important factors that were needed to control in order to avoid the detachment of the microorganisms from solid support. The characterizations performed were Mastersizer for complex size determination, Scanning Electron Microscopy (SEM) for surface morphology and Brunauer, Emmett and Teller analysis (BET) for specific surface area determination.

Abstract: Thermosonic Copper (Cu) wire interconnection has been under an extensive research and development to replace expensive Gold (Au) wire material in the semiconductor industry. However, a reliability concern is raised due to void formation at the bonding interface of Copper wire-Aluminum bond pad (Cu-Al) after High Temperature Storage (HTS) annealing condition. It is believed that the Intermetallic Compound (IMC) layer growth and evolution lead to a volumetric shrinkage which in turn results in the void formation. Annealing conditions influence the development of the IMC at the bonding interface which is related to the bonding reliability. In this work, the effects of annealing toward the micro-structure and IMC growth at the bonding interface were evaluated using Scanning Transmission Electron Microscope equipped with Energy Dispersive X-ray analysis. In the as-synthesized sample bonded at 100°C, an inhomogeneous IMC formation dominated by grain boundary diffusion was observed. After High Temperature Storage of 1000 hours, the consumption of the Al bond pad resulted in the formation of irregular IMC layers. The variation of phases existed in a localized region was believed due to simultaneous growth of IMC by both grain boundary and volume diffusions. Moreover, the diffusion of Cu into Si was observed. This resulted in the formation of the mixture of Si + η phases in the affected sea region.

Abstract: Solar cell is one of the promising alternative green energy sources that can provide free electricity when sunlight is converted. The absorbent materials and their synthesis methods are subject of interest mainly due to solar panel installation cost despite of free electricity generated. The well-known silicon solar cells made, either amorphous or polycrystalline are good in conversion efficiency up to 17%, but their high cost make the researchers to look for alternate materials. Semiconducting materials in thin film form such as InP, SnO₂ and ZnO are being studied as the alternative materials, but are not commercialised due to their poor conversion efficiency. Another group of semiconductor compounds known as transition metal chalcogenides (TMC) have been developed to be used as the absorbent materials. Consisting of transition metals and chalcogenides (S, Se and Te), they show promising solar absorbent properties such as semiconducting band gap, well adhesion to substrate and good conversion with better cost-effective. There are many TMC compounds synthesised, including copper indium selenide (CIS), ZnTe₂, CdSe etc. Nickel, one of the transition metals synthesised with chalcogenides are referred as nickel chalcogenides. There are many possible combinations of nickel chalcogenides such as NiS₂, NiSe, NiSe₂ and Ni₃Se₂. The combination of nickel and telluride are the fewest being observed due to the nature of tellurium that is poorly-adhesive onto the substrate. Therefore, NiTe₂ thin film is being electro-synthesised onto the indium tin oxide (ITO) coated glass substrates and their properties are studied. The additives are being used to improve the adhesion between the film and substrate. Cyclic voltammetry experiments have been done prior to electrodeposition in order to get the electrodeposition potential range where the observable reduction range is between-0.9-(-1.1) V. The electrodeposition is carried out using the potentials in the reduction region, producing the well-adherent, well-distributed and dark-coloured thin films.

Abstract: The structural properties of Zn-doped and undoped lead iodide ( PbI₂ ) nanostructures have been investigated. Zn-doped and undoped of ( PbI₂ ) have been grown by chemical technique. Different doped and undoped PbI₂ when prepared successfully by thermal evaporation technique an glass substrate at room temperature. Characterization and analysis using scanning electron microscopy (SEM) and X-ray diffraction (XRD) have indicated to the crystalline character. The particle size of Zn-PbI₂ is larger than undoped PbI₂.

Abstract: The aim of the presented study is to investigate the thermo-physical behaviour and mechanical properties of mortar pre-coated crumb rubber concrete block. For this purpose, thermal conductivity, emissivity and effusively will be tested in addition to the specific heat capacity. Thereafter, dynamic calculator software will be used to study the behaviour of a wall that constructed using the suggested concrete block and a comparison with a normal concrete wall will be made. Compressive, splitting tensile and flexural strength were tested as well. The results show that concrete blocks which meet the requirement of strength can be produced with about 300 kg/m³ of crumb rubber aggregate.

Abstract: CdS/glass nanostructures are prepared at 400 °C by sol-gel spin coating method without catalyst. These nanostructures have been characterized by analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM). The grin size, full width half maxima, miller indices, strain, dislocation density, lattice constant and interplaner distance are measured. The measured and calculated results showed a good agreement with other experimental and theoretical data.

Abstract: In this study, two sets of pure aluminum strips 3 mm in thickness were friction stir welding (FSW) together in a regular Butt joint pattern. Two rotational speeds of 1750 RPM and 2720 RPM were utilized to perform the welding process. The transverse speed and the axial load were kept constant at 45 mm/min and 6.5 kN respectively. As a welding tool, cylindrical shoulder and pin geometry was selected. For comparison purposes other similar strip pair sets were butt welded using the conventional metal inert gas arc welding technique (MIGAW). The welding quality, power input, microstructure, macrostructure and the mechanical properties of the weld joints yielded from these two welding techniques were examined. The types of the fumes and the amount of the released gases during these two welding processes were measured and compared. The results proved that the solid state friction stir welding is clean, cost effective and environment friendly process as opposed to the conventional metal inert gas arc welding.

Abstract: Nucleation and condensation of mercury vapor has been investigated in various divergent angle and operating condition. Divergent angle has a great effect on droplet size at the end of nozzle. Influence of operating condition such as pressure and temperature on the size of droplet has been investigated. A one-dimensional mathematical model based on classical nucleation and growth has been developed to calculate the nucleation and condensation of mercury vapor. A mercury vapour turbine has been used in conjunction with a steam turbine for generating electricity. The mercury cycle offers an efficiency increase compared to a steam-only cycle because energy can be injected into the Rankine Cycle at higher temperature. The target of modeling is predicting the droplet size of mercury nanoparticles during rapid expansion. The results are verified by accurate experimental data available in the literature. The governing equations were solved using Runge-Kutta third-order numerical method in MATLAB software.