Electrospray is an atomization method subject to intense study recently due to its monodispersity and the wide size range of droplets it can produce, from nanometers to hundreds of micrometers. This thesis focuses on the numerical and theoretical modeling of the interaction of charged droplets from the single and multiplexed electrospray. We studied two typical scenarios: large area film depositions using multiplexed electrospray and fine pattern printings assisted by linear electrostatic quadrupole focusing. Due to the high computation power requirement in the unsteady n-body problem, graphical processing unit (GPU) which delivers 10 Tera flops in computation power is used to dramatically speed up the numerical simulation both efficiently and with low cost. For large area film deposition, both the spray profile and deposition number density are studied for different arrangements of electrospray and electrodes. Multiplexed electrospray with hexagonal nozzle configuration can not give us uniform deposition though it has the highest packing density. Uniform film deposition with variation < 5% in thickness was observed with the linear nozzle configuration combined with relative motion between ES source and deposition substrate. For fine pattern printing, linear quadrupole is used to focus the droplets in the radial direction while maintaining a constant driving field at the axial direction. Simulation shows that the linear quadrupole can focus the droplets to a resolution of a few nanometers quickly when the interdroplet separation is larger than a certain value. Resolution began to deteriorate drastically when the inter-droplet separation is smaller than that value. This study will shed light on using electrospray as a scalable nanomanufacturing approach.

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Niobium thin films are expected to be free of solid inclusions commonly seen in solid niobium. For particle accelerators, niobium thin film has the potential to replace the solid niobium in the making of the accelerating structures. In order to understand and improve the superconducting performance of niobium thin films at cryogenic temperature, an energetic vacuum deposition system has been developed to study deposition energy effects on the properties of niobium thin films on various substrates. The system directly uses microwave power to create a pure niobium plasma, which can be used to extract niobium ion flux with controllable kinetic energy for direct deposition. The ultra high vacuum avoids the gaseous inclusions in thin films. A retarding field energy analyzer is developed and used to measure the kinetic energy of niobium at the substrate location. A systematic process for thin film characterization is developed and used to analyze the niobium thin films made by this energetic condensation. The properties of niobium thin films at several deposition energies are obtained, and the results show that there exists a preferred deposition energy around 115eV. / Ph. D.

In the first part of this dissertation work, Al bond pad corrosion behavior was investigated in the presence of common industrial contaminants such as chloride (Cl-) and fluoride (F-). Al corrosion while in direct contact with Cu displayed rapid hydrogen (H2) gas evolution and dendrite propagation. In contrast, Al without bimetallic contact showed only minor surface roughening. This observed difference in the corrosion mechanism between Cl- and F- is attributed to the solubility of the corrosion products (AlCl3 vs. AlF3) formed on the Al surface. Our subsequent work explored corrosion prevention inhibition of wire-bonded devices (WBD) in the Cl- environment. Our research shows that the Al bond pad was protected against corrosion by chemically modifying the surface of the Cu wires, thereby preventing the H2 evolution. The inhibitor was observed to be highly selective, thermally stable, hydrophobic, and cost-effective, making it viable for industrial application of this coating for Al bond pad corrosion prevention. In the second part of the dissertation work, we utilized a novel approach of using ultraviolet-visible spectroscopy (UV-Vis) as a chemical-sensitive monitoring tool of the chemical environment in Cu etch bath. The UV-Vis technique illuminates the roles of H+, Cl-, Cu+, and Cu2+ to the etch bath while also providing a means to monitor the Cl- in the broad UV peak at 250 nm. The UV-Vis probe successfully demonstrated the etch rate difference between the two etch bath solutions and help in the restoration of the etching bath. Additionally, the proof-of-concept experiments (POC) to investigate UV enhanced etching for achieving anisotropic etching in PCB fabrication showed promising preliminary results with the need to develop additional etching techniques.

Mesoporous semiconductors such as TiO2 nanoparticles, as well as transparent conducting oxides (TCOs) such as indium tin oxide films are typically employed for setting up the photo-electrode module in variety of photoelectrochemical cells including Dye-Sensitized Solar Cells (DSSCs). In order to exhibit a high performance efficiency, the photo-electrodes in such applications are required to be able to harvest the light and transport the generated electrons effectively. Accordingly mesoporous layers with high values of surface area and well-established pore structure along with highly transparent and conductive TCOs are deposited on suitable substrates through the physical or chemical vapor deposition methods. The processing facilities and materials required to fabricate such high-quality devices with high values of efficiency are complicated and expensive, whereas devices of lower quality do not fulfill the demands. This issue is of particular importance regarding the energy production and developing the solar cell technologies, as it is considered by the concept of “cost per watt”. Thus, a great deal of effort is being carried out globally to enhance the efficiency of affordably-produced solar cells such as low-cost DSSCs. Utilizing the wet chemical techniques such as sol-gel method which provide a considerably more affordable route to synthesize nanoparticles and deposit thin films without the need of applying high temperature or vacuum condition is a widely-used approach to decrease the processing expenses. However, to achieve an acceptable cost-per-watt ratio requires enhancing the obtained efficiency value as well, and therefore, modifying the processing procedures to improve the required features of the products are highly encouraged. This thesis focuses on two individual activities: synthesis of TiO2 nanoparticles, and also thin film deposition of a promising TCO called aluminum-doped zinc oxide (AZO); both obtained through the sol-gel route that is modified to contribute to nanostructures with suitable features for application in photoelectrochemical devices such as DSSC. In the first part, mesoporous anatase nanoparticles were synthesized through the surfactant-mediated sol–gel route. Through changing the refluxing time and water-to-surfactant molar ratio, as-prepared nanocrystals of high density and large and narrowly-distributed pore sizes were obtained, displaying surface area values up to 240 m2·g-1, much higher than the reported values for commercial TiO2-based catalysts. In the second part, sol–gel dip–coating of ZnO thin films doped with 2 at.% of aluminium ions was carried out. By altering the hydrolysis reaction and changing the thermal treatment procedure, thin films of highly c-axis preferred orientation were obtained with optical transmittance of around 80% and resistivity values down to 6 – 15 mΩ·cm, corresponding to sheet resistance of around Rsh ~ 500 Ω/sq. The obtained conductivity values, even though one order magnitude lower than those reported for the AZO thin film prepared via expensive techniques, are in the suitable range to improve the cost per watt ratio in applications such as inkjet printing of low-cost printed electronics and more affordable DSSC devices.

Current gas sensor technology, although meeting the minimum requirements in many instances, suffers for a number of limitations. Hence, there is currently a considerable volume of research being undertaken at many laboratories of different countries. In the past, all chemical sensors and catalyst were optimized empirically by a trial and error method. Today, however, systematic research and development is becoming increasingly important in order to improve sensors and to find new sensing principles. Obtaining a long term stable gas sensor with improved sensitivity, selectivity, and low cost for mass production passes through fundamental research and material characterization to build new chemically sensitive devices or to improve existing ones. The bottom line in the design and manufacture of modern gas sensors is the transfer from ceramic(of Figaro type) to thin film gas sensors(TFGs). This transfer provides new opportunities for further microminiaturization, power consumption and cost reduction of gas sensors. Therefore, at the present time, thin film gas sensors are the basis for the design of the modern gas sensitive multi-parameter microsensor systems. Applications of these systems include environment, security, home systems, smart buildings, transportation, discrete manufacturing, process industries and so on. Microelectromechanical systems(MEMS) based integrated gas sensors present several advantages for these applications such as ease of array fabrication, small size, and unique thermal manipulation capabilities. MEMS based gas sensors; which are usually produced using a standard CMOS(Complimentary Metal Oxide Semiconductor) process, have the additional advantages of being readily realized by commercial foundries and amenable to the inclusion of on-chip electronics. In order to speed up the design and optimization of such integrated sensors, microheater designs for gas sensor applications have been presented as first part of the present thesis. As heater design is the key part for a gas sensor operation. So 3D simulations have been used to optimize micro-heater geometry. The application of MEMS Design Tool(COVENTORWARE) has been presented to the design and analysis of micro-hotplate (MHP) structures. Coupled Electro-thermal analysis provided an estimation of thermal losses and temperature distribution on the hotplate for realistic geometrical and material parameters pertinent to fabrication technology. Five microheater designs have been proposed in terms of different sizes and shapes in order to optimize the microhotplate structure to be used for gas sensor operation for the specified range of temperature and power consumption. To produce a gas sensor, which is able to detect LPG leak, thin films of tin oxide have been developed. FR sputtering has been used to deposit gas sensitive tin oxide thin filmls under various deposition conditions. Four different values of pressure in the range from high pressure(5 X 10-2 mbar) to lower pressure (2 X 10-3 mbar), three RF power values 50, 75, 100 W and varied oxygen percentage in sputtering atmosphere (0-18%) have been used to optimize the material properties of tin oxide thin films to study the sensitivity towards LPG. All the samples have been analyzed using various macro and microscopic characterization techniques. Extensive studies have been done on the sensor response for the samples deposited under different conditions. Finally the sample film deposited at 5 x 10-3 mbar, with applied power of 75 W in the presence of 8% oxygen, showed maximum sensitivity towards LPG.