No description available.

No description available.

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.

No description available.

Industrial production of hydrogen from the syngas, generated from steam reformation of natural gas or coal gasification, sets conditions for hydrogen separation membranes in terms of operating conditions. An alternative source for hydrogen is a syngas generated by gasification of municipal solid wastes which are likely to set more stringent conditions for the separation membranes. There is therefore, a growing demand for separation membranes with improved permeability and particularly of low cost. Among various alternatives, metallic membranes are particularly attractive due to their high selectivity and permeability for hydrogen, exemplified by palladium (Pd). However, due to high cost of Pd there is still a demand to develop alternative metallic membranes that are of low cost and have improved durability. Efforts have therefore concentrated on either alloying Pd so as to reduce its cost or on alternative membrane compositions of particularly b.c.c. structure. The current study deals with hydrogen separation membranes and aims to develop infrastructure for rapid identification of membrane compositions with improved permeability. The study is made up of three parts / i) development of sputter deposition system that would allow deposition of multiple compositions in a single experiment, ii) development of substrate material that would support the thin film membranes and would allow permeability measurement and iii) development of a set-up to measure the permeability of the thin film membranes. In the present thesis, a sputter deposition system incorporating three targets was successfully constructed. The system as tested with palladium-niobium-titanium (Pd-Nb-Ti) ternary system after necessary adjustment would yield thin films of homogenous thickness (&le / 7%) over a sample area of &asymp / 150 mm diameter. A total of 21 substrates each in 19 mm diameter arranged in triangular form in the substrate holder could successfully be deposited where composition distributions covered a greater portion of Pd-Nb-Ti ternary phase diagram. The structure of the deposited thin films can successfully be controlled by substrate temperature as well as by the pressure of plasma gas (argon). With the help of these parameters, structural diversity can also be produced beside the compositional variation. As for substrates, two materials were investigated. These were titanium dioxide (TiO2) modified porous stainless steel (PSS) and anodic porous alumina (AAO). TiO2 modified PSS due to its associated surface roughness leads to the deposition of films with defected structure which as a result is not gas tight. AAO produced via anodization of aluminum foil had a regular (40-60 nm) pore structure that provides a suitable surface for thin film depositions which could be defect free. However, AAO is very delicate and fragile which makes it difficult to adapt it as a support material for permeability measurement/hydrogen separation purposes. Finally, a set-up was developed for measurement of hydrogen permeability which is capable of measurement over a wide pressure and temperature conditions, i.e. hydrogen pressures up to 10 bar and temperature as high as 450 &deg / C. It is recommended that so as to identify compositions with improved permeability, Nb or a similar metal which has extremely high permeability could be used as a support material. This would tolerate the evaluation of the films which are not totally defect free.

Near infrared region (NIR) of the electromagnetic spectrum (EM) is defined as 700nm to 1400nm wavelength interval by International Commission on Illumination(CIE). This wavelength interval is extensively used for target acquisition, night vision, wireless communication etc. Therefore, filtering the desired portion of EM spectra becomes a need for that kind of applications. Interference filters are multilayer optical devices which can be designed and produced for the desired wavelength intervals. The production of near infrared interference filters is a process of depositing thin material layers on the suitable substrates. In this thesis, a multilayer NIR filter will be designed for a selected wavelength interval by the use of dierent materials. Then, transmission quality, thermal stability, dependence of the transmission values on the incoming beam angle, performance and durability of the filter will be studied.

The aim of this work is plasma diagnostic during the deposition of thin films based on organosilicone compounds. These layers have a wide range of applications mainly as protective coatings or intermediate phase in composites reinforced by glass fibers. The theoretical part of this work gives a basic fundaments of optical emission spectroscopy and mass spectroscopy and describes procedures for rotational, vibrational, and electron temperature calculations. The RF capacitive coupled discharge in configuration with planar electrodes was used with tetravinylsilane (TVS) organosilicone monomer in this study. The optical emission spectroscopy and mass spectroscopy were applied for the plasma diagnostics. The deposition process was carried out in continuous regime with applied power of 20, 25, 40, 50, 60, and 70 W, some experiments were done also in pulsed regime with duty cycle 1:1, 1:4 and 1:9 at fixed power of 50 W and 10 W when discharge was on. The atomic lines of hydrogen Balmer series and many rotational lines of molecular hydrogen were identified in the spectra. Besides them, the molecular bands of SiH, CH and C2 species were observed. The rotational temperature calculated from 0-0 CH band was in the range of 600 – 1000 K depending on the discharge conditions. The electron temperature in the range of 3600-7500 K was calculated from hydrogen atomic lines. In situ mass spectra collected simultaneously with optical emission spectra showed TVS monomer fragmentation increase with the increase of applied power in continuous regime. This result well correlated with OES in case of CH radical and hydrogen species, the other particles were mainly non-measurable by emission spectroscopy. The same results were also obtained with respect to the duty cycle parameter. The presented results clearly demonstrated the increase of monomer fragmentation with the increase of mean applied discharge power. Determination of prepared layer properties is a subject of other works and their relation to the plasma parameters will be a subject of further studies.

Das Ziel der vorliegenden Arbeit war die erstmalige, umfassende und systematische Untersuchung aller Teilprozesse bei der ionenstrahlgestützten Schichtabscheidung (IBSD). Silber (Metall) und Germanium (Halbleiter) wurden als Beispielsysteme ausgewählt, da auf Grund der unterschiedlichen Eigenschaften der beiden Materialien prinzipielle Unterschiede in der Zerstäubung und Schichtabscheidung zu erwarten sind. Zur Bearbeitung der wissenschaftlichen Fragestellung erfolgte eine Charakterisierung der Primärteilchen sowie der zerstäubten und gestreuten Teilchen bezüglich ihrer Energie und Winkelverteilung sowie eine Charakterisierung der abgeschiedenen Schichten bezüglich ihrer Schichtdicke, Komposition, Struktur, Oberflächentopographie, elektrischen und optischen Eigenschaften unter Variation der Art (Argon und Xenon), der Energie (0.5 keV–1.5 keV) und des Einfallswinkels der Primärteilchen relativ zur Targetnormalen (0°–60°) sowie des betrachteten polaren Emissionswinkels (-40°–90°). Die dargestellten Ergebnisse demonstrieren den systematischen Einfluss der primären Prozessparameter (Ionenart, Energie, Einfallswinkel und Emissionswinkel) auf die Eigenschaften der zerstäubten und gestreuten Teilchen und auf die Eigenschaften der erzeugten Silber- und Germaniumschichten, wobei die Eigenschaften der abgeschiedenen Schichten mit den Eigenschaften der schichtbildenden Teilchen korrelieren. Bei der IBSD von Silber führt der Einfluss der hochenergetischen zerstäubten und gestreuten Teilchen auf die Schichten zu kleineren mittleren Korngrößen und damit zu höheren spezifischen Widerständen und Variationen in den optischen Eigenschaften. Die Untersuchungen zur IBSD von Germanium zeigen, dass der Einbau von Prozessgas in die abgeschiedenen Schichten mit der Anzahl der gestreuten Primärionen, deren Energie hoch genug für eine Implantation in die Schicht ist, korreliert werden kann.