The thin film technology is of great importance in modern society and is a key technology in wide spread applications from electronics and solar cells to hard protective coatings on cutting tools and diffusion barriers in food packaging. This thesis deals with various aspects of thin film processing and the aim of the work is twofold; firstly, to obtain a fundamental understanding of the sputter deposition and the reactive sputter deposition processes, and secondly, to evaluate sputter deposition of specific material systems with low friction properties and to improve their performance.From studies of the reactive sputtering process, two new methods of eliminating the problematic and undesirable hysteresis effect were found. In the first method it was demonstrated that an increased process pressure caused a reduction and, in some cases, even elimination of the hysteresis. In the second method it was shown that sufficiently high oxide content in the target will eliminate the hysteresis. Further studies of non-reactive magnetron sputtering of multi-element targets at different pressures resulted in huge pressure dependent compositional gradients over the chamber due to different gas phase scattering of the elements. This has been qualitatively known for a long time but the results presented here now enable a quantitative estimation of such effects. For example, by taking gas phase scattering into consideration during sputtering from a WS2 target it was possible to deposit WSx films with a sulphur content going from sub-stoichiometric to over-stoichiometric composition depending on the substrate position relative the target. By alloying tungsten disulphide (WS2) with carbon and titanium (W-S-C-Ti) its hardness was significantly increased due to the formation of a new titanium carbide phase (TiCxSy). The best sample increased its hardness to 18 GPa (compared to 4 GPa for the corresponding W-S-C coating) while still maintaining a low friction (µ=0.02) due to the formation of easily sheared WS2 planes in the wear track.

Single-walled carbon nanotubes (SWNTs), with their superior combination of electrical and mechanical properties, have drawn attention from many researchers for potential applications in electronics. Many SWNT-based electronic device prototypes have been developed including transistors, interconnects and flexible electronics. In this thesis, a fabrication method for patterned SWNT networks and devices based on colloidal lithography is presented. Patterned SWNT networks are for the first time formed via solution deposition on a heterogeneous surface. This method demonstrates a simple and straight-forward way to fabricate SWNT networks in a controllable manner. Colloidal sphere monolayers were obtained by drop-casting from solution onto clean substrates. The colloidal monolayer was utilized as a mask for the fabrication of patterned SWNT networks. SWNT networks were shown to be patterned either by depositing SWNT solutions on top of a colloidal monolayer or by depositing a mixed SWNT-colloidal sphere aqueous suspension on the substrates. Colloidal monolayers were examined by optical microscopy and it was found that the monolayer quality can be affected by the concentration of colloids in solution. Polystyrene colloidal solution with concentration of 0.02 wt% ~ 0.04 wt % was found optimal for maximum coverage of colloidal monolayers on SiO2 substrates. After removing the colloidal spheres, the topology of the patterned SWNT networks was characterized by atomic force microscopy and scanning electron v microscopy. Two-dimensional ordered arrays of SWNT rings and SWNTs interconnecting the SWNT rings were observed in the resulting network structure. The height of the rings was about 4-10 nm and the diameter was about 400 nm. In some samples, mesh-like patterned SWNT networks are also observed. It is hypothesized that the capillary forces induced by Van der Waals interaction at liquid/air/solid interfaces play an important role during the formation of the patterned SWNT networks. Raman spectroscopy was also employed to identify the chirality and diameter of the SWNTs in the networks. Both metallic and semiconducting SWNTs were found in the networks and the diameter of the SWNTs was about 1 to 2 nm. The electrical properties of SWNT networks, including random SWNT networks, partially patterned SWNT networks and fully patterned SWNT networks were characterized by a probe station and a Keithley 4200 semiconductor measurement system. The random SWNT networks had two-terminal resistance varying between several MΩ to several hundred MΩ. Field effect behavior was observed in some devices with relatively high resistance and nonlinear I-V curves. Those devices had on/off ratio of less than 100. There was significant leakage current in the ―off‖ state likely due to metallic tube pathways in the networks. The partially patterned SWNT networks had resistance that varied from 20 KΩ to 10 MΩ, but did not display field effect behavior in our studies. The resistance of the patterned SWNT networks was about 10 MΩ - 100 MΩ. The electrical characteristics of the patterned SWNT networks as thin film transistors were investigated, and the on/off ratio of the devices varied from 3 to 105. The upper limit of mobility in the devices was about ~ 0.71 – 5 cm2/V·s. The subthreshold slope of patterned SWNT network FETs can be as low as 210 meV/dec. / Graduate / 0544

The primary focus of this thesis is to study the effect of doping on magnetic properties in amorphous Fe100−xZrx alloys. Samples with compositions of x = 7,11.6 and 12 at.% were implanted with different concentrations of H. Moreover, the samples with a composition of x = 7 at.% were also implanted with He, B, C and N. Magnetic measurements were performed, using SQUID magnetometry and MOKE, in order to compare the as-grown and the implanted films. The Curie temperature (Tc) increases and the coercivity (Hc) decreases, with increasing dopant volume. We also found that Hc increases with temperature for B and C doped samples. Magnetization curves at low temperature validate the presence of non-collinear spin configurations in the as-grown films, which is suppressed after doping, resulting in films with tunable soft magnetic properties. We have also studied the effect of interlayer mixing and finite size effects on FeZr in Fe92Zr8/AlZr multilayer films, and found an anomalous increase of Tc with decreasing thickness. Strain induced changes in the magnetization of an amorphous Co95Zr5 film at the orthorhombic phase transition of the BaTiO3 substrate, was also studied. The results show that structural modifications of the substrate increases the stress and hence changes the magnetic anisotropy in the amorphous Co95Zr5 layer. Finally, the magnetization reversal of Co and CoX heterostructures, with X being Cr, Fe, Ni, Pd, Pt and Ru, has been studied. For this purpose a synthetic antiferromagnet structure, FM/NM/FM, was used, where FM is a ferromagnetic Co or CoX layer and NM is a nonmagnetic Ru spacer layer. The FM layers are coupled antiferromagnetically across the NM layer. For a range of FM layer thicknesses, the exchange stiffness parameter Aex and the interlayer coupling (JRKKY ) of the Co or CoX layers were obtained. This is done by fitting M(H) curves, measured by SQUID magnetometry, to a micromagnetic model. The alloying in CoX resulted in a decreasing Aex and also a reduced MS. The experimental results are in a good agreement with DFT calculations.

High energy neutron and charged particle radiation cause microstructural and mechanical degradation in structural metals and alloys, such as phase segregation, void swelling, embrittlement and creep. Radiation induced damages typically limit nuclear materials to a lifetime of about 40 years. Next generation nuclear reactors require materials that can sustain over 60 - 80 years. Therefore it is of great significance to explore new materials with better radiation resistance, to design metals with favorable microstructures and to investigate their response to radiation. The goals of this thesis are to study the radiation responses of several nanostructured metallic thin film systems, including Ag/Ni multilayers, nanotwinned Ag and nanocrystalline Fe. Such systems obtain high volume fraction of boundaries, which are considered sinks to radiation induced defects. From the viewpoint of nanomechanics, it is of interest to investigate the plastic deformation mechanisms of nanostructured films, which typically show strong size dependence. By controlling the feature size (layer thickness, twin spacing and grain size), it is applicable to picture a deformation mechanism map which also provides prerequisite information for subsequent radiation hardening study. And from the viewpoint of radiation effects, it is of interest to explore the fundamentals of radiation response, to examine the microstructural and mechanical variations of irradiated nanometals and to enrich the design database. More importantly, with the assistance of in situ techniques, it is appealing to examine the defect generation, evolution, annihilation, absorption and interaction with internal interfaces (layer interfaces, twin boundaries and grain boundaries). Moreover, well-designed nanostructures can also verify the speculation that radiation induced defect density and hardening show clear size dependence. The focus of this thesis lies in the radiation response of Ag/Ni multilayers and nanotwinned Ag subjected to charged particles. The radiation effects in irradiated nanograined Fe are also investigated for comparison. Radiation responses in these nanostructured metallic films suggest that immiscible incoherent Ag/Ni multilayers are more resistant to radiation in comparison to their monolithic counterparts. Their mechanical properties and radiation response show strong layer thickness dependence in terms of radiation hardening and defect density. Coherent twin boundaries can interact with stacking fault tetrahedral and remove them effectively. Twin boundaries can actively absorb radiation induced defects and defect clusters resulting in boundary migration. Size dependence is also found in nanograins where fewer defects exhibit in films with smaller grains.

A novel polymer semiconductor with side chains thermally cleavable at a low temperature of 200 °C was synthesized. The complete cleavage and removal of the insulating 2-octyldodecanoyl side chains were verified with TGA, FT-IR, and NMR data. The N-H groups on the native polymer backbone are expected to form intermolecular hydrogen bonds with the C=O groups on the neighboring polymer chains to establish 3-D charge transport networks. The resulting side chain-free conjugated polymer is proven to be an active p-type semiconductor material for organic thin film transistors (OTFTs), exhibiting hole mobility of up to 0.078 cm2V-1s-1. This thermo-cleavable polymer was blended with PDQT to form films that showed a higher performance than the pure individual polymers in OTFTs. MoO3 or NPB was used as a hole injection buffer layer between the metal electrodes and the polymer semiconductor film layer in OTFT devices. This buffer layer improved hole injection, while its use in the OTFT, improved the field-effect mobility significantly due to better matched energy levels between the electrodes and the polymer semiconductor.

CdS thin films were deposited by thermal evaporation method onto glass substrates without any doping. As a result of the structural and electrical investigation it was found that CdS thin films were of the polycrystalline structure and n-type / and of the transmission analysis optical band gap was found to be around 2.4 eV. Temperature dependent conductivity measurements were carried out in the range of 180 K &ndash / 400 K. The dominant conduction mechanism is identified as tunnelling between 180 K &ndash / 230 K and thermionic emission between 270 K and 400 K. To produce Schottky devices, CdS thin films were deposited onto the tin-oxide and indium-tin-oxide coated glasses, by the same method. Gold, platinum, carbon and gold paste were used as metal front contact in these devices. The area of these contacts were about...... Temperature dependent current-voltage measurements between 200 K and 350 K, room temperature current-voltage measurements, capacitance-voltage measurement in the frequency range 1 kHz &ndash / 1 MHz and photoresponse measurements were carried out for the characterization of these diodes. Ideality factor of the produced Schottky devices were found to be at least 1.5, at room temperature. Dominant current transport mechanism in the diodes with gold contacts was determined to be tunnelling from the temperature dependent current voltage analysis. Donor concentration was calculated to be about ........ from the voltage dependent capacitance measurement.

No description available.

Emulsions and foams are thermodynamically unstable dispersions that will eventually succumb to coalescence, leading to phase separation. However the kinetic stability of emulsions and foams can vary from transiently stable systems with lifetimes of seconds to indefinitely stable systems with lifetimes of many years. Understanding and controlling emulsion and foam stability is fundamental to their widespread application in consumer products and industrial processes. Designed stimuliresponsive peptide surfactants that allow the stability of emulsions and foams to be controlled by changes in solution conditions have recently been developed at the University of Queensland. The research objective of this thesis was to establish the mechanism by which these switchable biosurfactants control emulsion and foam stability and hence contribute design rules for future generations of peptide surfactants. In particular, research focused on the control of emulsion coalescence kinetics and the fundamental insights that these peptide-based emulsions provide into the coalescence phenomena. It was proposed that these switchable peptide surfactants allow the mechanical strength of the viscoelastic surfactant layer to be decoupled from other contributions to emulsion stability. It was found that the established Derjaguin– Landau–Vervey–Overbeek (DLVO) theory, which is frequently used as the basis for predicting emulsion stability, was not able to describe the stability switching observed in the peptide-based emulsions. Different designs of peptide surfactant were used to demonstrate that the kinetics of emulsion coalescence could be shifted by changing the interfacial elasticity, clearly illustrating the critical role of the surfactant layer’s mechanical properties in the coalescence mechanism. Where the peptide-surfactant-based emulsions enabled triggering a rapid transition to coalescence from a flocculation stable system it was shown that both the electrostatic repulsion (flocculation barrier) and the interfacial elasticity (coalescence barrier) were switched. This work made use of a number of experimental techniques to study the coalescence mechanism, including the observation of droplet interactions in microfluidic channels. The switchable peptide surfactants were shown to enable triggered coalescence in droplet based microfluidics, something that had hereto with proved an intractable challenge for surfactant containing oil-in-water systems. Having established the importance of the mechanical properties of the adsorbed peptide layer in enabling control over coalescence kinetics, it was of interest to study the effect of adding other surfactant species. Mixed surfactant systems are likely to be encountered in industrial applications or commercial products. The peptide surfactant AM1 was mixed with the common anionic surfactant sodium dodecyl sulfate (SDS) and synergistic behaviour was identified, including enhanced interfacial adsorption and reversible association of structures in the bulk solution. Furthermore the interfacial layers formed by AM1-SDS retained the switchable mechanical behaviour despite considerable increases in the absolute mechanical strength.

We examine the boundary-layer flow of generalised Newtonian fluids. A specific member of this class of non-Newtonian fluids, namely the Ostwald-de Waele or power-law fluid, is studied in some detail. We show, through the numerical solution of the governing equations, that this empirical model of fluids encountered in physical and industrial situations is of limited benefit when considering the boundary-layer flow of such a fluid. We then develop and employ a Carreau viscosity model in the same context and show that the numerical marching scheme has better convergence behaviour than was the case for power-law fluids. We also investigate the boundary-layer flow of a Newtonian fluid over a thin film of non-Newtonian fluid, described by a Carreau fluid model, by focusing specifically on similarity-type solutions. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1456589 / Thesis (Ph.D.) - University of Adelaide, School of Mathematical Sciences, 2009

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.