LiCoO₂thin films have been grown by pulsed laser deposition on stainless steel and SiO₂/Si substrates. The film deposited at 600°C in an oxygen partial pressure of 100mTorr shows an excellent crystallinity, stoichiometry and no impurity phase present. Microstructure and surface morphology of thin films were examined using a scanning electron microscope. The electrochemical properties of the thin films were studied with cyclic voltammetry and galvanostatic charge-discharge techniques in the potential range 3.0-4.2 V. The initial discharge capacity of the LiCoO2 thin films deposited on the stainless steel and SiO₂/Si substrates reached 23 and 27 µAh/cm², respectively. / Singapore-MIT Alliance (SMA)

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 189-197).

Part I - We have designed a binary metallic alloy for nanoscale resonator applications. We used magnetron sputtering to deposit films with different stoichiometries of aluminum and molybdenum and then characterized the microstructure and physical properties of each film. A structure zone map is proposed to describe the dependence of surface and bulk structure on composition. We then fabricated proof of principle resonators from the Al-32 at%Mo composition, selected for its optimized physical properties. An optical interferometer was used to characterize the frequency response of our resonators. Part II - We investigate the growth of faceted polycrystalline thin films with modeling and simulations. A new analytic model is derived for the case of orientation dependent facet growth velocity and the dependence of growth on initial grain orientations is explicitly calculated. Level set simulations were used to both confirm this analytic model and extend it to include various angular flux distributions, corresponding to different deposition methods. From these simulations, the effects of self-shadowing on polycrystalline film growth are quantitatively evaluated. / Materials Engineering

Advanced optical technologies profoundly impact countless aspects of modern life. At the heart of these technologies is the manipulation of light using optical materials. Currently, optical technologies are created using naturally occurring materials. However, a new and exciting approach is to use nanomaterials for technology development. Nanomaterials are artificially constructed material systems with precisely engineered nanostructures. Many technological revolutions await the development of new nanoscale fabrication methods that must provide the ability to control, enhance, and engineer the optical properties of these artificial constructs. This thesis responds to the challenges of nanofabrication by examining glancing angle deposition (GLAD) and improving its optical-nanomaterial fabrication capabilities. GLAD is a bottom-up nanotechnology fabrication method, recognized for its flexibility and precision. The GLAD technique provides the ability to controllably fabricate high-surface-area porous materials, to create structurally induced optical-anisotropy in isotropic materials, and to tailor the refractive index of a single material. These three advantages allow GLAD to assemble optical nanomaterials into a range of complex one-dimensional photonic crystals (PCs). This thesis improves upon previous GLAD optical results in a number of important areas. Multiple optical measurement and modeling techniques were developed for GLAD-fabricated TiO2 nanomaterials. The successful characterization of these nanomaterials was extended to engineer PC structures with great precision and a superior degree of control. The high surface area of basic PC structures was exploited to fabricate an optimized colourimetric sensor with excellent performance. This colourimetric sensor required no power source and no read-out system other than the human eye, making it a highly attractive sensing approach. Incorporating engineered defects into GLAD-fabricated PCs established a new level of design sophistication. Several PC defect structures were examined in detail, including spacing layers and index profile phase-shifts. Remarkable control over defect properties was achieved and intriguing polarization-sensitive optical effects were investigated in anisotropic defect layers. The success of these results demonstrates the precision and flexibilty of the GLAD technique in fabricating optical nanomaterials and advanced photonic devices. / Micro-Electro-Mechanical Systems (MEMS) and Nanosystems

This thesis investigates technologies directed towards developing photonic crystal display devices. A switching technology based on dye electrophoretic motion within a 1D porous photonic crystal was developed. Dissociated absorbing dye species were moved through the assembled device and reflectance was controllably altered by up to 0.4. Refinement of fabrication techniques yielded a slow switching device, whose time-resolved reflectance data was analyzed. A wavelength dependence of the device switching speed was observed. This phenomenon was described by modelling where bandgap effects match observation. These devices may be improved by employing a 3D photonic crystal. We developed a nanoimprint lithography technique for seeding films deposited by GLAD for the fabrication of 3D square spiral photonic crystals. Parameters for patterning a precisely defined mould pattern using electron beam lithography were established. A large area diamond:1 square spiral photonic crystal was fabricated on the nanoimprinted seeds, and it exhibited a visible wavelength bandgap. / Micro-Electro-Mechanical Systems (MEMS) and Nanosystems

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 156-167).

Thesis (M.Phil.)--City University of Hong Kong, 2006. / "Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Master of Philosophy" Includes bibliographical references.

No description available.

This dissertation is focused on understanding heterogeneous metal catalysts supported on oxides using a model catalyst system of SiO2 thin film supported metal nano-clusters. The primary technique applied to this study is scanning tunneling microscopy (STM). The most important constituent of this model catalyst system is the SiO2 thin film, as it must be thin and homogeneous enough to apply electron or ion based surface science techniques as well as STM. Ultra-thin SiO2 films were successfully synthesized on a Mo(112) single crystal. The electronic and geometric structure of the SiO2 thin film was investigated by STM combined with LEED, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The relationship between defects on the SiO2 thin film and the nucleation and growth of metal nano-clusters was also investigated. By monitoring morphology changes during thermal annealing, it was found that the metal-support interaction is strongly dependent on the type of metal as well as on the defect density of the SiO2 thin film. Especially, it was found that oxygen vacancies and Si impurities play an important role in the formation of Pd-silicide. By substituting Ti atoms into the SiO2 thin film network, an atomically mixed TiO2-SiO2 thin film was synthesized. Furthermore, these Ti atoms play a role as heterogeneous defects, resulting in the creation of nucleation sites for Au nano-clusters. A marked increase in Au cluster density due to Ti defects was observed in STM. A TiO2-SiO2 thin film consisting of atomic Ti as well as TiOx islands was also synthesized by using higher amounts of Ti (17 %). More importantly, this oxide surface was found to have sinter resistant properties for Au nano-clusters, which are desirable in order to make highly active Au nano-clusters more stable under reaction conditions.

Conductive thin films of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT-PSS) were created via layer-by-layer assembly. The PEDOT-PSS was used in an aqueous solution as an anionic polyelectrolyte, with both linear and branched polyethylenimine (PEI) and poly(allylamine hydrochloride) (PAH) in the positive aqueous solution. The electrical conductivity was varied by altering pH, concentration, polyelectrolyte, and doping the PEDOT with dimethylsulfoxide (DMSO). The most conductive 12BL samples were doped with 1wt% DMSO and have a sheet resistance of approximately 8kΩ/□. Despite exhibiting good initial conductivity, these PEDOT based thin films degrade under ultraviolet (UV) exposure. UV absorbing nanoparticles were added into the cationic solution in an effort to reduce UV sensitivity. The final bilayers of the films contained either colloidal titanium dioxide (TiO2) or carbon black (CB) and the films were exposed to a 365nm UV-light with an intensity of 2.16mW/cm2 for 9 days. The UV light at this intensity correlates to approximately four years of sunlight. The initial sheet resistances for all samples were similar, but the UV-degradation was reduced by a factor of 5 by utilizing TiO2 and CB in the final bilayers. In addition to being the most conductive after UV exposure, the TiO2 containing film was also 27% more optically transparent than the pure PEDOT films. These additional UV-absorbing nanoparticles extend the operational life of the PEDOT films and, in the case of TiO2, do so without any reduced transparency.