In this paper, some critical issues and problems in the development of TiNi thin films were discussed, including preparation and characterization considerations, residual stress and adhesion, frequency improvement, fatigue and stability, as well as functionally graded or composite thin film design. Different types of MEMS applications were reviewed and the prospects for future advances in fabrication process and device development were discussed. / Singapore-MIT Alliance (SMA)

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).

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.

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.

A main driving force behind the recent years’ immense interest in nanoscience and nanotechnology is the possibility of achieving new material properties and functionalities within, e.g., material physics, biomedicine, sensor technology, chemical catalysis, energy storing systems, and so on. New (theoretical) possibilities represent, in turn, a challenging task for chemists and physicists. An important feature of the present nanoscience surge is its strongly interdisciplinary character, which is reflected in the present work. In this thesis, nanocrystals and thin films of magnetic and ferroelectric metal oxides, e.g. RE2O3 (RE = Y, Gd, Dy), GdFeO3, Gd3Fe5O12, Na0.5K0.5NbO3, have been prepared by colloidal and sol-gel methods. The sizes of the nanocrystals were in the range 3-15 nm and different carboxylic acids, e.g. oleic or citric acid, were chemisorbed onto the surface of the nanoparticles. From FT-IR measurements it is concluded that the bonding to the surface takes place via the carboxylate group in a bidentate or bridging fashion, with some preference for the latter coordination mode. The magnetic properties of nanocrystalline Gd2O3 and GdFeO3 were measured, both with respect to magnetic resonance relaxivity and magnetic susceptibility. Both types of materials exhibit promising relaxivity properties, and may have the potential for use as positive contrast enhancing agents in magnetic resonance imaging (MRI). The nanocrystalline samples were also characterised by transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and quantum chemical calculations. Thin films of Na0.5K0.5NbO3, GdFeO3 and Gd3Fe5O12 were prepared by sol-gel methods and characterized by x-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). Under appropriate synthesis conditions, rather pure phase materials could be obtained with grain sizes ranging from 50 to 300 nm. Magnetic measurements in the temperature range 2-350 K indicated that the magnetization of the perovskite phase GdFeO3 can be described as the sum of two contributing terms. One term (mainly) due to the spontaneous magnetic ordering of the iron containing sublattice, and the other a susceptibility term, attributable to the paramagnetic gadolinium sublattice. The two terms yield the relationship M(T)=M0(T)+χ(T)*H for the magnetization. The garnet phase Gd3Fe5O12 is ferrimagnetic and showed a compensation temperature Tcomp ≈ 295 K.

In this thesis the concept of inhomogeneous dielectrics is demonstrated for various optical coating applications. Compositionally-varying silicon oxynitride (SiON) dielectric layers, with the refractive index varying as a function of position, are grown by computer-controlled plasma-enhanced chemical vapor deposition (PECVD) using silane, nitrogen, and nitrous oxide reactant gases. Compositionally graded and superlattice-like SiON layers are grown and their compositional profiles are confirmed by Auger electron spectroscopy sputter profiling. Inhomogeneous antireflection coatings and rugate filters, with sinusoidally varying refractive index profiles, are designed and fabricated and their measured spectral responses are found to be in excellent agreement with simulated results. Alternating-current thin film electroluminescent (ACTFEL) devices with multiple layer dielectrics also are designed, fabricated, and the insulating layers are shown to increase the optical outcoupling efficiency of an ACTFEL devices by approximately 14 % compared to that of a conventional ACTFEL structure. / Graduation date: 1993