Metallic ferromagnetic (FM) thin film heterostructures play an important role in emerging magnetoelectronic devices, which introduce the spin degree of freedom of electrons into conventional charge-based electronic devices. As the majority of magnetoelectronic devices operate in the GHz frequency range, it is critical to understand the high-frequency magnetization dynamics in these structures. In this thesis, we start with the static magnetic properties of FM thin films and their optimization via the field-sputtering process incorporating a specially designed in-situ electromagnet. We focus on the origins of anisotropy and hysteresis/coercivity in soft magnetic thin films, which are most relevant to magentic susceptibility and power dissipation in applications in the sub-GHz frequency regime, such as magnetic-core integrated inductors. Next we explore GHz magnetization dynamics in thin-film heterostructures, both in semi-infinite samples and confined geometries. All investigations are rooted in the Landau-Lifshitz-Gilbert (LLG) equation, the equation of motion for magnetization. The phenomenological Gilbert damping parameter in the LLG equation has been interpreted, since the 1970's, in terms of the electrical resistivity. We present the first interpretation of the size effect in Gilbert damping in single metallic FM films based on this electron theory of damping. The LLG equation is intrinsically nonlinear, which provides possibilities for rf signal processing. We analyze the frequency doubling effect at small-angle magnetization precession from the first-order expansion of the LLG equation, and demonstrate second harmonic generation from Ni81 Fe19 (Permalloy) thin film under ferromagnetic resonance (FMR), three orders of magnitude more efficient than in ferrites traditionally used in rf devices. Though the efficiency is less than in semiconductor devices, we provide field- and frequency-selectivity in the second harmonic generation. To address further the relationship between the rf excitation and the magnetization dynamics in systems with higher complexity, such as multilayered thin films consisting of nonmagnetic (NM) and FM layers, we employ the powerful time-resolved x-ray magnetic circular dichroism (TR-XMCD) spectroscopy. Soft x-rays have element-specific absorption, leading to layer-specific magnetization detection provided the FM layers have distinctive compositions. We discovered that in contrast to what has been routinely assumed, for layer thicknesses well below the skin depth of the EM wave, a significant phase difference exists between the rf magnetic fields Hrf in different FM layers separated by a Cu spacer layer. We propose an analysis based on the distribution of the EM waves in the film stack and substrate to interpret this striking observation. For confined geometries with lateral dimensions in the sub-micron regime, there has been a critical absence of experimental techniques which can image small-amplitude dynamics of these structures. We extend the TR-XMCD technique to scanning transmission x-ray microscopy (STXM), to observe directly the local magnetization dynamics in nanoscale FM thin-film elements, demonstrated at picosecond temporal, 40 nm spatial and less than 6° angular resolution. The experimental data are compared with our micromagnetic simulations based on the finite element analysis of the time-dependent LLG equation. We resolve standing spin wave modes in nanoscale Ni81 Fe19 thin film ellipses (1000 nm × 500 nm × 20 nm) with clear phase information to distinguish between degenerate eigenmodes with different symmetries for the first time. With the element-specific imaging capability of soft x-rays, spatial resolution up to 15 nm with improved optics, we see great potential for this technique to investigate functional devices with multiple FM layers, and provide insight into the studies of spin injection, manipulation and detection.

The lack of an energetic model for the seemingly spontaneous room temperature recrystallization of electroplated copper thin films has proven to be a technological bottleneck in the optimization of copper interconnect microstructure for the microelectronics industry. The inability to either achieve large grained interconnect microstructures by simple annealing or explain them by a posteriori analyses necessitates a new approach. Synchrotron x-ray diffraction was utilized to obtain real-time grain size, crystallographic texture, and strain data about the recrystallization in the geometrically simpler case of blanket electroplated Cu films. The observation of a bimodal size distribution between as- deposited and recrystallizing grains during led to the development of a theoretical framework for combining x-ray data and the canonical Johnson-Mehl-Avrami-Kolmogorov (JMAK) kinetics model. Under this framework, analysis of variations in plated Cu film and vapor deposited underlayer structures established that film recrystallization speed is a function of initial 111 film texture, and that this dependency is modulated by underlayer deposition conditions and plated film thickness. Verification of the new x-ray analysis was performed by combined use of complementary destructive and non-destructive characterization techniques which are more commonly accessible in the industrial setting. These included cross-sectional focused ion beam milling and scanning electron microscopy (x-FIB/SEM), electron back scatter diffraction (EBSD), and four-point probe electrical resistivity measurements. Comparative real-time in situ x-ray and resistivity studies revealed the formation of electron percolation paths which prematurely short-circuited the latter analysis. An effective resistivity model is proposedto extend the current canonical one-dimensional analysis to be compatible with multi-dimensional recrystallization. X-ray analysis of plated films whose initial stress state had been modified by delamination or the photoresist masking of substrate stresses revealed a significant change to the recrystallization kinetics. Complementary real-time EBSD analysis localized the initiation of recrystallization to the free surface of the film. The combination of this with quantitative activation energy measurements was then the basis for a comprehensive theoretical energetics model.

The new complex materials have wide applications in next generation technologies in industrial fields such as electronics, energy production, environment engineering, etc. Understanding their structure is the key in keeping developing new materials and improving their performance. As they are more and more complex in different length scale, new methods that utilize information from different sources and be able to provide complex structural information are on the horizon of this new era. In this thesis, we developed new methods that process the mixed data and provide the extra information that people are interested in. First one is extending the computed tomography technique with other analysis method including texture analysis and Pair Distribution Function (PDF) method. The new methods enable us to study the coupling of desired structural properties, such as texture and local local structure of nano-particles, at meso-scale. For example, by applying the texture-CT analysis on the LiCoO₂ coin cell, we found the texture of LiCoO₂ particles was quite inhomogeneous. By combining PDF and CT method, we successfully studied the catalyst reaction and the participle size distribution in industrial catalyst. Second one is a new method of obtaining reliable anomalous differential Pair Distribution Function (adPDF) by using diffraction data sets in wide energy range and an ad-hoc algorithm that perform the data correction automatically. The new method was demonstrated using both simulated data and real experimental data.

Supramolecular ionic assemblies not only provide alternatives to conventional polymers, but also introduce unique and interesting functions for the design of "smart" polymeric assemblies for use in a number of fields due to their programmable and reversible properties. Research in the area has led to an understanding of the connection between molecular contributions and macroscopic properties, as well as a range of applications from material processing/manufacuturing to energy transfer and storage. To this end, we have developed a library of charged building blocks based on ionic liquids to create functional supramolecular ionic assemblies. The polymeric ionic assemblies prepared from a di-phosphonium and poly (acrylic acid) were first studied and found to have the potential to be utilized as "smart" materials due to their ability to reversibly respond to stimuli such as temperature and pressure. With the interest of elucidating the molecular contributions to the bulk macroscopic material properties, six supramolecular assemblies were sequentially characterized in terms of thermal, rheological and X-ray studies. The effect of side alkyl chain was found to dramatically change the material properties. A second type of supramolecular assembly was investigated based on a poly-phosphonium ionic liquid, which was complexed with a number of carboxylic acids. The material properties were easily manipulated from a sticky fiber to a brittle solid by changing the composition of the carboxylic acid. A crosslinked supramolecular assembly combining ionic interactions and weak covalent bonds, specifically disulfide bonds, was next designed and characterized. The network properties could be switched between "on and off" using mild conditions. The polymeric ionic networks and their building block ionic liquids are also of interest as safe electrolytes in energy storage devices due to their non-flammability, non-volatility, etc. We have identified one ionic liquid with superior thermal stability, high lithium salt solubility, and good conductivity in a lithium metal battery. The prototype battery performed safely at 100 degree celsius for more than 30 days. Thermally stable Li metal batteries are of interest in the oil industry for downhole applications. These studies were extended to an ionic polymer that exhibits a lamellar structure as a new polymer electrolyte.

Wong Yuk Hong = 一維納米結構材料製造與特性量測 / 王旭航. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 53-56). / Text in English; abstracts in English and Chinese. / Wong Yuk Hong = Yi wei na mi jie gou cai liao zhi zao yu te xing liang ce / Wang Xuhang. / Title --- p.i / Abstract --- p.ii / 摘要 --- p.iii / Acknowledgement --- p.iv / Tables of contents --- p.v / List of figures --- p.vii / List of table --- p.x / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Background --- p.4 / Chapter 2.1 --- Major mechanisms of fabricating various one-dimensional nano structures --- p.4 / Chapter 2.2 --- Previous work on fabrication of nanocable and nanobelt --- p.6 / Chapter Chapter 3 --- Instrumentation --- p.9 / Chapter 3.1 --- High temperature furnace --- p.9 / Chapter 3.2 --- X-ray diffractometry --- p.11 / Chapter 3.3 --- Scanning electron microscopy --- p.12 / Chapter 3.4 --- Energy dispersive X-ray spectrometry --- p.13 / Chapter 3.5 --- Cathodoluminescence spectroscopy --- p.14 / Chapter 3.6 --- Transmission electron microscopy --- p.14 / Chapter 3.6.1 --- Diffraction mode --- p.15 / Chapter 3.6.2 --- Imaging mode --- p.15 / Chapter 3.6.3 --- High-resolution transmission electron microscopy --- p.18 / Chapter Chapter 4 --- Zn/ZnO nanocable heterostructures --- p.19 / Chapter 4.1 --- General experimental --- p.19 / Chapter 4.2 --- Results --- p.21 / Chapter 4.3 --- Discussions --- p.31 / Chapter 4.4 --- Conclusion --- p.39 / Chapter Chapter 5 --- "Morphology, microstructure and optical properties of CdS nanobelts" --- p.41 / Chapter 5.1 --- General experimental --- p.41 / Chapter 5.2 --- Results and discussions --- p.41 / Chapter 5.3 --- Conclusion --- p.50 / Chapter Chapter 6 --- Conclusion --- p.52 / References --- p.53

Nanometer scale structures represent an exciting and rapidly expanding area of research. Studies on new physical/chemical properties and applications of nanomaterials and nanostructures are possible only when nanostructured materials are made available with desired size, morphology, crystal and microstructure, and composition. Thus, controlled synthesis of nanomaterials is the essential aspect of nanotechnology. This thesis describes the development of simple and versatile solution-based approaches to synthesize low-dimensional nanostructures. / The first major goal of this research is to design and fabricate morphology-controlled alpha-Fe 2O3 nanoarchitectures in aqueous solution through a programmed microwave-assisted hydrothermal route, taking advantage of microwave irradiation and hydrothermal effects. Free-standing alpha-Fe2O3 nanorings are prepared by hydrolysis of FeCl3 in the presence of phosphate ions. The as-formed architecture of alpha-Fe2O 3 nanorings is an exciting new member in the family of iron oxide nanostructures. Our preliminary results demonstrate that sensors made of the alpha-Fe 2O3 nanorings exhibit high sensitivity not only for bio-sensing of hydrogen peroxide in a physiological solution but also for gas-sensing of alcohol vapor at room temperature. Moreover, monodisperse alpha-Fe 2O3 nanocrystals with continuous aspect-ratio tuning and fine shape control are achieved by controlling the experimental conditions. The as-formed alpha-Fe2O3 exhibits shape-dependent infrared optical properties. The growth process of colloidal alpha-Fe 2O3 crystals in the presence of phosphate ions is discussed. In addition, through an efficient microwave-assisted hydrothermal process, self-assembled hierarchical alpha-Fe2O3 nanoarchitectures are synthesized on a large scale. / The second major goal of this research is to develop convenient microwave-hydrothermal approaches for the fabrication of carbon-based nanocomposites: (1) A one-pot solution-phase route, namely microwave-assisted hydrothermal reduction/carbonization (MAHRC), is developed to prepare coaxial Ag/amorphous-carbon (a-C) nanocables. The as-grown Ag/C nanocables can self-assemble in an end-to-end fashion. (2) A novel Se/C nanocomposite with core-shell structures is prepared. The new material consists of a trigonal-Se (t-Se) core and an amorphous-C (a-C) shell. The Se/C composite can be converted to hollow carbon capsules by thermal treatment. (3) A Fe 3O4/C nanocomposite is synthesized by a green wet-chemical approach. The product possesses porous microstructures and exhibits superparamagnetic behavior. / The third major goal of this research is develop facile solution-based methods for preparing carbonaceous nano test tubes, thin films of metal iodides, and spherical selenium spheres: (1) Carbonaceous nano test tubes are fabricated by a facile "decoring" route using a core-sheath Te carbon nanocomposite as the precursor. The as-formed carbonaceous material looks like a "test tube" with an average diameter of about 120 nm and lengths up to 5 mum. (2) Tetrahedral-shaped CuI crystals were formed on a variety of copper substrates (e.g. grids, flat/porous foils, and macro-/nano- wires) via an interfacial reaction between a copper substrate and iodine in water at room temperature. This preparation approach can also be used to grow PbI2 and AgI nano- and micro-crystals with different morphologies on corresponding substrates. (3) Colloidal trigonal selenium (t-Se) microspheres are synthesized through a mild hydrothermal reduction reaction, using glucose as a reducing regent and water as an environmentally friendly solvent. Importantly, the resulting t-Se microspheres inherit functional groups from the starting materials and possess hydrophilic and biocompatible surfaces. / Hu, Xianluo. / "July 2007." / Adviser: Jimmy C. Yu. / Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0602. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

by Woo Yick Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 188-191). / by Woo Yick Fai. / Chapter i. --- Abstract --- p.i / Chapter ii. --- Acknowledgment --- p.ii / Chapter 0. --- Introduction --- p.1 / Chapter 1. --- Effects of nonlinear impurity in a diatomic chain --- p.3 / Chapter 1.1 --- Introduction --- p.3 / Chapter 1.2 --- Formulation --- p.9 / Chapter 1.3 --- Results --- p.16 / Chapter 1.4 --- Discussion --- p.28 / Chapter 2. --- Single nonlinear impurity in a diatomic plane --- p.30 / Chapter 2.1 --- Introduction --- p.30 / Chapter 2.2 --- Formulation --- p.34 / Chapter 2.3 --- Results --- p.39 / Chapter 2.4 --- Discussion --- p.43 / Chapter 3. --- Effects of a nonlinear impurity in a diatomic cube --- p.46 / Chapter 3.1 --- Introduction --- p.46 / Chapter 3.2 --- Formulation --- p.50 / Chapter 3.3 --- Results --- p.54 / Chapter 3.4 --- Discussion --- p.58 / Chapter 4. --- Effective response in random mixtures of linear and nonlinear conductors --- p.60 / Chapter 4.1 --- Introduction --- p.60 / Chapter 4.2 --- Formalism of our proposed theory --- p.67 / Chapter 4.3 --- Results --- p.68 / Chapter 4.4 --- Effective response in random mixture of strongly nonlinear composites --- p.74 / Chapter 5. --- 1D traffic models --- p.77 / Chapter 5.1 --- Introduction to Cellular Automata models for traffic flow --- p.77 / Chapter 5.2 --- Inhomogeneous 1D traffic models --- p.89 / Chapter 6. --- 2D traffic models --- p.102 / Chapter 6.1 --- Isotropic traffic systems --- p.102 / Chapter 6.2 --- Anisotropic traffic systems --- p.117 / Chapter 7. --- Inhomogeneities in the 2D traffic models --- p.127 / Chapter 7.1 --- Systems with faulty traffic lights --- p.127 / Chapter 7.2 --- Systems with over-passes --- p.144 / Chapter 7.3 --- Traffic models with two-time scales --- p.154 / Chapter 7.4 --- Traffic models with acceleration --- p.159 / Appendix --- p.164 / Appendix A Effects of a nonlinear impurity in a diatomic chain --- p.165 / Appendix B Effective response in random mixtures of linear and nonlinear conductors --- p.175 / Appendix C Upper bounds for the critical car densities in traffic flow problems --- p.180 / Appendix D Improved mean-field theory of two-dimensional traffic flow models --- p.183 / Bibliography --- p.188

By virtue of their non-toxic nature and their attractive photoluminescence (PL) properties, Carbon-dots (or C-dots) represent an emerging class of environmentally benign multifunctional materials. They exhibit excitation-dependent emission and demonstrate colloidal and structural stability. As a result, C-dots are promising candidates for a wide spectrum of applications.

The Kassandra mining district in Chalkidiki is an important producer of base and precious metals in northern Greece. The mining district is comprised of two major Pb-Zn (Ag [plus or minus] Au) carbonate-replacement deposits at Olympias and Mavres Petres with total mineable reserves of 0.7 Mt Pb, 0.9 Mt Zn, 64 Moz Ag and 4.1 Moz Au. Skouries is a Cu-Au porphyry resource under development with reserves of 3.6 Moz Au and 0.8 Mt Cu. Despite available data, the geodynamic background of the polymetallic district mineralisation is unknown in the context of regional tectono-magmatic evolution. The scope of this PhD project was to develop an over arching ore-genetic model for the diverse mineralisation styles in the Kassandra mining district. The polymetallic zonation and spatial distribution of diverse mineralisation styles in the study area is characteristic for an intrusion-centred ore system. Subeconomic to economically important Cu-Au porphyry copper, Cu-skarn, Pb-Zn (Ag [plus or minus] Au) carbonate-replacement and basement-hosted Fe-Pb ([plus or minus] As) sub-epithermal vein mineralisation between Olympias, Mavres Petres, Madem Lakkos, Stratoni-Fisoka and Skouries represent the proximal to distal parts of a fault-controlled magmatic-hydrothermal system. Fluid inclusion and stable isotope data provided by previous authors identified magmatic and evolved meteoric-hydrothermal fluids in the mineralisation system. New He and S stable isotope data support the involvement of a magmatic component as important metallogenic source for metals, ligands, fluids and heat. Spatially and genetically related to the mineralisation are Oligocene-Miocene stocks and dykes of granite, granodiorite diorite, diorite-gabbro and subordinate gabbro. U-Pb zircon and [sup]40Ar-[sup]39Ar mica ages constrain the mineralisation-related calc-alkaline, medium-K to shoshonitic magmatism to a short-lived cycle between 29 Ma and 20 Ma. A late Oligocene [sup]187Re-[sup]187Os isochron age of 26.1 [plus or minus] 5.3 Ma for ore-related arsenopyrite from the Olympias deposits provides a robust in-situ formation age for the carbonate-replacement mineralisation in the district. Two [sup]40Ar-[sup]39Ar biotite ages of 26.3 [plus or minus] 0.3 Ma and 19.9 [plus or minus] 0.2 Ma date the porphyry-style mineralisation-alteration at Stratoni-Fisoka and the economically important Skouries Cu-Au porphyry resource. Magmatism and magmatic-hydrothermal mineralisation in the district were coeval with a phase of post-collisional extension in the North Aegean region. Eocene-Miocene slab roll-back initiated orogen-scale lithospheric stretching, crustal thinning and asthenospheric upwelling which elevated the regional heat gradient. Heat transmission into lower structural levels of the Rhodope nappe pile started and maintained hydrothermal fluid circulation which led to the formation of base metal rich-deposits. Metamorphic and protolith ages of host and country rocks allocate the district mineralisation to the middle to upper tectono-stratigraphic crustal levels. Here, on the flank of the Southern Rhodope core complex, the heat flux was not high enough to initiate large-scale fluid flow. Instead, synetensional partial melting at mid to lower crustal levels, involving fertile and hydrous cumulates in the subduction-modified sub-continental lithospheric mantle, generated hydrous melts with subduction-type chemical signatures that were emplaced in the Kassandra mining district in the magmatic arc above the retreating slab.

abstract: Collective cell migration in the 3D fibrous extracellular matrix (ECM) is crucial to many physiological and pathological processes such as tissue regeneration, immune response and cancer progression. A migrating cell also generates active pulling forces, which are transmitted to the ECM fibers via focal adhesion complexes. Such active forces consistently remodel the local ECM (e.g., by re-orienting the collagen fibers, forming fiber bundles and increasing the local stiffness of ECM), leading to a dynamically evolving force network in the system that in turn regulates the collective migration of cells. In this work, this novel mechanotaxis mechanism is investigated, i.e., the role of the ECM mediated active cellular force propagation in coordinating collective cell migration via computational modeling and simulations. The work mainly includes two components: (i) microstructure and micromechanics modeling of cellularized ECM (collagen) networks and (ii) modeling collective cell migration and self-organization in 3D ECM. For ECM modeling, a procedure for generating realizations of highly heterogeneous 3D collagen networks with prescribed microstructural statistics via stochastic optimization is devised. Analysis shows that oriented fibers can significantly enhance long-range force transmission in the network. For modeling collective migratory behaviors of the cells, a minimal active-particle-on-network (APN) model is developed, in which reveals a dynamic transition in the system as the particle number density ρ increases beyond a critical value ρc, from an absorbing state in which the particles segregate into small isolated stationary clusters, to a dynamic state in which the majority of the particles join in a single large cluster undergone constant dynamic reorganization. The results, which are consistent with independent experimental results, suggest a robust mechanism based on ECM-mediated mechanical coupling for collective cell behaviors in 3D ECM. For the future plan, further substantiate the minimal cell migration model by incorporating more detailed cell-ECM interactions and relevant sub-cellular mechanisms is needed, as well as further investigation of the effects of fiber alignment, ECM mechanical properties and externally applied mechanical cues on collective migration dynamics. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2019