Polymer electrolytes are the most obvious candidates for safe "all-solid" Li-ion batteries and other electrochemical devices. However, they still have relatively poor ionic conductivities, which limits their wider adoption in commercial applications. It has earlier been the conventional wisdom that only amorphous phases of polymer electrolytes show usefully high ionic conduction, while crystalline forms are insulators. However, this has been challenged in the last decade by the discovery of highly organized, low-dimensional ion-conducting materials. Specifically, the crystalline phases of LiXF6.PEO6 exhibit higher ionic conductivities than their amorphous counterparts, with the Li-ion conduction taking place along the PEO channels. Polymer chain-length and chain-end registry has emerged as potentially significant in determining ionic conduction in these materials. Molecular Dynamics simulations have therefore been made of short-chain, monodisperse (Mw~1000), methoxy end-capped LiPF6.PEO6 to examine relationships between ion conduction and mode of chain-ordering. Studies of smectic and nematic arrangements of PEO chains have revealed that ion-transport mechanisms within the smectic planes formed by cooperative chain-end registry appear to be more suppressed by ion-pairing than in-channel conduction. Disorder phenomena in the chain-end regions emerge as a critical factor in promoting Li-ion migration across chain-gaps, as does the structural continuity of the PEO channels. Simulations incorporating ~1% aliovalent SiF62- dopants further suggest an increase in Li-ion conduction when the extra Li-ions reside within the PEO channels, with the anion influencing charge-carrier concentration through enhanced ion-pair formation. XRD techniques alone are shown to be inadequate in ascertaining the significance of the various short-chain models proposed; atomistic modelling is clearly a helpful complement in distinguishing more or less favourable situations for ion conduction. Though providing valuable insights, it must be concluded that this work has hardly brought us significantly closer to breakthroughs in polymer electrolyte design; the critical factors which will make this possible remain as yet obscure.

Zinc xanthates are active catalysts in stereoregular polymerization of propylene oxide and markedly more stable than that of known classical stereoregular catalysts. But steric control of zinc xanthates is weaker. To find more effective catalyst systems the isopropyl xanthates of Cu, Pb, Ni, Fe, Al and Sn are investigated and only copper (Cu(isoPr)Xt) and tin (Sn(isoPr)Xt) isopropyl xanthates were appeared to be active, but Cu(isoPr)Xt yielded only low molecular weight product. Therefore Sn(isoPr)Xt system was investigated in detail in polymerization of propylene oxide (PO). Polymerization of PO with this catalyst produced two contrasting polymers / high molar mass, crystalline (K-polymer) and low molar mass (D-polymer). Formation of double bonds in D-polymer was thought to be due to as an anionic process. Polymerization reactions were studied by changing polymerization conditions and reacting catalyst with predetermined amount of water. It&amp / #8217 / s found that Sn(isoPr)Xt have considerably low efficiency than that of Zn(isoPr)Xt catalyst. The yield linearly increases by increasing catalyst concentration. The propagation is competed by termination or transfer process hence overall activation energy is negative. Some mechanistic features of this system was also discussed. The catalytical activity of carbamates in this field has also been reported, without any information about catalytical efficiency and stereoregularity of the process. Therefore zinc diethyl dithiocarbamate was also studied and found as an active catalyst in stereoregular polymerization but it showed weaker efficiency in the PO polymerization than that of Zn(isoPr)Xt catalyst (about 12 times weaker).

In this thesis study, fabrication and doping of silicon thin films prepared by electron beam evaporation equipped with effusion cells for solar cell applications have been investigated. Thin film amorphous Si (a-Si) layers have been fabricated by the electron beam evaporator and simultaneously doped with boron (B) and phosphorous (P) using effusion cells. Samples were prepared on glass substrates for the future solar cell operations. Following the deposition of a-Si thin film, crystallization of the films has been carried out. Solid Phase Crystallization (SPC) and Metal Induced Crystallization (MIC) have been employed to obtain thin film crystalline Si. Crystallization was performed in a conventional tube furnaces and Rapid Thermal annealing systems (RTA) as a function of process parameters such as annealing temperature and duration. Produced films have been characterized using chemical and structural characterization techniques such as Raman Spectroscopy, X-Ray Diffractometer and Secondary Ion Mass Spectrometer (SIMS). The electrical properties of the films have been studied using Hall Effect and I-V measurements as a function of doping. We have demonstrated successful crystallization of a-Si by SPC at temperatures above 600 &deg / C. The crystallization occurred at lower temperatures in the case of MIC. For doping, P was evaporated from the effusion cell at a temperature between 600 &deg / C and 800 &deg / C. For B, the evaporation temperature was 1700 &deg / C and 1900 &deg / C. The thickness and the band gap of the Si films were determined by ellipsometry method and the results were compared for different evaporation temperatures. The effect of doping was monitored by the I-V and Hall Effect measurements. We have seen that the doping was accomplished in most of the cases. For the samples annealed at relatively high temperatures, the measured doping type was inconsistent with the expected results. This was attributed to the contamination from the glass substrate. To understand the origin of this contamination, we analyzed the chemical structure of the film and glass by X-ray Fluorescence (XRF) and seen that the glass is the main source of contamination. In order to prevent this contamination we have suggested covering the glass substrate with Si3N4 (Silicon Nitride) which act as a good diffusion barrier for impurities.

An alternative approach to energy integrating systems is photon counting which provides higher dose efficiency through efficient noise rejection and optimal energy weighting, and, moreover, is not susceptible to memory artifacts such as image lag and ghosting. The first large-area photon counting imager was Charpak's Nobel Prize winning invention of the gas-filled multiwire proportional chamber (MWPC), which revolutionized the field of radiation detection in 1968. In most applications, however, the use of a solid detection medium is preferable because solid densities are about three orders-of-magnitude greater than gas, and thus, they can yield much smaller detector dimensions with unsurpassed spatial and temporal resolution. Thus far, crystalline Cadmium Zinc Telluride is the only room-temperature solid-state detector that meets the requirements for photon counting imaging. However, the material is grown in small ingots and production costs are high for large-area imaging applications. The problem is that disordered (or non-crystalline) solids, which are easier and less expensive to develop over large-area than single crystalline solids, have been ruled out as viable photon counting detectors because of their poor temporal resolution, or more specifically, extremely low carrier mobilities and transit-time-limited photoresponse. To circumvent the problem of poor charge transport in disordered solids with a conventional planar detector structure, we propose unipolar charge sensing by establishing a strong near-field effect using an electrostatic shield within the material. We introduce the concept of time-differential photoresponse in unipolar solids and show that their temporal resolution can be improved substantially to reach the intrinsic physical limit set by spatial dispersion. Inspired by Charpak's MWPC and its variants, and for the first time, we have implemented an electrostatic shield inside evaporated amorphous selenium (a-Se) using the proposed lithography-based microstrip solid-state detector (MSSD). The fabricated devices are characterized with optical, x-ray, and gamma-ray impulse-like excitations. Using optical time-of-flight (TOF) measurements, we show for the first time a unipolar Gaussian TOF transient from the new MSSD structure, instead of a rectangular response with a Gaussian-integral at the tail which is a typical response of a conventional planar device. The measured optical and x-ray TOF results verify the time-differential property of the electrostatic shield and the practicality of the dispersion-limited photoresponse. Furthermore, we use single gamma-ray photon excitations to probe detector's temporal resolution in pulse mode for photon counting. For the MSSD, we show a depth-independent signal for photon absorption across the bulk and a reduction in signal risetime by a factor of 350, comparing performance limiting factors being hole-dispersion for the MSSD and electron-transit-time for the conventional planar device. The time-differential response obtained from the proposed unipolar detector structure enables disordered photoconductive films to become viable candidates for large-area photon counting applications.

The integration of mixed-signal systems has long been a problem in the semiconductor industry. CMOS System-on-Chip (SOC), the traditional means for integration, fails mixed-signal systems on two fronts; the lack of on-chip passives with high quality (Q) factors inhibits the design of completely integrated wireless circuits, and the noise coupling from digital to analog circuitry through the conductive silicon substrate degrades the performance of the analog circuits. Advancements in semiconductor packaging have resulted in a second option for integration, the System-On-Package (SOP) approach. Unlike SOC where the package exists just for the thermal and mechanical protection of the ICs, SOP provides for an increase in the functionality of the IC package by supporting multiple chips and embedded passives. However, integration at the package level also comes with its set of hurdles, with significant research required in areas like design of circuits using embedded passives and isolation of noise between analog and digital sub-systems. A novel multiband balun topology has been developed, providing concurrent operation at multiple frequency bands. The design of compact wideband baluns has been proposed as an extension of this theory. As proof-of-concept devices, both singleband and wideband baluns have been fabricated on Liquid Crystalline Polymer (LCP) based organic substrates. A novel passive-Q based optimization methodology has been developed for chip-package co-design of CMOS Low Noise Amplifiers (LNA). To implement these LNAs in a mixed-signal environment, a novel Electromagnetic Band Gap (EBG) based isolation scheme has also been employed. The key contributions of this work are thus the development of novel RF circuit topologies utilizing embedded passives, and an advancement in the understanding and suppression of signal coupling mechanisms in mixed-signal SOP-based systems. The former will result in compact and highly integrated solutions for RF front-ends, while the latter is expected to have a significant impact in the integration of these communication devices with high performance computing.

The goal of the research in this dissertation is to design and characterize embedded passive components, interconnects, and circuits in inhomogeneous, multi-layer liquid crystalline polymer (LCP) substrates. The attenuation properties of inhomogeneous multi-layer LCP substrates were extracted up to 40 GHz. This is the first result for an inhomogeneous LCP stack-up that has been reported. The characterization results show excellent loss characteristics, much better than FR-4-based technology, and they are similar to LTCC and homogeneous LCP-based technology. A two-port characterization method based on measurements of multiple arrays of vias is proposed. The method overcomes the drawbacks of the one-port and other two-port characterizations. Model-to-hardware correlation was verified using multi-layer model in Agilent ADS and measurement-based via model using arrays of the vias. The resulting correlations show that this method can be readily applied to other vertical interconnect structures besides via structures. Comprehensive characterizations have been conducted for the efficient 3D integration of high-Q passives using a balanced LCP substrate. At two different locations from three different large M-LCP panels, 76 inductors and 16 3D capacitors were designed and measured. The parameters for the measurement-based inductor model were extracted from the measured results. The results validate the large panel process of the M-LCP substrate. To reduce the lateral size, multi-layer 3D capacitors were designed. The designed 3D capacitors with inductors can provide optimized solutions for more efficient RF front-end module integration. In addition, the parameters for the measurement-based capacitor model were extracted. Various RF front-end modules have been designed and implemented using high-Q embedded passive components in inhomogeneous multi-layer LCP substrates. A C-band filter using lumped elements has been designed and measured. The lumped baluns were used to design a double balnced-mixer for 5 GHz WLAN application and a doubly double-balanced mixer for 1.78 GHz CDMA receiver miniaturization. Finally, to overcome the limitations of the lumped component circuits, a 30 GHz gap-coupled band-pass filter in inhomogeneous multi-layer LCP substrates, and the measured results using SOLT and TRL calibrations have been compared to the simulation results.

The monomer, p-acryloyloxybenzoic acid (ABA) was synthesized by condensation reaction of acryloyl chloride and p-hydroxybenzoic acid in alkaline medium. Polymerization of the monomer and grafting of the produced polymer (PABA) onto high density polyethylene (HDPE) were expected to be carried simultaneously in melt mixing at high temperature. The graft copolymerization was studied at varying concentrations of the monomer in the reaction mixture at constant temperature (200 0C). Grafted HDPE samples were investigated by several techniques such as DSC, FTIR, MFI and mechanical testing. The tensile tests of PABA-g-HDPE showed an improvement particularly in stress at yield and Young&rsquo / s modulus whereas the strain at break values showed a decrease for all compositions compared to neat HDPE.

The objective of this study is to synthesize nematic-thermotropic liquid crystalline polymers (LCP) and determine their possible application areas. In this context, thirty different LCP&rsquo / s were synthesized and categorized with respect to their fiber formation capacity, melting temperature and mechanical properties. The basic chemical structure of synthesized LCP&rsquo / s were composed of p-acetoxybenzoic acid (p-ABA), m-acetoxybenzoic acid (m-ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA) and isophthalic acid (IPA) and alkyl-diacids monomers. In addition to mentioned monomers, polymers and oligomers were included in the backbone such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) polymers, and polybutylene naphthalate (PBN), polyhexylene naphthalate (PHN) and poly butylene terephthalate (PBT) oligomers that contain different kinds of alkyl-diols. We adjusted the LCP content to have low melting point (180oC-280oC) that is processable with thermoplastics. This was achieved by balancing the amount of linear (para) and angular (meta) groups on the aromatic backbones together with the use of linear hydrocarbon linkages in the random copolymerization (esterification) reaction. LCP species were characterized by the following techniques / Polarized Light Microscopy, Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Analysis (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), X-ray Scattering (WAXS, Fiber diffraction), surface free energy, end group analysis (CEG), intrinsic viscosity (IV) and tensile test. According to these analysis LCPs were classified into five main categories / (I) fully aromatics, (II) aromatics+ PET/PEN, (III) aromatics + oligomers (IV) aromatics + short aliphatic diacids, (V) aromatics + long aliphatic diacids. The foremost results of the analysis can be given as below. DSC analysis shows that some LCPs are materials that have stable LC mesogens under polarized light microscopy. In TGA analysis LCPs that have film formation capacity passed the thermal stability test up to 390oC. NMR results proved that predicted structures of LCPs from feed charged to the reactor are correct. In FTIR due to the inclusion of new moieties, several peaks were labeled in the finger-print range that belongs to reactants. In X-ray analysis, LCP24 (containing PET) was found to be more crystalline than LCP25 (containing PEN) which is due to the symmetrical configuration. Block segments were more pronounced in wholly aromatic LCP2 than LCP24 that has flexible spacers. Another important finding is that, as the amount of the charge to the reactor increases CEG value increases and molecular weight of the product decreases. Selected group V species were employed as reinforcing agent and mixed with the thermoplastics / acrylonitrile butadiene styrene (ABS), nylon6 (PA6), polyethylene terephthalate (PET), polypropylene (PP) and appropriate compatibilizers in micro compounder and twin screw extruder. The blends of them were tested in dog-bone and/or fiber form. In general LCPs do not improve the mechanical properties except in composite application with polypropylene. A significant increase in tensile properties is observed by LCP24 and LCP25 usage. Capillary rheometer studies show that the viscosity of ABS decreases with the inclusion PA6 and LCP2 together. In addition to the composite applications, some LCPs are promising with new usage areas. Such as nano fibers with 200nm diameter were obtained from LCP27 by electrospinning method. The high dielectric constant of LCP29 has shown that it may have application areas in capacitors.

Different monomeric diols, with a central rigid FD unit connected with two aliphatic chains of various length, were prepared to react with aromatic mesogenic triad, TOBC. In this manner, thermotropic polyesters with possible low thermal transition temperatures (including Tmand Ti) and high solubility in organic solvent can be generated in view of the non-linear polymeric chain imposed by the rigid, bent FD moieties. In addition to the effect of the aliphatic chain length, polyesters of different molecular weight will be obtained by different synthesis approach (or fractionation of the resulting polyester product) and therefore, the influence of molecular weight on liquid crystalline properties can be evaluated.

No description available.