Computation model is presented for mass spring systems of one and two dimensional phononic band gap crystals and micro-electro-mechanical systems. The computation model is veri ed with existing work, and phononic band gap microelectro- mechanical systems are analyzed. Phononic band gap in the scienti c and industrial community is discussed. The motivation and the recent popular methods are discussed. The computation models are highlighted with their pros and cons and adequate computational applications. The one dimensional mass spring model is developed and the simulator operation is validated through comparison with the published simulation data in the original paper by J.S. Jensen et al.. Additionally, the one dimensional mass spring simulator is validated for a micro-electro-mechanical system band structure. The two dimensional mass spring model is developed, as well, the simulator operation is validated through comparison with the published simulation data in the original paper by J.S. Jensen et al.. The two-dimensional simulator is utilized to analyze solid square-shaped, hollow square-shaped, solid diamond-shaped, and hollow diamond-shaped inclusion micro-electro-mechanical band gap structures. The solid inclusion-based micro-electro-mechanical band gap results are compared with hollow inclusion-based micro-electro-mechanical structures.

The atomic layer deposition (ALD) growth of titania thin films was studied for the infiltration of silica photonic crystals. Titania thin films were grown in a custom-built ALD reactor by the alternating pulsing and purging of TiCl4 and water vapor. The conformal nature of ALD growth makes it an ideal candidate for the infiltration of the complex opal structure. Titania is a high refractive index material, which makes it a popular material for use in photonic crystal (PC) applications. Photonic crystals are periodic dielectric structures that forbid the propagation of light in a certain wavelength range. This forbidden range is known as the photonic band gap (PBG). A refractive index contrast of at least 2.8 is required for a complete PBG in an inverted opal structure. Therefore, the rutile structure of titania is more desirable for use in PCs due to its higher index of refraction than the anatase or brookite structure. The growth mechanisms and film properties of the TiO2 thin films were studied. Investigation of the growth mechanisms revealed saturated growth rate conditions for multiple temperature regions. Film characterization techniques included XRD, SEM/EDS, XPS, AFM, reflectivity, and index of refraction measurements. Post growth heat treatment was performed to study the conversion from the as-deposited crystal structure to the rutile structure. After optimization of the deposition process, the infiltration of silica opals for PC applications was attempted. The filling fraction was optimized by increasing the pulse and purge lengths at a deposition temperature of 100oC. Although the silica opals were successfully infiltrated using ALD of TiO2, the long range order of the PC was destroyed after the heat treatment step required to achieve the high index rutile structure.

Since the discovery of the photovoltaic effect in bulk heterojunction devices¡Mthe considerable publications in PSCs have been reported¡OPSCs based on the concept of bulk heterojunction (BHJ) configuration where active layer comprises of a p-type donor (conjugated polymer) and a n-type acceptor (fullerene derivative) materials¡Mrepresents the most useful strategy to maximize the internal donor-acceptor interface area allowing for efficient charge separation¡OTo further enhance the power conversion efficiency from solar cells made of poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric acid methyl ester (P3HT/PCBM) ¡M a new conducting polymer with optimized band energy levels are demonstrated to be one of the key properties¡OIn this study¡MI synthesized a soluble and strongly visible-light absorbing alternating conducting polymer using Suzuki coupling polymerization method¡OThe UV-Vis absorption spectra of copolymer contains an intramolecular charge transfer (ICT) transition band¡Mwhich leads to absorption extending to near-infrared region and optical band gaps is 1.55 eV¡OThe photo-electron spectroscopy in air(PESA) measurements show that the HOMO level of the polymer is ~5.0eV which is lower than P3HT¡O

A rigorous power coupling model for three-core optical waveguides is proposed based on a full-wave vector boundary element method (VBEM). In addition to the influence of the state of the polarization (SOP) of the input light on the coupling behavior of the three-core optical waveguides can be simulated, the polarization dependent loss (PDL) of the three-core optical waveguides can also be investigated by combining the Mueller matrix method into the power coupling model. In this dissertation, the power coupling model is applied to investigate two kinds of power splitters. The first power splitters are constructed of step-index single mode fibers called triangular 3 3 fused tapered couplers. The influence of the SOP of the input light on the coupling behavior of the triangular 3 3 fused tapered couplers and the effect of fabricating parameters of the coupler, fusion degree, and heated length on the PDL of the coupler are investigated in this dissertation. The second kind of power splitters are constructed of photonic crystal fibers (PCFs). And, several fundamental coupling properties of three-core photonic crystal fibers (PCFs) with equilateral triangular cores are investigated numerically included coupling length, bandwidth, and polarization dependent loss (PDL). It is found the three-core PCFs are good candidate to be realized as an ultra-compact power splitter. And, for three-core PCFs that chose a proper coupling point can raise the yield and performance stability of the power splitter. In addition to the coupling behavior of the power splitters, two-dimensional photonic crystals (PCs) are also studied in this dissertation based on finite-difference time-domain (FDTD) method. The phase interference phenomenon due to the multiple plane-wave signals as initial conditions of the FDTD method for computing band structure of two-dimensional PCs is studied in this dissertation. It is found some normal modes supposed to exist could be lost if the phase interference is nearly out of phase at eigenfrequency. To overcome this problem, we proposed a new solving procedure based on FDTD algorithm which can avoid mode loss phenomenon and obtain complete normal modes over interested frequency range.

Photonic crystal fibers (PCFs) are divided into two different kinds of fibers. The first one, index-guiding PCF, guides light by total internal reflection between a solid core and a cladding region with multiple air-holes. On the other hand, the second one uses a perfectly periodic structure exhibiting a photonic band-gap (PBG) effect at the operating wavelength to guide light in a low index core-region. A compact 2D-FDTD method based on finite-difference time-domain method is formulated and is effectively applied to analysis PCFs and PBGFs. We study the propagation features of fundamental mode and the fundamental characteristics such as effective index, modal-field diameter and chromatic dispersion in index-guiding PCFs. By optimizing the air-hole diameters and the hole-to-hole spacing of index-guiding PCFs, both the dispersion and the dispersion slope can be controlled in a wide wavelength range. We also investigate the propagation features of fundamental mode and band-gap effect of PBGFs.

A new class of &amp / #960 / -conjugated monomers was synthesized with combination of electron donating and electron-withdrawing heterocyclics to understand the effects of structural differences on electrochemical and optoelectronic properties of the resulting polymers. The use of this alternating donor-acceptor-donor strategy allows the synthesis of low band gap polymers in which the redox, electronic, and optical properties are controlled through easily approachable synthetic modification of the polymer backbone. This control allows fine-tuning of the band gap to values between 1.0 and 1.8 eV by making structural changes. These structural manipulations yield varied electronic absorption energies for a range of colors in the neutral polymer films, multi-colored electrochromism, and accessible states for reduction leading to n-type doping. The polymers prepared were characterized using cyclic voltammetry, colorimetry, and UV-Vis-NIR spectroscopy demonstrating that the polymers can undergo both p- and n-type doping and color changes in both redox states.

In conventional design of power delivery networks (PDNs), the PDN impedance is required to be less than the target impedance over the frequency range of interest to minimize the IR drop and to suppress the inductive noise during data transitions. As a result, most PDNs in high-speed systems consist of power and ground planes to provide a low-impedance path between the voltage regulator module (VRM) and the integrated circuit (IC) on the printed circuit board (PCB). For off-chip signaling, charging and discharging signal transmission lines induce return currents on the power and ground planes. The return current always follows the path of least impedance on the reference plane closest to the signal transmission line. The return current path plays a critical role in maintaining the signal integrity of the bits propagating on the signal transmission lines. The problem is that the disruption between the power and ground planes induces return path discontinuities (RPDs), which create displacement current sources between the power and ground planes. The current sources excite the plane cavity and cause voltage fluctuations. These fluctuations are proportional to the plane impedance since the current is drawn through the PDN by the driver. Therefore, low PDN impedance is required for power supply noise reduction. Alternatively, methods of preventing RPDs can be used to suppress power supply noise. Using a power transmission line (PTL) eliminates the discontinuity between the power and ground planes, thereby preventing the RPD effects. In this approach, transmission lines replace the power plane for conveying power from the VRM to each IC on the PCB. The PTL-based PDN enables both power and signal transmission lines to be referenced to the same ground plane so that a continuous current path can be formed, unlike the power-plane-based PDN. As a result, a closed current loop is achieved, and the voltage fluctuation caused by RPDs is removed in idealistic situations. Without the RPD-related voltage fluctuation, reducing the PDN impedance is not as critical as in the power-plane-based approach. Instead, the impedance of the PTL is determined by the impedance of the signaling circuits. To use the PTL-based PDN in a practical signaling environment, several issues need to be solved. First, the dc drop coming from the source termination of the PTL needs to be addressed. The driver being turned on and off dictates the current flow through the PTL, causing the dc drop to be dynamic, which depends on the data pattern. Second, impedance mismatch between the PTL and termination can occur due to manufacturing variations. Third, an increase in the number of PCB traces should be addressed by devising a method to feed more than one driver with one PTL. Lastly, the power required to transmit 1 bit of data should be optimized for the PTL by using a new signaling scheme and adjusting the impedance of the signaling circuit. Constant flow of current through the PDN is one solution proposed to address the first two issues. Constant current removes the dynamic characteristics of the dc drop by inducing a fixed amount of dc drop over the PTL. Moreover, constant current keeps the PTL fully charged at all times, and thereby eliminates the process of repeatedly charging and discharging the power transmission line. The constant current PTL (CCPTL) scheme maintains constant current flow regardless of the input data pattern. Early results on the CCPTL scheme have been discussed along with the measurements. The CCPTL scheme severs the link between the current flowing through the PTL and the output data of the I/O driver connected to it. Also, it eliminates the charging and discharging process of the PTL, thereby completely eliminating power supply noise in idealistic situations. To reduce any associated power penalty, a pseudo-balanced PTL (PBPTL) scheme is also proposed using the PTL concept. A pseudo-balanced (PB) signaling scheme, which uses an encoding technique to map N-bit data onto M-bit encoded data with fixed number of 1s and 0s, is applied. When the PB signaling scheme is combined with the PTL, the jitter performance improves significantly as compared to currently practiced design approach.

Bloch analysis was originally developed by Felix Bloch to solve Schrödinger's equation for the electron wave function in a periodic potential field, such as that found in a pristine crystalline solid. His method has since been adapted to study elastic wave propagation in periodic structures. The absence of a rigorous mathematical analysis of the approach, as applied to periodic structures, has resulted in mistreatment of internal forces and misapplication to nonlinear media. In this thesis, we detail a mathematical basis for Bloch analysis and thereby shed important light on the proper application of the technique. We show conclusively that translational invariance is not a proper justification for invoking the existence of a "propagation constant," and that in nonlinear media this results in a flawed analysis. Next, we propose a general framework for applying Bloch analysis in damped systems and investigate the effect of damping on dispersion curves. In the context of Schrödinger's equation, damping is absent and energy is conserved. In the damped setting, application of Bloch analysis is not straight-forward and requires additional considerations in order to obtain valid results. Results are presented in which the approach is applied to example structures. These results reveal that damping may introduce wavenumber band gaps and bending of dispersion curves such that two or more temporal frequencies exist for each dispersion curve and wavenumber. We close the thesis by deriving conditions which predict the number of wavevectors at each frequency in a dispersion relation. This has important implications for the number of nearest neighbor interactions that must be included in a model in order to obtain dispersion predictions which match experiment.

The chromogenic properties of tungsten trioxide (WO3) have been studied by photoluminescence spectroscopy at 4.2 K in order to characterize the electronic structure of this material and see how this relates to optical responses during chromogenic coloration. Transition processes between electron energy states are often the cause of optical phenomena and it is important to identify such processes in order to understand the chromogenic coloration of tungsten oxide films. Much research work has been devoted to characterize the physical and chemical mechanisms that are responsible for this coloration and this is of fundamental importance to understand the chromogenic behavior. The latest research shows that oxygen vacancies could play an important role in certain coloration processes, but it is still a matter of debate whether these are important for the overall response. This work aims to identify specific transitions that are related to oxygen vacancies by measuring photoluminescence from films with controlled vacancy content. The main goal of the project was to set up an experiment that could measure photoluminescence at liquid helium temperature. This was done by installing and integrating the components included in this experimental set-up. The films had been prepared prior to this work and were deposited on a nanocrystalline CaF2 substrate, which is a material that has a very large band gap and was therefore expected to fully transparent in the UV range. However it was found that the substrate inelastically scattered the UV excitation light, which produced strong signals that overshadowed the photoluminescence and prevented an effective characterization of the electronic structure in the films. Instead, suggestions were given on how to minimize uncertainty factors and overcome the difficulties met in this work. It was also found that the films attain a lasting blue coloration by exposure to UV light in vacuum, and that this might be due to oxygen being desorbed from the film during experiments in vacuum.

Graphene, the first two-dimensional crystal ever found, is a material that has attracted fervent and sustained interest from condensed matter researchers from around the world. It has a unique and unprecedented band structure in a bulk material: the bands near the Fermi level are linear, leading to massless charge carriers that propagate at the speed of light. However, graphene does not possess a band gap, and as such, it cannot be used to process information in any electronic device that uses digital logic. Graphene is oxidized when several different basic functional groups like hydroxyls, carboxyls, and epoxides bond to the hexagonal carbon basal plane to make graphene oxide (GO). The result is a nonstoichiometric and highly disordered system that, according to the results shown in this thesis, consists of zones of densely-packed functional groups interspersed between zones of relatively small functional group concentration. This has been confirmed by DFT calculations presented here, which is the first time that a successful simulation of the GO density of states has been compared to X-ray data. Contrary to many assumptions in the literature, many of the features in the density of states of GO are due not to carbon sites bonded to functional groups, but are due to nearby non-functionalized carbon sites. The band gap of graphene oxide is principally controlled by oxidation level. Reduction, followed by heating, will regenerate the near-Fermi states and close the band gap significantly as has been seen by others. However, heating non-reduced graphene oxide can also result in a much-reduced band gap, which occurs because intercalated water can react with the heated GO sample to remove functional groups by creation and eventual expulsion of carbon dioxide. The band gap of GO is further complicated by stacking effects if it is multilayered, because residual pi-conjugated states in neighboring planes interact. The two major types of stacking in graphite are AA-stacking and AB-stacking. AA-stacking interactions cause the pi * resonance to broaden and push states to lower energy, which means that AA-stacking determines the width of the gap in highly oxidized samples. However, direct oxidation of graphene is not the only way that one alter the electronic structure of GO. Other results presented here also show that non-covalent functionalization of graphene oxide by amorphous solid water is a powerful, reversible way to dramatically change the GO electronic structure.