The rise of organometal halide perovskite materials with extremely intriguing properties have opened a new horizon in the design of high speed and low price optoelectronic devices. The bandgap in the crystalline structure of these materials can be easily tuned for various applications and their dominant non-excitonic dynamics eliminate the requirement of a bulk or heterostructure for charge carrier separation. These unique properties increase the photo-sensitivity of perovskite-based optoelectronics and provide them with a low time constant, resulting in high precision fast devices. Realization of perovskite-based devices translates directly to inexpensive and simplified architectures of optoelectronic systems. In perovskite-based devices, costly silicon or wide bandgap semiconductor fabrication technology is largely replaced by solution processable methods. Their bandgap tunability allows the reduction of the required optical accessories and interconnects in optoelectronic components. For instance, a tuned perovskite-based detector can substitute a narrowband detecting system consisting of a conventional detector and its required optical accessories such as lenses and color filters. These properties of perovskite-based devices lead to the realization of inexpensive, low power and high-performance optoelectronic systems. In this work, the design of a narrowband, low noise, high performance and stable photodetector based on organic-inorganic hybrid perovskite structure is proposed. The full width at half maximum (FWHM) of the device would be in the nanometer range. The response of the device can be tuned using either different ratios of the lead salts or synthetic dyes (macromolecules) in the crystalline structure for color discrimination in machine vision and imaging applications. Non-excitonic photocarrier generation, tunability of the optical bandgap and low voltage requirements for charge carrier generation are the keys to the utility of this optoelectronic device. The goals of this project were to identify the required functional materials (lead salts and synthetic dyes based on their molecular structures) and optimize their performance; the study of their effect on the charge collection narrowing mechanism and bandwidth specifications defined for detectivity, linear dynamic range (LDR) and photoresponse speed. To achieve these goals, it was proposed to study the light detection properties as well as spectroscopic and semiconductor parameter characteristics of fabricated devices. The design considerations of such devices are versatile and may be modulated for different applications.

Congenital diaphragmatic hernia (CDH) results from a defect in the diaphragm through which abdominal contents enter the thorax displacing the heart and the lungs. This causes lung hypoplasia and varying degrees of pulmonary hypertension resulting in high rates of morbidity and mortality. Though CDH has a prevalence rate of 2.61 per 10,000 live births it is an expensive birth defect with an estimated annual cost of nearly $250 million for all CDH survivors. Maternal exposure to air pollutants have not been studied as risk factors for CDH in humans. Ambient ozone has been found to be risk factors for certain birth defects including congenital heart defects, chromosomal anomalies, and limb reduction defects. Cadmium, however, has been found to be a risk factor for diaphragmatic hernia, cleft palate, renal defects, anopthalmia, microphthalmia, anal atresia, undescended testes, and dysplastic ears in animal studies only. The objectives of this study were to: 1) examine the prevalence, temporal trends, and correlates of CDH among live-born infants during 1998–2012; 2) investigate the association between sociodemographic and perinatal characteristics and neonatal and one-year survival among infants with CDH and its subtypes, isolated and complex; 3) examine the role of ambient ozone as a risk factor for CDH; and 4) determine the association between maternal exposure to ambient cadmium in air and CDH and assess if maternal smoking during pregnancy is an effect modifier of the cadmium-CDH association. To answer these questions we used a population-based, retrospective cohort study using data from the 1998–2012 Florida Birth Defects Registry. We classified CDH cases into isolated and complex. A case that was associated with other anomalies listed on the National Birth Defects Prevention Network list of major structural reportable defects was classified as complex CDH. We used Poisson and joinpoint regression models to compute prevalence ratios and assess temporal trends, respectively. Kaplan-Meier survival curves and Cox proportional hazards regression were used to describe neonatal and one-year survival and estimate hazard ratios of neonatal and one-year mortality. We then used multilevel Poisson regression models to examine the association between maternal exposure to ambient ozone and CDH as well as cadmium and CDH. We conducted stratified analyses to test for effect measure modification by maternal smoking status. The study population to answer the first two questions consisted of 3,209,775 live-born infants (including 1,025 cases). To answer the third and fourth questions, the study population consisted of 3,039,685 and 2,591,395 live-born infants (including 981 and 840 cases), respectively. We found a 4% increase in the annual prevalence of CDH among complex cases, but no trend for isolated cases. We observed higher prevalence of CDH among infants born to mothers with high school or less maternal education and for multiple births. Female sex and maternal obesity were found to be associated with decreased risk for CDH. The most important predictor of neonatal and one-year mortality was gestational age

La prévention contre la corrosion est un facteur déterminant pour la durabilité des matériaux. Historiquement, le développement des applications des matériaux avancés n'est pas envisageable sans une approche scientifique poussée des mécanismes fondamentaux qui conduisent à la dégradation en service. L'histoire humaine a été ponctuée par les progrès technologiques, qui ont tous été permis par les progrès de la science des matériaux, de l'âge du fer à l'âge de silicium. Par exemple, c'est la fusion du minerai qui a fait basculer l'humanité de l'âge de pierre aux premiers alliages (bronze) et la fondation ultérieure d'une société basée sur les métaux. Ces métaux retournent à l'état naturel en suivant des lois thermodynamiques et cinétiques. l'objet de la thèse vise à comprendre le comportement de certains matériaux dits passivables pour tenter de proposer des lois de comportement à partir du modèle du défaut ponctuel. Cette approche s'appuie sur des caractérisations électrochimique et physico-chimique des matériaux métalliques considérés. / Corrosion control is an important facet of durable and responsible engineering. Historically, the development of advanced materials applications stymied without sufficient scientific understanding of the fundamental mechanisms that dominate degradation in the system of application. Human history has been punctuated by advances in technology, all of which were enabled by advances in materials science, from the iron age to the silicon age. For instance, it was the invention of smelting ores that brought humanity out of the stone age, leading to the first alloys (bronze) and the subsequent foundation of a metals based society. During the infancy of the planet earth, around four billion years ago, the first photosynthesizers began converting carbon dioxide into oxygen. However, oxygen gas was not released into the atmosphere in great quantities because it was immediately bound up with dissolved metals in the ocean; mostly iron, forming a large fraction of the iron ores we rely upon. Producing such metals from oxides formed during the previous four billion years involves flying in the face of the thermodynamic desire to return to the oxide state.

Perovskite-type oxides show irrefutable potential for feasible thermochemical solar-driven CO2 conversion. These materials exhibit the exact characteristics required by the low temperature reverse water-gas shift chemical looping process. These properties include structural endurance and high oxygen redox capacity, which results in the formation of numerous oxygen vacancies, or active sites for CO2 conversion. A major drawback is the decrease in oxygen self-diffusion with increasing perovskite particle size. In this study, the La0.75Sr0.25FeO3 (LSF) perovskite oxide was combined with various supports including popular redox materials CeO2 and ZrO2 along with more abundant alternatives such as Al2O3, SiO2, and TiO2, in view of its potential application at industrial scale. Supporting LSF on SiO2 by 25% mass resulted in the largest increase of 150% in CO yields after reduction at 600 °C. This result was a repercussion of significantly reduced perovskite particle size confirmed by SEM/TEM imaging and Scherrer analyses of XRD patterns. Minor secondary phases were observed during the solid-state reactions at the interface of SiO2 and TiO2. Density functional theory-based calculations, coupled with experiments, revealed oxygen vacancy formation only on the perovskite phase at these low temperatures of 600 °C. The role of each metal oxide support towards suppressing or enhancing the CO2 conversion has been elucidated. Through utilization of SiO2, the reverse water-gas shift chemical looping process using perovskite-based composites was significantly improved.

In the first study, superconducting 2D NbSe₂ was examined towards its prototypical demonstration as a transition-edge sensor, where photoexcitation caused a thermodynamic phase transition in NbSe₂ from the superconducting state to the normal state. The efficacy of the optical absorption was found to depend on the wavelength of the incoming radiation used, which ranged from the ultra-violet (405 nm), visible (660 nm), to the infrared (1060 nm). In the second case involving WSe₂, the UV-ozone treatment revealed the presence of localized excitonic emission in 1L WSe₂ that was robust and long-lived. Our third material platform dealt with hybrid 0D-2D ensembles based on graphene and WSe₂, specifically graphene–endohedral, WSe₂–fullerene (C₆₀), and WSe₂–Au nanoparticles, and exhibited exceptional performance gains achieved with both types of hybrid structures. Next, we investigated WSe₂ based mixed dimensional hybrids. Temperature T-dependent and wavelength λ-dependent optoelectronic transport measurements showed a shift in the spectral response of 1L WSe₂ towards the SPR peak locations of Au-Sp and Au-BP, fostered through the plexciton interactions. Models for the plexcitonic interactions are proposed that provide a framework for explaining the photoexcited hot charge carrier injection from AuNPs to WSe₂ and its influence on the carrier dynamics in these hybrid systems. Last, we studied interactions of vdWs hybrid structures composed of WSe₂ with 0D buckminsterfullerene (C₆₀) spheres. Our results indicate that the C₆₀-WSe₂ vdWs hybrid heterostructure appears to be an attractive architecture for enabling charge transfer and high performance photodetection capabilities. T-dependent electrical transport measurements after C₆₀ deposition revealed a dominant p-type conduction behavior and a significant ×10³ increase in WSe₂ field-effect mobility, with a maximum field-effect mobility of 281 cm²V⁻¹s⁻¹ achieved at 350 K and room-T mobility of 119.9 cm²V⁻¹s⁻¹ for the C₆₀-WSe₂ hybrid.

Titanium dioxide, TiO2, has potential applications as a photoelectrode for photoelectrochemical generation of hydrogen by splitting water using solar energy and as a photocatalyst for water purification. This study is part of the UNSW research program to process TiO2-based oxide semiconductors as high-performance photoelectrodes and photocatalysts. This study investigates the effect of defect disorder on semiconducting properties of polycrystalline TiO2. This study involved the processing of high-purity polycrystalline TiO2 and determination of its semiconducting properties through measurement of electrical conductivity and thermoelectric power at elevated temperatures (1073-1323K) in controlled oxygen activities [1x10-13 Pa < p(O2) < 75 kPa]. The study included two types of experiments: Determination of electrical properties under conditions of gas/solid equilibrium. The data obtained was used to derive defect disorder and related semiconducting properties Monitoring of electrical properties during equilibration. This data was used to determine the chemical diffusion coefficient. The data obtained under equilibrium conditions indicates that oxygen may be used as a dopant to impose controlled semiconducting properties. In reduced conditions TiO2 is an n-type semiconductor and under oxidizing conditions TiO2 is a p-type semiconductor. The n-type behaviour is associated with oxygen vacancies as the predominant defects and titanium interstitials as the minority defects. The p-type behaviour is closely related to titanium vacancies that are formed during prolonged oxidation. Charge transport at elevated temperature was shown to involve substantial contribution from ions. Analysis of electrical properties enabled determination of several defect-related quantities including the activation enthalpy for oxygen vacancy formation, and the activation energy of the electrical conductivity components related to electrons, holes and ions. The kinetic data obtained during gas/solid equilibration enabled determination of the chemical diffusion coefficient which exhibited a complex dependence on nonstoichiometry. In addition, prolonged oxidation showed that equilibration occurred in two kinetic regimes. One for highly mobile oxygen vacancies and titanium interstitials which quickly reached an ??operational equilibrium?? within hours and another slow kinetic regime for equilibration of titanium vacancies over many thousand hours. The determined chemical diffusion coefficient data may be used to select the processing conditions required to impose uniform concentration of defects within a TiO2.

<p>Spin filtering properties of novel GaNAs alloys are reported in this thesis. Spin-dependent recombination (SDR) in GaNAs via a deep paramagnetic defect center is intensively studied.  By using the optical orientation photoluminescence (PL) technique, GaNAs is shown to be able to spin filter electrons injected from GaAs, which is a useful functional property for integratition with future electronic devices.  The spin filtering ability is found to degrade in narrow GaNAs quantum well (QW) structures which is attributed to (i) acceleration of band-to-band recombination competing with the SDR process and to (ii) faster electron spin relaxation in the narrow QWs.  Ga interstitial-related defect centers have been found to be responsible for the SDR process by using the optically detected magnetic resonance (ODMR) technique. The defects are found to be the dominant grown-in defects in GaNAs, commonly formed during both MBE and MOCVD growths.  Methods to control the concentration of the Ga interstitials by varying doping, growth parameters and post-growth treatments are also examined.</p>

<p>NXP Semiconductors (formerly Philips Semiconductors) has created a new embedded asynchronous FIFO module. It is a small and fast full-custom design with Design-for-Test (DfT) functionality. The fault detection qualities of a proposed manufacturing test for this FIFO have been analyzed by a defect-based method based on analog simulation. Resistive bridges and opens of different sizes in the bit-cell matrix and in the asynchronous control have been investigated.</p><p>The fault coverage for bridge defects in the bit-cell matrix of the initial FIFO test has been improved by inclusion of an additional data background and low-voltage testing. 100% fault coverage is reached for low resistance bridges. The fault coverage for opens has been improved by a new test procedure including waiting periods.</p><p>98.4% of the hard bridge defects in the asynchronous control slices can be detected with some modifications of the initial test.</p>

Mechanical waves provide information about the stiffness and the condition of a medium; thus, changes in medium conditions can be inferred from changes in wave velocity and attenuation. Non-destructive testing (NDT) methods based on ultrasonic waves are often more economical, practical and faster than destructive testing. Multichannel analysis of surface waves (MASW) is a well-established surface wave method used for determination of the shear-wave profile of layered medium. The MASW test configuration is also applicable to assess the condition of concrete elements using appropriate frequency range. Both attenuation and dispersion of ultrasonic waves can be evaluated by this technique. In ultrasonic testing, the characterization of a medium requires the precise measurement of its response to ultrasonic pulses to infer the presence of defects and boundary conditions. However, any ultrasonic transducer attached to a surface affects the measured response; especially at high frequencies. On the other hand, ultrasonic transducers available for engineering application are mostly used to measure wave velocities (travel time method). Therefore, these transducers do not have a flat response in the required frequency range. Moreover, in the case of full-waveform methods, the recorded signals should be normalized with respect to the transfer functions of the transducers to obtain the real response of the tested specimen. The main objective of this research is to establish a comprehensive methodology based on surface wave characteristics (velocity, attenuation and dispersion) for condition assessment of cemented materials with irregular defects. To achieve the major objective, the MASW test configuration is implemented in the ultrasonic frequency range. The measured signals are subjected to various signal processing techniques to extract accurate information. In addition, a calibration procedure is conducted to determine the frequency response functions (FRF) of the piezoelectric accelerometers outside their nominal frequency range. This calibration is performed using a high-frequency laser vibrometer. This research includes three main studies. The first study introduces the calibration approach to measure the FRFs of the accelerometers outside of their flat frequency range. The calibrated accelerometers are then used to perform MASW tests on a cemented-sand medium. The original signals and the corrected ones by eliminating the effect of the FRFs are used to determine material damping of the medium. Although, the damping ratios obtained from different accelerometers are not same, the values from the corrected signals are found closer to the characteristic damping value compared to those from the uncorrected signals. The second study investigates the sensitivity of Rayleigh wave velocity, attenuation coefficient, material damping and dispersion in phase velocity to evaluate the sensitivity of these characteristics to the damage quantity in a medium. The soft cemented-sand medium is preferred as the test specimen so that well-defined shaped defects could be created in the medium. MASW test configuration is implemented on the medium for different cases of defect depth. The recorded signals are processed using different signal processing techniques including Fourier and wavelet transforms and empirical mode decomposition to determine the surface wave characteristics accurately. A new index, ‘dispersion index’, is introduced which quantifies the defect based on the dispersive behaviour. All surface wave characteristics are found capable of reflecting the damage quantity of the test medium at different sensitivity levels. In the final study, the condition assessment of six lab-scale concrete beams with different void percent is performed. The beam specimens involving Styrofoam pellets with different ratios are tested under ultrasonic and mechanical equipment. The assessment produce established in the second study with well-defined defects is pursed for the beams with irregular defects. Among the characteristics, attenuation, P and R-wave velocities and dispersion index are found as the promising characteristics for quantifying the defect volume.

Academia and industry expend much effort to predict software defects. Researchers proposed many defect prediction algorithms and metrics. While previous defect prediction techniques often take the author of the code into consideration, none of these techniques build a separate prediction model for each developer. Different developers have different coding styles, commit frequencies, and experience levels, which would result in different defect patterns. When the defects of different developers are combined, such differences are obscured, hurting the prediction performance. This thesis proposes two techniques to improve defect prediction performance: personalized defect prediction and confidence-based hybrid defect prediction. Personalized defect prediction builds a separate prediction model for each developer to predict software defects. Confidence-based hybrid defect prediction combines different models by picking the prediction from the model with the highest confidence. As a proof of concept, we apply the two techniques to classify defects at the file change level. We implement the state-of-the-art change classification as the baseline and compare with the personalized defect prediction approach. Confidence-based defect prediction combines these two models. We evaluate on six large and popular software projects written in C and Java—the Linux kernel, PostgreSQL, Xorg, Eclipse, Lucene and Jackrabbit.