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The labelling of the plasma membrane with targeted fluorescent probes offers a convenient and non-invasive means to image the cell membrane and follow morphological changes and dynamics in real-time. However, despite many examples of fluorescent plasma membrane probes, a "universal targeting/anchoring moiety" is still required. In the first research section of my PhD, I report on the development of a small library of stearic acid-based probes, labelled with 6-carboxyfluorescein, via solid-phase synthesis, in which variation in both charge and hydrophobicity were explored. An optimal probe was discovered that carried both a positively charged amino group and a stearic acid tail that exhibited intense plasma membrane brightness and robust retention. In the second section of my PhD thesis, I investigated a light-driven, reversible addition−fragmentation chain-transfer (photo-RAFT) polymerisation with a newly developed fluorophore-conjugated RAFT agent, containing a BODIPY dye attached to a thiocarbonylthio group. This new RAFT agent enabled light-controlled (470 nm) "on/off" polymerisation, producing well-defined polymers, with excellent photostability. It provides an expedient route to homogeneous fluorescently-labelled polymers. In the third part of my PhD thesis, I discovered amphiphilic polymer-based fluorescent probes which showed long-term plasma membrane binding, and that allowed imaging and simultaneous functionalisation of the cell surface with azides, as shown by fluorophore attachment via cycloaddition chemistry. The polymer structure was optimised using a library approach.

Aesthetic outcome from breast cancer surgery influences long-term psychosocial wellbeing. There is no gold standard measure. An objective measure is required in order to communicate and compare results ultimately to raise standards for patients. Simulation of aesthetic outcome can cross language and literacy barriers, explaining ideas simply which may help to prepare women for their surgery and consequently, by managing expectations translate into better satisfaction long-term. The over-arching hypotheses was that 3D surface imaging (3D-SI) can be applied to both evaluate and model aesthetic outcome in oncoplastic breast surgery. An objective aesthetic outcome tool for breast conserving treatment (BCT) was developed using measures from 3D-SI, designed to replace panel assessment and for use in conjunction with patient reported outcome measures (PROMs). An expert panel scale was constructed using Delphi methodology for the reconstruction population for use in the development of an objective tool. Subscales include volume, symmetry, breast mound position, nipple position and shape in addition to a global scale. It was used to report aesthetic outcomes for the Primary Radiotherapy and Diep FlAp reconstruction (PRADA) study. A simulation model for BCT was designed. A randomised controlled trial demonstrated significantly better preparedness for aesthetic outcome having viewed a simulation pre-operatively compared to 2D photographs or a verbal description. A low burden online patient recruitment and data collection platform was shown to be feasible, accurate, and acceptable to patients. It is scalable for use within a large multicentre study to develop an objective aesthetic outcome tool and simulation model for the reconstruction population. 3D-SI demonstrates capabilities to provide a robust method to report aesthetic outcome. The role of simulation is encouraging and research into the long-term influence on patient satisfaction is ongoing. Future research within the reconstruction population and the development of cheaper, portable 3D-SI devices will enable widespread use.

This thesis is focused on characterising Oxia Planum, the landing site for the ExoMars 2022 Rosalind Franklin rover. This involved the investigation and mapping out of the sites' Clay-bearing Unit, as well as digitising the extensive fracture networks present, using visible to near infrared images. Alongside this a prototype geotechnics tool intended for inclusion on a future Mars mission, the Small Planetary Linear Impulse Tool (SPLIT), was tested to determine how it compares to existing geotechnics tools. The Clay-bearing Unit, consisting of two subunits, was investigated and mapped using the  instruments. This was performed to better understand Colour and Stereo Surface Imaging System (CaSSIS) and High Resolution Imaging Science Experiment (HiRISE) how the Clay-bearing Unit varies over its extent, and if any such variations correlated to other features at the site. It was found that differences between the two subunits are likely due to mineralogical variation rather than differences in surficial cover, with the formation of the subunits occuring before a channel-forming stage of aqueous activity at the site. Fracture digitisation using HiRISE was also performed, with sites from units at Oxia Planum having their fracture networks digitised and parametrised. These were compared to each other and with sites at Gale Crater; sites on the margins of an unnamed crater within the Vastitas Borealis north polar region; and two Earth-based sites. This indicates that several mechanisms are unlikely to have caused the fracturing seen at Oxia Planum e.g., hydraulic fracturing and thermal fracturing, and identified that the fracturing within the Clay-bearing and Capping Units likely originated during separate fracturing episodes. SPLIT is an instrument designed to remove the upper layers of a target rock, revealing unaltered material to depths of several centimetres. Testing was carried out on Martian analogue samples in field trials and laboratory tests. These tests were generally successful, defined as removing volumes comparable to that achieved using existing instrumentation, with a smaller power expenditure and in less time. However failure to operate on gypsum due to its friability, as well as on a sandstone and a siltstone sample due to the lack of exploitable weaknesses and low mass of these samples (~3 kg), highlight the mass and material strength limits at which SPLIT can nominally operate.

This dissertation describes the development of novel mass spectrometry (MS) methodologies and techniques to improve, simplify and allow for specific characterizations of synthetic materials. Successful MS analyses are governed by the mass spectrometry principles surrounding specific ionization sources, mass analyzers and ion detecters. The methods described within this dissertation provide information about polymer materials that is historically difficult to determine using other available analytical techniques.Self-assembled terpyridine (tpy)-based metallomacrocycles that are coordinatively-bound using various transition metals were investigated through the analysis of their collision cross-section (CCS) values obtained by travelling wave ion mobility (TWIM)-MS separation, and through comparison to modeled/simulated structures and theoretical CCS values. This work demonstrated the uniquely powerful ability of TWIM-MS separation for architectural verification in samples containing stoichiometrically-defined isobaric ion species ranging from dimeric macrocycles to hexameric macrocycles. Furthermore, TWIM-MS was utilized in a separate project which allowed for the development of a method to monitor concentration dependent supramolecular structural equilibria and conformational trends. Using the methodology in this work, equilibrium constants were derived from these data; this was illustrated for two equilibria concerning the self-assembly of a tpy-based ligand containing a flexible crown ether moiety with Zn2+ ions, and a tetrakisterpyridinyl ligand with Cd2+ ions, which have previously been shown to reversibly interconvert. Additionally, experimental CCS values were also derived from drift time measurements and compared with theoretical predictions for these complex self-assembled terpyridine-based supramolecules to provide insight into their size, stoichiometry and architecture.Parallel studies have focused on the development of methods that can obtain connectivity and compositional information about covalently cross-linked polymers. The atmospheric solids analysis probe (ASAP) ionization source has been combined with MS, tandem MS (MS/MS) and TWIM to create an effective top-down technique for the molecular characterization of the mentioned materials, which were utilized in this project to address persisting structural questions about synthetic polymer cross-linking microstructures. The structural insight gained from these studies was illustrated by the analysis of two hydrogels: 1) oxime cross-linked poly(ethylene glycol) (PEG) hydrogels formed from the click-reaction between 4-arm PEG star polymers with levulinamide or levulinic acid end group functionalities and 4-arm PEG star polymers with aminoxyacetaamide or aminooxyacetic acid end group functionalities, and 2) cross-linked poly(methacrylate) (PMA)-PEG hydrogels formed from PEGdimethacrylate (PEGDMA) polymerized via radical propagation in the presence of a lithium acylphosphazine (LAP) photoinitiator and ultraviolet (UV) light. Lastly, the design of a surface-specific imaging technique with a probing depth of

In radiation therapy of tumors in the thorax and abdomen, respiratory-induced motion creates challenges in different steps of the treatment, such as simulation, treatment planning, and the daily patient positioning. Different methods are clinically applied to reduce the impact of respiration in radiation therapy. However, most techniques involve invasive procedures or expose the patient to extra radiation. In this thesis, first, the application of combining stereotactic body frames with a surface imaging system for patient positioning in stereotactic body radiotherapy (SBRT) of lung cancer was evaluated. Stereotactic body frames are safe and non-invasive devices that reduce the impact of respiratory-induced motions by decreasing the range of the tumor motion. Surface imaging systems are also safe and dose-free technologies for patient positioning that have the ability to monitor the patient’s motion during radiation delivery with high precision. Combining the use of a surface imaging system with SBRT positioning frames adds another level of accuracy to patient setup and provides monitoring of the movements during treatment. The results of this evaluation indicated difficulty in using surface imaging with SBRT frames primarily due to the presence of the compression plate.Next, a patient-specific correspondence model was developed to track tumors in the thorax during radiation therapy treatments using surface displacement as the surrogate signal. The proposed model is made prior to the treatment for each patient. Two types of data are used for model construction: Four-dimensional computed tomography (4DCT) images of the patient and the displacement of two points on the patient’s skin on the thoracic area (surrogate signals). The two types of data are acquired simultaneously. The 4DCT images are sorted by the amplitude-binning algorithm to account for hysteresis and breathing irregularities. A deformable image registration algorithm is applied to the 4DCT images to calculate the deformation vector fields as the knowledge of the patient’s internal motion. Principal component analysis is used to fit the correspondence model. The model incorporates recorded surrogate signals during radiation delivery as an input and delivers the 3D trajectory of the tumor or other anatomy of the interest. This model accounts for hysteresis and irregular breathing. The accuracy of the proposed model was evaluated on a respiratory phantom and five lung cancer patients. The results showed a primary validation for localizing the tumors in the lung. Testing the model on a larger population of patients will examine the accuracy of the localization more precisely.

Advances in semiconductor microlithography have resulted in reduced transistor dimensions and consequent improvements in chip performance and cost. In the microlithographic process a photoactive material called a photoresist is uniformly spun cast on a substrate and selectively exposed to radiation, causing a chemical change in the exposed areas. The polymer is subsequently removed in either the exposed or unexposed regions, typically using an aqueous base developer. An alternative to the traditional lithographic method is a process called Top Surface Imaging (TSI). TSI has a number of advantages over traditional base-development techniques but is highly susceptible to line edge deformities commonly referred to as line edge roughness (LER). In TSI, the top surface of the photoresist is exposed to radiation, resulting in the generation of reactive sites. A gas phase, silicon-containing compound called a silylation agent reacts with these sites, causing selective incorporation of silicon. The silicon then acts as an etch mask in an anisotropic oxygen etch process. As the industry continues to improve resolution by shifting to shorter wavelengths, TSI’s lax transparency requirements provide it with a distinct advantage over traditional lithographic techniques. In this work, TSI was evaluated for use with three industrially relevant radiation sources, including 157nm light, low-voltage electron beams, and extreme ultraviolet light. An investigation into the origins of low frequency LER in TSI systems showed it to be the result of surface tension induced capillary instabilities (also known as a Rayleigh instability). The polymer contribution to LER was investigated by the synthesis of numerous high-Tg TSI polymers. Although many of these polymers are capable of producing high-resolution features, they all suffer from significant levels of LER. The kinetics of the gas phase reaction of the TSI polymer poly(hydroxystyrene) and the silylation agent dimethylaminodimethylsilane was investigated using variable angle spectroscopic ellipsometry, and was found to be front propagated and reaction limited. It was found that the addition of base quenchers to chemically amplified photoresists greatly minimizes LER, and a theoretical approach to understand this effect is presented. Overall, TSI performs well, but the nature of LER in TSI systems is still not fully understood.

Background: Breast cancer is the most common cancer in women worldwide, affecting one in eight. It can be detected by X-ray mammography, which is used in screening programs to find cancer at an early stage when treatment is often effective. Aim: The aim of this work was to overcome some of the limitations associated with mammography and interpret information "beyond 2D" from Digital Breast Tomosynthesis (DBT) and surface imaging in a clinically relevant way. Methods: Unmet user requirements in current breast imaging practice were identified and the properties of DBT and surface images were investigated with quantitative image analysis in mind. New imaging analysis methodology was developed with applications in cancer risk estimation, cancer assessment and treatment planning. Three separate studies were conducted to assess feasibility and clinical performance. Breast density, a well established risk factor for breast cancer, was calculated from mammograms and DBT images of 35 women with different methods and compared. 3D segmentations from DBT were validated with histo-pathological assessment of 20 breast tumours. The feasibility of using Microsoft Kinect, an inexpensive depth sensor for gaming applications, was demonstrated using a phantom, then assessed in 10 women undergoing reconstructive surgery. Results: DBT provides spatial information about breast composition in reconstructed image volumes, but resolution is highly anisotropic and images exhibit artefacts. It is currently not possible to distinguish between different breast tissue types and imaging artefacts overlapping anatomical structures for the breast as a whole. The Microsoft Kinect can map the surface of the breast with adequate precision (error < 1 mm), but performance varies with imaging conditions. Although it is not accurate to analyse the composition of the breast from DBT reconstructions due to significant artefacts, good correlation (p=0.95) with the mammographic gold standard can be achieved when analysing DBT projections with volumetric methods in combination with pre-processing. We have found that it is possible to distinguish between tissue structure and artefacts in the context of extracting 3D morphology of breast lesions and achieved similar correlation with histological sizing than expert annotation (p=0.69) and better agreement with tumour volumes estimated from pathology assessment (95% limits of agreement -16 to 11 ml). Using the Kinect for planning implant based breast reconstruction showed similar accuracy than achieved by experienced breast surgeons or using mastectomy specimen weight as guidance (standard error 120 ml, 141 ml and 142 ml, respectively). Conclusion: Quantitative assessment of both DBT and surface imaging could improve breast imaging practice and help clinicians to estimate breast cancer risk reliably, assess tumour size and morphology and plan breast reconstruction.

Ultra-Fast Scanning Tunneling Microscopy (UFSTM) is a novel imaging technique that uses high intensity femtosecond laser light to generate atomic defect states called "traps" and provide subsequent atomic surface imaging between pulses. Many surface engineering applications are possible through femtosecond laser induced damage (fs-LID), a process where a strong non-perturbing laser electric field generates a high density of charge carriers that eventually thermalize and impart energy into a material's lattice changing the surface morphology. The number of pulses during illumination plays a large role in the resulting morphology with current theory predicting the formation of trap states in-between pulses. The trap states are too subtle to observe using traditional methods (ie. scanning electron microscopy or optical based microscopy). This thesis presents a coordinated effort in developing a novel scanning tunneling microscope system capable of detecting atomic trap states. In particular, a discussion of the instrumentation challenges associated with UFSTM techniques are presented. This work also includes a brief summary of the X-ray STM imaging technique that can also be used for elemental resolved surface imaging. The instrumentation challenges associated with coupling x-ray light with a standard STM system is included.

The ability for bacteria to become resistant to existing antibiotics drives researchers to the development of novel ways to eradicate bacteria. Especially within the medical field, infections caused by antimicrobial resistant bacteria are a major problem, that can lead to life threatening illnesses. Because of these challenges bacteria have been studied extensively, and the scientific community looked for new ways to fight bacteria. The discovery of the various stages involved in biofilm formation allowed for the development surface active materials that specifically target bacteria when they attach to surfaces to multiply. Two general strategy routes were identified, that focus either on antimicrobial or antifouling surfaces, where the former focus on the eradication of bacteria once they attach to surfaces, and the later prevents the attachment of bacteria all together. In this thesis we explore the use of several antimicrobial photo-active materials that emit heat when irradiated with laser light, which in turn kill bacteria attached to these surfaces. Chapter 1 gives a general introduction into antimicrobial resistance and highlight the importance of the development of novel strategies to kill bacteria. This chapter will show methods that are currently for the design of antimicrobial surfaces, and will especially focus on photo-active surfaces. Chapter 2 gives a general overview of the main characterisation techniques used throughout the thesis, which are used for the characterisation of materials in chapters 3-5. This chapter also examines the techniques that are used to assess the antimicrobial performance of the materials developed in chapters 3-5. Chapter 3 shows a novel approach to fabricate a robust and cost effective photothermal material, by the incorporation of carbon nanopowder (CNP) into polydimethylsiloxane (PDMS). This material displayed photoactive properties across a broad spectrum of light, including the near infra-red (NIR) region, where water and living tissues are semitransparent, and therefore not susceptible to direct radiation damage. The material was used for the combined photothermal eradication of bacteria, showing efficacy against both Gram-negative (E. coli) and Gram-positive (S. aureus) bacterial species. Chapter 4 continues with the carbon nanopowder (CNP) polydimethylsiloxane (PDMS) composite material of chapter 3, which was surface modified to allow for single cell correlation across technically incompatible surface imaging techniques (SEM and fluorescence microscopy). This surface modification consisted of fabricating the CNP PDMS with a grid structure that could be identified using both imaging techniques. Single cell correlation between these imaging techniques allowed us to study the effect of various temperatures on the bacterial cell membrane of Escherichia coli, and obtained more information than either imaging technique could have provided. Chapter 5 combines the photo-thermal efficiency of gold nanostars/nanorods with the flexible properties of PDMS, to create a hybrid material that can be used for the correlation of imaging techniques, as well as the eradication of bacteria. The chapter focusses on the fabrication of various surfaces with microstructures, and the challenges that needed to be overcome during the production process.

This thesis provides a piece of comprehensive information on the interrelationship between particle properties, formulation properties, and the performance of pharmaceutical powders. Three main performance categories were investigated; these include flow, disintegration, and dissolution. The effect of formulation properties on the dissolution performance of a pharmaceutical formulation containing a low soluble active pharmaceutical ingredient was explored. A novel, dynamic contact angle measurement technique was used to understand wetting behaviour and provide correlations with dissolution testing using biorelevant dissolution media. In addition, this thesis explored the link between the microstructure obtained by X-ray microtomography and the dissolution performance. The thesis also investigates how formulation properties such as disintegrant type and the amount of lubricant affects the disintegration behaviour of pharmaceutical tablets by coupling a novel surface imaging instrument with an in-line particle size analyser. This thesis also presents novel data analysis techniques with the aim to build a modelling framework that can be used to relate particle properties of pharmaceutical powders such as particle size and shape to their flow performance. Radial basis function (RBF) and neural network techniques were used to achieve this goal. Traditional data analysis techniques such as multivariate data analysis were used to build correlations between particle properties and powder performance. This is of great importance in the early stages of drug discovery activities. The information from this thesis therefore demonstrates how novel experimental and modelling techniques can be used to related particle properties and formulation properties to the performance of pharmaceutical powders.

Rheumatoid arthritis is a chronic autoimmune disease, characterised by joint inflammation, which if untreated causes disability. A clinical need exists for novel, low-cost and noninvasive imaging tools capable of detecting inflammation in the joints for the diagnosis and monitoring of patients with rheumatoid arthritis. Diffuse optical imaging provides information about the underlying functional properties of biological tissue and previous studies have reported an optical contrast between inflamed and non-inflamed joints, with former displaying localised increases in absorption and scattering attributed to underlying pathophysiological changes. In this work, a novel, multispectral diffuse optical imaging system for imaging human hand joints was presented, which combined surface imaging and optical transmission imaging in a single work-flow to reconstruct maps of clinically relevant parameters such as oxygen saturation, total haemoglobin, water and scattering amplitude in three dimensions. The system was designed to provide accurate, robust and rapid data acquisition, particularly through the novel application to joint imaging of a galvanometer-based unit for fast source repositioning allowing full datasets to be acquired in 2mins per joint, such as to be sufficient for implementation in a clinical setting. This clinical prototype system was then comprehensively studied through experiments involving biological tissue mimicking optical phantoms, to assess performance against a ground truth set of known parameters. Preliminary studies involving healthy volunteers gave useful insight into the systems in vivo performance and provided a good understanding of baseline values in healthy subjects, with significantly greater variability observed between subjects than when comparing joints within the same subject. A pilot clinical study was then carried out, involving 144 joints from 21 rheumatology patients with ultrasound imaging and clinical examination as reference comparisons, to assess the systems diagnostic accuracy capabilities. A degree of sensitivity was observed from three dimensional maps of total haemoglobin and scattering amplitude to pathophysiological changes in the joint during longitudinal monitoring of either recovery from acute injury in a single healthy subject or the response to therapy in rheumatoid arthritis patients. From single time-point examination data, classification accuracies when considering the entire cohort were limited, with areas under the receiver operator curve of up to 0.657 achieved, with similar conclusions reached to those in comparable single-wavelength, continuous-wave studies previously reported despite the multiple wavelength acquisition. A normalised Fourier transform methodology was then presented, engineered to extract features related to the spatial signature of the transmitted light through the joint that were less sensitive to inter-subject variability in total flux for the assessment of optical transmission images. For the first time within the academic community, to the authors knowledge, the impact on diffuse optical imaging signals of the spatially asymmetrical prevalence of inflammation in hand joints of rheumatoid arthritis patients was addressed. In distinction from previous work, optical images were acquired from the dorsal side with illumination on the palmar side and results when using the proposed normalised fast Fourier transform methodology demonstrated accurate detection of inflamed joints from single time-point examinations, with of area under the receiver operator curve values up to 0.888 together with sensitivities and specificities of up to 77.9% and 90.9% respectively achieved for this specific dataset. This work-flow may enable future development of clinically viable, low-cost devices for assessing inflammation in arthritis patients, without the need for cuff occlusion or comparison to baseline. It will be important to assess the generalisation of these accuracies in future work, using a larger patient cohort and testing different machine learning classification schemes.

This thesis presents the first experimental investigations into resistive guiding of fast electrons using conically structured targets. Two experiments are presented in which a combination of experimental diagnostics and simulations are used to examine the performance of resistively generated magnetic fields in reducing the fast electron divergence. A critical aspect of this work is the deployment of a novel front surface imaging system to determine the location of the laser-target interaction. Significant rear surface heating is inferred in both experimental campaigns using shadowgraphy and one-dimensional hydrodynamic simulations in HYADES. Conically structured targets are shown to reach temperatures of up to 200eV; a significant enhancement at greater depth and reduced laser energies than results reported in the literature. Analysis of the laser focal spot and three-dimensional hybrid simulations in ZEPHYROS show how an astigmatic beam with significant energy outside of the main peak can enhance the confinement of electrons and improve the volumetric heating of the target. Proton diagnostics are used to determine the performance of conically structured targets. Significantly, an enhancement in peak proton energy is recorded for cones with opening half-angles of approximately 10 degrees. We suggest a mechanism underpinning these results and how the ability of the cone targets to reduce the fast electron divergence is sensitive to the specific target geometries implemented on the experiments. The fast electron beam that escapes the rear surface is observed to filament using a combination of image plate (IP) and coherent transition radiation (CTR) diagnostics. Three-dimensional hybrid simulations using ZEPHYROS present similar filamentation and show how the observation of the break-up of the electron beam does not significantly inhibit the resistive guiding mechanism.

In real-time applications, solder joints are exposed to thermal and mechanical stresses. As a result, the microstructure evolves, and mechanical characteristics deteriorate, resulting in component failure. Solders have progressed from the typical SnPb (tinlead) alloys to lead-free alloys containing dopants such as bismuth (Bi), antimony (Sb), and nickel (Ni). Alloying with these metals was found to improve the thermal and mechanical properties of the solder; however, multiple factors dictate the rate of damage accumulation and microstructure evolution of the solder joints. Also, the literature did not report the effects of homogenous SAC-Bi alloys on the reliability, coarsening kinetics of IMC particles, and evolution of creep deformation properties during thermal cycling. This dissertation investigates the effect of thermal cycling on the evolution of the mechanical and microstructure properties of newly developed lead-free alloys. The first study investigated the impact of Bi content on the creep behavior of solder joints under different aging conditions. Three types of lead-free solder alloys (SAC305, SAC-3Bi, and SAC-6Bi) were tested at room temperature, and three stress levels were defined for each alloy using preliminary microindentation tests. The strain vs. time data obtained from the tests were analyzed, and a new approach based on an empirical model was developed to systematically study the creep strain rate. A power dependency prediction model was also developed to investigate the creep mechanisms during different cycles. The creep mechanism associated with each strain rate vs. stress curve was identified. Microstructural analysis was carried out using SEM with EDX to examine the evolution of creep strain rate. Power law creep was found to be the dominating creep mechanism for all the solder alloys tested at predefined stress levels. The creep strain rate of Bi-based alloys is significantly lower than that of SAC305 due to the presence of Bi in the solid 3 solution. A slight change in the creep rate was noticed for SAC-6Bi compared to SAC-3Bi after 1000 hrs of aging. The second study assessed the reliability performance of the lead-free solder joints compared to SnPb on CABGA208 and SMR2512 packages. Five homogeneous leadfree solder alloys, including SAC305, SAC-3.3Bi, SAC-0.5Bi-6In, SAC-0.5Bi-1.4Sb0.15Ni, and Sn63Pb37 and two components (CABGA208 and SMR2512) were considered in this study. The test board was FR-4 with an organic solderability preservative (OSP) surface finish. After reflowing, the boards were thermally cycled at room temperature after 10 days of storage. Scanning electron microscopy (SEM) integrated with energy-dispersive spectroscopy (EDS) was performed to study the microstructural development at different cycle counts. The failure data were fitted to two-parameter Weibull curves. Representative cross-sections were used to investigate the IMC particles and the failure mode. Among all CABGA208 components, cracks were localized in the bulk solder on the component side. Also, the components containing 3% Bi alloys outperformed SAC305 and SnPb. The third study investigated the impact of Bi content on the microstructure and IMC layer evolution under various thermal cycling conditions. Five lead-free solder alloys, including SAC305, SAC-3.3Bi, SAC-0.5Bi-6In, SAC-0.5Bi-1.4Sb-0.15Ni, and Sn63Pb37, were used to assemble test boards and subjected to thermal cycling according to the JESD22-A104E standard. The IMC layer growth and Ag3Sn particle coarsening were analyzed using optical and scanning electron microscopy equipped with EBSD at various cycle intervals. Backscatter electron imaging was used to produce electron micrographs of the specimens for each test combination. Four high strain-localized regions were identified to characterize the Ag3Sn particles at each cycle interval. The multiple threshold approach is used to analyze particle size, number, and density of 4 the IMC particles using the surface imaging and analysis software Mountains® 9. In terms of microstructure, the impact of adding Bi was prominent, as solder joints containing 3% Bi exhibited less coarsening after 250 cycles with more evenly distributed precipitates. The IMC layer growth rate for Bi-based alloys was relatively low compared to SAC305 and SnPb. The fourth study analyzed the effect of newly developed solder alloys on the evolution of mechanical properties during ATC. Five lead-free solder alloys, including SAC305, SAC-3.3Bi, SAC-0.5Bi-6In, SAC-0.5Bi1.4Sb-0.15Ni, and Sn63Pb37, subjected to thermal cycling according to the JESD22- A104E standard. The microstructure, steady-state creep, and hardness properties were studied for 0, 100, 250, 625, 1560, and 3900 cycles. It was found that the creep deformation rate increased with the stress levels for all solder alloys. In addition, micro-alloying with Bi improved the creep deformation resistance through the solid solution strengthening and hardening mechanisms, and the creep rate variation was less noticeable after 250 cycles. A strong correlation between the thermal fatigue life, the creep deformation/hardness, and the particle density was established, providing insights into the behavior of SAC-based solders under realistic conditions. Overall these studies contribute to developing more reliable electronic components by advancing the understanding of creep behavior in solder alloys.

Dependence on membrane technology in seawater desalination and wastewater reclamation is increasing rapidly due to potable water shortages across the world. Nanofiltration (NF) and reverse osmosis (RO) are widely used membrane filtration techniques which use hydraulic pressure as the driving force for mass transport through the membrane. Interest is growing in use of forward osmosis (FO) membrane technology in wastewater reclamation and as a pre-step to low pressure reverse osmosis due to potential energy reductions. In FO, two liquids with different osmotic pressures are separated by a membrane and the osmotic pressure difference is the driving force for water permeation from the feed side to the draw side, eliminating the need for hydraulic pressure. Membrane fouling is an unavoidable problem facing all membrane processes. The presence of contaminants such as organic waste and bacteria in the feed solution can lead to membrane fouling and to a reduction in performance. This study aims to research cleaning methods that don't involve the use of harmful chemicals for fouling control in FO and RO membrane processes. Cleaning efficiency is tested under varying physical and chemical conditions. Efficiency is determined in terms of both flux restoration and fouling layer removal as it has been determined in this study that significant flux restoration does not translate to complete fouling layer removal. Feed solution chemistry, such as the quantity of Ca2+ in the feed and the operating pressure, and therefore initial flux greatly influence the rate and extent of fouling and therefore the efficiency of cleaning. Understanding fouling behaviour during operation and cleaning is important when optimising cleaning methods for RO and FO. For this reason, this study uses numerous visualisation and surface characterisation techniques to improve understanding of the fouling structure before and after cleaning. The first aim of this study is to examine the efficiency of osmotic backwashing as a way of controlling organic fouling of BW30 membranes through both pure water flux measurements and membrane surface imaging. Confocal laser scanning microscopy is used to determine the thickness of the fouling layer before and after osmotic backwashing. Firstly, the influence of feed solution chemistry was examined. After 6.5 hours of organic fouling with alginic acid, the fouling layer thickness increased from 37 μm in the absence of calcium in the fouling solution to 179 μm in the presence of 2.5 mM CaCl2. This occurred due to the formation of thick compact gel fouling layer as carboxyl groups present in alginate fouling form complexes with Ca2+. One minute of backwashing with 0.7 M NaCl resulted in initial pure water flux restorations of 90% for the membrane fouled in the absence of CaCl2 compared to 86% for the membrane fouled in the presence 2.5 mM CaCl2 despite the fact that 31 μm and 141 μm of foulant remained on these membranes respectively. As well as the feed solution chemistry, the impact of initial flux, on fouling and cleaning in RO was examined. As expected, higher initial fluxes resulted in thicker fouling layers with the layer increasing from 39 μm for an initial flux of 25 L/m2h to 270 μm for an initial flux of 100 L/m2h. Although flux restorations of 100% were achieved for initial fluxes of 25 and 33 L/m2h, foulant layers of 9 μm and 25 μm remained on the membrane surface respectively. This again shows that flux restoration alone cannot indicate cleaning efficiency as high values have been reported even when significant fouling remains on the membrane surface. Only 75% of the initial pure water flux was restored after fouling with an initial flux of 100 L/m2h showing that organic fouling at higher initial fluxes is largely irreversible due to the high hydraulic pressure applied to the fouling layer making it more dense and compact. As the solution chemistry of the feed solution has a significant influence on the fouling layer characteristics, it is questioned whether the backwashing solution could alter the fouling layer characteristics during one minute of backwashing. In order to examine this, backwashing with a solution of 0.5 M CaCl2 was tested. SEM-EDS measurements showed that the amount of elemental calcium on the membrane decreased by 19% after backwashing with NaCl but increased by 26% after backwashing with the same osmotic pressure of CaCl2. Atomic force microscopy was used to quantify the adhesion forces and elasticity of the fouling layers. The membrane backwashed with CaCl2 displayed adhesion forces twice that of the virgin membrane due to the presence of Ca2+ ions forming complexes with carboxyl groups in the fouling layer. In terms of the elastic forces, the sample backwashed with NaCl displayed forces similar to that of a virgin membrane showing that the fouling layer is stiff and firm. This is because the layer becomes much thinner and closer to the membrane surface. The fouled membrane was the most flexible and "fluffy" however after backwashing with CaCl2 the fouling layer remains flexible and soft, again showing that Ca2+ forms complexes with the fouling layer. SEM was also used to compare the morphology of the fouling layer before and after backwashing. Different backwashing trends are observed in osmotic backwashing of organically fouled forward osmosis membranes. In this case, the alginate fouling layer thickness increased from less than 33 μm, in the presence of 0 mM Ca2+ in the feed to 173 μm in the presence of 2.5 mM Ca2+. One minute of backwashing removed almost 100% of the fouling layer in each case and restored 93% of the flux in the absence of calcium and 100% for the membrane fouled in the presence of 2.5 mM CaCl2. Backwashing became less effective as the initial membrane fouling flux was increased. This was increased by increasing the draw solution concentration. For a draw solution of 4 M NaCl the fouling layer decreased in thickness to 113 μm but backwashing with 0.7 M NaCl only removed 19% of the fouling layer showing that although it was thinner, the fouling layer was, in fact, more compact and dense. In this case, despite 90 μm of fouling remaining on the membrane surface, 100% of the flux was restored. As with the case of organic fouling with RO, this result shows that flux restoration alone cannot indicate how effective membrane cleaning is. To test the true efficiency of backwashing in organic fouling of FO membranes, 5 consecutive fouling and backwashing cycles were performed. Even after 5 cycles, backwashing with 0.7 M NaCl can still remove the fouling layer and restore the initial pure water flux to 97%. This shows that backwashing is effective for the FO membranes subjected to organic fouling. The limitations of backwashing in FO are evident in the context of initial bacteria adhesion on FO membranes. Initial adhesion of Pseudomonas putida on forward osmosis membranes was performed for 30 minutes resulting in an 18% membrane surface coverage of live bacteria cells. Backwashing with 0.7 M NaCl was ineffective while backwashing with 3 M NaCl offered a higher backwashing flux and therefore removed 93% of the adhered cells. After 60 minutes of bioadhesion under the same conditions, 3 M NaCl backwashing was not effective as 13% of the membrane surface remained covered in dead cells. In order to test how the feed solution chemistry effects cell adhesion, varying concentrations of CaCl2 were added to the feed resulting in an increase in live cell surface coverage from 18% in the absence of calcium to 27% in the presence of 5 mM CaCl2. This is due to a reduction in the cell-surface separation distance as the Ca2+ ions reduce the repulsive force between the cells and membrane surface therefore increasing adhesion. This increase in adhesion resulted in a decrease in backwashing efficiency as the 3 M NaCl backwashing solution only removed 40% of the total bacteria. Backwashing with solutions of CaCl2 was tested to determine if 1 minute of backwashing was enough time for Ca2+ ions to influence the cells on the membrane surface. As with organic fouling, the Ca2+ ions in the backwashing draw solution influenced the cells on the membrane surface resulting in a reduction in backwashing efficiency. Backwashing with 3 M CaCl2 only removed 40% of the cell surface coverage compared to 93% for backwashing with 3 M NaCl. This study shows that cleaning without the use of harmful chemicals in membrane processes depends strongly on the type of process, the type of fouling, the fouling feed solution chemistry and the initial membrane flux. It also shows that the type of backwashing draw solution is important as even 1 minute of backwashing is sufficient time for interactions to occur between the draw solution and the fouling layer. Finally, this study shows that flux restoration alone cannot indicate how effective membrane cleaning is and that the membrane surface must be examined either by imaging or another surface characterisation method (e.g. SEM-EDS) in order to get a complete picture of cleaning efficiency.

Seismic site characterization is a critical part of understanding earthquake hazards in geotechnical engineering. This is often accomplished through various invasive and non-invasive methods for measuring shear-wave velocity (Vs) in-situ, as it is directly related to small-strain shear modulus. For civil engineering applications, the seismic conditions of the near surface (top 30 m) are of particular interest. Surface wave testing has become the tool of choice for many engineers due to its flexibility, efficiency, and ability to characterize a wide variety of subsurface conditions. Surface wave testing is also particularly well suited to near-surface imaging due to the prevalence of surface waves within the elastic wavefield at shallow depths. Surface wave testing, however, is not without limitations. Inversion of surface wave dispersion data is ill-posed and non-unique, meaning that when it is performed rigorously with full consideration of epistemic uncertainty, a potentially large number of reasonable and different 1D Vs profiles are produced. This presents a challenge of evaluating which profiles should be used for further analysis or design. Additionally, engineers often desire information about the lateral variability of seismic parameters in the subsurface, but the inherently 1D nature of the processing and inversion techniques used in surface wave testing make acquiring this information challenging. Evaluation of lateral variability is generally accomplished through multiple individual 1D surface wave analyses across the site, providing only pseudo-2D information. This also introduces a new challenge: how to collect the large amount of experimental data required for multiple analyses as the efficiency of traditional surface wave acquisition is limited by the need to physically move geophone arrays with limited numbers of sensors. This dissertation discusses these challenges and presents potential solutions through the application of the DeltaVs method, distributed acoustic sensing, and full waveform inversion.

Fingerprints are used to identify individuals in both criminal and civil cases based on their unique pattern of characteristic ridge details. Latent, i.e. non-visible, fingerprints are the most commonly exploited type of fingermark, since they are frequently left at a crime scene. However, they must be visualised via an enhancement method, the nature of which is dependent on the substrate. Physical developer (PD) is a widely used effective chemical enhancement method for the visualisation of fingerprints on porous surfaces, notably paper. The principle of the technique is based on a ferrous/ferric redox couple reducing silver ions to colloidal silver metal, which is stabilised by a surfactant formulation. Recent environmental legislation banning a crucial surfactant component – Synperonic N – motivates the design of a new formulation. This requires determination of the mechanism of the PD process and the roles of the components; previous work is macroscopic and empirical. This thesis describes solution and interfacial measurements and surface imaging that provide mechanistic insights and real-time dynamics of the process. Dynamic light scattering and microscopy reveal the particle size in solution. These particles deposit selectively on the fingermark, interacting with chemical constituents identified via spot tests, and grow to a size over an order of magnitude greater than in solution. Silver nucleation and growth on the surface are independent of the age of the mark. Neutron reflectivity measurements revealed that the cationic surfactant component, n-dodecylamine acetate, adsorbs more strongly to a silver surface in the presence of a non-ionic surfactant. Working solution stability variations with surfactant formulation are characterised, together with the effect on latent mark development times. The mechanistic and structural insights are used to design an alternative PD formulation with greater stability at no loss of the image quality.

Landmines are still a very existent threat to large parts of the world and some reports even suggest that it is increasing. A method which could aid in their discovery is Electrical Capacitance Tomography (ECT) which can perform non-invasive sub-surface imaging. ECT can create permittivity distributions and using a planar array sensor should be possible to distinguish artificial landmines form their natural surroundings. A software toolbox, DeTECT , was developed at the start of the project made specifically for landmine detection using ECT. New planar array sensors were designed which improved the depth at which ECT could reconstruct inclusions. From this work a new sensor, the Combined Sensor, was developed which showed how further improvements in object shape and location detection could be made. In order to improve image reconstruction a new Automatic Parameter Selection (APS) algorithm was created which solved the problem of manually selecting the best parameters and will make using ECT for landmine detection more accessible. The Combined Sensor was implemented by designing and manufacturing a bespoke switching mechanism, the Impedance Analyser (IA) Switch, which allowed further improvements in permittivity distribution imaging. Finally, scanning methods were conceived and tested which will have a direct application to landmine detection in the future. They showed that using temporal reconstruction could significantly improve the shape and location detection of objects both in simulations and in real experimental setups. These methods were then tested on a large scale to show how by scanning a sensor over an area, a complete image of the entire region could be reconstructed using a special technique which performs complete reconstructions with the aid of multiple measurements. Using the new Combined Sensor in conjunction with scanning techniques and APS could compliment existing landmine technology and help to reduce risk to future detectorists.

Light management is essential to improve the performance of optoelectronic devices as they depend on the interaction between photons and device design. This research demonstrates novel approaches to enhance the light absorption in thin-film III-V photovoltaics (PV) and light emission from micrometer-scale light-emitting diodes (μLED). The high power conversion efficiency (PCE) realized in III-V PV makes them attractive power generation sources, especially for off-the-grid space-related missions. Thin-film PV (< 1 μm) offer great tolerance towards the inevitable radiation damage in the space environment as carrier collection is maintained compared to their optically thick counterparts (3-5 μm). To combat transmission loss of photons traveling through the thinned device, this work develops textured back surface reflectors (BSR) to increase the optical path length (OPL) of unabsorbed photons to generate electron-hole pairs. The textures are created via etching techniques and epitaxial regrowth and are characterized by surface imaging and reflectance (R) measurements. The textured BSR with high diffuse R increase the OPL, and the best-known design demonstrates over a four-fold increase in the OPL, which is two times greater than the planar BSR. This research delivers new analyses useful to the PV community, including the lifetime enhancement factor and free-carrier absorption modeling, which aim to improve the PCE in thin-film PV. Modern display technology is constantly integrated into daily use to convey information and connect people worldwide. The next generation of wearable devices requires small-featured displays to achieve high resolution. The μLED delivers value to near-eye displays through low power consumption, long lifetime, high contrast, and increased resolution. As these devices reduce in size, surface states limit the light output power (LOP) at the roughened sidewalls, and the perimeter-to-area ratio must be considered. This research focuses on developing a fabrication process that improves LOP through sidewall treatments. The dry etch process is optimized to reduce surface roughness, and sidewall treatments via wet-chemical etching, in situ etching, and regrowth aim to improve the sidewall quality. Scanning electron microscopy on the LED sidewalls supports the optimized fabrication process. Luminescence characterization reveals that combinations of etching and regrowth suppress non-radiative recombination events. These techniques render pathways to enhance LOP in LEDs smaller than 25 μm x 25 μm.

In this thesis, we introduce new methods for analysing three dimensional surface texture using high resolution normal fields and apply these to the detection and assessment of skin conditions in human faces, specifically wrinkles, pores and acne. The thesis is part of a project sponsored by Unilever with an interest in applying the outcome of the research to facial skin care product development. This explains our focus on facial skin conditions. The main contributions of this thesis are the introduction of three methods of extracting texture descriptors from high resolution surface orientation fields, a comparative study of two-dimensional and three-dimensional skin texture analysis and the collection of an extensive dataset of high resolution 3D facial scans presenting various skin conditions. The dataset includes human rating judgements on the presence of certain skin conditions. Computer aided skin condition assessment has been mostly addressed using two dimensional texture analysis techniques on skin images or coarse geometrical features extracted from the skin’s three dimensional macro structures. While the first trend ignores the three dimensional nature characterising most of the skin conditions, the latter mainly deals with geometrical features that are not fine enough to capture skin structures at the meso and micro scales. Advances in three dimensional surface imaging during the last few decades brings the possibility of capturing human skin’s fine geometrical structures and re- flectance properties with unprecedented quality and resolution (down to the level ii of the pores). The methods proposed in this work aim at leveraging these advances and revisit the formulation of texture analysis as a three dimensional problem. For data collection we set up a Lightstage to capture high resolution facial normal fields along with reflectance properties. The collected data are photo-realistically rendered and presented to the general public for annotations indicating the presence of the studied skin conditions. These constitute the ground truth on which we apply the proposed methods and learn models for detecting and assessing facial skin conditions. We also demonstrate that some of these three dimensional surface texture descriptors can be extended to synthesize highly detailed skin structures and simulate the studied skin condition on normal faces.

A great number of chemical and mechanical phenomena, ranging from catalysis tofriction, are dictated by the atomic-scale structure and properties of material surfaces. Despite such enormous significance, the principal tools utilized to characterize surfaces at the atomic level rely heavily on strict environmental conditions such as ultrahigh vacuum and low temperature. Results obtained under such well-controlled, pristine conditions bear limited relevance to the great majority of processes and applications that often occur under ambient conditions. In this thesis, we report true atomic- resolution surface imaging via conductive atomic force microscopy (C-AFM) under ambient conditions, performed at high scanning speeds. We hypothesize that atomic resolution can be enabled by either (i) a confined, electrically conductive pathway at the tip–sample contact, or (ii) tunneling through a confined water layer accumulated on the sample surface under ambient conditions. Our approach delivers atomic- resolution maps on a variety of material surfaces that comprise defects including single atomic vacancies. Using our method, we also report the capability of in situ charge state manipulation of defects on MoS 2 . Finally, we employ the high-speed C- AFM methodology to study a thin transition metal carbide crystal (i.e., an MXene), α–Mo 2 C. Along with a variety of atomically-resolved defect structures, we observe an exotic electronic effect: room-temperature charge ordering. Our findings demonstrate that C-AFM can be utilized as a powerful tool for atomic-resolution imaging and manipulation of surface structure and electronics under ambient conditions, with wide-ranging applicability.

Comparative planetology is a growing discipline, and one which seeks to fundamentally address and improve our understanding of the Earth in the context of wider solar system processes. Missions to the other terrestrial planets vastly increase the data available for observation of contrasting planetary processes, and the upcoming 2016 NASA InSight mission to Mars is of particular importance. In recent years, exploration missions have focused primarily on surface imaging or geochemistry; InSight aims to penetrate deeper into Mars to observe what is happening at depth. To do this, it will use seismic energy to image and map the interior. Amongst other geophysical payload instruments, it will deploy two three-component seismometers (one short period and one broadband sensor) on to the Martian surface atop a tripod. In this thesis, I address the primary InSight team science goals by characterising and quantifying potential sources of seismic and acoustic energy that may provide signal to map the interior of Mars. In the first science chapter, I explore the potential of tectonic sources for InSight by analysing a series of faults known as the Cerberus Fossae on the Elysium Planitia of Mars. I found that these graben have the best evidence on Mars for current and on-going tectonic activity. Combining topographic data with crater count statistics to date the faults allowed me to calculate a size frequency distribution of events. By then taking into account the InSight instrument capabilities and the environmental noise estimates for Mars, I calculate there to be between 1.5 x 100 and 1.9 x 105 detectable tectonic events per year from the Cerberus Fossae. The implication of this number of events for InSight is important, since it compares to previous estimates of global tectonic activity. Events at the source-receiver distance of the Cerberus Fossae to the InSight landing site may also penetrate deep into Mars, sampling the structure of the mantle and potentially the core-mantle boundary. The second science chapter focuses on meteor airbursts as a potential seismo-acoustic source for InSight. By combining terrestrial analogue data with modelling of bolide properties, I was able to define a catalogue of diagnostic properties to identify an airburst, determine novel ways to utilise frequency content of the signal to determine parameters such as source-receiver distance and explosion yield, as well as estimate a number of detectable events per year for InSight. Here I predict between zero and 8.13 ± 1.68 x 106 , depending on the bolide material and strength parameters. This number is also significant for InSight, since it will allow NASA to address its science goal to observe and characterise the Martian impactor population. Smaller meteors are more likely to impact the top of the Martian atmosphere because of the size-frequency distribution of the source population. However these smaller bodies are also more likely to fragment. The ability to recognise airbursts will vastly improve the statistics of the observation of the Mars impactor population. The final science chapter concerns the deployment of the InSight seismometers and explores how the deployment configuration may affect the recording of signal from external seismic sources. I carry out a series of experiments in an analogue field environment designed to test how the seismometer mounting tripod mass and leg con'figuration affect the coupling of the signal from the regolith to the sensor. I find that the tripod transfer function does influence the signal recorded by the sensors. The resonance of the tripod platform imparts energy at spurious frequencies within the frequency range of interest for InSight. This effect will need to be taken into consideration and removed before the real InSight data is analysed. InSight will greatly increase our understanding of how Mars and the solar system evolved. By predicting and characterising signal inputs and highlighting potential problems, I hope to contribute to the analysis and understanding of the real InSight data when it is returned form Mars in 2016.

This research focuses on understanding the effects of accelerated aging through temperature and environment on novel gallium nitride-based Hall effect magnetic field sensors and determining device reliability under electric vehicle operating conditions. The device reliability was modeled using accelerated aging for the temperatures of 200 °C, 350 °C, 450 °C, and 600 °C under various time steps unique to each temperature and either air, which is identical to operating circumstances, or argon, which would model the hermetic packaging environment. Using a high temperature furnace and oven, devices underwent high temperature storage tests at a chosen temperature and time step. Afterwards, device electrical response as well as surface imaging was used to determine the degree to which devices had degraded. This data was then used to create accelerated aging models used to predict the lifetime of the gallium nitride devices under the target operating conditions of 150 °C in air. This thesis explores the enabling aspect of the development of novel wide-bandgap devices for use under industry-relevant conditions.

Standard optical microscopes cannot resolve images below 200 nm within the visible wavelengths due to optical diffraction limit. This Thesis reports an investigation into super-resolution imaging beyond the optical diffraction limit by microsphere optical nano-scopy (MONS) and submerged microsphere optical nano-scopy (SMON). The effect of microsphere size, material and the liquid type as well as light illumination conditions and focal plane positions on imaging resolution and magnification have been studied for imaging both biological (viruses and cells) and non-biological (Blu-ray disk patterns and nano-pores of anodised aluminium oxide) samples. In particular, sub-surface imaging of nano-structures (data-recorded Blu-ray) that cannot even be seen by a scanning electron microscope (SEM) has been demonstrated using the SMON technique. Adenoviruses of 75 nm in size have been observed with white light optical microscopy for the first time. High refractive index microsphere materials such as BaTiO3 (refractive index n = 1.9) and TiO2-BaO-ZnO (refractive index n = 2.2) were investigated for the first time for the imaging. The super-resolution imaging of sub-diffraction-limited objects is strongly influenced by the relationship between the far-field propagating wave and the near-field evanescent waves. The diffraction limit free evanescent waves are the key to achieving super-resolution imaging. This work shows that the MONS and SMON techniques can generate super-resolution through converting evanescent waves into propagating wave. The optical interactions with the microspheres were simulated using special software (DSIMie) and finite different in time domain numerical analysis software (CST Microwave Studio). The optical field structures are observed in the near-field of a microsphere. The photonic nanojets waist and the distance between single dielectric microsphere and maximum intensity position were calculated. The theoretical modelling was calculated for comparisons with experimental measurements in order to develop and discover super-resolution potential.

Millimetre-wave radar in a missile seeker for the engagement of ground targets allows all-weather, day and night, surface imaging and has the ability to detect, classify and geolocate objects at long ranges. The use of a seeker allows intelligent target selection and removes inaccuracies in the target position. The selection of the correct target against a cluttered background in radar imagery is a challenging problem, which is further constrained by the seeker’s hardware and flight-path. This thesis examines how to make better use of the components of radar imagery that support target selection. Image formation for a squinted radar seeker is described, followed by an approach to automatic target recognition. Size and shape information is considered using a model-matching approach that is not reliant on extensive databases of templates, but a limited set of shape-only templates to reject clutter objects. The effects of radar sensitivity on size measurements are then explored to understand seeker operation in poor weather. Size measures cannot easily be used for moving targets, where the target signature is distorted and displaced. The ability to detect, segment and measure vehicle dimensions and velocity from the shadows of moving targets is tested using real and simulated data. The choice of polarisation can affect the quality of measurements and the ability to reject clutter. Data from three different radars is examined to help to understand the performance using linear and circular polarisations. For sensors operating at shorter ranges, the application of elevation monopulse to include target height as a discriminant is tested, showing good potential on simulated data. The combination of these studies offers an insight into the performance factors that influence the design and processing of a radar seeker. The use of shadow imagery on short-dwell radar seeker imagery is an area offering particular promise.

Microscopic techniques were used to study the surface behaviour of model active pharmaceutical ingredients (APIs) and excipients, while under stress, and this was compared with the response of the bulk material. The model APIs were caffeine/oxalic acid, caffeine/malonic acid cocrystals and aspirin whilst spheronised microcrystalline cellulose (s-MCC), pregelatinised starch (PGS) and dicalcium phosphate dehydrate served as examples of excipients. The difference between the surface and bulk behaviour of caffeine cocrystals in response to storage in controlled humidity environments was investigated. Surface imaging illustrated an anisotropic element to the microstructure of the caffeine cocrystals, which became more pronounced at the extremities of relative humidity (RH) storage. The trends in surface reactivity which were observed for the cocrystals were found to follow those previously reported for bulk behaviour, using PXRD. Atomic force microscopy imaging, however, gave an earlier indication of incompatibility between the ecocrystals and > 75% RH, with surface transformations occurring on a shorter timescale than indicated from the results of bulk analysis. This work represents the first reported analysis of organic molecular cocrystals by AFM. The material properties and subsurface structure of s-MCC and PGS were examined using AFM. Phase imaging and force measurements identified heterogeneity in the material properties of these excipient particles. In the case of s-MCC, the results were used to support a theory for intragranular porosity. The solid-state hydrolysis of aspirin crystals in the presence of dicalcium phosphate dehydrate was studied, using in situ AFM techniques.

The macroscale electrochemical theory breaks down with microstructures smaller than the dimensions of the diffusion layer, showing that such electrodes have significant quantitative effects and qualitative advantages. The great advantage of microelectrodes over macroelectrodes is the minimisation of interference, which gives rise to much lower detection limits. Microelectrodes have much reduced ohmic drops and capacitive effects and can be used in the absence of supporting electrolyte. These features have opened a growing interest in the fabrication and application of microelectrodes in various areas. There are different microelectrode geometries, but disc type is the most used. Microelectrode arrays have been proposed as a way of increasing the magnitude of the current (produced for a single microelectrode), while maintaining the advantages of the single microelectrode. Although the inlaid microdisc microelectrode can be considered as one the most popular microelectrode geometry, there is also a need to consider conical recessed, recessed and protruding microdiscs as photolithographic microfabrication techniques often result in non-ideal geometries. It has been proved using surface imaging techniques such as scanning Kelvin nanoprobe (SKN), scanning electron microscopy (SEM) and white light interferometer microscopy that conical recessed electrodes with gradient potential along the recessed walls are formed during standard photolithographic methods for producing microelectrode arrays. Microarrays are ubiquitously used for high-throughput measurements using various signal transduction techniques. Ideally each sensor in a microarray platform should perform optimally to ensure an error free response. In this thesis, a simple method for designing a microelectrode array platform (MEA) is described, allowing a ‘defective’ cluster of sensing arrays to be easily identified. It is possible to extend this concept for multiple analyses on a single chip. Molecular electronic is a promising technology which would be an alternative. The concept of molecular electronics is the use of single molecules or arrays, or layers of molecules for the fabrication of electronic components such as wires, switches, and storage elements. Indeed, functionalised thiol monolayer-based microelectrode array may provide unique possibilities, facilitating electrochemical measurements involving electron transfer via electron tunnelling. The conjugated structure of rigid, linear molecule increases greatly the rate of electron transfer across the monolayer. Charge transfer and self-assembly characteristics of novel fully conjugated molecules molecular wires (synthesised at the Department of Chemistry and Centre for Molecular and Nanoscale Electronics, Durham University) assembled on flat gold electrodes are evaluated using Marcus model of electron-transfer and tunnelling theory. The behaviour of these wires is compared with heptanethiol and dodecanethiol SAMs. A preliminary study for application of self-assembled monolayer of molecular wires in microelectrode arrays for multiple analyses on a single chip has been successfully reached.

The work in this thesis investigated the effects of soot contaminated lubricants of engine components. A thorough background review demonstrated that soot related wear is a major issue for the automotive and lubricants industry. A detailed analysis of the physical properties and effects of soot contaminated lubricants highlighted that there are associated effects that will tend to reduce engine perfonnance and efficiency. The actual wear that was produced is studied for the area of the engine which is most significantly affected by soot contamination, the valve train. A typical elephant's foot to valve tip contact, known to suffer from soot related wear, fonned the basis of the specimen ball-on-flat reciprocating wear testing. A standardised wear test rig and method were developed for the testing, which investigated different lubricants (base and fonnulated oil), increasing levels of soot contamination (using carbon black as a soot surrogate) and different temperatures. The results demonstrated significant increases in wear with increasing level of carbon black contamination. Furthennore, increased temperature tended to increase the amount of wear produced and using a fonnulated lubricant reduced the amount of wear measured when compared to tests using base oil. Significant changes in wear mechanism were visible from surface imaging ofthe wear scars, showing initially lubricated sliding, which changes to abrasion at higher contamination levels, and then shifting to contact starvation as the contamination significantly reduces the flow of lubricant into the contact at very high contamination levels. Significantly, the severity of the effects of soot contamination was due to the lubricant film thickness in the contact and therefore ultimately the lubrication regime within which it is operating. Where boundary lubrication is significantly affected by soot contaminated lubricants, but these effects are reduced when the contact operates under elastohydrodynamic (EHD) lubrication conditions. A region of the engine that is significantly affected by soot contaminated oil is the contact between the piston and the cylinder wall or liner. This is mainly due to the component's proximity to the area where soot in produced. Wear will occur in this highly sensitive region due to the breakdown of the protective oil film, which will occur when the lubricant is contaminated with soot. A method of analysing the effect sO~as been investigated 'using an ultrasonic technique to measure the oil film between a piston and a cylinder wall or liner. The ultrasonic oil film thickness measurement technique (developed at the University of Sheffield) has been used in many static and dynamic applications; therefore an initial trial was performed on a single cylinder engine, demonstrating some success. A motored test engine was then built on which to develop the technique and to provide a platform for future research. The test engine demonstrated potential for future success, as a variety of ultrasonic transducers were tested. Testing also highlighted that significant future work, regarding reducing electrical interference, improving the data processing electronics and further investigations into the different types of transducer is required to improve the technique.

My thesis work focuses on the integration of scanning tunneling microscopy with infrared spectroscopy, to provide unprecedented �-scale resolution in surface imaging with spatially correlated chemical specificity. Scanning probe techniques generally lack chemical information. Inspired by recent advances coupling optical spectroscopies with scanning probe microscopies, I have developed a nanoscale infrared spectroscopic imaging method applying scanning tunneling microscope probe tips as nanoamplifiers to obtain multiplexed molecular vibrational signals utilizing a Fourier transform interferometer at room temperature and ambient pressure. The sensitivity of the tunneling junction and nanoscale probe area enables the measurement of vibrational spectra orders of magnitude below the diffraction limit. I substantiated the effectiveness of this instrument by designing an air- and temperature-stable model system characterized by infrared absorption that couples to the electronic states of the gold substrate. Specifically, aurous cyanide (AuCN) self-assembled monolayers satisfy these requirements with the added benefit that its IR absorption lies outside of the carbon dioxide and water windows, thereby maintaining high signal-to-noise ratios for these experiments. These atomically pristine hexagonal close-packed AuCN monolayers exhibit a strong absorption at 2140 cm−1. Upon thermal annealing, the surface rearranges into a ribbon structure with a blue-shifted absorption to 2230 cm−1. The unique vibrational contrast in AuCN monolayers resulting from thermally induced structural changes serves as an ideal model system for the new infrared scanning tunneling microscope (IR-STM). Upon prolonged vapor deposition, the self-assembled cyanide monolayers reconfigure into large-scale AuCN crystals, giving two distinct morphologies and significantly different vibrational modes, compared to the AuCN monolayer structures. Once again, temperature can tune gold-cyanide orientation and long-range ordering. This work provides new insights for controlled surface-mediated crystal growth in AuCN systems. Ultimately, combining with the chemical information gained from the developed IR-STM, surface-mediated growth will enable new methodologies for fabricating next-generation nanoscale semiconductors. Nanoscale semiconductors based on AuCN that are similar to nanoribbon structures have been demonstrated to be useful for nanoelectronics as well as in catalytic applications.

The facts that seismic body-wave types are sensitive to different physical properties, seismic sources radiate polarized waves, and seismic receivers are sensitive to the polarization of scattered body-waves and coherent noise, mean that it is important to consider recording and analyzing different wave-types and data components prior to high-resolution reflection surveys. In this dissertation, important aspects of elastic-wave propagation relevant to high-resolution multicomponent surveying have been analyzed experimentally and numerically, and methodologies have been tested and developed that will improve near-surface imaging and characterization. Factors affecting the ability of common-mode P- and S-wave reflection surveys for mapping features in the near-surface are described and illustrated through analyses of experimental field data and modeling. It is demonstrated through comparisons of known subsurface conditions and processed stacked sections, that combined P- and S-wave common-mode reflection information can allow a geologic sequence to be imaged more effectively than by using solely P- or S-wave reflection information. Near-surface mode-converted seismic reflection imaging potential was tested experimentally and evaluated through modeling. Modeling results demonstrate that potential advantages of near-surface mode-conversion imaging can be realized in theory. Analyses of acquired multicomponent data however demonstrate that mode-conversion imaging could not be accomplished in the field study area, due to the low amplitudes of events and the presence of noise in field data. Analysis methods are presented that can be used for assessing converted-wave imaging potential in future reflection studies. Factors affecting the ability of SH-wave reflection measurements for allowing near-surface interfaces and discontinuities to be effectively imaged are described. A SH-wave reflection data analysis workflow is presented that provides a methodology for delineating active subsidence areas of the subsurface. Equations that define an incidence angle for which the SH-wave reflection coefficient is zero are also presented. In one appendix a computer program developed for the application of equations describing elastic-wave scattering from planar interfaces is presented. In another appendix, it is shown that EM-wave velocity and amplitude information can be used to infer near-surface media distribution and subsidence activity between boreholes. Data acquisition considerations and data analysis workflows for cross-hole radar measurements are also presented. The facts that seismic body-wave types are sensitive to different physical properties, seismic sources radiate polarized waves, and seismic receivers are sensitive to the polarization of scattered body-waves and coherent noise, mean that it is important to consider recording and analyzing different wave-types and data components prior to high-resolution reflection surveys. In this dissertation, important aspects of elastic-wave propagation relevant to high-resolution multicomponent surveying have been analyzed experimentally and numerically, and methodologies have been tested and developed that will improve near-surface imaging and characterization. Factors affecting the ability of common-mode P- and S-wave reflection surveys for mapping features in the near-surface are described and illustrated through analyses of experimental field data and modeling. It is demonstrated through comparisons of known subsurface conditions and processed stacked sections, that combined P- and S-wave common-mode reflection information can allow a geologic sequence to be imaged more effectively than by using solely P- or S-wave reflection information. Near-surface mode-converted seismic reflection imaging potential was tested experimentally and evaluated through modeling. Modeling results demonstrate that potential advantages of near-surface mode-conversion imaging can be realized in theory. Analyses of acquired multicomponent data however demonstrate that mode-conversion imaging could not be accomplished in the field study area, due to the low amplitudes of events and the presence of noise in field data. Analysis methods are presented that can be used for assessing converted-wave imaging potential in future reflection studies. Factors affecting the ability of SH-wave reflection measurements for allowing near-surface interfaces and discontinuities to be effectively imaged are described. A SH-wave reflection data analysis workflow is presented that provides a methodology for delineating active subsidence areas of the subsurface. Equations that define an incidence angle for which the SH-wave reflection coefficient is zero are also presented. In one appendix a computer program developed for the application of equations describing elastic-wave scattering from planar interfaces is presented. In another appendix, it is shown that EM-wave velocity and amplitude information can be used to infer near-surface media distribution and subsidence activity between boreholes. Data acquisition considerations and data analysis workflows for cross-hole radar measurements are also presented.

Archaeological materials science or archaeometry is the scientific study of material culture, which plays an important role in the development and interpretation of archaeological theory by establishing links between an object's materiality and its societal context. Driven by the complex nature of archaeological materials and the necessity to improve analysis, interpretation, and access of material culture and scientific research in the field, in the last decade there has been a significant advancement in instrumentation development for rapid, non-invasive and high-specificity materials characterization. To this end, imaging spectroscopy and portable chemical sensing modalities have played a revolutionary role in the identification and chemical mapping of constituent materials in ancient and historical wall paintings and other immovable artifacts. In this research, different imaging and spectroscopic modalities are explored: direct-detection terahertz (THz) imaging, hyperspectral imaging spectroscopy (HSI), and high-resolution scanning reflectance spectroscopy. First, a novel direct-detection THz imaging system, adopted from biomedical imaging applications, was used to probe hierarchically-complex painting targets for sub-surface imaging of hidden decorative features and structural defects that are difficult to discern by X-ray and infrared imaging techniques. The imaging system’s deep signal penetration depth and high contrast sensitivity can successfully penetrate overlaying layers of strong signal scatterers such as lead white and chalk and to identify internal voids, hidden text, and topographic details of concealed iconography, which has important implications for future applications of this system on the study of wall paintings covered by whitewash or plaster layer(s).Investigations of two different collections of painted artifacts were performed using novel imaging spectroscopy applications, supplemented by forensic photography and portable chemical sensing modalities, fiber-optic reflectance spectroscopy (FORS) and X-ray fluorescence (XRF) spectroscopy: (1) Cypriot wall paintings, and (2) Greco-Roman funerary portraits from Egypt. A comprehensive in situ characterization of Hellenistic, Roman and Byzantine Cypriot wall paintings in the region of Paphos, Cyprus was achieved for the first time, applying a non-invasive multi-scale approach, employing a commercial hyperspectral imaging (HSI) camera operated in reflectance and luminescence modes and a custom-made high-resolution scanning reflectance spectroscopy system developed and adapted for field research. The HSI and the scanning reflectance spectroscopy system offered complementary, powerful high-spectral and spatial resolution 3D data cubes to reconstruct the palette of Cypriot painters. From an archaeological materials science perspective, the characterization and mapping of pigments through derivative spectral analysis provided important information on pigment layering and mixtures used to produce complex hues and special optical effects, such as shading and translucency. Combined with FORS and XRF, these techniques offered fast, in-depth studies of large painted surfaces, inferring material and artistic choices and the chaine operatoire of production technology. Similarly, the analysis of funerary portraits of ancient Egypt (first to fourth century AD) identified technological choices, materials selection and application methodology, revealing the vogue of Greco-Roman society. From a materials engineering perspective, the study of these paintings lead to adaptations and development of novel methods of analysis: luminescence imaging spectroscopy was for the first time employed to collect and map luminescence signatures of Egyptian blue and madder lake, two of the most important synthetic pigments of antiquity, over painting surfaces; and the success of forensic and spectral imaging in producing luminescence/chemical maps across 2D surfaces led to the development of a streamlined, accessible methodology to construct luminescence-textured 3D models for new visualizations and analyses of high-relief/3D polychrome artifacts that feature photoluminescent pigments and conservation materials.

The quality of continuous fiber reinforced polymer matrix composite parts and structures depends strongly on the friction during the composite forming process. The two major types of friction that cause deformations during this process are ply-ply friction and tool-ply friction. One of the challenges in the composite forming process is the occurrence of wrinkling and shape distortion of the fabric caused by the surface differences between the forming tool and surface of the laminate. Frictional measurements of composites can vary widely depending on processing parameters, measurement technique, and instruments used. In this study, a commercial rheometer was used to evaluate tool-ply friction of unidirectional carbon fiber epoxy prepreg at various contact pressures, temperatures and sliding velocities. Viscoelastic properties such as the complex viscosity (η*), storage modulus (G'), loss modulus (G"), and loss factor (tan δ) were used to determine the critical transition events (such as gelation) during cure. An understanding of changes in viscoelastic properties as a function of time, temperature, and cure provides insight for establishing a suitable processing range for compression forming of prepreg systems. Surface imaging results were coupled with rheological results to qualitatively examine the effects of processing parameters on prepreg distortions. Changes in gap height over the measurement interval qualitatively describe the changes in contact area and contact mechanisms between the tool-ply surfaces. The results indicate that friction behavior of the prepreg system is a contribution of adhesive and frictional forces, where increase in viscosity, reduction in gap height, and cure of the sample correlate to higher friction values.

The nanogap voltammetry based on Scanning Electrochemical Microscopy (SECM) can monitor and study fast electron transfer (ET) reaction on macroscopic substrates of interest. The understanding of the electrochemical reactivity of carbon nanomaterials is of great importance not only for the application purposes, but also for fundamental electrochemistry. There are controversies about how the electronical reactivity of these materials depend on the electronic structures, defects and contamination. One theme of my PhD work is to study the electrochemical reactivity of various carbon nanomaterials using nanogap voltammetry based on SECM. On the other hand, SECM at nanometer scale is a powerful technique, with unique advantages and unprecedented measurement capabilities, such as very high spatial resolution for surface imaging. However, it has been challenging to reliably characterize the size and geometry of the nanometer-size electrodes. The other aim of my PhD work is the development of methods for fabricating and characterizing nanoelectrodes for SECM. Therefore, this thesis is based on two sections. In the first section, I fabricate graphene electrodes based on graphene grown by chemical vapor deposition, and apply nanogap voltammetry to study the ultrafast ET kinetics at graphene. I also study the ultrafast ET kinetics at highly ordered pyrolytic graphite (HOPG) with nanogap voltammetry. In the second section, I develop carbon nanoprobes with high electrochemical reactivity and well-controlled size and geometry based on chemical vapor deposition of carbon in quartz nanopipets. I also characterized the size and geometry of the nanopipets that support interfaces between two immiscible electrolyte solutions (ITIES). I then prove the utility of such nanopipets by the SECM imaging on 100 nm diameter Si3N4 nanopores.

The reliability of flexible electronic devices needs to be characterized to ensure that these devices can function after repeated stretching and bending. Many of these devices contain metallic films bonded to polymer substrates. This research is therefore focused on understanding the electrical performance and mechanical behavior of these incorporated metallic thin films. Some work has already been published in this area that has provided insight on both when mechanical failure occurs in the metallic film (cracking or delamination) and also identified when through-thickness cracks initiate and/or propagate. Other studies have monitored in situ resistance measurements to determine when electrical performance decreases or ceases. Contributions have detailed how different methods of straining, such as monotonic tensile straining, uniaxial cyclic tensile straining, and bending fatigue, influence the electrical performance. These contributions have primarily focused on Cu films, and this body of work extends the prior work to also include Ag films. This study explores the effects of an adhesion layer (Ti), the magnitude of film thickness (200 to 1,800 nm), and substrate (Kapton, PEN, PET) on the electro-mechanical performance of sputtered Ag films. The electrical performance (resistance) of Ag films was measured during monotonic and cyclic in situ tensile testing and also before and after bending. Analysis of the electrical resistance and surface imaging was conducted in an effort to correlate mechanical failures to the electrical behavior. The normalized resistance results showed that the inclusion of an adhesion layer could be detrimental to the electro-mechanical behavior of the Ag films in tensile testing, but not always during bending. It was also observed that changing the film thickness between 200 nm and 1,800 nm also affects the electrical and/or mechanical behavior of the films in different straining modes. In monotonic tensile testing, the inclusion of the adhesion layer increased the crack density observed in the Ag films, but there was no evident influence of film thickness. However, in cyclic fatigue testing, both the inclusion of an adhesion layer and changing the film thickness were separately observed to effect the cracking behavior in the films and the normalized resistance profiles from the 900 nm Ag films. When examining films subjected to bending fatigue tests, a difference in the cracking behavior of the films was observed. It was seen that film thickness and an adhesion layer affected the performance to different degrees. The types of cracks and deformation present in the Ag film were observed to be dependent on the inclusion of an adhesion layer. In some cases, linear crack density in 900 nm Ag films was also measured to be lower for films with an adhesion layer, but in 200 nm Ag films cracks only appeared in films with an adhesion layer with larger crack densities than 900 nm Ag films. When model PVD Ag films were compared to printed Ag, there was a marked difference between cyclic and monotonic behavior of the PVD films and printed films. The electrical performance in printed films appeared to degrade at much lower strains than PVD Ag films in monotonic tests. In cyclic tensile tests, the printed films were observed to have a different normalized resistance profile over cycles than PVD films with the same maximum strain. For all tests performed on printed Ag, the films exhibited brittle cracking facilitated by pores and did not always propagate perpendicular to the straining direction. These differences in electro-mechanical behavior may be attributed to many factors including the film structure resulting from the printing process, surface defects, residual polymer from printing, or ink composition.

The fundamental behaviour of photocatalysts is very crucial for determining photoactivity. This thesis aims to investigate the physical, optical, and electronic properties of two semiconductor materials, ZnS and GaP, with the aim of optimizing their performance as visible-light active photoelectrodes. ZnS and GaP thin films are synthesized by pulsed laser deposition. The physical properties, such as crystal structure and surface morphology, are studied by x-ray diffraction and surface imaging techniques (e.g. scanning electron microscopy and atomic force microscopy). The role of defect and dopant states is assessed through analysis of the optical properties as well as electronic structure calculations using density functional theory. The application of the thin films in photoelectrochemical cells for water splitting is demonstrated and the effect of the physical and optical properties on photoelectrochemical performance is discussed. Compared with the individual semiconductor materials, the combination of both ZnS and GaP in a multilayer thin film is found to create a new route to significantly increase the visible-light photoelectrochemical activity. Overall, this thesis demonstrates the potential application of ZnS and GaP thin films for highly efficient photoelectrodes under visible light.

The treatment and desalination of inland water via reverse osmosis (RO) technology is gaining momentum for upgrading brackish groundwater and developing supplemental fresh water for various regions. In brackish RO plants, high water recovery is critical in order to minimize the volume of residual RO concentrate (brine), given the economic and environmental challenges of concentrate management. However, high recovery may be limited by mineral salt scaling resulting from supersaturation of sparingly soluble minerals (e.g., CaSO4, BaSO4, CaCO3, SiO2). Mineral scaling results in membrane surface blockage, reduction of permeate flux and shortening of membrane lifetime.In order to control or prevent mineral scaling, effective mitigation methods must be developed and tested (i.e., the relationship between RO operating conditions and mineral scaling). To accomplish the above, early detection of mineral scaling is essential. To meet the above challenges, a novel high-pressure RO membrane monitoring system was developed to allow direct membrane surface imaging. The membrane monitoring system (MMS) was interfaced with a slipstream from an RO plant, whereby captured membrane surface images were analyzed online. The present monitoring approach demonstrated, for the first time, early detection of silica scale formation and growth kinetics. Detailed silica scaling studies revealed that scaling consisted of discrete silica particles embedded in a silica “gel” layer. The membrane monitoring approach also served to evaluate the impact of a membrane biofilm on concentration polarization (CP) and mineral scaling kinetics. It was shown that biofilms enhanced CP within the biofilm and significantly exacerbated mineral scaling. The membrane monitoring approach was subsequently deployed in a field study of desalination of brackish agricultural drainage (AD) water. In these studies, the membrane monitor was integrated with a mobile RO pilot plant, developed at UCLA, for real-time field optimization of RO operating conditions for averting mineral scaling. The above approach demonstrated that effective feed filtration for removal of suspended particles is critical for mitigating mineral scaling and reducing nucleation triggered by surface deposited particles. Moreover, antiscalant selection and dosage optimization was feasible under field conditions which also enabled determination of the maximum feasible water recovery level.

The strong light trapping properties of Silicon Nanowires have attracted much interest in the past few years for the conversion of sun energy into conventional electricity. Studies have been completed for many researchers to reduce the cost of fabrication and reflectance of solar light in these nanostructures to make a cheaper and more efficient solar cell technology by using less equipment for fabrication and employing different materials and solution concentrations. Silver, a conducting and stable metal is used these days as a precursor to react with silicon and then form the nanowires. Its adequate selection of solution concentration for a size of silicon substrate and the treatment for post-cleaning of silver dendrites make it a viable method among the others. It is an aim of this research to obtain significant low reflectance across the visible solar light range. Detailed concentration, fabrication and reflectance studies is carried out on silicon wafer in order to expand knowledge and understanding. In this study, electroless etching technique has been used as the growth mechanism of SiNWs at room temperature. Optimum ratios of solution concentration and duration for different sizes of exposed area to grow tall silicon nanowires derived from experimentation are presented. Surface imaging of the structures and dimension of length and diameter have been determined by Scanner Electron Microscopy (SEM) and the reflectance in the optical range in silicon nanowires has been make using UV-Visible Spectrophotometer.

Current x-ray technologies provide security personnel with non-invasive sub-surface imaging and contraband detection in various portal screening applications such as checked and carry-on baggage as well as cargo. Computed tomography (CT) scanners generate detailed 3D imagery in checked bags; however, these scanners often require significant power, cost, and space. These tomography machines are impractical for many applications where space and power are often limited such as checkpoint areas. Reducing the amount of data acquired would help reduce the physical demands of these systems. Unfortunately this leads to the formation of artifacts in various applications, thus presenting significant challenges in reconstruction and classification. As a result, the goal is to maintain a certain level of image quality but reduce the amount of data gathered. For the security domain this would allow for faster and cheaper screening in existing systems or allow for previously infeasible screening options due to other operational constraints. While our focus is predominantly on security applications, many of the techniques can be extended to other fields such as the medical domain where a reduction of dose can allow for safer and more frequent examinations. This dissertation aims to advance data reduction algorithms for security motivated x-ray imaging in three main areas: (i) development of a sensing aware dimensionality reduction framework, (ii) creation of linear motion tomographic method of object scanning and associated reconstruction algorithms for carry-on baggage screening, and (iii) the application of coded aperture techniques to improve and extend imaging performance of nuclear resonance fluorescence in cargo screening. The sensing aware dimensionality reduction framework extends existing dimensionality reduction methods to include knowledge of an underlying sensing mechanism of a latent variable. This method provides an improved classification rate over classical methods on both a synthetic case and a popular face classification dataset. The linear tomographic method is based on non-rotational scanning of baggage moved by a conveyor belt, and can thus be simpler, smaller, and more reliable than existing rotational tomography systems at the expense of more challenging image formation problems that require special model-based methods. The reconstructions for this approach are comparable to existing tomographic systems. Finally our coded aperture extension of existing nuclear resonance fluorescence cargo scanning provides improved observation signal-to-noise ratios. We analyze, discuss, and demonstrate the strengths and challenges of using coded aperture techniques in this application and provide guidance on regimes where these methods can yield gains over conventional methods.

Theoretical and numerical modeling of optical systems are increasingly being utilized in a wide range of areas in physics and engineering for characterizing and improving existing systems or developing new methods. This dissertation focuses on determining and improving the performance of imaging and non-imaging optical systems through modeling and developing model-aware enhancement methods. We evaluate the performance, demonstrate enhancements in terms of resolution and light collection efficiency, and improve the capabilities of the systems through changes to the system design and through post-processing techniques. We consider application areas in integrated circuit (IC) imaging for fault analysis and malicious circuitry detection, and free-form lens design for creating prescribed illumination patterns. The first part of this dissertation focuses on sub-surface imaging of ICs for fault analysis using a solid immersion lens (SIL) microscope. We first derive the Green's function of the microscope and use it to determine its resolution limits for bulk silicon and silicon-on-insulator (SOI) chips. We then propose an optimization framework for designing super-resolving apodization masks that utilizes the developed model and demonstrate the trade-offs in designing such masks. Finally, we derive the full electromagnetic model of the SIL microscope that models the image of an arbitrary sub-surface structure. With the rapidly shrinking dimensions of ICs, we are increasingly limited in resolving the features and identifying potential modifications despite the resolution improvements provided by the state-of-the-art microscopy techniques and enhancement methods described here. In the second part of this dissertation, we shift our focus away from improving the resolution and consider an optical framework that does not require high resolution imaging for detecting malicious circuitry. We develop a classification-based high-throughput gate identification method that utilizes the physical model of the optical system. We then propose a lower-throughput system to increase the detection accuracy, based on higher resolution imaging to supplement the former method. Finally, we consider the problem of free-form lens design for forming prescribed illumination patterns as a non-imaging application. Common methods that design free-form lenses for forming patterns consider the input light source to be a point source, however using extended light sources with such lenses lead to significant blurring in the resulting pattern. We propose a deconvolution-based framework that utilizes the lens geometry to model the blurring effects and eliminates this degradation, resulting in sharper patterns.

Hydraulic fracturing, which is a fast-developing well-stimulation technique, has greatly expanded oil and natural gas production in the United States. As the use of hydraulic fracturing has grown, concerns about its environmental impacts have also increased. A sub-surface imaging radar that can detect the extent of hydraulic fractures is highly demanded, but existing radar designs cannot meet the requirement of penetration range on the order of kilometers due to the exorbitant propagation loss in the ground. In the thesis, a medium frequency (MF) band sub-surface radar sensing system is proposed to extend the detectable range to kilometers in rock layers. Algorithms for cross-hole and single-hole configurations are developed based on simulations using point targets and realistic fractured rock models. A super-miniaturized borehole antenna and its feeding network are also designed for this radar system. Also application of imaging radars for sub-surface sensing frozen lakes at Arctic regions is investigated. The scattering mechanism is the key point to understand the radar data and to extract useful information. To explore this topic, a full-wave simulation model to analyze lake ice scattering phenomenology that includes columnar air bubbles is presented. Based on this model, the scattering mechanism from the rough ice/water interface and columnar air bubbles in the ice at C band is addressed and concludes that the roughness at the interface between ice and water is the dominate contributor to backscatter and once the lake is completely frozen the backscatter diminishes significantly. Radar remote sensing systems often require high-performance antennas with special specifications. Besides the borehole antenna for MF band subsurface imaging system, several other antennas are also designed for potential radar systems. Surface-to-borehole setup is an alternative configuration for subsurface imaging system, which requires a miniaturized planar antenna placed on the surface. Such antenna is developed with using artificial electromagnetic materials for size reduction. Furthermore, circularly polarized (CP) waveform can be used for imaging system and omnidirectional CP antenna is needed. Thus, a low-profile planar azimuthal omnidirectional CP antenna with gain of 1dB and bandwidth of 40MHz is designed at 2.4GHz by combining a novel slot antenna and a PIFA antenna.

Atomic force microscopes (AFMs) are used in many nanopositioning applications in order to measure the topography of various specimens at an atomic level through surface imaging. The imaging of samples in AFMs is carried out by using a three degree-of-freedom positioning unit called a piezoelectric tube scanner (PTS). The majority of the commercially available AFMs use PTS for x, y and z positioning because of its simplicity, large achievable scan range (>100 um) and smaller capacitance. In spite of having such good qualities, there are some limitations of the PTS which adversely affect the scanning speed and limit the overall performance of the AFM. The PTS of the AFM suffers from the problem of vibration, cross coupling effects between the axes of the scanner and nonlinear effects such as creep and hysteresis. This thesis presents several ways to compensate for the above mentioned problems of the PTS to improve the speed and accuracy of the PTS for high speed atomic force microscopy using robust control. The first contribution of this dissertation is the design of damping controllers to compensate for the effect of vibrations induced by the PTS. The first design uses a damping controller namely the resonant controller to damp the first resonant mode of the scanner. The design of the controller is presented both in single-input single-output (SISO) and multiple-input multiple-output (MIMO) forms. Experimental results show that the resonant controller significantly damps the first resonant mode of the scanner. One of the limitations of the use of the resonant controller is its high pass nature. The high pass nature of the resonant controller may add high frequency sensor noise and destabilise the system if there are unmodelled high frequency dynamics. In order to make the system robust to high frequency dynamics we next propose the design of a passive damping controller to damp the resonant modes of the scanner. The motivation to design a passive damping controller for the PTS is its bandpass nature. The bandpass nature of the passive damping controller not only reduces the addition of high frequency sensor noise but also results in large gain and phase margins. In order to design the passive damping controller for the PTS we have proposed a new analytical framework. The analytical framework examines the finite gain stability for a positive feedback interconnection between two stable linear systems where one system has mixed negative-imaginary (NI), passivity, and smallgain properties and the other system has mixed NI, negative-passivity (NP) and small-gain properties. The closed-loop system with this passive damping controller is robust against changes in the plant dynamics. Although the closed-loop system using the passive damping controller is robust, the performance of this controller is not same for all possible changes in plant dynamics. In order to achieve robust performance against changes in the plant dynamics, we propose another damping controller namely a minimax linear quadratic Gaussian (LQG) controller to compensate for induced vibrations in the PTS. This type of controller not only provides robust performance against changes in the plant dynamics but also results in large gain and phase margins. Due to its bandpass nature the minimax LQG controller also reduces the addition of high frequency sensor noise. A second contribution of this thesis is the design of an integral minimax LQG controller to improve the tracking performance of the PTS. The tracking accuracy of the PTS is hampered due to the low resonance frequency of the PTS. Here, we have proposed the design of a minimax LQG controller with integral action to track the reference triangular signal used for raster scanning in most commercial AFMs. The design of the controller includes uncertainty which arises due to the spill over dynamics of the system at high frequencies. Experimental results are compared with an integral controller to demonstrate the effectiveness of the proposed controller. The experimental results show that the integral minimax LQG controller achieves four times better performance as compared to the integral controller. The third and final contribution of this thesis is the design of a multi-variable controller for damping, tracking and cross coupling reduction of PTSs. At first we propose a design of multi-variable NI controllers for damping and cross coupling reduction of the PTS using a resonant and an integral resonant controller. Secondly, we propose a design of a double resonant controller with integral action to damp the resonant mode of the scanner, reduce the cross coupling effects of the scanner and improve the tracking performance of the PTS. The design of controllers in this case is done using a reference model matching approach. In all cases a performance comparison is made by implementing the controllers on the PTS. Experimental results presented in the thesis show that the proposed controllers provide significant improvement in the performance of the AFM.

Abstract: Traditional genetically-encoded imaging strategies are problematic for use in analysing cell surface interactions due to the heterogeneous nature of the cell surface, and the high level of post-translational modifications. Small molecule fluorophores can provide dynamic information on cell surface interactions due to their small size, low detection limits and environmental sensitivity. Recent advances in bioconjugate strategies such as the Staudinger ligation, Sharpless-Meldal reaction and periodate oxidation with aniline-catalyzed ligation (PAL) and hydrazone/oxime forming reactions have imparted improved specificity. However, there remains a need for chromophores with improved specificity. This thesis describes the synthesis and application of novel chromophores for cell surface imaging. We employed selective labelling strategies to combat background signal, and enable detection of specific post-translational modifications. We generated a small library of alkynyl coumarin profluorophores and characterized the corresponding alkyne and triazole derivatives. We observed increased fluorescence emission quantum yields of up to 9-fold and bathochromic shift of up to 23 nm due to the formation of the triazole linkage. Although these dyes are useful for fluorogenic labelling strategies, their relatively low brightness and short excitation wavelength inspired us to examine a new series of alkynyl and azido benzoxadiazole fluorophores for labelling cell surface glycoconjugates. We were able to identify reactive chromophores which act as fluorogenic, quenched, and static fluorescent labels. The fluorogenic dye showed an almost 50-fold increase of intensity, and the quenched dyes showed up to 500-fold loss of intensity. To quantify sialic acid content, using PAL methodology, we developed a novel 4-aminooxy-7-nitro- benzoxadiazole (NBDAO) fluorophore, and compared its performance with commercially available dyes. NBDAO was excited by a 488 nm laser line and found to be suitable for in vitro and in vivo labelling studies using SDS-PAGE, microplate assays, fluorescence spectroscopy, and flow cytometry. As well, a series of bioorthogonal cyanine-5 fluorophores and choline derivatives were synthesized and examined for suitability in phospholipid metabolic labelling experiments. Propargyl- and azido- choline readily incorporated as metabolic labels of phospholipids. However, a carbonyl-choline analog did not show any incorporation. The Cy 5 dyes were found to have exceptionally high absorption coefficients and long-wavelength absorption and emission.

Growing demand for clean source of energy in the recent years has increased the manufacture of solar cells for converting sun energy directly into electricity. Research has been carried out around the world to make a cheaper and more efficient solar cell technology by employing new architectural designs and developing new materials to serve as light absorbers and charge carriers. Aluminum doped Zinc Oxide thin film, a Transparent conductive Oxides (TCO) is used as a window material in the solar cell these days. Its increased stability in the reduced ambient, less expensive and more abundance make it popular among the other TCO’s. It is the aim of this work to obtain a significantly low resistive ZnO:Al thin film with good transparency. Detailed electrical and materials studies is carried out on the film in order to expand knowledge and understanding. RF magnetron sputtering has been carried out at various substrate temperatures using argon, oxygen and hydrogen gases with various ratios to deposit this polycrystalline films on thermally grown SiO2 and glass wafer. The composition of the films has been determined by Xray Photoelectron Spectroscopy and the identification of phases present have been made using X-ray diffraction experiment. Surface imaging of the film and roughness calculations are carried out using Scanning Electron Microscopy and Atomic Force Microscopy respectively. Determination of resistivity using 4-Probe technique and transparency using UV spectrophotometer were carried out as a part of electrical and optical characterization on the obtained thin film.The deposited thin films were later annealed in vacuum at various high temperatures and the change in material and electrical properties were analyzed.

Nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) are well established techniques. Both require samples to be placed inside spatially-homogeneous static magnetic and radio frequency magnetic fields. This research focuses on applying the principles of NMR spectroscopy and imaging to design a system that can produce images of the NMR signal from a sample placed adjacent to it. The long term goal is to image at distances of meters from the device. The specific application of interest is locating buried utilities in fully-hydrated soils by identifying non-signal bearing features in an NMR signal rich background. This thesis asserts that a minimum of three questions need to be answered to determine if near surface MRI is feasible. 1.) Can the Earth's magnetic field (BEarth) be used as the applied static magnetic field? 2.) Is the NMR signal from the water found in fully-hydrated soils sufficient for imaging? 3.) Can a near-surface imaging technique be developed? This thesis research attempts to answer each of these questions in three stand alone investigations: 1.) In situ measurements of BEarth, 2.) laboratory-based relaxation studies of synthetic sands, and 3.) the development of a proof-of-concept near-surface magnetic resonance imaging device. It is the assertion of this thesis that the results of these three studies are needed to begin to properly understand the signal space that a viable surface instrument would have to operate within for practical use. The BEarth results showed that better selection performance would be achieved using a larger B0 field. The synthetic sands study gave results suggest that relaxation behavior of water was highly deterministic based on particle diameter. The imaging performance of the unilateral MRI device was measured and the results demonstrate that imaging at depths on the order of one centimeter is possible. Overall, the results from these three studies have advanced the understanding of near-surface inhomogeneous magnetic resonance, while giving strong indications that near-field MRI in fully-hydrated soil is promising.

The move towards 157 nm as the next generation of photolithography has presented many challenges. One of the more challenging aspects of 157 nm photolithography is the development of a suitable photoresist. Two of the issues faced when designing a suitable resist for 157 nm applications are transparency requirements and outgassing from the photoresist. Designing a resist to not intentionally outgass upon exposure to acid and heat employed the screening of several new potential solubility switches. Several lactones were synthesized and NMR was used as a spectroscopic method to monitor whether the desired solubility switch occurred in model compounds. Successful model compounds were incorporated into polymers to form a photoresist. Subsequent imaging experiments gave insight into the desired copolymer ratios needed for imaging applications. The formation of base insoluble lactones from base soluble precursors were also investigated for use as a non-outgassing negative tone photoresist. Successful model compounds were incorporated into copolymers. Imaging experiments gave insight on the terpolymer ratios needed for to obtain imaging. Transparency of the polymer resin has been a major hurdle in the development of a 157 nm photoresist. Efforts to use top surface imaging (TSI), an alternative lithographic patterning technique have been explored. TSI, unlike traditional photolithographic schemes, does not require a transparent resin. However, line edge roughness (LER) has always hampered the feasibility of TSI. Efforts to reduce the LER of TSI through manipulation of the Tg of the polymer resin were investigated.

The process of cationic graft polymerization lithography was developed at The University of Texas at Austin. This process is a top surface imaging scheme that involves using photogenerated acid to initiate the graft polymerization of a gas phase monomer onto a surface. This technique relies on the cationic initiation of polymerization and, hence, is limited to a certain set of monomers and initiators. There are very few photoacid generators strong enough to initiate cationic polymerization. Also, the amount of photoacid generator that can be added to a polymer film is limited by its solubility in the film. Furthermore, only vinyl ethers and epoxides have been found to be active towards this type of polymerization. Because of these limitations, an alternate, free radical based scheme for graft polymerization lithography was desired. Free radical graft polymerization lithography would allow a multitude of initiators to be used, including polymer bound initiators. It would also allow access to a new set of monomers. This document describes the development of a free radical graft polymerization lithography scheme. Custom synthesis of both the initiator and monomer, design and automation of the grafting chamber, studies of grafting kinetics, and imaging experiments are described. This dissertation also describes fundamental research into the function of base in photoresists. As critical dimensions in microlithography become ever smaller and the importance of line-edge roughness becomes more pronounced, it is becoming increasingly important to gain a fundamental understanding of how the chemical composition of modern photoresists influences resist performance. Modern resists contain four basic components: polymer, photoacid generator, dissolution inhibitor, and base quencher. Of these four components, the one that is least understood is the base quencher. This dissertation examines the influence of base additives on line-edge roughness, contrast, photospeed, and isofocal critical dimension (CD). Furthermore, the function of acid/base neutralization products in photoresist films is examined.

Atomic Force Microscopes (AFM) are typically used to image surfaces along with small particulates that may be deposited on the surface. Surface imaging can be made down to the atomic level but usually it is conducted at the nano and micro scales. It is highly desirable to identify the constituency of particulates on the surface and if possible determine the chemical and physical identity of particulates. The objective of the research presented in this thesis is to establish the feasibility of using dual micro cantilevers to determine the physical constituency of nano particles deposited to the micro surface. The goal at this point is not to determine the physical properties of a particulate but rather to determine whether the particulate is hard or soft and categorize it. The research addresses this goal by predicting the vibration response of dual micro cantilever when the cantilever tip engages a surface and a particulate. Five different particulate models are analyzed: elastic, viscous, visco-elastic in parallel, visco-elastic in series and visco-elastic in series/parallel. Each model represents different possible physical constituencies of particles. The analysis shows that each particle model produces unique signatures and vibration responses of the dual micro cantilever. Properties that are identified in the research are signatures. Signatures can be shifts in natural frequencies, change in response amplitudes and phase angles.

Superlattice materials are nanocomposites that exhibit a hardness at small bilayer repeat periods which exceeds the hardness predicted by the rule of mixtures for composites. The objective of this investigation was to utilize the experimental data obtained from nanoindentations and image scanning to examine the behavior of the superlattice material, W/NbN. Nanoindentations and in situ surface imaging were conducted over a range of applied loads on samples of W/NbN with two different bilayer periods (ƒ¼=5.6 nm and ƒ¼=10.4 nm), and monolithic samples of the niobium nitride (NbN) ceramic and the tungsten (W) metal which comprise the superlattice material. Additional shallow nanoindentations were made to a depth equal to the individual layer thicknesses of the nanocomposites. The mechanical properties were determined using the Oliver and Pharr method and compared for all the samples. The load versus displacement curves were also compared. The energies of indentation were calculated. The characteristics of the material pile-up resulting from the nanoindentations are determined from the scanned surface images. The experimental results are discussed to evaluate the influence of the different factors to the increase in hardness. The results indicate that the elastic modulus does not influence the hardness of the superlattice materials. The hardness and load versus displacement curves for the shallow indentations show little difference in behavior between NbN sample and the two superlattice materials. However, an increase in hardness is observed in the superlattice materials at deeper indentation depths. The results indicate that this increase in hardness is related to the nature of the interface between the layers in the superlattice materials.