Dissertations / Theses on the topic 'X-RAY DEVICE'
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1
Hill, Joanne E. "The charge coupled device as an X-Ray polarimeter." Thesis, University of Leicester, 1999. http://hdl.handle.net/2381/30620.
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New results of X-ray polarisation detection efficiencies are presented for two small pixel devices. EEV Ltd. have designed the first CCD X-ray polarimeter with an improved deep depletion layer of 80 urn, to maximise the device quantum efficiency at energies above 1 keV. A novel design concept has been utilised to minimise the pixel dimension whilst maximising production, the CCD has 4x9 um2 pixels. This device was tested and has been shown to be greater than a factor of two more efficient for polarisation measurements above 10 keV, than previously tested CCDs. The first successful measurements below 10 keV show a 5 - 10 % polarisation detection efficiency (modulation factor, M(E)), a significant result, due to X-ray optics having greater effective area below 10 keV. The smallest pixel CCD to date, with 2.4 um2 pixels, designed for optical purposes by Philips Ltd., is shown to have 26.2 % modulation at 10 keV. From the analysis of the data from these devices it has been recognised that charge diffusion, and thus the depletion depth, has a significant effect on the polarisation measurements. A model has been written to simulate polarised X-ray interactions in CCDs, and is shown to successfully model thinly depleted devices (Kodak KAF1400), in terms of polarisation detection efficiency. Further improvements have been identified to provide an accurate model for deeply depleted devices, in order to create a tool for optimising future CCD polarimeters. The modulation factors, M(E), for a 0.5 um2 pixel CCD have been estimated using the model, and it has been shown that a device of this type would provide a further factor of 2 improvement in M(E), with a significant measurement as low as 5 keV. The feasibility of a future mission including a CCD X-ray polarimeter has been investigated in detail, in terms of current and future technology. The XMM and the XEUS optics are considered in conjunction with both the EEV polarimeter and the modelled 0.5 urn2 pixel CCD. Two types of Astronomical sources are taken into account over a 5 - 20 keV energy range: bright galactic objects, e.g. The Crab Nebula faint extragalactic objects e.g. Active Galactic Nuclei (AGN). Using the XEUS optics, a 25 m focal length and an effective area maximised to 1 m2 at 1 keV yields observation times of less than 105 sees for a Crab measurement (polarisation 10 - 20 %, below 12.5 keV) and of the order 104 sees or less using a 0.5 urn2 pixel CCD. For measurements of the more faint AGN (polarisation 10 - 20 %) observation times are of the order 106 sees or below for the EEV CCD (7.5 - 10 keV) and the 0.5 um2 device (5 - 12.5 keV). Employing the XEUS optics for the measurement of the polarisation of AGN requires no further technological advancement if the EEV polarimeter is utilised, and the production of a 0.5 um2 pixel CCD is said to be within easy reach according to manufacturers.
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Bray, Terry Lee. "A novel device for growing protein crystals : computer control and automation." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/30428.
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Carter, David John Donat 1966. "Sub-50nm x-ray lithography with application to a coupled quantum dot device." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50037.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (p. 214-231).
by David John Donat Carter.
Ph.D.
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Poust, Benjamin David. "X-ray scatter based metrologies for the development of metamorphic semiconductor device structures." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1320974691&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Mahadik, Nadeemullah A. "Non-destructive x-ray characterization of wide-bandgap semiconductor materials and device structures." Fairfax, VA : George Mason University, 2008. http://hdl.handle.net/1920/3404.
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Thesis (Ph.D.)--George Mason University, 2008.Vita: p. 104. Thesis director: Mulpuri V. Rao. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical and Computer Engineering. Title from PDF t.p. (viewed Mar. 17, 2009). Includes bibliographical references (p. 99-103). Also issued in print.
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Swaminathan, S. "Characterisation of III-V quaternary multilayer semiconductor device materials by X-ray diffraction." Thesis, University of Warwick, 1985. http://wrap.warwick.ac.uk/110577/.
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Optoelectronic devices find extensive use in optical fibre communication systems as infrared sources, in view of a relatively low attenuation of the optical fibres for such sources in the spectral range 1.0 - 1.4 pm. In the study of optoelectronic device materials, minute variations in the lattice parameter of different layers cause lattice strain, which, along with other factors namely thermal gradients, a high density of recombining carriers in the active layer promote the motion, multiplication and growth of defects into network clusters. In this thesis a double crystal plane wave synchrotron radiation technique has been found to be capable of accurately characterizing individual layers in a multilayer structure such as in an optoelectronic device consisting of many layers of InGaAs, InGaAsP and InP grown over an InP substrate. This non-destructive method can separate images of the ternary and quaternary layers from the substrate (InP) thereby identifying the location of any defects as well as detailed identification of dislocation-type defects. The observed presence of a cross hatch pattern of interfacial misfit dislocations has been strongly correlated to the degradation of the device. The technique also enables a very precise plot of the rocking curves which provides invaluable information about the assessment of the thickness, compositional variation in the ternary or quaternary epitaxial layers and also of their crystalline perfection. The technique is capable of mapping lattice parameter differences of the order of 10-8. A fairly accurate assessment of the inhomogeneity and non-uniformity of quaternary multilayers grown by liquid phase epitaxy has been made by this technique. About 54Z variations in the total quaternary layer thickness was observed for a double heterostructure laser and about 39Z for a thick graded single layer quaternary specimen. For multilayer structures showing complicated rocking curves, it has been demonstrated that a selective etching of the layers in sequence helps identify the individual layer characteristics. A theoretical calculation of rocking curves from heteroepitaxial layers is presented. Initial data from experimental rocking curves are used to calculate rocking curves for the multilayer structure and then compared with experimental curves. The input data are slightly adjusted about their initial values until a reasonable fit with experimental curves is achieved. The initial data consist of the knowledge of the thickness and mismatch variations of each layer in the multilayer structure. The mismatch variations for the layers as obtained by selective etching have been effectively used to simulate experimental rocking curves. An accurate interpretation of layer characteristics from such a simulated fit has thus been made possible. Simulation studies have thus been found to offer a powerful and nondestructive method of a detailed and accurate assessment of layer thickness and compositional variations by comparison with experimental rocking curves. Studies on a number of specimens have shown satisfactory agreement: the predicted thicknesses have been found to be generally of the same order as reported by Plessey, Caswell, where the devices were grown, and in cases where the data were either disputed or not available, experimental verification of the layer thickness made by selective etching, was found to be in agreement with the thickness predicted by the simulated studies.
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Ozkan, Cigdem. "The Controlled Drift Detector As An X-ray Imaging Device For Diffraction Enhanced Imaging." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610414/index.pdf.
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Diffraction Enhanced Imaging (DEI) is an X-ray imaging technique providing specific information about the molecular structure of a tissue by means of coherently scattered photons.
A Controlled Drift Detector (CDD) is a novel 2D silicon imager developed to be used in X-ray imaging techniques.
In this work a final (complete and detailed) analysis of DEI data taken with the CDD in the ELETTRA synchrotron light source facility in Trieste (Italy) in 2005, is presented and the applicability of both this new technique and the novel detector are discussed.
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Pym, Alexander Thomas Gafswood. "Grazing incidence X-Ray scattering from the interfaces of thin film magnetic device materials." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/2317/.
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Thin film devices have found many applications in recently developed technology. With the need to increase data storage capacity and performance there are ever more demanding requirements of these devices. Gaining an understanding at the atomic scale of the growth and subsequent manufacturing treatments is fundamental to improving the device design. Grazing incidence x-ray scattering techniques have been used to study the interfaces in a sequence of samples, starting with repeated bi layers of single element material and sequentially working up to a realistic Magnetic Tunnnel junction (MTJ) structure. The width of the diffuse Bragg sheet from repeated bi-layers of Co/Pd and Co/Ru shows that the correlation length of the out-of-plane toughness is shorter for higher frequency roughness components than longer wavelength features. Scaling behaviour in the intensity profile demonstrates that the interfaces become more two-dimensional as more layers are deposited Reflectivity measurements with in-situ annealing reveal that the interfaces in CoFe/Ru repeated bi-layers are stable with temperature. The interfaces of amorphous CoFeB with ruthenium are also stable until the CoFeB crystallises. Similar measurements on repeated bi-layers of CoFeB/AlO, show sharpening of the interface during annealing. The diffuse scatter shows this to be a reduction in the intetdiffusion of the interface and not a change in topological roughness. The scatter from a single CoFeB/A10, interface on a realistic MTJ sub-structure also shows changes with annealing which are consistent with interface sharpening. This sharpening is matched to enhancements in the tunnel magneto- resistance of the MTJ. The changes occurring cannot be explained solely by sharpening of this particular interface and more sophisticated modelling has been attempted to identify the changes. Simulations show that changes in the manganese profile from an IrMn pinning layer in the MTJ should result in a significant change in the variable energy reflectivity recorded at a constant scattering vector.
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Kang, Jun. "Thin film CdTe as high energy x-ray detector material for medical applications." Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1228060515.
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Gow, Jason Peter David. "Radiation damage analysis of the swept charge device for the C1XS instrument." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4311.
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This thesis is concerned with ensuring high energy resolution from the swept charge device (SCD) CCD54, essentially a non-pixellated version of the charge coupled device (CCD), for use in the Chandrayaan-1 X-ray Spectrometer (C1XS). Of particular interest is the effect on performance due to the radiation damage, caused by protons, the CCD54s used in C1XS will receive during the transfer to the Moon and during the two years in lunar orbit. Chapter 2 reviews the atomic structure, the formation and detection of X-rays, and the operation of a CCD. Chapter 3 discusses the space radiation environment and the damaging effects it has on CCDs, for example increasing dark current and charge transfer inefficiency. Chapter 4 presents the basic laboratory equipment and procedure used during the experimental work, and details the initial optimisation and characterisation, the pre-flight characterisation of devices available for use in C1XS, the measurement of the depletion depth, and quantum efficiency of the CCD54. Chapter 5 details the results of the initial proton irradiation study, intended to demonstrate the ability of the CCD54 to provide excellent scientific data over the two years at the Moon. Chapter 6 describes a second irradiation study covering a more detailed investigation of the damage effects, investigating dark current, trap energy levels, and charge transfer inefficiency. Chapter 7 describes work conducted to assist the C1XS science team in the development of an X-ray fluorescence model, to be used with X-ray spectra provided by the X-ray solar monitor and the spectra detected by C1XS, to provide elemental abundance information of the lunar surface. It also presents the initial C1XS results from the Moon, and a brief comparison of the CCD54 with other semiconductor X-ray fluorescence detectors. Chapter 8 describes the final conclusions and recommendations for further work, including a study of the radiation damage effects during the two years at the Moon and the future development of SCD detectors for use in space.
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Kim, Man-ho. "Three-dimensional numerical analysis of astronomical charge-coupled device image sensors for X-ray or UV detection." Thesis, University of Leicester, 1995. http://hdl.handle.net/2381/34791.
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Continuous advances in silicon processing technology have enabled devices to be more miniaturised and sophisticated. Most scientific Charge-Coupled Devices (CCDs), for example those used in astronomy, are following this trend; they are being scaled down and their doping profiles are becoming more complicated. Such trends increasingly require the use of three-dimensional (3-D) numerical simulations to provide improved designs. This thesis covers work focused on the three-dimensional simulation of buried-channel (BC) MOSFETs and CCDs. For BC MOSFETs a 1-D analytic model is developed to study their electrical characteristics and this is followed by 3-D numerical simulation work. Geometric-induced physical effects are thoroughly investigated using the 3-D simulation to optimise the scaling factor for the device. This simulation shows that 2-D simulation cannot estimate accurately the electrical characterisations of the narrow-channel and small geometry devices. For BC CCDs two X-ray astronomy CCDs are introduced: EPIC CCD as an open- electrode CCD imager and JET-X CCD. The optical properties of the EPIC CCD, used for ultra-low signal applications, were shown to be critically dependent on the dead layers and optical filter. It was clearly shown, for both devices, that 3-D simulations are useful for analysing charge storage and handling despite the complicated doping profile and sophisticated design structure. The charge handling capability of the JET-X CCD was found to be 9900 (electrons/?.m) using a 1-D analytical model. A 3-D static simulation of the JET-X CCD enabled estimations of the full-well capacity (60040 electrons), different depletion edge positions (< 5 % errors) and an optimised output gate voltage (between 3 and 4 V) for a higher charge transfer efficiency and demonstrated routes for optimisation and improvement. A 3-D transient simulation of the same device enabled estimations of the dynamic full- well capacity (61110 electrons), a dark current contribution (< 1 electron for a pixel clock cycle of 1.85 ?s) and a charge transfer inefficiency (< 0.001 % for a pixel clock cycle of 4.2 ns with a fall time of 0.4 ns). The 3-D simulation work suggests that a higher charge detection efficiency and charge transfer efficiency can be achieved with a higher-resistivity epi-material and a pixel clock cycle with a longer fall time (i.e. > 0.4 ns).
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Ward, Allan III. "Residual Stress Effects on Power Slump and Wafer Breakage in GaAs MESFETs." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/30503.
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The objectives of this investigation are to develop a precise, non-destructive single crystal stress measurement technique, develop a model to explain the phenomenon known as 3power slump2, and investigate the role of device processing on wafer breakage. All three objectives were successfully met. The single crystal stress technique uses a least squares analysis of X-ray diffraction data to calculate the full stress tensor. In this way, precise non-destructive stress measurements can be made with known error bars. Rocking curve analysis, stress gradient corrections, and a data reliability technique were implemented to ensure that the stress data are correct. A theory was developed to explain 3power slump2, which is a rapid decrease in the amplifying properties of microwave amplifier circuits during operation. The model explains that for the particular geometry and bias configuration of the devices studied in this research, power slump is linearly related to shear stress at values of less than 90 MPa. The microscopic explanation of power slump is that radiation enhanced dislocation glide increases the kink concentration, thereby increasing the generation center concentration in the active region of the device. These generation centers increase the total gate current, leading to a decrease in the amplifying properties of the device. Passivation layer processing has been shown to both reduce the fracture strength and increase the residual stress in GaAs wafers, making them more susceptible to wafer breakage. Bare wafers are found to have higher fracture strength than passivated wafers. Bare wafers are also found to contain less residual stress than SiON passivated wafers, which, in turn, are found to have less stress than SiN passivated wafers. Topographic imaging suggests that SiN passivated wafers have larger flaws than SiON passivated wafers, and that the distribution of flaw size among SiN passivated wafers is wider than the distribution of flaws in SiON passivated wafers. These flaws are believed to lead to breakage of the device during processing, resulting in low fabrication yield. Both the power slump model and the wafer breakage data show that these phenomena are dependent on residual stress developed in the substrate during device fabrication. Reduction of process-induced residual stress should therefore simultaneously decrease wafer breakage rates and reduce power slump during device fabrication and operation.Ph. D.
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Sharpnack, Lewis Lee. "Mesomorphism of Newly Synthesized Mesogens and Surface Morphology of Chalcogenide Glass Thin Films." Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1499949477885501.
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Mohamed, Amgad Elsayed Soliman. "A dense plasma focus device as a pulsed neutron source for material identification." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/18997.
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Doctor of PhilosophyDepartment of Mechanical and Nuclear Engineering
William L. Dunn
Dense plasma focus (DPF) devices are pulsed power devices capable of producing short-lived, hot and dense plasmas (~10[superscript]19 cm[superscript]-3) through a fast compression of plasma sheath. A DPF device provides intense bursts of electrons and ion beams, X-rays, and 2.5 MeV neutrons when operated with deuterium through the fusion reaction [superscript]2H(d,n)[superscript]3He. The Kansas State University DPF machine was designed and constructed in early 2010. The device was characterized to determine its performance as a neutron source. The device was shown to produce 5.0x10[superscript]7 neutrons/pulse using a tungsten-copper anode. Such machines have the advantages of being non-radioactive, movable, and producing short pulses (typically tens of nanoseconds), which allows rapid interrogation. The signature-based radiation-scanning (SBRS) method has been used to distinguish targets that contain explosives or explosive surrogates from targets that contain materials called “inert,” meaning they are not explosive-like. Different targets were placed in front of the DPF source at a distance of 45 cm. Four BC-418 plastic scintillators were used to measure the direct neutron yield and the neutrons scattered from various targets; the neutron source and the detectors were shielded with layers of lead, stainless steel, and borated polyethylene to shield against the X-rays and neutrons. One of the plastic scintillators was set at 70[supercript]o and two were set at 110[superscript]o from the line of the neutron beam; a bare [superscript]3He tube was used for detecting scattered thermal neutrons. Twelve metal cans of one-gallon each containing four explosive surrogates and eight inert materials were used as targets. Nine materials in five-gallon cans including three explosive surrogates were also used. The SBRS method indicated a capability to distinguish the explosive surrogates in both experiments, although the five gallon targets gave more accurate results. The MCNP code was used to validate the experimental work and to simulate real explosives. The simulations indicated the possibility to use the time of flight (TOF) technique in future experimental work, and were able to distinguish all the real explosives from the inert materials.
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Davesne, Vincent. "Organic spintronics : an investigation on spin-crossover complexes from isolated molecules to the device." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01062266.
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We have studied by STM, SQUID, X-ray reflectivity, X-ray diffraction, optical absorption and XAS Fe(phen)2(NCS)2 and Fe{[3,5-dimethylpyrazolyl]3BH}2 samples deposited by thermal evaporation on Cu(100), Co(100) and SiO2 substrates, and compared with results on powder samples. We have confirmed the existence of the soft X-ray induced excited spin state trapping (SOXIESST), and investigated its properties, in particular dynamic aspects. The effect is sensitive to the intensity and the structure of the applied X-ray beam, and is non-resonant. We suggest that its efficiency is also governed by metal-ligand charge transfer states (MLCT). The study of single molecules has revealed that they could be switched by voltage pulses, and by this way building memristive devices, but only if the influence of the substrate is sufficiently reduced. We have then investigated thin films with the help from a simple thermodynamic model, and evidenced that the cooperativity was reduced and the transition temperature is modified (higher for Fe-phen, and lower for Fe-pyrz). Finally, we use these results to build multilayer vertical devices Au/Fe-phen/Au, and its electrical properties depends, according to our preliminary results, on the external stimuli (temperature, magnetic field). Notably, they present a "diode" effect at the spin transition.
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Spisni, Giacomo. "Radiation-sensitive OXide semiconductor Field Effect Transistor (ROXFET): a novel thin-film device for real-time and remote ionizing radiation detection." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24394/.
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Nowadays, ionizing radiation detectors find application in a wide range of contexts, spanning from industry to healthcare and security. In this background, the next generation of ionizing radiation sensors require devices that are accurate, light-weight, relatively inexpensive and capable to be read-out in real-time and remotely. In recent years, research groups at the University of Bologna and the NOVA University of Lisbon (Portugal) have developed Radiation-sensitive OXide-semiconductor Field-Effect Transistors (ROXFET) to be employed as fast, real-time x-ray dosimetry detection systems. The ROXFET operation relies on the principle that, upon exposure to radiation, excitons are generated in the dielectric and separated into hole and electron charge carriers. While electrons are able to diffuse out of the dielectric layer, hole charges get trapped and contribute to the field-effect in the semiconductor channel. Macroscopically, such contribution is observable as a shift in transistor threshold voltage toward negative values, which turns out to be proportional to the absorbed radiation dose. In laboratory tests, ROXFET devices proved to be sensitive in a wide energy range and capable of providing reliable information about their radiation exposure history. Furthermore, the design of ROXFET can be integrated on a flexible substrate and read in real-time as a passive radiofrequency tag. Aim of this thesis work was to contribute to the development of the ROXFET technology. To this end, I carried out multiple characterization tests on recently fabricated samples, revealing how they outperformed previously observed radiation sensitivities. Later on, I worked in a clean-room facility to fabricate new ROXFET experimental samples by leveraging the knowledge acquired from previous observations.
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Parent, Laure. "The use of Monte Carlo methods to study the effect of X-Ray spectral variations on the response of an Amorphous Silicon Electronic Portal Imaging Device." Thesis, Institute of Cancer Research (University Of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444169.
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Haralson, Erik. "Device design and process integration for SiGeC and Si/SOI bipolar transistors." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3836.
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SiGe is a significant enabling technology for therealization of integrated circuits used in high performanceoptical networks and radio frequency applications. In order tocontinue to fulfill the demands for these applications, newmaterials and device structures are needed. This thesis focuseson new materials and their integration into heterojunctionbipolar transistor (HBT) structures as well as using devicesimulations to optimize and better understand the deviceoperation. Specifically, a SiGeC HBT platform was designed,fabricated, and electrically characterized. The platformfeatures a non-selectively grown epitaxial SiGeC base,in situdoped polysilicon emitter, nickel silicide,LOCOS isolation, and a minimum emitter width of 0.4 μm.Alternately, a selective epitaxy growth in an oxide window wasused to form the collector and isolation regions. Thetransistors exhibited cutoff frequency (fT) and maximum frequency of oscillation (fMAX) of 40-80 GHz and 15-45 GHz, respectively.Lateral design rules allowed the investigation of behavior suchas transient enhanced diffusion, leakage current, and theinfluence of parasitics such as base resistance and CBC. The formation of nickel silicide on polysiliconSiGe and SiGeC films was also investigated. The formation ofthe low resistivity monosilicide phase was shown to occur athigher temperatures on SiGeC than on SiGe. The stability of themonosilicide was also shown to improve for SiGeC. Nickelsilicide was then integrated into a SiGeC HBT featuring aselectively grown collector. A novel, fully silicided extrinsicbase contact was demonstrated along with the simultaneousformation of NiSi on thein situdoped polysilicon emitter.
High-resolution x-ray diffraction (HRXRD) was used toinvestigate the growth and stability of SiGeC base layers forHBT integration. HRXRD proved to be an effective, fast,non-destructive tool for monitoring carbon out-diffusion due tothe dopant activation anneal for different temperatures as wellas for inline process monitoring of epitaxial growth of SiGeClayers. The stability of the SiGe layer with 0.2-0.4 at% carbonwhen subjected to dopant activation anneals ranging from1020-1100°C was analyzed by reciprocal lattice mapping.It was found that as the substitutional carbon increases theformation of boron clusters due to diffusion is suppressed, buta higher density of carbon clusters is formed.
Device simulations were performed to optimize the DC and HFperformance of an advanced SiGeC HBT structure with low baseresistance and small dimension emitter widths. The selectivelyimplanted collector (SIC) was studied using a design ofexperiments (DOE) method. For small dimensions the lateralimplantation straggle has a significant influence on the SICprofile (width). A significant influence of the SIC width onthe DC gain was observed. The optimized structure showedbalanced fT/fMAXvalues of 200+ GHz. Finally, SOI BJT transistorswith deep trench isolation were fabricated in a 0.25μmBiCMOS process and self-heating effects were characterized andcompared to transistors on bulk silicon featuring deep trenchand shallow trench isolation. Device simulations based on SEMcross-sections and SIMS data were performed and the resultscompared to the fabricated transistors.
Key words:Silicon-Germanium(SiGe), SiGeC,heterojunction bipolar transistor(HBT), nickel silicide,selectively implanted collector(SIC), device simulation, SiGeClayer stability, high resolution x-ray diffraction(HRXRD),silicon-on-insulator(SOI), self-heating.
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Montag, Benjamin W. "Lithiated ternary compounds for neutron detectors: material production and device characterization of lithium zinc phosphide and lithium zinc arsenide." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/20415.
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Doctor of PhilosophyMechanical and Nuclear Engineering
Douglas S. McGregor
There is a need for compact, rugged neutron detectors for a variety of applications including national security and oil well logging. A solid form neutron detector would have a higher efficiency than present day gas filled ³He and ¹⁰BF ₃ detectors, which are standards currently used in the industry today. A sub-branch of the III-V semiconductors is the filled tetrahedral compounds, known as Nowotny-Juza compounds (A[superscript I]B[superscript II]C[superscript V]). These materials are desirable for their cubic crystal structure and semiconducting electrical properties. Originally studied for photonic applications, Nowotny-Juza compounds have not been fully developed and characterized. Nowotny-Juza compounds are being studied as neutron detection materials here, and the following work is a study of LiZnP and LiZnAs material development and device characterization. Precursor binaries and ternary materials of LiZnAs and LiZnP were synthesized in-house in vacuum sealed quartz ampoules with a crucible lining. Synthesized powders were characterized by x-ray diffraction, where lattice constants of 5.751 ± .001 Å and 5.939 ± .002 Å for LiZnP and LiZnAs, respectively, were determined. A static vacuum sublimation in quartz was performed to help purify the synthesized ternary material. The resulting material from the sublimation process showed characteristics of a higher purity ternary compound. Bulk crystalline samples were grown from the purified material. Ingots up to 9.0 mm in diameter and 13.0 mm in length were harvested. Individual samples were characterized for crystallinity on a Bruker AXS Inc. D2 CRYSO, energy dispersive x-ray diffractometer, and a Bruker AXS D8 DISCOVER, high-resolution x-ray diffractometer with a 0.004° beam divergence. High-resolution XRD measurements indicated reasonable out-of-plane and in-plane ordering of LiZnP and LiZnAs crystals. Devices were fabricated from the LiZnP and LiZnAs crystals. Resistivity of devices were determined within the range of 10⁶ – 10¹¹ Ω cm. Charge carrier mobility and mean free drift time products were characterized for electrons at 8.0 x 10⁻⁴ cm² V⁻¹ ± 4.8% and 9.1 x 10⁻⁴ cm² V⁻¹ ± 4.4% for LiZnP and LiZnAs respectively. Sensitivity to 337 nm laser light (3.68 eV photons) was observed, where an absorption coefficient of 0.147 mm⁻¹ was determined for LiZnAs devices. Thermal neutron sensitivity was evaluated with unpurified and purified LiZnP and LiZnAs devices. Sensitivity was observed, however material quality and crystalline quality significantly hindered device performance.
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Eklund, Anders. "Microwave Frequency Stability and Spin Wave Mode Structure in Nano-Contact Spin Torque Oscillators." Doctoral thesis, KTH, Integrerade komponenter och kretsar, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188546.
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The nano-contact spin torque oscillator (NC-STO) is an emerging device for highly tunable microwave frequency generation in the range from 0.1 GHz to above 65 GHz with an on-chip footprint on the scale of a few μm. The frequency is inherent to the magnetic material of the NC-STO and is excited by an electrical DC current by means of the spin torque transfer effect. Although the general operation is well understood, more detailed aspects such as a generally nonlinear frequency versus current relationship, mode-jumping and high device-to-device variability represent open questions. Further application-oriented questions are related to increasing the electrical output power through synchronization of multiple NC-STOs and integration with CMOS integrated circuits. This thesis consists of an experimental part and a simulation part. Experimentally, for the frequency stability it is found that the slow but strong 1/f-type frequency fluctuations are related to the degree of nonlinearity and the presence of perturbing, unexcited modes. It is also found that the NC-STO can exhibit up to three propagating spin wave oscillation modes with different frequencies and can randomly jump between them. These findings were made possible through the development of a specialized microwave time-domain measurement circuit. Another instrumental achievement was made with synchrotron X-rays, where we image dynamically the magnetic internals of an operating NC-STO device and reveal a spin wave mode structure with a complexity significantly higher than the one predicted by the present theory. In the simulations, we are able to reproduce the nonlinear current dependence by including spin wave-reflecting barriers in the nm-thick metallic, magnetic free layer. A physical model for the barriers is introduced in the form of metal grain boundaries with reduced magnetic exchange coupling. Using the experimentally measured average grain size of 30 nm, the spin wave mode structure resulting from the grain model is able to reproduce the experimentally found device nonlinearity and high device-to-device variability. In conclusion, the results point out microscopic material grains in the metallic free layer as the reason behind the nonlinear frequency versus current behavior and multiple propagating spin wave modes and thereby as a source of device-to-device variability and frequency instability.Dagens snabba utveckling inom informationsteknik drivs på av ständigt växande informationsmängder och deras samhällsanvändning inom allt från resursoptimering till underhållning. Utvecklingen möjliggörs till stor del hårdvarumässigt av miniatyrisering och integrering av elektroniska komponenter samt trådlös kommunikation med allt större bandbredd och högre överföringshastighet. Det senare uppnås främst genom utnyttjande av högre radiofrekvenser i teknologiskt tidigare oåtkomliga delar av spektrumet. Frekvensutnyttjandet har det senaste årtiondet ökat markant i mikrovågsområdet med typiska frekvenser runt 2.4 GHz och 5.2-5.8 GHz. I den spinntroniska oscillatorn (STO:n) möjliggörs frekvensgenerering i det breda området från 0.1 GHz upp till över 65 GHz av en komponent med mikrometerstorlek som kan integreras direkt i CMOS-mikrochip. Till skillnad från i konventionella radiokretsar med oscillatorer konstruerade av integrerade transistorer och spolar, genereras mikrovågsfrekvensen direkt i STO:ns magnetiska material och omvandlas därefter till en elektrisk signal genom komponentens magnetoresistans. Dessa materialegenskaper möjliggör ett tillgängligt frekvensband med extrem bredd i en och samma STO, som därtill kan frekvensmoduleras direkt genom sin styrström och på så sätt förenklar konstruktionen av sändarsystem. STO:ns icke-linjära egenskaper kan potentiellt också användas för att i en och samma komponent blanda ned mottagna mikrovågssignaler och på så sätt förenkla konstruktionen även av mikrovågsmottagare. STO:ns signalegenskaper bestäms av det magnetiska materialets fysik i form av magnetiseringsdynamik driven av elektriskt genererade spinnströmmar. I denna avhandling studeras denna dynamik experimentellt med särskilt fokus på frekvensstabiliteten i den hittills mest stabila STO-typen; nanokontakts-STO:n. Genom mätningar i tidsdomän av STO:ns elektriska signaler runt 25 GHz har frekvensstabiliteten funnits hänga samman med den typ av icke-linjärt beteende som också funnits vara utmärkande för tillverkningsvariationen i komponenterna. Mikroskopiska undersökningar av materialet visar att en trolig källa till denna variation är den magnetiska metallens uppbyggnad i form av korn i storleksordningen 30 nm, och datorsimuleringar av en sådan materialstruktur har visats kunna reproducera de experimentella resultaten. Därtill har en metod utvecklats för att med röntgenstrålning direkt mäta de små, magnetiska mikrovågsrörelserna i materialet. Denna röntgenteknik möjliggör detaljerade experimentella studier av magnetiseringsdynamiken och kan användas för att verifiera och vidareutveckla den existerande teorin för mikrovågsspinntronik. Sammantaget förs STO-teknologin genom denna studie ett steg närmare sina tänkbara samhällsbreda tillämpningar inom snabb, trådlös kommunikation för massproducerade produkter med integrerad sensor- och datorfunktionalitet.
QC 20160620
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Kripalani, Rishi A. "Novel Integration of Conductive-ink Circuitry with a Paper-based Microfluidic Battery as an All-printed Sensing Platform." DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1694.
Full textAbstract:
The addition of powered components for active assays into paper-based analytical devices opens new opportunities for medical and environmental analysis in resource-limited applications. Current battery designs within such devices have yet to adopt a ubiquitous circuitry material, necessitating investigation into printed circuitry for scalable platforms. In this study, a microfluidic battery was mated with silver-nanoparticle conductive ink to prototype an all-printed sensing platform. A multi-layer, two-cell device was fabricated, generating 200 μA of direct electrical current at 2.5 V sustained for 16 minutes with a power loss of less than 0.1% through the printed circuitry. Printed circuitry traces exhibited resistivity of 75 to 211 10-5 Ω m. Resistance of the printed traces increased upwards of 200% depending on fold angle and directionality. X-ray diffraction confirmed the presence of face-centered cubic silver after sintering printed traces for 30 minutes at 150°C in air. A conductivity threshold was mapped and an ink concentration of 0.636 μL mm-3 was identified as the lower limit for optimal electrical performance.
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RodriÌguez, MartiÌn David. "X-ray characterization of smectic devices." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412347.
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Howell, Mark John. "Signal processing for X ray spectroscopy." Thesis, Bangor University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361173.
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Törne, Karin. "Biocompatible X-ray opaque polymers for medical devices." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-44036.
Full textAbstract:
During coronary catheterization X-ray imaging is used to image coronary artery system. After the procedure X-ray imaging may be used to locate devices purposely left in the patient. The objective of this thesis was to investigate the possibility of improving X-ray opacity to medical devices made by St Jude Medical Systems AB. Two different routes were explored, inorganic-organic hybrid materials and functionalization of polymers with iodine. Sol-Gel synthesis was used to synthesize nanocomposite hybrid materials with TiO2 and Ta2O5. Iodine was incorporated by the use of an iodine containing initiator and by end group functionalization with triiodobenzoic acid. The materials were evaluated by X-ray imaging, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). The optical and mechanical properties were evaluated by visual inspection and by handling of the materials. Hybrid materials with Polydimetylsiloxane (PDMS) or Poly ester copolymers and Ta2O5 were found to have promising mechanical properties and degree of X-ray opacity. Iodinated polyesters with ~18 wt% iodine also demonstrated sufficient properties to promote further investigation. Some of the work done and obtained results has been excluded from this report due to patent applications.
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Rodríguez, Sanmartín Daniel. "Smart piezoelectric devices for X-ray optics applications." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3193/.
Full textAbstract:
The development of active/adaptive X-ray optics, utilising piezoelectric actuation for the focussing of X-rays in large and small scale applications, has been studied as part of the UK Smart X-Ray Optics (SXO) consortium. For laboratory based X-ray sources utilising micro structured optical arrays (MOAs), a novel spider actuator structure, compatible with silicon wet etching of MOAs, has been developed. Test spider samples (20x20x0.100mm) have been bent to a 6.5cm radius using unimorph actuators, and to a 3cm radius without failure. FEA models predicted that a 4.5cm radius and +/-3mrad tip/tilt control of the MOAs could be obtained using unimorph actuators with segmented electrodes and optimized thickness, which would enable a tandem pair MOA configuration of suitable focal length. A first generation prototype Wolter I optic for future high resolution X-ray telescopes exhibited kinks in the reflecting surface corresponding to the gaps between piezoelectric devices. FEA models have been used to develop second generation prototypes in which the gaps have been minimised or filled. These incorporate a brick wall arrangement of curved unimorph piezoelectric actuators (32x75x0.190mm) with radii from 160-200mm +/-6mm, manufactured using a VPP technique and laser machining for precise dimensional control. Keywords: Smart X-ray optics (SXO), micro-structured optical arrays (MOAs), Wolter I X-ray optics, piezoelectric actuators, finite element analysis (FEA), viscous plastic processing (VPP).
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Wong, Vincent V. "Fabrication of distributed feeback devices using X-ray lithography." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/37789.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 125-134).
by Vincent V. Wong.
Ph.D.
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Jenkins, Sam. "X-ray characterisation of surface stabilised ferroelectric liquid crystal devices." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324295.
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Lawrence, Shane Michael. "X-ray and neutron scattering of multiferroic LuFe2O4." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1336.
Full textAbstract:
Multiferroic materials have recently begun to attract significant scientific interest due to their potential applications in the design of modern electronic devices. Currently, the magnetic properties of materials form the basis of our electronic data storage and have the potential to enhance the logic operations performed in electronic devices (such as computers and sensors). Non-volatile magnetic memory is used in data storage devices, such as the hard drives found in personal computers, where data is encoded via the magnetisation state of magnetic domains in the device with one of two states: either up or down (M ↑ or M ↓); the state is determined or changed by interacting with the magnetic flux about the domain. Furthermore, in current computing and sensor technology, logic operations are performed with arrays of transistors; however, in spintronics ("spin transport electronics") the electric current itself is spin polarised and there is data encoded in the current itself. Circuit elements in such a system are magnetic devices that interact with the electron spin.Magnetoelectric multiferroics are materials that have both a spontaneous ferroelectric polarisation (P) and magnetic magnetisation (M). Polarisation may be manipulated by an electric field and magnetisation by a magnetic field, hence the potential of multiferroics lies in the coupling between the two degrees of freedom and the manipulation of magnetisation by an applied electric field and vice versa. The properties of a magnetic device could be altered "on-the-fly" by applying an electric pulse, and in the context of the examples provided this would greatly diversify the logic elements in spintronic circuits. Furthermore, with both polarisation and magnetisation a multiferroic domain can take on one of four states (M ↑ P ↑, M ↑ P ↓, M ↓ P ↑, or M ↓ P ↓) dramatically increasing data storage density over the current binary system.Lutetium ferrite (LuFe2O4) is a multiferroic material in which both the magnetisation and polarisation arise from the iron sites and with strong iron-iron correlations the material is a promising candidate as a high temperature multiferroic. The material has a layered structure with bilayers of FeO separated by single layers of LuO on a hexagonal lattice. Frustrated 2D charge order exists below 550 K which transitions to 3D charge order below 330 K and simultaneously frustrated ferrimagnetic order exists in the multiferroic phase below 250 K. X-ray and neutron scattering experiments have been performed in order to characterise the ferroelectric and ferrimagnetic order and magnetoelectric coupling in this material.Resonant x-ray scattering (RXS) was performed on the Material Science beamline of the Swiss Light Source where the energy dependence of the superlattice reflections corresponding to the charge order was collected. Non-linear regression using a custom Levenberg-Marquadt algorithm was applied in order to extract the anomalous scattering factors which demonstrated the superlattice reflections were described by a charge order model. Furthermore, the chemical shift was shown to correspond to full Fe2+/Fe3+ charge disproportionation. The absence of any polarisation or azimuthal dependence, shown by resonant x-ray scattering data collected on the ID20 beamline of the European Synchrotron Radiation Facility, confirmed the prediction of Nagano et al. that the orbital moments of the Fe2+-sites exist in a disordered glassy state.X-ray absorption near edge structure (XANES) calculations were performed using the FDMNES program in order to assess the validity of the anomalous scattering factors obtained in the RXS experiment and to further test the charge order model. It was shown that the characteristic features of the experimentally determined functions can be qualitatively reproduced by calculations using the known charge order model. Furthermore, these functions were shown to reproduce the phase of the RXS data further demonstrating that the reflections result from a pure charge ordered phase.Inelastic neutron scattering performed on the PUMA triple axis spectrometer of the FRMII demonstrated that magnetic critical scattering is observed at 250 K. A broad peak in the temperature dependence is observed rather than the characteristic divergence of a magnetic transition: this is attributed to broadening of the transition by the distribution of oxygen stoichiometry in the sample and ferroelectric fluctuations integrated into the data due to poor c-axis resolution. Pyroelectric current and magnetometry measurements demonstrate a peak in the magnetic susceptibility and a step in the polarisation at approximately 215 K, well below the magnetic transition. Elastic neutron scattering experiments performed on the E2 flat cone diffractometer of the Helmholtz-Zentrum Berlin demonstrate these features correspond to a 2D-to-3D magnetic transition that has previously only been predicted by anomalies in other measurements.An applied field study performed by neutron scattering on the E2 flat cone diffractometer of the Helmholtz-Zentrum Berlin and x-ray scattering on the PX1 protein crystallography beamline of the Australian synchrotron demonstrate the control of the magnetic domain population with an electric field, contrary to other recent reports on this topic. Furthermore, the observed magnetoelectric coupling is inconsistent with current models of the magnetic structure of this system. The x-ray measurements demonstrate a disorder-to-order effect by the applied electric field as 3D order is preferred with an increase in the intensity of all satellites.Temperature dependent x-ray powder diffraction data collected on the Powder Diffraction (PD) beamline of the Australian Synchrotron has demonstrated anisotropic thermal expansion with negative thermal expansion of the c-axis in this material. Electron density mapping by Fourier analysis shows the disorder of the oxygen between the electrically static Lu ions and the neighbouring Fe ions, as electron hopping between Fe2+ and Fe3+ leading to a corresponding variation on the Fe-O bond length. Reversible structural distortions are observed indicating a piezoelectric effect in this material caused by the crushing during sample preparation. Furthermore, weak reflections in the x-ray patterns, corresponding to a monoclinic sublattice, suggest a monoclinic distortion of the oxygen sites which is supported by neutron powder diffraction collected on the ECHIDNA instrument of the OPAL reactor.
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Mariotti, Francesco. "Characterization of organic thin film devices for direct X-ray photoconversion." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/17048/.
Full textAbstract:
The main purpose of this thesis is to present the fundamental characteristics of organic thin film devices for direct X-ray photoconversion. In the first part of this study will be presented the theoretical background of X-rays, X-rays detection and the theory organic devices.
In the second part will be considered in details the process of fabrication and characterization of organic devices projected for X-rays detection. The subjects of this thesis are some samples realized at the laboratories of the Department of Physics and Astronomy of Bologna: their fabrication and their
electrical and X-rays characterization will be analised in this work. These samples have been realized on 5 different ”substrates” in order to study their effect on the behaviour of the device. In the third and last part will be presented the characterization of a TIPGe device realized at the labora-
tories of the Department of Physics and Astronomy of Bologna, and tested at Skan-X Radiology Devices S.p.A. The collaboration with this company offered the
possibility to test the device with a complete different sets of parameters, in energy and dose range typical of dental medical applications. Moreover it was a constructive collaboration under the aspect of further developments of the device: physicists and experts from Skan-X Radiology Devices S.p.A. and from SkanRay S.p.A. defined the key points that organic
thin film devices for direct X-ray photoconversion should have to work as a X-rays detectors for radiographic imaging.
The encouraging results placed the bases for further analysis such as testing the device with other X-ray machine or/and trying to better understand the effect of the substrates on the behaviour of the device. In addition they represent the starting point for the beginning of the process of scaling of the device in order to move towards the fabrication of a prototype of X-rays detector for radiographic imaging
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Tanaka, Takashi. "Study on Insertion Devices as Vacuum-Ultraviolet and Soft X-ray Sources." Kyoto University, 1996. http://hdl.handle.net/2433/160810.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第6559号
工博第1561号
新制||工||1048(附属図書館)
UT51-96-W403
京都大学大学院工学研究科原子核工学専攻
(主査)教授 今西 信嗣, 教授 若谷 誠宏, 教授 吉川 潔
学位規則第4条第1項該当
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Favretto, Stefano. "Applications of x-ray computed microtomography to material science: devices and prespectives." Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2756.
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2006/2007The three-dimensional visualization of the inner microstructural features of objects and materials is an aspect of relevant interest for a wide range of scientific and industrial applications. X-ray computed microtomography (μ-CT) is a powerful non-destructive technique capable to satisfy these needs. Once the complete reconstruction of the sample is available, a quantitative characterisation of the microstructure is essential. Through digital image processing tools, image analysis software or custom developed algorithms, it is possible to obtain an exhaustive geometrical, morphological and topological description of the features inside the volume, or to extract other particular parameters of interest (e.g. porosity, voids distribution, cell size distribution, average struts length, connectivity between the cells, tortuosity). This thesis was carried out at the third-generation Elettra Synchrotron Radiation Facility (Trieste, Italy), where a hard X-ray imaging beamline is available. The experience developed at this beamline has leaded scientists to design a complementary state-of-the-art μ-CT facility based on a micro-focus X-ray source, working both in absorption and phase contrast mode. In this dissertation a detailed description of this facility is given together with a rigorous characterization of the imaging system capabilities, in terms of the actual achievable spatial resolution, in order to optimize the working parameters for the different experiments. The main artefacts that concur to the degradation of the quality of the reconstructed images have been considered (e.g. beam hardening effects, ring artefacts, uncertainness associated with the cone-beam geometry): procedures are presented in order to eliminate, or at least to reduce, the causes of these artefacts. The aspects related to the digital image processing of the reconstructed data are intensively developed in this study: appropriated methodologies have been elaborated capable to deal with the different three-dimensional data of complex porous media, providing a correlation between the microstructure and the macroscopic behaviour of the observed materials. Three representative examples obtained with the described methods are used to demonstrate the application of μ-CT, combined with the developed image processing tools, to material science: the geometrical and morphological characterisation of polyurethane foams employed in the automotive industry due their vibro-acoustic properties; a new approach to characterize the resonance spruce wood microstructure in order to study its acoustical behaviour; finally, the possibility of revealing defects in hybrid-friction stir welded aluminium joints, guiding the optimization of the process parameters.
La visualizzazione tridimensionale della struttura interna di oggetti e materiali costituisce un aspetto di notevole interesse per una ampia gamma di applicazioni scientifiche ed industriali. La microtomografia computerizzata a raggi X (μ-CT) rappresenta una potente tecnica di indagine adeguata a soddisfare tali richieste. Una volta completata la ricostruzione del campione in esame, è essenziale poter fornire una caratterizzazione quantitativa della microstruttura evidenziata. Attraverso gli strumenti messi a disposizione dalle moderne tecniche di analisi di immagine, per mezzo di software dedicati o algoritmi personalizzati, è possibile ottenere una descrizione esaustiva della geometria, morfologia e topologia degli elementi microstrutturali presenti, che consenta l’estrazione dei parametri di interesse per la particolare applicazione (porosità, distribuzione dei vuoti, dimensione degli elementi, lunghezze caratteristiche, grado di interconnessione, tortuosità etc.). Il presente lavoro di tesi è stato svolto presso il laboratorio di luce sincrotrone di terza generazione Elettra (Trieste, Italia), dove è disponibile una linea sperimentale dedicata all’imaging con raggi X duri. L’esperienza acquisita da parte dei ricercatori di questa linea ha consentito poi la progettazione di una stazione per μ-CT complementare, allo stato dell’arte e basata su una sorgente di radiazione a microfuoco, capace di operare con modalità di raccolta delle immagini sia in assorbimento sia in contrasto di fase. In questa tesi viene fornita una dettagliata descrizione della stazione, accompagnata da una rigorosa caratterizzazione del sistema impiegato per l’acquisizione e la ricostruzione delle immagini, in termini di risoluzione spaziale raggiungibile, così da consentire l’ottimizzazione dei parametri critici di lavoro nelle differenti condizioni sperimentali. Vengono poi presi in considerazione i principali artefatti che contribuiscono al deterioramento della qualità delle immagini ottenute (come il beam hardening, gli artefatti ad anello, gli artefatti legati all’incertezza geometrica associata al fascio conico etc.): vengono quindi proposti dei metodi per l’eliminazione, o almeno la riduzione, delle cause che li determinano. Nella tesi inoltre sono sviluppati in maniera approfondita gli aspetti connessi al trattamento dei dati digitali raccolti: sono state infatti elaborate delle metodologie appropriate, capaci di trattare i diversi tipi di dato provenienti dall’analisi di mezzi porosi, determinanti per la comprensione della correlazione tra la microstruttura del materiale ed il suo comportamento macroscopico. Infine, vengono proposti tre esempi rappresentativi per dimostrare l’efficacia dell’applicazione della μ-CT, in combinazione con gli strumenti di analisi di immagine messi a punto, alla scienza dei materiali: la caratterizzazione geometrica e morfologica di schiume di poliuretano impiegate nell’industria automobilistica come isolante vibro-acustico; un nuovo approccio rivolto alla caratterizzazione della struttura del legno di risonanza al fine di studiarne il comportamento acustico; la possibilità di mettere in luce i difetti in giunti di saldatura di leghe d’alluminio realizzati con la tecnica ibrida friction stir welding/TIG in maniera da ottimizzare i parametri di processo.
XX Ciclo
1978
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Horsburgh, Gordon. "MBE growth and characterisation of II-VI semiconductor materials and devices." Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/1256.
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Bismuth, Vincent, and Vincent Bismuth. "Image processing algorithms for the visualization of interventional devices in X-ray fluoroscopy." Phd thesis, Université Paris-Est, 2012. http://tel.archives-ouvertes.fr/tel-00786326.
Full textAbstract:
Stent implantation is the most common treatment of coronary heart disease, one of the major causes of death worldwide. During a stenting procedure, the clinician inserts interventional devices inside the patient's vasculature. The navigation of the devices inside the patient's anatomy is monitored in real-time, under X-ray fluoroscopy. Three specific interventional devices play a key role in this procedure: the guide-wire, the angioplasty balloon and the stent. The guide-wire appears in the images as a thin curvilinear structure. The angioplasty balloon, that has two characteristic markerballs at its extremities, is mounted on the guide-wire. The stent is a 3D metallic mesh, whose appearance is complex in the fluoroscopic images. Stents are barely visible, but the proper assessment of their deployment is key to the procedure. The objective of the work presented in this thesis is twofold. On the first hand, we aim at designing, studying and validating image processing techniques that improve the visualization of stents. On the second hand, we study the processing of curvilinear structures (like guide-wires) for which we propose a new image processing technique. We present algorithms dedicated to the 2D and 3D visualization of stents. Since the stent is hardly visible, we do not intend to directly locate it by image processing means in the images. The position and motion of the stent are inferred from the location of two landmarks: the angioplasty balloon and of the guide-wire, which have characteristic shapes. To this aim, we perform automated detection, tracking and registration of these landmarks. The cornerstone of our 2D stent visualization enhancement technique is the use of the landmarks to perform motion compensated noise reduction. We evaluated the performance of this technique for 2D stent visualization over a large database of clinical data (nearly 200 cases). The results demonstrate that our method outperforms previous state of the art techniques in terms of image quality. A comprehensive validation confirmed that we reached the level of performance required for the commercial introduction of our algorithm. It is currently deployed in a large number of clinical sites worldwide. The 3D stent visualization that we propose, uses the landmarks to achieve motion compensated tomographic reconstruction. We show preliminary results over 22 clinical cases. Our method seems to outperform previous state of the art techniques both in terms of automation and image quality. The previous stent visualization methods involve the segmentation of the part of the guide-wire extending through the stent. We propose a generic tool to process such curvilinear structures that we call the Polygonal Path Image (PPI). The PPI relies on the concept of locally optimal paths. One of its main advantages is that it unifies the concepts of several previous state of the art techniques in a single formalism. Moreover the PPI enables to control the smoothness and the length of the structures to segment. Its parametrization is simple and intuitive. In order to fully benefit from the PPI, we propose an efficient scheme to compute it. We demonstrate its applicability for the task of automated guide-wire segmentation, for which it outperforms previous state of the art techniques
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Lim, Michael H. (Michael Hong). "Development of X-ray lithography and nanofabrication techniques for III-V optical devices." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/16801.
Full textAbstract:
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. [117]-122).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
This dissertation covers the development of fabrication techniques for Bragg-grating-based integrated optical devices in III-V materials. Work on this rich family of devices has largely been limited to numerical analysis because of the difficulties of their fabrication. The challenges of fabrication are addressed by dividing the problem along two lines: (1) development of an advanced x-ray mask system that addresses future nanolithography needs, and (2) development of fabrication techniques that addresses problems specific to Bragg-grating-based filters. A new x-ray mask configuration is described that improves many aspects of the x-ray mask. A novel means of measuring nondestructively x-ray mask distortion on a global scale was developed, called holographic phase-shifting interferometry (HPSI). This system, in conjunction with appropriate thermal input can potentially provide active correction of x-ray mask distortion. Current microphotonic fabrication issues are presented along with a detailed description of the dual-layer hardmask process (DLHP). The development of the DLHP was specifically geared towards the special requirements of Bragg-grating based microphotonics. Taken as a whole the author hopes that this dissertation serves to facilitate the building of advanced future integrated-optical devices.
by Michael Lim.
Sc.D.
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Chembrolu, Venkatesh. "Time-resolved X-ray imaging of magnetization dynamics in spin transfer torque devices /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Bismuth, Vincent. "Image processing algorithms for the visualization of interventional devices in X-ray fluoroscopy." Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST1062/document.
Full textAbstract:
La pose de stent est l'option de traitement la plus courante de la maladie coronarienne, l'une des principales causes de mortalité dans le monde. Lors d'une procédure de pose de stent, le médecin insère des outils chirurgicaux dans le réseau vasculaire du patient. La progression de ces outils a l’intérieur du corps est suivie en temps réel sous uroscopie par rayons X. Trois outils, en particulier, jouent un rôle crucial dans la procédure : le guide, le ballon d'angioplastie et le stent. Le guide apparaît dans les images sous la forme d'une structure curviligne ne. Le ballon, monte sur le guide, est équipé de deux marqueurs radio-opaques à ses extrémités. Le stent est un maillage métallique qui se projette en une forme complexe dans les images uroscopiques. Le stent, dont le bon déploiement est essentiel au succès du geste médical, est souvent très difficilement visible dans les images. Les travaux présentés dans cette thèse poursuivent un double objectif. Il s'agit d'une part, de concevoir, d’étudier et de valider des techniques de traitement d'image visant à améliorer la visualisation des stents. D'autre part, nous étudions la traitement des structures curvilignes (comme les guides) pour lesquelles nous proposons un nouvel outil. Nous présentons des algorithmes de traitement d'image dédiés a la visualisation 2D et3D des stents. Nous sommes amenés, dans ce but, à détecter, suivre et recaler, de manière complètement automatique, les outils nécessaires a la pose de stent que sont le guide et le ballon. Le stent étant a peine visible dans les images, nous ne cherchons pas à le localiser directement à l'aide de techniques de traitement d'images. La position et le mouvement du stent sont déterminés par nos algorithmes […]. Nous avons évalué la performance des ces outils pour la visualisation des stents en 2D, sur une large base de près de 200 cas cliniques. Il en ressort que notre méthode surpasse les méthodes utilisées jusqu'ici sur le plan de la qualité image. La validation exhaustive que nous avons menée, confirme que nous avions atteint un niveau compatible avec son introduction commerciale. Le logiciel qui en résulte est désormais installé sur un grand nombre de sites cliniques, ou il est régulièrement utilisé. La méthode de visualisation 3D des stents que nous proposons utilise les marqueurs pour effectuer une reconstruction tomographique compensée en mouvement. Nous exposons des résultats préliminaires sur une base de 22 cas cliniques. Il semble que notre méthode surpasse les méthodes précédemment employées aussi bien du point de vue de la qualité d’image que de l'automatisation. Les méthodes de visualisation des stents que nous proposons s’appuient sur la segmentation de la portion du guide qui traverse le stent. Nous proposons un nouvel outil pour le traitement de telles structures curvilignes que nous appelons : l'Image de Chemins Polygonaux (acronyme PPI en anglais). Cet outil repose sur la notion de chemin localement optimal. L'un des principaux avantages du PPI est d’unir dans un même cadre différents concepts pré-existants. De plus, il permet de contrôler la régularité et la longueur des structures à traiter avec une paramétrisation simple et intuitive. Avant de tirer pleinement parti des performances du PPI nous proposons un schéma algorithmique efficace pour le calculer. Nous illustrons ces utilisation pour la segmentation automatique de guide où il surpasse les techniques existantesStent implantation is the most common treatment of coronary heart disease, one of the major causes of death worldwide. During a stenting procedure, the clinician inserts interventional devices inside the patient's vasculature. The navigation of the devices inside the patient's anatomy is monitored in real-time, under X-ray fluoroscopy. Three specific interventional devices play a key role in this procedure: the guide-wire, the angioplasty balloon and the stent. The guide-wire appears in the images as a thin curvilinear structure. The angioplasty balloon, that has two characteristic markerballs at its extremities, is mounted on the guide-wire. The stent is a 3D metallic mesh, whose appearance is complex in the fluoroscopic images. Stents are barely visible, but the proper assessment of their deployment is key to the procedure. The objective of the work presented in this thesis is twofold. On the first hand, we aim at designing, studying and validating image processing techniques that improve the visualization of stents. On the second hand, we study the processing of curvilinear structures (like guide-wires) for which we propose a new image processing technique. We present algorithms dedicated to the 2D and 3D visualization of stents. Since the stent is hardly visible, we do not intend to directly locate it by image processing means in the images. The position and motion of the stent are inferred from the location of two landmarks: the angioplasty balloon and of the guide-wire, which have characteristic shapes. To this aim, we perform automated detection, tracking and registration of these landmarks. The cornerstone of our 2D stent visualization enhancement technique is the use of the landmarks to perform motion compensated noise reduction. We evaluated the performance of this technique for 2D stent visualization over a large database of clinical data (nearly 200 cases). The results demonstrate that our method outperforms previous state of the art techniques in terms of image quality. A comprehensive validation confirmed that we reached the level of performance required for the commercial introduction of our algorithm. It is currently deployed in a large number of clinical sites worldwide. The 3D stent visualization that we propose, uses the landmarks to achieve motion compensated tomographic reconstruction. We show preliminary results over 22 clinical cases. Our method seems to outperform previous state of the art techniques both in terms of automation and image quality. The previous stent visualization methods involve the segmentation of the part of the guide-wire extending through the stent. We propose a generic tool to process such curvilinear structures that we call the Polygonal Path Image (PPI). The PPI relies on the concept of locally optimal paths. One of its main advantages is that it unifies the concepts of several previous state of the art techniques in a single formalism. Moreover the PPI enables to control the smoothness and the length of the structures to segment. Its parametrization is simple and intuitive. In order to fully benefit from the PPI, we propose an efficient scheme to compute it. We demonstrate its applicability for the task of automated guide-wire segmentation, for which it outperforms previous state of the art techniques
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Mclean, Ivan Hugh. "An adaptive discrete cosine transform coding scheme for digital x-ray images." Thesis, Rhodes University, 1989. http://hdl.handle.net/10962/d1002032.
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The ongoing development of storage devices and technologies for medical image management has led to a growth in the digital archiving of these images. The characteristics of medical x-rays are examined, and a number of digital coding methods are considered. An investigation of several fast cosine transform algorithms is carried out. An adaptive cosine transform coding technique is implemented which produces good quality images using bit rates lower than 0.38 bits per picture element
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Buchanan, James David Ralph. "The chemical and magnetic structural characterisation of magneto-resistive devices using X-ray techniques." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/4046/.
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The academic and industrial interest in magnetic data storage has been fuelled by the information age. The number of applications for magnetic thin-films has increased rapidly, along with the popularity of using X-ray techniques as a tool by which to characterise them. Structural characterisation is a key process to their development and understanding, correlating chemical and magnetic structure to magneto-transport. In this thesis a number of magneto-resistive devices are studied, including spin-valves, magnetic tunnel junctions and magnetic multilayers. The credence of using grazing incidence X-ray techniques for characterisation is initially demonstrated by accounting for variations in MR from nominally identical spin-valves, through observing subtle fluctuations in the pinning NiO layer thickness. The study of magnetic tunnel junctions has revealed discrepancies in barrier thickness as measured by X-ray reflectivity and through fits to the 1-V profile using Simmons’ model. This demonstrates localised tunnelling and the inaccuracy of 1-V modelling in determining average barrier thickness. Specular reflectivity and diffuse analysis have also determined a far larger than expected level of intermixing across Al bilayer interfaces with Al on X and X on Al, where X are transition metals from groups 3,4 and 5 of the periodic table. AF coupled multilayers are studied using polarised neutron reflectivity, the results of which have been compared directly with the relatively new technique: resonant soft X- ray magnetic scattering (SoXMaS). Specular and diffuse scattering studies reveal striking discrepancies between the two techniques, due to differences between the relative magnetic to chemical cross sections. Simulations further demonstrate SoXMaS and its sensitivity to magnetic structure. Finally, reflectivity data from Co/Cu Bragg peaks are used to calculate the refractive index of Co across the Co Lm and Ln edge under different magnetisation orientations.
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Leal, Michael J. "Effect of pixel size and scintillator on image quality of a CCD-based digital x-ray imaging system." Link to electronic thesis, 2001. http://www.wpi.edu/Pubs/ETD/Available/etd-0502101-123456.
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Farmand, Maryam. "X-ray Absorption Spectroscopy Characterization of Electrochemical Processes in Renewable Energy Storage and Conversion Devices." Thesis, The George Washington University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3557518.
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The development of better energy conversion and storage devices, such as fuel cells and batteries, is crucial for reduction of our global carbon footprint and improving the quality of the air we breathe. However, both of these technologies face important challenges. The development of lower cost and better electrode materials, which are more durable and allow more control over the electrochemical reactions occurring at the electrode/electrolyte interface, is perhaps most important for meeting these challenges. Hence, full characterization of the electrochemical processes that occur at the electrodes is vital for intelligent design of more energy efficient electrodes.
X-ray absorption spectroscopy (XAS) is a short-range order, element specific technique that can be utilized to probe the processes occurring at operating electrode surfaces, as well for studying the amorphous materials and nano-particles making up the electrodes. It has been increasingly used in recent years to study fuel cell catalysts through application of the Δ&mgr; XANES technique, in combination with the more traditional X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques. The Δ&mgr; XANES data analysis technique, previously developed and applied to heterogeneous catalysts and fuel cell electrocatalysts by the GWU group, was extended in this work to provide for the first time space resolved adsorbate coverages on both electrodes of a direct methanol fuel cell. Even more importantly, the Δ&mgr; technique was applied for the first time to battery relevant materials, where bulk properties such as the oxidation state and local geometry of a cathode are followed.
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Magnan, François. "Sulphur- & Nitrogen-Containing π-Conjugated Organic Molecules as Potential Semiconductors for Optoelectronic Devices." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36754.
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Organic semiconductors (OSCs), compared to the more traditional silicon, are enticing materials for the fabrication of optoelectronic devices (e.g., transistors, photovoltaic cells, light-emitting diodes) due notably to the lower cost associated with their preparation and purification, as well as their increased solubility in solvents which can accommodate large-scale fabrication. However, a higher degree of molecular disorder typically results in lower performance than silicon and remains an issue to be adressed. As the structure of an OSC is crucial to its performance, understanding the nature of this structure-property relationship is key to further the field of OSCs. In this regard, this thesis explores the optoelectronic properties of different π-conjugated organic frameworks which incorporate sulphur and nitrogen atoms along the rigid conjugated backbone for their desirable impacts on charge mobilities and stability.
After a brief review of both small-molecule OSCs as well as key experimental techniques employed in the course of this work, chapter three covers the synthesis and characterization of dithiatetrazocines (DTTA), electron-deficient sulphur-nitrogen heterocycles, which were functionalized with various (oligo)thienyls pendants. The impact of both the substitution patterns and the degree of conjugation on the optoelectronic and solid-state properties of the ring system was investigated.
The fourth chapter expands on previous work from the Brusso group that focused on extending the 2D conjugation of tetrathienoanthracene. While oligothienyls were previously shown to effectively increase the degree of conjugation, little to no change in device performance were observed, which was ascribed to disorder of the rotatable pendants. Here, rigid thieno[3,2-b]thiophene was used instead to increase both the degree of conjugation while maintaining structural rigidity, as assessed by optical, electrochemical and theoretical studies.
The fifth chapter introduces preliminary work toward expanding the electron-deficient hexaazatrinaphtylene core with thiophene rings. The resulting concentric donor-acceptor structure promotes luminescent behavior with pronounced emission solvatochromism. Optical measurements were performed before and after intramolecular cyclization of the thiophene rings, to study the impact of aromatization on the optoelectronic properties of the system.
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Kevin, Punarja. "On the synthesis, measurement and applications of solar energy materials and devices." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/on-the-synthesis-measurement-and-applications-of-solar-energy-materials-and-devices(9273d60d-cc5a-4992-8fae-ac9ddefa506b).html.
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Second generation solar cells based on thin film semiconductors emerged as a result of the past ten years of intense research in the thin film preparation technology. Thin film solar cell technology can be cost effective as it uses comparatively cheap materials suitable for solar building integration. Chemical Vapour Deposition (CVD) is a well-known method for the deposition of high quality thin films. This thesis describes the synthesis of novel tin(II)dithiocarbamate [Sn(S2CNEt2)2] and bis(diphenylphosphinediselenoato) tin(II) [Sn(Ph2PSe2)2] and these complexes as single source precursor for the deposition of SnS and SnSe and by using the combination of [Sn(Ph2PSe2)2] with [Cu(acac)2], Cu2SnSe3 thin films were deposited by AACVD. By using suitable combinations of metal complexes ([nBu2Sn(S2CNEt2)2], [Cu(S2CNEt2)2] [Zn(S2CNEt2)2] [Zn(Se2CNEt2)2] [Zn(acac)2], [Sn(OAc)4], [Cu(PPh3){Ph2P(Se)NP(Se)Ph2}] thin films and nanocomposites of CZTS, CFTS, CZTSe, CFTSe, CZFTS, , CZFTSe, CZTSSE, CFTSSe and CZFTSSe were prepared. The effect of precursor concentration and deposition temperature on the structure, morphology and composition of the thin films were studied in detail using by powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and elemental mapping. This thesis addressing the structural inhomogeneity, control of growth and material characterization is expected to yield closer performance parity between CZTS-Se and CIGS solar cells. A series of systematic experiments were carried out. Through AACVD and simple solvothermal methods CZFTS nanoparticles and thin films were prepared. The simple, potentially, low-cost nature of the CZTS nanoparticles and the enhancement of charge carrier mobility achieved suggest that these nanoparticles have potential in the improvement of OFETs and perhaps other organic electronic devices.
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Smith, Stephen James. "Development of transition edge sensor distributed read-out imaging devices for applications in X-ray astronomy." Thesis, University of Leicester, 2006. http://hdl.handle.net/2381/30586.
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This thesis is concerned with the development of, position-sensitive, Transition Edge Sensors (TES) operating at cryogenic temperatures (~ 0.1 K). The Distributed Read-Out Imaging Device (DROID) concept uses TES read-out at both ends of a linear X-ray absorber, to derive, through heat diffusion, both spectral and spatial information. Potentially, DROIDs offer a simpler technological alternative to the development of large area pixel arrays for future X-ray space observatories (Chapter 1). Chapter 2 presents a comprehensive review of the theory of microcalorimeter detectors. A finite-element model is established in Chapter 3, to numerically simulate the response of the DROID to an X-ray photon, as well as the noise spectral density at the detector outputs, including frequency dependent correlations between the two TESs. In Chapter 4 this model is used to implement pre-existing algorithms, based on the use of the optimal filter, to calculate the position and energy resolution along the length of experimental DROID designs. We show that these algorithms do not lead to optimum performance under all conditions and then derive the true optimal filters, based on least-squares minimisation of the total noise power in the DROID. By numerical simulation we show that significant improvements in both the energy and in particular, the position resolution, are theoretically possible. The design and experimental characterisation of two prototype DROIDs are described in Chapter 6 and 7, using the equipment described in Chapter 5. The first X-ray results from a prototype TES DROID, using single TES read-out, are reported. These results demonstrate proof of concept, confirming spatial sensitivity along the DROID, through the actual spectral and spatial resolutions are limited by the availability of only a single read-out channel.
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Xiao, Ting [Verfasser], and Marcus [Gutachter] Bär. "X-ray spectroscopic study of heterostructure contacting schemes for optoelectronic devices / Ting Xiao ; Gutachter: Marcus Bär." Cottbus : BTU Cottbus - Senftenberg, 2019. http://d-nb.info/1197614079/34.
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Tudge, Mark Vernon. "Long and short term effects of X-rays on charge coupled devices." Thesis, Brunel University, 1996. http://bura.brunel.ac.uk/handle/2438/10450.
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EEV buried channel charge coupled devices (BC CDs) with technological variations have been studied with respect to their response to 70kVp X-rays. Process variations considered are the conventional BCCD, scintillator coated BCCDs (Gadox(Eu) and Csl(Tl)) and the inversion mode device. The work was made necessary by the use of these CCDs for dental X-ray imaging. Effects investigated include changes in device operating voltages and dark current. The dark current buildup has been characterised in terms of a prompt component seen immediately following irradiation, and a time dependent component which occurs gradually. A major part of this work was the determination of the location and concentration of the energy states responsible for this dark current buildup. Also a novel aspect of the work was the derivation of an expression describing the time dependent component as a function of time and temperature. Effects associated with the bias dependence of the BCCD have also been considered, with particular regard to the effect of a negative substrate bias, and the theoretical explanation has been developed. The findings of this work have demonstrated the suitability of these devices for the commercial application of imaging X-rays for dentistry.
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Murray, Bryon Michael. "Determination of eye dose from personnel monitoring devices in medical institutions." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17040.
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Boudlali, Hana. "Analysis of Electroanatomic Mapping System Accuracy Using X-Ray Reconstruction of Electrode Locations in a Porcine Animal Model." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2237.
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Fluoroscopy is considered the gold standard for locating catheters during cardiac electrophysiology (EP) procedures. However, fluoroscopy emits ionizing radiation which can lead to adverse health effects when exposed to in high doses (World Health Organization, 2016). Electroanatomic mapping (EAM) systems display the three-dimensional location of EP catheters and measure the local electrical activity of the heart. They can minimize a physician’s reliance on fluoroscopy and can help reduce radiation exposure during a case (Casella, 2011).
EAM systems are diagnostic medical devices that inform the placement of ablation therapy and must accurately locate catheters to be deemed safe. Test methods to determine EAM system accuracy should be compared back to a gold standard, such as fluoroscopy. Fluoroscopy only provides a two-dimensional image of the catheter location, which is not a suitable ground truth for measuring the three-dimensional accuracy of EAM systems. X-Ray Reconstruction of Electrode Locations (XRROEL) calculates the true three-dimensional catheter location by performing a coordinate transform on two-dimensional fluoroscopy images. This thesis outlines the development and validation of the XRROEL method in a porcine animal model, and describes how XRROEL can be applied to optimize the location accuracy of electroanatomic mapping system algorithms.
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Paganestis, Antonios. "Investigation of the performance of microstrip gas detectors for X-rays and evaluation of their application to mammography." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266593.
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Albertini, Caio Marcos de Moraes. "Estudo prospectivo de eventos tromboembólicos após reoperações de alta complexidade em estimulação cardíaca artificial definitiva." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/5/5156/tde-26032018-125007/.
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INTRODUÇÃO: Estenose e obstruções venosas são achados frequentes após o implante de cabos-eletrodos transvenosos. Manifestações clínicas dessas lesões venosas, entretanto, são raramente reportadas. Embora exista consenso de que fenômenos tromboembólicos sejam mais comuns após reoperações que envolvam o implante de novos cabos-eletrodos ou procedimentos de extração transvenosa, ainda não existem evidências que comprovem essa observação. OBJETIVOS: Em pacientes submetidos a reoperações para corrigir disfunção em cabos-eletrodos ou para mudar o modo de estimulação, o estudo visou identificar: a) a incidência de tromboembolia pulmonar (TEP) e de trombose venosa profunda (TVP) do membro superior ipsilateral ao procedimento; b) a prevalência de lesões venosas prévias ao procedimento cirúrgico, pelo estudo venográfico, e a ocorrência de modificações desse padrão seis meses após o procedimento; e c) fatores prognósticos para a ocorrência dos eventos clínicos e das alterações venográficas. MÉTODOS: No período de abril de 2013 a julho de 2016 foram estudados 84 pacientes. A avaliação pré-operatória incluiu: ultrassonografia com doppler dos membros superiores, angiotomografia de tórax com protocolo para TEP, venografia por subtração digital e coleta de biomarcadores laboratoriais específicos do sistema de coagulação e hemostasia. Os exames diagnósticos foram repetidos no momento pós-operatório para detectar os desfechos do estudo. Todos os pacientes foram acompanhados por 12 meses. Os desfechos primários foram a ocorrência de TEP ou TVP em até 30 dias após o procedimento. Os desfechos secundários foram as alterações venográficas no sexto mês após a intervenção cirúrgica. Na análise da associação das variáveis demográficas, clínicas, operatórias e laboratoriais com os desfechos do estudo, empregou-se os testes Qui-quadrado, Exato de Fisher ou \"t\" de Student. Modelos de regressão logística multivariados foram utilizados para identificar fatores prognósticos. RESULTADOS: Entre os 84 pacientes incluídos, houve equilíbrio entre os sexos e a idade média de 59,3 ± 15,2 anos. O principal motivo para realizar o procedimento cirúrgico foi a disfunção de cabos-eletrodos (75%). A remoção de cabos-eletrodos foi efetuada em 52,4% dos casos. A taxa de eventos clínicos e subclínicos pós-operatórios foi de 35,7%, representada por TVP em 24 (28,6%) casos e TEP em seis (7,1%). Alterações no padrão venográfico seis meses após a operação foram identificadas em 34,5% dos pacientes. Os fatores prognósticos independentes para TVP foram: a presença de circulação colateral significativa na venografia pré-operatória ([odds ratio (OR) = 4,7]), (intervalo de confiança de 95% (IC 95%); 1,1 - 19,8; P = 0,037), a extração transvenosa de cabos-eletrodos (OR = 27,4; IC 95%; 5,8 - 128,8; P < 0,0001) e o aumento do fibrinogênio no pós-operatório (OR = 1,02; IC 95%; 1,01 - 1,03; P = 0,018). O histórico de tabagismo foi o único fator prognóstico relacionado com a ocorrência de TEP (OR = 14,6; IC 95%; 2,3 - 91,8; P = 0,004). Somente a extração transvenosa de cabos-eletrodos foi fator prognóstico independente (OR = 5,0; IC 95%; 1,6 - 15,4; P = 0,004) para alterações venográficas pós-operatórias. CONCLUSÃO: Reoperações envolvendo o manuseio de território venoso com cabos-eletrodos previamente implantados apresentam elevados índices de complicações tromboembólicas e de alterações venográficas. Extração transvenosa de cabos-eletrodos apresentou impacto significativo no desenvolvimento de TVP e de alterações venográficas. Esses resultados mostram a necessidade de novos estudos específicos para avaliar o papel de estratégias preventivas para esse subgrupo de pacientesINTRODUCTION: Venous stenosis or occlusion is a frequent finding in patients with previously-implanted transvenous leads. Clinical manifestations of these venous lesions, however, are rarely reported. Although there is a consensus that thromboembolic events are more frequent after reoperation involving the implantation of new leads or lead removal, there is still no evidence to support this observation. OBJECTIVES: In patients submitted to reoperations due to lead dysfunction or device upgrade, the study aimed to determine: a) the incidence of pulmonary embolism (PE) and upper extremity deep venous thrombosis (UEDVT) ipsilateral to the cardiac device; b) the prevalence of venous lesions determined by preoperative venography, and the occurrence of modifications or progression of these lesions six months after the procedure; and c) prognostic factors for clinical and venographic outcomes. METHODS: From April/2013 to July/2016, 84 patients were studied. The preoperative evaluation included: upper extremity venous ultrasound, computed tomography pulmonary angiography, digital subtraction venography and specific laboratory tests for coagulation and hemostasis. Diagnostic exams were repeated postoperatively to detect the study outcomes. All patients were followed for 12 months. Primary outcomes were occurrence of PE or UEDVT within 30 days after the procedure. Secondary outcomes were venographic changes six months after the surgical intervention. Student\'s t test, Chi-square or Fisher\'s Exact test were used in the univariate analysis of demographic, clinical, operative and laboratory variables. Multivariate logistic regression models were used to identify prognostic factors. RESULTS: Among the 84 patients included, there was a balance between gender and the mean age was 59.3 ± 15.2 years. Lead malfunctioning (75%) was the main surgical procedure indication. Lead removal was performed in 52.4% of the cases. The rate of postoperative clinical and subclinical events was 35.7%, represented by UEDVT in 24 (28.6%) cases and PE in 6 (7.1%). Alterations in the venography findings six months after the surgery were identified in 34.5% of the patients. Independent prognostic factors for UEDVT were: the presence of significant collateral circulation in the preoperative venography ([odds ratio (OR)= 4.7; [95% confidence interval (CI): 1.1 - 19.8; P=0.037), transvenous lead extraction (OR= 27.4; 95% CI 5.8-128.8; P < 0.0001) and fibrinogen variation (OR= 1.02; 95% CI 1.01 - 1.03; P=0.018). Smoking history was the only prognostic factor related to the occurrence of PE (OR= 14.6; 95% CI 2.3 - 91.8; P=0,004). Transvenous lead extraction was the only independent prognostic factor (OR= 5.0; 95% CI 1.6 - 15.4; P=0.004) for postoperative venographic endpoints. CONCLUSION: Reoperations involving previously transvenous implanted leads present high rates of thromboembolic complications and venographic alterations. Transvenous lead extraction had a significant impact on the development of UEDVT and venographic alterations. These results show the need for further studies to evaluate the role of preventive strategies for this subgroup of patients
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Greenlee, Jordan Douglas. "Study of cation-dominated ionic-electronic materials and devices." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53401.
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The memristor is a two-terminal semiconductor device that is able to mimic the conductance response of synapses and can be utilized in next-generation computing platforms that will compute similarly to the mammalian brain. The initial memristor implementation is operated by the digital formation and dissolution of a highly conductive filament. However, an analog memristor is necessary to mimic analog synapses in the mammalian brain. To understand the mechanisms of operation and impact of different device designs, analog memristors were fabricated, modeled, and characterized. To realize analog memristors, lithiated transition metal oxides were grown by molecular beam epitaxy, RF sputtering, and liquid phase electro-epitaxy. Analog memristors were modeled using a finite element model simulation and characterized with X-ray absorption spectroscopy, impedance spectroscopy, and other electrical methods. It was shown that lithium movement facilitates analog memristance and nanoscopic ionic-electronic memristors with ion-soluble electrodes can be key enabling devices for brain-inspired computing.