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Dissertations / Theses on the topic 'Scanning electron microscopy'
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Davies, D. G. "Scanning electron acoustic microscopy." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304042.
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Harland, C. J. "Detector and electronic developments for scanning electron microscopy." Thesis, University of Sussex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370435.
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Snella, Michael T. "Drift correction for scanning-electron microscopy." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62605.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 91-92).
Scanning electron micrographs at high magnification (100,000x and up) are distorted by motion of the sample during image acquisition, a phenomenon called drift. We propose a method for correcting drift distortion in images obtained on scanning electron and other scanned-beam microscopes by registering a series of images to create a drift-free composite. We develop a drift-distortion model for linear drift and use it as a basis for an affine correction between images in the sequence. The performance of our correction method is evaluated with simulated datasets and real datasets taken on both scanning electron and scanning helium-ion microscopes; we compare performance against translation only correction. In simulation, we exhibit a 12.5 dB improvement in SNR of our drift-corrected composite compared to a non-aligned composite, and a 3 dB improvement over translation correction. A more modest 0.4 dB improvement is measured on the real image sets compared to translation correction alone.
by Michael T. Snella.
M.Eng.
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McKeown, Karen. "Using scanning electron microscopy (SEM) and transmission electron nncroscopy." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492019.
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Electron impact excitation collisions are important processes for spectral line formation of plasmas. The work undertaken in this thesis focuses on such collisions involving Li-like ions, important in both astrophysical and magnetically confined plasmas. By having reliable atomic and collisional data, such as energy levels, radiative rates and excitation rate coefficients, it is possible to generate models to describe such plasmas. The atomic data were calculated using the General-Purpose Relativistic Structure Program (GRASP; Dyall et al 1989), for several Li-like ions, namely S XIV, Ar XVI, Ca XVIII, Ti XX, Cr XXII, Fe XXIV and Ni XXVI. Including relativistic effects in the calculations leads to the generation of 24 fine-structure energy levels when orbitals with 11,/ =:; 5 are considered. Oscillator strengths, were generated for all 276 transitions arising amongst these levels when maintaining a frozen core of Is2 • Comparisons were made with both theoretical and experimental data available from the publications of Nahar & Pradhan (1999), Nahar (2002), Whiteford et al (2002) and Del Zanna (2006), along with NIST data. Collisional calculations were performed for Fe XXIV, an abundant ion in solar and fusion plasmas, which has the potential to be employed in photo-pumping schemes for X-ray lasers. The calculations were performed using the Dirac Atomic Relativistic Code (DARC; Ait-Tahar, Grant & Norrington 1996), which is a fully relativistic code based on R-matrix theory. In addition to carrying out these calculations, DARC was further developed to provide a solution to the problem of convergence which affects optically allowed transitions in the above threshold energy region. Comparison of these results was made with data already available in the literature, with discrepancies being highlighted and discussed. The work of Berrington & Tully (1997) did not include the n=5 orbital, and comparisons with the results presented here showed how important these are for low temperatures. Discrepancies between this work and that of Whiteford et al (2002) were also identified. Despite being given access to their unpublished data, the source of the identified discrepancies remains elusive. The problems identified require further investigation which lies beyond the scope and resources of the present work.
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Morgan, Scott Warwick. "Gaseous secondary electron detection and cascade amplification in the environmental scanning electron microscope /." Electronic version, 2005. http://adt.lib.uts.edu.au/public/adt-NTSM20060511.115302/index.html.
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Findlay, Scott David. "Theoretical aspects of scanning transmission electron microscopy /." Connect to thesis, 2005. http://eprints.unimelb.edu.au/archive/00001057.
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Nellist, Peter David. "Image resolution improvement in scanning transmission electron microscopy." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361613.
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Stevens, Sam. "Understanding Porous Crystal Growth By Scanning Electron Microscopy." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532223.
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Ramasse, Quentin Mathieu. "Diagnosis of aberrations in scanning transmission electron microscopy." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615070.
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Waller, Deborah. "Environmental scanning electron microscopy of freezing aqueous solutions." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613409.
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Löfgren, André. "Detection of electron vortex beams : Using a scanning transmission electron microscope." Thesis, Uppsala universitet, Materialteori, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-255330.
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Electron vortex beams (EVBs) are electron beams with a doughnut-like intensity profile, carrying orbital angular momentum due to their helical phase shift distribution. When employed in an electron microscope, they are expected to be efficient for the detection of magnetic signals. In this report I have investigated high angle annular dark field (HAADF) images obtained using EVBs. This was done for 300 K and 5K. For 5 K, I also compared HAADF images from an ordinary electron beam with HAADF images from an electron vortex beam. What was found was that EVBs produced doughnuts around the atomic columns. However, when taking the size of the electron source into account, this phenomena could no longer be observed. When comparing images from EVBs with images from ordinary electron beams, I found that the intensity of scattered electrons around atomic columns was broader for EVBs. This was persistent even after taking the source size into account.Elektronvirvelstrålar (EVS) är elektronstrålar med en munk-liknande intensitetsprofil. Dessa bär på rörelsemängdsmoment på grund av sin fasdistribution. När de används i ett elektronmikroskop förväntas de vara effektiva för detektering av magnetiska signaler. I denna uppsats har jag undersökt high angle annular dark field (HAADF) bilder som erhållits med hjälp av EVS. Detta gjordes för 300 K och 5K. För 5 K, jämförde jag även HAADF bilder från en vanlig elektronstråle med HAADF bilder från en elektronvirvelstråle. Vad jag fann var att EVS producerade en munkformad intensitetsfördelning runt atomerna. Men när hänsyn till storleken på elektronkällan togs i beaktande kunde inte detta fenomen observeras längre. När bilder från EVS jämfördes med bilder från vanliga elektronstrålar, fann jag att intensiteten av spridda elektroner runt atomkolumnerna var bredare för EVS. Detta kunde observeras även efter att jag tagit hänsyn till elektronkällans storlek.
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Ekwall, Hans. "Electron microscopy of cryopreserved boar spermatozoa : with special reference to cryo-scanning electron microscopy and immunocytochemistry /." Uppsala : Dept. of Clinical Sciences, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/2007123.pdf.
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Xiao, Juan. "Development of electron tomography on liquid suspensions using environmental scanning electron microscopy." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI050/document.
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La Microscopie Electronique à Balayage Environnementale permet l'observation de liquides dans certaines conditions de pression et température. En travaillant en transmission, i.e. en mode STEM (Scanning Transmission Electron Microscopy), des nano-objets présents au sein du liquide peuvent même être analysés (mode « Wet-STEM»). Dans les solutions concentrées, l'arrangement du soluté peut changer être un paramètre microstructural important, qu’il est alors nécessaire de caractériser. Dans ce contexte, le but de ce travail est de développer la tomographie électronique sur des suspensions liquides en utilisant le mode STEM en ESEM, de manière à obtenir la structure 3D de nano-objets dispersés dans un liquide. Dans une première partie, le contraste entre des nanoparticules et le film d’eau est étudié en combinant des images expérimentales Wet-STEM (en 2D) et des simulations Monte Carlo. Deux types de nano-matériaux sont choisis : des nanoparticules d’or sphériques, de diamètre environ 40 nm, dispersées dans l’eau, ainsi qu’une suspension aqueuse de latex SBA-PMMA, contenant 3% de PMMA utilisé comme tensioactif stérique. La comparaison entre les résultats simulés et expérimentaux permet d’estimer comment le contraste entre l’eau et les nanomatériaux est affecté par l’épaisseur du film d’eau. Dans une deuxième partie, des expériences de tomographie sont réalisées à sec sur des films de polyuréthane contenant des nanotubes de carbone multiparois greffés ou non, en utilisant une platine développée précédemment au laboratoire. Le volume a pu être reconstruit correctement. Cependant, en effectuant une acquisition 3D sur des suspensions de latex SBA-PMMA, le contrôle de la température de l’échantillon s’est révélé insuffisant. Nous proposons une amélioration à la fois de la platine et des conditions d’observations permettant de mieux contrôler l’évaporation et la condensation de l’eau sur des échantillons liquides. La troisième partie est dévolue à une analyse approfondie d’une suspension de latex SBA-PMMA, de différentes concentrations (d’un état dilué à très concentré), les acquisitions étant effectuées avec les conditions optimisées. L’arrangement des particules de latex est comparé à des modèles issus de la littérature, et avec des résultats expérimentaux obtenus par cryo-SEM sur suspensions congelées. Nous présentons ensuite une étude du même latex en présence de tensioactif. La couche de tensioactif peut être mise en évidence dans les volumes reconstruits et segmentés. En conclusion, nous résumons les potentialités de la tomographie wet-STEM pour la caractérisation de nanomatériaux solides et liquides. Des perspectives sont proposées pour continuer dans l’exploration de ces potentialités et des limites de la techniqueESEM (Environmental Scanning Electron Microscopy) allows the observation of liquids under specific conditions of pressure and temperature. When working in the transmission mode, i.e. in STEM (Scanning Transmission Electron Microscopy), nano-objects can even be analyzed inside the liquid (“wet-STEM” mode). Moreover, in situ evaporation of water can be performed to study the materials evolution from the wet to the dry state. This work aims at developing electron tomography on liquid suspensions using STEM-in-ESEM, to obtain the 3D structure of nano-objects dispersed in a liquid. In a first part, Monte Carlo simulations and 2D wet-STEM experimental images are combined to study the contrast. Two kinds of liquid nano-materials are chosen as the sample: spherical gold particles (diameter around 40 nm) in suspension in water; latex SBA-PMMA suspension, a copolymer derived from styrene and metacrylic acid esters in aqueous solution, 3% PMMA shell included as steric surfactant. The comparison between simulated and experimental results helps to determine how water can affect the contrast of hydrated nano-materials. Tomography experiments are then performed on dry PU-carbon nanotubes nanocomposites using a previously developed home-made tomography device, and the volume is well reconstructed. When performing tomography on latex suspension, limitations are found on the temperature control of samples. We propose an optimization of the device with new observations conditions to better control water evaporation and condensation of liquid samples. Afterwards, a full 3D analysis on SBA-PMMA latex from dilute suspension to very concentrated one is performed, and a further study is presented in presence of a surfactant. The encouraging reconstruction results are used to model the particles arrangement. This shows the potentialities of wet-STEM tomography for the characterization of both solid and liquid nano-materials
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Chen, Li. "Fabrication of electron sources for a miniature scanning electron microscope." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313904.
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Rakian, Audrey. "Scanning Electron Microscopy and Histological Evaluation of Flow Divertors." Scholarly Repository, 2007. http://scholarlyrepository.miami.edu/oa_theses/108.
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The purpose of this study is to evaluate the endothelialization, exclusion of the aneurysm from circulation and intra-aneurysmal thrombus formation induced by the implantation of endovascular flow divertors for the purpose of bridging aneurysms. The design of the flow divertors was based on previous in vitro hemodynamic experiments in aneurysm models. The significance of this work is manifested in the development of a minimally invasive technology that may be employed for aneurysm treatment. Divertors with two different filament sizes and three different porosities were implanted in the rabbit elastase-induced aneurysm model and their effectiveness evaluated both angiographically and histologically. Preliminary results demonstrated that it is possible to achieve substantial reduction in intraaneurysmal flow immediately after device deployment. Angiographically, the aneurysms were excluded from the circulation with the medium and low porosity devices. In addition, the device performed as expected: smooth deployment, no intralumenal clot formation, and exclusion of aneurysm from the circulation without occluding other arterial branches. Additional data is needed to make definitive conclusions regarding endothelialization and the formation of a neointima.
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Wan, Quan. "Scanning electron microscopy investigation of bio-polymer composites morphology." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19125/.
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The development of nano-composite materials puts higher demand on morphological analysis techniques. The bio-nano-composite material systems is among the most challenging nano-composite materials for morphology characterization due to its sensitivity to damage, complex molecular conformations and nano-structures. The aim of this project is to provide a nanometer resolution and convenient chemical mapping tool based on scanning electron microscope (SEM) and electron spectroscopy for complex bio-composite systems. This would combine the backscattered electron and secondary electron techniques based on the angle-selection and energy-filtering methods. Theoretical electron behavior in the SEM is calculated using Monte Carlo simulations for reference. This SEM technique is validated and applied on representative artificial and natural bio-composite systems. Poly(N-isopropylacrylamide) (PNIPAM) composite material is a family of widely applied temperature-responsive bio-materials. The phase separation and morphology in PNIPAM nano-composites can affect the bio-compatibility of material system. Silk fiber is a well known natural bio-material with exceptional properties as well as a model hierarchical material system. The organization of nano-repeating unit in silk is expected to be a key factor in the mechanical property formation. Direct chemical mapping of this organization was not available up to now in convenient methods. Our SEM techniques (secondary electron hyperspectral imaging, SEHI) were validated and applied for mapping of these bio-materials and provided high-resolution chemical characterization of their nano-structures. The application of SEM techniques were further extended to different silk fibers and artificial silk materials. Such experiment validated the complex fine structure of secondary electron spectra measured on silk materials. The comparison of the electron spectra in different silk materials suggested a possible reflection of protein conformation in secondary electron spectra and this may be exploited for characterization of such complex materials in future applications. In summary, SEM analysis technique using electron selective detection methods capable of nano-resolution chemical characterization were validated and applied on nano-bio-composite materials. These techniques show great potential for morphological analysis in complex and sensitive composite materials in the future.
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Jian, Nan. "Scanning transmission electron microscopy of atomic structure of nanoparticle." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7131/.
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This thesis presents the researches on the size and atomic structure of the nanoclusters including ligand protected monometallic clusters, ligand protected bimetallic clusters and biological metallic clusters, by using aberration corrected HAADF -STEM. The atom counting method with size selected clusters as mass balance was utilized to "fractionate" the relative broad distributed sample and make the structure study focus on the certain size range. The atomic structures of Auss Schmid clusters were investigated. Nearly half of these clusters were found to have a hybrid structure. A combination of geometric size analysis and atom counting method was performed to determine both the size and composition of the AuAg alloy clusters. We found that Ag-rich clusters tend to have an icosahedral structure while the Au-rich clusters prefer the fcc structure. For the biological nanoparticles, the ferritins' iron loadings were obtained. Different morphologies of the ferritin iron cores were observed as a function of iron loading, suggesting the iron core growth process in the protein shell. The HAADF -STEM was also successfully employed to characterize the ultra-small Au and Pd catalysts supported on the Ti02, which are helpful to understand the catalytic performance of these catalysts. A multilayer deposition method was developed to accommodate and process the large abundance of clusters from the new high-flux cluster source. With the similar experimental setup, size-selected colloidal clusters were produced by dissolving the multilayer cluster-PVP stacks. The colloidal clusters were observed by the STEM and their sizes were found to be conserved during the dissolving process.
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Zheng, Tao. "Investigation of plant tissue by environmental scanning electron microscopy." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609068.
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Hrubanová, Kamila. "Scanning Electron Microscopy and its Applications for Sensitive Samples." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-409082.
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Předložená dizertační práce s názvem “Rastrovací elektronová mikroskopie a její aplikace pro senzitivní vzorky” pojednává o problematice rastrovací elektronové mikroskopie v kontextu instrumentálního a metodologického vývoje vedoucího k inovativnímu řešení, které je dobře aplikovatelné zejména v mikrobiologickém výzkumu. Součástí práce je rozprava o historii a současném stavu elektronové mikroskopie (EM) jakožto vědecké zobrazovací a analytické techniky, tato část se nachází v úvodních kapitolách. Nepopiratelný přínos EM v biologických a lékařských oborech je dokazován mnoha citovanými vědeckými publikacemi. Předložená dizertační práce přináší novinky z oblasti přípravy preparátů a kryogenní rastrovací elektronové mikroskopie (cryo-SEM) vyvinuté na pracovišti Ústavu přístrojové techniky AV ČR, v.v.i. v Brně. Jedná se především o návrhy a výrobu speciálních držáků vzorků a vývoj nových metodik v oblasti přípravy mikrobiologických preparátů vedoucích k nalezení optimálních parametrů jednotlivých procesů. V experimentální části se nachází ověření metodologických postupů při studiu hydratovaných a na elektronový svazek senzitivních preparátů. Následné srovnání různých přístupů na definovaném biologickém systému z oblasti mikrobiologie přispívá k rozšíření interpretace doposud známých výsledků. Mezi zkoumanými mikrobiologickými kmeny byly biofilm-pozitivní bakterie Staphylococcus epidermidis a kvasinky jako Candida albicans a Candida parapsilosis, jež jsou považovány za klinicky významné, protože se podílejí na vzniku závažných infekcí zejména u imunokompromitovaných pacientů. Dále byl studován vliv růstu biofilmu bakterie Bacillus subtilis na biodeteriorizaci a biodegradaci poly--kaprolaktonových fólií. Vývoj v oblasti cryo-SEM byl aplikován ve výzkumu mikrobů s biotechnologickým potenciálem, jako jsou např. Cupriavidus necator a Sporobolomyces shibatanus.
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Liu, Yangmingyue. "Scanning Electron Microscopy To Probe Working Nanowire Gas Sensors." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1256.
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This study is dedicated to the implementing of Electron-Beam-Induced Current (EBIC) microscopy to study the behavior of metal oxide semiconducting (MOS) nanowire (NW) gas sensor in situ under exposure to different environment. First, we reported the development of a single nanowire gas sensor compatible with an environmental cell. The major component of the device we use in this study is a single SnO2 nanowire attached to an electron transparent SiN membrane (50-100 nm thick), which was used for mounting nanowire working electrodes and surface imaging of NW. First the NW's conductivity is investigated in different temperatures. Higher temperature is proved to cause higher conductivity of NW. We also found that often the Schottky barrier is formed at the nanowire's contacts with Au and Au/Cr electrodes. Then NW's responses to gas and electron beam (from SEM) are analyzed quantitatively by current measurement. Electron-Beam-Induced Current technique was introduced for the first time to characterize the conductivity behavior of the nanowire during the gas sensing process. Resistive contrast was observed in the EBIC image.
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Martín, Malpartida Gemma. "Combined Transmission Electron Microscopy and In-Situ Scanning Tunneling Microscopy Characterization of Nanomaterials." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663184.
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The main goal of this thesis has been to apply in-situ Transmission Electron Microscopy (TEM) electrical measurements using a Scanning Tunneling Microscopy (STM) tip, combined with TEM imaging and spectroscopic techniques, in order to address the characterization of relevant nanomaterials. This system has not only been used to measure electrical properties, but also to carry out in-situ experiments with Joule heating and to apply mechanical stresses.
A review of the different in-situ TEM techniques, their development over the years and their impact in the scientific community has been presented. Moreover, the instrumental used in this thesis, in particular, the TEM-STM system, has been described. In addition, two techniques for the preparation of specific samples for in-situ TEM-STM experiments have been presented: for nanostructured samples (2D materials, nanowires, etc), and for localized samples (devices, thin layers, bulk samples, etc). A gridcase that allows the use of conventional TEM grids in the TEM-STM system has been designed and fabricated in the context of this thesis. The use of this homemade gridase has allowed us to improve the experiments, offering more reproducibility and versatility. Finally, the calibration of the electrical measurements of the system has been carried out.
Using the TEM-STM system, different type of nanostructures have been characterized during the present thesis, from 2D nanostructures, as the elucidation of the effects of electrical current through a single graphene oxide sheet, to functional devices, as the study of the ferroelectric and piezoelectric behavior of structures based on La2WO6, the study of the anisotropic electrical conductivity of GaInP CuPtB type ordering layers used for multijunction solar cells or the study of the conductive filament (CF) formation mechanism in three different Resistive random-access memory (ReRAM) devices.
In summary, in-situ microscopy expands the horizons of the characterization and study of materials and, in particular, in the context of this thesis, an in-situ TEM-STM system has been used to electrically characterize samples from nanomaterials to functional devices.En aquesta Tesi, s'ha emprat una tècnica de Microscopia Electrònica de Transmissió (TEM, Transmission Electron Microscopy en anglès) in-situ que permet realitzar mesures elèctriques utilitzant una sonda de microscòpia d'efecte túnel (STM, Scanning Tunneling Microscopy en anglès), tot combinant-la amb imatge TEM i tècniques d'espectroscòpia. A més, aquest sistema no només s'ha utilitzat per a mesurar les propietats elèctriques, sinó també per a dur a terme experiments in-situ amb escalfament per efecte Joule o aplicant una tensió mecànica a la superfície de la mostra. D'aquesta manera s'han pogut caracteritzar nanomaterials, des de nanoestructures 2D, estudiant l’efecte del pas de corrent a través d'un sol full d'òxid de grafè, fins a dispositius completament funcionals, com la caracterització piezoelèctrica i ferroelèctrica de capes primes d'òxids funcionals lliures de plom, l'estudi de l’anisotropia en la conductivitat d’estructures ternàries III-V ordenades utilitzades en cèl·lules solars tàndem multicapa i l'estudi amb TEM de la formació de filaments conductors (CF) i del mecanisme de commutació resistiva en tres dispositius ReRAM diferents. En els diferents capítols d'aquesta tesi s'ha donat resposta a problemes de ciència de materials amb l'ajut d'una tècnica de TEM in-situ tot combinant-la amb altres tècniques d'espectroscòpia i difracció. El desenvolupament d'aquesta tècnica ha permès caracteritzar les propietats del materials a nivell nano.
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William, Gerald Martin. "The study of electronic materials for light emitting devices using scanning cathodoluminescence electron microscopy." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289377.
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Behan, Gavin Joseph. "Optical sectioning in the aberration-corrected scanning transmission and scanning confocal electron microscope." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:10c7151c-ff1f-4f88-a783-9ad5cf4831ec.
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This thesis concerns the experimental application of the technique of optical sectioning in the aberration-corrected scanning transmission electron microscope (STEM). Another aim was to perform optical sectioning experiments on the still relatively new scanning confocal electron microscope (SCEM). To test the feasibility of this technique, experiments were performed on a variety of samples to measure the achievable depth response. Deconvolution methods were explored in an attempt to further improve the depth response. Finally, some of the first optical sectioning experiments were performed in the SCEM using both elastic and inelastically scattered electrons. The results showed a clear need to investigate confocal electron microscopy due to the missing cone problem for incoherent imaging in the STEM. This is particularly evident when imaging objects of greater width than the STEM probe. Confocal electron microscopy using inelastic electrons appeared to be a promising imaging mode for the future with this thesis consisting of early work in the field.
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Bélisle, Jonathan. "Design and assembly of a multimodal nonlinear laser scanning microscope." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100765.
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The objective of this thesis is to present the fabrication of a multiphoton microscope and the underlying theory responsible for its proper functioning. A basic introduction to nonlinear optics will give the necessary knowledge to the reader to understand the optical effects involved. Femtosecond laser pulses will be presented and characterized. Each part of the microscope, their integration and the design of the microscope will be discussed. The basic concepts of laser scanning microscopy are also required to explain the design of the scanning optics. Fast scanning problems and their solutions are also briefly viewed. As a working proof, the first images taken with the microscope will be presented. Fluorescent beads, rat tail tendon, gold nanoparticles and pollen grain images using various nonlinear effects will be shown and discussed.
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Risnes, Ole Kristian. "Ex-situ and in-situ characterisation of polypropylene fibre morphology by scanning probe microscopy and environmental scanning electron microscopy." Thesis, Heriot-Watt University, 2003. http://hdl.handle.net/10399/419.
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Jenkins, L. "Development of environmental scanning electron microscopy for textile hydration studies." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.605085.
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The possibility of supporting a saturated water vapour atmosphere together with the presence of liquid water in the Environmental Scanning Electron Microscope (ESEM) presents new opportunities for the observation of water-textile interactions. It is important to understand such interactions because they will affect many manufacturing and performance processes, including dyeing, finishing, comfort and washing behaviour. Control of temperature and pressure conditions surrounding the sample in the ESEM allows the performance of in situ hydration experiments at high magnification and resolution. Many organic materials are very susceptible to the effects of the beam in an electron microscope. Beam specimen interactions will change the nature and therefore behaviour of the sample. Experiments with cellulosic fibres showed that some of the visible signs of damage are identical to those indicating interaction with water. These signs include smoothing of the fibre surfaces, and loss of surface and edge detail. Experiments were performed to investigate the effect of various experimental parameters on the time of onset of damage. From the results of these experiments, conditions were found which delayed the onset of visible damage for 40-50 minutes. Using the damage-free conditions, mounting and hydration techniques were developed which allow the observation of cross-section area increase in fibres as they interact with liquid water. The results obtained for the lyocell fibres chosen for these experiments show good agreement with similar swelling experiments in the optical microscope performed to confirm the temperature independence of swelling at low temperature. The possibility of assessing the effect of packing density on swelling using the same hydration technique has also been investigated, but limitations of the mounting method prevent the acquisition of useful data for this purpose. A method has been developed for the observation of the wetting behaviour of various textile fabrics. It has been shown that the ESEM provides a quick and easy method of comparing the behaviours of sample materials. Ability to interpret the images produced in the microscope depends on a knowledge of wetting processes. Conditions have been found which allow the condensation of water droplets onto individual textile fibres. Initial assessment has been made to determine the suitability of the ESEM micrographs for the measurement of contact angles.
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Fletcher, A. L. "Cryogenic developments and signal amplification in environmental scanning electron microscopy." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599080.
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This thesis describes the development of a cryogenic imaging system for an environmental scanning electron microscope (ESEM). The ESEM is an important new development in electron microscopy since it enables specimens to be viewed in a small pressure of gas - generally this gas is water vapour, although an alternative must be used for cryogenic applications. The presence of the gas also contributes to the imaging mechanism, a process whereby the signal electrons are amplified by the gaseous molecules prior to detection. The purpose of the cryogenic system was to image the complicated, four phase microstructure of ice cream. Although viewed routinely by conventional electron microscopy techniques, the harsh temperature and pressure regimes involved (around -120°C at 10.6 torr) increase the likelihood of introducing artefacts. Therefore, a methodology was developed for imaging ice cream with ESEM in a small pressure of an alternative imaging gas at a much warmer temperature of -80°C. In order to stabilise the ice phase in the samples at a higher temperatures, a system was designed for mixing gases, so that a small amount of water vapour could be mixed into the imaging gas. This system lifted the temperature restrictions of ice cream imaging so it can, in principle, now be imaged at its storage temperature of -20°C. In the search for alternative imaging gases to water vapour, questions were raised about the fundamental way in which the signal electrons interact with the gas. In order to understand the electron amplification properties of the different gases, a Faraday cage was designed and the electron amplification was investigated. We suggest that the ratio of the peak amplification to the plateau amplification gives a semi-quantitative method of determining the imaging quality of the gas. Furthermore, by isolating experimentally the effects of different components of the signal, it was found that the low energy secondary electrons dominate the signal at low pressure, whereas the effect of backscattered electrons becomes more important as the pressure is raised. In addition, the performance of two ESEM detector designs were compared. The new gaseous secondary electron detector (GSED), which was designed to reduce the contribution of some sources of signal, was found to achieve its aim, but some of its overall contrast was sacrificed when compared to the original environmental secondary detector (ESD).
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Kershaw, Matthew James. "Wettability and fluid absorption studies utilising environmental scanning electron microscopy." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423651.
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Jones, Lewys. "Applications of focal-series data in scanning-transmission electron microscopy." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:a6f2a4d5-e77a-47a5-b2d7-aab4b7069ce2.
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Since its development, the scanning transmission electron microscope has rapidly found uses right across the material sciences. Its use of a finely focussed electron probe rastered across samples offers the microscopist a variety of imaging and spectroscopy signals in parallel. These signals are individually intuitive to interpret, and collectively immensely powerful as a research tool. Unsurprisingly then, much attention is concentrated on the optical quality of the electron probes used. The introduction of multi-pole hardware to correct optical distortions has yielded a step-change in imaging performance; now with spherical and other remnant aberrations greatly reduced, larger probe forming apertures are suddenly available. Probes formed by such apertures exhibit a much improved and routinely sub-Angstrom diffraction-limited resolution, as well as a greatly increased probe current for spectroscopic work. The superb fineness of the electron beams and enormous magnifications now achievable make the STEM instrument one of the most sensitive scientific instruments developed by man, and this thesis will deal with two core issues that suddenly become important in this new aberration-corrected era. With this new found sensitivity comes the risk of imaging-distortion from outside influences such as acoustic or mechanical vibrations. These can corrupt the data in an unsatisfactory manner and counter the natural interpretability of the technique. Methods to identify and diagnose this distortion will be discussed, and a new technique developed to restore the corrupted data presented. Secondly, the subtleties of probe-shape in the multi-pole corrected STEM are extensively evaluated via simulation, with the contrast-transfer capabilities across defocus explored in detail. From this investigation a new technique of STEM focal-series reconstruction (FSR) is developed to compensate for the small remnant aberrations that still persist – recovering the sample object function free from any optical distortion. In both cases the methodologies were developed into automated computer codes and example restorations from the two techniques are shown (separately, although in principal the scan-corrected output is compatible with FSR). The performance of these results has been quantified with respect to several factors including; image resolution, signal-noise ratio, sample-drift, low frequency instability, and quantitative image intensity. The techniques developed are offered as practical tools for the microscopist wishing to push the performance of their instrument just that little bit further.
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Kauko, Hanne. "Quantitative scanning transmission electron microscopy studies on heterostructured GaAs nanowires." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23864.
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This thesis presents a quantitative high-angle annular dark eld scanning transmission electron microscopy (HAADF STEM) study on heterostructured GaAs-based nanowires (NWs). Quantitative HAADF STEM was employed to investigate Sb concentration variations in axial GaAsSb inserts within GaAs NWs and in GaAsSb NWs, as well as Al concentration variations in the AlGaAs shell in GaAs/AlGaAs core-shell NWs. The NWs were grown with the vapor-liquid-solid (VLS) growth mechanism using Ga- and Au-assisted molecular beam epitaxy (MBE). Compositional characterisation by quantitative HAADF STEM was realized by comparing experimental image intensities normalized to the incident beam intensity with simulated intensities. The HAADF STEM image simulations were performed using the frozen-phonon multislice approach. For correct compositional analysis of GaAs1-ySby, static atomic displacements (SAD) had to be included in the simulations, however this was not the case with AlxGa1-xAs. GaAsSb inserts within GaAs NWs and GaAsSb NWs were studied with non-corrected STEM at a relatively low magnication using NWs in plane. In this case the known thickness prole of the hexagonal NWs could be exploited in the quantitative HAADF STEM analysis. In the GaAsSb inserts, concentration gradients axially along as well as radially across the insert were identied. The Sb concentration in the insert decreased axially towards the upper and lower interfaces with GaAs, and radially towards the outer surfaces. The axial concentration gradients were attributed to the reservoir eect related to the VLS growth process. The eects of the axial concentration gradients on the NWs optical properties were investigated. The radial concentration gradients in the GaAsSb inserts result from a combined eect of radial GaAs overgrowth and out-diusion of Sb during the post-insert axial GaAs growth, causing an increased surface depletion of Sb with increasing post-insert GaAs growth time. In GaAsSb NWs, increased surface depletion of Sb towards the bottom of the NW was observed, and this was attributed to out-diusion of Sb during the NW growth. GaAs/AlGaAs core-shell NWs were studied with aberration corrected STEM, using cross-sectional specimens prepared with ultramicrotomy. A method for mapping Al concentration in AlxGa1-x As at unit cell spatial resolution using the atomic resolution HAADF STEM images was developed. The method is independent of the eective source size and higher order lens aberrations. With the method, Al concentration variations in the AlGaAs shell could be quantied at unit cell spatial resolution.
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Muellejans, Harald. "Secondary electron emission in coincidence with primary energy losses." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240071.
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Krajnak, Matus. "Advanced detection in Lorentz microscopy : pixelated detection in differential phase contrast scanning transmission electron microscopy." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/7906/.
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Modern devices require fundamental length scales to be analysed in a maximum detail to enable research of new types of phenomena and design new materials. In this thesis, an advancement in Lorentz microscopy will be presented where the focus was placed not only onto resolution in spatial space but also onto resolution in reciprocal space. This allows greater sensitivity to measurements of the integrated magnetic induction within thin samples. This was achieved by a novel approach to the data acquisition, where instead of a segmented (annular) detector, a pixelated detector was used to measure the deflection of the scanning transmission microscopy (STEM) probe due to the in-plane integrated magnetic induction. Computer vision algorithms were researched to find an efficient, noise-robust way to register the deflection of the STEM probe. This enabled a novel approach to data analysis, where a scatter of the 2D integrated induction (a bivariate histogram) is used to show the distribution of the magnetic induction vector. The experimental results are supported by simulations, where a model of a thin polycrystalline sample causes a shift of the simulated beam due to phase modulations. The results of the detection in both the simulation and experiment showed that cross-correlation based processing can efficiently separate the low spatial frequencies (from the in-plane magnetic induction), and high spatial frequencies (from the structure of the polycrystalline sample). This work will enable quantitative analysis of a greater number of thin magnetic samples, for which the current methods are hampered by the diffraction contrast. This will be particularly helpful for the study low moment, out of plane, magnetised thin films. Currently such systems are of great interest due to the tunability of their magnetic properties and the novel magnetic structures present within them. This work also provides an important step for computational methods in transmission electron microscopy, as this is one of the first examples of 4D data acquisition of processing in STEM (where two dimensions represent the spatial scanning dimensions and other two the reciprocal space). Imaging methods developed in this thesis were applied to the topic of skyrmions in a thin layer of a FeGe cubic helimagnet, where the very fine detail of the structure of their in-plane integrated magnetic induction was shown to contain a distorted modulations of its profile. This was compared to a simple three harmonic frequency model, which was altered to fit some characteristics of the imaged magnetic skyrmions. In this work, for the first time, a direct comparison of differential phase contrast and electron holography will be shown for a simple experiment in which the integrated electric field between two needles was measured in free space in the same microscope. Although it was concluded that both methods are equivalent, some small discrepancies of measured values were present due to a long range electric field in electron holography and/or drift of the beam in between scans in STEM.
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Schroeder-Reiter, Elizabeth. "High resolution analysis of mitotic metaphase chromosomes with scanning electron microscopy." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-27942.
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Kola, B. O. "Development of an image processing workstation for scanning Auger electron microscopy." Thesis, University of York, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374183.
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He, Dongsheng. "Quantitative scanning transmission electron microscopy characterisation of size-selected gold clusters." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4743/.
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This thesis presents a systematic study on the three-dimensional atomic structures of the size-selected gold (Au) using aberration-corrected scanning transmission electron microscopy (STEM), fitted with a high angle annular dark field (HAADF) detector. The work involves experimental quantification of the microscope, HAADF-STEM image modeling and cluster structure identification. The study explores the cluster structure distribution as a function of experimental conditions and investigates their structural stability by electron beam irradiation. The Au clusters studied were produced by inert gas aggregation, size-selected by a lateral time-of-flight filter and soft-landed on thin amorphous carbon films. A quantitative image analysis methodology has been developed for rapid cluster structure identification, which involves direct comparison of atomic-resolved experimental images with simulated images. Applying the method to over two thousand individually imaged Au887 clusters (each containing nominal 887 gold atoms) revealed a distribution of structural isomers including icosahedron, decahedron and FCC structures. It was found that the isomer distribution depended critically on the cluster formation conditions. A quick condensation condition led clusters with icosahedral structure, while the slow condensation was favoured by clusters with FCC structure. In addition, the stability of Au887 clusters under the electron beam irradiation was investigated by following electron beam induced structural transformation in situ. The transformation sequence was found to be dominated by icosahedron to decahedron to FCC structure. The results provide insights to the understanding of cluster growth mechanism and dynamic behaviour at atomic scale, enabling the ability to control the three dimensional atomic structures of clusters.
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Bera, Sagorika. "Analysis of Antibody-Induced Plasmodium falciparum Sporozoites Through Scanning Electron Microscopy." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6679.
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Malaria is a devastating disease that continues to affect millions of people worldwide every year. Specifically, Plasmodium falciparum is the most common human malaria parasite, particularly in sub-Saharan Africa. P. falciparum causes the most malignant and debilitating symptoms with the highest mortality and complication rates. Even with the worldwide efforts of many researchers and organizations, the road to discovering a vaccine has been difficult and challenging. Due do to the improvements in in vitro liver stage assays as well as rodent models of mammalian malaria, pre-erythrocytic stages of malaria have become a more accessible target for experimental studies. These vaccine candidates target Plasmodium sporozoites in the liver and liver stages to prevent development to the blood-stage forms, which is responsible for the debilitating symptoms of the disease. Scanning electron microscopy has been used for decades to provide insight on the morphology and topography of specimens, which cannot be seen through a light microscope. The purpose of this study was to analyze the morphology of sporozoites with some target antibodies. Sporozoites have previously shown uncharacterized appearances and development in an immunofluorescent stain at different concentrations of particular antibodies. With this further understanding on the morphological impact few of the target antibodies have on sporozoites through scanning electron microscopy, further grasp can be acquired.
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Marturi, Naresh. "Vison and visual servoing for nanomanipulation and nanocharacterization using scanning electron microscope." Thesis, Besançon, 2013. http://www.theses.fr/2013BESA2014/document.
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Avec les dernières avancées en matière de nanotechnologies, il est devenu possible de concevoir, avec une grande efficacité, de nouveaux dispositifs et systèmes nanométriques. Il en résulte la nécessité de développer des méthodes de pointe fiables pour la nano manipulation et la nano caractérisation. La d´étection directe par l’homme n’ étant pas une option envisageable à cette échelle, les tâches sont habituellement effectuées par un opérateur humain expert `a l’aide de microscope électronique à balayage équipé de dispositifs micro nano robotiques. Toutefois, en raison de l’absence de méthodes efficaces, ces tâches sont toujours difficiles et souvent fastidieuses à réaliser. Grâce à ce travail, nous montrons que ce problème peut être résolu efficacement jusqu’ à une certaine mesure en utilisant les informations extraites des images. Le travail porte sur l’utilisation des images électroniques pour développer des méthodes automatiques fiables permettant d’effectuer des tâches de nano manipulation et nano caractérisation précises et efficaces. En premier lieu, puisque l’imagerie électronique à balayage est affectée par les instabilités de la colonne électronique, des méthodes fonctionnant en temps réel pour surveiller la qualité des images et compenser leur distorsion dynamique ont été développées. Ensuite des lois d’asservissement visuel ont été développées pour résoudre deux problèmes. La mise au point automatique utilisant l’asservissement visuel, développée, assure une netteté constante tout au long des processus. Elle a permis d’estimer la profondeur inter-objet, habituellement très difficile à calculer dans un microscope électronique à balayage. Deux schémas d’asservissement visuel ont été développés pour le problème du nano positionnement dans un microscope électronique. Ils sont fondés sur l’utilisation directe des intensités des pixels et l’information spectrale, respectivement. Les précisions obtenues par les deux méthodes dans diff érentes conditions expérimentales ont été satisfaisantes. Le travail réalisé ouvre la voie à la réalisation d’applications précises et fiables telles que l’analyse topographique,le sondage de nanostructures ou l’extraction d’ échantillons pour microscope électronique en transmissionWith the latest advances in nanotechnology, it became possible to design novel nanoscale devicesand systems with increasing efficiency. The consequence of this fact is an increase in the need for developing reliable and cutting edge processes for nanomanipulation and nanocharacterization. Since the human direct sensing is not a feasible option at this particular scale, the tasks are usually performedby an expert human operator using a scanning electron microscope (SEM) equipped withmicro-nanorobotic devices. However, due to the lack of effective processes, these tasks are always challenging and often tiresome to perform. Through this work we show that, this problem can be tackle deffectively up to an extent using the microscopic vision information. It is concerned about using the SEM vision to develop reliable automated methods in order to perform accurate and efficient nanomanipulation and nano characterization. Since, SEM imaging is affected by the non-linearities and instabilities present in the electron column, real time methods to monitor the imaging quality and to compensate the time varying distortion were developed. Later, these images were used in the development of visual servoing control laws. The developed visual servoing-based autofocusing method ensures a constant focus throughout the process and was used for estimating the inter-object depth that is highly challenging to compute using a SEM. Two visual servoing schemes were developed toperform accurate nanopositioning using a nanorobotic station positioned inside SEM. They are basedon the direct use of global pixel intensities and Fourier spectral information respectively. The positioning accuracies achieved by both the methods at different experimental conditions were satisfactory.The achieved results facilitate in developing accurate and reliable applications such as topographic analysis, nanoprobing and sample lift-out using SEM
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Furnival, Thomas. "Single atom imaging with time-resolved electron microscopy." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270314.
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Developments in scanning transmission electron microscopy (STEM) have opened up new possibilities for time-resolved imaging at the atomic scale. However, rapid imaging of single atom dynamics brings with it a new set of challenges, particularly regarding noise and the interaction between the electron beam and the specimen. This thesis develops a set of analytical tools for capturing atomic motion and analyzing the dynamic behaviour of materials at the atomic scale. Machine learning is increasingly playing an important role in the analysis of electron microscopy data. In this light, new unsupervised learning tools are developed here for noise removal under low-dose imaging conditions and for identifying the motion of surface atoms. The scope for real-time processing and analysis is also explored, which is of rising importance as electron microscopy datasets grow in size and complexity. These advances in image processing and analysis are combined with computational modelling to uncover new chemical and physical insights into the motion of atoms adsorbed onto surfaces. Of particular interest are systems for heterogeneous catalysis, where the catalytic activity can depend intimately on the atomic environment. The study of Cu atoms on a graphene oxide support reveals that the atoms undergo anomalous diffusion as a result of spatial and energetic disorder present in the substrate. The investigation is extended to examine the structure and stability of small Cu clusters on graphene oxide, with atomistic modelling used to understand the significant role played by the substrate. Finally, the analytical methods are used to study the surface reconstruction of silicon alongside the electron beam-induced motion of adatoms on the surface. Taken together, these studies demonstrate the materials insights that can be obtained with time-resolved STEM imaging, and highlight the importance of combining state-ofthe- art imaging with computational analysis and atomistic modelling to quantitatively characterize the behaviour of materials with atomic resolution.
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Staniewicz, Lech Thomas Leif. "Transmission-mode imaging in the environmental scanning electron microscope (ESEM." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/242281.
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Electron microscopy was first conducted in the 1930s with the advent of theTEM and later the STEM. In 1969, the first commercial SEM was released,with the possibility of retrofitting it to behave like a STEM following soonafterwards. In 1979, Danilatos and Robinson advanced electron microscopyby creating a new type of SEM which allowed a controlled quantity of gasinto the sample chamber, termed ESEM. The most recent evolution in thisline was the combination of ESEM and STEM in 2005, a procedure termedWet STEM.The focus of this work is on investigating applications of this new technique,along with the contrast mechanisms involved in forming an image. Tothat end, a wide variety of samples will be imaged. Clay and paint suspensions(colloids) are used to test Wet STEM’s capacity to image submergedobjects, as well as thin objects which are stacked together. Diblock copolymerfilms are used to test Wet STEM’s ability to distinguish chemically similarmaterials without staining, the physical effects of heavy metal staining andto demonstrate the necessity of gas for the purpose of charge neutralisation. Single cell biological samples are also investigated. Internal contrast inmammalian cells is visible without recourse to staining, but chemical fixationis required despite maintaining a high relative humidity. Bacteria are moreresilient and as such are easier to image than animal cells, requiring no priortreatment. When exposed to low relative humidity, bacteria are found tocollapse. The collapse pattern is observed to differ between wild-type andcytoskeletal-deficient bacteria of the same species and strain, so it is likelythat dehydration-induced collapse offers information about the position andshape of the bacterial cytoskeleton.
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Heller, Eric. "Ultra low signals in ballistic electron emission microscopy." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1060979803.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xvii, 237 p.; also includes graphics. Includes abstract and vita. Advisor: Jonathan P. Pelz, Dept. of Physics. Includes bibliographical references (p. 232-237).
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Kersell, Heath R. "Alternative Excitation Methods in Scanning Tunneling Microscopy." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1449074449.
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Bjørge, Ruben. "Scanning transmission electron microscopy studies of precipitation in Al-Mg-Ge alloys." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15627.
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Precipitation in three Al-Mg-Ge(-Si-Cu) alloys has been investigated using transmission electron microscopy. The alloy compositions were chosen to be similar to previously studied Al-Mg-Si(-Cu) alloys to facilitate direct comparison. These alloys are strengthened by the precipitation of nanometresized, needle-shaped particles during heat treatment. A deeper understanding of precipitation at the atomic level is required in order to achieve greater control over alloy properties. The precipitation in the investigated Al-Mg- Ge(-Si-Cu) alloys was found to share similarities with that in Al-Mg-Si(-Cu) alloys, but there were also significant differences. The high atomic number of Ge relative to Al, Mg, and Si made Al-Mg-Ge alloys highly suited for study by the atomic-number sensitive technique high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM). This was the most important technique employed in this thesis. The use of a state-of-the-art aberration-corrected microscope also made it possible to resolve details previously inaccessible. A near-hexagonal network of Ge columns when viewed along the needle direction was a unifying feature of all the precipitates in these alloys, as is the case in the metastable precipitates of the Al-Mg-Si(-Cu) alloy system. However, the β__ phase, the most important hardening phase in Al-Mg-Si alloys, was not observed. Instead, hardnesses similar to that of comparable Al-Mg-Si(-Cu) alloys were achieved through other precipitate phases. Two Al-Mg-Ge alloys were the main objects of study in this thesis: one Mg-rich and one Ge-rich, with an addition of Mg and Ge in the relation Mg2Ge and Mg5Ge6, respectively. Precipitate phases that form in overaged Al-Mg-Si alloys were observed around peak hardness in these Al-Mg-Ge alloys, as well as disordered precipitates. The precipitate phases known from Al-Mg-Si, U1 and β_, were finer and more coherent with the Al matrix in the Al-Mg-Ge alloys than their counterparts in Al-Mg-Si. These precipitates also displayed highly interesting interface structures, consisting of Ge atoms in columns not part of the bulk precipitate structure. The β_-like precipitate phase that was observed in the Mg-rich alloy was investigated by quantitative HAADF STEM. This method makes it possible to obtain quantitative compositional information from the specimen. It was found that the Ge-rich columns contained significantly less Ge than the Si columns of β_ in Al-Mg-Si alloys. A partial replacement of Ge by Al or vacancies might explain the smaller lattice parameter of the β_-like phase in Al-Mg-Ge compared with β_ in Al-Mg-Si alloys. Precipitation in an Al-Mg-Si-Ge-Cu alloy was also investigated with HAADF STEM. No repeating unit cell was observed in these precipitates near peak hardness. However, these precipitates contained a hexagonal network consisting of mixed Si and Ge columns with Mg, Al, and Cu columns occurring in between the network columns at specific sites. Structural units consisting of Al, Mg, Si, and Ge were often arranged in an ordered manner.
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Jenei, István Zoltán. "Scanning electron microscopy (SEM) analysis of tribofilms enhanced by fullerene-like nanoparticles." Licentiate thesis, Stockholms universitet, Fysikum, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-82153.
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The beneficiary effects of WS2 inorganic fullerene-like nanoparticles in the lubrication industry were shown in recent years. The incorporation of the nanoparticles into lubricants (oils, greases) is however not straightforward. When two surfaces are sliding against each other and a lubricant is used, a thin layer (tribofilm) is formed on the contact area, which effects the friction process. Lubricants usually contain several additives. These additives can impair the friction reducing behaviour of the WS2 inorganic fullerene-like nanoparticles. This thesis investigates the effects of several additives in the lubrication process by analysing the tribofilms formed on the worn surfaces using energy-dispersive X-ray spectroscopy in a scanning electron microscope.
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Durkin, Richard J. "The investigation and optimisation of signals in high pressure scanning electron microscopy." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259445.
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MacDonald, Kinsey Elizabeth. "Analysis of Frozen Desserts Using Low-Temperature Scanning Electron Microscopy (LT-SEM)." Thesis, Clemson University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10982077.
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Commercial vanilla ice cream and other frozen desserts from the United States were analyzed for ice crystal length using low-temperature scanning electron microscopy (LT-SEM). Average ice crystal length was determined using multiple micrographs of each sample/product. Out of the products tested, 11 out of 15 samples had an average ice crystal length above the consumer sensory threshold limit of 55 µm. Products containing stabilizers tended to have smaller average ice crystal lengths than products without stabilizers. With a few exceptions, lower fat products tended to have larger ice crystals because there was less fat to stabilize the ice crystals. Four brands of frozen dessert were studied in detail: a super-premium ice cream (Brand P), a regular ice cream (Brand R), a dietary high protein ice cream (Brand D), and a non-dairy coconut-based frozen dessert (Brand ND). All brands were purchased from two separate supermarket supply chains (Store I and Store P) and analyzed for ice crystal size, weight loss/shrinkage, melting rate, texture, and sensory characteristics before and after being heat-shocked (HS). Brand P, R, and ND all had mean ice crystal sizes that were not significantly different when purchased from either Store I and Store P. The mean ice crystal size increased after HS for all brands except Brand ND. Brand D and Brand P had the highest melting rates, while Brand ND had a much lower melting rate than the other brands tested. Brand ND had a slight decrease in the average ice crystal size and had a decrease in peak force/hardness after HS, while all other brands had an increase in average ice crystal size and an increase in peak force/hardness after HS. Significance was determined using α = 0.05 for all sensory data. The iciness attribute was found to be significantly affected by both brand and HS and an increase in ice crystal size corresponded with an increase in iciness for most samples. The use of stabilizers and emulsifiers in the brands affected various melting characteristics. Additional research is needed on non-dairy frozen desserts and how their physical and sensorial properties are affected by heat-shock.
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Haibo, E. "Quantitative analysis of core-shell nanoparticle catalysts by scanning transmission electron microscopy." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:19c3b989-0ffb-487f-8cb3-f6e9dea83e63.
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This thesis concerns the application of aberration corrected scanning transmission electron microscopy (STEM) to the quantitative analysis of industrial Pd-Pt core-shell catalyst nanoparticles. High angle annular dark field imaging (HAADF), an incoherent imaging mode, is used to determine particle size distribution and particle morphology of various particle designs with differing amounts of Pt coverage. The limitations to imaging, discrete tomography and spectral analysis imposed by the sample’s sensitivity to the beam are also explored. Since scattered intensity in HAADF is strongly dependent on both thickness and composition, determining the three dimensional structure of a particle and its bimetallic composition in each atomic column requires further analysis. A quantitative method was developed to interpret single images, obtained from commercially available microscopes, by analysis of the cross sections of HAADF scattering from individual atomic columns. This technique uses thorough detector calibrations and full dynamical simulations in order to allow comparison between experimentally measured cross section to simulated ones and is shown to be robust to many experimental parameters. Potential difficulties in its applications are discussed. The cross section approach is tested on model materials before applying it to the identification of column compositions of core-shell nanoparticles. Energy dispersive X-ray analysis is then used to provide compositional sensitivity. The potential sources of error are discussed and steps towards optimisation of experimental parameters presented. Finally, a combination of HAADF cross section analysis and EDX spectrum imaging is used to investigate the core-shell nanoparticles and the results are correlated to findings regarding structure and catalyst activity from other techniques. The results show that analysis by cross section combined with EDX spectrum mapping shows great promise in elucidating the atom-by-atom composition of individual columns in a core-shell nanoparticle. However, there is a clear need for further investigation to solve the thickness / composition dualism.
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Cosgriff, Eireann Catherine. "Image formation mechanisms in three-dimensional aberration-corrected scanning transmission electron microscopy." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:e7ddeaf7-4d16-47d3-9248-3b2cfa7d0a6b.
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This thesis considers the theory and calculations of image formation mechanisms for various modes of three-dimensional imaging in aberration-corrected scanning transmission electron microscopy. Discrete tomography is used to determine and refine the three-dimensional structure of molecular nanowire bundles. The structure determination is expedited by the use of annular dark-field imaging, an incoherent imaging mode which provides directly interpretable images. The development of spherical aberration correctors and the subsequent reduction in probe sizes, including the depth of field, has made optical depth sectioning a feasible technique. The localisation in three dimensions of substitutional impurity atoms in zone-axis imaging is discussed. Both the channelling of the probe and the pre-focussing effect of the atomic column play an important role in determining the depth response of the impurity atom. Interband scattering within a sample is shown to be influential in imaging crystals containing dislocations and optical depth sectioning is explored as a possible option for overcoming surface relaxation effects in the imaging of screw dislocations end-on. The possibility of extending the optical depth sectioning approach using aberration-corrected scanning confocal electron microscopy is discussed. The coherent and incoherent imaging modes, involving elastically and inelastically scattered electrons respectively, are investigated.
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Benetello, Vanessa 1983. "Influência do material obturador e agentes de limpeza pós-obturação na composição e morfologia da dentina radicular decídua." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288602.
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Orientador: Regina Maria Puppin-RontaniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: O objetivo neste estudo foi avaliar o efeito de diferentes pastas obturadoras e agentes de limpeza sobre a dentina radicular de dentes decíduos, sobre: a estrutura molecular; e a morfologia de superfície da dentina radicular em dentes decíduos. Foram utilizadas 80 raízes de dentes decíduos anteriores extraídos por razões clínicas. As coroas foram seccionadas na junção cemento-esmalte e descartadas; e as raízes seccionadas no sentido longitudinal expondo os condutos radiculares, as quais foram planificadas e sonicadas. As raízes foram fixadas com resina composta para facilitar o manuseio, em seguida os condutos foram instrumentados com limas tipo K (15 a 35) e irrigados a cada troca de lima com hipoclorito de sódio a 0,5% + EndoPTC. Então, os espécimes foram distribuídos em 4 grupos de acordo com as pastas obturadoras (n=20): Controle-CP (sem obturação), Calen® espessada com óxido de zinco-CZ, Calcipex II®-CII, Vitapex®-V. Após a obturação, os espécimes foram armazenamentos por 7 dias. Após esse período, as pastas obturadoras foram removidas e os espécimes foram subdivididos em 4 grupos de acordo com os agentes de limpeza (n=5): Controle-CL (Sem limpeza), Etanol-E, Tergenform®-T, Ácido fosfórico-AF 35%...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital
Abstract: The aim of this study was to verify the effect the different filling pastes and cleaning agents in primary dentin root, as: molecular structure and morphologic structure the surface of root dentin in primary teeth. For the study were used 80 anterior primary teeth roots extracted for clinical reasons. The crowns of the teeth were sectioned at cement enamel junction and discarded. The roots were separated longitudinally exposing the root canal, which were ground flat and sonicated. The specimens were fixed using composite resin to facilitate manipulation, and then they were prepared with K-type files size #15-35 and irrigated with of 0.5% sodium hypochlorite solution + EndoPTC cream. Thus, were divided into 4 groups (n=20) according to the filling pastes: Control (without filling), Calen® paste thickened with zinc oxide, Calcipex II®, Vitapex®. Then, the specimens were stored for seven days. After that, filling paste was removed and the specimens were subdivided into 4 cleaning agents groups (n=5): Control (without cleaning agents), Ethanol, Tergenform®, Phosphoric acid (35%)...Note: The complete abstract is available with the full electronic document
Mestrado
Odontopediatria
Mestre em Odontologia
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Jones, Darrell E. "Spontaneous step creation on (001) silicon surfaces studied with scanning tunneling microscopy and low-energy electron microscopy /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487946776020229.
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Åhlund, John. "Electronic and Geometrical Structure of Phthalocyanines on Surfaces : An Electron Spectroscopy and Scanning Tunneling Microscopy Study." Doctoral thesis, Uppsala universitet, Fysiska institutionen, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7802.
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Core- and Valence Photoelectron Spectroscopy (PES), X-ray- and Ultraviolet-Visible Absorption Spectroscopy (XAS and UV-Vis), Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT) calculations are used to study the electronic and geometrical structure of a class of macro-cyclic molecules, Phthalocyanines (Pc), on surfaces. These molecules are widely studied due to their application in many different fields. Multilayer and monolayer coverages of Iron Phthalocyanine (FePc) and metal-free Phthalocyanine (H2Pc) deposited on different surfaces are investigated in order to get insight in the electronic and geometrical structure of the obtained overlayers, of crucial importance for the understanding of the film functionality. Sublimation of molecular thick films on Si(100) and on conducting glass results in films with molecules mainly oriented with their molecular plane orthogonal to the surface. Ex-situ deposited H2Pc films on conductive glass show different molecular orientation and morphology with respect to the vacuum sublimated films. We study the monolayer adsorption structure of FePc and H2Pc and compare our results with other Pc’s adsorbed on graphite. We find that the molecular unit cell and the superstructure is characteristic for each Pc adsorbed on graphite, even if the geometrical size of the compared molecules is the same. The PE- and XA- spectra of FePc on graphite are essentially identical for the mono- and multilayer preparations, evidencing weak intermolecular and molecular-substrate interactions of van der Waals nature. Furthermore, we characterize Pc’s on InSb (001)-c(8x2). The substrate In rows are observed to be the adsorption site for Pc’s. We find that the growth of the two-dimensional islands of FePc is prolonged in the [-110] direction, in contrast to ZnPc adsorbed on the same substrate at room temperature. We interpret this result as an indication that the adsorption is controlled by the substrate corrugation observed at 70 K.