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Dissertations / Theses on the topic 'Electronic Microscope and microscopy'
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Yu, Enhua. "Crossed and uncrossed retinal fibres in normal and monocular hamsters : light and electron microscopic studies /." [Hong Kong : University of Hong Kong], 1990. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13014316.
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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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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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于恩華 and Enhua Yu. "Crossed and uncrossed retinal fibres in normal and monocular hamsters: light and electron microscopic studies." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31232449.
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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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El, Hajraoui Khalil. "Études in-situ dans un microscope électronique en transmission des réactions à l’état solide entre métal et nanofil de Ge." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY012/document.
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Le domaine des nanofils semi-conducteurs est en pleine expansion depuis ces dix dernières années grâce à leurs applications dans de nombreux domaines tels que l’électronique ou la conversion d’énergie. Dans cette étude on part d’une base de nanofil de germanium (le canal), on dépose des contacts métalliques qui seront chauffés par effet joule. Une différence de potentiel est alors appliquée au contact d’entrée (la source), le courant électrique est récupéré et mesuré par le contact de sortie (le drain). Une réaction à l’état solide permet aux atomes du métal de diffuser dans le nanofil. La propagation d'une phase métal/semi-conducteur est suivie dans un microscope électronique en transmission (MET) dont la résolution permet une observation à l’échelle atomique au niveau de la source, le drain et le canal. Les dispositifs caractérisés au cours de ce stage ont été élaborés à partir de deux types de membranes, l’une plane et l’autre avec des trous. Chacune d’entre elles sont constituées d’une couche de nitrate de silicium Si3N4 à leurs surfaces présentant l’avantage d’être transparents aux électrons et isolants au courantSemiconductor nanowires (NWs) are promising candidates for many device applications ranging from electronics and optoelectronics to energy conversion and spintronics. However, typical NW devices are fabricated using electron beam lithography and therefore source, drain and channel length still depend on the spatial resolution of the lithography. In this work we show fabrication of NW devices in a transmission electron microscope (TEM) where we can obtain atomic resolution on the channel length using in-situ propagation of a metallic phase in the semiconducting NW independent of the lithography resolution. We show results on semiconducting NW devices fabricated on two different electron transparent Si3N4 membranes: a planar membrane and a membrane where devices are suspended over holes. First we show the process of making lithographically defined reliable electrical contacts on individual NWs. Second we show first results on in-situ propagation of a metal-semiconductor phase in Ge NWs by joule heating, while measuring the current through the device. Two different devices are studied: one with platinum metal contacts and one with copper contacts. Different phenomena can occur in CuGe NWs during phase propagation
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Romero, Leiro Freddy José. "Poly-articulated microrobotics for correlative AFM-in-SEM microscopy." Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS520.pdf.
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La microscopie corrélative est le résultat de la combinaison de deux ou plusieurs techniques de microscopie pour fournir des informations complémentaires sur un échantillon. En utilisant un microscope électronique à balayage (MEB) et un microscope à force atomique (AFM), la microscopie corrélative AFM-in-SEM permet non seulement la caractérisation 3D d'échantillons observés à l'intérieur d'un MEB, mais aussi la manipulation de micro- et nanostructures avec une très grande précision. Cette technique peut être appliquée à divers échantillons dans les domaines de la biologie, de l'électronique et de la science des matériaux. Bien que les solutions AFM-in-SEM existantes dans l'état actuel soient puissantes, elles nécessitent des utilisateurs experts, elles ne sont pas assez polyvalentes pour être utilisées pour différents types de tâches et elles utilisent des robots AFM cartésiens qui limitent fortement la dextérité et la performance du système d'imagerie. L'objectif de cette thèse est d'étudier et d'expérimenter un concept original d'AFM basé sur la robotique poly-articulée pour la microscopie corrélative AFM-in-SEM. Un système robotique AFM à 6 ddls (3 translations et 3 rotations) est développé et intégré à l'intérieur d'un MEB. La capacité de contrôler 3 positions et 3 rotations d'une sonde AFM de taille micrométrique tout en maintenant le centre de rotation à proximité d'une micro-structure est un véritable défi. Cela est principalement dû aux incertitudes inhérentes à l'assemblage des systèmes micro-robotiques et aux jeux mécaniques dans les articulations du robot qui sont du même ordre de grandeur que la précision requise pour le positionnement de la sonde AFM. Les méthodes d'étalonnage des robots et la théorie du contrôle peuvent cependant surmonter ces limitations, comme le démontre cette thèse. Des stratégies de contrôle et une interface utilisateur sont étudiées pour faire fonctionner le système d'imagerie corrélative multi-ddl de manière polyvalente et intuitive. Plusieurs caractéristiques clés qui vont au-delà de l'état de l'art sont mises en œuvre, notamment - Le contrôle par vision électronique (MEB) permet l'atterrissage rapide et automatisé d'une sonde AFM sur un échantillon de taille micrométrique, avec une robustesse par rapport au grossissement du MEB. L'utilisateur peut sélectionner n'importe quelle région d'intérêt (ROI) sur un échantillon en cliquant simplement sur l'écran du MEB. Quel que soit le grossissement du MEB, l'algorithme de contrôle assure un atterrissage sûr de la sonde AFM sur la région d'intérêt. La surface de l'échantillon peut atteindre plusieurs centimètres carrés et le positionnement peut être réalisé avec une précision micrométrique. - Rotation dans le plan et hors du plan d'un échantillon par rapport à la sonde AFM tout en maintenant le centre de rotation autour de la pointe de l'AFM. Le centre de rotation est défini par l'utilisateur par un clic de souris sur l'écran du MEB. Cette fonction est utile pour les tâches de manipulation et de topographie, ainsi que pour les observations multi-angles d'un échantillon à l'intérieur d'un MEB. - Modes de sélection de la trajectoire et de la vitesse de la sonde AFM. Mode AFM à faible vitesse pour une imagerie topographique détaillée. Mode AFM rapide (4fps) pour des observations dynamiques à l'échelle nanométrique. Les utilisateurs ont également accès aux paramètres de contrôle. Ils peuvent être modifiés en fonction de leurs besoins. - Mode AFM mosaïque pour étendre la zone de balayage de la topographie à l'intérieur d'un MEB. Toutes ces caractéristiques s'appuient sur les travaux de recherche en robotique, mécatronique et contrôle réalisés au cours de la thèse. Ces derniers ont le potentiel d'ouvrir la porte à une nouvelle ère de microscopes à force atomique poly-articulés utilisés en microscopie corrélativeCorrelative microscopy is the result of the combination of two or more microscopy techniques to provide complementary information on a sample. When using a scanning electron microscope (SEM) and an atomic force microscope (AFM), AFM-in-SEM correlative microscopy not only enables the 3D characterization of samples observed inside a SEM, but also the manipulation of micro- and nanostructures with an extremely high precision. This technique can be applied to various samples in biology, electronics and materials science. Although existing AFM-in-SEM solutions in the current state of the art are powerful, they require expert users; they are not versatile enough to be used for different types of tasks; and they use Cartesian AFM robots that severely limit the dexterity and performance of the imaging system. The aim of this thesis is to study and experiment an original concept of an AFM based on poly- articulated robotics for AFM-in-SEM correlative microscopy. A homemade 6 DoF (3 translations and 3 rotations) robotic AFM system is developed and integrated inside a SEM. The ability to control 3 positions and 3 rotations of a micrometer sized AFM probe while keeping the center of rotation at the close proximity of a micro-structure is very challenging. This is mainly due to the uncertainties inherent to the assembly of micro-robotic systems and clearances in the joints of the robot that are of the same order of magnitude as the required AFM probe positioning accuracy. Robot calibration methods and control theory can however overcome these limitations as demonstrated in the thesis. Control strategies and a user interface are studied to operate the multi DoF correlative imaging system in a versatile and intuitive way for low-level end users while keeping it enough powerful for high-level end users. Several key features that go beyond the state of the art are implemented, including - Vision based control for fast and automated landing of an AFM probe on a micrometer sized sample with robustness with respect to the SEM magnification. The user can select any region of interest (ROI) on a sample by simply performing a mouse click on the SEM screen. Whatever the SEM magnification, the control algorithm ensures a safe landing of the AFM probe on the ROI. The surface of the sample can be as high as several square centimeters and the positioning can be achieved with a micrometric precision. - In-plane and out-of-plane rotation of a sample relatively to the AFM probe while keeping the center of rotation around the tip of the AFM. The center of rotation is defined by the user with a mouse click on the SEM screen. This feature is useful for manipulation and topography tasks, as well as for multi-angle observations of a sample inside a SEM. - Trajectory/speed selection modes. Low speed AFM mode for a detailed topography imaging. Fast AFM mode (4fps) for dynamic observations at the nanoscale. The users also have access to the control parameters. They can be modified to suit their needs. - Mosaic AFM mode to extend the topography scanning area inside a SEM. All these features rely on research works in robotics, mechatronics and control made during the thesis. The latter has the potential to opens the door to a new era of poly-articulated atomic force microscopes used in correlative microscopy
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Leane, Robert B. "Scanning tunnelling microscopy." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291716.
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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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Tomic, Aleksandra T. "Scanning tunneling microscopy of complex electronic materials." Diss., Connect to online resource - MSU authorized users, 2008.
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Thesis (Ph.D.)--Michigan State University. Dept. of Physics and Astronomy, 2008.Title from PDF t.p. (viewed on Mar. 27, 2009) Includes bibliographical references (p. 95-102). Also issued in print.
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Shin, Heungjoo. "Fabrication of atomic force microscope probes integrated with microelectrodes for micro four-point probe and SECM-AFM." Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-01042006-123329/.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2006.Levent Degertekin, Committee Member ; William P. King, Committee Member ; Boris Mizaikoff, Committee Member ; Mark G. Allen, Committee Member ; Peter J. Hesketh, Committee Chair.
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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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Amaduci, Marcia Regina Lombardo. "Efeitos do campo eletromagnetico em celulas e bacterias." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259947.
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Orientador: Vitor BaranauskasDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Este trabalho refere-se a alguns efeitos de um campo eletromagnético aplicados em colônias bacterianas. A bactéria escolhida é bastante conhecida no mundo científico e tratase da Escherichia coli (E. coli). A parte experimental divide-se entre a análise quantitativa, qualitativa e morfológica sobre o ciclo de vida da E. coli. O circuito eletromagnético foi gerado a partir de uma freqüência de 60Hz. Durante um período de 18h, as bactérias acopladas ao circuito eletromagnético se proliferaram em meio aquoso e a cada fase do ciclo de vida da E. coli, foram realizadas diluições em tubos de ensaio para a análise da absorbância e contagem de bactérias viáveis. Ao mesmo tempo foram colocados em uma estufa, na mesma temperatura do circuito, tubos contendo a mesma amostra em quantidade e qualidade, para uma análise paralela do seu ciclo de vida. O trabalho inclui análise morfológica, com a utilização da microscopia eletrônica de transmissão (MET) e da microscopia eletrônica de varredura (MEV)
Abstract: This research work studies some effects of an electromagnetic field applied on bacteria. The chosen bacterium is quite known in the scientific world, the Escherichia coli (E. coli). The experimental part was divided into the quantitative, qualitative and morphologic analysis on the life of bacterium Escherichia coli. The electromagnetic circuit was generated from a frequency of 60Hz. During a period of 18h, the bacteria connected to the electromagnetic circuit proliferated in watery way, and for each phase of the life cycle of E. coli LT1, dilutions in test tube were performed for the analysis of the absorbancy and counting of viable bacteria. At the same time, other test tubes holding the same sample in amount and quality were placed in a incubator, at the same temperature of the circuit, for a parallel analysis of its cycle of life. The work includes morphologic analysis, with the use of transmission electronic microscopy (TEM), and scanning electronic microscopy (SEM)
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica
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Chang, Michael Ming Yuen. "A computer-controlled system in transmission electron microscopy." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292941.
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Girirajan, Thanu Prabha Kalambur. "Development of Spectral Imaging Microscope for Single Molecule Studies in Complex Biological Systems." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/GirirajanTPK2007.pdf.
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Haenssler, Olaf Christian. "Multimodal sensing and imaging technology by integrated scanning electron, force, and near-field microwave microscopy and its application to submicrometer studies." Thesis, Lille, 2018. http://www.theses.fr/2018LIL1I006.
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La combinaison de plusieurs procédés d’imagerie et de mesure permet d’obtenir des ensembles de données complémentaires et parfois uniques. A l’aide d’une technique hybride de microscopie présentant des modalités de mesure différentes et des enregistrements synchrones, on peut recueillir des informations complémentaires sur des échantillons à l’échelle nanométrique. De plus, l’intégration de procédés nanorobotiques et de logiciels open-source permet une approche technologique pour la recherche sur les semi-conducteurs et les sciences des matériaux. Ce travail démontre le potentiel d’une telle technologie. Ce démonstrateur fonctionne dans la chambre d‘un MEB et sert de plateforme technologique dans laquelle sont intégrés différentes modalités, technologies et procédés. Un AFM basé sur un interféromètre optique compact permet l’imagerie de la topographie de surface tandis qu’un microscope à micro-ondes à balayage enregistre les caractéristiques électromagnétiques dans la gamme de fréquence des micro-ondes, le tout opérant dans le même MEB. L’engin est contrôlé par un ensemble de logiciels qui est optimisé pour la nanorobotique basée sur l‘imagerie. Ce démonstrateur technologique permet d’observer en direct la région d’intérêt à l’aide du microscope électronique tandis qu’est effectuée en champ proche la caractérisation de la surface de l’échantillon par intermédiaire des micro-ondes évanescentes et des forces intermoléculaires. Ensuite, est présenté un standard multimodal de test et qui valide la fonctionnalité de l’instrument démonstrateur. Le présent travail est complété par une analyse électrique de capacités MOS ainsi que leur approximation destinée au calibrageVarious disciplines of micro- and nanotechnology requires combinatorial tools for the investigation, manipulation and transport of materials in the submicrometer range. The coupling of multiple sensing and imaging techniques allows for obtaining complementary and often unique datasets of samples under test. By means of an integrated microscopy technique with different modalities, it is possible to gain multiple information about nanoscale samples by recording at the same time. The expansion with nanorobotics and an open-source software framework, leads to a technology approach for semiconductor research and material science. This work shows the potential of such a multimodal technology approach by focusing on a demonstrator setup. It operates under high-vacuum conditions inside the chamber of a Scanning Electron Microscope and serves as a technology platform by fusing various microscopy modalities, techniques and processes. An Atomic Force Microscope based on a compact, optical interferometer performs imaging of surface topography, and a Scanning Microwave Microscope records electromagnetic properties in the microwave frequency domain, both operating inside an SEM. A software framework controls the instrument. The setup allows for observing with SEM, while imaging and characterizing with interacting evanescent microwaves and intermolecular forces simultaneously. In addition, a multimodal test standard is introduced and subsequently confirms the functionality of the demonstrator. Within this context, the work also includes an electrical analysis of micro-scale MOS capacitors, including an approximation for use in the calibration
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Johnson, Lars. "Nanoindentation in situ a Transmission Electron Microscope." Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8333.
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The technique of Nanoindentation in situ Transmission Electron Microscope has been implemented on a Philips CM20. Indentations have been performed on Si and Sapphire (α-Al2O3) cut from wafers; Cr/Sc multilayers and Ti3SiC2 thin films. Different sample geometries and preparation methods have been evaluated. Both conventional ion and Focused Ion Beam milling were used, with different ways of protecting the sample during milling. Observations were made of bending and fracture of samples, dislocation nucleation and dislocation movement. Basal slip was observed upon unloading in Sapphire. Dislocation movement constricted along the basal planes were observed in Ti3SiC2. Post indentation electron microscopy revealed kink formation in Ti3SiC2 and layer rotation and slip across layers in Cr/Sc multilayer stacks. Limitations of the technique are presented and discussed.
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Santos, Julio Sergio dos 1979. "A ultraestrutura dos espermatozoides de algumas espécies da família Leptodactylidae (Amphibia: Anura)." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/317961.
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Orientadores: Shirlei Maria Recco Pimentel , Gisele Orlandi IntroíniTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Os anuros da família Leptodactylidae estão alocados em três subfamílias: Leiuperinae, Leptodactylinae e Paratelmatobiinae. Com o auxílio da microscopia eletrônica, foram observados os espermatozoides de 23 espécies de leptodactilídeos buscando-se contribuir com elementos para o entendimento de incertezas filogenéticas. Em Pseudopaludicola, gênero alocado em Leiuperinae, é comparado o espermatozoide de representantes do grupo P. pusilla e de espécies dos quatro clados recuperados na filogenia molecular, os quais correspondem aos grupos cromossômicos 2n=22, 20, 18 e 16. A análise das espécies de Pseudopaludicola mostrou que as cabeças dos espermatozoides são semelhantes e contém a vesícula acrossomal cobrindo o cone subacrossomal. Já as caudas dos espermatozoides de Pseudopaludicola apresentam diferenças marcantes. Nas espécies com número cromossômico 2n=22, Pseudopaludicola sp. 1 (grupo P. pusilla), P. saltica, P. falcipes e P. mineira, as caudas exibem fibras acessórias (justa-axonemal, membrana ondulante e a fibra axial). Essas fibras também são observadas em P. ternetzi e P. ameghini, ambas do clado com 2n=20, mas nas suas caudas a fibra axial é mais desenvolvida. Nos indivíduos do clado com número cromossômico 2n=18, P. canga, P. facureae, P. giarettai, P. atragula e Pseudopaludicola sp. 2 e com 2n=16, P. mystacalis, a cauda apresenta a membrana ondulante espessa, caracterizando um bastão para-axonemal, o qual é mais curto do que a membrana ondulante da cauda dos Pseudopaludicola com número cromossômico 2n=22 e 20. As diferenças morfológicas ultraestruturais observadas nas caudas dos espermatozoides indicam que esses caracteres podem ser filogeneticamente informativos, quando mapeados na filogenia molecular, pois os perfis ultraestruturais da cauda coincidem parcialmente com a formação dos quatro clados filogenéticos e possibilitam levantar a hipótese de uma progressiva simplificação do espermatozoide durante a evolução do gênero Pseudopaludicola. A análise comparativa de espécies entre os gêneros de leiuperíneos mostra que as caudas dos espermatozoides de Physalaemus (P. albifrons, P. centralis, P. cicada e P. cuvieri), também exibem fibras acessórias, como a fibra justa-axonemal e a membrana ondulante, contudo, a membrana ondulante nesse gênero é mais longa que aquela encontrada em Pseudopaludicola. Além disso, as caudas dos espermatozoides de Physalaemus não mostram fibra axial. Do gênero Engystomops, grupo irmão de Physalaemus, foram analisadas E. petersi, E. freibergi e E. puyango, cujas caudas apresentam fibra justa-axonemal, membrana ondulante e fibra axial. Esses gêneros diferem ainda pela membrana ondulante mais curta em Engystomops, corroborando a revalidação do gênero Engystomops. A cauda de Engystomops puyango difere de E. petersi e E. freibergi, clado Duovox, e é igual a E. pustulosus, do clado Edentulus, indicando a necessidade de ampliar os estudos desse gênero. A espécie Pleurodema diplolister, do gênero próximo a Physalaemus e Engystomops, apresenta na cauda do espermatozoide a fibra justa-axonemal e a membrana ondulante, as quais são semelhantes àquelas observadas nas espécies de Physalaemus, entretanto, a membrana ondulante de P. diplolister é menor que a observada em Physalaemus. A comparação dos espermatozoides de representantes das outras subfamílias de Leptodactylidae mostrou que Paratelmatobiinae, representada por P. poecilogaster, apresenta estruturas iguais àquelas observadas nos Pseudopaludicola do clado com número cromossômico 2n=22. Por outro lado, a espécie analisada, Leptodactylus natalensis, Leptodactylinae, apresenta fibra axial bem desenvolvida, diferente daquela exibida nos espermatozoides de Engystomops, Pseudopaludicola e P. poecilogaster. A outra espécie de Leptoctylinae, Adenomera marmorata, a qual era alocada em Leptodactylus, apresenta apenas o axonema na cauda do espermatozoide. Essa diferença ultraestrutural das caudas de A. marmorata e L. natalensis, corrobora com a re-alocação de A. marmorata como espécie válida e diferente de Leptodactylus. A descrição ultraestrutural dos gametas masculinos leptodactilídeos mostra caracteres filogenéticos informativos, principalmente aqueles das caudas dessas células, que podem ser usados para o entendimento dos relacionamentos intragenérico e intergenérico.
Abstract: The anurans of the family Leptodactylidae are distributed in three subfamilies ¿Leiuperinae, Leptodactylinae and Paratelmatobiinae. The spermatozoa of 23 leptodactylid species were analyzed under an electron microscope in order to provide evidence for the better understanding of a number of phylogenetic uncertainties. In the case of the leiuperine genus Pseudopaludicola, the sperm of the representative of the P. pusilla group and those of four clades identified in the molecular phylogeny, which correspond to well-defined chromosomal groups with 2n=22, 20, 18, and 16, were compared. The analysis of the different Pseudopaludicola species found spermatozoa with heads of similar shape, which contain an acrosomal vesicle covering the subacrosomal cone. However, the tails present marked differences. In the species with 2n=22, that is, Pseudopaludicola sp. 1 (P. pusilla group), P. saltica, P. falcipes and P. mineira the tails present accessory fibers (juxtaxonemal fiber, undulating membrane and axial fiber). Fibers of this type are also observed in P. ternetzi and P. ameghini (representatives of the 2n=20 clade), although the axial fiber is more developed. In the specimens of the 2n = 18 clade (P. canga, P. facureae, P. giarettai, P. atragula and Pseudopaludicola sp. 2) and the 2n=16 clade (P. mystacalis), the tail has a thick undulating membrane, characterized by a paraxonemal rod, which is shorter than the undulating membrane of the tail of Pseudopaludicola (2n=22 and 20). The ultrastructural morphological differences observed in the tails of the spermatozoa indicates that these traits are phylogenetically informative, given their partial correspondence to the four clades identified in the molecular studies, and provide evidence of a progressive simplification of the spermatozoa during the evolution of the genus Pseudopaludicola. The comparative analysis of the leiuperine genera indicates that in Physalaemus (P. albifrons, P. centralis, P. cicada and P. cuvieri), the tail of the spermatozoon also shows accessory fibers, such as the juxtaxonemal and the undulating membrane, although in this genus, the membrane is longer than that observed in Pseudopaludicola. In addition, there is no axial fiber on the tail of the spermatozoon in Physalaemus. In the case of Engystomops, sister group of Physalaemus, the species E. petersi, E. freibergi, and E. puyango the sperm tail presents all three types of fiber (juxtaxonemal, undulating membrane and axial fiber). The tail of these two genera also differ each other for the shorter undulating membrane in Engystomops, corroborating the revalidation of the genus Engystomops. Additionaly, the tail of E.puyango differs from E. petersi and E. freibergi, Duovox clade, and it is similar to E. pustulosus, Edentulus clade, indicating the need of more studies in this genus. In Pleurodema diplolister, representing the genus closest to Physalaemus and Engystomops, the sperm tail has a juxtaxonemal fiber and undulating membrane, which are similar to those found in Physalaemus, although the membrane observed in Pleurodema diplolister is shorter than that observed in Physalaemus. Comparisons with other leptodactylid subfamilies indicated that the Paratelmatobiinae, represented by P. poecilogaster, has the same structures as those observed in the 2n = 22 clade of Pseudopaludicola. On the other hand, the leptodactyline species analyzed, Leptodactylus natalensis, has a well-developed axial fiber, distinct from that found in the sperm of Engystomops, Pseudopaludicola and P. poecilogaster. However, in the other leptodactyline species analyzed, Adenomera marmorata, previously allocated to Leptodactylus, the sperm tail has only an axoneme. This ultrastructural difference in the tails of A. marmorata and L. natalensis supports the status of A. marmorata as a valid taxon distinct from Leptodactylus. Overall, then, the ultrastructural description of the male gametes of a selection of leptodactylid species provided informative phylogenetic characters, especially with regard to the morphology of the sperm tails, which can be used for understanding of the intrageneric and intergeneric relationships
Doutorado
Biologia Celular
Doutor em Biologia Celular e Estrutural
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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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Claveau, Yann. "Modeling of ballistic electron emission microscopy." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S074/document.
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Après la découverte de la magnéto-résistance géante (GMR) par Albert Fert et Peter Grünberg, l'électronique a connu une véritable avancée avec la naissance d'une nouvelle branche appelée spintronique. Cette discipline, encore jeune, consiste à exploiter le spin des électrons dans le but notamment de stocker de l'information numérique. La plupart des dispositifs exploitant cette propriété quantique des électrons consistent en une alternance de fines couches magnétiques et non magnétiques sur un substrat semi-conducteur. L'un des outils de choix pour la caractérisation de ces structures, inventé en 1988 par Kaiser et Bell, est le microscope à émission d'électrons balistiques (BEEM). A l'origine, ce microscope, dérivé du microscope à effet tunnel (STM), était dédié à l'imagerie d'objets (nanométriques) enterrés ainsi qu'à l'étude de la barrière de potentiel (barrière Schottky) qui se forme à l'interface d'un métal et d'un semi-conducteur lors de leur mise en contact. Avec l'essor de la spintronique, le BEEM est devenu une technique de spectroscopie essentielle mais encore fondamentalement incomprise. C'est en 1996 que le premier modèle réaliste, basé sur le formalisme hors équilibre de Keldysh, a été proposé pour décrire le transport des électrons dans cette microscopie. Il permettait notamment d'expliquer certains résultats expérimentaux jusqu'alors incompris. Cependant, malgré son succès, son usage a été limité à l'étude de structures semi-infinies via un méthode de calcul appelée décimation de fonctions de Green. Dans ce contexte, nous avons étendu ce modèle au cas des films minces et des hétéro-structures du type vanne de spin : partant du même postulat que les électrons suivent la structure de bandes du matériaux dans lesquels ils se propagent, nous avons établi une formule itérative permettant le calcul des fonctions de Green du système fini par la méthode des liaisons fortes. Ce calcul des fonctions de Green a été encodé dans un programme Fortran 90, BEEM v3, afin de calculer le courant BEEM ainsi que la densité d'états de surface. En parallèle, nous avons développé une autre méthode, plus simple, qui permet de s'affranchir du formalisme hors équilibre de Keldysh. En dépit de sa naïveté, nous avons montré que cette approche permettait l'interprétation et la prédiction de certains résultats expérimentaux de manière intuitive. Cependant, pour une étude plus fine, le recours à l'approche “hors équilibre” reste inévitable, notamment pour la mise en évidence d'effets d'épaisseur, lés aux interfaces inter-plans. Nous espérons que ces deux outils puissent se révéler utiles aux expérimentateurs, et notamment pour l'équipe Surfaces et Interfaces de notre départementAfter the discovery of Giant Magneto-Resistance (GMR) by Albert Fert and Peter Grünberg, electronics had a breakthrough with the birth of a new branch called spintronics. This discipline, while still young, exploit the spin of electrons, for instance to store digital information. Most quantum devices exploiting this property of electrons consist of alternating magnetic and nonmagnetic thin layers on a semiconductor substrate. One of the best tools used for characterizing these structures, invented in 1988 by Kaiser and Bell, is the so-called Ballistic Electron Emission Microscope (BEEM). Originally, this microscope, derived from the scanning tunneling microscope (STM), was dedicated to the imaging of buried (nanometer-scale) objects and to the study of the potential barrier (Schottky barrier) formed at the interface of a metal and a semiconductor when placed in contact. With the development of spintronics, the BEEM became an essential spectroscopy technique but still fundamentally misunderstood. It was in 1996 that the first realistic model, based on the non-equilibrium Keldysh formalism, was proposed to describe the transport of electrons during BEEM experiments. In particular, this model allowed to explain some experimental results previously misunderstood. However, despite its success, its use was limited to the study of semi-infinite structures through a calculation method called decimation of Green functions. In this context, we have extended this model to the case of thin films and hetero-structures like spin valves: starting from the same postulate that electrons follow the band structure of materials in which they propagate, we have established an iterative formula allowing calculation of the Green functions of the finite system by tight-binding method. This calculation of Green’s functions has been encoded in a FORTRAN 90 program, BEEM v3, in order to calculate the BEEM current and the surface density of states. In parallel, we have developed a simpler method which allows to avoid passing through the non-equilibrium Keldysh formalism. Despite its simplicity, we have shown that this intuitive approach gives some physical interpretation qualitatively similar to the non-equilibrium approach. However, for a more detailed study, the use of “non-equilibrium approach” is inevitable, especially for the detection of thickness effects linked to layer interfaces. We hope these both tools should be useful to experimentalists, especially for the Surfaces and Interfaces team of our department
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Chand, Gopal. "Aberration determination and compensation in high resolution transmission electron microscopy." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362968.
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Gold, Daniel Patrick. "Transmission electron microscope studies of emitters of silicon bipolar transistors." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:ec5f58c3-ced6-44fe-8f1f-d042cdb7b7b7.
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Transmission Electron Microscope (TEM) studies have been carried out of emitter regions in polysilicon contacted emitter bipolar transistors. The preparation of suitable TEM thin foils is described. In addition a technique is developed for the observation and quant jtative interpretation of the break-up of the interfacial oxide layers observed in these samples. The effect of annealing the samples prior to emitter dopant implantation (pre-annealing) is investigated for phosphorus and arsenic doped samples, implanted into a polysilicon layer 0.4μm thick, with a dose of 1x1016cm2. Two wafer pre-cleans have been used prior to polysilicon deposition to produce a thin oxide (0-8Å) and a thicker oxide (14Å). In the presence of the thinner oxide, the phosphorus doped samples enhance epitaxial regrowth of the polysilicon layer compared with the arsenic doped or undoped samples. In the presence of the thicker oxide, no difference is observed between the samples. A mechanism is proposed to explain this. The mechanisms controlling the gain of a phosphorus doped device are investigated and a model proposed to explain the observed electrical characteristics. It is concluded that there are two mechanisms responsible for the observed supression of hole current. Firstly tunnelling through the interfacial oxide and secondly some blocking effect of the interface. Carrier transport in the polysilicon is not believed to contribute to this supression. A dopant sensitive etch has been applied to TEM thin foils containing fully processed emitters in state-of-the-art devices. The shape of the emitter dopant distribution is revealed in such devices for the first time, and a 2-D profile is obtained from the emitter. It is shown that reduction in the emitter depth to 8OOÅ or less does not alter the emitter dopant geometry. The technique is demonstrated to be capable of resolving spatial separations of dopant iso-concentration contours of 100Å or less.
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Mattiazzo, Serena. "Performances of the Ion Electron Emission Microscope at SIRAD." Doctoral thesis, Università degli studi di Padova, 2008. http://hdl.handle.net/11577/3425031.
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When an energetic ion strikes a microelectronic device it induces current transients that may lead to a variety of undesirable Single Event Effects (SEE). An important part of the activity of the SIRAD heavy ion facility at the 15 MV Tandem accelerator of the INFN Laboratories of Legnaro (Italy) concerns SEE studies of microelectronic devices destined for radiation hostile environments.
An Ion Electron Emission Microscope (IEEM) is working at the SIRAD facility. In the IEEM technique, a broad ion beam irradiates a device under test (DUT) and the secondary electrons emitted by the target surface by each ion impact are collected and focused by a commercial electron emission microscope onto a fast electron detector. The spatial (x and y coordinates) and the temporal information of the ion impacts are then correlated to the SEE induced in the device under test and a SEE sensitivity map is obtained. An IEEM can achieve resolutions better than 1um, comparable to the ones achieved by nuclear microprobes techniques where the DUT is systematically scanned with micrometric precision with a microfocused beam. For a heavy ion microbeam to work one must meet severe requirements in terms of beam monochromaticity and stability. The IEEM poses no such requests.
In this thesis we describe in detail the IEEM apparatus working at SIRAD facility and the performed experiments, with an initial discussion on the physical aspects involved in radiation hardness testing.
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Shin, Heungjoo. "Fabrication of Atomic Force Microscope Probes Integrated with Microelectrodes for Micro Four-Point Porbe and SECM-AFM." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10428.
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This research is dedicated to develop novel batch fabrication procedures for two distinct AFM (Atomic Force Microscope) probes integrated with electrodes enabling electrical sample characterization and electrochemical sample surface profiling respectively. These AFM probes allow for highly accurate control of the probe positioning, low contact force and sample surface imaging with high lateral resolution.
As an electrical characterization tool, a nickel micro four-point probe integrated with solid nickel tips was developed. Low electrical resistance of the probe and contact resistance were achieved due to the solid nickel cantilever and tips. Low aspect ratio solid metal tips reduced contact resistance resulting in stable electrical measurement. Conductivity loss easily experienced while using metal coated AFM cantilevers was overcome by solid nickel tip integration to the electrically conductive AFM cantilevers. The fabrication method introduces selective conical nickel tip etching in silicon dioxide etching chambers.
A novel batch fabrication method for SECM-AFM (Scanning Electrochemical Microscope-Atomic Force Microscope) tip integrated with a ring electrode was developed as a tool for electrochemical imaging as well as topological imaging. The electroactive area at an exactly defined distance above the apex of the AFM tip is fabricated using an inverse silicon mold technique. The electrode at a deliberately chosen distance from the end of a scanning probe tip allowing electrochemical sample imaging separated from sample topology imaging. The ring electrode coated with polymer entrapping enzymes enabled the probe to detect ATP from living epithelial cells.
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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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Burger, Willem Adriaan. "The design and analysis of a DC SQUID for a SQUID microscope." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/2239.
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Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2008.This thesis relates to the analysis and design of a SQUID microscope. Superconductor theory is discussed in depth to provide a thorough understanding of Josephson junctions and of dc SQUID magnetometers. The behaviour and suitability of different types of single-layer dc SQUIDs are looked at. The quality of the superconducting material patterned onto a substrate and the Josephson junction design used affect the behaviour of a practical dc SQUID. Noise and cooling play an integral part in the design and operation of a dc SQUID. The source of noise is looked at in an effort to minimize its effect. Cryocooling is essential to real world operation so different cooling strategies and their consequences are analyzed. This thesis focuses on modeling the behaviour of the dc SQUID to creating a practical system for use inside a SQUID microscope. Operating the dc SQUID with the appropriate electronics will linearize the device, reduce the effect of noise, and create a device with wide bandwidth. Each step in creating a practical system is discussed in detail. Simulations are used to create models predicting the behaviour of the dc SQUID and the electronics. They are then used to design and create practical electronic systems. Measurements are performed on Josephson junctions and dc SQUID magnetometers using the designed electronics. The Josephson junctions behave as predicted and were successfully tested. The dc SQUIDs did not behave as predicted and were not successfully tested. The SQUIDs were damaged, either by a malfunction in the cryocooler or through age related deterioration. A full test of the flux-locked loop was not possible and the dc SQUID was not linearized.
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Ingle, Jeffery Thomas 1962. "Applications of scanning force microscopy to magnetic and electronic media." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277145.
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A scanning force microscope is an instrument which can image the forces present on a sample with high resolution. These forces include magnetic, electric, and atomic forces. The scanning force microscope uses either a tunneling, capacitive or optical method of sensing the motion of a lever-tip mechanical system that reacts to the forces present on a sample. There are four optical methods used in scanning force microscopy: heterodyne, homodyne, deflection and laser feedback. In this thesis, two implementations of the laser feedback method of detecting lever motion are described: a fiber coupled laser diode feedback and a tightly coupled laser diode feedback. The theory of interactions between a tip and the magnetic or electric fields at the surface of a sample are presented, along with the theory of the laser diode feedback. The limiting noises inherent in the system are discussed and representative values are given. Results of the sensitivity of the two systems are presented, and images of electric forces acting on the tip from interdigitated electrodes are demonstrated.
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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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Atia-Tul-Noor. "Reaction microscope studies of small molecules in strong laser fields." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/371910.
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The dynamics of molecules and molecular reactions that generate chemistry such as
bond breaking, bond formation or bond rearrangement occur on the femtosecond
(1015 s) time scale. Real-time observations and investigations of these reactions are
fundamental to understanding these dynamics. Ultra-fast laser pulses with intensities
around 1014 W=cm2, impact on the electronic and nuclear motion on femtosecond
timescale. In order to understand the region of transition states between the initial
and nal state of a reaction, that determines the fate of the products, detailed
experimental investigations are necessary.
This work focuses on three separate investigations, one addressing the strong eld
control of the electronic dynamics in the hydrogen molecule and two addressing the
strong eld ionization dynamics in small but complex hydrocarbon molecule acetylene
(C2H2). The pump-probe approach is applied to observe the real-time femtochemistry.
The rst part of this thesis deals with the strong eld dissociation of H+
2 . The goal
is to control the dissociating dynamics by utilizing the control capability of the carrierenvelope
phase (CEP) in a pump-probe approach. The work shows the response of
the bound electron during the dissociation process. The timing of the electron localization
and time-dependent distribution of the inter-nuclear separation is retrieved.
Second and third part of this thesis deals with the investigations of the fragmentation
dynamics in acetylene in the strong laser eld. Time-resolved vibrational
dynamics and enhanced ionization (EI) are studied by using the pump-probe approach
with reaction microscope in the second part. A wave-packet is launched onto
the acetylene cation by the pump pulse and vibrational dynamics are traced by the
probe pulse in di-cation fragmentation of the acetylene. Whereas laser parameters
to control particular fragmentation and bond breaking are investigated in the third section of the thesis. This is illustrated by taking the experimental measurements at
di erent laser intensities and ellipticities and parameters that govern the ultra-fast
proton migration in acetylene dication are investigated. It is found that C-C bond
breaking after proton migration in acetylene dication is favored in circularly polarized
laser elds over C-C bond breaking without proton migration.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
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Leigh, David. "The electronic structure of carbon nanomaterials imaged by scanning tunneling microscopy." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427631.
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Jerner, Karin. "Electrical Pulsing of a Laser Diode for Usage in Fluorescence Microscopy." Thesis, Linköpings universitet, Elektroniska Kretsar och System, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-136723.
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A relatively new application for the laser is in fluorescence microscopes. The fluo- rescence microscope needs a high power light source input. Using a laser source improves the precision of the microscope. A pulsed laser source enhances the performance of the fluorescence microscope and a laser diode can be overdriven without being damaged. The thesis investigates which properties of the laser pulses are needed regarding pulse width, pulse period and waveform. The thesis also investigates which properties are desired for the electrical pulses driving the laser, and how they can be generated using electrical components. The desired laser pulse should have a pulse width of 100 ps and a pulse period of 50 ns. The laser pulse should also have a well-defined wavelength, stable output power and it should be able to quickly turn on and off. To achieve this laser pulse, the desired input to the laser diode should have an input voltage of 5 V, an input current of 250 mA, a pulse width of 100 ps and a pulse period of 50 ns. For generating this pulse the chosen pulse generator, an SRD, should have low junction capacitance, low package capacitance and low package inductance. The chosen amplifier, a MESFET, desires low drain current and should have high transconductance and a large negative threshold voltage.
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Lawunmi, David Laditi. "Theoretical studies of scanning tunnelling microscopy and tunnelling phenomena." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386087.
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Goroš, Pavel. "Kontrast v obraze získaném pomocí ionizačního detektoru ve VP SEM." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219043.
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This work deal with problems of investigation materials electron beam. This project is focuses on investigation materials by the help of method environmental scan electron microscopy (ESEM) and describes her patterns. The perfection of ESEM excel above all at studies non - conducting or water containing, often biological samples. These samples not to be in no way prepared or cut – and – dries, in contradistinction to classical scanning electron microscope and thanks is under investigation their native surface structure without desiccation breaking. The general aim is determination of contrast in image acquired by ionization detector.
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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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Park, Kibog. "Electronic properties of stacking-fault induced heterostructures in silicon carbide studied with ballistic electron emission microscopy." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149089614.
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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.
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Åhlund, John. "Electronic and geometrical structure of phthalocyanines on surfaces : an electron spectroscopy and scanning tunneling microscopy study /." Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7802.
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Rawcliffe, Adam. "The reactions of loaded carbon nanotubes studied by novel electron microscope techniques." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301258.
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Durako, Maris R. "A reassessment of Geminella (Chlorophyta) based upon photosynthetic pigments, DNA sequence analysis and electron microscopy /." Electronic version (PDF), 2007. http://dl.uncw.edu/etd/2007-1/durakom/marisdurako.pdf.
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Meyer, Jörg. "Electronic Properties of Organic Nanomaterials Studied by Scanning Tunneling Microscopy and Spectroscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200781.
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In this work organic molecules, namely derivatives of BODIPY and poly-para-phenyls are investigated on different metal surfaces by means of LT-STM. These molecule are important for the development of molecular electronics and spintronics. I show that aza-BODIPY molecules form a weak chemical bond with the Au(111) substrate and the molecular structure significantly changes upon adsorption. Due to the low corrugation of the Au(111) surface, diffusion of the molecule is observed for applied bias in excess of ±1 V. The temperature dependent formation of different molecular nanostructures formed by polyparaphenyls and Au adatoms is discussed. The diffusing Au adatoms act as coordination centers for the cyano groups present on one end of the molecules. The structure of the super molecular assemblies completely changes in a temperature range of only 60 K. Furthermore, I investigate in this work the hybridization of atomic orbitals within the molecular ligand. The Kondo resonance of a Co atom incorporated into an other aza-BODIPY derivative is investigated in detail on Ag(100). The hybridization of the atomic Co orbital with the organic ligands molecular orbitals is shown by spectroscopy measurements with submolecular resolution. The changing line shape of the Kondo resonance for the molecule-substrate system is discussed. This data is compared to measurements of Co incorporated in another molecular binding motive and on different metal samples to show the importance of the local environment for molecular materialsIn dieser Arbeit werden organische Moleküle, Derivate von BODIPY und poly-para-Phenyl, auf verschiedenen Metalloberflächen mittels Tief-Temperatur Rastertunnelmikroskopie (LT-STM) untersucht. Diese Moleküle sind wichtig für die Entwicklung von molekularer Elektronik und Spintronik. Ich zeige, dass aza-BODIPY-Moleküle eine schwache chemische Bindung mit dem Au(111)- Substrat eingehen und die molekulare Struktur bei der Adsorption deutlich verändert wird. Wegen der geringen Rauigkeit der Au(111)-Oberfläche wird bereits bei einer angelegten Spannungen über ±1 V die Diffusion der Moleküle beobachtet. Die temperaturabhängige Bildung verschiedener molekularer Nanostrukturen aus poly-para-Phenyl und frei beweglichen Goldatomen wird diskutiert. Die diffundierenden Goldatome agieren hierbei als Koordinationszentren für die Cyanogruppen am einen Ende der Moleküle. Die Struktur der supramolekularen Anordnungen verändert sich dabei in einem Temperaturbereich von nur 60 K vollkommen. Außerdem beschäftige ich mich in dieser Arbeit mit der Hybridisierung atomare Orbitale im molekularen Verbund. Die Kondo-Resonanz eine Co-Atoms, welches in einem anderen aza-BODIPY-Derivat gebunden ist, wird detailliert auf der Ag(100)-Oberfläche untersucht. Die Hybridisierung des atomaren Co-Orbitals mit den molekularen Orbitalen des organischen Liganden wird an Hand von Spektroskopiemessungen mit submolekularer Auflösung gezeigt. Die veränderte Form der Kondo-Resonanz für dieses Molekül-Substrat-System wird diskutiert. Diese Daten werden mit Messungen an Co-Atomen in anderen molekularen Bindungsschemen und auf anderen Substraten verglichen um dieWichtigkeit der lokalen Umgebung für molekulare Materialien zu verdeutlichen
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Bidermane, Ieva. "Structure and Electronic Properties of Phthalocyanine Films on Metal and Semiconductor Substrates." Doctoral thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-217086.
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The current thesis presents fundamental studies of phthalocyanines (Pcs), a group of organic macro-cycle molecules. The use of phthalocyanine molecular films in devices with a variety of possible technological applications has been the reason of the many studies dedicated to such molecules during the last decades. Core and valence photoelectron spectroscopies (PES), X-ray absorption spectroscopy (XAS) and scanning tunneling microscopy (STM) techniques are used to study phthalocyanine molecules in gas phase and adsorbed on gold (111) and silicon Si(100)-2x1 substrates. Density functional theory (DFT) is used to obtain further insights in the electronic structure of the phthalocyanines. The aim of our studies is to get a deeper understanding into the molecule-molecule and molecule-substrate interactions, a fundamental requirement for improving the devices based on such molecular materials. Gas phase PES and XAS studies and single molecule DFT calculations are performed on the valence band (VB) of iron phthalocyanine (FePc), manganese phthalocyanine (MnPc) and metal-free phthalocyanine (H2Pc). The VB simulations have shown how the metal atom of the Pc influences the inner valence states of the molecules. The HOMO of the H2Pc and FePc is formed by mostly C2p states, whereas the HOMO of MnPc has mainly Mn3d character. PES studies of H2Pc on Au(111) have revealed the influence of the surface on the adsorption of the monolayer. XAS studies indicate formation of ordered monolayer with the Pc ligands parallel to the surface and the change of the molecular tilt angle with increasing thicknesses. For LuPc2 adsorbed on Au(111), STM study demonstrates a formation of bilayer instead of a monolayer. A comparison between the results of LuPc2 adsorbed on pristine or passivated Si(100)-2x1 confirmes the different reactivities of these surfaces: LuPc2 retains many molecular-like characters, when adsorbed on the innert passivated Si. Instead, on the more reactive pristine Si surface, the spectroscopic results have indicated a more significant interaction, possible hybridization and charge redistribution between the molecules and the surface. Moreover, STM images show a modification of the geometrical shape of the molecules, which are proposed to adsorb in two different geometries on the pristine Si surface.
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Matos, Jorge José Rio Tinto de. "Tratamento com glutamina ou associação de hidrocortisona, dimetilsulfóxido, ácido ascórbico e pentoxifilina de lesões decorrentes de isquemia e reperfusão induzidas no cólon maior de equinos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/10/10137/tde-10102012-111339/.
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Com o objetivo de estudar os possíveis efeitos da administração sistêmica de glutamina ou da associação de hidrocortisona, dimetilsulfóxido, ácido ascórbico e pentoxifilina nas lesões de isquemia e reperfusão no cólon maior, foram utilizados dezoito equinos. Sob anestesia geral e controle da oximetria de pulso e pressão arterial, os equinos foram submetidos a laparotomia e em um segmento do cólon maior foi induzida isquemia venosa total. Após uma hora de isquemia, seis equinos do Grupo G receberam glutamina (25mg/Kg IV), seis equinos do Grupo A receberam uma associação de hidrocortisona (4mg/Kg IV), dimetilsulfóxido (20mg/Kg IV), ácido ascórbico (50mg/Kg IV), e pentoxifilina (10mg/Kg IV) e os seis equinos do Grupo C receberam apenas solução de Ringer com lactato e constituíram o Grupo controle. Após duas horas de isquemia o fluxo sanguíneo local foi restabelecido. Decorridas duas horas de reperfusão foi realizada a laparorrafia e permitiu-se a recuperação anestésica. Seis horas após o início da reperfusão os equinos do Grupo G receberam novamente 25mg/Kg de glutamina, enquanto os equinos dos Grupos A e C receberam apenas solução de Ringer com lactato. Doze horas após o início da reperfusão os equinos foram eutanasiados. Foram colhidas amostras de cólon antes da indução da isquemia, após duas horas de isquemia e após duas e doze horas de reperfusão, que foram submetidas a avaliação histomorfológica, ultra-estrutural e determinação da atividade de mieloperoxidase. Os resultados para todas as variáveis estudadas foram semelhantes entre os grupos, permitindo concluir que os tratamentos, nas condições em que foram empregados neste estudo, não foram eficazes em atenuar as alterações decorrentes de isquemia e reperfusão no cólon maior de equinos.This study was designed to evaluate the effects of intravenous administration of glutamine or the association of hydrocortisone, dimethyl sulphoxide, ascorbic acid and pentoxifylline on ischemia reperfusion lesions of the large colon. A segment of the large colon was isolated in 18 horses under inhalant general anesthesia and total venous ischemia was induced. One hour after the onset of ischemia, glutamine (25mg/Kg IV) was administered to six horses (G group), an association of hydrocortisone (4mg/Kg IV), dimethyl sulphoxide (20mg/Kg IV), ascorbic acid (50mg/Kg IV) and pentoxifylline (10mg/Kg IV) was administered to six horses, and the others received only isotonic fluids and remained as the control group (C). After 2 hours of ischemia and 2 hours of reperfusion the abdomen was closed and the horses were allowed to recover from anesthesia. After 6 hours of reperfusion, horses of group G received another dose of glutamine (25mg/Kg IV) whereas groups A and C received only isotonic fluids. Horses were euthanatized 12 hours after reperfusion. Biopsies were taken from the large colon before and after 2 hours of ischemia and after 2 and 12 hours of reperfusion. Alterations were evaluated under light and scanning electronic microscopy and scored. Additionally, mieloperoxidase (MPO) activity was measured. Results showed that scores for mucosal lesion, edema, hemorrhage, neutrophil infiltration and MPO activity during IR were similar between groups G, A and C. It was concluded that treatments were not effective in attenuating effects of ischemia and reperfusion in the equine large colon.
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Caruso, Giuseppe Mario. "Development of a coherent ultrafast transmission electron microscope based on a laser-driven cold field emission source." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30140.
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L'étude de la physique des systèmes à l'échelle nanométrique nécessite idéalement une résolution spatiale atomique et une résolution temporelle de l'ordre de la femtoseconde. La microscopie électronique en transmission ultra-rapide (UTEM), qui combine une résolution temporelle inférieure à la picoseconde et une résolution spatiale nanométrique, est récemment apparue comme un outil unique doté de résolutions spatio-temporelles sans précédent. Cependant, les performances des premiers UTEMs étaient limitées par la brillance des photocathodes utilisées comme source d'électrons ultra-rapide. Dans ce contexte, il a été vite réalisé que les UTEMs utilisant des sources d'électrons déclenchées par laser et basées sur des pointes métalliques comme émetteur, permettraient de dépasser cette limitation. L'objectif de cette thèse est de décrire le développement d'un microscope électronique en transmission ultra-rapide basé sur ce type de source dites " source à émission de champ froide ", pouvant fonctionner en mode continu ou ultra-rapide. L'émission d'électrons d'une nanopointe de tungstène est déclenchée par des impulsions laser femtosecondes, qui sont fortement focalisées par des composants optiques insérés proche de la cathode. La brillance mesurée est la plus grande mesurée à ce jour dans un UTEM. En associant cette nouvelle source de brillance élevée à un système d'injection/cathodoluminescence composé d'un miroir parabolique installé au-dessus du porte-échantillon, l'UTEM peut être utilisé pour réaliser des expériences TEM-pompe-sonde ultra-rapides résolues dans le temps. Les possibilités d'un tel instrument pour l'imagerie ultra-rapide, la diffraction, l'holographie électronique et la spectroscopie sont présentées. Une attention particulière a été accordée aux applications en nano-optique. La spectroscopie électronique de gain d'énergie (EEGS) permet notamment d'étudier les excitations optiques de nano-systèmes à travers les modifications du spectre d'énergie des électrons. La possibilité de synchroniser facilement les impulsions d'électrons libres ultra-courts avec l'excitation optique de l'échantillon dans les UTEM est essentielle pour l'observation d'interactions électron/photon fortement non linéaires. Ces expériences nous ont permis de caractériser les propriétés spectro-temporelles du faisceau d'électrons ultra-courts. La dernière partie propose une discussion des premières expériences d'holographie électronique hors-axe réalisées avec des impulsions électroniques ultra-rapides. En effet, la dose d'électrons dans le plan de l'échantillon étant considérablement réduite en raison du faible taux de répétition du train d'impulsions électronique, les hologrammes ultra-rapides sont obtenus dans des conditions dites " low dose " complexes. En conséquence, les paramètres expérimentaux couramment utilisés pour l'acquisition d'hologrammes avec des TEM conventionnels ne peuvent pas être directement utilisés en mode ultra-rapide. Des études expérimentales ont été réalisées pour déterminer les conditions optimales pour l'holographie électronique hors-axe ultra-rapide. L'influence de la dose, la longueur de cohérence de la source, les conditions d'illumination et les instabilités de l'instrument ont été systématiquement prises en compteThe investigation of the physics of nanoscale systems ideally requires atomic spatial resolution and femtosecond time-resolution. Ultrafast Transmission Electron Microscopy (UTEM) combining subpicosecond temporal resolution and nanometer spatial resolution has recently emerged as a unique tool with unprecedented spatio-temporal resolutions. However, the performances of the first UTEMs were limited by the brightness of the photocathodes used as ultrafast electron source. In this context, it was soon realized that UTEMs relying on laser-driven electron sources based on nanoscale emitters would overcome this limitation. The aim of this thesis is to report the development of an ultrafast Transmission Electron Microscope based on a cold field emission source, which can operate either in DC or ultrafast mode. Electron emission from a tungsten nanotip is triggered by femtosecond laser pulses, which are tightly focused by optical components integrated inside a cold-field emission source close to the cathode. The measured brightness is the largest reported so far for UTEMs. Combining this new high brightness source with an injection/Cathodoluminescence system, composed of a parabolic mirror placed above the sample holder, the UTEM can be used to perform time-resolved ultrafast pump-probe TEM experiments. The possibilities of such an instrument for ultrafast imaging, diffraction, electron holography and spectroscopy are presented. Particular attention has been paid on applications in nano-optics. In particular, Electron Energy Gain Spectroscopy (EEGS) allows to investigate the optical excitations of nanosystems in the energy domain. The ability to easily synchronize ultrashort free electron pulses with the optical excitation of the sample in UTEMs is essential for the observation of strongly nonlinear electron/photon interactions. These experiments will enable us to characterize the spectro-temporal properties of the ultrashort electron beam. Off-axis electron holography performed with ultrafast electron pulses are finally discussed. The electron dose in the specimen plane is considerably reduced due to the low repetition rate of the electron pulse train. This peculiar property of ultrafast FE-TEMs implies that ultrafast holograms are acquired in low-dose-like conditions. As a consequence, the experimental parameters commonly used for the acquisition of off-axis electron holograms with conventional TEMs cannot be directly implemented in the ultrafast mode. Experimental studies were performed to find the optimum conditions for ultrafast off-axis electron holography. Influence of the dose, the coherence length of the source, the illumination condition and the instrument instabilities have been addressed
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Wang, Lin. "Carrier profiling of ZnO nanowire structures by scanning capacitance microscopy and scanning spreading resistance microscopy." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI031/document.
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Ce travail de thèse porte sur l'application des techniques Scanning Capacitance Microscopy (SCM) et Scanning Spreading Resistance Microscopy (SSRM) pour la caractérisation électrique de nanofils de ZnO avec l'objectif d'en déterminer le dopage par profilage des porteurs libres suite à des essais de dopage de type p. Afin de pouvoir utiliser un référentiel planaire nécessaire à ces mesures par sonde locale, un procédé de remplissage par dip-coating et de polissage a été spécialement développé sur des champs de nanofils quasi-verticaux. De plus, dans le but de parvenir à un étalonnage des mesures SCM et SSRM, nous avons conçu et fait fabriquer des échantillons étalons de dopage de type n, contenant des niveaux de Ga en escalier de densité variable de 2×10^17 à 3×10^20 cm^-3. Les mesures sur des coupes transversales de ces deux de structures multicouches ont permis, pour la première fois sur ZnO d'établir un étalonnage des mesures SCM et SSRM et de déterminer le dopage intrinsèque électriquement actif de couches 2D nanométriques, résultat difficilement atteignable par d'autres techniques d'analyse. Des résultats inattendus de concentration résiduelle de porteur de l'ordre de 2×10^18 et 3×10^18 cm^-3 ont été trouvés sur les nanofils de ZnO crus par MOCVD et par CBD respectivement. Outre la caractérisation électrique microscopique des nanofils par SCM et SSRM, des techniques macroscopiques classiques ont été utilisées pour caractériser des assemblées importantes de nanofils de ZnO. L'origine de la difference entre les résultats de deux genres de technique a été discutée. Nous avons aussi étudié les effets des dopages ex-situ par diffusion du phosphore (procédé SOD) et des dopages in situ par incorporation d'antimoine (Sb) pendant la croissance MOCVD. Les résultats majeurs sont obtenus pour l'antimoine, en utilisant des couches ZnO: Sb 2D et des nanofils cœur-coquille ZnO/ZnO: Sb, ou l'hypothèse d'une compensation partielle du dopage n résiduel par un centre accepteur créé par le dopage Sb semble pouvoir être établie raisonnablementBased on atomic force microscope (AFM), scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) have demonstrated high efficiency for two dimensional (2D) electrical characterizations of Si semiconductors at nanoscale and then have been extensively employed in Si-based structures/devices before being extended to the study of some other semiconductor materials. However, ZnO, a representative of the third generation semiconductor material, being considered a promising candidate for future devices in many areas, especially in opto-electronic area, has rarely been addressed. Recently, extensive research interests have been attracted by ZnO NWs for future devices such as LED, UV laser and sensor. Therefore, a good understanding of electrical properties of the NWs is in need. In this context, this thesis work is dedicated to the 2D electrical characterization of ZnO NWs with the focus of carrier profiling on this kind of nanostructure in the effort of their p-type doping. For this purpose, a planarization process has been developed for the NWs structure in order to obtain an appropriate sample surface and perform SCM/SSRM measurements on the top of the NWs. For quantitative analysis, Ga doped ZnO multilayer staircase structures were developed serving as calibration samples. Finally, residual carrier concentrations inside the CBD and MOCVD grown ZnO NWs are determined to be around 3×10^18 cm^-3 and 2×10^18 cm^-3, respectively. The results from SCM/SSRM characterization have been compared with that from macroscopic C-V measurements on collective ZnO NWs and the differences are discussed. In addition to carrier profiling on NWs structure, applications of SCM/SSRM on some other ZnO-based nanostructures are also investigated including ZnO:Sb films, ZnO/ZnO:Sb core-shell NWs structure, ZnO/ZnMgO core-multishell coaxial heterostructures
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Osaka, Miki. "Nanoscale Electronic Properties of Conjugated Polymer Films Studied by Conductive Atomic Force Microscopy." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225631.
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Egan, Christopher Kieran. "Morphology, structure and electronic properties of CdTe surfaces studied by scanning tunneling microscopy." Thesis, Durham University, 2011. http://etheses.dur.ac.uk/835/.
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A scanning tunneling microscope has been used to study the surface properties of CdTe crystals. Coupled with scanning tunneling spectroscopy (STS) and atomic force microscopy, the surface morphology, structure and electronic properties of CdTe and CdZnTe surfaces have been studied. We have systematically investigated the three low index surface planes of the cubic crystal, that is the {100}, {110} and {111} surface planes. In addition, wet chemically treated surfaces were also examined. Clean surfaces were prepared in ultra-high vacuum conditions using argon ion sputtering and annealing. For each surface we imaged and recorded the surface reconstructions and morphologies. For the (100) surface, a mixed c(2x2)+(2x1) surface phase was found, where steps on the surface were found to preferentially align along <100> directions. For the (110) surface, tunneling spectroscopy was used to investigate the surface electronic structure of the (1x1) reconstruction. Using theoretical calculations of the tunneling current, we were able to match theory to experiment and discern the various vacuum tunneling processes for both n-type and semi-insulating material. For the (111) surface, a (2x2) reconstruction consisting of a cadmium vacancy structure was found. For the (-1-1-1) surface, a very disordered c(8x4) reconstruction was observed, consisting of a complicated tellurium terminated chain structure. For both faces, a large amount of faceting was observed to occur with the facets formed by {311} planes. Finally, wet chemically treated surfaces, important for the construction of many semiconductor devices, were investigated. Here the change in surface morphology for a variety of different common surface preparation methods was observed and, using STS, various surface electronic states were identified.
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Taber, Benjamen. "Real-Space Visualization of Organic Molecular Electronic Structure: Scanning Tunneling Microscopy and Spectroscopy." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23711.
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Organic electronics are becoming an increasingly important part of the semiconductor industry, with myriad applications enabled by their low cost, solution processability, and electrical conductivity. Charge transport in electronic applications involving organic semiconductor materials depends strongly on the electronic properties of nanoscale interfaces. Local variations in molecular environments can have a significant impact on the interfacial electronic properties, and subsequently the organic semiconductor electronic structure. Here, we use scanning tunneling microscopy and spectroscopy, supported by theoretical calculations, to investigate the impact of the local adsorption environment on the local density of states of oligothiophenes, carbon nanohoops, and carbon nanotubes. First, we present work showing that, for alkyl-substituted quaterthiophenes, molecular packing and electronic structure at interfaces differ substantially from the bulk, and a significant degree of structural and electronic variation occurs even in this relatively simple system. Then, we report on investigations of longer alkyl-substituted oligothiophenes, were we found a variety of planar molecular conformations that surprising exhibited similar, particle-in-a-box-like progressions of unoccupied molecular orbitals. Next, we share our research that found, for the first time, metal surface electrons confined within single adsorbed molecules. Finally, we study the impact of electrostatic defects in both metal and dielectric substrates on single-walled carbon nanotubes. The research presented in this dissertation increases our understanding of organic semiconductor interfaces and the impact of said interfaces on local molecular electronic structure, thereby aiding future organic semiconductor technological development.10000-01-01
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Chiaravalloti, Franco. "Electronic control of single molecules on ultra thin insulating layers by STM microscopy." Paris 11, 2009. http://www.theses.fr/2009PA112299.
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Le but de ce travail de thèse est d'explorer à l'échelle atomique les propriétés électroniques de nanostructures fabriquées par épitaxie moléculaire sur un substrat de silicium. La technique expérimentale employée est la microscopie à effet tunnel (STM) en Ultra Vide (UHV) à basse température (5 K). En premier lieu, des molécules de CaF2 sont déposées sur un substrat de silicium Si(100) chauffé à 1000K afin d'obtenir une couche mince ultra fine d'isolant sur semiconducteur. Des nanostructures cristallines sont observées à faible (0,3 ML) et haut (1,2 ML) taux de couverture, illustrant une fonctionnalisation de la surface. Une étude à température de dépôt inferieure est aussi présentée. Dans la deuxième partie de ce travail, une molécule organique (hexaphenyle) est déposée sur des couches de CaF2 d'épaisseur 1,2 ML sur Si(100). Le couplage électronique entre la molécule et le substrat est étudié en excitant électroniquement les molécules d'hexaphenyle à l'aide de la pointe du STM. Dans la troisième partie de cette thèse, des atomes d'or ont été déposés sur la surface propre de Si(100) et leur adsorption et diffusion de surface est étudiéeThe aim of this thesis is to explore the electronic properties of atomic size nanostructures fabricated on a silicon substrate. The experimental technique used is Scanning Tunnelling Microscopy (STM) performed in Ultra High Vacuum (UHV) at low temperature (5 K). First, molecular CaF2 is deposited by Molecular Beam Epitaxy (MBE) on the Si(100) substrate heated at 1000 K, obtaining an ultra thin insulating layer on semiconductor. Different crystalline nanostructures are observed at low (0,3 ML) and high (1,2 ML) coverage. A study of the epitaxy at lower substrate temperatures is also carried out, demonstrating different growth modes depending on the temperature. In the second part of this work, an organic molecule (hexaphenyl) is deposited on 1,2 ML thick CaF2 layers on Si. The electronic coupling between the molecule and the substrate is studied by electronically exciting the adsorbed hexaphenyl with the STM tip. In the third part of this thesis, gold atoms are deposited on the clean Si(100) surface and their adsorption sites and surface diffusion are studied
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Larkin, Joshua D. "Photon event distribution sampling (PEDS) image formation & high precision particle localization in scanning microscopy /." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3355587.
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Elkaseh, Akram Abdulsalam. "Fabrication of high-temperature superconducting nanobridges using atomic force microscopy." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1019.
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