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Krajnak, Matus. "Advanced detection in Lorentz microscopy : pixelated detection in differential phase contrast scanning transmission electron microscopy." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/7906/.
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Modern devices require fundamental length scales to be analysed in a maximum detail to enable research of new types of phenomena and design new materials. In this thesis, an advancement in Lorentz microscopy will be presented where the focus was placed not only onto resolution in spatial space but also onto resolution in reciprocal space. This allows greater sensitivity to measurements of the integrated magnetic induction within thin samples. This was achieved by a novel approach to the data acquisition, where instead of a segmented (annular) detector, a pixelated detector was used to measure the deflection of the scanning transmission microscopy (STEM) probe due to the in-plane integrated magnetic induction. Computer vision algorithms were researched to find an efficient, noise-robust way to register the deflection of the STEM probe. This enabled a novel approach to data analysis, where a scatter of the 2D integrated induction (a bivariate histogram) is used to show the distribution of the magnetic induction vector. The experimental results are supported by simulations, where a model of a thin polycrystalline sample causes a shift of the simulated beam due to phase modulations. The results of the detection in both the simulation and experiment showed that cross-correlation based processing can efficiently separate the low spatial frequencies (from the in-plane magnetic induction), and high spatial frequencies (from the structure of the polycrystalline sample). This work will enable quantitative analysis of a greater number of thin magnetic samples, for which the current methods are hampered by the diffraction contrast. This will be particularly helpful for the study low moment, out of plane, magnetised thin films. Currently such systems are of great interest due to the tunability of their magnetic properties and the novel magnetic structures present within them. This work also provides an important step for computational methods in transmission electron microscopy, as this is one of the first examples of 4D data acquisition of processing in STEM (where two dimensions represent the spatial scanning dimensions and other two the reciprocal space). Imaging methods developed in this thesis were applied to the topic of skyrmions in a thin layer of a FeGe cubic helimagnet, where the very fine detail of the structure of their in-plane integrated magnetic induction was shown to contain a distorted modulations of its profile. This was compared to a simple three harmonic frequency model, which was altered to fit some characteristics of the imaged magnetic skyrmions. In this work, for the first time, a direct comparison of differential phase contrast and electron holography will be shown for a simple experiment in which the integrated electric field between two needles was measured in free space in the same microscope. Although it was concluded that both methods are equivalent, some small discrepancies of measured values were present due to a long range electric field in electron holography and/or drift of the beam in between scans in STEM.
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Pickford, Rachael Anne. "A study of magnetic properties of hard and soft magnetic materials by Lorentz transmission electron microscopy and magnetic x-ray circular dichroism." Thesis, University of York, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367489.
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Srivastava, Abhay Kant [Verfasser], Stuart S. P. [Gutachter] Parkin, Ingrid [Gutachter] Mertig, and Christian [Gutachter] Back. "Investigations of anti-skyrmions and Néel skyrmions using Lorentz Transmission Electron Microscopy / Abhay Kant Srivastava ; Gutachter: Stuart S. P. Parkin, Ingrid Mertig, Christian Back." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2021. http://d-nb.info/122730174X/34.
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Vaňatka, Marek. "Statické a dynamické vlastnosti nanostrukturovaných magnetických materiálů." Doctoral thesis, Vysoké učení technické v Brně. CEITEC VUT, 2021. http://www.nusl.cz/ntk/nusl-438773.
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Magnetické materiály a z nich vyrobené nanostruktury jsou v průběhu posledních let studovány pro jejich aplikace v např. záznamových médiích a logických obvodech. Tato práce navazuje na náš předchozí výzkum tohoto oboru s hlavním zaměřením na statické a dynamické vlastnosti nanostrukturovaných magnetických materiálů, jako například NiFe, CoFeB a YIG. Práce začíná teoretickým úvodem s popisem mikromagnetických systémů, dynamiky magnetických vortexů, feromagnetické rezonance (FMR) a spinových vln včetně jejich disperzních vlastností. Následuje popis použitých experimentálních metod a první experimentální část zabývající se nukleačním procesem magnetického vortexu, jinými slovy procesem transformace ze saturovaného stavu do spinové konfigurace magnetického vortexu v průběhu snižování magnetického pole. Jsou použity mikroskopické metody zobrazující magnetickou strukturu materiálu, jmenovitě Lorentzova transmisní elektronová mikroskopie a rentgenová transmisní mikroskopie. Výsledky jsou poté korelovány s měřením elektrické odezvy pomocí jevu anizotropní magnetorezistence. Výhodou elektrických měření je, že plně elektrická detekce dovoluje použití tohoto systému v uzavřených systémech integrovaných obvodů. Výsledky oblasti nukleací magnetických vortexů ukazují, že při tomto procesu prochází magnetizace v nano- a mikrometrových magnetických discích několika fázemi s růsnými typy spinových konfigurací nazvaných nukleační stavy. Dále je představeno měření magnetických materiálů pomocí vektorového síťového analyzátoru (VNA), což je aplikováno na měření resonance magnetických vortexů (určení gyrotropické frekvence a měření vysokofrekvenčních módů), feromagnetické rezonance tenkých vrstev (získání základních magnetických materiálových parametrů) a spektroskopii spinových vln. Právě spektroskopie spinových vlna je rozvinuta za účelem měření disperzních relací tenkých magnetických vrstev, což je základní charakteristika, jejíž znalost je důležitá v návrhu aplikací. Nakonec je představeno anténní zařízení, díky kterému lze oddělit magnetické buzení od vzorku samotného bez nutnosti absolvovat proces elektronové litorafie, což je zapotřebí v klasickém přístupu antény na vzorku a kontaktování vysokofrekvenční sondou. Toto zařízení se skládá ze skleněného kantilívru, na kterém je vyrobena budící anténa, konektoru a spojovacího prvku v podobě plošného spoje. Celé zařízení je díky umístění na x-y-z stolek s náklonem pozicovatelné a lze tedy měřit v jakémkoliv místě vzorku. Umístění antény na sklo umožňuje navigaci pomocí mikroskopu a optické měření, např. metodou Brillouinova světelného rozptylu (BLS) nebo Kerrova jevu.
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Andersen, Ingrid Marie. "2D and 3D quantitative TEM mapping of CoNi nanowires." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30205.
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Les nanofils magnétiques constituent un domaine de recherche en plein essor. De section cylindrique, ils permettent la propagation des parois de domaines magnétiques à très grandes vitesses et des interactions fortes avec les ondes de spin, ce qui les rend particulièrement intéressants pour le développement de futurs composants de la spintronique. L'objectif de ce travail de thèse est de fournir une analyse quantitative et qualitative complète de la configuration magnétique locale dans des nanofils magnétiques cylindriques d'alliage CoNi à anisotropie magnétocristalline perpendiculaire en utilisant les techniques d'imagerie magnétique avancées de la microscopie électronique à transmission (MET), principalement axées sur l'holographie électronique (HE). Une étude corrélative entre les propriétés structurales, les variations locales de composition et les configurations magnétiques de ces nanofils a été réalisée. De plus, les configurations tridimensionnelles (3D) complexes des domaines et des parois magnétiques ont été analysées par tomographie holographique de champ vectoriel (THCV) afin d'obtenir les trois composantes de l'induction magnétique. Enfin, un protocole a été développé pour étudier in situ par microscopie de Lorentz la configuration magnétique de ces nanofils lors de l'injection d'impulsions de courant. La première partie de ce travail est focalisée sur la corrélation des configurations magnétiques de nanofils individuels de CoNi avec les propriétés structurales et chimiques locales. L'orientation de la phase cristalline a été cartographiée en diffraction électronique par précession et combinée à des mesures de composition par spectroscopie de perte d'énergie des électrons. Les résultats révèlent une coexistence de grains de phase cfc et de phase hcp, cette dernière présente sa direction cristallographique c orientée presque perpendiculairement à l'axe du nanofil. Cette coexistence de phases cristallographiques est à l'origine de variations localisées et abruptes de la configuration magnétique. Deux nanofil configurations principales ont été observées : une chaîne d'états transversaux par rapport à l'axe du, de type vortex, et un état longitudinal. Nous avons observé que les états transversaux sont liés à la phase hcp possédant une forte anisotropie magnétocristalline perpendiculaire, ce que confirment les simulations micromagnétiques. Une autre partie de ce travail concerne l'étude de la structure magnétique 3D des domaines et des parois de domaines dans la phase hcp. Cette étude a été menée pour des états rémanents différents en fonction de l'application d'un champ de saturation perpendiculaire et parallèle à l'axe du nanofil. Les mesures ont été réalisées par la méthode THCV afin d'extraire les trois composantes de l'induction magnétique et reconstruire en 3D la configuration magnétique locale du nanofil. Les résultats montrent une stabilisation d'une chaîne de vortex dans le cas d'une saturation perpendiculaire, et des états d'enroulement longitudinaux séparés par des parois de domaine transversales après l'application d'un champ externe parallèle à l'axe du fils. La dernière partie du manuscrit présente les résultats obtenus en microscopie de Lorentz in situ démontrant la possibilité de manipuler les parois des domaines magnétiques d'un nanofil de CoNi par injection d'impulsions électriques. Cette preuve de concept est considérée comme le précurseur des observations in situ de la dynamique des parois de domaines en EH. Un protocole précis, axé sur les étapes cruciales de préparation des échantillons et les développements à poursuivre pour réaliser ces expériences délicates, est détailléCylindrical magnetic nanowires (NWs) are currently subjects of high interest due to fast domain wall velocities and interaction with spin-waves, which are considered interesting qualities for developing future spintronic devices. This thesis aims to provide a wholesome quantitative and qualitative analysis of the local magnetic configuration in cylindrical Co-rich CoNi NWs with perpendicular magnetocrystalline anisotropy using state-of-the-art transmission electron microscopy (TEM) magnetic imaging techniques, mainly focused on two-dimensional (2D) and three-dimensional (3D) electron holography (EH). A correlative study between the NW's texture, modulation in composition, and magnetic configuration has been conducted. Further, the complex 3D nature of the domain and domain wall configurations have been analyzed using holographic vector field electron tomography (VFET) to retrieve all three components of the magnetic induction. Finally, I have successfully manipulated the magnetic configuration observed by Lorentz microscopy in Fresnel mode by the in situ injection of a current pulse. A TEM study comparing the magnetic configuration to the local NW structure was performed on single NWs. The crystal phase analysis was done by precession electron diffraction assisted automated crystal orientation mapping in the TEM combined with compositional analysis by scanning-TEM (STEM) electron energy loss spectroscopy (EELS) for a detailed correlation with the sample's magnetic configuration. The results reveal a coexistence of fcc grains and hcp phase with its c-axis oriented close to perpendicular to the wire axis in the same NW, which is identified as the origin of drastic local changes in the magnetic configuration. Two main configurations are observed in the NW region: a chain of transversal vortex-like states and a longitudinal curling state. The chain or vortices are linked to the hcp grain with the perpendicular magnetocrystalline anisotropy, as confirmed by micromagnetic simulations. The 3D magnetic structure of the domains and domain walls observed in the hcp grain of the NWs has been studied for two different remnant states: after the application of a saturation field perpendicular (i) and parallel (ii) to the NW axis. The measurements were done using state-of-the-art holographic VFET to extract all three components of the magnetic induction in the sample, as well as a 3D reconstruction of the volume from the measured electric potentials, giving insight into the local morphology of the NW. The results show a stabilization of a vortex chain in the case of perpendicular saturation, but longitudinal curling states separated by transversal domain walls after applying a parallel external field. Finally, preliminary Lorentz microscopy results are presented, documenting the manipulation of magnetic domain walls by the in situ injection of electrical pulses on a single cylindrical CoNi nanowire contacted by focused ion beam induced deposition. This is believed to be the forerunner for quantitative electrical measurements and in situ observations of domain wall dynamics using EH at the CEMES. A detailed protocol focusing on the crucial steps and challenges ahead for such a delicate experiment is presented, together with suggestions for future work to continue the developments
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Ahmed, Adam Saied. "Skyrmions and Novel Spin Textures in FeGe Thin Films and Artificial B20 Heterostructures." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492686407034025.
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Jin, Liang. "Direct electron detection in transmission electron microscopy." Diss., [La Jolla, Calif.] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3344737.
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Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed April 3, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 148-151).
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Rodríguez, González Luis Alfredo. "In situ Lorentz microscopy and electron holography in magnetic nanostructures." Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2554/.
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Nous avons développé dans cette thèse des études quantitatives et qualitatives par microscopie de Lorentz (LM) et holographie électronique (EH) des configurations magnétiques de nanostructures étudiées in-situ sous champ magnétique ou à basse température. Les trois nanostructures magnétiques étudiées sont: des nanofils de Co et de Co50Fe50, des réseaux d'antidot de Co et des couches minces de La2/3Ca1/3MnO3. Les experiences de manipulation de parois de domaine magnétique (DW) dans les nanofils ont permis l'étude de la nucleation des DW, de leur propagation, de leur piégeage et dépiegage. Par LM nous avons étudié la configuration magnétique à la remanence et les processus de retournement dans les réseau d'antidots à haute densité. Enfin, nous avons mis en evidence par EH à 100K une separation de phase magnétique et une variation de l'anisotropie magnétocristalline dans les films minces de LCMO resultant de la déformation épitaxiale induite par le substratIn this thesis, we have developed quantitative and qualitative studies of the magnetic states of different magnetic nanostructures by in situ Lorentz Microscopy (LM) and Electron Holography (EH) experiments under application of magnetic field or working at low temperature (100 K), on three different magnetic nanostructures: L-shape Co and Co50Fe50 nanowires, Co antidot arrays and strained La2/3Ca1/3MnO3. DW manipulation experiments by magnetic field allowed characterize process such as DW nucleation, propagation, pinning and depinning in the nanowires. By in situ LM, remanent magnetic states and reversal magnetization process in high-density antidot arrays were studied. Finally, the effect of the substrate-induced strain in LCMO thin film were studied by EH at 100 K. We found that such strain effect produce a magnetic phase separation and/or variation in the magnetocrystalline anisotropy
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Worden, R. H. "Transmission electron microscopy of metamorphic reactions." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234381.
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Chan, Yu Fai. "Nanostructure characterization by transmission electron microscopy /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202002%20CHAN.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 62-63). Also available in electronic version. Access restricted to campus users.
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McKeown, Karen. "Using scanning electron microscopy (SEM) and transmission electron nncroscopy." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492019.
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Electron impact excitation collisions are important processes for spectral line formation of plasmas. The work undertaken in this thesis focuses on such collisions involving Li-like ions, important in both astrophysical and magnetically confined plasmas. By having reliable atomic and collisional data, such as energy levels, radiative rates and excitation rate coefficients, it is possible to generate models to describe such plasmas. The atomic data were calculated using the General-Purpose Relativistic Structure Program (GRASP; Dyall et al 1989), for several Li-like ions, namely S XIV, Ar XVI, Ca XVIII, Ti XX, Cr XXII, Fe XXIV and Ni XXVI. Including relativistic effects in the calculations leads to the generation of 24 fine-structure energy levels when orbitals with 11,/ =:; 5 are considered. Oscillator strengths, were generated for all 276 transitions arising amongst these levels when maintaining a frozen core of Is2 • Comparisons were made with both theoretical and experimental data available from the publications of Nahar & Pradhan (1999), Nahar (2002), Whiteford et al (2002) and Del Zanna (2006), along with NIST data. Collisional calculations were performed for Fe XXIV, an abundant ion in solar and fusion plasmas, which has the potential to be employed in photo-pumping schemes for X-ray lasers. The calculations were performed using the Dirac Atomic Relativistic Code (DARC; Ait-Tahar, Grant & Norrington 1996), which is a fully relativistic code based on R-matrix theory. In addition to carrying out these calculations, DARC was further developed to provide a solution to the problem of convergence which affects optically allowed transitions in the above threshold energy region. Comparison of these results was made with data already available in the literature, with discrepancies being highlighted and discussed. The work of Berrington & Tully (1997) did not include the n=5 orbital, and comparisons with the results presented here showed how important these are for low temperatures. Discrepancies between this work and that of Whiteford et al (2002) were also identified. Despite being given access to their unpublished data, the source of the identified discrepancies remains elusive. The problems identified require further investigation which lies beyond the scope and resources of the present work.
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Findlay, Scott David. "Theoretical aspects of scanning transmission electron microscopy /." Connect to thesis, 2005. http://eprints.unimelb.edu.au/archive/00001057.
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Koda, Nobuko. "Transmission electron microscopy studies of fega alloys." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/167.
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Thesis (M.S.) -- University of Maryland, College Park, 2003.Thesis research directed by: Dept. of Material, Science and Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Hetherington, C. "Transmission electron microscopy of GaAs/AlGaAs multilayers." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379967.
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Dwyer, C. "Scattering theory for advanced transmission electron microscopy." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598710.
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Aspects of a theoretical and computational basis for the simulation of fast electron scattering in a solid due to elastic, electron-phonon and atomic ionisation events are developed. The primary motivation for this work arises from the need for detailed simulations of fast electron scattering to assist in the quantitative interpretation of experimental data acquired using high-spatial-resolution analytical techniques in the scanning transmission electron microscope. The scattering behaviour of Å-scale electron probes in simple atomic structures is examined with specific reference to the origin of core energy-loss signals and the spatial resolution of annular dark-field images generated by such probes. A multiscale theory of the dynamical elastic and inelastic scattering of fast electrons is then developed. This theory is applicable to many forms of inelastic scattering, and is developed in the form of a multi-dimensional extension of the well-known multislice theory of dynamical elastic scattering of fast electrons. Methods for obtaining the key quantities required for the application of this theory to the inelastic scattering of fast electrons due to atomic ionisation are presented. One of these methods is extended to enable the inclusion of relativistic effects in the ionisation process. A preliminary test of the multislice theory is made by comparing calculated and experimental characteristic-loss electron diffraction patterns acquired from silicon. The treatment of incoherent electron waves using Monte Carlo integration, which in certain circumstances can reduce computation time dramatically, is also demonstrated. Finally, the predictions of the theory are compared with those of approximate methods for calculating the origin of the core energy-loss signal in the scanning transmission electron microscope.
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Whittle, Caroline Kay. "Analytical transmission electron microscopy of authigenic chlorites." Thesis, University of Sheffield, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324284.
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Cardoch, Sebastian. "Studying Atomic Vibrations by Transmission Electron Microscopy." Thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305370.
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We employ the empirical potential function Airebo to computationally model free-standing Carbon-12 graphene in a classical setting. Our objective is to measure the mean square displacement (MSD) of atoms in the system for different average temperatures and Carbon-13 isotope concentrations. From results of the MSD we aim to develop a technique that employs Transmission Electron Microscopy (TEM), using high-angle annular dark filed (HAADF) detection, to obtain atomic-resolution images. From the thermally diffusive images, produced by the vibrations of atoms, we intent to resolve isotopes types in graphene. For this, we establish a relationship between the full width half maximum (FWHM) of real-space intensity images and MSD for temperature and isotope concentration changes. For the case of changes in the temperature of the system, simulation results show a linear relationship between the MSD as a function of increased temperature in the system, with a slope of 7.858×10-6 Å2/K. We also note a power dependency for the MSD in units of [Å2] with respect to the FWHM in units of [Å] given by FWHM(MSD)=0.20MSD0.53+0.67. For the case of increasing isotope concentration, no statistically significant changes to the MSD of 12C and 13C are noted for graphene systems with 2,000 atoms or more. We note that for the experimental replication of results, noticeable differences in the MSD for systems with approximately 320,000 atoms must be observable. For this, we conclude that isotopes in free-standing graphene cannot be distinguished using TEM.
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Zhang, Yucheng. "Characterisation of GaN using transmission electron microscopy." Thesis, University of Cambridge, 2008. https://www.repository.cam.ac.uk/handle/1810/252119.
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Meng, Ting, and Yating Yu. "Deconvolution algorithms of 2D Transmission Electron Microscopy images." Thesis, KTH, Optimeringslära och systemteori, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-110096.
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The purpose of this thesis is to develop a mathematical approach and associated software implementation for deconvolution of two-dimensional Transmission Electron Microscope (TEM) images. The focus is on TEM images of weakly scattering amorphous biological specimens that mainly produce phase contrast. The deconvolution is to remove the distortions introduced by the TEM detector that are modeled by the Modulation Transfer Function (MTF). The report tests deconvolution of the TEM detector MTF by Wiener _ltering and Tikhonov regularization on a range of simulated TEM images with varying degree of noise.The performance of the two deconvolution methods are quanti_ed by means of Figure of Merits (FOMs) and comparison in-between methods is based on statistical analysis of the FOMs.
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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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Strobel, Julian [Verfasser]. "Transmission Electron Microscopy on Memristive Devices / Julian Strobel." Kiel : Universitätsbibliothek Kiel, 2019. http://d-nb.info/1185485244/34.
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TIYYAGURA, MADHAVI. "TRANSMISSION ELECTRON MICROSCOPY STUDIES IN SHAPE MEMORY ALLOYS." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3913.
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In NiTi, a reversible thermoelastic martensitic transformation can be induced by temperature or stress between a cubic (B2) austenite phase and a monoclinic (B19') martensite phase. Ni-rich binary compositions are cubic at room temperature (requiring stress or cooling to transform to the monoclinic phase), while Ti-rich binary compositions are monoclinic at room temperature (requiring heating to transform to the cubic phase). The stress induced transformation results in the superelastic effect, while the thermally induced transformation is associated with strain recovery that results in the shape memory effect. Ternary elemental additions such as Fe can additionally introduce an intermediate rhombohedral (R) phase between the cubic and monoclinic phase transformation. This work was initiated with the broad objective of connecting the macroscopic behavior in shape memory alloys with microstructural observations from transmission electron microscopy (TEM). Specifically, the goals were to examine (i) the effect of mechanical cycling and plastic deformation in superelastic NiTi; (ii) the effect of thermal cycling during loading in shape memory NiTi; (iii) the distribution of twins in martensitic NiTi-TiC composites; and (iv) the R-phase in NiTiFe. Both in situ and ex situ lift out focused ion beam (FIB) and electropolishing techniques were employed to fabricate shape memory alloy samples for TEM characterization. The Ni rich NiTi samples were fully austenitic in the undeformed state. The introduction of plastic deformation (8% and 14% in the samples investigated) resulted in the stabilization of martensite in the unloaded state. An interlaying morphology of the austenite and martensite was observed and the martensite needles tended to orient themselves in preferred orientations. The aforementioned observations were more noticeable in mechanically cycled samples. The observed dislocations in mechanically cycled samples appear to be shielded from the external applied stress via mismatch accommodation since they are not associated with unrecoverable strain after a load-unload cycle. On application of stress, the austenite transforms to martensite and is expected to accommodate the stress and strain mismatch through preferential transformation, variant selection, reorientation and coalescence. The stabilized martensite (i.e., martensite that exists in the unloaded state) is expected to accommodate the mismatch through variant reorientation and coalescence. On thermally cycling a martensitic NiTi sample under load through the phase transformation, significant variant coalescence, variant reorientation and preferred variant selection was observed. This was attributed to the internal stresses generated as a result of the thermal cycling. A martensitic NiTi-TiC composite was also characterized and the interface between the matrix and the inclusion was free of twins while significant twins were observed at a distance away from the matrix-inclusion interface. Incorporating a cold stage, diffraction patterns from NiTiFe samples were obtained at temperatures as low as -160ºC. Overall, this work provided insight in to deformation phenomena in shape memory materials that have implications for engineering applications (e.g., cyclic performance of actuators, engineering life of superelastic components, stiffer shape memory composites and low-hysteresis R-phase based actuators). This work was supported in part by an NSF CAREER award (DMR 0239512).M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Batstone, J. L. "Cathodoluminescence and transmission electron microscopy characterization of ZnSe." Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355952.
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Nellist, Peter David. "Image resolution improvement in scanning transmission electron microscopy." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361613.
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Holsgrove, Kristina. "Transmission electron microscopy study of domains in ferroelectrics." Thesis, Queen's University Belfast, 2017. https://pure.qub.ac.uk/portal/en/theses/transmission-electron-microscopy-study-of-domains-in-ferroelectrics(e83e215a-bcf7-465b-bab9-31442486bb71).html.
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This thesis investigates domain dynamics in one of the most well-known ferroelectric materials – polycrystalline BaTiO3 ceramics, and one of today’s most promising ferroelectric materials for future device applications – mixed-phase BiFeO3 thin films. The investigations use primarily TEM techniques accompanied by relevant theory and AFM techniques. The study on polycrystalline BaTiO3 (FIB lamellae) aims to further understand the link between domains coupling across adjacent grains and to explore the domains’ re-ordering as a function of heating through TC. Two cases were explored: domains coupling across a single grain boundary, and a more complex case of domains within adjacent grains meeting around a junction (or pore). Analysis using martensite crystallography theory demonstrated that domains sharing a single grain boundary do on average arrange themselves in a compatible and stress-free manner. For the example of grains arranged around a junction, a computational example was created, given the complexity of the case. It was demonstrated that the relaxation of the out-of-plane constraint gives rise to an undetermined set of linear equations which can be solved for compatible domain wall orientations and volume fractions of domains, indicating that groups of adjacent grains can form stress-free domain patterns. STEM in-situ heating cycle experiments, heating and cooling through TC, showed that the re-configuration of the domain structure (domain density, favourable domain orientations and presence of domain bundles) was directly influenced by the rate and continuous/dis-continuous nature of the performed heating cycles. Furthermore, this material was explored with focus on the functionality of its positive temperature coefficient of resistivity (PTCR) effect. Aberration-corrected STEM and EELS revealed a grain boundary PbTiO3-like region (~10-15 nm), which was associated with an increased local polarisation in that region. The chemical and electronic heterogeneity of the ceramic was linked to the changes in potential barrier at the grain boundary, theorised by the Heywang-Jonker model. It was inferred that the confined PbTiO3 rich grain boundary region would have a higher spontaneous polarisation (than BaTiO3), thus reducing the grain boundary barrier potential further below TC, augmenting electronic transport and enhancing the magnitude of resistivity jump at TC, and so justifying the optimised PTCR effect exhibited by this ceramic. For the study on phase reversibility in BiFeO3 thin films, the native polymorphs, known as T and R, were initially identified. The thermal activation phase transformation was investigated by STEM in-situ heating cycle experiments; showing a lateral growth of the highly-strained T phase above 400°C. Additionally, an AFM tip was used to locally apply electric field and stress, demonstrating reversible switching between the native mixed-phase and a pure T phase state. Energy-based effective Hamiltonian simulations verified phase competition under the application of electric field and stress, comparable to experimental data. The stress-written phase boundaries (R’/T’) were investigated via c-AFM showing enhanced conductivity. TEM analysis of cross-sectional lamellae from pre-written AFM regions revealed that the stress-written R’ and T’ polymorphs differ in structure from the native polymorphs and, the R’/T’ boundaries have higher in-plane strain gradients compared to the native R/T boundaries, rationalising the enhanced conductivity as a strain mediated effect.
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Ramasse, Quentin Mathieu. "Diagnosis of aberrations in scanning transmission electron microscopy." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615070.
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Webster, Richard Francis. "Transmission electron microscopy of indium gallium nitride nanorods." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690381.
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Indium Gallium Nitride (InxGa1_xN) and associated III-nitride compounds are widely researched for optoelectronic applications such as solar cells and light emitting and laser diodes. These materials generally suffer from high threading dislocation densities (> x 109 cm-2) due to a large lattice mismatch between the nitride film and foreign substrates used for growth. This thesis is primarily concerned with studying the structural and compositional characterisation of InxGa1-xN nanorod arrays which may be used to reduce dislocation densities. Indium nitride and InxGa1-xN nanorods arrays have been grown on silicon (111) substrates at the University of Nottingham using plasma-assisted molecular beam epitaxy (PA-MBE).
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Soundararajah, Queenie Yoganandhi. "Characterization of InGaN nanorods using transmission electron microscopy." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720816.
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Bücker, Kerstin. "Characterization of pico- and nanosecond electron pulses in ultrafast transmission electron microscopy." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAE014/document.
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Cette thèse présente une étude des impulsions électroniques ultra-brèves en utilisant le nouveau microscope électronique en transmission ultrarapide (UTEM) à Strasbourg. La première partie porte sur le mode d’opération stroboscopique, basé sur l’utilisation d’un train d’impulsions d’électrons de l’ordre de la picoseconde pour l’étude des phénomènes réversibles ultrarapides. L’étude paramétrique effectuée a permis de révéler les dynamiques fondamentales des impulsions électroniques. Des mécanismes inconnus jusqu’alors et décisifs dans les caractéristiques des impulsions ont été dévoilés. Il s’agit des effets de trajectoire, qui limitent la résolution temporelle, et du filtrage chromatique, qui impacte la distribution en énergie et l’intensité du signal. Ces connaissances permettent aujourd’hui un paramétrage affiné de l’UTEM de manière à satisfaire les divers besoins expérimentaux. La deuxième partie concerne l’installation du mode d’opération complémentaire : le mode « singel-shot ». Ce mode fait appel à une impulsion unique d’intensité élevé et d’une durée de l’ordre de la nanoseconde pour l’étude des phénomènes irréversibles. L’UTEM de Strasbourg étant le premier instrument single-shot équipé d’un spectromètre de perte d’énergie des électrons (EELS), l’influence de l’aberration chromatique a pu été étudiée en détail. Elle s’est dévoilée être une limitation majeure pour la résolution en imagerie, nécessitant d’ajuster le bon compromis avec l’aberration sphérique d’une part et l’intensité du signal d’autre part. Enfin, la faisabilité de mener des études en EELS ultrarapide avec une seule impulsion nanoseconde a pu être démontrée, ceci constituant une première mondiale. Ce résultat très prometteur ouvre un tout nouveau domaine d’expériences résolu en tempsThis thesis presents a study of ultrashort electron pulses by using the new ultrafast transmission electron microscope (UTEM) in Strasbourg. The first part focuses on the stroboscopic operation mode which works with trains of picosecond multi-electron pulses in order to study ultrafast, reversible processes. A detailed parametric study was carried out, revealing fundamental principles of electron pulse dynamics. New mechanisms were unveiled which define the pulse characteristics. These are trajectory effects, limiting the temporal resolution, and chromatic filtering, which acts on the energy distribution and signal intensity. Guidelines can be given for optimum operation conditions adapted to different experimental requirements. The second part starts with the setup of the single-shot operation mode, based on intense nanosecond electron pulses for the investigation of irreversible processes. Having the first ns-UTEM equipped with an electron energy loss spectrometer, the influence of chromatic aberration was studied and found to be a major limitation in imaging. It has to be traded off with spherical aberration and signal intensity. For the first time, the feasibility of core-loss EELS with one unique ns-electron pulse is demonstrated. This opens a new field of time-resolved experiments
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Tao, Shizhong. "High-resolution transmission electron microscopy of copper-oxide compounds /." [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10775.
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Pretorius, Angelika. "Transmission electron microscopy of GaN based, doped semiconductor heterostructures." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981822002.
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Hashimoto, Richard Y. "Analytical transmission electron microscopy studies on copper-alumina interfaces." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA362728.
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Cherns, Peter David. "A transmission electron microscopy study of AlGaN/GaN heterostructures." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597581.
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The use of an A1N interlayer to allow the growth of crack-free AlGaN on a GaN template is investigated. The impact of using an A1N interlayer on the active region of a device is examined by investigating a series of GaN/AlGaN quantum well structures. It is observed by WBDF that the a-type dislocations generated at the A1N interlayer form ‘staircase’ structures in the quantum well stack where all dislocation segments are in edge orientation A model is proposed where misfit dislocation segments at each well interface are formed by climb, in contrast to the dislocation glide at the lowest interface that might be expected in other systems. Both HAADF imaging and conventional TEM are used to characterise a series of Al-GaN/GaN quantum cascade laser (QCL) structures. These devices have great potential in the field of fibre optic communication. Changes in the layer spacing near V-defects, and the effects that changing substrate from sapphire to bulk GaN have on the mechanisms for relaxation in this system are identified and discussed.
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Kuang, Qie. "Structural studies of membrane proteins using transmission electron microscopy." Doctoral thesis, KTH, Strukturell bioteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-161721.
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Membrane proteins play important roles for living cells. They control transportation of ions, solutes, and nutrients across the membrane and catalyze metabolic reactions. Transmission electron microscopy has its advantages in convenient sample preparation, straightforward structural determination, and wide applications for diverse specimens. In this thesis, the structure of three membrane proteins are studied by this method. Kch, a potassium channel in Escherichia coli, has a transmembrane part and a cytosolic domain. Large and well-ordered two dimensional crystals were obtained from both a functional mutant (KchM240L) and a modified protein possessing only the transmembrane part (KchTM). Both samples crystallize as two symmetry-related overlapping layers. Furthermore, the KchTM structure was reconstructed which showed that the transmembrane part of the two adjacent proteins are involved in forming the crystal contacts. Thus, the cytosolic domains of Kch in crystals are deduced to expose to the solvent and do not interact with each other. MGST1 (microsomal glutathione transferase 1) is a detoxification enzyme. It was recombinantly over-expressed in the current study, instead of purified from rat liver as before. The crystallization condition was adjusted and isomorphic crystals were obtained. The refined model was built from a combined data set consisting of previous and new diffraction patterns. More residues at the C-terminus of the transmembrane helix 1 were assigned and the residues in the transmembrane helices 3 and 4 were remodeled. Several phospholipid molecules were observed and the ligand glutathione adopts an extended conformation in the refined model. The structure of MelB (a sugar/sodium symporter in Escherichia coli) was determined using a refined single particle reconstruction method. This novel method is aimed for processing small or locally distorted crystals. In comparison with the previously published single particle reconstruction protocol, the current method is improved in several aspects. A more reliable reconstruction of MelB was obtained and the resolution was increased. The docking experiment indicates that MelB adopts an open conformation under the present two dimensional crystallization condition. Electron microscopy has developed quickly recently with the help of modern instruments, techniques, and software. This method will without doubt play a more critical role in future structural biology.QC 20150320
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Wisnet, Andreas. "1D TiO2 nanostructures probed by 2D transmission electron microscopy." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-179430.
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Hybrid solar cells based on nanoparticulate TiO2, dye and poly(3-hexylthiophene) are a common benchmark in the field of solid-state dye-sensitized solar cells. One-dimensionally nanostructured titanium dioxide is expected to enhance power-conversion efficiency (PCE) due to a high surface area combined with a direct path for electrons from the active interface to the back electrode. However, current devices do not meet those expectations and cannot surpass their mesoporous counterparts. This work approaches
the problem by detailed investigation of diverse nanostructures on a nanoscale by advanced transmission electron microscopy (TEM). Anodized TiO2 nanotubes are analyzed concerning their crystallinity. An unexpectedly large grain size is found, and its implication is shown by corresponding solar cell characteristics which feature an above-average fill factor. Quasi-single crystalline rutile nanowires are grown hydrothermally, and a peculiar defect structure consisting of free internal surfaces is revealed. A growth model based on Coulombic repulsion and steric hindrance is developed to explain the resulting V-shaped defect cascade. The influence of the defects on solar cell performance is investigated and interpreted by a combination of TEM, electronic device characterization and photoluminescence spectroscopy, including lifetime measurements. A specific annealing treatment is proposed to counter the defects, suppressing several loss mechanisms and resulting in an improvement of PCEs by 35 %. Simultaneously, a process is developed to streamline electron-tomographic reconstruction of complex nanoparticles. Its suitability is
demonstrated by the reconstruction of a gold nanostar and a number of iron-based particles distributed on few-layered graphene.
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Smith, Jaqueline Margaret. "Microcharacterisation of halogenated copper phthalocyanines using transmission electron microscopy." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241835.
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Murdoch, Susan Jane Tara. "Transmission electron microscopy study of advanced magnetic sensor films." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410170.
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Trevor, Colin. "Transmission electron microscopy of chemical vapour deposited diamond films." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295064.
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Jian, Nan. "Scanning transmission electron microscopy of atomic structure of nanoparticle." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7131/.
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This thesis presents the researches on the size and atomic structure of the nanoclusters including ligand protected monometallic clusters, ligand protected bimetallic clusters and biological metallic clusters, by using aberration corrected HAADF -STEM. The atom counting method with size selected clusters as mass balance was utilized to "fractionate" the relative broad distributed sample and make the structure study focus on the certain size range. The atomic structures of Auss Schmid clusters were investigated. Nearly half of these clusters were found to have a hybrid structure. A combination of geometric size analysis and atom counting method was performed to determine both the size and composition of the AuAg alloy clusters. We found that Ag-rich clusters tend to have an icosahedral structure while the Au-rich clusters prefer the fcc structure. For the biological nanoparticles, the ferritins' iron loadings were obtained. Different morphologies of the ferritin iron cores were observed as a function of iron loading, suggesting the iron core growth process in the protein shell. The HAADF -STEM was also successfully employed to characterize the ultra-small Au and Pd catalysts supported on the Ti02, which are helpful to understand the catalytic performance of these catalysts. A multilayer deposition method was developed to accommodate and process the large abundance of clusters from the new high-flux cluster source. With the similar experimental setup, size-selected colloidal clusters were produced by dissolving the multilayer cluster-PVP stacks. The colloidal clusters were observed by the STEM and their sizes were found to be conserved during the dissolving process.
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Kong, Lisa (Lisa Fanzhen). "High-resolution transmission electron microscopy of III-V FinFETs." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119065.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 47-50).
III-V materials have great potential for integration into future complementary metal-oxide-semiconductor technology due to their outstanding electron transport properties. InGaAs n-channel metal-oxide-semiconductor field-effect transistors have already demonstrated promising characteristics, and the antimonide material system is emerging as a candidate for p-channel devices. As transistor technology scales down to the sub-10-nm regime, only devices with a 3D configuration can deliver the necessary performance. III-V fin field-effect transistors (finFETs) have displayed impressive characteristics but have shown degradation in performance as the fin width is scaled to the sub-10-nm regime. In this work, we use high-resolution transmission electron microscopy (HRTEM) in an effort to understand how interfacial properties between the channel and high-k dielectric affect device performance. At the interface between the channel material, such as InGaSb or InGaAs, and the high-k gate dielectric, properties of interest include defect density, interdiffusion between the semiconductor and dielectric, and roughness of the dielectric - semiconductor interface. Using HRTEM, we can directly study this interface and try to understand how it is affected by different processing conditions and its correlation with device characteristics. In this thesis, we have analyzed both InGaAs and InGaSb finFETs with state-of-the-art fin widths. Analysis of TEM images was combined with electrical data to correlate interfacial properties with device performance. We compared the materials properties of InGaAs and InGaSb and also explored the impact of processing steps on interfacial properties.
by Lisa Kong.
S.B.
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Liu, Chuan-Pu. "Characterisation of ultrathin semiconductor layers using transmission electron microscopy." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624121.
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Liberti, Emanuela. "Transmission electron microscopy of titanium dioxide nanoplatelets and nanorods." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/40093.
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As the size of the bulk crystal reduces to the nanometre scale, anatase titania exhibits enhanced photocatalytic properties. Nanostructuring of TiO2 involves engineering the crystal facets in a way that speci c types of surfaces dominate the 3D shape. The atomic structure of the surfaces and 3D morphology of the crystal determine the electronic properties of the material, and should be characterized with atomic precision. Due to its high spatial resolution (0.1 nm), aberration-corrected transmission electron microscopy was used to obtain morphological and structural information on anatase nanoplatelets and nanorods. TEM morphological analysis showed that the main 3D shape of the platelets is that of a truncated tetragonal bipyramid, where f001g facets dominate. This 3D shape is accessible via 2D projections of the crystal structure. In the nanorod specimens, the types of edge morphology found link to intermediate or nal stages of growth, occurred via oriented attachment of primary nanocrystals and classical monomer addition. The structural characterization of the nanocrystals was carried out by examining the exit plane wave of the specimen, which was reconstructed from a serial acquisition of aberration-corrected TEM images of di erent defocus. The phase of the reconstructed wave reproduces the atomic potential of the specimen, and provides information with the maximum resolution of the microscope. The optical properties of the platelets and rods were also analysed using a combination of STEM imaging and EELS. Due to the high surface to volume ratio of the platelets, the EELS spectrum is dominated by strong surface features that arise from the polarization of the surface electrons induced by the electron beam. The in uence of the surface excitations on the EELS spectrum is strongly determined by the thickness of the platelets: by modifying the crystal thickness below 20 nm, the frequency of the surface excitations changes, enabling the optical properties of titania to be tuned in the visible and UV range. Finally, preliminary EELS investigations on the nanorods suggest that, unlike metallic nanoparticles, the surface excitations are not in uenced by the morphology of the crystal, but strongly depend on its thickness.
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Martín, Malpartida Gemma. "Combined Transmission Electron Microscopy and In-Situ Scanning Tunneling Microscopy Characterization of Nanomaterials." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663184.
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The main goal of this thesis has been to apply in-situ Transmission Electron Microscopy (TEM) electrical measurements using a Scanning Tunneling Microscopy (STM) tip, combined with TEM imaging and spectroscopic techniques, in order to address the characterization of relevant nanomaterials. This system has not only been used to measure electrical properties, but also to carry out in-situ experiments with Joule heating and to apply mechanical stresses.
A review of the different in-situ TEM techniques, their development over the years and their impact in the scientific community has been presented. Moreover, the instrumental used in this thesis, in particular, the TEM-STM system, has been described. In addition, two techniques for the preparation of specific samples for in-situ TEM-STM experiments have been presented: for nanostructured samples (2D materials, nanowires, etc), and for localized samples (devices, thin layers, bulk samples, etc). A gridcase that allows the use of conventional TEM grids in the TEM-STM system has been designed and fabricated in the context of this thesis. The use of this homemade gridase has allowed us to improve the experiments, offering more reproducibility and versatility. Finally, the calibration of the electrical measurements of the system has been carried out.
Using the TEM-STM system, different type of nanostructures have been characterized during the present thesis, from 2D nanostructures, as the elucidation of the effects of electrical current through a single graphene oxide sheet, to functional devices, as the study of the ferroelectric and piezoelectric behavior of structures based on La2WO6, the study of the anisotropic electrical conductivity of GaInP CuPtB type ordering layers used for multijunction solar cells or the study of the conductive filament (CF) formation mechanism in three different Resistive random-access memory (ReRAM) devices.
In summary, in-situ microscopy expands the horizons of the characterization and study of materials and, in particular, in the context of this thesis, an in-situ TEM-STM system has been used to electrically characterize samples from nanomaterials to functional devices.En aquesta Tesi, s'ha emprat una tècnica de Microscopia Electrònica de Transmissió (TEM, Transmission Electron Microscopy en anglès) in-situ que permet realitzar mesures elèctriques utilitzant una sonda de microscòpia d'efecte túnel (STM, Scanning Tunneling Microscopy en anglès), tot combinant-la amb imatge TEM i tècniques d'espectroscòpia. A més, aquest sistema no només s'ha utilitzat per a mesurar les propietats elèctriques, sinó també per a dur a terme experiments in-situ amb escalfament per efecte Joule o aplicant una tensió mecànica a la superfície de la mostra. D'aquesta manera s'han pogut caracteritzar nanomaterials, des de nanoestructures 2D, estudiant l’efecte del pas de corrent a través d'un sol full d'òxid de grafè, fins a dispositius completament funcionals, com la caracterització piezoelèctrica i ferroelèctrica de capes primes d'òxids funcionals lliures de plom, l'estudi de l’anisotropia en la conductivitat d’estructures ternàries III-V ordenades utilitzades en cèl·lules solars tàndem multicapa i l'estudi amb TEM de la formació de filaments conductors (CF) i del mecanisme de commutació resistiva en tres dispositius ReRAM diferents. En els diferents capítols d'aquesta tesi s'ha donat resposta a problemes de ciència de materials amb l'ajut d'una tècnica de TEM in-situ tot combinant-la amb altres tècniques d'espectroscòpia i difracció. El desenvolupament d'aquesta tècnica ha permès caracteritzar les propietats del materials a nivell nano.
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Pierce, William Renton. "High-resolution transmission electron microscopy and electron energy loss spectroscopy of doped nanocarbons." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/highresolution-transmission-electron-microscopy-and-electron-energy-loss-spectroscopy-of-doped-nanocarbons(dd1340ba-4a31-49e5-a421-9dd47ea35256).html.
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Graphene, a one-atom thick sheet of carbon, is the thinnest, strongest and most electrically conductive material ever discovered. Alongside carbon nanotubes it is part of the group of nanocarbons whose unique properties have sparked huge interest in possible applications, including electronic devices, solar cells and biosensors. Doping of these materials allows for the modification of their optical and electronic properties,which is crucial to realising these applications. Studying the properties of these doped materials at atomic resolution and finding controllable and industrially scalable routes to doping, such as low energy ion implantation, are thus essential if they are to becomethe materials of the future. In this thesis, highly localised optical enhancements in metal doped graphene are studied using energy-filtered transmission electron microscopy in a monochromated and aberration corrected electron microscope. The ideal conditions for imaging the low energy loss region of graphene using EFTEM are discussed and new methods to compensate for image artifacts when using this technique at high resolution are presented. Density functional theory is used to reveal new visible spectrum plasmon excitations in the electron energy loss spectra of boron and nitrogen doped nanocarbons. Atomic resolution scanning transmission electron microscopy and nanoscale electron energy loss spectroscopy are used to investigate controllable and defect-free substitutional doping of suspended graphene films through low energy ion implantation. Computational methods for filtering high angle annular dark field images are shown and software for the automated processing and spectroscopic analysis of these images is developed.
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Tanaka, N., H. Iwai, K. Kakushima, E. Okunishi, J. Yamasaki, and S. Inamoto. "Annealing effects on a high-k lanthanum oxide film on Si (001) analyzed by aberration-corrected transmission electron microscopy/scanning transmission electron microscopy and electron energy loss spectroscopy." American Institute of Physics, 2010. http://hdl.handle.net/2237/14189.
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Roventa, Elena. "Transmission electron microscopy investigations of the CdSe based quantum structures." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=982375115.
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Turnbull, Susan B. "Characterisation of focused ion beam nanostructures by transmission electron microscopy." Thesis, University of Glasgow, 2009. http://theses.gla.ac.uk/572/.
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Ion irradiation is an effective tool for the modifcation and control of the properties of magnetic thin films. Basic magnetic properties such as coercivity and local anisotropy direction can be altered in NiFe (Permalloy) films, whilst for Co/Pd multilayers, ion irradiation results in a transition from perpendicular to in-plane magnetisation. This ability to tailor magnetic properties in a controlled manner can be used as a tool for nanoscale patterning. Results are presented from investigations into the effect of Ga+ ion dose on the magnetic and structural properties of permalloy thin film systems. Systems consisting of a permalloy layer of either 10nm or 20nm, and one or more non-magnetic layers of Al or Au were deposited by thermal evaporation and irradiated in a focused ion beam (FIB) with a 30kV Ga ion source. The presence of the non-magnetic layers allows irradiation induced mixing with the magnetic layer, effectively creating alloyed regions with different properties to the rest of the film. At low ion doses, no signifcant effect on either the magnetic or structural properties were observed. Bright field TEM images of the irradiated regions revealed that increasing the dose to 1x10^15 ions/cm^2 and above caused an increase in mean grain size from ~5nm to ~30nm. The Fresnel mode of Lorentz microscopy revealed that a reduction in the mean moment was also observed at these doses but no clear changes in coercivity or magnetisation reversal behaviour were observed until the systems were rendered non-magnetic. This occurred at 1x10^16 and 3x10^16 ions/cm^2 for systems with 10nm NiFe and 20nm NiFe respectively. Milling of the samples was evident at these high doses, meaning that it was not possible to magnetically pattern these systems without occasioning a change of 2nm and 6nm respectively in the thickness of the samples. Based on the above, structures were created to control the location of magnetic domain walls (DW). Lines were written by FIB in simple elements with dimensions <1micron, the aim being to create a higher density of DW than could be realised in equivalent homogeneous elements. Structures containing high DW densities are attractive for measuring domain wall magnetoresistive effects and have potential application in DW-based storage or logic devices. One geometry of interest is an element with `zigzag' edges. Results are be presented in chapter 4 showing how these can support either quasi-uniform magnetisation or multi-domain structures separated by DW with spacing <100nm. In chapter 5 irradiation of magnetic structures was again carried out, but this time in magnetic wires to create defect or pinning sites. Domain wall traps fabricated by ion irradiation were characterised, and irradiation line defects introduced along the wire. The lines were patterned at 90± and 45± to the length of the wire, and successfully pinned the domain walls at predefned locations. A 90 degree line irradiated at a dose of 1x10^15 ions/cm^2 was not able to provide a strong enough pinning site for a domain wall. However, when the angle of the line was changed to ±45 degrees it was possible to reproducibly pin domain walls at these sites. A relationship between the orientation of the irradiated line and the chirality of the domain wall that pinned at the site was observed. The effcts of irradiation on Co/Pd multilayers with perpendicular magnetic anisotropy was investigated in chapter 6. Irradiation causes magnetic systems with perpendicular magnetisation to undergo a transition from out-of-plane magnetisation to in-plane. A grid pattern was devised so that magnetic states with both in-plane and out-of-plane magnetisation could be observed. A combination of differential phase contrast microscopy and simulations of integrated magnetic induction were used to determine the orientation of magnetisation within the lines.
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Johnston, Alan Biggar. "Investigation of magnetic microstructures using novel transmission electron microscopy techniques." Thesis, University of Glasgow, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294166.
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Moulding, Keith M. "Transmission electron microscopy of nonlinear optical glasses and optical fibres." Thesis, University of Essex, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279411.
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Hawkridge, Michael Edward. "Transmission electron microscopy of threading dislocations in gallium nitride epilayers." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435731.
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