Дисертації: "Transmission electron"

1

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).

2

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 Ã‚Â• 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.

3

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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4

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.

5

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.

6

Agarwal, Akshay. "A nanofabricated amplitude-division electron interferometer in a transmission electron microscope." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107101.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.
"September 2016." Cataloged from PDF version of thesis.
Includes bibliographical references (pages 56-62).
Wavefront-division electron interferometry with the electron biprism has enabled many applications such as electron holography, exit-wave reconstruction, and demonstration of the Aharonov-Bohm effect. However, wavefront-division interferometry is limited by the requirement of high source coherence. Amplitude-division electron interferometers, first demonstrated by Marton and co-workers in 1954, can overcome this limitation. The implementation of these interferometers is hindered by the precise rotational and translational alignment required. This thesis develops a self-aligned, monolithic electron interferometer consisting of two 45 nm thick silicon layers separated by 20 gm and fabricated from a single crystal silicon cantilever on a transmission electron microscope grid by gallium focused ion-beam milling. Using this interferometer, beam path-separation and interference fringes of lattice periodicity and a maximum contrast of 15% in an unmodified 200 kV transmission electron microscope was demonstrated. This interferometer design can potentially be scaled to millimeter-scale and used in electron holography. It can also be applied to perform fundamental physics experiments such as interaction-free measurement with electrons, with the aim of significantly reducing the damage suffered by biological samples during high-resolution microscopy. Thus, the interferometer can serve as a proof-of-concept of the recently proposed 'Quantum Electron Microscope'.
by Akshay Agarwal.
S.M.

7

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.

8

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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9

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.

10

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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11

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.

12

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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13

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.

14

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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15

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 temps
This 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

16

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.

17

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.

18

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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19

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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20

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

21

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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22

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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23

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 T_C. 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 T_C, 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 T_C, augmenting electronic transport and enhancing the magnitude of resistivity jump at T_C, 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.

24

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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25

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).

26

McLaren, Mathew Jonathon. "Transmission electron microscope characterisation of iron-rhodium epilayers." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/8281/.

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Iron-rhodium (FeRh) alloys exhibit an unusual magnetostructural transition, making them a fascinating topic of research. When the alloy is approximately equiatomic (Fe48Rh52 to Fe56Rh44) it is in a caesium chloride (CsCl) structure. At room temperature it is antiferromagnetic (AFM), making a first-order phase transition to a ferromagnetic (FM) state when heated above ~350K. There is also a 1% increase in unit lattice volume upon heating to the FM phase, as well as an increase in entropy and decrease in resistivity. The transition can be modified by doping, applied strain and applied magnetic field among other methods. Thin film FeRh has potential uses as part of a spin valve system for magnetic data storage and as a suitable choice for a memristor. The work presented here demonstrates the methods approached to preparing a variety of sputter-deposited thin film FeRh samples for characterisation in a transmission electron microscope (TEM) as well as by techniques such as X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). These include samples capped with epitaxial chromium (Cr) and tungsten (W) to raise and lower the transition temperature respectively. After cross-section or plan-view preparation using either a conventional ion polishing method or a focused ion beam, the samples were characterised using a variety of methods in the TEM. Initial characterisation has examined the crystal structure, layer thickness and interfacial roughness of these films, confirming results from bulk X-ray measurements. It has been found that FIB-prepared samples do not exhibit the phase transition whereas ion polished samples are unaffected. Compositional analysis of the interface FeRh makes with a magnesium oxide (MgO) substrate finds a change in iron-to-rhodium ratio while characterising the FeRh/cap interface finds significant Fe diffusion into Cr-capped samples with no interdiffusion seen in identical W-capped FeRh films. Analysis of the transition dynamics observing changes in strain and ferromagnetic domains via heating experiments have confirmed the nucleation and growth of the phase change at the interfaces. Finally, there is some evidence to suggest that a martensitic change is occurring in FeRh through the transition. The presence of twins in the FeRh as well as extra ordering spots in a FIB-prepared cross-section allude to a more complex transition than previously thought.

27

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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28

Gass, Mhairi Hope. "Low-loss electron energy loss spectroscopy in a scanning transmission electron microscope of GaInNAs." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415656.

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29

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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30

Ryll, Henning [Verfasser]. "Direct detection of electrons with the pnCCD for applications in transmission electron microscopy / Henning Ryll." Siegen : Universitätsbibliothek der Universität Siegen, 2018. http://d-nb.info/116044370X/34.

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31

Tanaka, H., T. Kojima, H. Tsuruta, J. Chen, T. Tanji, and M. Ichihashi. "Development of a Real-Time Stereo Transmission Electron Microscope." Cambridge University Press, 2005. http://hdl.handle.net/2237/10297.

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32

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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33

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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34

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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35

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.

36

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

37

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.

38

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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39

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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40

Faisal, A. Q. D. "Transmission electron diffraction studies of xenon adsorbed on graphite." Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380531.

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41

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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42

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.

43

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.

44

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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45

Vaughn, Joel M. "Manipulation Of Nanoscale Objects in the Transmission Electron Microscope." Ohio University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1191525305.

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46

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.

47

Kadifachi, Sadiq Hussein. "Electron transmission spectroscopy of some inorganic and organic molecules." Thesis, Birkbeck (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398339.

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An electron spectrometer was built in our laboratory to study the interaction of low energy ( 0.3 to 10 eV ) electrons with neutral molecules. The helium resonance at 19.3 eV was used to determine the energy resolution of the electron beam, and the 2.1 eV molecular nitrogen resonance to calibrate the energy scale of the incident electron beam. Total absolute cross sections were measured for the following molecules: molecular nitrogen, carbon monoxide, carbon dioxide, sulphur dioxide; also recorded was their electron affinity and resonant vibrational levels arising from temporary formation of negative ion states. Relative cross sections , resonant vibrational structures and electron affinities were determined for the following molecules: benzene, furan, pyrrole; ethylene, propene, butene, pentene, hexene; cyclopentene, cyclohexene, cycloheptene, cyclooctene. Comparison between these measurements and the most recent theoretical calculations and experimental data of other laboratories are presented. The spectrometer was modified by incorporating a manometer for the purpose of making accurate pressure measurements inside the collision chamber and interfaced with a new computer containing the appropriate software to calculate the electron cross section of molecules in the gas phase. Also measured, for the first time in our laboratory, the absolute total electron cross sections of N2, CO, CO2 and SO2, the latter never having been measured before anywhere. The electron beam resolution was improved by incorporating into the spectrometer an additional 1270 momentum cylindrical selector in tandem with the existing monochromator but having separate controls. The previously published results of C6H6, N2, C2H4, were remeasured and inaccuracies were discovered in this data. In addition, the electron affinities of a complete series of related compounds-: linear and cyclic alkenes - were measuredf or the first time and to the best of the author's knowledge the results are original and do not appear elsewhere.

48

Shmeliov, Aleksey. "Transmission electron imaging and diffraction characterisation of 2D nanomaterials." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:4bc4d60f-4db0-43d2-9119-cb0a0366090e.

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Following the discovery of graphene, 2D nanostructures have been noted for their potential in a range of high-impact applications, such as sensing, catalysis, and composite reinforcement. Liquid-phase exfoliation and chemical vapour deposition have been demonstrated and indicate the feasibility of mass-scale production. With the advent of mass-produced 2D nanostructures a key focus of research is to characterise these materials. This thesis is concerned with imaging and structural properties of the 2D nanomaterials, hexagonal boron nitride (h-BN), molybdenum disulfide (MoS₂), tungsten disulfide (WS₂), titanium disulfide (TiS₂) and hexabenzocoronene (HBC), produced via liquid phase exfoliation. HBC strictly speaking is not 2D nanomaterial, however, it can be viewed as transition molecule from benzene to graphene. The data used for characterisation is based primarily on electron diffraction and, in particular, aberration corrected annular dark field (ADF) scanning transmission electron microscopy (STEM). The incoherent nature of ADF STEM provides direct atomic imaging without the contrast reversals upon focus changes seen in conventional high-resolution transmission electron microscopy (HRTEM). The main structural feature investigated in this thesis was the stacking sequences in few-layers h-BN, MoS₂, WS₂ and TiS₂. Simple stacking (AAA) can be distinguished from Bernal (ABA) and rhombohedral (ABC) on the basis of intensity ratio, I_{10̅10}/I_{11̅20} , in diffraction patterns and indirectly in HRTEM images. Nonetheless acquisition of the diffraction patterns suitable for analysis can be challenging due to the sample issues. Non-bulk stacking sequences were reliably confirmed for all above 2D nanomaterials on the basis of atomically resolved ADF STEM. 20 h-BN, 28 MoS₂, 5 WS₂ and 6 TiS₂ nanoflakes were imaged and analysed. Amongst them 2 h-BN, 9 MoS2, 4 WS2 and 1 TiS2 nanoflakes displayed non-bulk stacking. Hence, it appears that 2D WS2 has the greatest affinity for non-bulk stacking. Finally, an interesting structural transformation was observed in HBC molecules. Under the influence of electron beam HBC agglomerates were transformed into crystalline phase with 90^o symmetry.

49

Sharp, Joanne. "Electron tomography of defects." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/228638.

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Tomography of crystal defects in the electron microscope was first attempted in 2005 by the author and colleagues. This thesis further develops the technique, using a variety of samples and methods. Use of a more optimised, commercial tomographic reconstruction program on the original GaN weak beam dark-field (WBDF) tilt series gave a finer reconstruction with lower background, line width 10-20 nm. Four WBDF tilt series were obtained of a microcrack surrounded by dislocations in a sample of indented silicon, tilt axes parallel to g = 220, 220, 400 and 040. Moiré fringes in the defect impaired alignment and reconstruction. The effect on reconstruction of moiré fringe motion with tilt was simulated, resulting in an array of rods, not a flat plane. Dislocations in a TiAl alloy were reconstructed from WBDF images with no thickness contours, giving an exceptionally clear reconstruction. The effect of misalignment of the tilt axis with systematic row g(ng) was assessed by simulating tilt series with diffraction condition variation across the tilt range of Δn = 0, 1 and 2. Misalignment changed the inclination of the reconstructed dislocation with the foil surfaces, and elongated the reconstruction in the foil normal direction; this may explain elongation additional to the missing wedge effect in experiments. Tomography from annular dark-field (ADF) STEM dislocation images was also attempted. A tilt series was obtained from the GaN sample; the reconstructed dislocations had a core of bright intensity of comparable width to WBDF reconstructions, with a surrounding region of low intensity to 60 nm width. An ADF STEM reconstruction was obtained from the Si sample at the same microcrack as for WBDF; here automatic specimen drift correction in tomography acquisition software succeeded, a significant improvement. The microcrack surfaces in Si reconstructed as faint planes and dislocations were recovered as less fragmented lines than from the WBDF reconstruction. ADF STEM tomography was also carried out on the TiAl sample, using a detector inner angle (βin) that included the first order Bragg spots (in other series βin had been 4-6θ B). Extinctions occurred which were dependent on tilt; this produced only weak lines in the reconstruction. Bragg scattering in the ADF STEM image was estimated by summing simulated dark-field dislocation images from all Bragg beams at a zone axis; a double line was produced. It was hypothised that choosing the inner detector angle to omit these first Bragg peaks may preclude most dynamical image features. Additional thermal diffuse scattering (TDS) intensity due to dilatation around an edge dislocation was estimated and found to be insignificant. The Huang scattering cross section was estimated and found to be 9Å, ten times thinner than experimental ADF STEM dislocation images. The remaining intensity may be from changes to TDS from Bloch wave transitions at the dislocation; assessing this as a function of tilt is for further work. On simple assessment, only three possible axial channeling orientations were found over the tilt range for GaN; if this is typical, dechanneling contrast probably does not apply to defect tomography.

50

Muto, S., K. Tatsumi, K. Ikeda, and S. Orimo. "Dehydriding process of alpha-AlH3 observed by transmission electron microscopy and electron energy-loss spectroscopy." American Institite of Physics, 2009. http://hdl.handle.net/2237/12636.

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