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Artykuły w czasopismach na temat "Atomic-resolution TEM"
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Bell, David C., Christopher J. Russo i Dmitry V. Kolmykov. "40keV atomic resolution TEM". Ultramicroscopy 114 (marzec 2012): 31–37. http://dx.doi.org/10.1016/j.ultramic.2011.12.001.
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Yagi, K., H. Sato, K. Kobayashi, Y. Nishiyama i Y. Tanaka. "TEM study of Si surfaces". Proceedings, annual meeting, Electron Microscopy Society of America 50, nr 1 (sierpień 1992): 280–81. http://dx.doi.org/10.1017/s0424820100121806.
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UHV TEM studies of surfaces have been successfully applied in surface science. Low resolution TEM can characterize surface atomic steps, monolayer adsorbate, reconstruction of surfaces and surface structure domains. TED from surfaces of thin films can be used to analyze surface atomic structure. On the other hand high resolution TEM can seen atomic structure of surfaces either in profile or in plan view modes. The profile mode is effective for surfaces with short periods along the beam direction and is sensitive to displacements of surface atoms normal to the surface and along a direction parallel to the surface and perpendicular to the beam direction. Image contrast of high resolution plan view images is very weak except cases of heavy adsorbed atoms on a substrate of light atoms. The present paper shortly reviews recent studies of Si surfaces done with use of a low resolution UHV TEM and high resolution TEM.
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Lee, Yangjin, Jun-Yeong Yoon, Hu Young Jeong i Kwanpyo Kim. "Atomic-Resolution TEM Imaging of Phosphorene Protected by Graphene". Microscopy and Microanalysis 25, S2 (sierpień 2019): 1696–97. http://dx.doi.org/10.1017/s1431927619009218.
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Hashimoto, Hatsujiro. "Contribution of Atomic-Level TEM to Resolution of Structure". Proceedings, annual meeting, Electron Microscopy Society of America 48, nr 1 (12.08.1990): 4–5. http://dx.doi.org/10.1017/s042482010017877x.
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Atomic Resolution Electron Microscopes are now producing useful results in many fields of science and technology. This success was obtained not only by the improvement of resolution of TEM but also through the developments of theories and experiments of diffraction crystallography, image formation and recording technique over the past 44 years. Boersch (1946-47) discussed the image of atoms and crystals by the phase object approximation; the image contrast is due to the phase shift of electron waves passing through them. Scherzer (1949) discussed the effect of the phase shift by the electron lens and proposed the phase contrast transfer function. He pointed out that the key to observe images of single atoms is by contrast enhancement, which might be possible by dark field images if resolution is improved. This proposal was attempted by improving the resolution using tilted-beam dark fields (Th atoms, Hg & Pt atoms 1971). Crystal lattice fringes were observed by Menter in 1956 who discussed the contrast by kinematical theory. The interpretation of lattice images by dynamical theories were carried out by Hashimoto et al. (Bethe theory) and Cowley (Multi-slice theory) in 1958-60 and noted the correct position of atoms is in neither black fringe regions nor white ones when the images are taken in the Bragg reflecting position. However Miyake et al in 1964, showed that black or white contrast peaks appear at atom positions if the crystal is in symmetry position. Two dimensional lattice structure images were first photographed in 1970-71, which stimulated strongly the application of electron microscopy to materials science, crystallography and engineering at many laboratories such as the National Center at Berkeley. For the identification of correct position of atoms, two types of image contrast calculation have been proposed (e.g. multi-slice 1972, Bethe method 1975). The partially coherent theory originally developed in optics was introduced into the contrast calculation in 1979-80. Around this time, many observations of defect structures have been carried out, some of which are shown in Table 1. In situ observation of moving atoms and atom columns in molecules and crystals have been carried out in 1978 by using a TV system, which enable us to see the transition phenomena with a speed of 1/30 or 1/60 seconds. More recently atomic imaging at 1.8 A-1.6 A played an important role in the structure research of new materials and phenomena such as superconducting materials (metallic A15, 1989, ceramic high Tc, 1988), metal ceramic interface (Nb/Al2O3 1984), superstructure (GaAs/AlAs/GaAs 1985) quasi crystals (1987) etc. Many subsequent observations are presented in this congress. In spite of these developments, there are still some problems to be solved, e.g. imaging of atoms in the correct positions and the identification of different kinds of atoms in the materials especially with unknown crystal structure.
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Cochrane, Heather D., John L. Hutchison i Donald White. "Surface studies of catalytic ceria using atomic-resolution tem". Ultramicroscopy 31, nr 1 (wrzesień 1989): 138–42. http://dx.doi.org/10.1016/0304-3991(89)90044-2.
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Krakow, William, David P. Divincenzo, Peter A. Bancel, Eric Cockayne i Veit Elser. "High-resolution TEM of Al-Cu-Fe quasicrystals". Proceedings, annual meeting, Electron Microscopy Society of America 50, nr 1 (sierpień 1992): 118–19. http://dx.doi.org/10.1017/s0424820100120990.
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High resolution electron microscopy and electron diffraction have always been key tools for the study of quasicrystals. The unique features of quasicrystals arc their long range oricntational order despite the absence of periodic translational order, and their non-crystallographic symmetry. The early work in electron microscopy and diffraction assessed the degree of perfection of these materials; microdo-mains with slightly different orientations, phason strains and dislocations were found which masked the fundamental atomic structure. A defect free material was sought to deduce the atomic arrangement of these materials and this was found in Al-Cu-Fe. Preliminary examinations of these materials using 20 at.% Cu and 15 at.% Fe indicated they are almost entirely free of phason strains when viewed in a 200kV microscope.At the time of these investigations the microscopes employed were limited in resolution and thus provide limited information about the atomic arrangements of these quasicrystals. Recently, studies were made using a more powerful microscope operating at 400kV where the point resolution is improved to 1.7Å. In that case, a Al-Mn-Si specimen was viewed along the five-fold axis under apparent optimum imaging conditions. These prior studies have interpreted various image features as being due to dynamical scattering processes and therefore little about the atomic arrangement of the quasicrystal is obtained. Our interpretation of the image feature is different and is due to modification of the phase contrast transfer function. Here clarification is given of the information contained in high resolution micrographs of quasicrystals.
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Zhang, Xiao Feng, i Takeo Kamino. "Imaging Gas-Solid Interactions in an Atomic Resolution Environmental TEM". Microscopy Today 14, nr 5 (wrzesień 2006): 16–19. http://dx.doi.org/10.1017/s1551929500058600.
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It is well known that analysis using transmission electron microscopes (TEM) yields very high resolution images of thin specimens. However, the applicability of TEM analysis is not universal due to the requirement that a high internal vacuum is required. This high vacuum precludes the TEM study of living specimens or specimens in a gas or liquid environment. In order to tackle this problem, L. Marton of Universite Libre in Brussels, Belgium was the first to design an environmental cell (E-cell) in 1935 that was sealed in the tip of a TEMsample holder [1]. Marton's design included two 0.5 μm aluminum foils as upper and lower windows sandwiching a biological sample to sustain a living environment. The electron transparent windows permitted the confined biological objects to be imaged in TEMmode. Since then, environmental TEM (E-TEM) has received increasing attention from biological scientists and eventually from materials scientists as well.
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Kujawa, S., B. Freitag i D. Hubert. "An Aberration Corrected (S)TEM Microscope for Nanoresearch". Microscopy Today 13, nr 4 (lipiec 2005): 16–21. http://dx.doi.org/10.1017/s1551929500053608.
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The continued focus on improving materials, combined with the fact that it is now commonly understood that material properties are affected by characteristics at the atomic level, give rise to the need to characterize and image at the best resolutions possible. The (Scanning) Transmission Electron Microscope ((S)TEM) has the capability to image structures with atomic resolution and provides, at the same time, information on the chemical composition, bonding and electronic structure of the material. The nanoresearcher's continued need for the ultimate resolution has accelerated the development of next generation electron optics and technology.
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Zhang, Xiao Feng. "Enabling Lab-in-Gap Transmission Electron Microscopy at Atomic Resolution". Microscopy Today 24, nr 1 (styczeń 2016): 24–29. http://dx.doi.org/10.1017/s1551929515000930.
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Abstract: Hitachi Lab-in-Gap transmission electron microscopy (TEM) technologies are introduced. The term Lab-in-Gap refers to a special function that allows in situ and in operando TEM studies of materials in gas or liquid environments while stimulations, such as thermal or electrical fields, are applied to the specimen sitting in the pole piece gap in a TEM system. Physical or chemical process can be activated and imaged in real time using TEM or other imaging modes. The new generation environmental TEM platform with large pole piece gap and advanced aberration correctors opens wide possibilities for integrating multiple stimuli sources as well as large-area, sub-Å resolution live imaging for dynamic structural changes.
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Hasegawa, Tsuyoshi, Kunio Kobayashi, Nobuyuki Ikarashi, Kunio Takayanagi i Katsumichi Yagi. "Atomic Resolution TEM Images of the Au(001) Reconstructed Surface". Japanese Journal of Applied Physics 25, Part 2, No. 5 (20.05.1986): L366—L368. http://dx.doi.org/10.1143/jjap.25.l366.
Pełny tekst źródłaRozprawy doktorskie na temat "Atomic-resolution TEM"
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Cochrane, Heather Dunlop. "Surface studies of catalytic cerias using atomic resolution TEM". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276508.
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He, Kuang. "Synthesis and atomic resolution AC-TEM characterisation of graphene edges". Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:32b4ea72-5a60-4c1f-9d93-9d9fe1cc4382.
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My primary goal was to perform an in depth characterisation of the atomic structure of graphene edges, which was fulfilled through the use of an aberration corrected transmission electron microscope (AC-TEM) - OJ2200 MCO that was enhanced with a double Wien slit monochromator to improve its spatial resolution to ~ 80pm. The chemical vapour deposition grown graphene was characterised by various techniques, including the use of Scanning Electron Microscopy (SEM) and Raman spectroscopy to respectively determine the homogeneity and number of layers, and selected area electron diffraction (SAED) to distinguish the size of single crystal region. With this set up, I obtained images of graphene edges at atomic resolution that allowed bond length determination. Based on the acquired information and the application of the density functional theory, it was possible to correlate structural information with the bonding nature of graphene edges; allowing me to further determine the hydrogenation states of graphene with a single AC-TEM frame. Imaging with electron beam monochromation also allowed me to discover the theoretically predicted extended Klein edge structure, which is included as the fourth inherent periodic structure of graphene edges. With the aid of an in situ heating holder, the temperature dependence of graphene edges were investigated over 350 frames: zig-zag edges are found to dominate at = 400°C; and at temperatures above 600°C, the proportion of armchair and reconstructed 5-7 edges increase dramatically. This is because low temperatures allow contamination, which result in edges becoming etched at a more rapid rate that favours the formation of intrinsic zig-zag edges. The predominance of armchair and reconstructed zig-zag edges at high temperatures could be attributed to the evaporation of surface adsorbates, which resulted from higher thermodynamic stability. Finally, the in situ growth of a second layer graphene was investigated. Extra layers of graphene was found to heterogeneously nucleate around gold nanoparticles and continuous to grow at 600°C. This study shed light on the growth mechanism of CVD. By bridging the dangling bonds from the edges of two layers of graphene, this structure was extended to form a closed edge graphene nanopore with diameter ranging from 1.4-7.4 nm, The closed edge nanopores in bilayer graphene are robust to back-filling even after exposure to atmospheric conditions for days - this opens new possibilities of nanopore fabrication routes for applications such as graphene sensors and DNA sequencing technology.
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Li, Siqian. "The atomic struture of inversion domains and grain boundaries in wurtzite semonconductors : an investigation by atomistic modelling and high resolution transmission electron microscopy". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC252/document.
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Au cours de ce travail, nous avons étudié deux types de défauts interfaciaux: domaines d’inversion (DI) et joints de grains (JG) dans des semiconducteurs de structure wurtzite (nitrures- d’éléments III, ZnO et l’hétérostructure ZnO/GaN) en utilisant le MET haute résolution et la modélisation ab initio. Dans le cas des DI, nos analyses théoriques montrent qu'une configuration tête-à-tête avec une séquence d'empilement à l’interface AaBbAa-AcCaA (H4) est la structure la plus stable dans les composés binaires (nitrures et ZnO wurtzites). De plus, un gaz d’électrons (2DEG) ou de trous (2DHG) à 2 dimensions est formé pour les configurations « tête-à-tête » ou queue-à-queue. A l’interface ZnO/GaN, l'observation de MET très haute résolution a confirmé la configuration H4 avec une interface -Zn-O-Ga-N. Notre modélisation théorique a mis en évidence la formation d’un gas de trous à 2 dimensions à cette hétérointerface. Nous avons aussi réalisé l’étude topologique, théorique et par MET des joints de grains de rotation autour de l’axe [0001] dans ces matériaux. Dans le GaN, nous avons trouvé que les plans du joint sont simplement formés par des dislocations de type a déjà connues pour le matériau en couche mince. Par contre, dans ZnO, la théorie topologique est complétement démontrée, et la dislocation [101 ̅0] est une brique de base dans la constitution des joints de grains avec des cycles d’atomes 6-8-4-In this work, we investigated two kinds of interfacial defects: inversion domain boundaries (IDBs) and grain boundaries (GB) in wurtzite semiconductors (III-nitrides, ZnO and ZnO/GaN heterostructure) using high-resolution TEM and first-principle calculations. For IDBs, theoretical calculation indicated that a head-to-head IDB with an interfacial stacking sequence of AaBbAa-AcCaA (H4) is the most stable structure in wurtzite compounds. Moreover, 2-dimensional electron gas (2DEG) and 2-dimensional hole gas (2DHG) build up in head-to-head and tail-to-tail IDBs, respectively. Considering the IDB at the ZnO/GaN heterointerface, TEM observations unveiled the H4 configuration with a -Zn-O-Ga-N interface. Moreover the theoretical investigation also confirmed stability of this interface along with the corresponding formation of a 2DHG. A detailed topological, TEM and theoretical investigation of [0001] tilt Grain Boundaries (GBs) in wurtzite symmetry has also been carried out. In GaN, it is shown that the GBs are only made of separated a edge dislocations with 4, 5/7 and 8 atoms rings. For ZnO, a new structural unit: the [101 ̅0] edge dislocation made of connected 6-8-4-atom rings is reported for the first time, in agreement with an early theoretical report on dislocations and jogs in the wurtzite symmetry
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Bacia, Maria. "Comportement du carbone aux joints de grains du molybdène". Grenoble INPG, 1994. http://www.theses.fr/1994INPG4210.
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La mise en evidence et l'interpretation du role benefique du carbone et du role nefaste de l'oxygene sur la cohesion intergranulaire du molybdene en l'absence de precipitation visible au meb constituaient le but de cette etude. Une methode efficace de purification du molybdene a ete mise au point. Les mesures de la concentration intergranulaire de carbone en fonction de la temperature de carburation et de la teneur volumique ont ete effectuees a l'aide d'un spectrometre auger. Un modele d'enrichissement des joints de grains au cours du refroidissement a ete propose. Les structures des joints purs et contenant des atomes de solute ont ete determinees par des simulations statiques a l'aide de potentiels a n corps calcules en se fondant sur la methode de l'atome immerge (eam). La comparaison des segregations intergranulaires d'oxygene et de carbone (sites de segregation, sequence d'occupation des sites, enthalpies de melange) a ete effectuee pour le cas du joint symetrique de flexion 37 autour de l'axe 100. Les structures atomiques du joint 37 a l'etat pur et a l'etat carbure ont ete observees au microscope electronique a haute resolution. Apres la carburation ne conduisant pas a la formation de precipites mo#2c visibles au meb, la presence d'une phase bidimensionnelle moc#x (x 0,4) formant un film continu au joint a ete mise en evidence. Elle peut etre rendue responsable du renforcement du joint. Sa faible largeur ( 10 a) et son accommodation parfaite aux reseaux cristallographiques des deux grains rendent son observation impossible par des methodes classiques (meb, met), ce qui explique que son existence etait jusqu'a maintenant ignoree. Il n'est pas exclu qu'il s'agisse de la premiere observation d'un etat intermediaire entre la segregation et un compose tridimensionnel discontinu
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Sun, Xingsheng. "A Computational Framework for Long-Term Atomistic Analysis of Solute Diffusion in Nanomaterials". Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/85242.
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Diffusive Molecular Dynamics (DMD) is a class of recently developed computational methods for the simulation of long-term mass transport with a full atomic fidelity. Its basic idea is to couple a discrete kinetic model for the evolution of mass transport process with a non-equilibrium thermodynamics model that governs lattice deformation and supplies the requisite driving forces for kinetics. Compared to previous atomistic models, e.g., accelerated Molecular Dynamics and on-the-fly kinetic Monte Carlo, DMD allows the use of larger time-step sizes and hence has a larger simulation time window for mass transport problems. This dissertation focuses on the development, assessment and application of a DMD computational framework for the long-term, three-dimensional, deformation-diffusion coupled analysis of solute mass transport in nanomaterials. First, a computational framework is presented, which consists mainly of: (1) a computational model for interstitial solute diffusion, which couples a nonlinear optimization problem with a first-order nonlinear ordinary differential equation; (2) two numerical methods, i.e., mean field approximation and subcycling time integration, for accelerating DMD simulations; and (3) a high-performance computational solver, which is parallelized based on Message Passing Interface (MPI) and the PETSc/TAO library for large-scale simulations. Next, the computational framework is validated and assessed in two groups of numerical experiments that simulate hydrogen mass transport in palladium. Specifically, the framework is validated against a classical lattice random walk model. Its capability to capture the atomic details in nanomaterials over a long diffusive time scale is also demonstrated. In these experiments, the effects of the proposed numerical methods on solution accuracy and computation time are assessed quantitatively. Finally, the computational framework is employed to investigate the long-term hydrogen absorption into palladium nanoparticles with different sizes and shapes. Several significant findings are shown, including the propagation of an atomistically sharp phase boundary, the dynamics of solute-induced lattice deformation and stacking faults, and the effect of lattice crystallinity on absorption rate. Specifically, the two-way interaction between phase boundary propagation and stacking fault dynamics is noteworthy. The effects of particle size and shape on both hydrogen absorption and lattice deformation are also discussed in detail.Ph. D.
Interstitial diffusion in crystalline solids describes a phenomenon in which the solute constituents (e.g., atoms) move from an interstitial space of the host lattice to a neighboring one that is empty. It is a dominating feature in many important engineering applications, such as metal hydrides, lithium-ion batteries and hydrogen-induced material failures. These applications involve some key problems that might take place over long time periods (e.g., longer than 1 s), while the nanoscale behaviors and mechanisms become significant. The time scale of these problems is beyond the capability of established atomistic models, e.g., accelerated Molecular Dynamics and on-the-fly kinetic Monte Carlo. To this end, this dissertation presents the development and application of a new computational framework, referred to as Diffusive Molecular Dynamics (DMD), for the simulation of long-term interstitial solute diffusion in advanced nanomaterials. The framework includes three key components. Firstly, a DMD computational model is proposed, which accounts for three-dimensional, deformation-diffusion coupled analysis of interstitial solute mass transport. Secondly, nu- merical methods are employed to accelerate the DMD simulations while maintaining a high solution accuracy. Thirdly, a high-performance computational solver is developed to implement the DMD model and the numerical methods. Moreover, regarding its application, the DMD framework is first validated and assessed in the numerical experiments pertaining to hydrogen mass transport in palladium crystals. Then, it is employed to investigate the atomic behaviors and mechanisms involved in the long-term hydrogen absorption by palladium nanoparticles with different sizes and shapes. The two-way interaction between hydrogen absorption and lattice deformation is studied in detail.
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Bansal, Ujjval. "Development of a coarsening resistant microstructure in precipitation strengthened aluminium alloys with Zr, Ta and Hf". Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5237.
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The work herein aims at developing precipitation-strengthened aluminium-copper (Al-Cu) alloys that can meet the current challenges of the aeronautical and automobile sectors to increase the fuel efficiency where operating temperatures are above 200 ℃. The present study shows the effect of micro-additions of Zr, Ta and Hf in designing the newer generation of high strength Al-Cu alloys by microstructural engineering using a three-step heat treatment route. Prior ageing (400-450 ℃) before solutionizing is effective to form L12 ordered coherent precipitates. However, discontinuous precipitation is a challenge that can be avoided by micro-additions of Si with Hf. Further, ageing at 190 ℃ resulted in a dense distribution of strengthening θ"/θ' plates, nucleated heterogeneously on these L12 ordered precipitates resulting in a significant improvement in mechanical properties. The synergistic coupling of high and low-temperature strengthening phases resulted in the slower growth of θ"/θ' plates. The higher number density of θ"/θ' plates along with L12 ordered precipitates in the α-Al matrix rationalize the observed higher yield strength in Zr, Ta and Hf modified Al-Cu alloys. The reduction in the coarsening rate of θ' plates in the modified Al-Cu alloys was observed during a long time exposure at 250 ℃. Atomic-resolution composition analysis reveals the partitioning of slow diffusing elements to the θ' plates, which delays their coarsening. It induces a high-temperature stable microstructure with 250 MPa of yield strength at 250 ℃.
Części książek na temat "Atomic-resolution TEM"
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Tochigi, Eita, Bin Miao, Shun Kondo, Naoya Shibata i Yuichi Ikuhara. "TEM Characterization of Lattice Defects Associated with Deformation and Fracture in α-Al2O3". W The Plaston Concept, 133–56. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-7715-1_7.
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AbstractAlumina (α-Al2O3) is one of the representative structural ceramics. To understand its mechanical responses, the lattice defect behavior of alumina has been investigated by transmission electron microscopy (TEM) for many years. In this report, we review our recent research progress on TEM structural analysis of lattice defects in alumina. In the first half, the core atomic structure and dissociation reaction of b = $$1/3<11\bar{2}0>$$ 1 / 3 < 11 2 ¯ 0 > , $$<1\bar{1}00>$$ < 1 1 ¯ 00 > , and $$1/3<\bar{1}101>$$ 1 / 3 < 1 ¯ 101 > dislocations formed in low-angle grain boundaries are investigated by atomic-resolution TEM observations. Based on experimental results, the slip deformation behavior associated with those dislocations is discussed. In the second half, the formation of $$1/3<11\bar{2}0>$$ 1 / 3 < 11 2 ¯ 0 > dislocations and fracture of Zr-doped ∑13 grain boundary of alumina are observed by in situ TEM nanoindentation. Furthermore, these indented samples were observed by atomic-resolution scanning TEM. The mechanisms of the deformation and fracture phenomena are discussed in detail.
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Harano, Koji, i Eiichi Nakamura. "Conformational Analysis of Organic Molecules with Single-Molecule Atomic-Resolution Real-Time Transmission Electron Microscopy (SMART-TEM) Imaging". W Molecular Technology, 339–68. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2019. http://dx.doi.org/10.1002/9783527823987.vol4_c12.
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Schmidt-Böcking, H., S. Eckart, H. J. Lüdde, G. Gruber i T. Jahnke. "The Precision Limits in a Single-Event Quantum Measurement of Electron Momentum and Position". W Molecular Beams in Physics and Chemistry, 223–45. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63963-1_12.
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AbstractA modern state-of-the-art “quantum measurement” [The term “quantum measurement” as used here implies that parameters of atomic particles are measured that emerge from a single scattering process of quantum particles.] of momentum and position of a single electron at a given time [“at a given time” means directly after the scattering process. (It should be noticed that the duration of the reaction process is typically extremely short => attoseconds).] and the precision limits for their experimental determination are discussed from an experimentalists point of view. We show—by giving examples of actually performed experiments—that in a single reaction between quantum particles at a given time only the momenta of the emitted particles but not their positions can be measured with sub-atomic resolution. This fundamental disparity between the conjugate variables of momentum and position is due to the fact that during a single-event measurement only the total momentum but not position is conserved as function of time. We highlight, that (other than prevalently perceived) Heisenberg’s “Uncertainty Relation” UR [1] does not limit the achievable resolution of momentum in a single-event measurement. Thus, Heisenberg’s statement that in a single-event measurement only either the position or the momentum (velocity) of a quantum particle can be measured with high precision contradicts a real experiment. The UR states only a correlation between the mean statistical fluctuations of a large number of repeated single-event measurements of two conjugate variables. A detailed discussion of the real measurement process and its precision with respect to momentum and position is presented.
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Krishnan, Kannan M. "Transmission and Analytical Electron Microscopy". W Principles of Materials Characterization and Metrology, 552–692. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198830252.003.0009.
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Transmission electron microscopy provides information on all aspects of the microstructure — structural, atomic, chemical, electronic, magnetic, etc. — at the highest spatial resolution in physical and biological materials, with applications ranging from fundamental studies to process metrology in the semiconductor industry. Developments in correcting electron-optical aberrations have improved TEM resolution to sub-Å levels. Coherent Bragg scattering (diffraction), incoherent Rutherford scattering (atomic mass), and interference (phase) are some contrast mechanisms in TEM. For phase contrast, optimum imaging is observed at the Scherzer defocus. Magnetic domains are imaged in Fresnel, Foucault, or differential phase contrast (DPC) modes. Off-axis electron holography measures phase shifts of the electron wave, and is affected by magnetic and electrostatic fields of the specimen. In scanning-transmission (STEM) mode, a focused electron beam is scanned across the specimen to sequentially form an image; a high-angle annular dark field detector gives Z-contrast images with elemental specificity and atomic resolution. Series of (S)TEM images, recorded every one or two degrees about a tilt axis, over as large a tilt-range as possible, are back-projected to reconstruct a 3D tomographic image. Inelastically scattered electrons, collected in the forward direction, form the energy-loss spectrum (EELS), and reveal the unoccupied local density of states, partitioned by site symmetry, nature of the chemical species, and the angular momentum of the final state. Energy-lost electrons are imaged by recording them, pixel-by-pixel, as a sequence of spectra (spectrum imaging), or by choosing electrons that have lost a specific energy (energy-filtered TEM). De-excitation processes (characteristic X-ray emission) are detected by energy dispersive methods, providing compositional microanalysis, including chemical maps. Overall, specimen preparation methods, even with many recent developments, including focused ion beam milling, truly limit applications of TEM.
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Ueda, O., Y. Sakuma, M. Ozeki, N. Ohtsuka i K. Nakajima. "High-Resolution TEM Evaluation of InAs/InP Strained Layer Superlattices Grown on (001)InAs Substrates by Atomic Layer Epitaxy". W Control of Semiconductor Interfaces, 531–36. Elsevier, 1994. http://dx.doi.org/10.1016/b978-0-444-81889-8.50097-3.
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Krishnan, Kannan M. "Scanning Electron Microscopy". W Principles of Materials Characterization and Metrology, 693–744. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198830252.003.0010.
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A scanning electron microscope (SEM) focuses an electron beam to a sharp probe, with its diameter, which depends on the acceleration voltage and the aberration coefficients of the probe-forming lens, determining SEM resolution. This electron beam is scanned over the specimen and signals arising from a variety of beam-specimen interactions are recorded to form images using different detectors positioned in the specimen chamber. Secondary electrons, detected with the Everton-Thornley detector, reveal the topography and electrical properties; back-scattered electrons provide information about the average atomic number and local crystallography of the specimen. Ferromagnetic materials alter the trajectory of secondary (Type I) and back-scattered (Type II) electrons to provide magnetic contrast. The magnetic polarization of the secondary electrons can also be analyzed directly (SEMPA) to image domains. The electron beam also excites characteristic X-rays for chemical microanalysis. Luminescent specimens produce light (Cathodoluminescence); these photons provide information on the electronic structure, particularly the defect states, of the specimen. Environmental SEMs, with differential pumping, image the specimen in a gaseous environment and/or under hydration for biological materials. A SEM combined with a focused ion beam (FIB) column is used for nano-fabrication, including preparation of electron-transparent TEM specimens.
Streszczenia konferencji na temat "Atomic-resolution TEM"
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Hubbard, William A., Ho Leung Chan i B. C. Regan. "High-Resolution Conductivity Mapping with STEM EBIC". W ISTFA 2022. ASM International, 2022. http://dx.doi.org/10.31399/asm.cp.istfa2022p0251.
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Abstract Modern electronic systems rely on components with nanometer-scale feature sizes in which failure can be initiated by atomic-scale electronic defects. These defects can precipitate dramatic structural changes at much larger length scales, entirely obscuring the origin of such an event. The transmission electron microscope (TEM) is among the few imaging systems for which atomic-resolution imaging is easily accessible, making it a workhorse tool for performing failure analysis on nanoscale systems. When equipped with spectroscopic attachments TEM excels at determining a sample’s structure and composition, but the physical manifestation of defects can often be extremely subtle compared to their effect on electronic structure. Scanning TEM electron beam-induced current (STEM EBIC) imaging generates contrast directly related to electronic structure as a complement the physical information provided by standard TEM techniques. Recent STEM EBIC advances have enabled access to a variety of new types of electronic and thermal contrast at high resolution, including conductivity mapping. Here we discuss the STEM EBIC conductivity contrast mechanism and demonstrate its ability to map electronic transport in both failed and pristine devices.
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Gai, Pratibha. "Atoms in action for energy, healthcare and environment using in-situ atomic resolution environmental (S)TEM". W European Microscopy Congress 2020. Royal Microscopical Society, 2021. http://dx.doi.org/10.22443/rms.emc2020.506.
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de Knoop, Ludvig. "Electric Field-Induced Surface Melting of Gold at Room Temperature visualized at Atomic Resolution Using In Situ TEM". W European Microscopy Congress 2020. Royal Microscopical Society, 2021. http://dx.doi.org/10.22443/rms.emc2020.1421.
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Nguyen, Tai D., Michael A. O'Keefe, Roar Kilaas, Ronald Gronsky i Jeffrey B. Kortright. "Effects of Fresnel Fringes on TEM Images of Interfaces in X-Ray Multilayers". W Physics of X-Ray Multilayer Structures. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/pxrayms.1992.tub2.
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Cross-sectional High-Resolution Transmission Electron Microscopy (HRTEM) has been widely used to examine the structure and morphology at multilayer interfaces at an atomic scale. Assessment of the interfacial structures quantitatively from these TEM images however is difficult due to the Fresnel fringe effects, which produce different apparent structures with defocus values in the images. These fringes result from the electrons experiencing an abrupt change in the scattering potential parallel to the electron beam path. Imaging of multilayers in cross-section, in which the electrons travel parallel to the interfaces between the two layer materials, always results in such fringes. X-ray multilayers having alternating layers of very different atomic numbers or scattering powers are more prone to these fringes than the heterostructures having less contrast layers. The visibility of the fringes increases with increasing defocus away from the minimum contrast, while optimum resolution in bright-field imaging is obtained at the Scherzer defocus, which is about 100 nm from the minimum contrast for most high resolution microscopes. Fresnel fringes are thus present when imaging at optimum defocus. The effects of these fringes have been commonly overlooked in efforts of making quantitative interpretation of interfacial profiles. They however have also been employed to characterize the structures and compositional roughness at interfaces.1-3 In this report, we present the observations of the Fresnel fringes in nanometer period Mo/Si, W/C, and WC/C multilayers in through-focus-series TEM images. Calculation of the Fresnel fringes of a Mo/Si multilayer using charge density approximation is used to illustrate the characteristics of the fringes from different interfacial structures.
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Demarest, James, i John Bruley. "Quantitative SiGe TEM Elemental Analysis in FinFET Test Structures". W ISTFA 2015. ASM International, 2015. http://dx.doi.org/10.31399/asm.cp.istfa2015p0120.
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Abstract As semiconductor device scaling continues to reduce the structure size, device geometries are also changing to three dimensional structures such as finFETs, and the materials which compose the devices are also evolving to obtain additional device performance gains. The material change studied in this paper is the introduction of silicon germanium into the electrically active region of a finFET test structure. The paper demonstrates a quantitative energy dispersive X-ray spectroscopy transmission electron microscopy (TEM) technique through the use of blanket film calibration samples of known concentration characterized by X-ray diffraction. The technique is used to identify a test structure issue which could only be diagnosed with a technique having nanometer spatial resolution and atomic percent sensitivity. The results of the test structure analysis are independently verified by the complementary TEM electron energy loss spectroscopy technique.
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Wang, Qi, L. Knight i J. Thorne. "Imaging Cross Section Of X-ray Multilayer By STM". W Physics of X-Ray Multilayer Structures. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/pxrayms.1994.wc.5.
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Cross section information is important in the study of x-ray multilayers. The traditional technique in this area is TEM. One of the limitations for TEM method is that the image is not from the surface of the sample but over an average of 10-20 nm in depth. STM, on the other hand, is a surface-sensitive technique. Comparing with TEM, STM has another advantage that STM is capable of obtaining information about the electronic structure of the materials. Like TEM, STM can also provide images with atomic lateral resolution. Potentially, STM is a very powerful tool in the study of x-ray multilayer.
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Lund, Mark W. "High reflectivity x-ray multilayers using reactive ion sputtering". W OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.tuee6.
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MOXTEK has been experimenting with reactive ion sputtering to achieve better quality multilayers. These experiments have been successful, achieving high reflectivities in the 8–60-Å region of the soft x-ray spectrum. These multilayers have been able to achieve >70% of their theoretical reflectivity. I present the results of x-ray, Auger, and atomic resolution TEM analysis of these multilayers.
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Chang, Chih-Chung, Jian-Chang Lin, Wen-Sheng Wu, Chih-Ying Tasi i Ching-Lin Chang. "A Novel Technique of Device Measurement after Cross-Sectional FIB in Failure Analysis". W ISTFA 2009. ASM International, 2009. http://dx.doi.org/10.31399/asm.cp.istfa2009p0230.
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Abstract A dual beam FIB (Focused Ion Beam) system which provides the ion beam (i-beam) and electron beam (e-beam) function are widely used in semiconductor manufacture for construction analysis and failure cause identification. Although FIB is useful for defect or structure inspection, sometimes, it is still difficult to diagnose the root cause via FIB e-beam image due to resolution limitation especially in products using nano meter scale processes. This restriction will deeply impact the FA analysts for worst site or real failure site judgment. The insufficient e-beam resolution can be overcome by advanced TEM (Transmission Electron Microscope) technology, but how can we know if this suspected failure site is a real killer or not when looking at the insufficient e-beam images inside a dual beam tool? Therefore, a novel technique of device measurement by using C-AFM (Conductive Atomic Force Microscope) or Nano-Probing system after cross-sectional (X-S) FIB inspection has been developed based on this requirement. This newly developed technology provides a good chance for the FA analysts to have a device characteristic study before TEM sample preparation. If there is any device characteristic shift by electrical measurement, the following TEM image should show a solid process abnormality with very high confidence. Oppositely, if no device characteristic shift can be measured, FIB milling is suggested to find the real fail site instead of trying TEM inspection directly.
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Vahdat, Vahid, David S. Grierson, Kevin T. Turner i Robert W. Carpick. "Nano-Scale Forces, Stresses, and Tip Geometry Evolution of Amplitude Modulation Atomic Force Microscopy Probes". W ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-48653.
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Atomic-scale wear is one of the main factors that hinders the performance of probes for atomic force microscopy (AFM) [1–6], including for the widely-used amplitude modulation (AM-AFM) mode. To conduct consistent and quantitative AM-AFM wear experiments, we have developed a protocol that involves controlling the tip-sample interaction regime, calculating the maximum contact force and normal stress over the course of the wear test, and quantifying the wear volume using high-resolution transmission electron microscopy imaging (HR-TEM). The tip-sample interaction forces are estimated from a closed-form equation that uses the Derjaguin-Mu¨ller-Toporov interaction model (DMT) accompanied by a tip radius measurement algorithm known as blind tip reconstruction. The applicability of this new protocol is demonstrated experimentally by scanning silicon probes against ultrananocrystalline diamond (UNCD) samples. The wear process for the Si tip involved blunting of the tip due to tip fragmentation and plastic deformation. In addition, previous studies on the relative contributions of energy dissipation processes to AFM tip wear are reviewed, and initial steps are taken towards applying this concept to AM-AFM.
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West, Paul, i Natasha Starostina. "AFM Capabilities in Characterization of Particle Nanocomposites: From Angstroms to Microns". W ASME 2006 Multifunctional Nanocomposites International Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/mn2006-17020.
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Scanning Probe Microscopy has been routinely employed as a surface characterization technique for nearly 20 years. Atomic Force Microscopy, the most widely used subset of SPM, can be performed in ambient conditions with minimum sample preparation. AFM is able to measure three-dimensional topography information from the angstrom level to the micron scale, with unprecedented resolution. This paper reviews the most common examples of nanoparticle composite evaluation with an AFM. AFM is well suited for dispersion strengthened composite characterization. A standard set of measured parameters includes: volume, In general, AFM nanocomposite characterization is both cost and time effective, as well as easier to use than electron microscopy. The resolution of AFM is greater than or comparable to SEM/TEM, and the strong advantages of AFM for nanoparticle composite characterization include morphology measurement along with direct measurements of height, volume and 3D display.
Raporty organizacyjne na temat "Atomic-resolution TEM"
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Or, Dani, Shmulik Friedman i Jeanette Norton. Physical processes affecting microbial habitats and activity in unsaturated agricultural soils. United States Department of Agriculture, październik 2002. http://dx.doi.org/10.32747/2002.7587239.bard.
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experimental methods for quantifying effects of water content and other dynamic environmental factors on bacterial growth in partially-saturated soils. Towards this end we reviewed critically the relevant scientific literature and performed theoretical and experimental studies of bacterial growth and activity in modeled, idealized and real unsaturated soils. The natural wetting-drying cycles common to agricultural soils affect water content and liquid organization resulting in fragmentation of aquatic habitats and limit hydraulic connections. Consequently, substrate diffusion pathways to soil microbial communities become limiting and reduce nutrient fluxes, microbial growth, and mobility. Key elements that govern the extent and manifestation of such ubiquitous interactions include characteristics of diffusion pathways and pore space, the timing, duration, and extent of environmental perturbations, the nature of microbiological adjustments (short-term and longterm), and spatial distribution and properties of EPS clusters (microcolonies). Of these key elements we have chosen to focus on a manageable subset namely on modeling microbial growth and coexistence on simple rough surfaces, and experiments on bacterial growth in variably saturated sand samples and columns. Our extensive review paper providing a definitive “snap-shot” of present scientific understanding of microbial behavior in unsaturated soils revealed a lack of modeling tools that are essential for enhanced predictability of microbial processes in soils. We therefore embarked on two pronged approach of development of simple microbial growth models based on diffusion-reaction principles to incorporate key controls for microbial activity in soils such as diffusion coefficients and temporal variations in soil water content (and related substrate diffusion rates), and development of new methodologies in support of experiments on microbial growth in simple and observable porous media under controlled water status conditions. Experimental efforts led to a series of microbial growth experiments in granular media under variable saturation and ambient conditions, and introduction of atomic force microscopy (AFM) and confocal scanning laser microscopy (CSLM) to study cell size, morphology and multi-cell arrangement at a high resolution from growth experiments in various porous media. The modeling efforts elucidated important links between unsaturated conditions and microbial coexistence which is believed to support the unparallel diversity found in soils. We examined the role of spatial and temporal variation in hydration conditions (such as exist in agricultural soils) on local growth rates and on interactions between two competing microbial species. Interestingly, the complexity of soil spaces and aquatic niches are necessary for supporting a rich microbial diversity and the wide array of microbial functions in unsaturated soils. This project supported collaboration between soil physicists and soil microbiologist that is absolutely essential for making progress in both disciplines. It provided a few basic tools (models, parameterization) for guiding future experiments and for gathering key information necessary for prediction of biological processes in agricultural soils. The project sparked a series of ongoing studies (at DTU and EPFL and in the ARO) into effects of soil hydration dynamics on microbial survival strategy under short term and prolonged desiccation (important for general scientific and agricultural applications).