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Studium elektronově optických systémů s porušenou rotační symetrií
Horák, Michal ; Radlička, Tomáš (oponent) ; Zlámal, Jakub (vedoucí práce)
Tato práce se zabývá výpočty magnetické čočky, jejíž pólový nástavec má kvůli nepřesnostem ve výrobě porušenou rotační symetrii. Jsou diskutovány dva možné způsoby výpočtů - užití poruchové teorie a 3D výpočty. Jsou představeny tři metody pro určení osových multipólových funkcí ze 3D polí. Jsou vypočítány stopy svazku v obrazové rovině a aberační koeficienty a výsledky získané použitím poruchové teorie jsou porovnány s výsledky vypočítanými s využitím 3D simulací. Na základě těchto výsledků je diskutována vhodnost použití poruchové teorie.
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Parasitic aberrations of the hexapole corrector of spherical aberration - analysis and corrections
Sopoušek, Jan ; Lencová, Bohumila (oponent) ; Radlička, Tomáš (vedoucí práce)
One of the option of spherical aberration correction in electron microscopy is the hexapole corrector. Although the principle of the corrector is described in literature quite elaborately the adjustment of the corrector, which is crucial for its functionality, is studied just briefly. The thesis is dedicated to the analytic analysis of parasitic aberrations and its influence on resolution of an image by the Eikonal method and aberration integrals. It is shown that off-axial shifts and tilts play the major role in parasitic aberrations. In the end the procedure of adjustment of the hexapole corrector for elimination of parasitic aberrations is described.
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Aberration Corrector for an Exclusively Low-Voltage Electron Microscopy
Bačovský, Jaromír ; Radlička, Tomáš (oponent) ; Vašina, Radovan (oponent) ; Kolařík, Vladimír (vedoucí práce)
Current development of low voltage electron microscopy has led to an aberration correction of the instrument in order to improve its spatial resolution. In recent years, aberration correction has slowly become standard in high-end conventional transmission electron microscopy (50-200kV). However, the integration of a corrector to a desktop transmission electron microscope with exclusively low-voltage design seems to be a challenging task. The hexapole corrector based on permanent magnet technology seems to be a promising solution for the correction of the primary spherical aberration, especially if the compact dimensions and low complexity are to be preserved. The benefits and potential of the Rose hexapole corrector implemented to such low-voltage systems are critically considered in this thesis. The feasibility of a miniaturized corrector suitable for desktop LVEM is thoroughly discussed, including the aspect of corrector contribution to chromatic aberration that appears to be crucial. However, despite the effort to minimize the effect of chromatic aberration, its high importance with respect to the microscope resolution still remains a serious obstacle. It must be taken into account when the design is made. The presented concept is intended exclusively for STEM mode to avoid additional chromatic deterioration caused by electron passage through the specimen. The design of the key segment (transfer lens doublet) is discussed in detail, including its compensation system, which guarantees proper alignment. Optimal corrector parameters and theoretical resolution limits of such a system are proposed.
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Tolerances and Misalignment Aberrations for Electron Optical Elements and Systems
Sháněl, Ondřej ; Radlička, Tomáš (oponent) ; Tiemeijer,, Peter Christiaan (oponent) ; Zlámal, Jakub (vedoucí práce)
Inaccuracies in the production and assembling of rotationally symmetric lenses and deflectors and their accurate positioning in the electron optical system can be treated as an additional field with specific type of symmetry. The additional fields can be evaluated with the help of the finite element method in the program EOD. Tolerance analysis allows evaluation of the requirements on the dimensions and position of individual elements and their parts. Elimination of misalignment aberrations consists in determining the type and position of correcting deflection coils and multipoles so that these additional aberrations are removed or their effect is minimized. The aim of the dissertation is the analysis of the effect of misalignment aberrations and behavior of misaligned systems of transmission electron microscopes.
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Coulomb Interactions in Electron Beams in the Vicinity of a Schottky and Cold Field Emission Sources
Liška, Ivo ; Kotačka, Libor (oponent) ; Radlička, Tomáš (oponent) ; Lencová, Bohumila (vedoucí práce)
This thesis deals with the effects of the coulomb interactions in the vicinity of the Schottky and the cold field electron source. It provides a basic overview about the subject describes Monte Carlo simulation method and used emitter models. A new method for generating initial particle conditions has been developed, which respects in more detail than usually the physical emission process. Especially the effects of the mutual interactions on energy width, size of the virtual source and brightness in dependence on the tip radius and the angular intensity were investigated. The evolution of the energy width in the emitter region showed that the absolute majority of interactions take place within first few micrometer. The dependence of the calculated total energy width on the angular intensity was compared with available experimental data, showing a good agreement. The calculated contribution of the interaction effects to the energy width was compared with predictions based on analytical approximations. It has been shown that some of them predict reasonably the tendencies but cannot be used for quantitative estimations.
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Parasitic Aberrations of Electrostatic Deflectors
Badin, Viktor ; Radlička, Tomáš (oponent) ; Sháněl, Ondřej (oponent) ; Lencová, Bohumila (vedoucí práce)
The present doctoral dissertation deals with parasitic aberrations in electrostatic multipole optical components arising due to mechanical misalignment of the electrodes. Manufacturing and alignment precision of the mechanical parts can have a significant influence on the performance of electron beam machines such as microscopes and lithography (EBL) systems. Defects, imprecisions, and all other symmetry violations generate so-called parasitic fields whose effects on the particle beam are referred to as parasitic aberrations. Perturbations of axially symmetric lenses are usually treated using Sturrock's principle. Displacement or tilt of an entire multipole component can be analyzed in a globally shifted or tilted coordinate system. The present thesis deals with the misalignment of individual electrodes, which cannot be easily described with the mentioned approaches and usually need to be solved in 3D. Calculations in 3D are generally slower and have higher computational requirements than 2D tools standardly used in charged particle optics programs. To calculate parasitic fields generated by electrode misalignment, a 2D perturbation method compatible with the finite element method (FEM) has been developed in this thesis based on shifting the coordinate system locally around the affected electrode. Electrodes misaligned in each axis of the cylindrical coordinate system (longitudinal, radial, and azimuthal) are studied. Possible applications of the derived general method are shown, such as ellipticity and transverse shift of the entire deflector. For each of these cases, the resulting parasitic axial field functions (AFF) calculated in 2D are validated against the 3D solution. In addition to comparing parasitic AFFs, a case study is provided where the effect of parasitic aberrations on the electron beam in an entire optical column of an EBL system is shown, again validated against the 3D solution. The proposed method of calculating parasitic fields in 2D allows understanding the effects of different manufacturing and assembling tolerances, characterizing these effects, designing aberration correction devices, and optimizing mechanical tolerance requirements. The developed method can be run on any standard PC and is 1--2 orders of magnitude faster than solving the perturbed system in 3D.
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SMV-2021-43: Návrh a simulace elektronově optických systémů
Radlička, Tomáš
V rámci smluvního výzkum bylo zpracováno několik studií proveditelnosti týkajících se optických vlastností elektronově optických elementů, optimalizace jejich designu a jejich možné integrace do elektronového mikroskopu. Výzkum také zahrnoval vývoj programů, které se používají na elektronově optický design a jejich integrace do programového prostředí Julia.
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Aberration Corrector for an Exclusively Low-Voltage Electron Microscopy
Bačovský, Jaromír ; Radlička, Tomáš (oponent) ; Vašina, Radovan (oponent) ; Kolařík, Vladimír (vedoucí práce)
Current development of low voltage electron microscopy has led to an aberration correction of the instrument in order to improve its spatial resolution. In recent years, aberration correction has slowly become standard in high-end conventional transmission electron microscopy (50-200kV). However, the integration of a corrector to a desktop transmission electron microscope with exclusively low-voltage design seems to be a challenging task. The hexapole corrector based on permanent magnet technology seems to be a promising solution for the correction of the primary spherical aberration, especially if the compact dimensions and low complexity are to be preserved. The benefits and potential of the Rose hexapole corrector implemented to such low-voltage systems are critically considered in this thesis. The feasibility of a miniaturized corrector suitable for desktop LVEM is thoroughly discussed, including the aspect of corrector contribution to chromatic aberration that appears to be crucial. However, despite the effort to minimize the effect of chromatic aberration, its high importance with respect to the microscope resolution still remains a serious obstacle. It must be taken into account when the design is made. The presented concept is intended exclusively for STEM mode to avoid additional chromatic deterioration caused by electron passage through the specimen. The design of the key segment (transfer lens doublet) is discussed in detail, including its compensation system, which guarantees proper alignment. Optimal corrector parameters and theoretical resolution limits of such a system are proposed.
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