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STEM modes in SEM
Konvalina, Ivo ; Paták, Aleš ; Mikmeková, Eliška ; Mika, Filip ; Müllerová, Ilona
The segmented semiconductor STEM detector in the Magellan 400 FEG SEM microscope\n(https://www.fei.com/) is used to detect transmitted electrons (TEs) and allows observing\nsamples in four imaging modes. Two modes of objective lens, namely high resolution (HR)\nand ultra-high resolution (UHR), differ by their resolution and by the presence or absence of\na magnetic field around the sample. If the beam deceleration (BD) mode is chosen, then\nan electrostatic field around the sample is added and two further microscope modes HR + BD\nand UHR + BD, become available. Trajectories of TEs are studied with regard to their angular\nand energy distribution in each mode in this work.\n
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A Perpetual Glass Ceiling? The Position of Women in the ICT Sector
Sobina, Anastasiia ; Žouželková Bartošová, Marie (referee) ; Ellederová, Eva (advisor)
Cílem této bakalářské práce je prozkoumat postavení žen v sektoru informačních a komunikačních technologií (dále jen ICT). Práce analyzuje nízké zastoupení žen v profesích ICT a v ICT firmách. Dále se zabývá hypotézou o ženách čelících takzvanému „skleněnému stropu“, který brání ženám a menšinám získat pozice na vyšší úrovni založené na stereotypech a předsudcích. Teoretická část této práce se skládá z následujících témat: role žen v historickém vývoji počítačů, seznam některých nejvýznamnějších žen v oboru informatiky, důvody pro nedostatečné zastoupení specialistů ženského pohlaví v ICT, koncepce „skleněného stropu“ a popisu současné situace v Evropě, konkrétně v České republice, kde tato data doplňují statistické informace organizace Czechitas. Informace byly shromážděny studiem literatury a analýzou studií souvisejících s daným tématem. V empirické části této práce byl proveden kvalitativní a kvantitativní výzkum. Data byla shromážděna prostřednictvím dotazníkového šetření a rozhovorů.
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Activating Strategies of Managing Students' Learning Process in Chemistry
Gabriel, Štěpán ; Rusek, Martin (advisor) ; Beneš, Pavel (referee)
TITLE: Activating Strategies of Managing Students' Learning Process in Chemistry AUTHOR: Št pán Gabriel DEPARTMENT: Department of Chemistry and Chemistry Education VEDOUCÍ PRÁCE: PhDr. Martin Rusek ABSTRACT This thesis is focused on literature-search evaluation of modern methods applied in chemistry education. Firstly, the development of chemistry education from the beginnings of the Czech schooling system until present is briefly described. Further, currently the most widely discussed methods used in Science education eventually Chemistry were defined based on the analysis of scientific literature and other available electronic resources. These methods are briefly characterized; an evaluation of the possibility of their usage in teaching practice in terms of Czech schools is made not only with regards to the educational reality in schools, but also with respect to the law (Framework Educational Programmes). KEYWORDS: Chemistry teaching, modern teaching methods, constructivism, project-based learning, inquiry-based learning, STEM, STEAM
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Bridge crane one-girder
Stanec, Stanislav ; Malach, František (referee) ; Malášek, Jiří (advisor)
This diploma thesis deals with constructional design and a calculation of one-girder bridge crane with the requested primary parametres: lifting capacity 10 000 kg, span 12 000 mm, wheel base 2 500 mm, travel height 7 000 mm. In diploma thesis, there is executed analysis of constructional designs of box girders, drawn up technical report with the analysis of the choice of the construction with important technical and physical calculations. Calculations were executed according to valid Czech state norms and literature. Drawing documentation is enclosed to this thesis.
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Difraction in a scanning electron microscopie
Řiháček, Tomáš ; Mika, Filip ; Matějka, Milan ; Krátký, Stanislav ; Müllerová, Ilona
Manipulation with the primary beam phase in a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM) has drawn significant attention in the microscopy community in the recent years. Although a few applications were found long before, some are still subjects of a future research. One of them is the use of electron vortex beams, which has very promising potential. It ranges from probing magnetic materials and manipulating with nanoparticles to spin polarization of a beam in an electron microscope.\nThe methods for producing electron vortex beams have undergone a lot of development in recent years as well. The most versatile way is holographic reconstruction using computer-generated holograms modifying either phase or amplitude. As the method is\nbased on diffraction, beam coherence is a very important parameter here. It is usually performed in TEM at energies of about 100 – 300 keV which are well suited for diffraction on artificial structures for two reasons. The coherence of the primary beam is often reasonable, and the diffraction pattern is easily observed. This is however not the case for a standard scanning electron microscope (SEM) with typical energy up to 30 keV.
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Correction of misalignment aberrations of a hexapole corrector using the differential algebra method
Radlička, Tomáš ; Oral, Martin
Overcoming the limitations of the Schertzer theorem is a long story in electron microscopy. Although the basic principle of a spherical aberration (C3) correction was suggested as early as in 1947 the first experimental correctors of spherical aberration were only realized in the last decade of the 20th century. The recent multipole correctors are designed for high-energy\nTEM or STEM, where the corrector system enables reaching the atomic resolution. On the other\nhand, the corrector for low-energy SEM has been developed but this type of corrector must also contain chromatic aberration (Cc) correction to reduce the effect of the non-zero energy width. Recently, the energies of SEM reach 30 keV and transmission mode (TSEM) is a standard part of the instrument. Standard resolution in TSEM is about 0.6 nm and it is limited by C3. Reaching atomic resolution with this set-up is not a real expectation because of its instability, but the resolution of about 0.2 nm would increase the field of applications. Corrector for these type of instruments should be (a) simple, compact and cheap (b) only spherical aberration of the third,\noptionally the fifth order must be corrected (c) effect of the chromatic aberration may be reduced by energy filtering. We studied design based on Rose’s hexapole corrector.
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Optimal X-ray detection for thin samples in low-energy STEM
Rozbořil, Jakub ; Oral, Martin ; Radlička, Tomáš
In many applications it is desirable to perform energy-dispersive X-ray spectroscopy (EDS) on very thin samples at low primary beam energies in a STEM. Thin samples, or lamellae, with the thickness of about 10 nm, are mostly prepared in focused ion beam instruments (FIBs), and they are used to evaluate experiments in the development of thin films and coatings, in the semiconductor industry, and in other applications. EDS then provides a map of different chemical elements or compounds in the sample, obtained by scanning the electron beam in a raster. Often the qualitative composition is known as a limited set of materials and only their distribution on the sample is to be determined. For large batches of samples fast measurements are desired to maximize utilization of expensive equipment. In this study we found a method to minimize the time needed to reliably acquire an elemental map by determining the optimal detector placement and the minimal necessary primary electron dose per pixel.
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Treatment of surfaces with slow electrons
Frank, Luděk ; Mikmeková, Eliška
Historically, the most annoying obstacle to acquiring SEM micrographs, in particular higher magnification micrographs taken with the ambition of resolving the finest observable details, may be said to be carbonaceous contamination “highlighting” the previous field of view with a black rectangle contoured by an even darker frame. This contamination is generated by decomposition of adsorbed hydrocarbon molecules with incident electrons leaving a crosslinked\nlayer of carbon atoms as a surface coating. The darker contours come from high surface mobility of hydrocarbon molecules from outside the field. The situation has been improved in recent decades by a lower pressure and dryer vacuum in specimen chambers, but even under ultrahigh vacuum (UHV) conditions the phenomenon occurs due to hydrocarbon molecules deposited on the specimen when loaded. Therefore, only in-situ cleaning with an\nattachment producing an ion beam solves this problem in UHV, while some plasma cleaners have also started appearing in standard-vacuum SEM chambers. The goal of complete removal of hydrocarbons is motivated by the supposed unavoidability of their decomposition with primary electrons. However, we have found hydrocarbon molecules being released, rather than their decomposition, when the energy of the impinging electrons drops beneath 50 eV or so.
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Monte Carlo simulations of electron scattering in scanning transmission electron microscopy
Záchej, Samuel ; Hrubanová, Kamila (referee) ; Krzyžánek, Vladislav (advisor)
This thesis deals with an electron scattering in STEM microscopy on objects with dif-ferent shapes, such as cuboid, sphere and hollow capsule. Monte Carlo simulations are used for description of multiple electron scattering. Except the theoretical analysis of the electron scattering and simulation methods, the thesis contains design and realiza-tion of an algorithm simulating electron scattering in given objects. In addition, there is a design for robustness evaluation of the simulation, based on comparison between results and known signals for a given object. Reliability of the algorithm was verified by experimental measurements of the electron scattering on a carbon layer.
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