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Classical and advanced methods of optical micromanipulations and their applications
Zemánek, Pavel ; Brzobohatý, Oto ; Šiler, Martin ; Karásek, Vítězslav ; Samek, Ota ; Jákl, Petr ; Šerý, Mojmír ; Ježek, Jan
Optical micro-manipulation techniques have been using for more than 30 years to transfer the momentum from light to microparticles or nanoparticles and influence their movement in liquid, on the surface, or in the air. These days such techniques become more developed and frequently used in physics, chemistry and biology to manipulate, trap, rotate, or sort various types of objects, including living cells in a contactless and gentle way.
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Proximity effect simulation for variable shape e-beam writer
Kolařík, Vladimír ; Matějka, Milan ; Urbánek, Michal ; Král, Stanislav ; Krátký, Stanislav ; Mikšík, P. ; Vašina, J.
Electron Beam Writer (EBW) is a lithographic tool allowing generation of patterns in high resolution. The writing is carried out into a layer of a sensitive material (resist), which is deposited on the substrate surface (e.g. silicon). The resolution of the EBW is limited not only by the beam spot size, but also by the electron scattering effects (forward scattering, backscattering). Thus, even if the beam spot size on the resist surface is very small, due to electron scattering effect in the resist, the exposed area is significantly broader than the original beam spot size [1, 2].
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Current state and prospects of scintillation materials for detectors in SEM
Schauer, Petr ; Bok, Jan
The two principal quantities are important for assessing the quality of each imaging system. Firstly, it is the detective quantum efficiency (DQE), which is primarily a measure of image noise. As the DQE is determined by signal to noise ratio (SNR), the efficient and noise-free components are the key to the high DQE. Second, not less important indicator of image quality is also the modulation transfer function (MTF). MTF describes the ability of adjacent pixels to change from black to white in response to patterns of varying spatial frequency, and hence it determines the actual capability to show fine detail, whether with full or reduced contrast. Using a scanning imaging system the fast components are the key to the good MTF. In a scintillation electron detector of scanning electron microscope (SEM) the scintillator is the most crucial component, because it significantly influences both the DQE and MTF. The aim of this study is to assess the scintillation materials suitable for SEM detectors characterized by the both high efficiency and fast decay characteristic.
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Calculation of difraction aberration using differential algebra
Radlička, Tomáš
The resolution in light microscopy is limited mainly by the wave length of light. Although the wave length of the electron is several orders Of magnitude smaller than that of light, the wave properties of the electron limit the resolution of scanning electron microscopes as well. It is described by the diffraction on the limiting aperture. While the effect of the diffraction can be reduced by increasing the limiting aperture size, it affects the resolution by increased geometrical and chromatic aberrations, that are more critical in the electron optics than in the light optics. These opposite trends cause that the best resolution is given by an aperture size that balances the effect of the diffraction with the effect of geometric and chromatic aberrations - an optimal aperture.
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Imaging the local density of electronic states by very low energy electron reflectivity
Pokorná, Zuzana ; Frank, Luděk
This work was concerned with the relationship between the reflectivity of very low energy electrons from a crystalline sample and its density of electron states above the vacuum level. Also, as different crystallographic orientations of the same single crystal exhibit different density of states, the usefulness of electron reflectivity at very low energies was demonstrated for the determination of crystallographic orientation. The technique chosen was the Scanning Low Energy Electron Microscopy (SLEEM) wich allows using arbitrarily low electron energies while preserving a very good image resolution. In our experiments, the incident electron energy ranged between 0 and 45 eV.
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Fast simulation of ToF spectrometers
Oral, Martin
A fast simulation method was developed for analysis of time-of-flight spectrometers and it has been successfully used to optimize parameters of a real instrument. In the general case, the function of a time-of-flight spectrometer is best modeled using the Monte Carlo method, That involves calculation of a high number of ion trajectories, which is time consuming. We have found a way to reduce the calculation time greatly by introducing a simplification and using pre-computed data independent on the ion mass and charge. The procedure makes it computationally feasible to run iterative optimizations. By comparing the results with those of a realistic simulation on a selected case, we have verified that there is no noticeable influence on the results.
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Characterization of industrial materials by slow and very slow electrons
Mikmeková, Šárka ; Müllerová, Ilona ; Frank, Luděk
Progress in materials science and engineering is inseparably connected with excellent knowledge of the correlation between materials properties and their microstructure. In our experiment an ultra-high vacuum scaning low energy electron microscope (UHV SLEEM) of an in-house design was used to observe microstructure of specimens. The UHV SLEEM is equipped with the cathode lens (CL) assembly, which enables us to observe samples at arbitrary landing energies of primary electrons. The device provides argon ion beam for in-situ cleaning of the specimen surface.
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Observation of high stressed hydrogenated carbon nitride films by SLEEM
Mikmeková, Eliška ; Müllerová, Ilona ; Sobota, Jaroslav
Two main factors can lead to losing adhesion in thin sputtered carbon nitride films: high residual stress and absorption of humidity. Basically, two different types of stress can be identified in thin films: compressive stress and tensile stress. Compressive stress can lead to wrinkling and film delamination, and tensile stress can cause the fracturing of thin films. For reactive sputtering of hydrogenated carbon nitride films, the compressive stress is typical. The films were prepared from graphite target (high purity, 99.9999 %) in mixture of nitrogen and hydrogen discharge.
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