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Bandpass filter for secondary electrons in SEM - simulations
Konvalina, Ivo; Mika, Filip; Krátký, Stanislav; Müllerová, Ilona
2016 - English
Scanning electron microscope (SEM) is commonly equipped with a through-the-lens secondary electron detector (TLD). The TLD detector in Magellan 400 FEG SEM works as a bandpass filter for the special setup of potentials of electrodes inside the objective lens, the positive potential on the specimen regulates the energy window of the filter. An energy filtered image contains additional information to that of an unfiltered one. The contrast of the filtered image is changed and new information about the topography and the material can be observed.\nTo understand image contrast formation with TLD detector we traced SEs and BSEs through the three-dimensional (3D) model of included 3D distribution of the electrostatic and magnetic fields. The properties of the bandpass filter were simulated for a working distance (WD) in the range of 1 mm to 3 mm and a primary beam energy (EP) from 1 keV to 10 keV.\nThe 3D electrostatic field of the system was calculated by Simion, magnetic field and raytracing were done using EOD program.
Keywords:
scanning electron microscope; TLD detector
Available at various institutes of the ASCR
Bandpass filter for secondary electrons in SEM - simulations
Scanning electron microscope (SEM) is commonly equipped with a through-the-lens secondary electron detector (TLD). The TLD detector in Magellan 400 FEG SEM works as a bandpass filter for the special ...
Bandpass filter for secondary electrons in SEM - experiments
Mika, Filip; Konvalina, Ivo; Krátký, Stanislav; Müllerová, Ilona
2016 - English
Bandpass energy filtering using a through-the-lens secondary electron (TLD) detector in a field emission gun SEM (FEG-SEM) has been known over a decade. During energy filtering, image contrast is changed and new information about the material can be observed. Our motivation for this study was to compare theoretical calculations with the experimental data\nof the SE bandpass energy filter in Magellan 400 FEG SEM. The TLD detector works as a bandpass energy filter for the special setup of electrode potentials inside the objective lens, with the positive potential on the specimen regulating the energy window.
Keywords:
electron microscopy; TLD
Available at various institutes of the ASCR
Bandpass filter for secondary electrons in SEM - experiments
Bandpass energy filtering using a through-the-lens secondary electron (TLD) detector in a field emission gun SEM (FEG-SEM) has been known over a decade. During energy filtering, image contrast is ...
Scanning very low energy electron microscopy for the characterization of polycrystalline metal samples
Pokorná, Zuzana; Knápek, Alexandr
2016 - English
We explored the possibility of a Scanning Electron Microscopy technique for the determination of crystallographic orientation, based on the measurement of the reflectivity of very low energy electrons. Our experiments are based on the concept that in the incident electron energy range 0–30 eV, electron reflectivity can be correlated with the electronic structure of the material, which varies with the local crystallographic orientation of the specimen.\nThe motivation for the development of this technique was to achieve a quick and highresolution means for determining the crystallographic orientation of very small grains in a polycrystalline material. The key limiting factor was the cleanliness of the sample surface and also the geometrical setup of the experiment.
Keywords:
electron microscopy; SEM; crystallographic orientation
Available at various institutes of the ASCR
Scanning very low energy electron microscopy for the characterization of polycrystalline metal samples
We explored the possibility of a Scanning Electron Microscopy technique for the determination of crystallographic orientation, based on the measurement of the reflectivity of very low energy ...
Using GPGPU in MR Data Processing
Mikulka, J.; Slíž, J.; Bartušek, Karel
2016 - English
The main tissue parameters targeted by MR tomography include, among others, relaxation times T-1 and T-2. This paper focuses on the computation of the relaxation time T-2 measured with the Spin Echo method. The maxima of measured echoes must be interleaved with an exponential function to compute the T2 relaxation. As this procedure needs to be repeated for each pixel of the scanned tissue, the processing of large images then becomes very intensive. This paper introduces the results provided by accelerated computation based on parallelization and carried out with a graphics card. By using the simple method of linear regression, we obtain a processing time of less than 36 ms. In the case of the Levenberg-Marquardt algorithm, the reconstruction was done in 96 ms. This period is at least 900 times shorter than that achievable with professional software.
Keywords:
GPGPU; data processing
Available at various institutes of the ASCR
Using GPGPU in MR Data Processing
The main tissue parameters targeted by MR tomography include, among others, relaxation times T-1 and T-2. This paper focuses on the computation of the relaxation time T-2 measured with the Spin Echo ...
New detectors for low-energy BSE
Lalinský, Ondřej; Schauer, Petr; Kučera, M.; Hanuš, M.; Lučeničová, Z.
2016 - English
Backscattered electrons (BSE) are mostly used to study the specimen’s topography. Nowadays, low energy (units of keV) electron beam imaging is often necessary for example for the research of nanomaterials, biomaterials or semiconductors. Because BSE detectors are mostly non-accelerating or low-accelerating, electrons with approximately the same energy as primary beam (PB) have to be detected. Therefore, BSE detectors need to become optimized for such low-energy electrons. For the scintillation detectors, the biggest problem probably lies in the scintillator. Semiconductor detectors aren’t studied in this work. Cerium activated bulk single crystals of yttrium aluminium garnet (YAG:Ce)Ce(X):Y(3-X)Al(5)O(12) are widely used as scintillators for the detection of high-energy backscattered electrons (BSE). However, commonly used YAG:Ce single crystal strongly loses its light yield (LY) with the decrease of the PB energy. As possible available alternatives for this application, bulk single crystals of yttrium aluminium perovskite (YAP:Ce) Ce(x)Y(1-X)AlO(3) and CRY018 can be predicted. However, similar LY drop can be expected also with these scintillators.
Keywords:
BSE detector; cathodoluminescence; low-energy electron; scintillator
Available at various institutes of the ASCR
New detectors for low-energy BSE
Backscattered electrons (BSE) are mostly used to study the specimen’s topography. Nowadays, low energy (units of keV) electron beam imaging is often necessary for example for the research of ...
The information depth of backscattered electron imaging
Piňos, Jakub; Mikmeková, Šárka; Frank, Luděk
2016 - English
Of the conventional imaging signals in the scanning electron microscope (SEM), the secondary electrons generally reflect surface properties of the sample, while the backscattered electrons (BSE) are capable of providing information about complex properties of the target down to a certain subsurface depth. Contrast mechanisms are combined according to the energy of incident electrons and energy and angular acceptance of BSE detection. In all cases, a question arises concerning the information depth of this mode. No applicable answer provides a definition declaring this depth as that from which we still obtain useful information about the object. We can employ software simulating the electron scattering in solids,\nwhile experimental approaches are also possible. Moreover, two analytic formulas can be found in the literature.
Keywords:
electron microscopy; SEM; BSE
Available at various institutes of the ASCR
The information depth of backscattered electron imaging
Of the conventional imaging signals in the scanning electron microscope (SEM), the secondary electrons generally reflect surface properties of the sample, while the backscattered electrons (BSE) are ...
Secondary electron spectroscopy and energy selective imaging for the engineering of carbon based materials
Rodenburg, C.; Masters, R.; Lidzey, D.; Unčovský, M.; Vystavěl, Tomáš; Mika, Filip
2016 - English
That the fine structure of secondary electron emission spectra (SES) from carbon fibres is effected by fibre crystallinity and molecular orientation and linked to engineering materials properties such as modulus was reported over three decades ago. In spite of this\nlongstanding knowledge SES are not yet widely exploited for materials engineering of carbon based materials, probably due to a lack of instrumentation that is suitable to collect SES from beam sensitive materials and also has the capability to visualise, local variation based on SES shape. Thanks to rapid advances in low voltage SEM that offer energy selective imaging, it was recently demonstrated that differences in SES for different carbon based materials can be used to map chemical variations with sub-nanometer resolution when only SE 8 < eV were\nselected to form the SEM images. Such high resolution is not surprising as the implementation of energy filtering in SEMs to improve image resolutions was previously advocated. To fully exploit energy selective imaging for materials engineering the nature of the features in the SES must be determined.
Keywords:
emission spectroscopy; SES
Available at various institutes of the ASCR
Secondary electron spectroscopy and energy selective imaging for the engineering of carbon based materials
That the fine structure of secondary electron emission spectra (SES) from carbon fibres is effected by fibre crystallinity and molecular orientation and linked to engineering materials properties such ...
Golden nanoparticle in optical tweezers: influence of shape and orientation on optical trapping
Šiler, Martin; Brzobohatý, Oto; Chvátal, Lukáš; Karásek, Vítězslav; Paták, Aleš; Pokorná, Zuzana; Mika, Filip; Zemánek, Pavel
2016 - English
Noble metal nanoparticles (NPs) have attracted increased attention in recent years due to various applications of resonant collective oscillations of free electrons excited with light (plasmon resonance). In contrast to bulk metal materials, where this plasmon resonance frequency depends only on the free electron number density, the optical response of gold and silver NPs can be tuned over the visible and near-infrared spectral region by the size and shape of the NP. Precise and remote placement and orientation of NPs inside cells or tissue would provide another degree of control for these applications. A single focused laser beam – optical tweezers – represents the most frequently used arrangement which provides threedimensional (3D) contact-less manipulation with dielectric objects or living cells ranging in size from tens of nanometers to tens of micrometers. It was believed that larger metal NPs behave as tiny mirrors that are pushed by the light beam radiative force along the direction of beam propagation, without a chance to be confined. However, recently several groups have reported successful optical trapping of gold and silver particles as large as 250 nm. We\noffer an explanation based on the fact that metal nanoparticles naturally occur in various nonspherical\nshapes, and their optical properties differ significantly due to changes in localized plasmon excitation.
Keywords:
NPs; plasmon resonance
Available at various institutes of the ASCR
Golden nanoparticle in optical tweezers: influence of shape and orientation on optical trapping
Noble metal nanoparticles (NPs) have attracted increased attention in recent years due to various applications of resonant collective oscillations of free electrons excited with light (plasmon ...
Proceedings of the 15th International Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation
Mika, Filip
2016 - English
The origins of the seminar “Recent Trends in Charged Particle Optics and Surface Physics Instrumentation” date back into the eighties, when as a part of the isolated “Eastern Bloc”, we were short of English-language books, papers and conferences. In 1990, at the second Seminar, there were as many as 30 participants from 5 countries. The third Seminar in 1992 was moved to hotel Skalský dvur in the Bohemian-Moravian Highlands where it has been held as a biannual meeting ever since.\nThe Seminar takes place in a secluded lakeside hotel surrounded by beautiful nature and calm forests, so all participants have a great possibility to see each other every day and to discuss their topics of interest in more detail. This is a great advantage compared to the huge bustling conferences with their many parallel sections, which are a lively celebration of science but\nsometimes it is difficult to meet there the person with whom you want to discuss a particular scientific topic in more detail.\nFrom the very beginning, the Seminar has been conceived as a meeting devoted more to asking questions not answered yet, than to reporting results. This spirit is usually less present in the introductory presentations and posters but is dominant in the following discussions.\n
Keywords:
electron microscopy
Available at various institutes of the ASCR
Proceedings of the 15th International Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation
The origins of the seminar “Recent Trends in Charged Particle Optics and Surface Physics Instrumentation” date back into the eighties, when as a part of the isolated “Eastern Bloc”, we were short of ...
Reverse Monte Carlo as MRS quantitation quality assessment
Jabłoński, Michal; Starčuková, Jana; Starčuk jr., Zenon
2016 - English
Data analysis of Magnetic Resonance Spectroscopy (MRS) using quantitation algorithms, such as AQSES, QUEST, AMARES or LCModel produces estimates of relative metabolite concentrations and their precision, estimated as the Cramer Rao Lower Bounds (CRLB). This assessment does not guarantee the uniqueness of the fit, and thus is not a true representation of the concentration uncertainty. In this publication authors propose to verify the quality of fitting by Reverse Monte Carlo method, which is independent of the estimator and has weaker requirements on the solution and model accuracy.
Keywords:
reverse Monte Carlo; MRS quantitation quality
Available at various institutes of the ASCR
Reverse Monte Carlo as MRS quantitation quality assessment
Data analysis of Magnetic Resonance Spectroscopy (MRS) using quantitation algorithms, such as AQSES, QUEST, AMARES or LCModel produces estimates of relative metabolite concentrations and their ...
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