Ne (643)
Počet nalezených dokumentů:
643
Publikováno od
do
Beam damage of embedding media sections and their investigations by SEM
Krzyžánek, Vladislav; Novotná, V.; Hrubanová, Kamila; Nebesářová, J.
2014 - anglický
A scanning transmission electron microscope (STEM) is useful device combining features of scanning and transmission electron microscopes. The sample in form of the ultrathin section is scanned by the electron probe and the transmitted electrons are detected. Except the dedicated STEMs this mode can exist as options in both TEM and SEM. The STEM based on the SEM equipped by a transmission detector was used for presented experiments. Nowadays, such low voltage STEM is more often used, and in many cases replaces the typical TEM. Here, we report investigations of embedding media that are typically used for TEM preparation of biological samples. The STEM detector in SEM may be able to detect both bright-field and dark-fields images. It uses much lower acceleration voltages (30 kV and below) than conventional TEM or STEM. However, materials like biological samples, polymers including embedding media are electron beam sensitive. Two the most important beam damages are the mass loss and the contamination. Both types of damages depend on the used electron energy and the electron dose applied to the sample. The mass loss depends on the sample composition, and the contamination results from the poor vacuum in the specimen chamber of the SEM, cleanness of the sample surface, etc.
Klíčová slova:
beam damage; mass determination; ADF imaging
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Beam damage of embedding media sections and their investigations by SEM
A scanning transmission electron microscope (STEM) is useful device combining features of scanning and transmission electron microscopes. The sample in form of the ultrathin section is scanned by the ...
Plasmonic Structures In PMMA Resist
Urbánek, Michal; Krátký, Stanislav; Šimík, M.; Kolařík, Vladimír; Horáček, Miroslav; Matějka, Milan
2014 - anglický
Some metal material can exhibit special physical phenomenon which is called plasmon resonance. This effect can be used in optical applications where designed structures, using this effect, have special function as optical filters, polarizers, holograms etc. This papers deals with preparation of plasmonic structures in poly(methyl methacrylate) (PMMA) resist which is the most common material used for e-beam processing. Designed structures were prepared by e-beam writer with Gaussian beam and accelerating voltage of 100 kV. These structures are usually prepared into negative tone resist hydrogen silsesquioxane (HSQ). We prepared these structures by unusual way into positive resist PMMA due to unavailability and cost of HSQ resist. By this way we are able to achieve high resolution of structures suitable for special optical application. Exposed structures were developed in isopropyl based developer. Final structures after development were coated by two metal layers (first one is Ag layer, second one is gold) by magnetron sputtering and vacuum evaporation. The quality of prepared plasmonic structures was examined by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM).
Klíčová slova:
electron beam lithography; plasmonic structures; PMMA; metal coating
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Plasmonic Structures In PMMA Resist
Some metal material can exhibit special physical phenomenon which is called plasmon resonance. This effect can be used in optical applications where designed structures, using this effect, have ...
Exposure Time Comparison between E-beam Writer with Gaussian Beam and Variable Shaped Beam
Horáček, Miroslav; Krátký, Stanislav; Urbánek, Michal; Kolařík, Vladimír; Meluzín, Petr; Matějka, Milan; Chlumská, Jana
2014 - anglický
One of the main goals in e-beam lithography is to increase exposure speed to achieve higher throughput. There are basically two types of electron-beam writers, shaped beam lithography systems and Gaussian beam lithography systems. The exposure time of both e-beam writers consist in essence of beam-on time, deflection system stabilization time and stage movement time. Exposure time testing was carried out on two types of patterns. There were completely filled in areas, binary period gratings (ratio 1:1 between exposed and unexposed areas), and multileveled structures (computer generated holograms). Exposures data was prepared according to standard technology (PMMA resist, exposure dose, non-alcoholic based developer) for both systems. The result of experiment shows that variable shaped beam system has advantage in multileveled structures while the Gaussian beam system is more suitable for gratings type of pattern. It was proved that combination of both systems has its use to increase exposures throughput.
Klíčová slova:
e-beam writer; Gaussian beam; variable shaped beam
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Exposure Time Comparison between E-beam Writer with Gaussian Beam and Variable Shaped Beam
One of the main goals in e-beam lithography is to increase exposure speed to achieve higher throughput. There are basically two types of electron-beam writers, shaped beam lithography systems and ...
Factors Influencing Thermal Radiative Properties of Metals
Králík, Tomáš; Hanzelka, Pavel; Musilová, Věra; Srnka, Aleš
2014 - anglický
Data on thermal absorptivity and emissivity are important for calculations of heat flows in cryogenic devices. Although thermal radiative properties of materials used in cryogenics are measured, published and used for more than sixty years we have noticed that sometimes users of that data don’t well understand the significance of individual factors influencing thermal radiative properties. The sensitivity of the thermal radiative properties of metals to the condition of the surface and the difficulty of measurement, especially at low temperatures is probably the reason of dispersion of the published values. The effect of the material and its purity, finishing (machining, mechanical or chemical polishing) and of the protective coatings or accidental layers (water, oxidation) on the thermal radiative properties is not always obvious. Influence of the material, surface treatment, roughness and layers on the surface is discussed on the basis of our 20 year experience with measurement of the emissivity and absorptivity in the range from 20 K to 300 K.
Klíčová slova:
emissivity; absorptivity; radiative heat transfer; surface finish; cryogenics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Factors Influencing Thermal Radiative Properties of Metals
Data on thermal absorptivity and emissivity are important for calculations of heat flows in cryogenic devices. Although thermal radiative properties of materials used in cryogenics are measured, ...
Performance of YAG:Ce Scintillators for Low-Energy Electron Detectors in S(T)EM
Lalinský, Ondřej; Bok, Jan; Schauer, Petr; Frank, Luděk
2014 - anglický
Cerium activated single crystals of yttrium aluminium garnet (YAG:Ce) Y3-xCexAl5O12 are widely used as scintillators in electron detectors for S(T)EM. Nowadays, it is sometimes necessary to detect low-energy electrons without post-acceleration. In such cases, extremely sensitive detectors are required that are able to detect even electrons with energies of only hundreds of eV while avoiding charging of the scintillator surface. However, commonly used scintillators strongly lose their light yield with the decrease of the incident electron energy. Moreover, a thinner conductive layer on the scintillator surface has to be used to allow low-energy electrons to pass through. Possible charging of the surface negatively affects its cathodoluminescence (CL) light yield. The low-energy electron excitation takes place closer to the scintillator surface where damage can be expected owing to its preparation, which also reduces the CL light yield. The aim was to study the influence of the scintillator and its conductive layer on the low-energy electron detection efficiency.
Klíčová slova:
scintillator; YAG:Ce; single crystal; electron detector; SEM; STEM; low-energy electron; cathodoluminescence
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Performance of YAG:Ce Scintillators for Low-Energy Electron Detectors in S(T)EM
Cerium activated single crystals of yttrium aluminium garnet (YAG:Ce) Y3-xCexAl5O12 are widely used as scintillators in electron detectors for S(T)EM. Nowadays, it is sometimes necessary to detect ...
Imaging of carbon nanostructures by low energy STEM below 5 keV
Pokorná, Zuzana; Knápek, Alexandr; Jašek, O.; Prášek, J.; Majzlíková, P.
2014 - anglický
Our work deals with the imaging of nanostructures composed of light biogenic elements, such as carbon nanotubes, by low energy scanning transmission electron microscopy (STEM). Compared to imaging at the voltages commonly used for TEM and STEM, low energy electrons seem very promising in terms of specimen damage that is caused by a number of elastic andn inelastic collisions. In carbonaceous materials, the most problematic is probably the knock-on damage, where the structure can be impaired by carbon atom displacement. To avoid this problem with structures composed of light elements, a reduction in beam voltage going down to 5 keV has recently been proposed. The range below 5 keV has not been explored yet for this purpose, although electron scattering in matter is lower for these energies, which allows achieving a higher spatial resolution. We aim to demonstrate that additional reduction of incident electron energy may yield interesting contrast features.
Klíčová slova:
low energy STEM; carbon nanostructures
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Imaging of carbon nanostructures by low energy STEM below 5 keV
Our work deals with the imaging of nanostructures composed of light biogenic elements, such as carbon nanotubes, by low energy scanning transmission electron microscopy (STEM). Compared to imaging at ...
Ice and its impurities from the perspectives of photochemistry and electron microscopy
Heger, D.; Krausko, J.; Klán, P.; Runštuk, Jiří; Neděla, Vilém
2014 - anglický
Ice as a solid phase of water is an interesting but still not well understood medium. Our photochemical group utilized chemical and spectroscopic tools to acquire information relevant to the environmental and applied science. In the introduction I would like to stress some important facts on ice and frozen aqueous solutions stemmed from our work. Still opened question, that we are trying to answer by the ESEM, is where and at what forms are the impurities located after the freezing. The recently published results from the pilot collaboration with Dr. Neděla’s group will be detailed.
Klíčová slova:
ESEM; chemical and spectroscopic tools; environmental and applied science
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Ice and its impurities from the perspectives of photochemistry and electron microscopy
Ice as a solid phase of water is an interesting but still not well understood medium. Our photochemical group utilized chemical and spectroscopic tools to acquire information relevant to the ...
Use systems for the analysis of gas flow
Maxa, J.; Neděla, Vilém; Hladká, K.; Vyroubal, P.; Vaculík, S.; Hlavatá, P.
2014 - anglický
Environmental scanning electron microscope is explaining withdrawing of two differentially pumped chambers in a drawing area. To solve this problem is used finite volume method. This method includes several steps: - With using of mesh the area is dividing into discrete volume. - Discretization and balancing of the unknown quantities in each finite volume - Numerical solution of discretized equations.
Klíčová slova:
ESEM; finite volume method
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Use systems for the analysis of gas flow
Environmental scanning electron microscope is explaining withdrawing of two differentially pumped chambers in a drawing area. To solve this problem is used finite volume method. This method includes ...
Raman tweezers in microfluidic systems for automatic analysis and sorting of living cells
Pilát, Zdeněk
2014 - anglický
We have devised an automatic analytical and sorting system combining optical trapping with Raman spectroscopy in microfluidic environment, together with computerized real time image analysis, spectra processing and micromanipulation. This device serves to identify and sort biological objects, such as living cells of various prokaryotic and eukaryotic organisms based on their Raman spectral properties. This approach allowed us to collect information about the chemical composition of the objects, such as the presence and composition of lipids, proteins, or nucleic acids without using artificial chemical probes such as fluorescent markers. The non-destructive and non-contact nature of this optical analysis and manipulation allowed us to separate individual living cells of our interest in a sterile environment and provided the possibility to cultivate the selected cells for further experiments. The special microfluidic chip uses gravity to move the cells across the sorting area. Our system uses dedicated software to achieve fully automated spectral analysis and sorting. The devised system is a robust and universal platform for non-contact sorting of microobjects based on their chemical properties. It could find its use in many medical, biotechnological, and biological applications.
Klíčová slova:
laser trapping; spectroscopy; biophysics; microfluidics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Raman tweezers in microfluidic systems for automatic analysis and sorting of living cells
We have devised an automatic analytical and sorting system combining optical trapping with Raman spectroscopy in microfluidic environment, together with computerized real time image analysis, spectra ...
Some Other Gratings: Benchmarks for Large-Area E-Beam Nanopatterning
Meluzín, Petr; Horáček, Miroslav; Urbánek, Michal; Bok, Jan; Krátký, Stanislav; Matějka, Milan; Chlumská, Jana; Kolařík, Vladimír
2014 - anglický
E-beam lithography is a flexible technology for diffraction gratings origination. Nevertheless, requirements of the high optical quality of large area diffractive structures imply various severe challenges to e-beam delineating processes. This paper summarizes the e-beam process parameters that influence the quality of large area grating structures. Next, we propose some new methods to prepare diffraction gratings that were found to be useful for testing and benchmarking purposes. Those methods include single line gratings, labyrinth structures, fractional structures, tiling patterns, quasi regular filling structures and forked line structures. Various samples were prepared with the standard and newly developed e-beam patterning processes using both e-beam writers available: one with the Gaussian beam at 100 keV and another one with the shaped beam at 15 keV. Some of the results are presented further in this paper, their variants and parameters are discussed as well as their usefulness as benchmarking e-beam patterns for large area optical structures, elements and devices.
Klíčová slova:
e-beam writer; optical nano structures; diffraction gratings; fractal gratings
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Some Other Gratings: Benchmarks for Large-Area E-Beam Nanopatterning
E-beam lithography is a flexible technology for diffraction gratings origination. Nevertheless, requirements of the high optical quality of large area diffractive structures imply various severe ...
NUŠL poskytuje centrální přístup k informacím o šedé literatuře vznikající v ČR v oblastech vědy, výzkumu a vzdělávání. Více informací o šedé literatuře a NUŠL najdete na webu služby.
Vaše náměty a připomínky posílejte na email nusl@techlib.cz
Provozovatel
Zahraniční báze