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Imaging of carbon nanostructures by low energy STEM below 5 keV
Pokorná, Zuzana; Knápek, Alexandr; Jašek, O.; Prášek, J.; Majzlíková, P.
2014 - English
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.
Keywords:
low energy STEM; carbon nanostructures
Available at various institutes of the ASCR
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 - English
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.
Keywords:
ESEM; chemical and spectroscopic tools; environmental and applied science
Available at various institutes of the ASCR
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 - English
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.
Keywords:
ESEM; finite volume method
Available at various institutes of the ASCR
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 - English
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.
Keywords:
laser trapping; spectroscopy; biophysics; microfluidics
Available at various institutes of the ASCR
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 - English
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.
Keywords:
e-beam writer; optical nano structures; diffraction gratings; fractal gratings
Available at various institutes of the ASCR
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 ...
History of Electron Microscopy at the Institute of Scientific Instruments
Müllerová, Ilona
2014 - English
The development of the first transmission electron microscope (EM) at the Institute of Scientific Instruments (ISI) was completed in 1951. In 1954 a functional model of a desktop EM (the Tesla BS 242) was built and it won the Gold Medal at EXPO 1958. Over 1000 of these instruments were produced over a period of 20 years and exported to 20 countries. Unique transmission, emission and scanning EMs were developed and built during the 1960s. At the same time, the issues with high voltage sources, vacuum (and subsequently ultrahigh vacuum) and with the analysis of residual gases were resolved. In 1962, the first electron interference experiments in the world were carried out at ISI. Non-conventional forms of EM were also developed in the 1970s, e.g. interference shadow EM, Lorentz and tunneling EM, emission microscopy, as well as low energy electron diffraction [1]. Since 1973 the finite element method has been exploited for the computation of electrostatic and magnetic lenses. The ultrahigh vacuum scanning EM with cold field emission gun and an Auger spectrometer was fully developed and built at ISI in 1976, and the electron beam writer with a shaped beam and field emission gun in 1985. The development of new scintillation and cathodoluminescent screens began in the 1970s and our single crystal Yttrium Aluminium Garnet detector significantly improved detection systems all over the world. Low- and very-low-energy scanning EM was introduced to the world in 1990 as a unique technique. Today, it can achieve resolution as low as 4.5 nm at the incident electron energy of 20 eV.
Keywords:
Institute of Scientific Instruments; history of electron microscopy
Available at various institutes of the ASCR
History of Electron Microscopy at the Institute of Scientific Instruments
The development of the first transmission electron microscope (EM) at the Institute of Scientific Instruments (ISI) was completed in 1951. In 1954 a functional model of a desktop EM (the Tesla BS 242) ...
The Study of Ice Impurities Using the Environmental Scanning Electron Microscopy at Higher Pressures and Temperatures
Neděla, Vilém; Runštuk, Jiří; Klán, P.; Heger, D.
2014 - English
Natural ice and snow accumulate and concentrate significant amounts of impurities that can be stored or chemically transformed, and eventually released to the environment. The location of impurities and their interactions with the water molecules of ice have not yet been sufficiently clarified. The aim of this work is to observe an uranyl-salt brine layer on the ice surface using a back scattered electron detection and the ice surface morphology using a secondary electron detection under equilibrium conditions in a specimen chamber of environmental scanning electron microscope (ESEM). Our specially modified ESEM AQUASEM II equipped with the YAG:Ce3+ backscattered electron detector, an ionization detector of secondary electrons, a special hydration system and a Peltier cooled stage was used. The pressures between 400-700 Pa, 50% water-vapor saturation, and the temperatures above 250 K were utilized in our experiments. At these conditions, the phenomena of etching and subsequent stripping of impurities are largely suppressed.
Keywords:
uranyl-salt; BSE; ESEM
Available at various institutes of the ASCR
The Study of Ice Impurities Using the Environmental Scanning Electron Microscopy at Higher Pressures and Temperatures
Natural ice and snow accumulate and concentrate significant amounts of impurities that can be stored or chemically transformed, and eventually released to the environment. The location of impurities ...
Physical and biocatalytic properties of polyvinyl alcohol lens-shaped particles versus spherical polyelectrolyte complex microcapsules
Schenkmayerová, A.; Bučko, M.; Gemeiner, P.; Treľová, D.; Lacík, I.; Chorvát Jr., D.; Ačai, P.; Polakovič, M.; Lipták, L.; Rebroš, M.; Rosenberg, M.; Štefuca, V.; Neděla, Vilém; Tihlaříková, Eva
2014 - English
Direct comparison of key physical and chemical-engineering properties of two representative matrices for multipurpose immobilisations was performed for the first time. Polyvinyl alcohol lens-shaped particles LentiKats and polyelectrolyte complex microcapsules were characterised by advanced techniques with respect to the size distribution of the particles, their inner morphology as revealed by fluorescent probe staining, mechanical resistance, size-exclusion properties, determination of effective diffusion coefficient and environmental scanning electron microscope imaging. Recombinant cells E. coli overexpressing enzyme cyclopentanone monooxygenase were immobilised in polyelectrolyte complex microcapsules and LentiKats for comparison of their operational stability using model Baeyer-Villiger oxidation of (±)-cis-bicyclo[3.2.0]hept-2-en-6-one to regioisomeric lactones as important chiral synthons for potential pharmaceuticals.
Keywords:
SEM; ESEM
Available at various institutes of the ASCR
Physical and biocatalytic properties of polyvinyl alcohol lens-shaped particles versus spherical polyelectrolyte complex microcapsules
Direct comparison of key physical and chemical-engineering properties of two representative matrices for multipurpose immobilisations was performed for the first time. Polyvinyl alcohol lens-shaped ...
Examination of Graphene with Very Slow Electrons
Mikmeková, Eliška; Frank, Luděk
2014 - English
Although graphene has been available and intensively studied for nearly a full decade, new methods are still required for its examination and diagnostics. Even checking the continuity of layers and the reliable counting of layers of graphene and other 2D crystals should be easier to perform. Scanning electron microscopy with slow and very slow electrons offers an innovative tool enabling one to see graphene samples at nanometer or even sub-nanometer lateral resolution in both transmitted and reflected electrons and to count the number of layers reliably in both imaging modes. Diagnostics can be performed in this way on freestanding graphene samples as well as on graphene grown on the surfaces of bulk substrates. Moreover, bombardment with very slow electrons acts as an ultimate cleaning procedure removing adsorbed gases from crystal surfaces which can be monitored in scanned transmission electron images taken at below 50 eV.
Keywords:
graphene; slow electrons; very low energy scanning electron microscopy; ultralow energy STEM
Available at various institutes of the ASCR
Examination of Graphene with Very Slow Electrons
Although graphene has been available and intensively studied for nearly a full decade, new methods are still required for its examination and diagnostics. Even checking the continuity of layers and ...
E-beam Nano-patterning for Electroforming Replication
Krátký, Stanislav; Kolařík, Vladimír; Urbánek, Michal; Paták, Aleš; Horáček, Miroslav; Matějka, Milan
2014 - English
This contribution deals with nano-patterning by the way of electron beam lithography with satisfying requirements for electroforming replication of desired patterns. Electron beam lithography can be used for creating nano graphics (images, text etc.) due to its very high resolution and precision. However, patterns created by electron beam lithography cannot be applied for mass production directly because of resist material soft nature (usually a polymer material). Because of that, hard printing plate must be produced. Nickel plate prepared by electroforming is one of the ways to accomplish that. Prior to the production of nickel plate by electroforming, the surface of polymer material has to be covered by a sufficiently thick layer of metal. This procedure can lead to a partial destruction of the motif (completely covered by metal) thus the decreasing of nano graphics resolution. In this paper several nano graphics (images and text with various resolutions) are prepared in positive resist PMMA (thickness of 2000 nm) by e-beam lithography. Chemical developer (pentyl acetate) was used for wet developing of prepared patterns. The sputtering of silver (100 nm) was carried out to achieve sufficient thickness of conductive layer for electroforming. Electron scanning microscope was used for evaluation, which one of the images and texts are still recognizable.
Keywords:
electron beam lithography; nano graphics; polymethyl methacrylate; metal sputtering; electroforming
Available at various institutes of the ASCR
E-beam Nano-patterning for Electroforming Replication
This contribution deals with nano-patterning by the way of electron beam lithography with satisfying requirements for electroforming replication of desired patterns. Electron beam lithography can be ...
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