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Very low energy electron transmission spectromicroscopy
Daniel, Benjamin; Radlička, Tomáš; Piňos, Jakub; Mikmeková, Šárka; Konvalina, Ivo; Frank, Luděk; Müllerová, Ilona
2018 - English
For more than 25 years, Scanning Low Energy Electron Microscopy (SLEEM) has been\ndeveloped at the Institute of Scientific Instruments (ISI), with several commercially available SEMs adapted with a cathode lens for SLEEM use, as well as a dedicated self-built UHVSLEEM setup.\nFor a better understanding of contrast formation at low energies, especially at very low energies below 50 eV, where the local density of states plays an important role, more general knowledge about the interaction of (very) low energy electrons with solids is required. This will be achieved using a newly developed ultra-high vacuum (UHV SLEEM) setup which includes several enhancements compared to other available machines. Data processing is presented in, and processed data will be further used and tested with the Monte Carlosimulation package BRUCE, which is being developed by Werner et al. at TU Vienna.
Keywords:
low energy scanning electron microscopy; electron microscopy; time of flight; electron energy lost spectroscopy
Available at various institutes of the ASCR
Very low energy electron transmission spectromicroscopy
For more than 25 years, Scanning Low Energy Electron Microscopy (SLEEM) has been\ndeveloped at the Institute of Scientific Instruments (ISI), with several commercially available SEMs adapted with a ...
Structure investigation of hydrogels using a cryo-SEM
Adámková, Kateřina; Hrubanová, Kamila; Samek, Ota; Trudičová, M.; Sedláček, P.; Krzyžánek, Vladislav
2018 - English
Hydrogels can be characterized as elastic hydrophilic polymer chains connected in network\nwhich are able to swell notably when exposed to aqueous media by absorbing considerable\namounts of water. Besides being a constituent of living organisms, nowadays, there are\nvarious fields hydrated polymers (e.g. polyvinyl alcohol, collagen, and starch) can be utilized\n– in both biological and non-biological form. Classic examples of such applications are\nhuman health and cosmetics (contact lenses, wound healing dressings and artificial\nreplacement tissues – skin, arterial grafts, cornea and spinal disc replacement), pharmacy\n(drug delivery systems), bioengineering, food industry, agriculture etc. Also, hydrogels\ncan reversibly change their shape when being exposed to a temperature change.
Keywords:
hydrogel; cryo-SEM; raman spectroscopy; high pressure freezing; freeze-etching; hyaluronic acid; agarose
Available at various institutes of the ASCR
Structure investigation of hydrogels using a cryo-SEM
Hydrogels can be characterized as elastic hydrophilic polymer chains connected in network\nwhich are able to swell notably when exposed to aqueous media by absorbing considerable\namounts of water. ...
Thermal desorption spectroscopy in prototype furnace for chemical vapor deposition
Průcha, Lukáš; Daniel, Benjamin; Piňos, Jakub; Mikmeková, Eliška
2018 - English
Cleaning of the sample surfaces is crucial for scanning electron microscopy, especially for\nlow energy electron microscopy or for the deposition of thin layers, such as graphene,\nwhere surface has to be well prepared. In the best case, every unwanted particle should be\ncleaned from the sample surface for best low energy electron microscopy observation or thin\nfilm deposition. Unfortunately, the standard cleaning procedures can leave residues on the\nsample surface. This work is focused on thermal desorption spectroscopy (TDS). TDS is a method of observing desorbed molecules from a sample surface during the increase of\ntemperature of the sample. The aim of this study was to determine optimum conditions:\ntemperature and time, to achieve clean surfaces in the shortest time.
Keywords:
thermal desorption spectroscopy; CVD; surface cleaning; silicon
Available at various institutes of the ASCR
Thermal desorption spectroscopy in prototype furnace for chemical vapor deposition
Cleaning of the sample surfaces is crucial for scanning electron microscopy, especially for\nlow energy electron microscopy or for the deposition of thin layers, such as graphene,\nwhere surface has ...
Electron optical properties of a new low-energy scanning electron microscope with beam separator
Radlička, Tomáš; Kolařík, V.; Oral, Martin
2018 - English
The low energy scanning electron microscope (SEM) which is currently at the Institute of\nScientific Instruments, suffers from low resolution and suboptimal detections systems. In the cathode lens regime, signal electrons are accelerated by the electric field between the sample and the objective lens, getting collimated. Those with low emission angles get through the bore in the BSE detector into the objective lens and cannot be detected by the available detectors now. The information about the sample provided by these electrons is lost, which limits our microscopy methods.\nThese two limitations are to be overcome with a new low-energy SEM, which was developed\nat Delong Instruments. It consists of a field emission gun with the energy width of 0.8 eV, a magnetic condenser lens, and an electrostatic triode objective lens. The acceleration voltage is 5 kV. The sample stage can be biased at up to -5 kV to provide low landing energy without strong decrease of the resolution – the effect of the cathode lens. A beam separator is placed in front of the deflection system for the detection of the signal electrons that get to the column. In a combination with standard detectors and cathode lens, it allows detecting all\nkinds of signal electrons.
Keywords:
low energy scanning electron microscopy; beam separation; aberrations
Available at various institutes of the ASCR
Electron optical properties of a new low-energy scanning electron microscope with beam separator
The low energy scanning electron microscope (SEM) which is currently at the Institute of\nScientific Instruments, suffers from low resolution and suboptimal detections systems. In the cathode lens ...
Inelastic mean free path from raw data measured by low-energy electrons time-of-flight spectrometer
Zouhar, Martin; Radlička, Tomáš; Oral, Martin; Konvalina, Ivo
2018 - English
The inelastic mean free path (IMFP) is a key parameter of electron transport in a solid. With\nthe rise of so-called meta-materials, materials of specific shape, such as 2D crystals, or\nmaterials with tailored functionality for next-generation electronic devices, the investigation\nof the IMFP is still topical and of high importance. This is true especially at low energies, landing energy of electrons below 100 eV, that are hard to study using well established\ntechniques of electron spectroscopy.
Keywords:
electron microscopy; time of flight; inelastic mean free path; low energy
Available at various institutes of the ASCR
Inelastic mean free path from raw data measured by low-energy electrons time-of-flight spectrometer
The inelastic mean free path (IMFP) is a key parameter of electron transport in a solid. With\nthe rise of so-called meta-materials, materials of specific shape, such as 2D crystals, or\nmaterials ...
Optical binding of polystyrene particles in tractor beam
Damková, Jana; Chvátal, Lukáš; Oulehla, Jindřich; Ježek, Jan; Brzobohatý, Oto; Zemánek, Pavel
2018 - English
The motion of a particle illuminated by a laser beam is usually driven by the photon flow due\nto the radiation pressure and therefore for particle trapping, one has to employ gradient forces. But in a tractor beam, objects are illuminated by the uniform light intensity and even so they can be pulled against the beam propagation. There have been developed several techniques how to create such a tractor beam. In our case, the tractor beam is created by two identical Gaussian beams that interfere under the defined angle. It creates the\nstanding wave, where in the transversal plane the particle is trapped by means of the gradient\nforce, but in the total beam propagation direction, the particle manipulation is driven by the non-conservative force. It is remarkable that this force can for the specific combinations of\nparameters pull the micro-particle against the beam propagation. This kind of behavior is\nbecause of the particle scattering where the majority of the incident photons is scattered in the forward direction and, based on the principle of action and reaction, the transfer of\nmomentum leads to a backward movement of the object. The pushing and pulling force is\nsensitive to the polarization of the laser beam, its incident angle and the particle size so this\ntechnique can be used for example for sorting of objects of different sizes.
Keywords:
optical binding; self-organization; optical force; tractor beam; holographic video microscopy
Available at various institutes of the ASCR
Optical binding of polystyrene particles in tractor beam
The motion of a particle illuminated by a laser beam is usually driven by the photon flow due\nto the radiation pressure and therefore for particle trapping, one has to employ gradient forces. But in ...
Field emission from W5O14 nanowires
Saqib, M.; Knápek, Alexandr; Jelenc, J.; Pirker, L.
2018 - English
The W5O14 (O/W=2.8) nanowires are metallic oxides with specific resistivity of 25 microOhm/cm and\ndiameters bellow 100 nm [1]. They were synthesized by iodine transport method using nickel\nas a growth promoter and WO3 as source of tungsten and oxygen. The field emission\ncharacteristics of single nanowires [2] and the films composed of these nanowires have been\nreported [3]. The emitting current densities up to 6.4 mA/cm2 have been obtained at relatively\nlow average electric field of about 3 V/Ohm*m. The samples were allowed to emit for more than\n100 hours without showing significant decays of the emitting current and without substantial\ncurrent oscillations. Here, we present field emission properties of single W5O14 nanowires\nexposed to two ranges of average electric fields (0.7–0.85 V/Ohm*m and up to 37–39 V/Ohm*m.
Keywords:
field emission; W5O14 nanowires
Available at various institutes of the ASCR
Field emission from W5O14 nanowires
The W5O14 (O/W=2.8) nanowires are metallic oxides with specific resistivity of 25 microOhm/cm and\ndiameters bellow 100 nm [1]. They were synthesized by iodine transport method using nickel\nas a ...
Stable Ce4+ centres - a tool to optimize cathodoluminescence performance in garnet scintillators
Lalinský, Ondřej; Schauer, Petr; Rathaiah, M.; Kučera, M.
2018 - English
Garnet single crystals are widely used as scintillators in electron detectors. Cerium activated lutetium aluminum garnet Cex:Lu3-xAl5O12 (LuAG:Ce) is a promising example of such material for these applications. This is mainly due to its high light yield (LY) of 25 kph/MeV, short decay time of 60–80 ns, high atomic density (6.7 g/cm3), and high radiation stability with no hygroscopicity. The cathodoluminescence (CL) performance can be improved by Ga and Gd doping the garnet matrix. Proper admixture of these elements can increase the LY to 50–60 kph/MeV in addition to eliminating unwanted slower decay components. There was an idea that further decay acceleration can be achieved by doping the garnet with monovalent (Li+) or divalent ions (Mg2+, Ca2+). This should increase the valency of some Ce3+ centres to Ce4+ which should better compete with electron traps, and thus accelerate the decay. Our previous work proved the same decay trend, however, at a price of the LY. Such LY loss may induce the idea, if the stable Ce4+ centres are really participating in Ce3+ emission.
Keywords:
garnet scintillators; cathodoluminescence performance
Available at various institutes of the ASCR
Stable Ce4+ centres - a tool to optimize cathodoluminescence performance in garnet scintillators
Garnet single crystals are widely used as scintillators in electron detectors. Cerium activated lutetium aluminum garnet Cex:Lu3-xAl5O12 (LuAG:Ce) is a promising example of such material for these ...
Optofluidic techniques for directed evolution of enzymes
Pilát, Zdeněk; Ježek, Jan; Samek, Ota; Zemánek, Pavel; Buryška, T.; Damborský, J.; Prokop, Z.
2018 - English
Enzymes are highly versatile and ubiquitous biological catalysts. They can greatly accelerate\nlarge variety of reactions, while ensuring appropriate catalytic activity and high selectivity.\nThese properties make enzymes attractive biocatalysts for a wide range of industrial and\nbiomedical applications. Over the last two decades, directed evolution of enzymes has\ntransformed the field of protein engineering.
Keywords:
optofluidics; Raman spectroscopy; enzymes
Available at various institutes of the ASCR
Optofluidic techniques for directed evolution of enzymes
Enzymes are highly versatile and ubiquitous biological catalysts. They can greatly accelerate\nlarge variety of reactions, while ensuring appropriate catalytic activity and high selectivity.\nThese ...
Real time observation of strain in the SEM sample
Piňos, Jakub; Frank, Luděk
2018 - English
The SEM with various detector arrangements and analytical attachments represents an\nirreplaceable tool in material research. One of the techniques available in most contemporary\nmicroscopes is the scanning low energy electron microscopy (SLEEM) with biased specimen, marketed as the beam deceleration mode, gentle beam and others. The SLEEM allows\ncontrolling the information depth of the backscatter electron (BSE) imaging within a wide\nrange by altering the landing energy of electrons.
Keywords:
SEM; SLEEM; deformation
Available at various institutes of the ASCR
Real time observation of strain in the SEM sample
The SEM with various detector arrangements and analytical attachments represents an\nirreplaceable tool in material research. One of the techniques available in most contemporary\nmicroscopes is the ...
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