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PUBLIKACE V ČASOPISECH
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  • Lalinsky, O.; Schauer, P. NOVÉ! Časově korelované čítání jednotlivých fotonů: Nová metoda pro studium doznívání katodoluminiscence., Fine Mechanics and Optics, 62 (2017), 248-250.
    Abstrakt:
    Článek se zabývá detekcí slabé časově rozlišené katodoluminiscence (CL). Je zde představena metoda časově korelovaného čítání jednotlivých fotonů (TCSPC), která, na rozdíl od běžně používané metody měření časové závislosti analogového signálu, vyniká v detekci slabé CL především rychlých scintilátorů. V článku je rovněž obsaženo srovnávací měření časově rozlišené intenzity CL s využitím obou metod.

  • Schauer, P.; Lalinsky, O.; Kucera, M; Lucenicova, Z.; Hanus, M. Effect of Mg co-doping on cathodoluminescence properties of LuGAGG:Ce single crystalline garnet films., Optical Materials, 72 (2017), 359-366.
    Abstrakt:
    Mg2+ co-doped (LuGd)3(GaAl)5O12:Ce (LuGAGG:Ce,Mg) multicomponent single crystalline epitaxial garnet films were prepared and their cathodoluminescence (CL) and thermoluminescence (TSL) properties were studied in this paper. The films were prepared using the liquid phase epitaxy from lead-free BaO-B2O3-BaF2 flux and their scintillation properties were characterized using the 10 keV collimated e-beam. More specifically, temperature dependent CL intensity, CL emission spectra, CL decay characteristics as well as TSL emission characteristics of the mentioned films were measured. At the highest content of Mg (700 ppm), the CL decay time was as low as 28 ns and the CL afterglow was as low as 0.01% at 1 µs after the e-beam excitation cut-off, which are important parameters for electron detectors in e-beam devices. The CL temperature quenching of the studied films began above room temperature. An increase of Mg concentration to or above 280 ppm quenched the characteristic CL emission of LuGAGG:Ce,Mg. The TSL measurements show that the trap population in studied garnet samples is considerably suppressed. The LuGAGG:Ce,Mg multicomponent single crystalline epitaxial films were evaluated as the perspective fast scintillators for the electron detectors in the e-beam devices.
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  • Kucera, M.; Onderisinova, Z.; Bok, J.; Hanus, M.; Schauer, P.; Nikl, M.: Scintillation response of Ce3+ doped GdGa-LuAG multicomponent garnet films under e-beam excitation., J. Lumin. 169 (2016), 647-677.
    Abstrakt:
    Scintillation properties of multicomponent (GdLuY)3(GaAl)5O12:Ce3+ epitaxial garnet films were studied under electron beam excitation. The role of the shallow traps was investigated using the scintillation decay kinetics and cathodoluminescence spectroscopy. Tunneling-driven recombination, which provides a physical ground for the slow scintillation decay component in LuAG:Ce single crystals, is discussed in detail.
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  • Bok, J.; Schauer, P.: Apparatus for temperature-dependent cathodoluminescence characterization of materials., Meas. Sci. Technol., 25 (2014), doi:10.1088/0957-0233/25/7/075601
    Abstrakt:
    An apparatus for characterization of temperature-dependent cathodoluminescence (CL) of solid-state materials is presented. This device excites a specimen using an electron beam and the CL emission is collected from the specimen side opposite the e-beam irradiation. The design of the temperature-controlled specimen holder that enables cooling down to 100 K and heating up to 500 K is described. The desired specimen temperature is automatically stabilized using a PID controller, which is a proportional-integral-derivative control feedback loop. Moreover, the specimen holder provides in-situ e-beam current measurement during the specimen excitation. The apparatus allows the measurement of the CL intensity, the CL spectrum, or the CL intensity decay depending on the specimen temperature, or on variety excitation conditions, such as excitation energy, electron current (dose), or excitation duration. The apparatus abilities are demonstrated by an example of the CL measurements of the YAG:Ce single-crystal scintillator.
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  • Bok, J.; Schauer, P.: Performance of SEM scintillation detector evaluated by modulation transfer function and detective quantum efficiency function., Scanning, 36 (2014), 384–393.
    Abstrakt:
    In the paper, the SEM detector is evaluated by the modulation transfer function (MTF) which expresses the detector’s influence on the SEM image contrast. This is a novel approach, since the MTF was used previously to describe only the area imaging detectors, or whole imaging systems. The measurement technique and calculation of the MTF for the SEM detector are presented. In addition, the measurement and calculation of the detective quantum efficiency (DQE) as a function of the spatial frequency for the SEM detector are described. The measurement technique uses the time-modulated e-beam which creates well-defined input signal for the detector. The MTF and DQE measurements are demonstrated on the Everhart-Thornley scintillation detector. This detector was alternated using the YAG:Ce, YAP:Ce and CRY18 single-crystal scintillators. The presented MTF and DQE characteristics show good imaging properties of the detectors with the YAP:Ce or CRY18 scintillator, especially for a specific type of the e-beam scan. The results demonstrate the great benefit of the description of SEM detectors using the MTF and DQE. In addition, point-by-point and continual-sweep e-beam scans in SEM were discussed and their influence on the image quality was revealed using the MTF.
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  • Schauer, P.; Bok, J.: Study of spatial resolution of YAG:Ce cathodoluminescent imaging screens., Nucl. Instr. Meth. B 308 (2013), 68-73.
    Abstrakt:
    The aim of this paper is to find spatial resolution of YAG:Ce single crystal cathodoluminescent imaging screens at primary electron energies in the range from 20 to 100 keV using theoretical simulation as well as the experimental method. Calculations have been based on the MC model for energy distribution of excited electrons. Measurement of the spatial resolution was realized using the sharp edge projection method. As the projection object, the silicon single crystal plate with the hole made by the anisotropic etching was prepared and used. The edge of this object was examined at the magnification of up to 125000x. For the edge projection method, the experimental system with the screen specimen cartridge and with the light-microscopic module using the magnifying objective and the CCD camera has been constructed and used. The simulated as well as experimental results have been processed and are presented in the form of line spread function (LSF). The resulted image qualities were quantified using modulation transfer function (MTF). Finally, the spatial resolutions of YAG:Ce single crystal imaging screens were determined as the number of lines per mm for the contrast of 50 % and primary electron beam energies of 20, 60 and 100 keV.
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  • Bok, J.; Schauer, P.: LabVIEW-based control and data acquisition system for cathodoluminescence experiments., Rev. Sci. Instrum. 82, 113109 (2011), doi:10.1063/1.3662203
    Abstrakt:
    Computer automation of cathodoluminescence (CL) experiments using equipment developed in our laboratory is described. The equipment provides various experiments for CL efficiency, CL spectra, and CL time response studies. The automation was realized utilizing the graphical programming environment LabVIEW. The developed application software with procedures for equipment control and data acquisition during various CL experiments is presented. As the measured CL data are distorted by technical limitations of the equipment, such as equipment spectral sensitivity and time response, data correction algorithms were incorporated into the procedures. Some examples of measured data corrections are presented.
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  • Schauer, P.: Optimization of decay kinetics of YAG:Ce single crystal scintillators for S(T)EM electron detectors., Nucl. Instr. Meth. B 269 Issue 21 (2011), 2572-2577.
    Abstrakt:
    To enhance the detective quantum efficiency (DQE) of scintillation electron detectors for scanning electron microscopes or scanning transmission electron microscopes (S(T)EM) the cathodoluminescence (CL) decay kinetics of YAG:Ce single crystal scintillators is studied in this paper. Some possibilities for reductions of decay time and afterglow of the mentioned scintillators are presented. The pulse mode utilizing a blanking system and 10 keV electrons for the excitation and a sampling oscilloscope for the CL detection were used for the measurement of decay characteristics. The CL decay characteristics of YAG:Ce single crystals of different Ce concentrations, pulled by the Czochralski method and cleaned and annealed under specific conditions, were measured in dependence on excitation pulse duration and on the specimen temperature. To interpret the presented results, a kinetic model of cathodoluminescence of the YAG:Ce single crystals was created. The effects of quenching impurities and of defect centers in YAG:Ce were specified.
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  • Schauer, F.; Schauer, P.; Kuřitka, I.; Bao, H.: Conjugated Silicon–Based Polymer Resists for Nanotechnologies: EB and UV Meditated Degradation Processes in Polysilanes., Materials Transactions, 51 Issue 2 (2010), 197-201.
    Abstrakt:
    The comparison of the susceptibility of aryl-substituted polysilanes to the photodegradation by electron beam (EB) and UV radiation is examined on the prototypical material, poly[methyl(phenyl)silylene] (PMPSi). The main purpose of this paper is to compare the photoluminescence (PL) and cathodoluminescence (CL) after major degradation, predominantly in the long wavelength range of 400–600 nm, studying the disorder due to dangling bonds, conformational transformations and weak bonds created by the degradation process. The UV degradation was a completely reversible process, whereas the EB degradation process was only reversible, provided certain material specific level of degradation was not exceeded. This observation supports different paths and final states in both UV and EB degradations. The results serve for the optimization of polysilane nanoresists.
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  • Schauer, P. Extended Algorithm for Simulation of Light Transport in Single Crystal Scintillation Detectors for S(T)EM., Scanning, 29 Issue 6 (2007), 249-253.
    Abstrakt:
    The new extended Monte Carlo (MC) simulation method for photon transport in S(T)EM back scattered electron (BSE) scintillation detection systems of various shapes is presented in this paper. The method makes use of the random generation of photon emission from a scintillator luminescent centre and describes the trajectory of photons and the efficiency of their transport toward the photocathode of the photomultiplier tube. The paper explains a new algorithm for determining the position of interaction of the photon with the surface of the single crystal scintillator or of the light guide with nearly arbitrary shapes. Some examples of the utilization of the simulation method are also included, and conclusions for very simple edge-guided signal (EGS) scintillation detection systems made. The computer optimized design of the BSE scintillation detector for the S 4000 Hitachi SEM was chosen to demonstrate the capability of this MC simulation method.
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  • Horák, P.; Schauer, P.: Cathodoluminescence as a method for the study of degradation of polysilanes. Nucl. Instrum. Methods Phys. Res. Sect. B - Beam Interact. Mater. Atoms 252 Issue 2 (2006), 303-307.
    Abstrakt:
    The paper presents a unique cathodoluminescent (CL) method suitable for studying polysilane properties and the first CL characteristics of the material being investigated. Poly[methyl(phenyl)silylene] (PMPSi) was selected as a typical representative of polysilanes. The PMPSi study is based on the measurement of the intensity of CL emission after passing through the specimen. The major problem of this study is the susceptibility of the material being investigated to the degradation by electron beam. PMPSi degradation strongly decreases the CL intensity. Therefore, detection in the synchronous mode was used to eliminate the influence of the background and of the noise. It was found that the degradation process is partly reversible. A partial recovery of intensity was attributed to reverse recombination reactions of silyl radicals in a vacuum after 20 h of annealing at room temperature. Understanding of the physical and chemical mechanisms of the degradation and of the reversible process of the PMPSi CL emission is interesting for science as well as the application (e.g. resist in electron beam lithography or molecular scale electronic devices).
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  • Schauer, P.; Nešpůrek, S.; Schauer, F.; Autrata, R.: Optimization of Poly-(Methylphenylsilylene) Specimens for Cathodoluminescence Measurement. Microscopy and Microanalysis 9 [Sup. 3] (2003) p.156-157.
    Úvod:
    Two possibilities of photon collection from the luminescence centra can be applied at cathodoluminescence (CL) measurement of transparent specimens. The CL emission can be collected both from the side of excitation and substrate using a lens and a light guide, respectively. To choose the better alternative, one has to study optical properties and electron-interactive volumes of specimen materials. Based on this knowledge, optimized geometry, dimension and arrangement of the specimen can be designed. The object of our interest was the CL study of Poly-(Methylphenylsilylene), i.e. PMPhSi, which is an interesting material both from the application and the basic research point of view. The PMPhSi was prepared by the Wurtz coupling polymerization [1]. The low-molecular weight fractions were extracted with boiling diethyl ether. The layers for the CL measurements were prepared from a toluene solution by casting on quartz disk substrates.
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  • Schauer, P.; Nešpůrek, S.; Schauer, F.; Autrata, R.: Cathodoluminescence Study of Silicon Polymers., Fine Mechanics and Optics, 48 (2003), 156-157.
    Abstrakt:
    First steps of cathodoluminescence (CL) study of metastable states in poly-(methylphenylsilylene), i.e. PMPhSi are presented in this paper. Besides the explanation of the experimental setup, the attention is paid to the specimen optimization. The degradation of the CL emission as a result of the formation of metastable states is shown.
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  • Schauer, P.; Autrata, R.: Performance of Detector Elements for Electron Microscopes., Fine Mechanics and Optics, 45 (2000), 268-270.
    Abstrakt:
    Signal processing in scanning and transmission electron microscopes is analysed in this paper. Distinguished are criteria of principal and commercial significance, and problematic parameters of different systems are highlighted. The most important properties of scintillation detection systems and imaging screens are discussed more in detail. For the scintillation detector, the analysis of conversion of the signal to photons, their transport from emission centres to PMT photocathode, and their conversion to photoelectrons is carried out. For the imaging screen, attention is focussed on the spectral matching and spatial resolution.
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  • Yamamoto, K.; Takayoshi, T.; Hibino, M.; Schauer, P.; Autrata, R.: Improvement of Light Collection Efficiency of Lens-Coupled YAG Screen TV System for a High-Voltage Electron Microscope., Microsc. Res. Technique, 49 (2000), 596-604.
    Abstrakt:
    A new lens coupling television (TV) system using a YAG (Yttrium Aluminum Garnet: Y3Al5O12: Ce3+) single crystal screen has been developed for a high-voltage electron microscope (HVEM), and its performance is examined. The system, using a combination of YAG and lenses, is less damaged by high-energy electron irradiation and reduces the influence of X-rays on the image. YAG screens have not been used for lens-coupling systems, because the high refractive index (n = 1.84) of YAG results in a low light collection efficiency for emitted light. This disadvantage is overcome by combining a thin YAG disk screen (thickness; 100 mu m) with a glass hemisphere whose refractive index is 1.81. We found that the light intensity is almost the same as that obtained with a conventional P22 powder screen and lenses system. The resolution is about 55 mu m on the YAG screen, and this value is 1.3 times higher than that measured by the conventional system. Shading and distortion do not affect TV observation. Detection quantum efficiency, obtained after correction of the channel mixing effect, is about 0.1.
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  • Handlir, R.; Schauer, F.; Nespurek, S.; Kuritka, I.; Weiter, M.; Schauer, P.: Metastable States in Poly(methylphenylsilylene) Induced by UV Radiation and Electron Beam., J. Non-Crystalline Solids, 230 (1998), 669-672.
    Abstrakt:
    We have examined and measured the density of states (DOS) in a prototypical poly(silylene)-poly(methylphenylsilylene) (PMPSi) using the method of post-transit hole emission signals from traps using the time of flight (TOF) photoconductivity method, The main goal of our measurements was to correlate the metastable states produced both by UV radiation and electron beam and to determine their basic parameters as to their energies and susceptibility for annealing. In the course of measurements we discovered in accordance with our previous observations the fully reversible states around and deeper than 0.55 eV.
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  • Autrata, R.; Hutař, O.; Schauer, P.: Low Voltage Single Crystal Backscatter Electron Detectors., J. Computer Assisted Microsc., 9 (1997), 105-106.
    Úvod:
    High efficiency BSE detection can be carried out using solid-state detectors, microchannel-plate detectors and scintillation detectors of different geometrical configurations. At higher beam voltages, all these detectors show sufficient efficiency. Nevertheless, if the highest possible resolution or ultrahigh resolution, depending on the signal to noise ratio are to be achieved, scintillation detectors are preferred despite their complex construction.

  • Schauer, P.; Autrata, R.: Scintillator-Photocathode Matching in Scintillation Detector for S(T)EM., J. Computer Assisted Microsc., 9 (1997), 119-120.
    Úvod:
    Besides the decay time, the efficiency is the most important parameter of a scintillation detector for a scanning electron microscope and/or a scanning transmission electron microscope - S(T)EM. Much attention has been paid to the examination of the energy conversion efficiency in scintillators (Autrata and Schauer 1996). The study of the efficiency of the light transport from scintillator luminescence centres through a light guide to a photomultiplier tube (PMT) has been accomplished too (Schauer and Autrata 1992). But nearly no effort has been devoted to the analysis of the scintillator-photocathode spectral matching. Such an analysis is the topic of this paper.
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  • Schauer, P.; Autrata, R.: Inquiry of Detector Components for Electron Microscopy., Fine Mechanics and Optics, 42 (1997), 332-334.
    Abstrakt:
    Cathodoluminescent experimental methods for the measurement of efficiencies, emission spectra and decay times of scintillators and imaging screens are presented. Pointed out are light-guiding Monte Carlo simulation methods for efficiency optimization of scintillation detection systems. Finally, sharp edge projection and Monte Carlo methods for the measurement and for the simulation of the spatial resolution of imaging screens, respectively, are described.
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  • Autrata, R.; Schauer, P.: Cathodoluminescent Properties of Single Crystal Materials for Elecron Microscopy., Scanning Microscopy (Supplement), 9 (1995), 1-12.
    Abstrakt:
    The results of measurements of cathodoluminescence efficiencies, decay characteristics and emission spectra of YAG:Ce, YAP:Ce, P47 (Y2SiO5:Ce) and CaF2:Eu single crystals at excitation by electrons with an energy of 10 keV and a current density of the order of 10-8 Acm-2 are presented. Advantages and disadvantages of the individual single crystals intended for application in electron microscopes are dealt with. Attention is paid to the PMT matching, degradation and afterglow of the mentioned single crystals. For YAG:Ce, the effect of the activator concentration of crystals and the effect of the cleaning and annealing of crystal plates are included. The proposal for the application of YAG:Ce as a scintillator and as an image screen in electron microscopy is given. Sizes of electron interaction areas and absorbed energy distributions are simulated by using Monte Carlo method based on the plural large angle elastic scattering. Cathodoluminescence widths of YAG:Ce single crystals for an impact electron in the energy range 10 - 100 keV are estimated.
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  • Autrata, R.; Schauer, P.: Collection of low energy signal electrons in the rotationally symmetric electrostatic field of a detector., Beitr. Elektr. Mikr. Direktabb. Oberfl. 26 (1993), 19-26.
    Abstrakt:
    The rotationally symmetric annular scintillator detector with a scintillation electrode held at a high voltage produces an electrostatic lens which focuses secondary electrons on the axis without their being detected. Only those electrons with a higher energy travelling at a greater distance from the axis are detected. This results in an inhomogeneous signal. Concentric dark and light circles become evident in the image. A retardation grid supplied with a low negative voltage modifies the electrostatic field so that an efficient detection of secondary electrons can be carried out, with the signal being homogeneous over the specimen surface. If the negative voltage supplied to the gird is increased, the secondary electrons are deflected so that they do not arrive at the scintillator and the given system can be used for the detection of low energy backscattered electrons.
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  • Autrata, R.; Schauer, P.: Ansammlung der Niederenergie-Signalelektronen im rotationssymmetrischen elektrostatischen Feld des Detektors., Optik (Supplement), 94 (1993), 26.

  • Hibino, M.; Irie, K.; Autrata, R.; Schauer, P.: Characteristics of YAG Single Crystals for Electron Scintillators of STEM., J. Electron. Microsc., 41 (1992), 453-457.
    Abstrakt:
    Scintillators made of powder phosphor have been usually used for the detection of signal electrons in SEM and STEM. Single crystals of YAG, developed and applied to scintillators of SEM, were studied experimentally at the accelerating voltage of 100 kV and 1 MV for scintillators of STEM and sequential EELS. Measurements were carried out for the evaluation of scintillation characteristics of YAG single crystals and conventional powder phosphors on the light intensity guided to a photomultiplier tube, resistance to electron irradiation, spatial uniformity in light intensity and the afterglow in the seconds to minutes range. The characteristics of YAG single crystals were found to be preferable to those of powder phosphors at 1 00 kV and 1 MV.
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  • Schauer, P.; Autrata, R.: Light Transport in Single-Crystal Scintillation Detectors in SEM., Scanning, 14 (1992), 325-333.
    Abstrakt:
    A Monte Carlo simulation method was developed to determine the efficiency of photon transport through a modified rotationally symmetric Everhart-Thornley detector. The method makes use of the random generation of photon emission from a luminescent centre and describes the trajectory of photons and the efficiency of their transport toward the photocathode of the photo-multiplier tube. The model includes photon generation in a point source, mirror reflection by a metal-coated surface, Fresnel reflection by a metal-uncoated surface, Fresnel passage through the boundary of different materials, diffusion reflection, and passage through a matted surface and optical absorption in material. For the simulation, an IBM-PC-compatible program was written and applied to detection systems with disc, conical, and hemispherical YAG:Ce single-crystal scintillators with cylindrical or tapered light guides or without any light guide. The model was verified by measuring the efficiency of detection systems excited by the primary electron beam in the line-scan SEM mode.
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  • Autrata R., Schauer P.: Monokrystalická stínítka pro převadeč nízkoenergiového elektronového obrazu., Jemná Mech. Opt., 36 (1991), 133-138.

  • Autrata R., Schauer P., Kvapil Ji., Kvapil Jos.: Die Anwendung der Einkristall-Scintillatoren und Sichtschrime in Elektronenmikroskopen., Beitr. Elektronenmikroskop. Direktabb. Oberfl., 18 (1985), 97.

  • Autrata R., Schauer P., Kvapil Jos., Kvapil Ji.: Single crystal aluminates - a new generation of scintillators in SEM and transparent screens in electron optical devices., Scanning Electron Microsc., (1983), 489-500.
    Abstrakt:
    Scintillators and transparent screens are described which are based on single crystals of yttrium aluminium garnet (YAG) and yttrium aluminium perovskite (YAP) activated by trivalent cerium. Their relative efficiency is compared with the powder P 47 scintillators. The detective quantum efficiency (DQE) coefficient was measured as 0.8 for YAG (versus 0.6 for P 47). Their advantage is the high resistance to radiation damage. Decay time of the luminescence is suitable for TV frequencies (YAG is 80 ns, YAP is 40 ns). It is possible to use single-crystal scintillators in devices with ultrahigh vacuum conditions without difficulty. Spectral characteristics of YAP are matched to the maximum spectral sensitivity of photomultipliers with photocathodes S 11 or S 20. The use of photocathode S 20 is preferable for YAG which has a longer wavelength of characteristic emission (560 nm). YAG can be used as a transparent screen in various electron optical devices. Its efficiency is lower than that of powder screens, but it has a high resolution. It is capable of withstanding high power loading of the electron beam. The thinnest screen produced to date is 35 µm. Other parameters are identical with those of scintillators. YAG and YAP single crystals can be machined in different forms suitable for implementation of the backscattered electrons (BSE) detector. A double detector has been developed for secondary electrons (SE) or BSE detection which is connected to one photomultiplier. The detector makes it possible to choose detection of signal electrons of different types and can be used in any SEM.
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  • Autrata R., Schauer P., Kvapil Ji., Kvapil Jos.: Cathodoluminescence efficiency of Y3Al5O12 and YAlO3 single crystal in dependence on Ce3+ and other dopants concentrations., Cryst. Res. Technol., 18 (1983), 907.
    Abstrakt:
    The content of Ce3+ ions in the investigated single crystals grown under reducing conditions is limited by a low value of the distribution coefficient. This distribution coefficient decreases sharply with increasing concentration of Ce3+ ions in a melt. Cathodoluminescent efficiency rises with increasing Ce3+ concentration up to a certain state of saturation. At higher concentrations of Ce3+ ions emission from activator centres is dominant, while at lower concentrations defect centres play an important part. Iron acts as a strong quenching centre, especially in the YAlO3 lattice. Nd, Ir, Fe, Ti, Cr centres exhibit a high quenching effect, too. A trace amount of Mo enhances cathodoluminescent efficiency.
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  • Autrata R., Schauer P., Kvapil Ji., Kvapil Jos.: A Single crystal of YAlO3:Ce3+ as a fast scintillator in SEM., Scanning, 5 (1983), 91-96.
    Abstrakt:
    A new single-crystal scintillator intended for applications in a scanning electron microscope (SEM) is presented. It is a single-crystal disc of yttrium aluminium perovskite activated by trivalent cerium free of traces of Fe ions. The single crystals of YAlO3:Ce3+ (YAP: Ce3+) were prepared by the Czochralski method in a reducing atmosphere of Ar and H2 with an excess amount of Y3+ ions. Effective methods of purification and purity control of the raw material are described. The highest achievable concentration of Ce3+ ions in as grown crystals amounted to 0.3 wt%, concentration in the melt was 8-9 times higher. The best properties were found with samples of the maximum possible concentration of Ce3+. Compared with the previous aluminate Y3Al5012:Ce3+ (YAG: Ce3+) these samples showed higher efficiency, a shorter decay time of luminescence (40 ns) and an emission band in a more advantageous spectral region (378 nm). Because of high resistance to radiation damage, high chemical resistance and applicability to ultra-high vacuum it is also suitable for detection of other kinds of ionizing radiation.
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  • Kvapil Ji., Perner B., Kvapil Jos., Manek B., Kubelka J., Blazek K., Autrata R., Schauer P., Vitamvas Z.: Spectral properties of oxide crystals free of iron ions., Cryst. Res. Technol., 17 (1982), 885.
    Abstrakt:
    Al2O3 and YAG crystals were purified from traces of iron by the growth in reducing atmosphere. Luminescence output of such materials was substantially increased, but some undesirable properties as transient colour centre formation in YAG: Nd and low damage threshol of ruby laser rods were observed. Minimum concentration of iron ions which drastically change spectral properties of oxide crystals seems to be <= 10-4 wt%.
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  • Kvapil Ji., Kvapil Jos., Manek B., Perner B., Autrata R., Schauer P.: Czochralski growth of YAG:Ce in reducing protective atmosphere., J. Cryst. Growth, 52 (1981), 542.
    Abstrakt:
    Ce3+ ions cause the destruction of colour centres in YAG crystals grown under a reducing protective atmosphere. The more transparent Ce3+ -doped YAG crystals have a relatively large region submerged in the melt and form a strongly conical interface during growth. This phenomenon brings about the possibility of the growth of relatively perfect crystals. Using molybdenum crucibles, the crystals are free from impurities which cause luminescence quenching of Ce3+ and, after oxygen annealing, they may be used as efficient cathode-ray excited phosphors.
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  • Kvapil Jos., Kvapil Ji., Blazek K., Zikmund J., Autrata R.,Schauer P.: The luminescence efficiency of YAG:Ce phosphors., Czech. J. Phys. B, 30 (1980), 185.
    Abstrakt:
    The luminescence intensity of Yttrium aluminium garnet activated by the Ce3+ (YAG:Ce3+) under cathode-ray excitation depends on the preparation method and content of some dopants. Samples containing Fe, Pt, Ir or some colour centre, respectively, show relatively low luminescence. The maximum luminescence intensity was obtained with the Czochralski method grown single crystals in 98% Ar+2% H2 atmosphere which were sensitized by oxygen annealing followed by treatment at 1500 °C in molybdenum container using a wet hydrogen atmosphere.
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  • Schauer P., Autrata R.: Electro-optical properties of a scintillation detector in SEM., J. Microsc. Spectrosc. Electron., 4 (1979), 633.
    Abstrakt:
    Possibilities of sensitivity increase of a scintillation detector of electrons are discussed on the basis of analysis of its optical properties. Light signal losses due to imperfect guiding of light from luminescent centres of a scintillator to photoemissive centres of a photocathode of a photomultiplier are analysed. From this point of view different types of scintillators and light-guides are compared. A special attention is paid to a new fast transparent single-crystal scintillator of yttrium aluminium garnet activated by cerium (YAG:Ce3+). Different surface finishes of this scintillator are investigated and a solution in the form of a disc with matted base is presented. Optimum choice of a photomultiplier tube with respect to the emission spectrum of the scintillator is also discussed and experimentally verified.
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  • Autrata R., Schauer P.: Optoelektronika v elektronové mikroskopii., Slaboproudý obz., 39 (1978), 472.

  • Autrata R., Schauer P., Kvapil Jos., Kvapil Ji.: A single crystal of YAG:Ce - new fast scintillator in SEM., J. Phys E: Sci. Instrum., 11 (1978), 707.
    Abstrakt:
    The scintillator is the basic element of an electron detector in a scanning electron microscope (SEM). It transforms the energy of secondary or backscattered electrons (produced by the interaction of the primary-electron beam with the specimen) into photon energy. The generated light quanta are detected by a sensitive, spectrally adapted photomultiplier. The scintillator and photomultiplier form a detection system which should meet the following demands: high quantum efficiency, low noise, high bandwidth, large dynamic range and long lifetime. Not all scintillation materials used to date comply with these requirements.
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  • Autrata R., Schauer P.: Scintilátory pro rastrovací elektronový mikroskop., Slaboproudý obz., 38 (1977), 511.
    Abstrakt:
    Článek je věnován přehledu nejdůležitějších parametrů scintilačních látek, vhodných pro použití v rastrovací elektronové mikroskopii, se zvláštním zřetelem na scintilátory pro rastrovací elektronovou mikroskopii s autoemisní tryskou. Zabývá se přehledem a srovnáním současného stavu scintilačních látek vlastní výroby a přináší první zmínku o nově vyvinutém scintilátoru - monokrystalu ytrium hliníkového granátu. Cílem je podat základní informaci uživatelům elektronově mikroskopických zařízení při aplikaci scintilačních látek.
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  • Žák J., Schauer P.: Stanovení termofyzikálních vlastností brambor metodou impulsně působícího přímkového zdroje tepla., Zemědělská technika, 22 (1976), 23.

  • Schauer P.: Napěťová závislost kapacity anodicky oxidovaného systému Al-Al2O3-Al., Cs. cas. fys. A, 21 (1971), 257.

 

PUBLIKACE VE SBORNÍCÍCH
Podrobnosti o vlastních publikacích ve sbornících kongresů a konferencí. Seřazeno od novějších.


  • Schauer, P.; Lalinsky, O.; Kucera, M.; Lucenicova, Z. Superfast scintillators for SEM electron detectors. MCM2017 - 13th Multinational Congress on Microscopy, Rovinj, Croatia, Sept 2017, Proceedings, p.132-134.
    Úvod:
    Scanning electron microscopes (SEM) require a high-quality electron detector. Such an electron detector must primarily be very fast to process a large number of imaging data in real time. For example, for the acquisition of a high-quality image in a scanning electron microscope (SEM) in real time, it is usually required to process each pixel in less than 100 ns without a loss of contrast. If the mentioned electron detectors are to be formed by scintillation detection systems, they must be equipped with very fast scintillators having a short decay time (decay to 1/e value, where e is the base of natural logarithms) and low afterglow even at a microsecond time range after an excitation cut-off. The scintillator with the long decay time causes an image blur and the scintillator with the high afterglow reduces image contrast in the SEM.
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  • Lalinsky, O.; Schauer, P.; Lucenicova, Z.; Kucera, M. Improved cathodoluminescence performance of Mg-doped LuAG:Ce(GdGa) single crystalline films. SCINT 2017 - 14th Int. Conference on Scintillating Materials and their Applications, Chamonix, France, Sept 2017, Proceedings.
    Úvod:
    For the purpose of this work, set of Mg2+-doped LuAG:Ce and set of Mg2+-doped LuAG:CeGdGa multicomponent epitaxial films (thickness around 17 µm) with different Mg concentration (0-700 ppm) were grown from lead-free BaO-B2O3-BaF2 flux. The films were excited by an e-beam with energy of 10 keV using a specialized CL apparatus. The CL spectra, CL decays under nanosecond and millisecond excitation and thermoluminescence glows in the temperature range between 100 and 490 K were obtained.
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  • Schauer, P.; Lalinsky, O.; Lucenicova, Z.; Kucera, M. Multicomponent garnet film scintillators for SEM electron detectors. EMC 2016 - The 16th European Microscopy Congress 2016, doi: 10.1002/9783527808465.EMC2016.5236, Lyon, France, Aug 2016, Proceedings, p. IM03-232.
    Úvod:
    With an Everhart-Thornley (ET) scintillation detector in SEM, an image is formed by signal electrons emerged after an interaction of focused scanning electron beam with the specimen surface. In such a case a scintillator plays an important role as a fast electron-photon signal conversion element. A selection of fast scintillation materials is very limited, because the only mechanism for scintillators applicable in SEM ET detectors consists in allowed 5d-4f transitions in lanthanide ions. Unfortunately, the widely used Czochralski grown single crystal YAG:Ce scintillators suffer from an afterglow, which deteriorate the ability to transfer high image contrast. The mentioned afterglow in the bulk single crystal is caused by inevitable structural defects, such as antisite defects. These trap states are responsible not only for delayed radiative recombination causing the afterglow, but also for a degradation of the light yield. The aim of this study is to introduce new multicomponent garnet film scintillators for SEM electron detectors that due to the substitution of Al by Ga in the Gd3Al5O12:Ce garnet extensively supress the shallow traps resulting in a significant increase of the cathodoluminescence (CL) efficiency and in improvement of the afterglow characteristics.
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  • Lalinsky, O.; Schauer, P.; Kucera, M.; Lucenicova, Z.; Hanus, M. Prospective scintillators for low-energy BSE detectors. EMC 2016 - The 16th European Microscopy Congress 2016, doi: 10.1002/9783527808465.EMC2016.6239, Lyon, France, Aug 2016, Proceedings, p. MS07-897.
    Úvod:
    Cerium activated bulk single crystals of yttrium aluminium garnet (YAG:Ce) Cex:Y3-xAl5O12 are widely used as scintillators for the detection of backscattered electrons (BSE). In the electron microscopy research of nanomaterials, biomaterials or semiconductors, low energy (units of keV) electron beam imaging is often necessary. Because BSE detectors are mostly non-accelerating or low-accelerating, electrons with approximately the same energy as primary beam (PB) have to be detected. 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 YAlO3:Ce (YAP:Ce) and CRY018 can be predicted. However, similar LY sink can be expected also with these scintillators.
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  • Lalinsky, O.; Schauer, P.; Kucera, M.; Lucenicova, Z.; Hanus, M. Effect of Mg-doping on cathodoluminescence properties of GAGG:Ce single crystalline films. ICDIM 2016 - International Conference on Defects in Insulating Materials, Lyon, France, July 2016, Proceedings, p. Th-P-28.
    Úvod:
    Cerium activated single crystals of gadolinium aluminum gallium garnet (GAGG:Ce) are prospective scintillation materials thanks to their high light yield of 50-60 kPh/MeV and fast luminescence decay with a short decay time of 50-80 ns. However, such decay time can be still too high, for example, for special SEM applications where the very fast e-beam scanning is required. Thus, new materials with faster decay have to be found. For this purpose, Mg-doped specimens of the GAGG:Ce multicomponent epitaxial films with different concentration of Mg were grown from lead-free BaO-B2O3-BaF2 flux.
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  • Lalinsky, O.; Schauer, P.; Kucera, M.; Hanus, M.; Lucenicova, Z. New detectors for low-energy BSE. 15th Inter. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalsky Dvur (Brno) May 2016, Proceedings, p.34-35.
    Úvod:
    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) Cex:Y3-xAl5O12 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) CexY1-xAlO3 and CRY018 can be predicted. However, similar LY drop can be expected also with these scintillators.
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  • Lalinsky, O.; Schauer, P.; Kucera, M.; Onderisinova, Z.; Hanus, M. Cathodoluminescence study of LuAG:CeGdGa single crystalline films., ICOM 2015 - The 4th International Conference on the Physics of Optical Materials and Deices, Budva, Montenegro Aug 2015, Proceedings, p. 125.
    Úvod:
    Cerium activated single crystals of lutetium aluminum garnet (LuAG:Ce) are prospective scintillation materials for detection of X-rays, gamma rays or high energy particles [1]. However, the LuAG:Ce single crystals usually contain various unwanted structural defects (mainly antisite defects) which can result in nonradiative recombination and in delayed luminescence decay (afterglow). It was shown previously [2] that the concentration of these defects decreases with the decreasing temperature of the crystal growth. Therefore, single crystalline epitaxial films have attracted a lot of attention recently because the growth temperature of LuAG:Ce films is about a half (1000 °C) of the bulk ones (2000 °C). Although some new defects can be created due to strain in the film, the concentration of the antisite defects is highly reduced, as shown in this work. Moreover, the influence of Gd and Ga substitution on the cathodoluminescence (CL) properties was studied.
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  • Onderisinova, Z.; Kucera, M.; Hanus, M.; Lalinsky, O.; Bok, J.; Schauer, P.; Nikl, M. Cathodoluminescence decay kinetics of Ce3+ doped LuAG:GdGa multicomponent garnets., SCINT 2015 - 13th International Conference on Inorganic Scintillators and Their Applications, Berkeley, USA June 2015, Proceedings, p. O5-6.
    Úvod:
    Ce3+ doped single crystal aluminum garnet Lu3Al5O12 (LuAG) belongs to the group of high figure of merit scintillators. However, the main disadvantage of this material, having a promising light yield of 26 kPh/MeV [1], is presence of slow components in the scintillation response. Undesirable structural defects, identified as antisite defects, are responsible for slow component in scintillation decays and degrade this compound in applications where fast response is required. Therefore, a new material Gd3Ga3Al2O12:Ce multicomponent garnet has been recently designed [2] and demonstrated positive influence of Gd3+ and Ga3+ substitution on the light yield.
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  • Kucera, M.; Onderisinova, Z.; Hanus, M.; Prusa, P.; Bok, J.; Schauer, P.; Lalinsky, O.; Nikl, M. Improved scintillation response of Ce doped GGAG garnet films: A pathway to high LY materials. SCINT 2015 - 13th International Conference on Inorganic Scintillators and Their Applications, Berkeley, USA June 2015, Proceedings, p. O14-1.
    Úvod:
    Recently, a new concept of Ce3+ doped multicomponent aluminum garnets, (GdYLu)3(GaAl)5O12:Ce, has been proposed with partial substitution of Gd and Ga for (Y, Lu) and Al ions, respectively, where detrimental effect of shallow traps is significantly reduced [1]. Due to the combined substitution of Gd and Ga, the shallow traps are extensively suppressed and these systems have excellent LY, two times higher than LuAG:Ce or YAG:Ce. The aim of this work is detailed study of shallow traps in Ce3+ doped multicomponent (GdLu)3(GaAl)5O12:Ce garnets and their impact on the scintillation properties (scintillation efficiency and timing characteristics) of this material. Due to the technological breakthrough in the liquid phase epitaxy high purity single crystalline films were grown from the lead-free BaO-B2O3-BaF2 flux with special emphasis on elimination of potential impurities coming from the flux. The thickness of films was 10 – 30 µm. Combined experimental study of photoelectron yield (under alpha excitation), decay kinetics of delayed recombination in the millisecond time range (under e-beam excitation), and cathodo- and radio-luminescence spectroscopies were used in the study.
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  • Schauer, P.; Bok, J. Innovation possibilities of scintillation electron detector for SEM. IMC 2014 - The International Microscopy Congress 2014, Prague, Czech Rep. Sep 2014, Proceedings/Vol. IT-4, p. O-1674.
    Úvod:
    To evaluate performance of a scintillation detection system for SEM, it is necessary to consider many scintillator parameters. Various attributes of the scintillator for the SEM electron detector are listed in Fig. 1. The very important parameters are those affecting the detective quantum efficiency (DQE) which is primarily a measure of image noise. Not a less important indicator of image quality is the modulation transfer function (MTF) which describes the ability to show fine image details. Therefore, using a scanning imaging system, the detector bandwidth, which is given especially by the scintillator decay time, is the key to the good MTF. Currently, the YAG:Ce single crystal scintillator (introduced already in 1978 [1]) having somewhat limiting decay characteristic is the most frequently used scintillator in the SEM. The aim of this paper is to outline possibilities of scintillator innovation to get the improved MTF and DQE.
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  • Lalinsky, O.; Bok, J.; Schauer, P.; Frank, L.: Performance of YAG:Ce scintillators for low-accelerating electron detectors in S(T)EM. IMC 2014 - The International Microscopy Congress 2014, Prague, Czech Rep. Sep 2014, Proceedings/Vol. IT-4, p. P-3232.
    Úvod:
    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.
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  • Bok, J.; Schauer, P. Effect of oxidation annealing at different temperatures on cathodolu minescence properties of YAG:Ce single crystals. ICL 2014 - 17th International Conference on Luminescence and Optical Spectroscopy of Condensed Matter, Wroclaw, Poland, July 2014, Proceedings, p. P-180.
    Úvod:
    The cerium-activated yttrium aluminium garnet (YAG:Ce, chemical formula Y3-xCexAl5O12) is frequently used as a yellow-green emitting scintillator for high-energy particle detectors, or as a phosphor for white-light emitting LED sources [1]. The popularity of this material consists in its relatively fast decay, high light yield, good mechanical properties and low production costs. However, the YAG:Ce single crystals usually contain various unwanted structural defects which can result in non-radiative recombination and in delayed luminescence decay (afterglow). Thus, an effort is put into decreasing the concentration of material defects, which could bring desired increase of the light yield and reduction of the afterglow.
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  • Lalinsky, O.; Bok, J.; Schauer, P. Temperature-dependent study of cathodoluminescence intensity and decay of cerium-activated YAG single crystals. ICL 2014 - 17th International Conference on Luminescence and Optical Spectroscopy of Condensed Matter, Wroclaw, Poland, July 2014, Proceedings, p. P-205.
    Úvod:
    Yttrium aluminium garnet (YAG) Y3Al5O12 is a crystalline material of the garnet group. Ce - activated YAG (YAG:Ce) gains very useful properties in comparison to the Ce-free one, and therefore YAG:Ce is used for example as a phosphor in white light - emitting diodes or as a scintillator material. 35 years ago, Robbi ns et al. published series of successful papers studying cathodoluminescence (CL) properties of rare-earth activated YAG crystals. Their previous work has been successful and often cited till now, because there is no so complex work dedicated to CL study of YAG:Ce . However, as Robbins et al. admit, their results are distorted by some inadvertent impurities in the initial material for YAG:Ce single crystal growth. Unlike that time, nowadays there are more advanced technologies of YAG:Ce single crystal growth, which focus on material purity and defect-free crystal structure of the garnet. Meanwhile, there have been improved ways how to study CL properties to reach significantly better results, such as higher spectral and time resolution or higher dynamic range of a detector. This induces a requirement to revise and improve studies of Robbins et al.
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  • Kucera, M.; Onderisinova, Z.; Bok, J.; Hanus, M.; Nikl, M.; Schauer, P. Scintillation Response of Ce3+ Doped GdGa-LuAg Multicomponent Garnet Films Under Electron Excitation. ICL 2014 - 17th International Conference on Luminescence and Optical Spectroscopy of Condensed Matter, Wroclaw, Poland, July 2014, Proceedings, p. O-43.
    Úvod:
    Ce3+ doped aluminium garnets, YAG:Ce, LuAG:Ce, are prospective scintillation materials for detection of gamma rays or high energy particles. Thin single crystalline films have potential application in high resolution screens for electron or X-ray detection. The light yield of these garnet materials is, however, degraded by inevitable structural defects which result in trap states and appearance of slow light (delayed components) in scintillation decays. Recently, a new concept of multicomponent aluminium garnets has been proposed with partial substitution of Gd and Ga for (Y,Lu) and Al ions, respectively, where detrimental effect of shallow traps is significantly reduced.
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  • Bok, J.; Schauer, P: Mechanism of electron-photon conversion in YAG:Ce scintillator for SEM electron detectors. MC 2013 - Microscopy Conference 2013, Regensburg, Germany, August 25-30, 2013, p. 121-122.
    Úvod:
    The Everhart-Thornley imaging detector is commonly used one in SEM. In such a detector, the signal electrons are accelerated towards a conductively coated scintillator where they are converted to the visible photons within the cathodoluminescence (CL). The emitted photons are guided out of a vacuum chamber and detected by a photon detector. The scintillator is still a bottleneck of the signal electron detector, because its CL properties can highly affect the scanned image quality. For example, low CL efficiency of the scintillator can result in poor signal-to-noise ratio of the detector. Also long CL decay time can decrease the image contrast during the fast scanning. These problems highly motivate to clearly understand how the energy of the signal electron is converted in the scintillator. This knowledge is essential for modification of the scintillator properties in order to improve the SEM image quality.
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  • Bok, J.; Schauer, P: Two-state model for cathodoluminescence kinetics of YAG:Ce single-crystal scintillators. Scint 2013 - 12th International Conference on Inorganic Scintillators and Their Applications, Shanghai, China, April 15-19, 2013, p. 18.
    Úvod:
    In a scanning electron microscope (SEM), a scintillator is used to detect free electrons reflected from an observed specimen. It is demanding to detect individual electrons with energies below, for example, 20 keV, therefore the current of many electrons is usually detected. In order to understand behavior of scintillators in the SEM, cathodoluminescence (CL) of the scintillator excited by an e-beam pulse is studied.
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  • Schauer, P.; Bok, J.: Current state and prospects of scintillation materials for detectors in SEM. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalský Dvůr (Brno) June 2012, Proceedings, p.67-68.
    Úvod:
    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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  • Bok, J.; Schauer, P: Quality assessment of scintillation detector in SEM using MTF. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalský Dvůr (Brno) June 2012, Proceedings, p.9-10.
    Úvod:
    One of the recent trends in S(T)EM is increasing of the e-beam scanning speed. In general, higher speeds decrease object degradation and prevent image artifacts caused by slow electrical discharging. However, the increase of the scanning speed is limited by the time response of the signal-electron detector. When the detector response is slower than the scanning speed, it can have negative influence to the quality of the scanned image, such as contrast reduction and image blurring. Usually, the rise and fall edges of the time response curve to a square electron pulse have more complex form, such as a multi-exponential function of time. Evaluate and compare the time-dependent edges in context of their influence on the image quality is rather complicated. Therefore, we propose to express the detector time response by the modulation transfer function (MTF), which contains all relevant information. It can give the answer to the important question, what maximum scanning speed can be used not to significantly decrease the image quality.
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  • Bok, J.; Schauer, P: Afterglow of YAG:Ce single crystal scintillators for S(T)EM electron detectors. MCM 2011 - 10th Multinational Congress on Microscopy 2011, Urbino, Italy Sept 2011, Proceedings, p.61-62.
    Úvod:
    One of the most used electron detection systems in S(T)EM is a system based on a scintillator-photomultiplier combination. As scintillation properties of the system can highly affect scanned image quality, many requirements are placed on the scintillator. One of the requirements is short time response of a light emission pulse. The time response of scintillators usually follows sum of exponential decays with fast as well as with slow components. The fast components are usually short enough to meet a typical scanning speed, however the slow ones can cause an undesirable afterglow. This can have a negative influence to the quality of the scanned image, such as image contrast decreasing and image blurring.
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  • Schauer, P.; Schauer, F.; Kuritka, I.; Nespurek, S. Cathodoluminescence study of electron beam formed defects in polysilanes. MC 2009 - Microscopy Conference 2009, Graz, Austria Sept 2009, Proceedings/Vol. 3, p.383-384.
    Úvod:
    In materials science and semiconductor engineering, cathodoluminescence (CL) is a very efficient tool for the study of electronic substance structure and application possibilities. In spite of this, CL is only very rarely used for investigation of polymers. Recently Wellman et al introduced CL as an important tool for the investigation of materials for organic electroluminescence devices. It is evident that CL may become a strong tool for the investigation of polymer light emission possibilities as well as for investigation of triplet harvester organic solar cells. Our interest has been focused on the group of polysilanes (often also called polysilylanes), especially on poly[methyl(phenyl)silane] (PMPSi), having linear backbone of linked silicon atoms. Cathodoluminescence study of electron beam formed defects in PMPSi is presented in this paper.
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  • Bok, J.; Schauer, P. LabVIEW controlled cathodoluminescence equipment. MC 2009 - Microscopy Conference 2009, Graz, Austria Sept 2009, Proceedings/Vol. 1, p.55-56.
    Úvod:
    Cathodoluminescence (CL) is an opto-electronic phenomenon of a large number of solids, when an incident electron beam causes the light emission. This phenomenon is widely utilized in electron beam instruments (for example in the SEM) not only for a scintillation electron detector, but also as a significant imaging and analyzing SEM mode. So, the topic of CL is an important method for understanding of transition effects and of other processes not only in scintillators, but also in many other solids studied.
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  • Schauer, P.; Horak, P.; Schauer, F.; Kuritka, I.; Nespurek, S. Study of degradation and regeneration of silicon polymers using cathodoluminescence. EMC 2008 - 14th European Microscopy Congress, Aachen, Germany Sept 2008, Proceedings/Vol. 2, p.789-790.
    Úvod:
    Silicon polymers are widely studied materials in recent years, because they show very promising properties for the application in electronics. Their properties such as phase of matter, thermochromism, piezochromism, semiconductivity, photoreactivity, light emission and optical nonlinearity, have become very interesting. Our interest has been focused on the group of polysilanes (often also called polysilylenes), especially on poly[methyl(phenyl)silylene] (PMPhSi), having linear backbone of linked silicon atoms. Cathodoluminescence (CL) degradation and regeneration of PMPhSi are presented in this paper.
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  • Horák, P.; Kuřitka, I.; Schauer, P.; Schauer, F.; Sáha, P. Mechanism of poly[methyl(phenyl)silylene] e-beam degradation. 3rd European Weathering Symposium Natural and Arteficial Ageing of Polymers, Krakow Sept 2007, Proceedings, p.97-107.
    Úvod:
    The susceptibility to material degradation is a characteristic property of polysilylenes (PSi). PSi are degradable for example by ultraviolet (UV) radiation or by electron beam (EB). The degradation of the material decreases intensity of luminescence, which impedes the utilization of PSi as an active emissive layer in organic light emitting diodes. Poly[methyl(phenyl)silylene] (PMPSi) was selected as a typical representative of PSi. A cathodoluminescent (CL) device developed in our laboratory was used for integral and spectral study of PMPSi. CL spectrum of PMPSi corresponds to photoluminescence (PL) emission spectrum of the same material. UV emission decreases rapidly with the degradation, whereas visible one remains nearly stable during EB irradiation. The UV emission is related to the silicon (Si) backbone. The visible emission is related to the existence of weak bonds (WBs) and other defects on Si backbone. Infrared (IR) absorption spectroscopy was used to identify material changes caused by the EB degradation. IR spectra of PMPSi support the idea of Si-Si bonds deformation in the main chain of the material during the EB degradation. EB irradiation of PMPSi leads to the creation of WBs in early stages of the degradation followed by the creation of dangling bonds (DBs). DBs are proved by new absorption bands in IR spectra after exposure of EB degraded PMPSi to air and moisture. PMPSi degradation by EB corresponds to PMPSi degradation by low energy photon UV radiation (355 nm). The result indicates the same or very similar mechanism of the material degradation. According to the CL study, PMPSi with the susceptibility to EB degradation seems to be applicable as a resist in EB lithography.

  • Schauer, P. Enhancement of single crystal scintillators for scintillation detectors in S(T)EM. 8th Multinational Congress on Microscopy, Prague, Czech Rep. June 2007, Proceedings, p.105-106.
    Úvod:
    Scintillator is a problematic part of any scintillation detector for S(T)EM. The reason lies in its decay time and especially in its afterglow, which deteriorate the ability to transfer image contrast. In other words, a slow scintillator causes a bad modulation transfer function (MTF) of the whole detector. If a series of alternating white and black points is transferred using such a scintillator, the image is somewhat degraded at the typical S(T)EM spatial frequency. To enhance the MTF of the detector, the kinetics of the cathodoluminescence (CL) of many single crystal scintillators has been studied at our laboratory. Some results concerning single crystals of cerium-activated yttrium aluminum garnet (YAG:Ce) and cerium-activated yttrium aluminum perovskite (YAP:Ce) are presented in this paper.
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  • Horák, P.; Schauer, P. Analysis of electron beam degraded poly[methyl(phenyl)silylene]. 8th Multinational Congress on Microscopy, Prague, Czech Rep. June 2007, Proceedings, p.257-258.
    Úvod:
    Polysilanes (PSi) [1] are a broad class of organic materials whose basic building block is a chain built up of silicon. The susceptibility to material degradation is a characteristic property of PSi. PSi are degradable for example by ultraviolet (UV) radiation [2] or by electron beam (EB) [3]. The degradation of the material decreases intensity of luminescence. Poly[methyl(phenyl)silylene] (PMPSi) was selected as a typical representative of PSi.
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  • Horák, P.; Schauer, P.: Effect of Electron Beam on Poly[Methyl(Phenyl)Silylene]. Mikroskopie 2006, Nové Město na Moravě, February 2006, Proceedings, p.33.
    Úvod:
    The study of the properties of poly[methyl(phenyl)silylene] (PMPSi) was based on the measurement of intensity of the cathodoluminescent (CL) emission after passing through the specimen. The study of the PMPSi properties using the CL method is complicated by the material degradation characterized by the fall of the CL intensity. Therefore, the measurement in the synchronous mode was used to eliminate the influence of the background and of the noise. At the excitation energy of 10 keV the irradiation time dependence of the PMPSi CL intensity was measured for the different electron beam current densities. For the highest current density, both the strongest intensity and the fastest fall have been observed. The speed of degradation depends on the irradiation time as well as on the current density of the excitation beam. The effect mentioned impedes the utilization of PMPSi as a detecting or signalizing element. On the other hand, the degradation of PMPSi could be utilized in electron lithography.
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  • Schauer, F.; Kuřitka, I.; Zemek, J.; Horák, P.; Schauer, P.; Sáha, P.: Polysilanes for Nanorezists: Photoelecton Spectroscopy, UV and Electron Beam Degradation. 5th Int. Conference - Solid State Surfaces and Interfaces, Smolenice , Slovak Republic, November 19-24, 2006, (Edited and Published by Institute of Physics, SAS, Nov. 2006), p. 83.

  • Schauer, P.: Decay Time Optimization of YAG:Ce Scintillator for S(T)EM Electron Detector. IMC 16 - 16th International Microscopy Congress, Sapporo, Japan, September, 2006, Proceedings/Vol. 2, p.665.
    Úvod:
    The process of optimization of a scintillation electron detector for S(T)EM offers many options such as the optimization of electron collection, electron-photon conversion, photon collection, as well as of photon-electron conversion. In addition to the electron-photon conversion efficiency and to the photon transport efficiency, also kinetic properties of a scintillator are of great importance in an Everhart-Thornley scintillation detection system. This is because the decay time of the scintillator strongly influences the detective quantum efficiency (DQE), which is the most important criterion of quality of the whole detector. If the detector is to suit the TV rates, the decay time of the scintillator must be shorter than 100 ns. Kinetic properties of many single crystal scintillators were measured at our laboratory, and single crystals of YAG:Ce, YAP:Ce, and P47 were chosen as the most interesting ones for electron microscope detectors. Of the crystals mentioned, the YAG:Ce is the cheapest one and so its usage is widespread. However, its decay time is often longer than 100 ns, and moreover, its decay characteristic is multi-exponential with afterglow of 2 % at 5 µs after the end of excitation. Two possibilities of decay characteristic optimization of YAG:Ce single crystals are presented in this paper.
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  • Schauer, P.: Decay Kinetics of Scintillation Crystals for SEM Electron Detectors. 10th Inter. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalský Dvůr (Brno) May 2006, Proceedings, p.63-64.
    Úvod:
    The principal quantities of image quality in SEM are contrast, spatial resolution, and noise. However, to quantify the overall performance of an imaging system, the detective quantum efficiency (DQE) is a better tool as it includes both the modulation transfer function and the noise power spectrum. This means that for a detector to have high DQE, it should possess not only high efficiency and low noise, but also good kinetic properties. A study of the decay kinetics of some single crystal scintillators for SEM is presented in this paper.
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  • Schauer, P.; Autrata, R.: Extended Algorithm for Optimization of Photon Transport in Scintillation Detector. Dreiländertagung Microscopy Conference 2005, Davos, Switzerland Aug 2005, Proceedings, p.55.
    Úvod:
    To avoid inefficiency and inhomogeneity of BSE scintillation detection systems, efficient transport of photons from luminescent centres in a scintillator to a photocathode of a photomultiplier tube must be provided. Optimization of the photon transport of a rotationally symmetric Everhart-Thornley detector is quite a feasible task, because a code for the Monte Carlo (MC) simulation is based on the system geometry which is a function of one variable coordinate. For such a rotationally symmetric detection system the previous MC code Scintil [1] was developed in our laboratory. The Scintil code includes photon generation in a point source, mirror reflection by a metal coated surface, Fresnel reflection by a metal uncoated surface, Fresnel passage through the boundary of different materials, diffusion reflection and passage through a matted surface and optical absorption in material.
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  • Horák, P.; Schauer, P.: Degradation of Poly[methyl(phenyl)silylene] cathodoluminescence. 2nd European Weathering Symposium - Natural and Artificial Ageing of Polymers, Gothenburg, Sweden June 2005, Proceedings, p.311-319.
    Úvod:
    The study of the properties of Poly[methyl(phenyl)silylene] (PMPSi) was based on the measurement of intensity of the cathodoluminescent (CL) emission after passing through the specimen. The major problem of the study is the susceptibility of the material investigated to the degradation by electron beam. PMPSi degradation strongly decreases the CL intensity (to 40% after five minutes from the beginning of the excitation). Therefore, the measurement in the synchronous mode was used to eliminate the influence of the background and of the noise. An interaction of electrons with PMPSi causes the progressive scission of weak Si - Si bonds in the main chain of the material and leads to the formation of silyl radicals. A series of subsequent reactions of the radicals is possible, which complicates the process of degradation. It was found that the degradation process is partly reversible. A partial recovery of intensity was attributed to reverse recombination reactions of silyl radicals under the conditions of vacuum after 20 hours annealing at room temperature. Understanding of the physical and chemical mechanism of degradation and of the reversible process of the PMPSi CL emission is interesting from both scientific and application point of view.
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  • Schauer, P.; Autrata, R.: Monte Carlo Simulation Code for Photon Collection in S(T)EM Scintillation Detectors. 7th Multinational Congress on Microscopy, Portoroz, Slovenia June 2005, Proceedings, p.199-200.
    Úvod:
    The inefficient collection of photons emitted from luminescent centres in a scintillation detector of electrons is a frequent cause of poor S(T)EM images, particularly in the BSE image mode. In such cases, edge guided signal (EGS) scintillation systems utilising a signal from the side of a scintillator, and having a complicated geometry, are often used. The best way of avoiding the light-guiding problems of these systems is Monte Carlo (MC) simulation optimisation for signal photon collection. Unfortunately, the previous code SCINTIL [1] developed in our laboratory was built using an algorithm for rotationally symmetric systems where a function of one variable coordinate was used. Therefore, the extended code SCIUNI, intended for practically any geometry, has been written and its features are presented in this paper.
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  • Horák, P.; Schauer, P.: Detekce slabé katodoluminiscence. Mikroskopie 2005, Nové Město na Moravě, únor 2005, Sborník, p.36.

  • Schauer, P.; Autrata, R.: Optimization of scintillation detector for SEM. EMC 2004 - 13th European Microscopy Congress, Antwerp, Belgium Aug 2004, Proceedings/Vol. I, p.69-70.
    Úvod:
    Detective quantum efficiency (DQE) is the best quantity for characterisation of the detector quality. Unfortunately, low DQE of a poor detector gives nearly no information about the limiting component. To enhance the bad scintillation detector, one has to divide its performance into particular events. Electron collection, photon generation, escape from scintillator, coupling to light-guide, losses in light-guide, photoelectron generation, as well as collection and multiplication in a photomultiplier tube (PMT) are the most significant events in the scintillation detector for SEM. To analyse these events and optimise the detector, a lot of important quantities of detector components (such as conversion efficiency, decay time, intrinsic noise and optical reflectivity, transmittance and matching) must be known. Thereafter, properties of each component can be calculated from individual quantities, and properties of the whole detector can be determined using a convolution.
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  • Autrata, R.; Schauer, P.: Nanoresolution BSE images created using a new type of YAG II scintillator. EMC 2004 - 13th European Microscopy Congress, Antwerp, Belgium Aug 2004, Proceedings/Vol. I, p.75-76.
    Úvod:
    Detection of backscattered electrons (BSE) in scanning electron microscopy (SEM) serves as an auxiliary method in the study of surfaces and composition of materials. Backscattered electrons have properties that are different from those of usually used secondary electrons. The achievement of the theoretical limit of resolution (0.6 – 0.8 nm for SE and 0.9 nm for BSE) depends not only on the properties of the electron source, properties of electron optics, specimen preparation technique, type of electrons, but also on the detection system efficiency.
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  • Schneider, L.; Jirák, J.; Autrata, R.; Schauer, P.: Dependence of contrast on pressure using segmental ionization detector in environmental SEM. EMC 2004 - 13th European Microscopy Congress, Antwerp, Belgium Aug 2004, Proceedings/Vol. I, p.341-342.
    Úvod:
    Ionization detector is often used for the detection of signal electrons in environmental scanning electron microscope (ESEM). This detector is based on the principle of signal electron amplification by the process of impact ionization in the specimen chamber with gaseous environment. The grounded specimen forms one electrode of the parallel electrode detection system [1]. The second electrode is placed above the specimen, and it is connected to the appropriate potential that causes impact ionization of secondary electrons. A hole in the upper electrode allows primary electrons to pass to the specimen and this electrode also detects amplified signal electrons.
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  • Schauer, P.; Autrata, R.: Experimental and simulative methods for scintillation detector optimization. 9th Inter. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalský Dvůr (Brno) July 2004, Proceedings, p.67-68.
    Úvod:
    In S(T)EM an image is formed using a focused electron beam, which is scanning across a very small part of the specimen surface. A scintillation detection system consisting of a scintillator, light-guide and photomultiplier (PMT) processes only one pixel of the image at any given moment. Not only efficiency, but also kinetic properties of such a system are of great importance. Scintillation detectors can show a noticeable difference in detective quantum efficiency (DQE) due to the bad electron-photon energy conversion and/or light losses in the optical part of the detector. Up to now, some studies were engaged in measurement of S(T)EM detectors performance ascertaining very low DQE for some detectors, but no suggestion has been made to optimize the detector set-up. To find the neck of a detection system, one must examine the whole detection path (Figure 1) step by step.
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  • Autrata, R.; Schauer, P.; Wandrol P.: New type of YAG-II scintillator for nanoresolution BSE imaging in SEM. 9th Inter. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalský Dvůr (Brno) July 2004, Proceedings, p.11-12.

  • Horák, P.; Schauer, P.: Cathodoluminescence of polysilanes. 9th Inter. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalský Dvůr (Brno) July 2004, Proceedings, p.31-32.
    Úvod:
    Polysilanes - a broad class of organic materials whose basic building block is a chain built up of silicon substituted by alkyl or aryl groups. Properties of these substituents significantly affect properties of polysilanes. This material is very interesting because of its chemical, electrical and optical properties [1]. In spite of great research interest in recent years cathodoluminescent (CL) properties of polysilanes were not yet studied. Poly[methyl(phenyl) silane] (PMPhSi) is a typical representative of polysilanes which was prepared by the Wurtz coupling polymerization. Thin layers of PMPhSi were prepared from toluene solution by a spin coating technique [2]. The material was applied on the quartz glass substrate and covered with the aluminium (Al) film. The Al film protected the specimen from charging and reflected photons emitted under the specimen surface towards the quartz glass substrate.
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  • Horák, P.; Schauer, P.: Studium katodoluminiscenčních vlastností polysilanů. Mikroskopie 2004, Nové Město na Moravě, březen 2004, Sborník, s.25.

  • Schauer, P.; Nešpůrek, S.; Schauer, F.; Autrata, R.: Optimization of Poly-(Methylphenylsilylene) Specimens for Cathodoluminescence Measurement. Microscopy Conference 2003 (31st conference of Deutsche Gesellschaft für Elektronenmikroskopie), Dresden, Germany, September 2003, Proceedings, p.156-157.
    Úvod:
    Two possibilities of photon collection from the luminescence centra can be applied at cathodoluminescence (CL) measurement of transparent specimens. The CL emission can be collected both from the side of excitation and substrate using a lens and a light guide, respectively. To choose the better alternative, one has to study optical properties and electron-interactive volumes of specimen materials. Based on this knowledge, optimized geometry, dimension and arrangement of the specimen can be designed. The object of our interest was the CL study of Poly-(Methylphenylsilylene), i.e. PMPhSi, which is an interesting material both from the application and the basic research point of view. The PMPhSi was prepared by the Wurtz coupling polymerization [1]. The low-molecular weight fractions were extracted with boiling diethyl ether. The layers for the CL measurements were prepared from a toluene solution by casting on quartz disk substrates.
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  • Schauer, P.; Nešpůrek, S.; Schauer, F.; Autrata, R.: Electron Beam Degradation Study of Silicon Polymers. 6th Multinational Congress on Microscopy, Pula, Croatia June 2003, Proceedings, p.205-206.
    Úvod:
    Excitation of organic molecules, polymers and molecular assemblies by electrons represents interesting phenomena from both the application (detectors on one side and electron resists on the other side) and the basic research point of view. The aim of this paper is to present the first steps of our cathodoluminescence (CL) study of the metastable states in poly-(methylphenylsilylene), i.e. PMPhSi.
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  • Autrata, R.; Neděla, V.; Horký, D.; Schauer, P.: Comparison of Imaging with SE Ionisation and BSE Scintillation Detector in ESEM. 6th Multinational Congress on Microscopy, Pula, Croatia June 2003, Proceedings, p.487-488.
    Úvod:
    Environmental scanning electron microscopy (ESEM) or low-vacuum scanning electron microscopy (LV SEM) enables the visualisation of samples in a gaseous environment at the pressure of the specimen chamber from 1 Pa to over 1000 Pa. Detection of signal electrons, namely secondary electrons (SES) cannot be realised in a gaseous environment of the specimen chamber in the same way as for the high vacuum SEM, because high voltage of the Everhart-Thornley detector is not compatible with the conductance of the low vacuum environment [1]. For this reason, gaseous ions which are ionised by SES from the specimen are used for the detection in ESEM. For the detection of the backscattered electrons (BSES), conventional scintillation detector is the best to use.
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  • Schauer, P.; Autrata, R.: Experimental Setup for Cathodoluminescence Spectra Measurement. 15th International Congress on Electron Microscopy (ICEM 15), Durban, South Africa Sep 2002, Proceedings, Vol. 3 - Interdisciplinary, p.337-338.
    Úvod:
    Scintillators and cathodoluminescent (CL) screens are typical imaging elements in electron microscopes. For their properties evaluation, for the study of new materials, or for the improvement of the original elements, one has to study CL emission spectra. In our laboratory the measurement equipment for the investigation of CL properties of solid specimens has been built. The excitation unit with the electrostatic deflection system is formed by the adapted electron microscope, the light collection part is made up using the bulk UV transmitting light guide, and the detection unit is formed by the fast and efficient photomultiplier tube (PMT). The CL properties of specimens shaped as slim disks can be measured in continuous or pulse modes. So the efficiency, emission spectrum and the rise and decay times can be investigated for 10 keV electron beams. Although the pulse mode was intended for the determination of kinetic properties, it can also be used with advantage for the measurement of emission spectra.
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  • Autrata, R.; Schauer, P.: New Fast and Efficient YAP Scintillator for the Detection in SEM. 15th International Congress on Electron Microscopy (ICEM 15), Durban, South Africa Sep 2002, Proceedings, Vol. 3 - Interdisciplinary, p.347-348.
    Úvod:
    Several types of detection system have been designed for detection of signal electrons in SEM. They differ in their components (scintillator – PMT systems, semiconductor systems, channel plate multiplier), in the detection material, geometrical configuration etc. Further, their use depends on the requirement for the detection of certain types of signal electrons (SE, BSE, TE). The energy of signal electrons and their angular distribution, propagation of electrons in the electrostatic or magnetic field, demands on resolution, time characteristics, noise properties and vacuum conditions are some further aspects which decide on the suitability of use of a specific detection in SEM. Comparably among these systems, the scintillation – PMT system, designed in 1960 by Everhart-Thorneley (1), still possesses the best signal to noise ratio and bandwidth characteristics.
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  • Schauer, P.; Autrata, R.: Cathodoluminescence Spectra Measurement. 7th Inter. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalský Dvůr (Brno) Jul 2002, Proceedings, p.67-70.
    Úvod:
    In our laboratory the equipment for the investigation of cathodoluminescent (CL) properties of solid specimens has been built. The equipment is based on the completely rebuilt Tesla BS242 electron microscope, supplied by the light collection UV transmitting system, and by the fast and efficient photomultiplier tube (PMT) as the detection unit. The CL properties of specimens (slim disks) can be measured in continuous or pulse modes. So, in addition to the efficiency and decay times the emission spectra can be measured for 10 keV electron beams.
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  • Autrata, R.; Schauer, P.: Improvement of Single Crystal Scintillator Properties in SEM Detectors. 6th Inter. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalský Dvůr (Brno) Jul 2002, Proceedings, p.47-48.
    Úvod:
    Properties of the scintillation – PMT detection system in SEM depend on the properties of the scintillator and the light guide, for all. Efficient energy transfer electron-photon, very short decay time of luminescence and an efficient transfer of photons in the light guide to the photomultiplier are the decisive properties for the efficient detection system.
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  • Schauer, P.; Vlček, I.; Autrata, R.: Improved Recording System for the Study of Single Crystal Imaging Screens. 5th Multinational Congress on Electron Microscopy, Lecce, Italy Sep 2001, Proceedings, p.533-534.
    Úvod:
    The progressive image recording system in transmission electron microscope (TEM) is the setup utilising the YAG:Ce single crystal imaging screen, a light optical device, and some recording unit enabling processing the resulting image using a personal computer (PC). For such an arrangement, the key role relates to the screen, that has to provide an image with minimum imperfections to obtain an acceptable result after the final magnification. Therefore, imaging capability, i.e. spatial resolution, striations, and other defects of single crystal screens must be studied very carefully.
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  • Autrata, R.; Schauer, P.; Jirak, J.: Detection of backscattered electrons for biological speciments study. 5th Multinational Congress on Electron Microscopy, Lecce, Italy Sep 2001, Proceedings, p.519-520.
    Úvod:
    Energy of backscattered electrons (BSEs) unlike energy of secondary electrons (SEs) is just little lower than primary electron beam energy. BSEs leave a specimen from a lower depth than SEs and they spread themselves forward to the space. They bring information especially about material character of a specimen expressed by atomic contrast. As a result of these properties BSE image is less exposed to charging artefacts of non-conductive specimens, smaller influence of contamination and lower overbrightness of edges. Under convenient operation conditions in SEM and at use of suitable preparation techniques, BSE image resolution can be comparable with SE image. BSE detection is an indispensable method for obtaining supplementary image information of material and biological research by SEM..
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  • Schauer, P.; Autrata, R.: Performance of Detector Elements for Electron Microscopes. 12th European Congress on Electron Microscopy, Brno, Czech Republic Jul 2000, Proceedings/Vol. 3, p.I 455.
    Úvod:
    Signal processing in scanning and transmission electron microscopes is analysed in this paper. Distinguished are criteria of principal and commercial significance, and problematic parameters of different systems are highlighted. The most important properties of scintillation detection systems and imaging screens are discussed more in detail. For the scintillation detector, the analysis of conversion of the signal to photons, their transport from emission centres to PMT photocathode, and their conversion to photoelectrons is carried out. For the imaging screen, attention is focussed on the spectral matching and spatial resolution.
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  • Schauer, P.; Autrata, R.: Study of TEM Fluorescent Screen. 4th Multinational Congress on Electron Microscopy, Veszprem, Hungary Sep 1999, Proceedings, p.167-168.
    Úvod:
    In a transmission electron microscope (TEM), the electron image must be visualised by the observation system of the instrument. For this purpose, an imaging fluorescent screen has to be used which is capable of converting the energy of signal electrons into photons and offers the resulting image to the human eye or to a recording device. The screen provides the possibility for the location of the desired field of view, for the focussing of the lenses, and particularly for the study of the specimen. If necessary, the image from the screen is observed through a light optical magnifier.
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  • Autrata, R.; Schauer, P.: Single Crystal Scintillation Detectors for LVSEM. 14th International Congress on Electron Microscopy (ICEM 14), Cancun, Mexico Aug-Sep 1998, Proceedings/Vol. 1, p.437-438.
    Úvod:
    The scintillator-photomultiplier system to detect signal electrons has, from the viewpoint of detection efficiency, not been surpassed as yet. In combination with single crystal scintillators based on yttrium aluminium garnet (YAG) or yttrium aluminium perovskite (YAP), it allows achieving of a highest signal-to-noise ratio that ensures attainment of a high image resolution.
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  • Schauer, P.; Autrata, R.: Performance of YAG:Ce Single Crystal Screens for TEM. 14th International Congress on Electron Microscopy (ICEM 14), Cancun, Mexico Aug-Sep 1998, Proceedings/Vol. 1, p.633-634.
    Úvod:
    Originally, the YAG:Ce single crystals were developed for use in scintillation detectors of scanning electron microscopes (SEM). They have been studied extensively, and nearly all properties relevant to their application as scintillators are known (the most important are shown in Table 1). Nevertheless, the YAG:Ce is also a very appropriate crystal for imaging screens because of its well defined optical properties, in particular its optical homogeneity. Moreover, the crystals can be shaped precisely, even into very small elements for forming a small image intended for further processing. However, screen materials can not be used without an analysis of the cathodoluminescent (CL) image. The best characteristic to express imaging properties (including spatial resolution) is the modulation transfer function (MTF). Finding out the MTF of the YAG:Ce single crystal screen is the topic of this work.
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  • Schauer, P.; Autrata, R.: Cathodoluminescent Properties of Single Crystals for S(T)EM Detectors. 6th Inter. Seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Skalský Dvůr (Brno) Jun-Jul 1998, Proceedings, p.60-63.
    Úvod:
    The cathodoluminiscent (CL) emission spectrum, CL efficiency (emission intensity), and decay time are three basic scintillator parameters of a scintillation detector for a scanning electron microscope and/or a scanning transmission electron microscope - S(T)EM. They are important not only for the estimation of suitability of the single crystals application in S(T)EM but also for the physical analysis of CL. Besides the scintillator efficiency, the scintillator decay time is the decisive characteristic for a high detective quantum efficiency (DQE), and the emission spectrum is an important characteristic for the spectral matching to the photomultiplier tube (PMT).
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  • Yamamoto, K.; Tanji, T.; Hibino, M.; Schauer, P.; Autrata, R.: Improvement of Light Collection Efficiency of Lens Coupled YAG Screen TV System for HVEM. International Symposium on Atomic level Characterizations for New Materials and Devices '97, Maui, Hawaii, USA Nov 1997, Proceedings, p.98-101.

  • Autrata, R.; Schauer, P.; Madea, D.: Single crystal scintillators for BSE detectors in SEM. EUREM-11, the Eleventh European Congress on Electron Microscopy (Edited and Published by the CESM, Brussels 1998), Dublin, Ireland August 1996, Proceedings/Vol. 1, p.467.

  • Schauer, P.; Autrata, R.: Computer optimized design of BSE scintillation detector for SEM. EUREM-11, the Eleventh European Congress on Electron Microscopy (Edited and Published by the CESM, Brussels 1998), Dublin, Ireland August 1996, Proceedings/Vol. 1, p.369.
    Úvod:
    The design of an efficient backscattered electron (BSE) scintillation detector for a scanning electron microscope (SEM) depends to a great extent on the size and the arrangement of pole pieces and the specimen holder of the SEM. Therefore, for different microscopes, different scintillator - light-guide detection systems must be constructed. However, the efficiency of these edge guided signal (EGS) scintillation detectors is very strongly shape dependent (1). Even apparently insignificant changes in the light-guide geometry can degrade the efficiency of the EGS detection system to one tenth of its optimal value. Furthermore, owing to the low symmetry of EGS detection systems, the efficiency is very hard to estimate or calculate analytically. The best way of avoiding inefficient EGS detection systems is Monte Carlo (MC) simulation optimisation method for the photon transport through the scintillator and light-guide.
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  • Handlir, R.; Schauer, F.; Nespurek, S.; Kuritka, I.; Weiter, M.; Schauer, P.: Metastable States in Poly(methylphenylsilylene) Induced by UV Radiation and Electron Beam. International Conference on Amorphous and Microcrystalline Semiconductors (ICAMS 17), Budapest, Hungary Aug 1997, Proceedings, p.290.

  • Autrata, R.; Hutař, O.; Schauer, P.: Low Voltage Single Crystal Backscatter Electron Detectors. Multinational Congress on Electron Microscopy, Portorož, Slovenia Oct 1997, Proceedings, p.281-182.
    Úvod:
    High efficiency BSE detection can be carried out using solid-state detectors, microchannel-plate detectors and scintillation detectors of different geometrical configurations. At higher beam voltages, all these detectors show sufficient efficiency. Nevertheless, if the highest possible resolution or ultrahigh resolution, depending on the signal to noise ratio are to be achieved, scintillation detectors are preferred despite their complex construction.

  • Schauer, P.; Autrata, R.: Scintillator-Photocathode Matching in Scintillation Detector for S(T)EM. Multinational Congress on Electron Microscopy, Portorož, Slovenia Oct 1997, Proceedings, p.293-294.
    Úvod:
    Besides the decay time, the efficiency is the most important parameter of a scintillation detector for a scanning electron microscope and/or a scanning transmission electron microscope - S(T)EM. Much attention has been paid to the examination of the energy conversion efficiency in scintillators (Autrata and Schauer 1996). The study of the efficiency of the light transport from scintillator luminescence centres through a light guide to a photomultiplier tube (PMT) has been accomplished too (Schauer and Autrata 1992). But nearly no effort has been devoted to the analysis of the scintillator-photocathode spectral matching. Such an analysis is the topic of this paper.
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  • Autrata, R.; Schauer, P.; Madea, D.: Single crystal scintillators for BSE detectors in SEM. 11th European Congress on Microscopy (EUREM 96), Dublin, Ireland August 1996, CD-ROM Proceedings, p..

  • Schauer, P.; Autrata, R.: Computer optimized design of BSE scintillation detector for SEM. 11th European Congress on Microscopy (EUREM 96), Dublin, Ireland August 1996, CD-ROM Proceedings, p..
    Úvod:
    The design of an efficient backscattered electron (BSE) scintillation detector for a scanning electron microscope (SEM) depends to a great extent on the size and the arrangement of pole pieces and the specimen holder of the SEM. Therefore, for different microscopes, different scintillator - light-guide detection systems must be constructed. However, the efficiency of these edge guided signal (EGS) scintillation detectors is very strongly shape dependent (1). Even apparently insignificant changes in the light-guide geometry can degrade the efficiency of the EGS detection system to one tenth of its optimal value. Furthermore, owing to the low symmetry of EGS detection systems, the efficiency is very hard to estimate or calculate analytically. The best way of avoiding inefficient EGS detection systems is Monte Carlo (MC) simulation optimisation method for the photon transport through the scintillator and light-guide.
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  • Hibino, M.; Ban, K.; Tanaka, S.; Schauer, P.; Autrata, R.: High Resolution and High Collection Efficiency YAG Screen for Lens Coupling TV and CCD Camera. 6th Asia-Pacific Conference on Electron Microscopy (APEM), Hong Kong July 1996, Proceedings, p.45-46.

  • Schauer, P.; Autrata, R.: Computer Designed Scintillation Detectors for SEM. 5th Seminar of Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Brno, Czech Republic June 1996, Proceedings, p.73-74.
    Úvod:
    Two different modes of scintillation detection of electrons are used in SEMs. One (basic) makes use of the Everhart-Thornley (ET) detector, i.e. a base guided signal (BGS) rotationally symmetric system, intended for the detection of secondary electrons. The other makes use of an edge guided signal (EGS) scintillation system, and it is intended for the detection of backscattered electrons. An optimum design of detectors for both detection modes depends on the proper choice of material and geometry of the scintillator and light guide, as well as on the treatment of all surfaces including boundaries. Furthermore, the detector design must comply with the space available in the microscope. Estimation and experimental verification of the properties of such a detection system are very time consuming and expensive and offer uncertain results.
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  • Autrata, R.; Schauer, P; Jirak, J.; Spinka, J.: Signal Detection in SEM. 5th Seminar of Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Brno, Czech Republic June 1996, Proceedings, p.43-46.

  • Schauer, P.; Autrata, R.: Some Methods for Investigation of Detector Components for Electron Microscopy. 5th Seminar of Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, Brno, Czech Republic June 1996, Proceedings, p.47-50.
    Úvod:
    Scintillators, light guides, photomultiplier tubes (PMT) and imaging screens are opto-electrical components used for detection systems in electron microscopy (EM). Many methods for the study of their properties were developed in our laboratory. Some of them are presented in this paper.
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  • Schauer, P.; Autrata, R.: Spatial Resolution of YAG:Ce Single Crystal CL Screens. Multinational Congress on Electron Microscopy, St. Lesna, Slovak Rep Oct 1995, Proceedings, p.115-116.

  • Autrata, R.; Schauer, P.: Behaviour of Planar and Annular YAG Single Crystal Detectors for LVSEM Operation. 13th International Congress on Electron Microscopy (ICEM 13), Paris, France July 1994, Proceedings/Vol. I, p.71-72.

  • Schauer, P.; Autrata, R.: Time Response of Single Crystal Scintillation Detectors for SEM/STEM. 13th International Congress on Electron Microscopy (ICEM 13), Paris, France July 1994, Proceedings/Vol. I, p.227-228.

  • Autrata, R.; Schauer, P.: Cathodoluminescent Properties of Single Crystals for Electron Microscopy. Thirteenth Pfefferkorn Conference on Luminescence, Niagara Falls, Canada May 1994, Abstract Summary, p.1.

  • Schauer P., Autrata R.: Efficiency of SEM/STEM Scintillation Electron Detectors with Edge Guided Signal. Multinational Congress on Electron Microscopy, Parma, Italy Sept 1993, Proceedings, p.357-358.
    Úvod:
    Some Image modes of SEM or STEM require that the electron impact active surface of the detector of signal electrons should be fitted into a very small space, mostly symmetrically around the primary electron beam. This demand is easily fulfilled for semiconductor or channel plate detectors. However, they possess a low detective quantum efficiency and/or a high decay time, so that they are often unusable. Therefore, scintillation detectors in non-classical arrangements are applied. Here the signal must be guided through an edge of a plate scintillator1. The input end of the light guide must be narrow, to match to the edge of the scintillator, and the output end may be enlarged, according to the input window of the photomultiplier. The design of such a scintillator - light guide system with a high efficiency of the light transport is the key problem of the detector design.scintillator-photocathode spectral matching. Such an analysis is the topic of this paper.
    Plná PDF verze

  • Autrata R., Schauer P.: Collection of Low-Energy Signal Electrons in the Rotationally Symmetric Electrostatic Field of a Detector. Three Countries' EM Conference, BEDO 1993, Zurich, Switzerland Sept 1993, Proceedings, p..

  • Schauer P., Autrata R.: Coatings of Single Crystal Scintillators for Electron Detectors in SEM. 10th European Congress on Electron Microscopy, Granada, Spain Sept 1992, Proceedings/Vol. I, p.107.
    Úvod:
    The scintillator in the Everhart-Thornley detector of electrons collects signal electrons and transforms them into photons that are more suitable for signal processing. The surface of the scintillator hit by the signal electrons (input surface) must be conductive enough to prevent charging and must show high internal optical reflectivity in the spectral range of scintillator emission to ensure the collection of signal photons toward the photocathode of the photomultiplier (PMT). All currently used scintillators are non-conductive and it is therefore necessary to provide their input surfaces with a thin conductive coating. The coating must be thin enough not to absorb the energy of signal electrons and at the same time thick enough to be conductive and to show high optical reflectivity. It is difficult to meet these conflicting requirements. Moreover, the choice of the suitable material and thickness of the coating depends on the material and geometry of the scintillator and light guide. The aim of this paper is to analyse the influence of the thin film coating applied to the polished input surface of the YAG:Ce single crystal scintillator on the signal losses in SEM. Optically non-transparent (metal) Al and Ag films (including the Ag-Al double layer) and the transparent indium tin oxide (ITO) film have been investigated. For comparison, layers with ideal reflectivity and no reflectivity, respectively, were included.
    Plná PDF verze

  • Hibino M., Irie K., Autrata R., Schauer P.: YAG single crystals for scintillators of STEM. XIIth International Congress for Electron Microscopy, San Francisco 1990, Proceedings, p.166.

  • Schauer P., Autrata R.: Vyhodnoceni optickych vlastnosti scintilacniho detektoru v SEM. 20. ceskoslovenska konference o elektronove mikroskopii, Praha 1989, s.86.

  • Schauer P., Autrata R.: Influence of single crystal yttrium aluminates surfaces on their cathodoluminescent properties. 7th. Czechoslovak conference on electronics and vacuum physics, Bratislava 1985, Proceedings/Vol. 1, p.265.

  • Autrata R., Schauer P., Kvapil Ji., Kvapil Jos.: Single-crystal electron detectors. 8th. European Congress on Electron Microscopy, Budapest 1984, Proceedings/Vol. I, p.617.

  • Autrata R., Schauer P., Kvapil Ji., Kvapil Jos.: Monokrystalicke scintilatory pro rastrovaci elektronovy mikroskop. Dny nove techniky elektrotechnickeo vyzkumu, Praha 1983, Katalog exponatu, s.96.

  • Autrata R., Schauer P., Kvapil Jos., Kvapil Ji.: Scintillation detector for backscattered electron imaging in SEM. Surface analysis 83, Bratislava 1983, Proceedings, p.57.

  • Autrata R., Chaloupka M., Schauer P., Kvapil Jos., Kvapil Ji.: The use of single crystal scintillators for back-scattered imaging. 15 Kolloquium uber Oberflachen-abbildung und Analyse in Microbereichen, Bremen 1982, Proceedings/Vol. A, p.15.

  • Autrata R., Schauer P., Kvapil Ji., Kvapil Jo.: Influence of Ce3+ and other dopants concentration in single crystals of Y3Al5O12 and YAlO3 on their cathodoluminescent properties. European meeting on crystal growth, Prague 1982, Proceedings, p.435.

  • Autrata R., Schauer P., Kvapil Jos., Kvapil Ji.: A single crystal of Y3Al5O12:Ce3+ as a scintillator in SEM and transparent screen in electron optical devices. 10th. International Congress on Electron Microscopy, Hamburg 1982, Proceedings/Vol. I, p.451.

  • Kvapil Ji., Kvapil Jos., Autrata R., Schauer P.: Spectral properties of oxide crystals free of iron ions. Mezdunarodnaja konferencija; Defekty v dielektriceskich kristallach, Riga 1981, Vol. 1, p.48.

  • Kvapil Ji., Kvapil Jos., Manek B., Perner B., Autrata R., Schauer P.: Czochralski growth of YAG:Ce in reducing protective atmosphere. Six International Conference on Crystal Growth, Moskva 1980, Proceedings/Vol. III, p.113.

  • Autrata R., Schauer P., Kvapil Jos., Kvapil Ji.: Scintilacni detektor v rastrovacim elektronovem mikroskopu. Sbornik sympozia o stavu a perspektivach scintilacnich detektoru a jejich vyuziti, Harrachov 1980, s.80.

  • Autrata R., Schauer P.: Bystrij i dolgovecnyj monokristaliceskij scintiljator dlja rastrovovo elektronovo mikroskopa s avtoemissionnoj puskoj. XI. vsjesajuznaja konferencija po elektronnoj mikroskopii, Tallin 1979, 3, s.74.

  • Autrata R., Schauer P.: Scintillators for use in electron microscopes. XVth Czechoslovak conference on electron microscopy, Prague 1977, Proceedings/Vol. B, p.428.

 

 

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