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Innovation possibilities of scintillation electron detector for SEM
Schauer, Petr ; Bok, Jan
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. 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 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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Analýza poly[methyl(phenyl)silylene] degradovaného elektronovým svazkem
Horák, Petr ; Schauer, Petr
Polysilanes (PSi) 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 radiation or by electron beam. 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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Účinek elektronového svazku na poly[fenyl(methyl)silylen]
Horák, Petr ; Schauer, Petr
The study of Poly[Methyl(Phenyl)Silylene] properties using cathodoluminescent method is complicated by the material degradation. The speed of degradation depends on the irradiation time as well as on the current density of the excitation beam. CL investigation of PMPSi proved creating of metastable states in the material. The degradation is a reversible process in this case.
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Kinetika doznívání scintilačních krystalů pro detektory elektronů v SEM
Schauer, Petr
A study of the decay kinetics of YAG:Ce single crystal scintillators for SEM is presented in this paper. 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. Utilizing of the cathodoluminescence decay results, a schematic kinetic model of radiative and nonradiative transitions in the YAG:Ce single crystals is presented.
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Metastability of poly[methyl(phenyl)silylene]
Horák, Petr
Metastability of the poly[methyl(phenyl)silylene] (PMPhSi) specimen was studied using the cathodoluminescent (CL) method. The process of the CL emission recovery, depending on the irradiation time as well as on the current density of the excitation beam, was observed. The process of the CL recovery is the strongest at the smallest current densities. Knowledge of the time dependence of the PMPhSi degradation will be used for the CL spectra measurement.
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Katodoluminiscence polysilanů
Horák, Petr ; Schauer, Petr
Polysilanes - a broad class of organic materials whose basic building block is 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. 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. 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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Příprava a charakterizace struktur ZnO malých rozměrů
Grym, Jan ; Fernández, P. ; Piqueras, J.
ZnO low dimensional structures were prepared in order to study their unique electronic and optical properties. ZnO nanocrystals were obtained by ball milling of commercially available powders. This process was found to produce particles with sizes of tens to hundreds nanometers being composed of nanocrystals down to a few nanometers. ZnO micro and nanorods mainly of hexagonal shape as well as nanotubes and nanocombs were grown by vapor-solid method in a muffle furnace under the flow of high purity argon.
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