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Influence of working conditions on the signal level detected by BSE detector
Bednář, Eduard ; Zimáková, Jana (referee) ; Čudek, Pavel (advisor)
This thesis deals with the evaluation of the quality of the signal level of backscattered electrons detected by the scintillation backscattered electron detector depending on the working conditions in low vacuum scanning electron microscope. The theoretical part describes the issue of environmental scanning electron microscopy, the principle of generation the signal and detection of backscattered electrons. The experimental part of the thesis is to measure the properties of the scintillation detector of backscattered electrons. A series of experiments is evaluated the influence of working conditions on the stability and function of the detector of backscattered electron.
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Scintillation Secondary Electrons Detector for ESEM
Čudek, Pavel ; Kadlec, Jaromír (referee) ; Rek, Antonín (referee) ; Jirák, Josef (advisor)
The thesis deals with the scintillation secondary electron detector for environmental scanning electron microscope, its design and construction. The starting point was numerical simulation of electrostatic fields and electron trajectories in the electrode system of the detector and simulation of pressure distribution and flow of gases in different parts of the detector. On the basis of modeling and simulation, construction changes of the detector were gradually implemented. Detection efficiency of each version of the detector was determined by the method described in the work. This method enables to evaluate signal level from the captured images of the specimen, quality of images was stated from signal to noise ratio. The thesis describes the whole process of the detector improvement from initial state, when the detector operated with lower efficiency in the pressure range from 300 to 900 Pa, to final version that enables usage of the detector in the range from vacuum up to 1000 Pa of water vapors in the specimen chamber of the microscope.
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Detection of Signal Electrons in High Pressure Conditions in Environmental Scanning Electron Microscopy
Neděla, Vilém ; Jirák, Josef (advisor)
The thesis deals with the study of properties of a new system for detection of true secondary and backscattered electrons in high pressure conditions of the specimen chamber of a newly built environmental scanning electron microscope AQUASEM II. Detection system contains three detectors. For the first time is introduced and analyzed the working principle of ionisation detector with electrostatic separator, which is in many experiments compared with ionisation detector of secondary electrons. Experimentally demonstrated are unique properties of this detection system, especially the ability of energy separation of detected signal electrons. For the various working conditions are also analyzed signal levels detected by the BSE YAG detector, which is designed as a part of the new detection system and which worked together with both ionisation detectors.
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Scintillation SE Detector for Variable Pressure SEM
Tihlaříková, Eva ; Neděla, Vilém (referee) ; Jirák, Josef (advisor)
This project deals with the theme of environmental scanning electron microscopy (EREM). This method allows the examination of insulators and wet specimens without pretreatment and modification like drying and metallization. The principle of this method consists in using higher pressure in a specimen chamber. The pressure is within the range of 100 – 200 Pa. However, the pressure in the specimen chamber restricts the signal detection interference. The objective of the work is to explore the possibility of interference in secondary electron route detection by way of electrostatic field. The electrostatic field was realized with the system consisting of four electrodes located in front of the scintillation detector. It should have interfered the secondary electron´s trajectory to the detector chamber. The optimization of voltage on the electrodes was made by simulation program called SIMION. The simulation results were experimentally verified with laboratory EREM.
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Zobrazování nevodivých vzorků pomocí nízkoenergiových zpětně odražených elektronů v SEM
Wandrol, Petr
Article deals with the problems of imaging of non-conductive samples in the SEM that are caused mainly by charging. Use of the low primary beam energy and the observation by means of backscattered electrons are proposed as methods of suppression of charging artifacts in the image. Newly developed detector of backscattered electrons for the low energy SEM is described and images of uncoated non-conductive samples without charging artifacts taken by this detector are presented.
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Angular distribution of backscattered electrons signal in Environmental Scanning Electron Microscopy
Wandrol, Petr
The aim of this work was to verify an influence of the collection solid angle on a magnitude of detected signal. The presented results of measurement were gained by an observation of the specimen of carbon covered with a thin layer of gold. The primary beam accelerating voltage was 20kV. The collection solid angle was changed by application of aluminium masks with aperture diameters 2,3,4,8,16 mm mounted on scintillator. As a working environment in the specimen chamber air and saturated water vapour were used.
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