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Methods of Preparation and Characterization of Experimental Field-Emission Cathodes
Knápek, Alexandr ; Luňáček, Jiří (oponent) ; Lazar, Josef (oponent) ; Grmela, Lubomír (vedoucí práce)
This PhD thesis describes, and covers the preparation of field-emission cathodes that represent a high-quality, inexpensive source of electrons for devices that work with a focused electron beam. In this work, an improved method of electrochemical fabrication is used for the preparation of a composite field-emission cathode. The composite structure improves current stability in comparison to tungsten-based pure field-emission cathodes. Improvements to the technology used were implemented on the basis of findings obtained using spectrum noise diagnostics, which are based on measuring and evaluating the emission current in the time and in frequency domains. Additionally, noise spectroscopy provides important information about charge transport, electron mobility, and lifespan, which is essential for future research. Results obtained using the experimental method have been further supplemented with theoretical data provided by a computer simulation in order to establish characterization procedures for improved field-emission cathodes.
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Návrh měřicího pracoviště pro šumovou spektroskopii
Segiňák, Ján ; Fiala, Pavel (oponent) ; Szabó, Zoltán (vedoucí práce)
Práca obsahuje literárnu rešerš z oblasti šumu, spektroskopie a spektroskopických meracích metód v rámci širokého pásma frekvencií. Bola navrhnutá experimentálna meracia metóda pre meranie vzoriek materiálov šumovou spektroskopiou v meranom pásme 0,1 – 6 GHz, s použitím širokopásmového generátora šumu a zostavené meracie pracovisko pre šumovú spektroskopiu s popisom jednotlivých častí. Programová podpora pre automatizované meranie vzoriek bola vytvorená v prostredí Agilent VEE. Posledná časť práce sa venuje meraniu vybraných vzoriek a vyhodnocovaniu výsledkov merania.
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Návrh měřicího pracoviště pro šumovou spektroskopii
Segiňák, Ján ; Fiala, Pavel (oponent) ; Szabó, Zoltán (vedoucí práce)
Práca obsahuje literárnu rešerš z oblasti šumu, spektroskopie a spektroskopických meracích metód v rámci širokého pásma frekvencií. Bola navrhnutá experimentálna meracia metóda pre meranie vzoriek materiálov šumovou spektroskopiou v meranom pásme 0,1 – 6 GHz, s použitím širokopásmového generátora šumu a zostavené meracie pracovisko pre šumovú spektroskopiu s popisom jednotlivých častí. Programová podpora pre automatizované meranie vzoriek bola vytvorená v prostredí Agilent VEE. Posledná časť práce sa venuje meraniu vybraných vzoriek a vyhodnocovaniu výsledkov merania.
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Methods of Preparation and Characterization of Experimental Field-Emission Cathodes
Knápek, Alexandr ; Luňáček, Jiří (oponent) ; Lazar, Josef (oponent) ; Grmela, Lubomír (vedoucí práce)
This PhD thesis describes, and covers the preparation of field-emission cathodes that represent a high-quality, inexpensive source of electrons for devices that work with a focused electron beam. In this work, an improved method of electrochemical fabrication is used for the preparation of a composite field-emission cathode. The composite structure improves current stability in comparison to tungsten-based pure field-emission cathodes. Improvements to the technology used were implemented on the basis of findings obtained using spectrum noise diagnostics, which are based on measuring and evaluating the emission current in the time and in frequency domains. Additionally, noise spectroscopy provides important information about charge transport, electron mobility, and lifespan, which is essential for future research. Results obtained using the experimental method have been further supplemented with theoretical data provided by a computer simulation in order to establish characterization procedures for improved field-emission cathodes.
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Radiation Detectors Noise Spectroscopy
Andreev, Alexey ; Grmela, Lubomír (vedoucí práce)
Cadmium Telluride is a material of great importance in the fields of both fundamental research and technical applications, because of its structural, optical, electronic and photoelectronic properties. Today the main application of Cadmium Telluride is in high resolution detection of -rays and X–rays. The main advantage of radiation detectors manufactured on CdTe base is that they need no cooling and can operate at the room temperature and there is a more effective interaction of photons in CdTe than in either Si or Ge. The transport and noise characteristics of CdTe samples were studied. The measurements show that the bulk resistance of CdTe single crystals decreases very slowly when the external electric field is applied. n-type samples and p-type samples show different response on the temperature changes. These effects were analyzed. The noise measurements show that dominant noise at low frequencies is type of 1/f noise. At higher frequencies generation-recombination and thermal noise were apparent. All the studied samples have very high value of low frequency noise, much higher than it should have been according to Hooge’s formula. The sources of excess noise were investigated.
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