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SMV-2023-05: DI2023
Matějka, Milan ; Krátký, Stanislav ; Meluzín, Petr ; Košelová, Zuzana ; Chlumská, Jana ; Horáček, Miroslav ; Kolařík, Vladimír ; Knápek, Alexandr
The research focuses on the investigation and development of precise calibration samples with relief structures. These samples are designed for calibrating parameters in scanning electron microscopes (SEM). Test patterns allow verification of the imaging quality through microscopic techniques such as overall magnification, field of view size, resolution, deformation in lateral axes, and other geometric distortions. Precision lithographic techniques and other methods derived from silicon processing technologies in the semiconductor industry are employed for sample preparation. The development has been directed towards optimizing the recording of etching masks before transferring the image onto a monocrystalline silicon substrate.
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Influence of High Concentration of Silica Nanoparticles on the Dielectric Spectra
Soud, Ammar Al ; Daradkeh, Samer ; Knápek, Alexandr ; Liedermann, Karel ; Holcman, Vladimír ; Sobola, Dinara
In the presented work, we report the dielectricbehavior of epoxy–silicon oxide composites in the temperaturerange 240– 300 K, over the frequency range 10-2 Hz – 107 Hz. Themeasuring apparatus was based on the Novocontrol AlphaAnalyser and the measured data were analyzed and interpretedusing the Havriliak – Negami equation. The master curves of thereal part of permittivity and the dielectric loss number wereobtained by time–temperature superposition principle, and theresults showed that the nano-composite had a much higher lossfactor. Through the analysis of the origin of the dielectric responsein epoxy/silica composite, the reason for the different dielectricrelaxation behaviors of the nano-composite, and the pure epoxywas discussed.
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Field emission characteristics and analysis of chargé flow through graphite based cathodes
Allaham, Mohammad M. ; Burda, Daniel ; Sobola, Dinara ; Knápek, Alexandr
This paper studies the performance of differenttypes of graphite cathodes when operated as field emissionelectron sources. The tested cathodes were prepared in theform of bulk polymer graphite, bulk pure graphite, and polymergraphite coated with thin layer of insulating material(epoxy resin). The obtained results include X-Ray photoelectronspectroscopy analysis, scanning electron micrographs, the fieldemission microscope patterns and current-voltage characteristics,and the orthodoxy test analysis results. The importance of thisstudy is summarized in following the pursuit of finding cheapand green electron sources. Moreover, to present a new exoticfield emission behavior in the form of emission pulses.
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SMV-2023-03: Holder for field-emission cathodes
Knápek, Alexandr ; Horáček, Miroslav ; Klein, Pavel
The contract research (CR) deals with the development of a modular holder for the development and testing of field-emission cathodes under ultra-high vacuum conditions. The research combines knowledge from vacuum engineering, power electronics and surface physics to achieve a reliable device that allows working with field-emission cathodes under vacuum conditions in diode and triode configurations. The main deliverables for the customer are drawings that allow the apparatus to be replicated and one piece of working prototype that has been constructed within the CR to verify the function.
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Effect Of Al2O3 Barrier On The Field Emission Properties Of Tungsten Single-Tip Field Emitters
Burda, Daniel ; Knápek, Alexandr
This research aims to obtain a more in-depth understanding of the field emission properties of tungsten single-tip field emitters (STFEs) coated with a several tens of nanometer thin barrier of Al2O3. The introduction of an additional barrier into the metal-vacuum interface system of the emitter can be beneficial to improve its performance. The tungsten emitters were prepared using a two-step electrochemical drop-off etching technique. Thin oxide barrier coatings were prepared by using low-temperature atomic layer deposition (ALD), a chemical vapor deposition technique. Field emission was studied in an internally developed field emission microscope (FEM) working in UHV vacuum (< 1·10−7 Pa), and the experimental field emission data were analyzed by the so-called Murphy-Good plotsThe value of the local work function of the grown oxide layer were investigated using Ultra-violet photoelectron spectroscopy (UPS).
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Effect Of Al2O3 Barrier On The Field Emission Properties Of Tungsten Single-Tip Field Emitters
Burda, Daniel ; Knápek, Alexandr
This research aims to obtain a more in-depth understanding of the field emission properties of tungsten single-tip field emitters (STFEs) coated with a several tens of nanometer thin barrier of Al2O3. The introduction of an additional barrier into the metal-vacuum interface system of the emitter can be beneficial to improve its performance. The tungsten emitters were prepared using a two-step electrochemical drop-off etching technique. Thin oxide barrier coatings were prepared by using low-temperature atomic layer deposition (ALD), a chemical vapor deposition technique. Field emission was studied in an internally developed field emission microscope (FEM) working in UHV vacuum (< 1·10−7 Pa), and the experimental field emission data were analyzed by the so-called Murphy-Good plotsThe value of the local work function of the grown oxide layer were investigated using Ultra-violet photoelectron spectroscopy (UPS).
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Defectoscopy of thin polymer layers using computer vision
Podstránský, Jáchym ; Sobola, Dinara (referee) ; Knápek, Alexandr (advisor)
Při procesu elektronové litografie jedním z prvních kroků je ovrstvování substrátu, waferu, tenkou vrstvou polymerního rezistu. V průběhu ovrstvování dochází k defektům, které mohou ovlivňovat expozici a tudíž i funkčnost finální nanostruktury. Kontrolou kvality naneseného rezistu před expozicí je možně se těmto místům s defekty vyhnout. Tento proces je možné provádět ručně pomocí světelného mikroskopu, ale je to časově náročný proces. V rámci této bakalářské práce vzniklo zařízení, které tyto defekty dokáže určit automaticky. Jde o rastrovací zařízení, které díky kombinaci dvou krokových motorů a optické kamery pořídí snímky požadované oblasti waferu a ty poté za pomoci umělé inteligence zanalyzuje. Uživateli je poté poskytnut dokument v ktérém je zapsána velikost, pozice a typ každého z nalezených defektů.
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Analysis and characterisation of spirally-arranged field-emission nanostructure
Ondříšková, Martina ; Sobola, Dinara (referee) ; Knápek, Alexandr (advisor)
Katody obsahující pole emitorů s vysokým poměrem stran budí velký zájem jako elektronové zdroje pro vakuová zařízení. Ve snaze maximalizovat proud a proudovou hustotu byly navrženy hustší pole emitorů. To však vedlo k nežádoucím účinkům, jako je stínění pole, způsobené přítomností okolních emitorů v poli. Pro snížení efektu stínění, a tím pádem zvýšení proudové hustoty, bylo navrženo pole emitorů s uspořádáním inspirovaným přírodním principem fylotaxe. Takto navržená struktura mikropilířů byla vytvořena pomocí elektronové litografie a reaktivního iontového leptání. K vytvoření ultra ostrých hrotů s poloměrem v řádu desítek nanometrů na vrcholu každého mikropilíře byla použita technika leptání black siliconu. Analýza topografie vzorku byla provedena pomocí rastrovacího elektronového mikroskopu. Pro stanovení výstupní práce byla použita ultrafialová fotoelektronová spektroskopie. Pro zjištění emisních vlastností vyrobených struktur byl zkonstruován emisní mikroskop, jehož elektronové dělo bylo upraveno tak, aby vyrobená struktura sloužila jako katoda. Graf Murphy-Good byl použit k analýze dat o emisních vlastnostech, na které byl aplikován ortodoxní test pro kontrolu validity. Pro sledování fluktuací proudu bylo provedeno měření stability.
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Correlative measurement of cathodoluminescence using SEM and SPM techniques
Černek, Ondrej ; Knápek, Alexandr (referee) ; Spousta, Jiří (advisor)
The diploma thesis deals with the combined use of SEM and SPM techniques using optical fiber, which is used to collect the cathodoluminescent signal in close proximity to the sample. The thesis also includes a research section, which lists description of CPEM technique, the techniques used to modify the optical fiber, theoretical introduction to cathodoluminescence and techniques used to measure it. The practical part discusses the obtained measurement results and the problems that occurred in the process of modification of the optical fiber, its use as an SPM probe and in the measurement of cathodoluminescence active materials.
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