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The importance of the deformation necks in forming
Kučera, Radek ; Podaný, Kamil (referee) ; Peterková, Eva (advisor)
The aim of this bachelor thesis is elaboration of the research themed deformation necks in forming technology. Particular methods of spreading of the deformation necks are described in this thesis. The advantages and disadvantages are reviewed also as its use in practice. Moreover comparison of the most used methods of spreading of deformation necks had been carried out. Further the connection of deformation necks and forming limit diagram had been stated. The thesis also presents summary of the automated methods of deformation necks analysis.
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Characterisation for the cold field-emission sources intended for electron microscopy
Vašíček, Martin ; Tománek, Pavel (referee) ; Grmela, Lubomír (advisor)
This work deals with the theoretical foundations of electron emission into vacuum, various types of emissions, focused on the cold-emission and Schottky emission and the principle of quantum tunneling. The next part deals with the technical implementation of electron sources with a detailed study of the methodology of laboratory production of cathodes by electrochemical etching and construction of electron microscopes, using field-emission sources. This work also contains methods for measuring, processing and evaluation of electrical characteristics of emission sources.
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Preparation and analysis of nanostructures in UHV conditions
Gloss, Jonáš ; Spousta, Jiří (referee) ; Mach, Jindřich (advisor)
Cílem této bakalářské práce bylo skoumání přípravy a analýzy nanostruktur v podmínkách vysokého vakua (VV). Teoretická část klade důraz na gallium nitridové (GaN) nanostruktury. Ty pak byly analyzovány rastrovacím tunelovacím mikroskopem (RTM). Aby bylo možné analyzovat připravené vzorky ve VV RTM, bylo provedeno elektrochemické leptání wolfrámového drátu. Tato práce zhrnuje postup k vytvoření wolfrámových hrotů pro RTM. Kapitola o výrobě wolfrámových hrotů zahrnuje popis princípu elektrochemického leptání. Obrázky vyleptaných hrotů byly provedeny pomocí rastrovacího elektronového mikroskopu. Zaostřování hrotů pak bylo vykonáno fokusovaným iontovým svazkem. V této práci je také představena metoda pro opětovné ostření RTM hrotů elektronovým svazkem, vykonávaná in-situ. Bylo dokázáno, že je možné rutinně obdržet wolfrámové hroty s poloměrem křivosti rádovo v nanometrech.
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Electrochemical etching of graphite tips for potential use in nanoscience
Jonáš, Adam
The main goal is to find an easy, and more importantly, cheap process of producing sharp tips for the potential use in an atomic force microscope (AFM) or as a source of electrons utilizing cold field emission. This objective is being achieved by the method named electrochemical etching, and the used material is cheap and easily accessible. For this experiment, graphite leads of different hardnesses were used, etched with two types of etching solutions. The first solution contained potassium hydroxide (KOH) dissolved in water and the second contained sodium hydroxide (NaOH), also dissolved in water. Different ratios of chemicals were tried for the manufacturing process. Hardnesses of leads were 2B, B, and HB. After the process of etching, products were examined with a scanning electron microscope (SEM). The radius of tips was measured, and results were compared and evaluated. Stating on the output data of tips, it can be said, that goal was achieved, and tips can be used for their potential purpose. There would be needed another research about how well they fit to work.
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Preparation Of Cold Field Emission Cathodes Withultra Sharp Tips
Jurčík, Michal
This article deals with preparation of very sharp cold field emission cathodes made from polycrystalline tungsten wire which is widely used by other researchers and manufacturers. Common manufacturing process of electrochemical etching in NaOH solution is improved by separation of electrolyte surfaces between anode and cathode. This method prevents hydrogen bubbles, formed on cathode, to fine down the electrolyte surface near anode that cause shockwaves which affect the progress of etching. Separation of surfaces leads to sharper tips of the final cathode which is the main goal of my research.
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Automated Electrochemical Etching Prototype for Cold Field Emission Cathodes
Jurčík, Michal
This article deals with a setup for automated cold cathode etching, its difficulties and benefits. As the method is well know there are no articles which describes this procedure in detail at least for tungsten wires from which cathodes are made. To provide stable and repeatable process of cathodes manufacturing, the experimental setup was proposed with full hardware control with aim to assure etching circuit disconnection in order of hundreds of nanoseconds.
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Electrochemical etching of silicon
Vrzal, Pavel ; Voborný, Stanislav (referee) ; Šamořil, Tomáš (advisor)
The electrochemical etching is very used technique for semiconductor materials modification. Different structures which find applications in many fields (biotechnology, nanotechnology or electronics) can be prepared by this technique. The task of bachelor’s thesis was preparation of porous silicon using electrochemical etching. At first, a study dedicated to porous Si was carried out. Experimental part of this work deals with a design of etching cell which was used for preparation of porous silicon by electrochemical etching. In addition, the porous Si was prepared by metal assisted chemical etching. Subsequently, created structures were analyzed by scanning electron microscopy. Photoluminescence properties of porous silicon were studied as well.
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Electrochemical etching of silicon
Vrzal, Pavel ; Voborný, Stanislav (referee) ; Šamořil, Tomáš (advisor)
The electrochemical etching is very used technique for semiconductor materials modification. Different structures which find applications in many fields (biotechnology, nanotechnology or electronics) can be prepared by this technique. The task of bachelor’s thesis was preparation of porous silicon using electrochemical etching. At first, a study dedicated to porous Si was carried out. Experimental part of this work deals with a design of etching cell which was used for preparation of porous silicon by electrochemical etching. In addition, the porous Si was prepared by metal assisted chemical etching. Subsequently, created structures were analyzed by scanning electron microscopy. Photoluminescence properties of porous silicon were studied as well.
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Electrochemical etching of silicon
Vrzal, Pavel ; Voborný, Stanislav (referee) ; Šamořil, Tomáš (advisor)
The electrochemical etching is very used technique for semiconductor materials modification. Different structures which find applications in many fields (biotechnology, nanotechnology or electronics) can be prepared by this technique. The task of bachelor’s thesis was preparation of porous silicon using electrochemical etching. At first, a study dedicated to porous Si was carried out. Experimental part of this work deals with a design of etching cell which was used for preparation of porous silicon by electrochemical etching. In addition, the porous Si was prepared by metal assisted chemical etching. Subsequently, created structures were analyzed by scanning electron microscopy. Photoluminescence properties of porous silicon were studied as well.
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Characterisation for the cold field-emission sources intended for electron microscopy
Vašíček, Martin ; Tománek, Pavel (referee) ; Grmela, Lubomír (advisor)
This work deals with the theoretical foundations of electron emission into vacuum, various types of emissions, focused on the cold-emission and Schottky emission and the principle of quantum tunneling. The next part deals with the technical implementation of electron sources with a detailed study of the methodology of laboratory production of cathodes by electrochemical etching and construction of electron microscopes, using field-emission sources. This work also contains methods for measuring, processing and evaluation of electrical characteristics of emission sources.
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