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Characterization of electronic properties of nanowires for electrochemistry
Kovařík, Martin ; Čech, Vladimír (oponent) ; Kolíbal, Miroslav (vedoucí práce)
Electrochemical methods are widely used in many applications (e.g. sensing, energy storage or catalysis) with the advantage of their inexpensive instrumentation. In order to understand redox processes taking place at electrodes, the knowledge of electronic band structure of the electrode materials is very valuable. This thesis focuses on the analysis of work function and valence band edge position of novel electrode materials, in particular indium tin oxide decorated with tungsten disulfide nanotubes. Ultraviolet Photoelectron Spectroscopy and Kelvin Probe Force Microscopy are used to measure those characteristics. A special emphasis is put on the electrode sample preparation to avoid misinterpretation of the results due to adventitious efects (e.g. contamination or surface modification).
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Analysis and characterisation of spirally-arranged field-emission nanostructure
Ondříšková, Martina ; Sobola, Dinara (oponent) ; Knápek, Alexandr (vedoucí práce)
Cathodes containing arrays of high aspect ratio field emitters are of great interest as sources of electron beams for vacuum electronic devices. The desire to maximize current and current density leads to the design of denser arrays. However, denser arrays lead to undesirable field shielding effects caused by the presence of surrounding emitters in the array. To reduce the shielding effect and thus maximize the field enhancement, an array of emitters was designed with an arrangement inspired by the natural phenomenon of phyllotaxis. The structure thus designed was created using electron beam lithography and reactive ion etching to form micropillars. A black silicon etching technique was used to create ultra-sharp tips with a radius in the order of tens of nanometers on the top of each micropillar. Analysis of the sample topography was performed by Scanning electron microscopy. Ultraviolet photoelectron spectroscopy was used to determine the work function. To find out the emission properties of the fabricated structures, a Field emission microscope was constructed and its electron gun was modified to experimentally use the fabricated structure as the cathode. A Murphy-Good plot was used to analyze the field emission data, to which the orthodoxy test was applied to check the validity of the experimental I-V data. Current stability measurement was performed to observe current fluctuations.
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Analysis and characterisation of spirally-arranged field-emission nanostructure
Ondříšková, Martina ; Sobola, Dinara (oponent) ; Knápek, Alexandr (vedoucí práce)
Cathodes containing arrays of high aspect ratio field emitters are of great interest as sources of electron beams for vacuum electronic devices. The desire to maximize current and current density leads to the design of denser arrays. However, denser arrays lead to undesirable field shielding effects caused by the presence of surrounding emitters in the array. To reduce the shielding effect and thus maximize the field enhancement, an array of emitters was designed with an arrangement inspired by the natural phenomenon of phyllotaxis. The structure thus designed was created using electron beam lithography and reactive ion etching to form micropillars. A black silicon etching technique was used to create ultra-sharp tips with a radius in the order of tens of nanometers on the top of each micropillar. Analysis of the sample topography was performed by Scanning electron microscopy. Ultraviolet photoelectron spectroscopy was used to determine the work function. To find out the emission properties of the fabricated structures, a Field emission microscope was constructed and its electron gun was modified to experimentally use the fabricated structure as the cathode. A Murphy-Good plot was used to analyze the field emission data, to which the orthodoxy test was applied to check the validity of the experimental I-V data. Current stability measurement was performed to observe current fluctuations.
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Characterization of electronic properties of nanowires for electrochemistry
Kovařík, Martin ; Čech, Vladimír (oponent) ; Kolíbal, Miroslav (vedoucí práce)
Electrochemical methods are widely used in many applications (e.g. sensing, energy storage or catalysis) with the advantage of their inexpensive instrumentation. In order to understand redox processes taking place at electrodes, the knowledge of electronic band structure of the electrode materials is very valuable. This thesis focuses on the analysis of work function and valence band edge position of novel electrode materials, in particular indium tin oxide decorated with tungsten disulfide nanotubes. Ultraviolet Photoelectron Spectroscopy and Kelvin Probe Force Microscopy are used to measure those characteristics. A special emphasis is put on the electrode sample preparation to avoid misinterpretation of the results due to adventitious efects (e.g. contamination or surface modification).
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