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Analysis of one-dimensional structures using Kelvin Probe Force Microscopy
Kovařík, Martin ; Bartošík, Miroslav (referee) ; Kolíbal, Miroslav (advisor)
This bachelor's thesis deals with the use of Kelvin probe force microscopy (KPFM) for analysis of 1D nanostructures, namely germanium nanowires and tungsten disulfide (WS2) nanotubes. First part of this thesis is dedicated to the possibility of gold nanoparticles detection on germanium nanowires and also to the analysis of relevance of the KPFM method to measurements performed at various humidity. Second part deals with the measurement of surface potential changes on WS2 nanotubes induced by interaction with light. We have concluded, that relative surface potential changes can be measured at various humidity. This conclusion is also applied to study the interaction of WS2 nanotubes with monochromatic light. The experiment has revealed, that when exposed to light with defined wavelength, nanotubes coated with gold nanoparticles show opposite surface-potential changes as compared to pristine nanotubes, which indicates different physical processes under way.
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Characterization of sensitive nanomaterials for MOX gas sensors
Priščák, Juraj ; Gablech, Imrich (referee) ; Chmela, Ondřej (advisor)
This thesis deals with one-dimensional (1D) and two-dimensional nanomaterials (2D) in terms of their utilization for new types of gas sensors. Thesis focuses on study of sensing elements for gas sensors based on semiconductor metal oxide materials (MOX) and their manufacturing technology. The objective of the thesis is the design and implementation of a sensing elements formed by selected nanomaterials based on the structure of interdigital electrodes. The result of the practical part of the thesis is the characterization and comparison of materials in terms of their detection parameters in the presence of selected test gases. The first part of thesis hierarchically defines chemoresistive gas sensor, characterizes and explains its operation principle. Second part studies 1D and 2D nanomaterials of sensing elements for MOX chemoresistive gas sensors, contains a research of their properties and describes their methods of manufacturing and implementation. The last part deals with the implementation of the sensitive layer of the sensor with selected nanomaterials, characterizes and compares their detection properties.
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Preparation Techniques and Characterization of Electrodes with Nanostructured Surface
Hrdý, Radim ; Trnková, Libuše (referee) ; Janderka,, Pavel (referee) ; Hubálek, Jaromír (advisor)
Nowadays, nanostructures fixed on solid substrates and colloidal nanoparticles permeate through all areas of human life, in area of sensors and detection as well. This dissertation thesis deals with the fabrication of nanostructures on the surface of planar electrodes via self-ordered nanoporous template of aluminum trioxide. The nanofabrication, as one of many possible techniques, is used to increase the active surface area of electrodes by creating unique surface types with specific properties. These electrodes are very perspective in the applications, such as biomolecules electrochemical detection and measurement. The transformation of aluminum layer into non-conductive nanoporous template in the process of anodic oxidation is a fundamental technique employed to obtain the array of nanostructures in this thesis. The fabrication of high quality nanoporous membranes with narrow pore size distribution on various types of metallic multilayers is one of the key experimental parts in this work. Several problems associated with the production of the thin-film systems, including the dissolving the barrier oxide layer, are discussed and solved. Another part of this work deals with the use of nanoporous membrane as a template for the production of metallic nanostructures via electrochemical metal ions deposition directly into the pores. The obtained nanostructures as nanowires, nanorods or nanodots are characterized by the scanning electron microscopy and energy-dispersive or wavelength X-ray spectroscopy. The electrode surface, modified by gold nanostructures suitable for the detection of biomolecules, has been chosen for the electrochemical measurements, due to the gold biocompatibility. The nanostructured electrodes were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The effect of nanostructured surface geometrical parameters, including the size of the electrochemically active area, on the results of electrochemical measurements has been observed and compared to flat gold electrodes. Two model biomolecules, namely guanine and glutathione, have been chosen for the study of potential application of these nanostructures in biosensors.
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Preparation of nanowires for photonics
Mikula, Martin ; Grym, Jan (referee) ; Kolíbal, Miroslav (advisor)
This thesis is dealing with nanowires of zinc oxide and of cesium lead bromide. Main goal was a preparation of ZnO nanowires using MBE. This goal was partially achieved and growth of needle-like structures was observed. Another goal was characterization of already prepared ZnO nanowires. We successfully determined polarity of their surfaces, examined the influence of lattice defects and assessed the result of their doping. Side goal of this work was characterization of nanostructures of cesium lead bromide. However, preparation of cesium lead bromide nanowires remains an open issue.
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Growth of highly doped ZnO nanowires
Andrýsek, Michal ; Macák, Jan (referee) ; Kolíbal, Miroslav (advisor)
This diploma thesis is about ZnO nanowires growth, their doping and analysis. High temperature and pressure oxidation of brass foil and deposition from effusion cell in oxidative atmosphere utilized for nanowires growth. The growth is affected by different temperature and pressure. It has been shown that under certain experimental conditions nanowires can be prepared by the former method. However, the growth was hindered when effusion cell was used.
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Growth of ZnO nanowires
Mikula, Martin ; Voborný, Stanislav (referee) ; Kolíbal, Miroslav (advisor)
In this thesis the most important properties of nanowires are briefly characterized and possible methods of their synthesis are described. Special attention is paid to zinc oxide nanostructures as well as VLS mechanism, which is crucial for explanation of nanowire growth. Furthermore, deposition chamber for growth of ZnO nanowires has been assembled and effusion cell for zinc has been tested. Testing of the cell revealed one major drawback of its design, which prevents its use for zinc deposition. Therefore, no growth of ZnO nanowires has been carried out and before it can be accomplished, the effusion cell has to be modified.
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Self-organized nanostructured oxide layers
Šťastná, Eva ; Pouchlý, Václav (referee) ; Jan, Vít (advisor)
Series of anodization experiments was conducted on pure aluminium (99,95 Goodfellow) substrates with the aim to map the possibilities and evaluate available techniques. Oxalic acid electrolyte was used for anodization at different voltage levels ranging from 20 to 60V, while current was always measured continuously during the experiment. The influence of substrate surface treatment, time and grain size of the substrate was documented for as anodized oxide structures using FEG-SEM. Well aligned and evenly distributed pores of the diameters ranging 20- 35 nm were achieved. Extremely fine pores down to 10 nm were achieved using the step-down technique governed by current limitation. Further post-anodizing treatment was evaluated – pore widening by chemical and electrochemical etching, which resulted in pores 80nm wide. The feasibility of electrodeposition of metallic wires directly into the AAO structure without substrate removal was evaluated. DC, AC symmetric and non-symmetric voltage setups were used. The deposition experiments results varied strongly depending on the post anodization treatment. For combination of pore-widening after anodizing with step-down stage, the deposition of copper nanowires was achieved. For simple step-down procedure, creation of very fine copper particles was realized using non-symmetric AC deposition. Further experiments and feasibility of metals electrodeposition in the AAO pores without substrate removal is discussed.
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Electron beam modification of nanostructure growth
Kilian, Jakub ; Voborný, Stanislav (referee) ; Bábor, Petr (advisor)
This bachelor's thesis focuses on the further development of a method for modifying the surface of germanium using alloy Au-Ge droplets. A focused electron beam, which is brought in close proximity to the droplet, is utilized for thermomigration-induced motion of the droplets. The thesis is divided into two parts. The first part is dedicated to explaining the fundamental principles that are essential for a proper understanding of the conducted experiments. The theoretical overview also includes an introduction to the individual instruments utilized in the experimental section. In the practical part, the movement of Au-Ge droplets and the resulting surface morphology left by the droplets' passage were initially examined. The remaining portion of the practical research concentrated on utilizing the focused electron beam for controlled growth of nanowires in the VLS process.
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Analysis and modifications of 1D nanostructures
Kachtík, Lukáš ; Houben,, Lothar (referee) ; Šlouf,, Miroslav (referee) ; Kolíbal, Miroslav (advisor)
Tato disertační práce se zabývá strukturální a spektrální analýzou 1D nanostruktur. Nejprve jsou představeny techniky pro určení krystalografické struktury, stejně jako spektroskopické techniky, které byly použity pro tuto analýzu – jejich popis a možnosti. Disertace pokračuje analýzou InAs a Ge nanodrátů, kde se analýza zaměřuje na krystalografický směr růstu těchto nanodrátů a jejich dopování. Následující kapitola zahrnuje analýzu vícestěnných WS2 nanotrubic pomocí Ramanovy spektroskopie a postup, pomocí kterého by bylo možné spočítat počet stěn těchto nanotrubic. Disertace pokračuje analýzou WOx nanodrátů, které vznikly po oxidaci WS2 nanotrubic. Následuje nejobsáhlejší kapitola zaměřující se na určení chirality nejsvrchnější stěny vícestěnné WS2 nanotrubice, která mimo jiné odhaluje i proces růstu jednotlivých stěn při tvorbě těchto nanotrubic. V příloze je pak popsán postup, při kterém byl vytvořen autoregulační prvek vyhřívání držáku vzorků rastrovacího elektronového mikroskopu – jak hardwarová, tak softwarová část.
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