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Application of oxygen atomic beams
Mikerásek, Vojtěch ; Čech, Vladimír (referee) ; Mach, Jindřich (advisor)
V diplomové práci je popsán návrh, konstrukce a testování termálního zdroje svazku atomárního kyslíku, který je určen k růstu tenkých oxidových vrstev v podmínkách ultra vysokého vakua. První kapitola pojednává o teorii spjaté s termální disociací a tvorbou atomárních svazků. Dále jsou uvedeny hlavní typy zdrojů svazků atomárního kyslíku a jeho aplikace. Experimentální část je věnována samotnému návrhu zařízení, konstrukci a jeho složení. V poslední část je popsáno testování vlivu atomárního kyslíku na vznik oxidových vrstev (stechiometricky Ga2O3) na nanokapičkách Ga na křemíkovém substrátu připraveného molekulární svazkovou epitaxí. Chemické složení a morfologie připravených nanostruktur jsou zkoumány metodou XPS, SEM a TEM.
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Deposition of GaN nano structures on Si(111) 7x7
Šťastný, Jakub ; Horák, Michal (referee) ; Mach, Jindřich (advisor)
The thesis is focused on the study of growth of 2D GaN nanocrystals on Si(111) 7x7. In the theoretical part of this thesis the properties of 3D and 2D GaN, main methods used for growth of GaN and 2D GaN and applications of GaN are described. The experimental part of this thesis describes in detail the method of low temperature droplet epitaxy with assistance of ions, which was used for series of deposition of 2D GaN under different angles of ion beam. The deposition was done in the complex UHV system in the ÚFI VUT labs in Brno. The nanocrystals were analysed by SEM and AFM.
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Optimization of ion source with saddle field
Zálešák, Marek ; Voborný, Stanislav (referee) ; Mach, Jindřich (advisor)
The goal of my bachelor's thesis was to make literature search about ion source applications. The next goal was to create models of saddle field ion source and find the best settings of the ion source. At first the most necessary changes were made to make the ion source operational. Then the deflection optics was developed that cause a deviation of the beam from the geometric axis of the ion source.
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The oxygen modification of the graphene structures for biosensors
Mikerásek, Vojtěch ; Bartošík, Miroslav (referee) ; Mach, Jindřich (advisor)
The bachelor thesis deals with the modification of CVD graphene by oxygen atoms. The theoretical part describe the structure of graphene oxide and its physical properties. Methods of production of this material and its use in biosensors are also described. The practical part describes the preparation of monolayer graphene on a silicon wafer. The main attention was paid to the oxidation of graphene by atomic oxygen and its modification in oxygen plasma. The samples were measured during process of oxidation at individual time intervals using XPS.
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UV detection by Grafen/GaN structures
Kostka, Marek ; Piastek, Jakub (referee) ; Mach, Jindřich (advisor)
This bachelor thesis covers fabrication as well as the study of behavior of UV sensor based on galium nitride structures on graphene substrate. The sensor takes advantage of high mobility of charge carriers in graphene and UV selective sensitivity of GaN nanoctystals. This combination exhibits a potential for being a UV sensor because of the unique properties brought by both materials. The first part of this work describes graphene, galium nitride and graphene/GaN heterostructure with their properties and fabrication processes. The second part includes full description of already used fabrication process and characterization of the optical and electrical behavior using photoluminiscence and transport properties measurements.
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Deposition of Ga nanostructures on graphene membranes
Severa, Jiří ; Mikulík, Petr (referee) ; Mach, Jindřich (advisor)
This diploma thesis deals with the preparation of the graphene membranes for depo-sition of gallium atoms by the molecular beam epitaxy. In the first part properties ofgraphene and methods of its production are described. Second part focuses on the gra-phene membranes, their specific properties, applications and methods of production. Thirdpart describes growth theory of the thin films. Practical part is focused on preparationof graphene membranes, which consists of covering the holes in the silicon substrate bygraphene layer. For that mechanical exfoliated and chemical vapor deposited graphenewere used. Subsequently, gallium atoms were deposited on these membranes by molecularbeam epitaxy and in situ observed by scanning electron microscopy.
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The deposition of Ga and GaN nanostructures on silicon and graphene substrate
Novák, Jakub ; Jarý, Vítězslav (referee) ; Mach, Jindřich (advisor)
The thesis is focused on the study of properties of GaN nanocrystals and Ga structures on the surface of silicon and graphene substrate. In the theoretical part of this thesis, the basic properties of Ga/GaN and graphene are described, as well as their applications or connection of both structures together in different devices. The ability of metal nanoparticles to enhance not only photoluminescence, due to the interaction of the material with surface plasmons, is also shown in several examples. The experimental part of the work first deals with the production and characterization of graphene sheets prepared by Chemical Vapor Deposition. Ga/GaN growth on both types of substrates was performed in a UHV chamber using an effusion cell for Ga deposition and an atomic ion source for nitridation. Prepared structures were characterized using various methods (XPS, SEM, AFM, Raman spectroscopy or photoluminescence). In the last step, GaN nanocrystals were coated with Ga islands to study the photoluminescence enhancement.
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The deposition of CaF2 ultrathin layers on graphene substrate
Caesar, Radek ; Nebojsa, Alois (referee) ; Mach, Jindřich (advisor)
This master’s thesis is focused on preparation and analysis of ultrathin CaF2 (calcium fluoride) films on a graphene substrate. CaF2 was deposited in UHV conditions at substrate temperatures in the range from 20 °C to 400 °C. The material was deposited on Si(111) with a native SiO2 layer and on a substrate with a CVD graphene layer. The deposited films were analyzed by XPS, AFM and SEM. Moreover four different sample holders for deposition purposes were designed in this work.
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Design of manipulator for TEM
Melichárek, Václav ; Doležel, Pavel (referee) ; Mach, Jindřich (advisor)
The topic of this master’s thesis is the design of a sample manipulator for TEM. Regarding which the segment of the sample manipulator used to move the sample in the direction of the x-axis (so-called x-stage) was designed. The introductory theoretical part is concerned with a brief description of transmission electron microscopy focused on the imaging methods used in TEM and the procedures of preparing and loading TEM samples. The theoretical part follows with the design of precise mechanisms, especially with respect to the inaccuracies of their operation and the technological aspect of the design. In the practical part, a detailed analysis of the design of the x-stage is presented. Kinematics and dynamics of the mechanism is analyzed in depth, following with the description of the overall design of the mechanism and some of its parts in detail.
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