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Investigation of CO oxidation on tin-cerium oxides by means of photoelectron spectroscopy and temperature-programmed reaction.
Václavů, Michal ; Bábor, Petr (referee) ; Matolín, Vladimír (advisor)
Metal-oxide and oxide-oxide interactions play an important role in heterogeneous catalysis. They influence electronic and crystallographic structure of catalyst surfaces, and consequently their adsorption properties. Nanosized powders of CeO2 supported tin oxide exhibit very good activity in NO reduction by CO. In order to contribute to the elucidation of the reaction mechanism we studied properties of SnO2/CeO2 by investigating the thin film model systems SnO2/CeO2/SiO2 prepared by rf-magnetron sputtering of ceria that were doped by tin oxide by means of thermal decomposition of tin acetate in air. The catalyst composition was characterized by photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The CO and NO reaction was investigated by means of a chip flow micro-reactor.
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Development of the sample holder for electrical diagnostics in UHV SEM
Axman, Tomáš ; Pavera, Michal (referee) ; Bábor, Petr (advisor)
This bachelor thesis focuses on design and testing of a sample holder enabling for cooling and heating of the sample in ultra-high vacuum apparatus for scanning electron microscope, developed in cooperation with Tescan company. In the theoretical part the currently used sample holders in similar UHV systems are described and their positives and negatives are discussed including material selection. The experimental part describes designing of the sample holder with respect to the required number of electrical contacts for measuring electrical properties of the samples and UHV compatibility. Measurement and testing of the manufactured sample at low and high temperatures is presented.
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Design of the carbon atomic source for deposition of graphene in UHV
Čalkovský, Vojtěch ; Bábor, Petr (referee) ; Mach, Jindřich (advisor)
This bachelor's thesis deals with the design of the atomic carbon source for deposition of graphene layers in UHV conditions. In the first part are briefly described the problems of epitaxial growth, the theory of atomic beams and theory of sublimation. The second part is aimed on graphene description, namely on his properties and on the growth of graphene layers, especially by molecular beam epitaxy. The third part contains brief description of detection and analysis methods of carbon atomic beams. In the practical part of this bachelor's thesis the design and the numeric calculations were made in Simion 8.0 and EOD program. Afterwards the atomic carbon source was constructed. In the conclusion are discussed the obtained results.
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Analysis of Trench Insulated Gate Bipolar Transistors
Karlovský, Juraj ; Polčák, Josef (referee) ; Bábor, Petr (advisor)
This thesis is focused on the selection and optimalization of suitable analytical methods for study of TIGBT (Trench Insulated Gate Bipolar Transistor) structures with a use of methods, that depict material composition of the studied sample. The theoretical part contain explana-tions of the analytical methods used for measurements and basic principle of operation of an TIGBT transistor. The practical part contain the methodic of measurements and the evaluation of the obtained data and design of optimal procedures in done experiments.
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Organic materials for molecular quantum bits
Tuček, Marek ; Bábor, Petr (referee) ; Čechal, Jan (advisor)
In this thesis we briefly outline the properties and utilization of metal phthalocyanines, the procedure of iron phthalocyanine thin film deposition on Si(100), the supplementary post-deposition analysis by XPS and the equipment used to measure X-ray reflectivity. Further we describe the theoretical description of physical background of X-ray diffraction on a crystal, the measurement of X-ray reflectivity and evaluation of acquired data, focusing on determination of the thin film thickness, identification of its crystal structure and lattice parameters. It has been found out that iron phthalocyanine thin films deposited on a substrate at room temperature grow as an alpha-phase in the shape of needles perpendicular to substrate surface, so the film thickness, due to high rougness of the film, can be only estimated with the help of Scherrer equation for long depositions. In the case of shorter depositions (and thus lower roughness) the Kiessig fringes method can be used. By the post-deposition annealing we were not able to induce a phase transition; at required temperatures all the material on the substrate evaporated. By a deposition on a substrate heated to 160°C we acquired considerably rough film with unclear crystalline phase.
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Electron Beam Micromachining of Nonmetalic Materials
Dupák, Libor ; Mrňa, Libor (referee) ; Bábor, Petr (referee) ; Lencová, Bohumila (advisor)
The thesis deals with electron beam micromachining of nonmetallic materials like glass, ceramics and plastics. A brief description of the device on which the experiments were carried out is included; the author has participated on its development. Main topic is experimental study of influence of main electron beam parameters on results of machining. Examined parameters include accelerating voltage, beam current, focusing and speed of machining. Influence of beam deflection is analyzed. Method of sequential machining by repeated passes of the electron beam is presented. Main examined materials are quartz glass, alumina and selected plastics. The usefulness of the technology is shown by several practical applications.
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Analysis and modification of thin layers using ion beams
Jonner, Jakub ; Lörinčík, Jan (referee) ; Bábor, Petr (advisor)
This diploma thesis deals with analysis and modification of thin layers using ion beams. The first part of this diploma thesis deals with phenomena accompanying ion beam bombardment of solid matter. The second part of this diploma thesis is concerned with Secondary Ion Mass Spectroscopy (SIMS) and Low Energy Ion Scattering (LAIS). This work convey some basic information about these two techniques and it also deals with some benefits result in their connection into parallel depth profiling mode (such as better depth resolution of the LEIS profile, quantification of the SIMS). These benefits are demonstrated on MoSi film measurement. Within the framework of this thesis a new UHV manipulator was designed. This new UHV manipulator is equipped with precise stepper UHV motor and since the proportions are smaller, the manipulation with a sample in a space limited UHV chamber is much more comfortable and more precise. The third part of this diploma thesis deals with ion-beam induced transformation of epitaxially grown Fe films with thickness of 22 monolayer (ML) and 44 ML on Cu(100) single crystal at room temperature. Metastable Fe films of 22 ML thickness were prepared in CO pressure and 44 ML Fe films were prepared by co-evaporation of Fe with Fe64Ni36 (invar). Structural changes are analyzed by scanning tunneling microscopy and low-energy electron diffraction. The aim of this thesis is to discuss the influence of the sputtering parameters such as ion dose and ion energy on the nucleation of bcc nanocrystals, their growth, final shape and size. The influence of different Ni concentration on stability of 44 ML thick Fe films is also discussed.
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