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Growth of 3D Structures Induced by Electron Beam on Ceramic Substrates
Bukvišová, Kristýna ; Čechal, Jan (referee) ; Salamon, David (advisor)
Vystaví-li se vzorek působení elektronového svazku, dojde na jeho povrchu ke strukturním změnám. Jednou z těchto změn je vertikální růst 3D struktur na keramických materiálech. V práci jsou zkoumány podmínky nutné pro takový proces. Nárůst teploty často zapříčiní povrchové změny, proto je v práci proveden výpočet ohřevu materiálu elektronovým svazkem. Dále je zkoumán vliv různých parametrů svazku na růst 3D struktur, závislost objemu a rozměrů je analyzována pomocí AFM. Výsledný odhad nárůstu teploty se pohybuje v řádech jednotek, maximálně desítek K. Výrazný objemový růst je pozorován pro nízká urychlovací napětí a malé proudy. Výška vzniklých struktur dosahuje 100 nm za minutu a je nepřímo úměrná velikosti proudu.
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Organic materials for molecular quantum bits: deposition and chemical and morphological analysis
Komora, Mojmír ; Mach, Jindřich (referee) ; Čechal, Jan (advisor)
This bachelor thesis deals with an experimental preparation and analysis of ultra thin films of iron phtalocyanines on silicon substrates with goal to describe parameters of films prepared under different conditions, e.g deposition time or substrate temperature. Preparation of samples was done using MBE method under conditions of ultrahigh vacuum in vacuum chamber. Analysis of chemical composition and morfology of prepared films was done with methods of X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy and Atomic Force Microscopy, respectively.
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Epitaxial growth of cobalt islands via oxide mediated epitaxy
Stará, Veronika ; Kolíbal, Miroslav (referee) ; Čechal, Jan (advisor)
This bachelor thesis deals with preparation, growth and analysis of cobalt thin films. The films are formed on silicon (111) samples covered with a thin layer of native oxide SiO2. Cobalt thin films were prepared using oxide mediated epitaxy method with the effusion cell as a source of cobalt atoms. Composition and morphology of the resulting Co system was studied as a function of the annealing temperature. Another goal of this research was to determine the dependence of the final island shape on the amount of deposited material and substrate orientation. The prepared structures were analyzed using X-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy. To determine the thickness of subsurface islands the samples were etched in buffered hydrofluoric acid and analyzed using above mentioned methods.
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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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Single Atomic Catalysts
Závodný, Adam ; Švec,, Martin (referee) ; Čechal, Jan (advisor)
Single atom catalysts are prospective class of materials, which holds promises to reach the ultimate limit of improvement in catalyst performance, selectivity, lifetime and cost reduction. The ability to efficiently capture the adsorbates at the active sites is the key prerequisite for catalytic transformation to the products. In this respect, our experimental study aims to describe the interaction of gas molecules (H2O, CO, O2 and NO) with single metal atoms (Rh, Ir, Cu) on the magnetite surface employing scanning tunneling microscopy.
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Optical response of asymmetric plasmonic structures
Babocký, Jiří ; Kolařík, Vladimír (referee) ; Čechal, Jan (advisor)
This diploma thesis deals with study of resonance modes of plasmonic structures. First part provides an overview of theoretical models, which explain the resonanace modes in plasmonic structures. Next part describes technology of electron beam lithography. First section of experimental part deas with technological processes leading to an improvement of resulting structures made by electron beam lithography that is followed by lift-off process. Last part focuses on a study of reflectance spactra of plasmonic antenas and the identification of resonance modes.
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Selective growth of metallic materials.
Šimíková, Michaela ; Schneeweiss, Oldřich (referee) ; Čechal, Jan (advisor)
The diploma thesis deals with selective growth of cobalt thin films on lattices created by focused ion beam on Si(111) substrates with thin film of silicon dioxide. Further, the growth and morphology of iron thin films growing on Si/SiO2 substrate without modification was studied. In the last part, thin film of a-C:H, influence of preparation parameters on their growth and ratio of sp2 and sp3 bonds, was investigated. For analysis of those films XPS, AFM, and SEM metods were used.
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Thin films modification by focussed ion beam.
Faltýnek, Petr ; Čechal, Jan (advisor)
The purpouse of the master's thesis is study problematic of focused ion beams and their material influence. In this thesis are described interactions in the sample after impact of ion beam, use and applications of FIB systems. Second part of thesis are simulations of ion influence on different kinds of materials by the help of SRIM program.
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