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An influence of electron beam on thin oxide films
Kostyal, Michal ; Průša, Stanislav (referee) ; Čechal, Jan (advisor)
This bachelor work deals with a study of the influence of electron beam of scanning electron microscope on the surface of the SiO2/Si (100) – sample. In the work the electron and atomic force microscopy briefly described. The main objective of experimental part is to describe variation in the brightness of sample SiO2/Si (100) in Scanning electron microscope images. In this study is found that on the sample surface are created objects few nm high. The rest of the work is then devoted to measuring the dependence of the object’s high on different variables. Experiments are generally based on the selective irradiation of the sample surface by scanning electron microscope, measurement of irradiated parts using atomic force microscope and evaluation in the application Gwyddion.
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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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Non-thermal dehydrogenation of carboxylic acids on metal surfaces
Kugler, David ; Kolíbal, Miroslav (referee) ; Čechal, Jan (advisor)
Molecular self-assembly is the process of spontaneous arrangement basic adsorbate units into complex structures. Self-assembly systems could be used for atomically precise fabrication of functional nanostructures in the future. One of the possibilities to fabricate self-assembled molecular networks is to deposit the simple carboxylic acid molecules onto a clean metal substrate. The aim of this work is to describe the kinetics of the deprotonation process of 4,4´-biphenyldicarboxylic acid on Ag(100) due to CO exposure. A low-energy electron microscope was used to monitor phase transitions induced by changes in binding properties of molecules. The result of the work is a comprehensive view on the deprotonation process induced by exposure to CO. We found out that the deprotonation reaction depends on the shape and size of molecular islands, and we described the kinetics of individual phase transitions for different molecular coverages. We have also described the correlation between CO pressure and the rate of deprotonation.
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Atomic structure of FeRh(001) surface
Ondračka, Václav ; Bábor, Petr (referee) ; Čechal, Jan (advisor)
Alloy of iron-rhodium, Fe50Rh50, shows a low-temperature metamagnetic phase transition between its antiferromagnetic and ferromagnetic state. A detailed description of this transition using the tools of surface analysis has not yet been done. This bachelor’s thesis focuses on preparation and characterisation of the alloy’s clean surface using X-ray photoemission spectroscopy and low-energy electron diffraction. A flat field correction and a diffraction measurement callibration is done using a sample with known crystal lattice in order to quantify the diffraction results.
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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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Fabrication of Nanowires into Porous Alumina by Electrolysis
Staňo, Michal ; Čechal, Jan (referee) ; Škoda, David (advisor)
This thesis deals with preparation of metal nanowires based on electrodeposition from aqua solution of metallic salts into porous dielectric aluminium oxide templates. The theoretical part covers various bottom-up methods of nanowire preparation using a template, electrochemistry and electrodeposition overview. The Experimental part is focused on the nanowire (Ag, Cu, Ni-H) preparation by means of direct current and alternating current electrodepositon and geometrical characterization of fabricated nanowires by scanning electron and atomic force microscopy. Defects of commercially available and prepared porous alumina templates are mentioned. Branching and coalescence of nanowires are briefly discussed as well.
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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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Metal-organic networks on graphene surfaces
Kurowská, Anna ; Průša, Stanislav (referee) ; Čechal, Jan (advisor)
Molecular self-assembly is a spontaneous association of molecules and atoms into well-defined supramolecular structures. Understanding this process is key for preparation of structures with atomic precision. This thesis studies the supramolecular structure of tetrakyanochinodimetan molecules (TCNQ) and iron atoms on graphene grown on iridium crystal with the (111) surface. The surface analysis was performed by scanning tunneling microscopy, low-energy electron microscopy and x-ray photoelectron spectroscopy. The thesis introduces the growth process of a good quality graphene on Ir(111) and the synthesis of Fe-TCNQ networks 20 nm x 20 nm large and describes their structural properties. Three preferential orientations of Fe-TCNQ on graphene were identified. The networks will be used in follow-up studies targeting their magnetic properties.
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