Original title: Studium interakce jednoduchých organických molekul s povrchem oxidu ceru
Translated title: Interaction of simple organic molecules with cerium oxide surfaces
Authors: Ormoš, Martin ; Matvija, Peter (advisor) ; Sobotík, Pavel (referee)
Document type: Bachelor's theses
Year: 2023
Language: cze
Abstract: [cze] [eng]
Práca sa zaoberá tenkými epitaxnými vrstvami oxidu céru (CeO2) a oxidu céru s nanočasticami platiny (CeO2/Pt) pripravenými na substráte Cu(111). Povrch vrstiev bol charakterizovaný pred expozíciou molekulami etanolu, po expozícii, po ohreve v UHV na 725 K a po ohreve na 725 K v O2 atmosfére pri tlaku p = 5 × 10−7 mbar pomocou metód LEED (nízko-energetická elektrónová difrakcia), XPS (röntgenová fotoelektrónová spektroskopia) a STM (skenovacia tunelová mikroskopia). Vrstvu CeO2/Pt sme okrem etanolu vystavili aj 2 mbar metánu a 2, 5 mbar zmesi metánu a kyslíku v pomere 1:1. Tento povrch sme pozorovali pomocou metódy NAP-STM za zvýšeného tlaku plynov. Zo získaných výsledkov vyplynulo, že jednoduché organické molekuly pri izbovej tep- lote na povrchu vytvárajú súvislú neusporiadanú vrstvu. Výraznejšie vrstva CeO2 s or- ganickými molekulami interaguje počas ohrevu v UHV, kedy atómy uhlíku desorbujú z povrchu a cér sa redukuje. Po ohreve v kyslíku sa cér reoxiduje. Aj po reoxidácii však povrch obsahuje veľké množstvo defektov rôzneho typu. Behom skenovania povrchu za prítomnosti zmesi kyslíku a metánu bolo pozorované výrazné zvýšenie jasu okolia doménových rozhraní vrstvy oxidu céru. Tento efekt bude podrobnejšie skúmaný v našich budúcich experimentoch. 1 In this work we prepare well defined thin epitaxy layers of cerium oxide (CeO2) and cerium oxide with nanoparticles of platinum (CeO2/Pt) on the Cu(111) substrate. The surface was characterized before exposition by ethanol molecules, after exposition, after annealing at 725 K in UHV and after annealing in O2 atmosphere at pressure p = 5×10−7 mbar at 725 K by LEED (low-electron energy diffraction), XPS (x-ray photoelectron di- ffraction) and STM (scanning tunnelling microscopy). Layer of CeO2/Pt was also exposed to 2 mbar of methane and 2, 5 mbar of methane and oxygen mixture in a ratio 1:1. This layer was observed by NAP-STM in higher pressures. In this work we have discovered that a disordered layer is formed on the CeO2 surface after exposure to the mixture of air and ethanol. Interaction of adsorbed molecules and ceria is increased during annealing in UHV, when carbon desorbs from the surface and cerium is reduced. After annealing in oxygen cerium is reoxidized. However, even after reoxidation, the surface contains a large number of defects of various types. Significant increase in brightness was observed in the proximity of domain interfaces of cerium oxide layers during scanning at higher pressures of oxygen. This effect will be studied more closely in our future experiments. 1
Keywords: STM|cerium oxide|organic molecules; STM|oxid ceru|organické molekuly

Institution: Charles University Faculties (theses) (web)
Document availability information: Available in the Charles University Digital Repository.
Original record: http://hdl.handle.net/20.500.11956/182604

Permalink: http://www.nusl.cz/ntk/nusl-531940


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Universities and colleges > Public universities > Charles University > Charles University Faculties (theses)
Academic theses (ETDs) > Bachelor's theses