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Environment-Dependent Surface Structure of Fe2O3(012)
Komora, Mojmír ; Dubroka, Adam (oponent) ; Čechal, Jan (vedoucí práce)
This thesis deals with study of alpha-Fe2O3(012) exposed to water environment. The up to date knowledge of different oxides with focus on alpha-Fe2O3 and its R-cut (012) non polar surface is briefly reviewed. The experimental part of this work start with the description of the state of the art ultra high vacuum compatible experimental setup for dosing liquid water onto single crystal surfaces. Individual features of the system are thoroughly discussed and the tests of the system were performed on silver foil and on Fe3O4(001) single crystal surface. The chemical composition and surface morphology of the crystal after liquid water experiment is discussed. The proposed setup was used to study interaction of water with known (1x1) and (2x1) surface reconstruction of alpha-Fe2O3(012). The experimental data shows that water binds to both reconstruction disociatively with some molecular water bound to adsorbed hydroxyls. The (1x1) reconstruction appears to survive exposure to different pressures of water vapor, while the (2x1) seems to change into (1x1) after exposures to higher pressures or by exposing it to electron beam. Further, this thesis presents the first real time study of (1x1)-to-(2x1) transition by Low Energy Electron Microscopy. These results show iniciation of the transition at atomic step edges and defects, which then continues to the centers of terraces at lower temperatures. Onservation of gradual transition at higher temperatures suggets creation of numerous nucleation centers from which then (2x1) spread. The beam damage is believed to also play role in the transformation as documented in the thesis.
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Structural and magnetic properties of Fe-oxide layers prepared by inkjet printing on Si-substrate
Zažímal, František ; Svoboda, T. ; Dzik, P. ; Homola, T. ; Jirásková, Yvonna
Magnetic films with two, four, six, and eight layers were prepared using 2D inkjet printing on the 333 K heated Si-substrates at ambient conditions. The microstructure, phase composition of layers, and magnetic studies were investigated using wide spectrum of experimental methods with the aim to find the optimal conditions for producing magnetic sensors by digital printing technology in the near future. As the magnetic compound, the hematite powder was chosen and its milling with Si-binder dissolved in dowanol using glass balls and vial to prevent contamination was done to prepared suspension appropriate for printing. It is shown that hematite transformed markedly into maghemite, thus the layers consisted of small amount hematite and dominant maghemite phases determining the magnetic properties. From the viewpoint of magnetic behavior, the highest saturation magnetization and the lowest coercivity was obtained at the sample with 8 layers.
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Formation, Functionalization and Characterization of 2D Materials on Crystalline Supports
López-Roso Redondo, Jesús Rubén ; Švec, Martin (vedoucí práce) ; Gonzáles Pascual, César (oponent) ; Mysliveček, Josef (oponent)
Abstrak: V této práci je studován růst 2D materiálů grafénu a FeO2 na krystalických substrátech pomocí řady povrchově citlivých metod. Jsou prozkoumány mechanismy růstu grafénu v ultravysokém vakuu a atmosférickém tlaku argonu, je popsáno jednoduché zařízení na výrobu vysoce kvalitního monokrystalického grafénu na SiC. Charakterizace elektronických a chemických vlastností borem a dusíkem dopovaného grafénu je provedena metodami STM/AFM s hroty funkcionalizovanými molekulou CO a podpořena výpočty DFT. Je též zkoumána chemická interakce testovací molekuly (FePc) s dopovaným grafénem. Dlouhodobě nevyřešený spor ohledně tzv. "biphase" (tj. dvoufázového) modelu rekonstrukce α - Fe2O3(0001) je vyřešen odhalením kompletní FeO2 vrstvy pro tuto fázi. Struktura této povrchové vrstvy je zkoumána metodami STM, LEEM a pomocí DFT výpočtů. Je podán detailní popis cest k získání jednotlivých fází pokrývajících celý povrch α - Fe2O3(0001).
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Environment-Dependent Surface Structure of Fe2O3(012)
Komora, Mojmír ; Dubroka, Adam (oponent) ; Čechal, Jan (vedoucí práce)
This thesis deals with study of alpha-Fe2O3(012) exposed to water environment. The up to date knowledge of different oxides with focus on alpha-Fe2O3 and its R-cut (012) non polar surface is briefly reviewed. The experimental part of this work start with the description of the state of the art ultra high vacuum compatible experimental setup for dosing liquid water onto single crystal surfaces. Individual features of the system are thoroughly discussed and the tests of the system were performed on silver foil and on Fe3O4(001) single crystal surface. The chemical composition and surface morphology of the crystal after liquid water experiment is discussed. The proposed setup was used to study interaction of water with known (1x1) and (2x1) surface reconstruction of alpha-Fe2O3(012). The experimental data shows that water binds to both reconstruction disociatively with some molecular water bound to adsorbed hydroxyls. The (1x1) reconstruction appears to survive exposure to different pressures of water vapor, while the (2x1) seems to change into (1x1) after exposures to higher pressures or by exposing it to electron beam. Further, this thesis presents the first real time study of (1x1)-to-(2x1) transition by Low Energy Electron Microscopy. These results show iniciation of the transition at atomic step edges and defects, which then continues to the centers of terraces at lower temperatures. Onservation of gradual transition at higher temperatures suggets creation of numerous nucleation centers from which then (2x1) spread. The beam damage is believed to also play role in the transformation as documented in the thesis.
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