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Preparation and characterization of nanostructures for catalysis and gas detection
Haviar, Stanislav ; Matolínová, Iva (advisor) ; Zahoran, Miroslav (referee) ; Plšek, Jan (referee)
First part of this thesis is focused on magnetron sputtering deposited layers of cerium oxide using carbonaceous substrates. Micrographs from scanning and transmission electron microscopes reveal that cerium oxide layers exhibit remarkable roughness and nano-porosity. In this work there are presented optimized key preparation parameters for growth of highly nano-porous layers of cerium oxide on amorphous graphite as well as on graphite foil. The effect of residual atmosphere during the magnetron sputtering deposition is discussed. Results of deposition using oxygen/argon mixture as working gas are presented. A simple growth model is formulated and discussed. Second part deals with utilization of cerium and tungsten oxides as conductometric gas sensors. A testing station was constructed for gathering sensorial properties of such devices. The construction and abilities of the measuring system designed by the author are noted. Preliminary results of measurements of response to hydrogen are presented. Cerium oxide layers suprisingly exhibit measurable response to hydrogen gas. Tungsten oxide nanowires grown on mica substrate were formed into gas sensor via electron beam lithography and show high sensitivity. Powered by TCPDF (www.tcpdf.org)
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Preparation and characterization of nanostructures for catalysis and gas detection
Haviar, Stanislav ; Matolínová, Iva (advisor) ; Zahoran, Miroslav (referee) ; Plšek, Jan (referee)
First part of this thesis is focused on magnetron sputtering deposited layers of cerium oxide using carbonaceous substrates. Micrographs from scanning and transmission electron microscopes reveal that cerium oxide layers exhibit remarkable roughness and nano-porosity. In this work there are presented optimized key preparation parameters for growth of highly nano-porous layers of cerium oxide on amorphous graphite as well as on graphite foil. The effect of residual atmosphere during the magnetron sputtering deposition is discussed. Results of deposition using oxygen/argon mixture as working gas are presented. A simple growth model is formulated and discussed. Second part deals with utilization of cerium and tungsten oxides as conductometric gas sensors. A testing station was constructed for gathering sensorial properties of such devices. The construction and abilities of the measuring system designed by the author are noted. Preliminary results of measurements of response to hydrogen are presented. Cerium oxide layers suprisingly exhibit measurable response to hydrogen gas. Tungsten oxide nanowires grown on mica substrate were formed into gas sensor via electron beam lithography and show high sensitivity. Powered by TCPDF (www.tcpdf.org)
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Investigation of Pt-SnOx gas sensors
Kúš, Peter ; Matolín, Vladimír (advisor) ; Zahoran, Miroslav (referee)
1 is a suitable material for thin-film gas sensors. Higher sensitivity could be achieved by platinum dopping of the layer. This work focuses on the optimalization of and thin film preparation by radio-frequency magnetron sputtering method. Subsequent analysis by means of XPS, AFM, SEM and XRD was carried out to determine physicochemical attributes of resulting layers. It appears that after the deposition, platinum within the layer is present in the metalic , as well as in the mixed chemical state. After the annealing process mixed state dominates over metalic state and after additional annealing platinum is present solely in oxidized form. Sensory response of layers for presence of hydrogen were examined on two different chip platforms (glass with chromium contacts and sapphire with platinum contacts). Contrary to expectations, the platinum dopped layers performed worse in comparison to the pure tin dioxide layers. This could be explained by the fact, that after annealing platinum within the layer was present mainly in the non-metalic form. Both and layers were more sensitive on sapphire platform, which could be associated with the crystal structure formed on its surface or with presence of metalic contacts.
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