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CVD graphene sensor of relative humidity measured in ambient and high vacuum conditions
Urbiš, Jakub ; Mach, Jindřich (referee) ; Bartošík, Miroslav (advisor)
This bachelor thesis deals with the utilization of graphene as a gas sensor and the effect of gate voltage on sensor sensitivity change. The first part summarizes knowledge about graphene as a sensor of hydrogen, oxygen and water. The experimental part was devoted to measuring and comparing resistance variation in dependence on ambient humidity for pure graphene, graphene-modified by Ar+ ions and Ga-coated graphene. Another experiment dealt with the rate at which the resistance of graphene was stabilized after an application of gate voltage. The last part deals with the environmental chamber.
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Selective hydrogenation/Oxidation of CVD graphene using AFM
Přikryl, Vojtěch ; Švarc, Vojtěch (referee) ; Bartošík, Miroslav (advisor)
Graphene is a perspective material for utilization in electronics due to its high charge carrier mobility. However, in order to be applicable in practice the bandgap opening is necessary. One way of achieving this is modification of graphene by hydrogenation or oxidation. This work concerns the possibility of using AFM for local hydrogenation/oxidation of graphene depending on the bias voltage between the tip and the sample. The presence of hydrogenation/oxidation was examined by Kelvin probe force microscopy and Raman spectroscopy. The possibility of oxidation was proved but hydrogenation was not proved.
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Analysis of one-dimensional structures using Kelvin Probe Force Microscopy
Kovařík, Martin ; Bartošík, Miroslav (referee) ; Kolíbal, Miroslav (advisor)
This bachelor's thesis deals with the use of Kelvin probe force microscopy (KPFM) for analysis of 1D nanostructures, namely germanium nanowires and tungsten disulfide (WS2) nanotubes. First part of this thesis is dedicated to the possibility of gold nanoparticles detection on germanium nanowires and also to the analysis of relevance of the KPFM method to measurements performed at various humidity. Second part deals with the measurement of surface potential changes on WS2 nanotubes induced by interaction with light. We have concluded, that relative surface potential changes can be measured at various humidity. This conclusion is also applied to study the interaction of WS2 nanotubes with monochromatic light. The experiment has revealed, that when exposed to light with defined wavelength, nanotubes coated with gold nanoparticles show opposite surface-potential changes as compared to pristine nanotubes, which indicates different physical processes under way.
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Selective hydrogenation of graphene prepared by chemical vapour deposition
Kovařík, Štěpán ; Nováček, Zdeněk (referee) ; Bartošík, Miroslav (advisor)
Controlled bandgap opening is one of the skills necessary for the application of graphene in electronics. The graphene hydrogenation is one of the possible ways to open the bandgap. In this work we deal with local hydrogenation of graphene prepared by chemical vapour deposition on a Si/SiO2 substrate. The hydrogenation was performed by atomic source of hydrogen and polymethyl methacrylate pattern was used for localization of hydrogenated structures on graphene. The pattern was prepared by electron beam lithography. The presence of structures formed by hydrogenated graphene was investigated by Raman spectroscopy, Kelvin probe force microscopy and PeakForce tunneling atomic force microscopy. All three methods have confirmed the local hydrogenation of graphene.
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UHV-EC transfer system for electrochemical surface science studies
Jakub, Zdeněk ; Vanýsek, Petr (referee) ; Bartošík, Miroslav (advisor)
This thesis deals with the combined ultra-high vacuum (UHV) and electrochemical (EC) studies of selected iron oxide surfaces, namely Fe3O4(001) and -Fe2O3(012). The state-of- the-art knowledge regarding these surfaces is briefly reviewed, and importance of understanding these materials in the electrochemical environment is discussed. The design of the transfer system between UHV and EC environment is presented; individual features of the system are thoroughly discussed and the system is used for testing the stability of the Fe3O4(001) (2×2)R45° surface reconstruction in ambient conditions. The experimental results presented in this thesis show that the Fe3O4(001) (2×2)R45° reconstruction, utilized as an adatom array for single atom catalysis studies, survives both exposure to air and to liquid water, if the exposure is achieved in well-controlled fashion. Further, this thesis presents the first-ever atomic scale scanning tunneling microscopy (STM) study of the -Fe2O3(012) surface, which is important for photoelectrochemical water splitting. STM images of two surface reconstructions of the -Fe2O3(012) surface known to date are presented. A bulk terminated model of the (1×1) reconstruction is confirmed and a novel surface structure model for the (2×1) reconstructed surface is proposed. Adsorption studies of H2O and O2 on the (2×1) reconstructed surface are documented by timelapse STM.
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Application of Graphene Membrane in Nanoelectronic Devices
Kormoš, Lukáš ; Drbohlavová, Jana (referee) ; Bartošík, Miroslav (advisor)
This diploma thesis is focused on the applications and fabrication of graphene membrane from graphene prepared by the chemical vapor deposition. Theoretical part deals with transport properties of the graphene and multiple scattering processes limiting the charge carrier mobility in this material. Included is short review of graphene membrane applications. Experimental part provides fabrication process for achieving suspended graphene device by utilizing electron beam lithography, focused ion beam, chemical etching and patterning of graphene. Graphene membrane is characterized by transport properties measurement and compared to non-suspended graphene.
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Application of KPM on Graphene/Si Surface Modified by FIB method
Konečný, Martin ; Rezek, Bohuslav (referee) ; Bartošík, Miroslav (advisor)
This diploma thesis is focused on the application of Kelvin probe microscopy on graphene fabricated by the chemical vapour deposition. The theoretical part of the thesis deals with basic principles of Kelvin force microscopy and focus ion beam. Further, basic properties of graphene and its possible fabrication methods are discussed. The experimental part is focused on the surface potential measurements on graphene membranes fabricated on the substrate modified by focus ion beam. Finally, atomic force microscope lithography was used for nanopatterning of graphene sheets.
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