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Deposition of Ga and GaN ultrathin layers on graphene substrate
Dvořák, Martin ; Nebojsa, Alois (referee) ; Mach, Jindřich (advisor)
This diploma thesis deals with preparation of graphene samples for depositions of ultrathin layers of gallium and gallium nitride. Graphene substrates were prepared by chemical vapour deposition in home-build high temperature reactor. After graphene transfer to silicon wafers, a series of chemical and thermal treatments were performed. Obtained samples were suitable for the study of growth of ultrathin layers of Ga and GaN. The growth of Ga and GaN was realized in ultra high vacuum conditions. Molecular beam epitaxy technique was used for gallium depositions together with ion source for nitridation. Obtained ultrathin layers were studied with X-ray photoelectron spectroscopy, atomic force microscopy and with scanning electron microscopy.
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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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Modeling of Surface-Plasmon Propagation in Graphene
Hrtoň, Martin ; Munzar,, Dominik (referee) ; Kalousek, Radek (advisor)
The diploma thesis provides an introduction to electronic and optical properties of graphene, emphasizing thier tunability through the ambipolar field effect. Furthermore, an experiment, which would demonstrate the possible utilization of graphene in active plasmonics, is presented. The author focuses on light scattering simulations involving hybrid plasmonic structures made of noble metals and graphene. The scattering properties of those structures and their dependence on the density of free charge carriers in graphene are investigated. The author concludes that the proposed tuning of the response of a single metallic antenna through the electrostatic doping of graphene proves to be inefficient, and a more elaborate configuration will be required to enhance the effect and achieve the desired control.
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Nanotechnology utilization in nuclear industry and research
Skalička, Jiří ; Štefánik, Milan (referee) ; Katovský, Karel (advisor)
This thesis introduces reader to current knowledge of nanomaterials and their usage. It summarises production methods and usage of different materials in nuclear power plants, nuclear research and nuclear medicine. Theoretical part of this thesis is dedicated to possible usage of carbon nanotubes for neutron beam collimation and guides. In experimental part different materials were tested in measuring box connected to horizontal radial channel of VR-1 nuclear reactor and their influence on neutron flux was measured. Tested samples were non-oriented carbon nanotubes, carbon nanofibers, alumina nanowires, oriented carbon nanotubes with several angles of rotation and these samples were compared with results of graphite.
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Photocatalytic water splitting by oxide semiconductors modified with graphen/graphenoxide
Marek, Jiří ; Čáslavský, Josef (referee) ; Cihlář, Jaroslav (advisor)
This master thesis deals with the topic of alternative production of hydrogen as the energy carrier of the future. The primary focus is on the production of hydrogen based on photocatalytical water splitting in the presence of semiconductor materials (especially modified and unmodified TiO2). The aim of the thesis is a synthesis of nanostructured oxide, graphene/graphene oxide particles and its composites, and a study of its structures and photocatalytical properties regarding photolysis of water. Products of the syntheses are described from the point of view of phase composition, surface area and photocatalytical activity. The main output of the thesis is a discussion of the influence of alkaline complex forming reagents on the hydrothermal low-temperature synthesis of biphasic TiO2, and a study of the influence of graphene/graphene oxide modification on photocatalytical activity of biphasic TiO2.
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Analysis of the transport properties of graphene nanostructures
Novák, Martin ; Bartošík, Miroslav (referee) ; Lišková, Zuzana (advisor)
Graphene transport properties are analysed in this thesis. They are strongly dependent on doping with charge carriers. The number of charge carriers can be influenced by electric field, substrate or surface adsorbates. The graphene field-effect transistor (FET) has been prepared. Graphene made by chemical vapor deposition (CVD) has been con tacted through gold structures made by electron beam lithography (EBL). Dependences on electrode configuration, gate voltage and used substrate are observed.
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Preparation of graphene samples for experiments under UHV conditions
Mareček, David ; Mach, Jindřich (referee) ; Čechal, Jan (advisor)
This bachelor thesis deals with electrical conductivity of a graphene sample and preparation of a graphene field-effect transistor. In the theoretical part of the thesis, we describe electronic properties of graphene, preparation of graphene by CVD and its transfer to SiO_2. Experimental part of this thesis is focused on the preparation of a graphene field-effect transistor with long distance between Source and Drain electrodes. Thesis deals with a design of a chip expander for contact of graphene in UHV conditions. The last part describes measurement of dependency of graphene layer conductivity on the gate voltage with emphasis on the position of Dirac point during adjustments of the sample in UHV conditions.
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Schottky solar cells with interface graphene/Si modified by gallium
Hlavička, Ivo ; Lišková, Zuzana (referee) ; Mach, Jindřich (advisor)
Main focus of this bachelor thesis is on fabrication, characterization and modification of graphene-on-silicon Schottky solar cells. By transfering CVD graphene onto silicon wafer with electrodes, a basic Schottky junction was created. The junction was then modified by annealing in UHV chamber as well as by gallium deposition. Information about power conversion efficiency of such Schottky solar cells was then obtained by IV measurement. Schottky junction itself was analyzed using X-EBIC method.
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