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Preparation of graphene membranes for Ga deposition
Severa, Jiří ; Bartošík, Miroslav (referee) ; Mach, Jindřich (advisor)
This bachelor’s thesis deals with the production of graphene membranes, which would be suitable for the deposition of gallium atoms. In the first part is characterized graphene. The second part is focused on preparation and improvement the production of graphene layers via atomically flat Cu foils. In the third part are described graphene membranes, techniques of their production and specific applications of graphene membranes. The fourth part introduced interface between gallium and graphene layers. The fifth part is the practical part. Graphene was grown on different Cu foils which resulted in higher quality graphene grown on smooth foils. Subsequently, the production of graphene membranes and deposition of gallium atoms were done.
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Depositon Ga and GaN nanostructures on graphen substrate
Hammerová, Veronika ; Váňa, Rostislav (referee) ; Mach, Jindřich (advisor)
This diploma thesis is focused on deposition Ga and GaN structures on graphene fabricated by method of mechanical exfoliation. For mechanical exfoliation was used new method with using DGL Gel-Film with kinetically controlled adhesion. Ga is deposited by Molecular beam epitaxy with using eusion cell in UHV conditions. GaN was obtained by post-nitridation of Ga islands. These structures were investigated with optical microscope, SEM, Raman spectroscopy and photoluminiscence.
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Analysis of locally modified surfaces for selective growth of cobalt
Krajňák, Tomáš ; Bábor, Petr (referee) ; Čechal, Jan (advisor)
In this thesis the chemical composition of silicon substrates locally modified by focused gallium ion beam by X-ray photoelectron spectroscopy is determined. In order to determine the influence of focused ion beam, the sample comprising sputtered square areas with nominal depths in range of 1 to 10 nm was prepared. Next, the sample was heated to elevated temperatures (500 - 700 °C) to reveal changes in the sputtered areas induced by annealing. In this work by X-ray photoelectron spectrometer Kratos Supra and electron microscope Tescan LYRA3 with focused ion beam were used. From the measured spectra of the Si 2p and Ga 2p3/2 peaks measured as a function of nominal sputtering depth and annealing temperature the following main observations were obtained. First, there is the additional peak component in the Si 2p peak, which can be assigned to the amorphous silicon. The second important finding is that gallium can be removed from near surface volume by annealing at temperatures beyond 700 °C.
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Application onf the Focused Ion on Electron Beam in Nanotechnologies
Šamořil, Tomáš ; Mikulík, Petr (referee) ; Jiruše, Jaroslav (referee) ; Šikola, Tomáš (advisor)
Nowadays, the systems that allow simultaneous employment of both focused electron and ion beams are very important tools in the field of micro- and nanotechnology. In addition to imaging and analysis, they can be used for lithography, which is applied for preparation of structures with required shapes and dimensions at the micrometer and nanometer scale. The first part of the thesis deals with one lithographic method – focused electron or ion beam induced deposition, for which a suitable adjustment of exposition parameters is searched and quality of deposited metal structures in terms of shape and elemental composition studied. Subsequently, attention is paid also to other types of lithographic methods (electron or ion beam lithography), which are applied in preparation of etching masks for the subsequent selective wet etching of silicon single crystals. In addition to optimization of mentioned techniques, the application of etched silicon surfaces for, e.g., selective growth of metal structures has been studied. The last part of the thesis is focused on functional properties of selected 2D or 3D structures.
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The deposition of Ga and GaN nanostructures on silicon and graphene substrate
Mareš, Petr ; Hospodková,, Alice (referee) ; Mach, Jindřich (advisor)
Presented thesis is focused on the study of properties of Ga and GaN nanostructures on graphene. In the theoretical part of the thesis a problematics of graphene and GaN fabrication is discussed with a focus on the relation of Ga and GaN to graphene. The experimental part of the thesis deals with the depositions of Ga on transferred CVD-graphene on SiO2. The samples are analyzed by various methods (XPS, AFM, SEM, Raman spectroscopy, EDX). The properties of Ga on graphene are discussed with a focus on the surface enhanced Raman scattering effect. Furthermore, a deposition of Ga on exfoliated graphene and on graphene on a copper foil is described. GaN is fabricated by nitridation of the Ga structures on graphene. This process is illustrated by the XPS measurements of a distinct Ga peak and the graphene valence band during the process of nitridation.
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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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Selective growth of GaN on SiN
Hulva, Jan ; Kolíbal, Miroslav (referee) ; Mach, Jindřich (advisor)
This bachelor's thesis deals with the selective growth of gallium and gallium nitride on silicon nitride (SiN) substrates. Thin silicon nitride layers are deposited on silicon substrates. Oxide structures are prepared by the local anodic oxidation method (LAO) on SiN substrates. These surfaces can be editionally modified by etching in hydrofluoric acid. Modified substrates are used for the deposition of gallium or gallium nitride under ultra-high vacuum conditions. Consequently, ordering of deposited material was studied in areas modified by LAO. Chemical state of layers is studied by X-ray photoelectron spectroscopy. Morphology of surfaces is measured by the atomic force microscope (AFM).
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