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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Aplikace korelativní AFM/SEM mikroskopie / Application of correlative AFM/SEM microscopy

Hegrová, Veronika January 2019 (has links)
This thesis is dealing with application of Correlative Probe and Electron Microscopy. All measurements were carried out by atomic force microscope LiteScope which is designed especially to be combined with electron microscopes. Advantages of Correlative AFM/SEM Microscopy are demonstrated on selected samples from field of nanotechnology and material science. Application of the correlative imaging was proposed and then realized particularly in case of low-dimensional structures and thin films. Further, this thesis deals with the possibility of combining Correlative AFM/SEM Microscopy with other integrated techniques of an electron microscope such as Focused Ion Beam and Energy Dispersive X-rays Spectroscopy.
52

Optimalizace a měření transportních experimentů na grafenových polem řízených tranzistorech / Optimalization and measurement of transport experiments on graphene field effect transistors

Urbiš, Jakub January 2019 (has links)
This thesis deals with the automation of transport experiments on graphene using the graphical programming language LabVIEW. Specifically, the experiments with graphene relative humidity sensors are based on: a two-point graphene structure, a two-point structure of SiO$_2$ and a four-point graphene structure in the form of a Hall bar. In all of these experiments, relative humidity, input electrical parameters, SPM measurements, and macroscopic transport properties are measured simultaneously. The program DeviceManager developed in framework of this thesis simplifies the implementation of these experiments.
53

Příprava a charakterizace atomárně tenkých vrstev / Fabrication and characterization of atomically thin layers

Tesař, Jan January 2020 (has links)
Tato práce se zabývá oblastí dvourozměrných materiálů, jejich přípravou a analýzou. Pravděpodobně nejznámějším zástupcem dvourozměrných materiálů je grafen. Tento 2D allotrop uhlíku, někdy nazývaný „otec 2D materiálů“, v sobě spojuje neobyčejnou kombinaci elektrických, tepelných a mechanických vlastností. Grafen získal mnoho pozornosti a byl také připraven mnoha metodami. Jedna z těchto metod však stále vyniká nad ostatními kvalitou produkovaného grafenu. Mechanická exfoliace je ve srovnání s jinými technikami velmi jednoduchá, takto připravený grafen je však nejkvalitnější. Práce je také zaměřena na optimalizaci procesu tvorby heterostruktur složených z vrstev grafenu a hBN. Dle prezentovaného postupu bylo připraveno několik van der Waalsových heterostruktur, které byly analyzovány Ramanovskou spektroskopií, mikroskopií atomových sil a nízkoenergiovou elektronovou mikroskopií. Měření pohyblivosti nosičů náboje bylo provedeno v GFET uspořádání. Získané hodnoty pohyblivosti prokázaly vynikající transportní vlastnosti exfoliovaného grafenu v porovnání s grafenem připraveným jinými metodami. V práci popsaný proces přípravy je tedy vhodný pro výrobu kvalitních heterostruktur.
54

Příprava grafenu metodou CVD / The preparation of Grafen by method CVD

Procházka, Pavel January 2012 (has links)
This diploma thesis is mainly focused on the fabrication of graphene layers on the copper foil by the Chemical Vapor Deposition (CVD). For this purpose the high-temperature chamber for the production of the graphene was completed and fully automated. The production of the high area graphene on the copper foil was experimentally achieved. The Raman microscopy and X-ray photoelectron spectroscopy measurements proved that the produced graphene is mostly a monolayer. Graphene layer was transferred on non-conductive substrate.
55

Příprava a charakterizace elektrických vlastností CVD grafenových monokrystalů / The preparation and characterisation of electrical properties of graphene CVD monocrystals

Hulva, Jan January 2014 (has links)
Chemická depozice grafenu z plynné fáze (CVD) je metoda schopná produkovat grafenové monovrstvy velkých velkých rozměrů. Část experimentální práce v rámci této diplomové práce je zaměřena na depozici a analýzu grafenových monokrys- talů připravených metodou CVD na měděném substrátu. Pro analýu grafénových domén je použito technik optické mikroskopie, elektronové mikroskopie, mikroskopie atomárních sil a Ramanovy spektroskopie. Úkolem další části je studium defektů po- zorovaných na mědi po depozici grafenu pomocí energiově disperzní rentgenové spek- troskopie. Množství těchto defektů bylo odstraněno úpravou depozičního systému ačkoliv takto nebylo dosaženo eliminování všech typů defektů. Poslední část této práce se zabývá měření elektro-transportních vlastností grafenu. Výsledky této části zahrnují měření ve vakuu se zapojeným hradlovým napětím a měření při nízkých teplotách v magnetickém poli.
56

Příprava grafenových vrstev pokrytých Ga atomy a charakterizace jejich elektrických vlastností / The preparation of graphene layers modified by Ga atoms and characterisation of their electrical properties

Piastek, Jakub January 2015 (has links)
This master's thesis deals with the study of electric properties of graphene layers covered by Ga atoms in UHV conditions. The substrates were prepared by using laser litography and the graphene layer was prepared by using chemical vapor deposition (CVD). Dependence of Dirac point location on gallium atoms deposition time and influence of electrical properties of graphene on hydrogen atoms deposition time were studied. Experimental results and their evaluation are discussed.
57

Grafenový fotodetektor využívající plazmonických efektů / Graphene photodetector based on plasmonic effects

Horáček, Matěj January 2015 (has links)
Two rich and vibrant fields of investigation - graphene and plasmonics - strongly overlap in this work, giving rise to a novel hybrid photodetection device. The intrinsic photoresponse of graphene is significantly enhanced by placing the gold nanorods exhibiting unique anisotropic localized surface plasmon resonances on the graphene surface. The reported enhanced photoresponse of graphene is caused by the redistribution of localized surface plasmons in the nanoparticles into graphene. The exact underlying energy redistribution mechanism is thoroughly studied by a single particle scattering spectroscopy monitoring the particle plasmon linewidth as a function of the number of underlaying graphene layers. The obtained extraordinary plasmon broadening for nanoparticles placed on graphene suggests the contribution of a novel energy redistribution channel attributed to the injection of hot electrons from gold nanorods into graphene.
58

Vliv uhlíkových nanostruktur na chování lidských buněk a význam fetálního bovinního séra během buněčné adheze / The effect of carbon nanostructures on human cell behavior and the role of fetal bovine serum in cell adhesion

Verdánová, Martina January 2016 (has links)
Graphene (G) and nanocrystalline diamond (NCD) are carbon allotropes and promising nanomaterials with an excellent combination of their properties, such as high mechanical strength, electrical and thermal conductivity, possibility of functionalization and very high surface area to volume ratio. For these reasons, G and NCD are employed next to electronics in biomedical applications, including implant coating, drug and gene delivery and biosensing. For a fundamental characterization of cell behavior on G and NCD, we studied osteoblast adhesion and proliferation on differently treated G and NCD. Generally, both G and NCD exhibited better properties for osteoblast cultivation than control tissue culture polystyrene. Better cell adhesion but lower cell proliferation were observed on NCD compared to G. The most surprising finding was that hydrophobic G with nanowrinkled topography enhanced cell proliferation extensively, in comparison to hydrophilic and flat G and both NCDs (hydrophobic and hydrophilic) with slightly higher roughness. Promoted cell proliferation enables faster cell colonization of G and NCD substrates, meaning faster new tissue formation which is beneficial in biomedical applications. Furthermore, it was shown that osteoblast adhesion was promoted in the initial absence of fetal bovine...
59

Nové přístupy k uspořádávání plasmonických nanočástic do 2D a 3D hybridních aktivních systémů pro SERS grafenu a SERS, SERRS a SERS + GERS aromatických molekul / New pathways to plasmonic nanoparticle assembling into 2D and 3D hybrid active systems for SERS of graphene and SERS, SERRS and GERS + SERS of aromatic molecules

Gajdošová, Veronika January 2019 (has links)
In the first part of the Thesis, a new type of active system for SERS and SERRS of hydrophobic molecules, namely a 3-dimensional (3D) nanosponge aggregate with incorporated hydrophobic molecules has been developed, and tested by fullerene C60 and hydrophobic free- base tetraphenylporfine (H2TPP). The SERS and SERRS (surface enhanced /resonance/ Raman scattering) limits of detection (LODs) of C60 at four excitation wavelengths spanning the visible spectral region were found to be by one order of magnitude lower than in the reference system, which mimics the previously reported ways of utilization of Ag nanosponges as substrates for SERS and SERRS. The superiority of the newly developed sample is attributed to the efficient localization of the hydrophobic molecules into hot spots in 2D fractal aggregates of Ag nanoparticles (NPs). Diprotonation of H2TPP during the procedure using HCl as the preaggregation agent has been eliminated by employment of NaCl. On the other hand, investigation of the mechanism of H2TPP protonation during the former preparation procedure opened a possibility to employ Ag nanosponge aggregate as nanoreactor. In the second part of the Thesis, 2D assemblies of AgNPs were found to be better substrates for SERS of single layer graphene (SLG) than the 3D ones. In particular, the 2D...
60

Tvorba nanostruktur a nanosoučástek pro oblast nanoelektroniky a spintroniky / Fabrication of Nanostructures and Nanodevices for Nanoelectronics and Spintronics

Lišková, Zuzana January 2015 (has links)
The thesis deals with preparation of graphene nanostructures and their applications in the measurement of transport properties of graphene. The contacts for measurement of resistance are fabricated by electron beam lithography on graphene exfoliated flakes, CVD graphene layers and grains. Graphene is also shaped using the same method. Resistivity of the layer, concentration and mobility of charge carriers are determined by different approaches. Hysteresis appearing in dependence of resistivity on the gate voltage is discussed as well. A significant part of the work is dedicated to monitoring the response of graphene resistance to relative humidity changes and potential use of graphene as a sensor of relative humidity.

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