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Correlative probe electron microscopy analysis of plasma-treated gallium-doped zinc oxide nanorods
Rutherford, D. ; Remeš, Zdeněk ; Mičová, J. ; Ukraintsev, E. ; Rezek, B.
Correlative Probe Electron Microscopy (CPEM) was used to investigate the topographical and electronic emission properties of gallium-doped zinc oxide nanorods (ZnO:Ga) after low pressure hydrogen or oxygen plasma treatment. Simultaneous secondary electron (SE) and back-scattered electron (BSE) emission information from the same nanorods enabled true correlation with the topographical information obtained by atomic force microscopy (AFM). All nanorods were analyzed in-situ on the same substrate using the same experimental parameters which allowed for accurate comparison. ZnO:Ga nanorods displayed the largest SE emission intensity as well as the greatest BSE emission intensity. Hydrogen plasma treatment reduced both SE and BSE emission intensity, whereas oxygen plasma treatment only reduced SE emission. These effects may help elucidate various optical as well as biological interactions of ZnO:Ga nanorods.
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Effect of spin coating on electrical properties of MXene films deposited from non-aqueous solvents
Gutsul, O. ; Szabó, Ondrej ; Pfeifer, R. ; Sasitharan, K. ; Jackivová, Rajisa ; Slobodyan, V. ; Kromka, Alexander ; Rezek, B.
We investigated the effect of spin coating parameters on the electrical properties of Ti3C2 MXene thin films deposited from non-aqueous suspensions in N,N-dimethyl formamide (DMF) and N-methyl-2-pyrrolidone (NMP) on gold interdigitated electrodes (IDE). The electrical properties of DMF-MXenes and NMP-MXenes films are characterized by impedance spectroscopy (4 Hz - 8 MHz at 1 V) using gold IDE with 25 µm gap. The electrical conductivity of MXene films decreases with increasing spin coating speed from 300 to 900 rpm. The series resistance (Rs) and double layer capacitance remain similar (Cdl). In all cases, MXenes deposited from DMF have five orders of magnitude higher electrical conductivity (lower Rct) than MXene films deposited from NMP. It is correlated with the thin film morphology obtained by scanning electron microscopy (SEM). These findings can be useful for possible application of MXenes as charge transport layers in hybrid photovoltaic devices.
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Application of metallic materials for selective growth
Němeček, Tomáš ; Rezek, Bohuslav (referee) ; Čechal, Jan (advisor)
The Si(100) surface and Ga surface phases up to 1 ML on their oxidation have been studied by XPS and LEED. The selective growth of Ga on the SiO2/Si structures fabricated by EBL has been analyzed using SEM and AFM methods. It was proved that Ga clusters grow in structures beside the oxide. The structure of alumina on Ni3Al(111) and NiAl(110) substrates was fully determined by combining the results of STM measurements and DFT simulations. It was determined the alumina/NiAl(110) does not form a suitable template for ordered Fe and Co clusters growth. However, the next research confirmed the alumina/Ni3Al(111) forms template appropriate to clusters growth purpose.
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Nanophotonics
Dvořák, Petr ; Rezek, Bohuslav (referee) ; PhD, Jakub Dostálek, (referee) ; Šikola, Tomáš (advisor)
This thesis deals with an experimental research of the surface plasmon polaritons (SPPs) using Scanning Near-field Optical Microscopy (SNOM). The first chapter provides theoretical background and a description of most of the physical phenomena and relevant dependencies studied in this work. These dependencies include the dependence of the resulting SPP image on homogeneity, polarization, wavelength and phase of the illumination, on the geometry of the interference structures and on the tilt of the sample with respect to the illumination. Further, this work presents a new experimental method which, using the numerical simulations or SNOM measurements, allows to estimate the sensitivity of SNOM probe to detect the individual electric intensity components of the near-field. At the end of the thesis, the work presents a new microscopic technique which enables a 3D quantitative imaging of phase distribution above the plasmonic metasurfaces.
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The preparation and characterisation of electrical properties of graphene CVD monocrystals
Hulva, Jan ; Rezek, Bohuslav (referee) ; Mach, Jindřich (advisor)
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.
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Application of Scanning Probe Microscopy for the Study of Ultrathin Films and Nanostructures
Neuman, Jan ; Rezek, Bohuslav (referee) ; Mašláň, Miroslav (referee) ; Šikola, Tomáš (advisor)
Dizertační práce je obecně zaměřena na problematiku mikroskopie atomárních sil (AFM), a to jak vývoje částí těchto mikroskopů, tak i jejich obecnému využití v oblasti výzkumu povrchů, ultratenkých vrstev a nanostruktur. Na Ústavu fyzikálního inženýrství jsou vyvíjena zařízení umožňující aplikovat uvedenou mikroskopickou metodu. V těchto mikroskopech jsou využívány piezoelektrické motory pro zajištění pohybu vzorku a ladicích zrcátek v optickém detekčním systému. Práce se v části věnované vývoji AFM zabývá studiem parametrů řídicích pulzů za účelem optimalizace funkce těchto komponent. Měřením vlivu tvaru pulzů a opakovací frekvence byl jejich pohyb optimalizován z hlediska stability a rychlosti posuvu. V části věnované výzkumu povrchů byly experimentálně zkoumány morfologické změny ultratenkých vrstev zlata na povrchu oxidu křemičitého za zvýšených teplot. Bylo zjištěno, že vhodná povrchová modifikace způsobuje vznik preferenčních trhlin ve vrstvě zlata. Řízeným rozdělením polykrystalické vrstvy na oddělené oblasti je možné významně ovlivnit proces tvorby ostrůvků zlata vznikajících při žíhání. S využitím metod elektronové litografie je možná příprava uspořádaných polí zlatých ostrůvků o velikostech 50 – 400 nm. Dále bylo ukázáno, že zvýšením teploty žíhání na 1000 °C dochází k postupnému zanořování ostrůvků zlata do povrchu. Tento jev je pravděpodobně způsoben přesunem oxidu křemičitého z oblasti pod zlatým ostrůvkem do těsného okolí vzniklého kráteru, kde tvoří tzv. límec. V těchto studiích vedle metody AFM byla s výhodou používána rovněž elektronová mikroskopie (SEM).
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Fabrication of Graphene and Study of its Physical Properties
Procházka, Pavel ; Rezek, Bohuslav (referee) ; Kalbáč,, Martin (referee) ; Dub, Petr (advisor)
This doctoral thesis is focused on the preparation of graphene layers by Chemical Vapor Deposition (CVD) and their utilization for fabrication and characterization of field effect transistors. The theoretical part of the thesis deals with different methods of graphene production and measurement of its transport properties. In the first part of the experimental section the growth of polycrystalline graphene and individual graphene crystals with sizes up to 300 m is investigated. Further, graphene layer was also grown on an atomically flat copper foils, which were fabricated in order to achieve the growth of graphene of higher quality. Subsequently, the transport properties of field effect transistors produced from the grown layers were measured. The last two chapters deal with a doping of graphene layer by gallium atoms and X-ray radiation. Whereas the deposition of gallium atoms on the graphene surface causes chemical doping of graphene layer by charge transfer, X-ray irradiation of graphene field effect transistors induces the ionization of positively charged defects in dielectrics, which electrostatically dope a graphene layer.
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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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Ordered and disordered arrays of colloidal nanoparticles for biomolecule detection
Ligmajer, Filip ; Rezek, Bohuslav (referee) ; Kolíbal, Miroslav (advisor)
This thesis deals with guided self-assembly of gold nanoparticles from their colloidal solutions onto silicon substrates and possible employment of nanoparticles for detection of biomolecules. It was found that by adjustment of solution pH and surface chemistry modification by means of electron beam irradiation it is possible to facilitate nanoparticle deposition to patterns with almost single particle precision. Spectroscopic ellipsometry was then employed in analysis of self-assembled layers of nanoparticles and its combination with a theory of effective medium approximation has proven the ability to assess nanoparticle dimensions and volume fractions. By experiments with thiolated oligonucleotides it has been shown that using ellipsometry one can detect even with very subtle changes in nanoparticle environment caused by biomolecules, thus promising its possible use in the field of biodetection.
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Semiconductor nanowire growth utilizing alloyed catalyst
Musálek, Tomáš ; Rezek, Bohuslav (referee) ; Kolíbal, Miroslav (advisor)
This master's thesis deals with growth of germanium nanowires using different catalyst particles. The emphasis is mainly layed on fabrication of specific alloyed catalyst consisting of (AgGa). In the first part of the thesis are mentioned two most common concepts of nanowire growth and the importance of phase diagrams for their interpretation. Method for production of alloyed catalyst is demonstrated and experiments focused on the growth of germanium nanowires using this catalyst were performed. Moreover, method for modification of germanium surface via anisotropic etching is demonstrated as well. Such etched structures are suitable for nanowire growth with the help of different kinds of catalyst particles or for the growth of nanowires made of various materials.
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