National Repository of Grey Literature 63 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
High mobility two-dimensional electron gas in CdTe quantum wells:High magnetic field studies
Kunc, Jan
KurHigh mobility two-dimensional electron gas in CdTe quantum wells: High magnetic field studies Experimental studies of two-dimensional electron gases confined in CdTe and CdMnTe quantum wells are presented. The data analysis is supported by numerical calcula- tions of the band structure of confined states, using the local density and envelope func- tion approximations. Four by four, k.p calculations have been performed to justify the parabolic approximation of valence bands. Samples were characterized by Raman scatter- ing spectroscopy and far infrared cyclotron resonance absorption measurements. Low-field magneto-transport shows the dominant contribution of the semi-classical Drude conduc- tivity and three orders of magnitude weaker contributions of weak localization, electron- electron interaction and Shubnikov-de Haas oscillations. The contribution of electron- electron interactions is explained within a semi-classical model of circling electrons. The shape of Landau levels, broadening, transport and quantum lifetimes and dominant long- range scattering mechanism have been determined. High-field magneto-transport displays fractional quantum Hall states at Landau levels N = 0 and N = 1. The ground states 5/3 and 4/3 have been determined to be fully spin polarized, in agreement with the approach of composite...
Interaction of short-wavelength laser pulses with matter on various time scales
Vozda, Vojtěch ; Kunc, Jan (advisor) ; Caha, Ondřej (referee) ; Timneanu, Nicusor (referee)
An advent of powerful sources producing intense and ultrashort laser pulses containing high-energy photons opened up a wide range of possibilities to conduct experiments formerly achievable only through theoretical calculations and models. This thesis provides a complex overview of processes which occur right after arrival of the first photons, through lattice heating, up to resolidification and formation of irreversible changes. Irradiated spots and craters formed in various materials are examined employing a wide range of microscopic and spectroscopic methods which provide a deep insight into laser-induced modifications such as detachment of a graphene layer from SiC substrate or thermally-induced diffusion of tellurium inclusions through CdTe lattice. An increased emphasis is placed on beam characterization utilizing ablation and desorption imprints in suitable solids. A proper knowledge of the beam fluence profile may serve for evaluation of diverse damage thresholds as well as for modelling of the pulse propagation or consequent retrieval of otherwise unmeasurable opacity of warm dense aluminium plasma heated to temperatures exceeding tens of thousands of Kelvins. Moreover, the method of desorption imprints is extended to accurate characterization of pulses delivered at MHz repetition rate....
Growth of graphene by thermal decomposition of silicon carbide for applications in biophysics
Hodoš, Matúš ; Kunc, Jan (advisor) ; Čechal, Jan (referee)
This bachelor thesis is focused on growth and characterization of graphene from SiC powder at different conditions. In the introduction graphene properties are briefly described. Afterwards three methods of graphene growth are discussed, with particular emphasis on thermal decomposition of SiC. Further, the characterization methods which were used by us are explained. In experimental part, three sets of graphene samples prepared by thermal decomposition of SiC will be described, each will differ in one of the factors: temperature, time and ambient atmosphere. Growth samples will be subsequently used in an experiment on yeast. The effect of graphene prepared at different conditions on membrane potential will be determined for possible application in biophysics.
Fabrication and characterization of atomically thin layers
Tesař, Jan ; Kunc, Jan (referee) ; Procházka, Pavel (advisor)
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.
Design of demonstration panel KNX
Kalfus, Petr ; Kunc, Josef (referee) ; Bátora, Branislav (advisor)
This bachelor's thesis deals with the design of a demonstration panel KNX, which has to demonstrate the control of lights, blinds and appliances of the house with the help of devices from various manufacturers First, there is a search and acquaintance with the KNX system, it´s topological arrangement, devices and used communication media. Furthermore, an introduction is made to the individual devices used on the demonstration panel, with the functions they enable and with their application programs for the ETS environment. Based on the possibilities of the device, the design of the panel function is done. These functions have been programmed in the ETS 5. Next, a drawing of the electrical connection of the panel is made and documentation is made for it. Finally, an overall evaluation is made.
Role of hydrogen during growth of epitaxial graphene on SiC
Sýkora, Petr ; Kunc, Jan (advisor) ; Čechal, Jan (referee)
This work is focused on preparation of graphene by epitaxial growth on silicon face of silicon carbide. In the introduction, the interesting properties of graphene are briefly described, and its possible applications are mentioned. Subsequently, the methods of preparation are discussed with an emphasis on epitaxial growth and the role of hydrogen on the process itself. Further, the possible ways of measuring graphene samples are explained and three of them are analyzed in more detail - Raman spectroscopy, atomic force microscopy, and Hall effect measurement. The experiment itself is focused on the effect of argon-hydrogen atmosphere on the growth of graphene. 1
Interaction of low-energy electrons with graphene field effect transistors
Vysocký, Filip ; Kunc, Jan (referee) ; Čechal, Jan (advisor)
This diploma thesis is focused on fabrication of graphene field-effect transistors, characterisation of their transport properties and investigation of low-energy electron beam influence on the devices' properties under UHV conditions. The theoretical part of this work describes graphene fabrication methods, options of graphene transfer onto the substrates for graphene field-effect transistor manufacture. Furthermore, model of graphene doping via electrostatic interaction or photon, resp. electron beam exposition is explained. The experimental part of this work consist of manufacture of the graphene field-effect transistor in order to examine the change of its transport properties induced by doping of the graphene via low-energy electron beam exposition.
Factors of revitalization of brownfields in the Czech Republic
Osman, Robert ; Frantál, Bohumil ; Kunc, Josef ; Klusáček, Petr ; Martinát, Stanislav
The paper deals with reuse of brownfields in the Czech Republic. Based on the analysis of information about re-use of residual spaces are shown major changes in the current management space. The paper is based on a comparison of two data files - specifically, the existing brownfields database managed by the CzechInvest and own database of brownfields that have already been revitalized. The paper is divided into three parts, the first part of the paper analyzes the structure of a revitalized brownfields, in the second part of the paper, the structure of this file is compared with the structure of existing brownfields and the third part analyzes the factors revitalization of brownfields. The paper aims to answer the question what functions take the brownfields after revitalization and what factors determine their reuse.
Perception of wind power plants construction on the local level: Case studies in East Bohemia
Janová, M. ; Kunc, J. ; Frantál, Bohumil
The paper aims to evaluate selected findings of a research regarding the attitudes of the inhabitants of East Bohemian municipalities (Anenska Studanka and Vitezna) towards the construction of wind power plants and the perception thereof. A survey was carried out among the inhabitants of the two municipalities, as well as nearby municipalities and guided interviews were conducted with their mayors. The two selected sites differ in population numbers, time of power plant construction, number and size of the turbines and form of financial settlement. In the case of Vitezna, the power plant in question was community-funded, meaning that a portion of the shares was offered to the inhabitants (a unique case in the Czech Republic). The results indicated that, over time, the attitudes and opinions of the respondents from all the municipalities concerned have shifted towards a more positive perception of wind power plants. They have, however, also become more polarized. Citizens' movements against further construction have been created, even though it is currently not possible in the Czech Republic, especially given that the government has cancelled funding for the support of clean power. Respondents who were found to have the fewest issues with the wind power plants were younger than 30 years, graduates of secondary education and resided at a greater distance from the stations without having direct visual contact with them from their home.
Graphene doping by low-energy electrons
Stará, Veronika ; Kunc, Jan (referee) ; Čechal, Jan (advisor)
Tato diplomová práce se zabývá dotováním grafenu nízkoenergiovými elektrony. Na křemíkový substrát pokrytý vrstvou SiO2 jsou pomocí litograficky vyrobené masky nadeponované kovové kontakty z titanu a zlata. Grafen vyrobený pomocí metody depozice z plynné fáze je přenesen na substrát a slouží jako vodivé spojení kovových elektrod, které vytvářejí kolektor a emitor. Na křemík je ze spodu přivedeno napětí, které tak vytváří spodní hradlo. Takto vytvořený grafenový tranzistor je ozařován nízkoenergiovými elektrony, které mění dotování grafenu. Z polohy maxima v závislosti odporu grafenu na hradlovém napětí lze vyčíst typ dotování. Toto maximum udává napětí, při kterém Fermiho meze grafenu prochází Diracovým bodem v pásové struktuře grafenu. Velikost hradlového napětí, primární energie elektronového svazku a proud svazku jsou tři parametry, které mají velký vliv na změny dotování. Při ozařování transistoru dochází ke změně typu dotování právě tehdy, když odpor grafenu v závislosti na hradlovém napětí dosáhne maxima. Vývoj této změny je zkoumán pro různé energie a proudy primárního svazku v závislosti na hradlovém napětí i v čase. Typ dotování je také prozkoumán při zastavení ozařování v různých fázích smyčky hradlového napětí. Dopování grafenu nízkoenergiovými elektrony je popsáno v teoretickém modelu.

National Repository of Grey Literature : 63 records found   1 - 10nextend  jump to record:
See also: similar author names
1 Kunc, Jakub
1 Kunc, Jakub Bc.
4 Kunc, Jan
3 Kunc, Jaroslav
1 Kunc, Jindřich
1 Kunc, Jiří
4 Kunc, Josef
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