|
|
Characterization of structures fabricated by selective wet etching of silicon
Metelka, Ondřej ; Mikulík, Petr (referee) ; Šamořil, Tomáš (advisor)
The task of master’s thesis was to perform optimalization process for preparing metal etching mask by electron beam litography and subsequent selective wet ething of silicon with crystalographic orientation (100). Further characterization of etched surface and fabricated structures was performed. In particular, attention was given to the morphology demonstrated by scanning electron microscopy and study changes of the optical properties of gold plasmonic antennas due to their undercut.
|
|
|
Design and adaptation of electron microscope accessories for in-situ experiments
Drozd, Michal ; Mikulík, Petr (referee) ; Kolíbal, Miroslav (advisor)
Účinnost katalyzátoru v kombinaci s optimalizovanou reakcí a minimalizováním jeho množsví jsou klíčovými faktory při snižování investičních a provozních nákladů v rámci chemických procesů. Díky pokročilým experimentálním technikám mohou být katalyzátory dále zlepšovány. Jednou z těchto technik je in-situ elektronová mikroskopie. Tato práce se zabývá vývojem zařízení pro automatický ohřev vzorku, automatickým vpouštěním reaktantů a měřením parciálních tlaků v komoře mikroskopu. Dále je pomocí provedených experimentů srovnán přístup pomocí environmentálního rastrovacího mikroskopu, kde se využívá laserový ohřev vzorku s přístupem, který využívá skenovací elektronový mikroskop připojený k ultra vakuové komoře, kde se vzorek zahřívá pomocí průchodu elektrického proudu.
|
|
|
Šikmost v teorii optimalizace a eficience portfolia
Mikulík, Petra ; Branda, Martin (advisor) ; Lachout, Petr (referee)
In this thesis we study models, which search for an optimal portfolio from a set of stocks. On the contrary to the classical approach focusing only on expected return and variance, we examine models where an additional crite- rion of skewness is included. Furthermore we formulate a model for measuring performance of a portfolio defined as the distance from the Pareto efficient frontier. In numerical experiments we apply the models on historical prices and stock data from the electronic stock market NASDAQ. We analyze the stock data from companies listed in the index NASDAQ-100. We conclude by comparing of optimal portfolios created using different models among each other, with trivial single-stock portfolios and the with NASDAQ-100 index itself.
|
|
|
Study of indium doped shape-memory alloy Ni2MnGa
Cejpek, Petr ; Dopita, Milan (advisor) ; Dobročka, Edmund (referee) ; Mikulík, Petr (referee)
Title: Study of indium doped shape-memory alloy Ni2MnGa Author: Petr Cejpek Department: Department of Condensed Matter Physics Supervisor: RNDr. Milan Dopita, PhD., Department of Condensed Matter Physics Abstract: The alloys related to Ni-Mn-Ga system exhibit effects connected to the magnetic shape-memory and martensitic transformation and therefore attract attention of researchers for their application potential. Properties and especially transformation temperatures are strongly dependent on composition, doping and also on external conditions as a magnetic field or pressure. The main aim of the work was to prepare own single crystals of Ni2MnGa1−xInx and to study their properties with respect to the temperature and applied fields in dependence on a various indium doping. The transformation temperatures obtained from the measurement of electrical resistivity and magnetisation re- vealed the systematic decrease of martensitic transformation temperature TM , pre-martensitic transformation temperature TP and Curie temperature TC. The martensitic transformation should vanish at indium concentration of x ≈ 0.10. The decrease with indium content is much faster than in the study published previously on the polycrystalline samples (vanishing at x ≈ 0.20). This dis- crepancy is probably caused by the residual stress...
|
|
|
Deposition of Ga nanostructures on graphene membranes
Severa, Jiří ; Mikulík, Petr (referee) ; Mach, Jindřich (advisor)
This diploma thesis deals with the preparation of the graphene membranes for depo-sition of gallium atoms by the molecular beam epitaxy. In the first part properties ofgraphene and methods of its production are described. Second part focuses on the gra-phene membranes, their specific properties, applications and methods of production. Thirdpart describes growth theory of the thin films. Practical part is focused on preparationof graphene membranes, which consists of covering the holes in the silicon substrate bygraphene layer. For that mechanical exfoliated and chemical vapor deposited graphenewere used. Subsequently, gallium atoms were deposited on these membranes by molecularbeam epitaxy and in situ observed by scanning electron microscopy.
|
|
|
Combined Electron Beam Lithography
Krátký, Stanislav ; Mikulík, Petr (referee) ; Škereň,, Marek (referee) ; Kolařík, Vladimír (advisor)
This thesis deals with grayscale e-beam lithography and diffractive optical elements fabrication. Three topics are addressed. The first topic is combined grayscale e-beam lithography. The goal of this task is combining exposures performed by two systems with various beam energies. This combined technique leads to a better usage of both systems because various structures can be more easily prepared by one electron beam energy than by the other. The next topic is the optimization of shape borders of exposing structures that are defined by image input. The influence of such optimization on exposure data preparation is evaluated, as well as the exposure time and the change of optical properties of testing structures. The possibility of deep multilevel diffractive optical element fabrication in plexiglass blocks is researched as the third topic. Plexiglass can replace the system of a resist and a substrate. A new approach to writing down the structures by electron beam is presented, minimizing thermal stress on the plexiglass block during the exposure. The writing method also improves the homogeneity of exposed motifs. A method for computing the exposure dose for specific multilevel structures was designed. This method is based on the existing model of proximity effect computation and it minimizes the computing time necessary to obtain the exposure doses.
|
|
|
CSS3 Style Sheet Analyzer Extensions
Mikulík, Petr ; Bartík, Vladimír (referee) ; Burget, Radek (advisor)
Thesis extends an existing open source CSSBox project by adding support for new CSS3 properties to its jStyleParse parser. Specifically, support for box-shadow, grid layout and finaly CSS animations and transitions was added. Thesis is, just like the original project, writen Java and consists of a series of data structures, implementation methods and testing classes. The result is a git pull request on Github.com over the original project repository. All changes related to this thesis are applied to the project and are therefore part of it.
|
|
|
Integration of nanostructures into functional devices
Citterberg, Daniel ; Mikulík, Petr (referee) ; Kolíbal, Miroslav (advisor)
This master thesis is focused on characterization of electrical transport properties of one-dimensional nanostructures. First section of this work deals with theoretical description of the experimental approaches to realization of such measurements. This section involves also a detail discussion of preparation of contacts using e-beam lithography. Next, theoretical description of characterization of nanostructures using photoluminescence measurements is given. Second section describes practical application of the aforementioned electrical transport measurements. Presented results include transport and photoluminescence measurements of WS2 nanotubes, InAs and WO2.72 nanowires. The last section of this thesis deals with nanowire quantum well heterostructures. The section provides both a deeper theoretical view of the problem and results of the photoluminescence measurements are shown.
|
|
|
CREATION OF NANOSTRUCTURES ON SURFACES OF SOLID MATTER USING HYBRID METHODS
Rudolfová, Zdena ; Mikulík, Petr (referee) ; Horová, Ivana (referee) ; Kolíbal, Miroslav (advisor)
This thesis deals with the study of GaAs surface properties and with methodology of metal (mainly gold) nanoparticles deposition on GaAs substrate. GaAs has complicated surface oxides structure, which are very reactive when exposed to various chemicals (both acids and alkalines) and therefore they change GaAs surface properties. That is why the study of this properties is crucial for understanding of GaAs surface reactions on metal particles colloidal solution, from which the nanoparticles are deposited on the surface. The possibilites of GaAs surface etching and passivation are discussed. These should lead to surface stability enhancement during colloidal nanoparticles deposition. There was also studied the influence of adhesive polymer monolayer grown on GaAs substrate to the amount of nanoparticles deposited to the surface after substrate immersion into colloidal solution. This thesis concentrates on analyzing of methods, how the gold colloidal nanoparticles can be deposited selectivelly, only to defined areas. The areas were defined using charged particle beam.
|
|
|
Šikmost v teorii optimalizace a eficience portfolia
Mikulík, Petra ; Branda, Martin (advisor) ; Lachout, Petr (referee)
In this thesis we study models, which search for an optimal portfolio from a set of stocks. On the contrary to the classical approach focusing only on expected return and variance, we examine models where an additional crite- rion of skewness is included. Furthermore we formulate a model for measuring performance of a portfolio defined as the distance from the Pareto efficient frontier. In numerical experiments we apply the models on historical prices and stock data from the electronic stock market NASDAQ. We analyze the stock data from companies listed in the index NASDAQ-100. We conclude by comparing of optimal portfolios created using different models among each other, with trivial single-stock portfolios and the with NASDAQ-100 index itself.
|
guest ::
RSS feed.