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Sequential growth of GaN nanocrystals on SiO2 substrate modified by FIB method
Flajšmanová, Jana ; Voborný, Stanislav (referee) ; Mach, Jindřich (advisor)
This bachelor's thesis deals with the selective growth of gallium (Ga) and gallium nitride (GaN). In theoretical part, there is a brief description of growth of ultrathin films with respect to GaN and their manufacturing. Experimental part is aimed to the deposition of Ga and GaN on silicon substrates Si(1 1 1). Substrates with the native silicon dioxide layer (SiO2) were modified by focused ion beam (FIB). GaN was deposited by pulsed deposition followed by postnitridation. Prepared samples were studied by atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM).
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Reconstruction of Sparse Sampled Images with Deep Learning
Le, Hoang Anh ; Hradiš, Michal (referee) ; Juránek, Roman (advisor)
The main goal of this thesis was to increase reconstruction quality of sparse sampled microscopic images by using neural networks. The thesis will cover various approaches for image reconstruction and will also include descriptions of implementations, which were used. Implementations will be evaluated based on quality of reconstruction, but also based on segmentation, which could be their main possible application.
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Preparation and analysis of nanostructures in UHV conditions
Gloss, Jonáš ; Spousta, Jiří (referee) ; Mach, Jindřich (advisor)
Cílem této bakalářské práce bylo skoumání přípravy a analýzy nanostruktur v podmínkách vysokého vakua (VV). Teoretická část klade důraz na gallium nitridové (GaN) nanostruktury. Ty pak byly analyzovány rastrovacím tunelovacím mikroskopem (RTM). Aby bylo možné analyzovat připravené vzorky ve VV RTM, bylo provedeno elektrochemické leptání wolfrámového drátu. Tato práce zhrnuje postup k vytvoření wolfrámových hrotů pro RTM. Kapitola o výrobě wolfrámových hrotů zahrnuje popis princípu elektrochemického leptání. Obrázky vyleptaných hrotů byly provedeny pomocí rastrovacího elektronového mikroskopu. Zaostřování hrotů pak bylo vykonáno fokusovaným iontovým svazkem. V této práci je také představena metoda pro opětovné ostření RTM hrotů elektronovým svazkem, vykonávaná in-situ. Bylo dokázáno, že je možné rutinně obdržet wolfrámové hroty s poloměrem křivosti rádovo v nanometrech.
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Optimization of the radiofrequency atomic source for deposition of GaN
Kern, Michal ; Wertheimer, Pavel (referee) ; Mach, Jindřich (advisor)
This thesis is focused on construction and optimization of radiofrequency atomic dissociation source of atomic nitrogen for depostion of GaN. The theoretical part deals with atomic sources, growth of ultrathin layers and the issue of radiofrequency circuits, with emphasis on their design using Smith chart. Methods for synthesis of GaN ultrathin layers and deposition are also discussed. In the experimental part, design and realization of various congurations of the impedance matching network is described. Using the impedance matching network a nitrogen plasma discharge was successfuly created and its spectrum was analysed. Afterwards, design and realization of a stepper motor control for the impedance matching network is described.
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Deposition of GaN nanocrystals with Ga droplets
Novák, Jakub ; Voborný, Stanislav (referee) ; Mach, Jindřich (advisor)
This bachelor thesis deals with preparation and characterization of Ga structures and GaN nanocrystals. In the theoretical part, properties and applications of GaN are introduced. Further, some substrates for the growth and some techniques used for manufacturing of these structures are stated. Further, is also mentioned the photoluminiscence of GaN. The experimental part deals with preparation of Ga and GaN structures and combination of both. These structures were further analyzed by various methods such as XPS, SEM or photoluminiscence.
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Increasing quality of facial images using sequence of images
Svorad, Adam ; Mezina, Anzhelika (referee) ; Burget, Radim (advisor)
Diplomova praca sa zameriava na oblast zaostrovania obrazkov tvari. V teoretickej casti prace budu prezentovane moderne metody zaostrovania obrazkov pomocou jedineho obrazku a metody editacie obrazkov. Prakticka cast sa zameria na pristupy rekonstrukcie obrazkov zo sekvencie poskodenych obrazkov. Viacere modely neuronovych sieti so vstupom pre viacero obrazkov budu zhotovene a vyhodnotene. Alternativny pristup v podobe balika nastrojov na editaciu obrazkov bude taktiez predstaveny. Tieto nastroje budu vyuzivat najmodernejsie pristupy k editacii obrazkov s cielom spojit vizualne prvky tvari zo vstupnej sekvencie obrazkov do jedneho finalneho vystupu. V zavere prace budu vsetky metody navzajom porovnane.
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Generative Adversial Network for Artificial ECG Generation
Šagát, Martin ; Ronzhina, Marina (referee) ; Hejč, Jakub (advisor)
The work deals with the generation of ECG signals using generative adversarial networks (GAN). It examines in detail the basics of artificial neural networks and the principles of their operation. It theoretically describes the use and operation and the most common types of failures of generative adversarial networks. In this work, a general procedure of signal preprocessing suitable for GAN training was derived, which was used to compile a database. In this work, a total of 3 different GAN models were designed and implemented. The results of the models were visually displayed and analyzed in detail. Finally, the work comments on the achieved results and suggests further research direction of methods dealing with the generation of ECG signals.
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Generating Faces with Generative Adversarial Networks
Konečný, Daniel ; Herout, Adam (referee) ; Kolář, Martin (advisor)
Cílem této práce je generování barevných obrázků obličejů z náhodně určených vysokodimenzionálních vektorů pomocí generativních neuronových sítí. Dále se zabývá analýzou vstupních vektorů na základě příznaků obličejů z nich vygenerovaných. Je provedena implementace generativní neuronové sítě pro generování obrázků ručně psaných číslic, poté dalších dvou sítí pro generování obrázků obličejů. Vygenerované obrázky zobrazují věrohodně vypadající obličeje, lidské oko je však dokáže odlišit od fotek reálných osob. Analýza jednotlivých dimenzí vektorů je provedena pomocí Studentova t-testu. Dále jsou vstupní vektory promítnuty do podprostorů pomocí lineární diskriminační analýzy a jsou nalezeny rozdělovací hranice mezi třídami příznaků. Analýza generovaných dat dokazuje, že ovlivněním vstupního vektoru je možné docílit generování obrázku obličeje s požadovanými příznaky s pravděpodobností až 80 %. Hlavním výsledkem této práce je model generativní neuronové sítě určené pro generování obrázků obličejů. Dalším přínosem je nástroj pro generování obrázků obličejů na základě vybraných příznaků.
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Drivers for power switching transistors GaN MOSFET
Fiala, Zbyněk ; Pazdera, Ivo (referee) ; Vorel, Pavel (advisor)
The thesis describes the procedure during the proposal of the driver circuits for the GaN MOSFET transistors, which are known for their fast switching especially. In the first instance of this thesis the issue of GaN MOSFET transistors is described and also the thesis describes the different types of MOSFET transistors in the way of their electrical and mechanical attributes. The specific type driver circuit is stated in the thesis, which was selected in the semestral thesis. For this circuit the boost converter with an output power 600W and high switching frequency 800kHz was proposed as an attempt measurement circuit. This boost converter was measured after its construction was done. The waveforms captured by the oscilloscope are commented also. In the conclusion the assessment is done about this new technology of power switching transistors.
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The deposition of Ga and GaN nanostructures with metal core
Čalkovský, Martin ; Jarý,, Vítězslav (referee) ; Mach, Jindřich (advisor)
The presented thesis deals with preparation of GaN nanocrystals with a metal core. In the theoretical part of the thesis GaN with its properties and applications is introduced. Further, some of the preparation methods of GaN are presented, mainly focusing on MBE growth. Deposition of metal NPs from colloidal solution and the state of the art approaches to enhance luminescence of GaN based structures is discussed. The experimental part follows three steps of preparation of GaN crystals with the Ag core. In the first step the Ag NPs are deposited on the Si(111) substrate. In the second step the Ga deposition process is optimized and in the third step the deposited Ga is transformed into GaN. After the Ga deposition the samples were analyzed by SEM/EDX and SAM/AES. The properties of prepared GaN crystals with the Ag core were studied by XPS, photoluminescence and Raman spectroscopy.
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