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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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Deposition and characterization of GaN nanocrystals with a metal core
Čalkovský, Vojtěch ; Čech, Vladimír (referee) ; Mach, Jindřich (advisor)
Tato diplomova prace se zabyva prpravou a charakterizac GaN nanokrystalu s kovovym jadrem. V teoreticke casti teto prace je predstaven material GaN se svymi vlastnos- tmi a aplikacemi. Dale jsou uvedeny substraty pro rust a jednotlive mechanismy rustu GaN nanokrystalu. V dalsm jsou popsany kovove nanocastice a jejich opticke vlastnosti umoznujc zesilovan fotoluminiscence na zaklade interakce plasmonu a GaN. Experi- mentaln cast se zabyva prpravou GaN nanokrystalu s Ag jadrem ve ctyrech krocch. Prvne jsou Ag nanocastice naneseny na substrat Si(111). Nasledne se nechaj zoxidovat. Tretm krokem je depozice Ga a poslednm je nitridace. Jednotlive kroky byly opti- malizovany a analyzovany ruznymi metodami, jako je XPS, SEM, fotoluminiscence a Ramanova spektroskopie.
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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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Market survey of high power semiconductor devices
Jankovský, Martin ; Rujbrová, Šárka (referee) ; Zmrzlá, Petra (advisor)
Hlavním tématem práce jsou moderní výkonové polovodičové součástky. Jsou diskutovány i rozvíjející se materiály s velkou šířkou zakázaného pasu a jejich elektrické vlastnosti. Práce je pak zaměřena na tyto moderní součástky, včetně jejich teorie, aplikace a dostupnosti na trhu. Dále práce předkládá tabulky jednotlivých zařízení, které jsou nabízeny evropskými předními výrobci polovodičů.
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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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Thermal Desorption Spectroscopy (TDS) and its Application for Research of Surface Processes
Potoček, Michal ; Čech, Vladimír (referee) ; Pavlík, Jaroslav (referee) ; Dub, Petr (advisor)
ermal desorption spectroscopy (TDS) is a common method for surface analysis of adsorbed molecules. In chapter 1 the work deals with the theoretical background of this method and shows the principles of a desorption process influenced by subsurface diffusion. Chapter 2 first shows application of TDS for detection of surface molecules and determination of binding energy.Experiments were mainly focused on ditermination of surface adsorbents and impurities on Si wafers. The second part of chapter 2 describes desorption of atoms of a Ga layer on Si surface and their subsurface diffusion. A Ga diffusion process was also observed by with secondary ion mass spectrometry (SIMS) and numerically simulated.
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Development and Application of an UHV Equipment for Deposition of Thin Films (Atomic and Ion Systems)
Mach, Jindřich ; Čech, Vladimír (referee) ; Lencová, Bohumila (referee) ; Šikola, Tomáš (advisor)
In the thesis the development of two equipment for preparation of ultrathin films under ultrahign vacuum conditions (UHV) is discussed. Here, additionally to a brief description of theoretical principles, more details on the design of these units are given. In the first part the design of a thermal source of oxygen or hydrogen atomic beams is discussed. Further, a design and construction of an ion–atomic beam source for ion-beam assisted deposition of thin films is detailed. The source combines the principles of an efusion cell and electron-impact ion beam source generating ions of (30 – 100) eV energy. The source has been successfully applied for the growth of GaN on the Si(111) 7x7 substrate under room temperature.
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Selective gallium nitride thin-film growth on substrates covered by pyrolyzed resist mask
Novák, Tomáš ; Kostelník, Petr (referee) ; Voborný, Stanislav (advisor)
This thesis deals with deposition of GaN thin films and GaN selective growth utilizing pyrolyzed resist masks. Carbon masks were prepared on silicon substrates by electron-beam litography and resist pyrolysis. As a further step, Ga and GaN were deposited on the masked substrates by Moleculer Beam Epitaxy (MBE) method. A selective growth of Ga droplets was achieved. These results were used for preparation of GaN crystallites by pulse deposition. It is also shown that direct MBE deposition of GaN on the masked substrates leads to a selective growth of GaN thin films with GaN film growing only on the areas which are not covered by the carbon mask. The results are explained by enhanced surface diffusion of gallium atoms on the surface of the carbon mask.
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Development of Atomic- and Ion Beam Sources
Šamořil, Tomáš ; Lencová, Bohumila (referee) ; Mach, Jindřich (advisor)
The objective of this master thesis was to provide the optimization of an ion-atom beam source for the improvement of its properties. The improvement of the parameters increases the efficiency of the source during the deposition of gallium nitride ultrathin films (GaN) being important in microeletronics and optoelectronics. After optimization, the depositions of GaN ultrathin films on Si(111) 7x7 at lower temperatures (
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