|
|
Reconstruction of ion gun and its application for deposition of thin films and nanostructures
Novák, Tomáš ; Mach, Jindřich (referee) ; Voborný, Stanislav (advisor)
This bachelor´s thesis deals with modification and experimental application of the ion device, generating and transporting nitrogen ion beam with energy in a range of 10-100 eV. Together with gallium effusion cell, this device can be used for deposition of gallium nitride (GaN) thin films. Nitrogen ion beam current significantly increased by shortening the optical part of the ion gun. A differential pumping provides the system with ultrahigh-vacuum conditions in the deposition chamber. Profiles of ion current density, appropriate for GaN depositions, were found by the optimization of potentials applied on electrodes of the ion gun. Due to increase of nitrogen-ion current, the depositon rate of the system raised from about tenth of nm/h to more than 10 nm/h. For experiments described in this paper, monocrystalline silicon (111) was used as a substrate. The effect of gallium and nitrogen ion fluxes on GaN growth was investigated, together with the effect of gold nanoparticles on a GaN growth. Thin films were analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Several specific morphologies of thin films were observed.
|
|
|
Optimization of device for measurement field emission from GaN nanocrystals surface
Horák, Stanislav ; Kromka, Alexander (referee) ; Mach, Jindřich (advisor)
This diploma thesis deals with the design and optimization of the device for measurement of field emission from gallium nitride (GaN) nanocrystals surface. The first part of the thesis is the topic review, which contains the introduction to the problematics of field emissio focused on GaN. Then there were designed, constructed and optimized two versions of the device for the measurement of field emission. Through the optimization phase, the first successful test has been performed with zinc oxide (ZnO) nanowires. Simultaneously GaN nanocrystals were fabricated on the silicon substrate Si(111) with 2 nm of silicon dioxide SiO2 and also on the copper foil covered by graphene by molecular beam epitaxy (MBE). In the last chapter, there are presented the results of the measurement for emission of GaN nanocrystals. Finally, this study is comparing results with the current research in the area of field emission, which displays the improved characteristics for field emission of GaN nanocrystals on the copper foil covered by graphene.
|
|
|
The deposition of Ga and GaN nanostructures on silicon and graphene substrate
Novák, Jakub ; Jarý, Vítězslav (referee) ; Mach, Jindřich (advisor)
The thesis is focused on the study of properties of GaN nanocrystals and Ga structures on the surface of silicon and graphene substrate. In the theoretical part of this thesis, the basic properties of Ga/GaN and graphene are described, as well as their applications or connection of both structures together in different devices. The ability of metal nanoparticles to enhance not only photoluminescence, due to the interaction of the material with surface plasmons, is also shown in several examples. The experimental part of the work first deals with the production and characterization of graphene sheets prepared by Chemical Vapor Deposition. Ga/GaN growth on both types of substrates was performed in a UHV chamber using an effusion cell for Ga deposition and an atomic ion source for nitridation. Prepared structures were characterized using various methods (XPS, SEM, AFM, Raman spectroscopy or photoluminescence). In the last step, GaN nanocrystals were coated with Ga islands to study the photoluminescence enhancement.
|
|
|
Studies of molecular beams of organic materials
Maniš, Jaroslav ; Průša, Stanislav (referee) ; Mach, Jindřich (advisor)
This bachelor's thesis deals with assembling of low-temperature efussion cell which is suitable for deposition of organic materials. The calibration of operating temperature of effusion cell is performed. Depositions of organic semiconductor material are realized. Morphology of surface of thin film is studied in AFM and SEM microscope. In the paper background research on the utilization of organic materials in semiconductor industry is presented.
|
|
|
Selective growth of GaN on SiN
Hulva, Jan ; Kolíbal, Miroslav (referee) ; Mach, Jindřich (advisor)
This bachelor's thesis deals with the selective growth of gallium and gallium nitride on silicon nitride (SiN) substrates. Thin silicon nitride layers are deposited on silicon substrates. Oxide structures are prepared by the local anodic oxidation method (LAO) on SiN substrates. These surfaces can be editionally modified by etching in hydrofluoric acid. Modified substrates are used for the deposition of gallium or gallium nitride under ultra-high vacuum conditions. Consequently, ordering of deposited material was studied in areas modified by LAO. Chemical state of layers is studied by X-ray photoelectron spectroscopy. Morphology of surfaces is measured by the atomic force microscope (AFM).
|
|
|
Upgrade of the device for depositions by ion beam sputtering
Páleníček, Michal ; Mach, Jindřich (referee) ; Bábor, Petr (advisor)
This thesis deals with concept and realization of device which allows loading without air intake. Vacuum technology and its theoretical bases are discussed as well. Moreover the thesis is based on description of the current deposition chamber and its principles. The main part deals with the description of the concepts of lock and load systems. The first concept that has not been realized is described just briefly. The second one is thorough with description of the individual solutions and methods. The work also contains simple instructions how to install the specimen. At the end are described some outputs of simulations that have been done to comprehend and solve any problems that might occur as specimen holder cooling and deflection of magnetic rod.
|
|
| |
|
| |
|
|
Adaptation of the UHV SEM system for growth and characterization of nanostructures
Skladaný, Roman ; Mach, Jindřich (referee) ; Páleníček, Michal (advisor)
This bachelor thesis presents mechanical design of an objective protection of ultrahigh vacuum scanning electron microscope (UHV SEM), which is a part of a complex modular UHV system used for growth, observation and characterisation of nanostructures. Main physical and technical working principles of the UHV SEM system are explained. Furthermore, adaptation of a Knudsen cell used for growth of ultrathin layers in the UHV SEM system is described. Finally, a mechanical design of a shutter reducing overheating and contamination of objective during in situ growth and observation of nanostructures is drafted. The objective shutter also protects the sample from ambient heat radiation in case that sample is cooled to cryogenic temperatures.
|
|
|
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.
|
guest ::
RSS feed.