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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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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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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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Selective growth of GaN layers on substrate modificated by method FIB
Mareš, Petr ; Voborný, Stanislav (referee) ; Mach, Jindřich (advisor)
The thesis deals with the selective growth of GaN crystals on the SiO2 layer. The theoretical part discusses the type of growth of ultrathin layers with focus on gallium nitride and its manufacturing. Moreover the text deals with principles of the focused ion beam and basic principles of other further methods which were used for analyzing the samples (AFM, XPS, photoluminescence spectroscopy). Experimental part consists of depositions of GaN. The silicon wafer Si(111) with native oxide SiO2 (1-2 nm) was used as a substrate. Focused ion beam was utilized to manufacture suitable structures on the substrate. Selective growth was acomplished with the use of the postnitridation method. Method of the pulse deposition was introduced with focus on increasing the volume of crystals.
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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).
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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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The photoluminescence properties measurement of ultrathin films
Metelka, Ondřej ; Mach, Jindřich (referee) ; Šamořil, Tomáš (advisor)
The thesis briefly describes the principles and types of luminescence. In the first following research of study is also discussed the equipment which is applicable to photoluminescence experiments, including the arrangement. The second research focuses on the influence of the properties of gallium nitride (GaN) (ultra) thin films and other structures prepared by various ways on shape of photoluminescence spectra. The paperwork also describes the further optimization of photoluminescent apparatus used for the measurement of photoluminescence spectrum in the UV light radiation which is located at the Institute of Physical Engineering at the Technical University. The extension of measurements at low temperatures (design and construction of its own cryostat) is added. The conclusion concernes the test measurements to determine the effect of various settings of the apparatus on the resulting measured photoluminescence spectrum.
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