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Nonlinear optical properties of semiconductor nanostructures
Kořínek, Miroslav
Title: Nonlinear optical properties of semiconductor nanostructures Abstract: Laser ablation of solid state wafer in liquids is a simple and reliable method for creation of nanocrystals of almost any kind of metals and semiconductors. We performed pulsed laser ablation of a silicon wafer in deionized water to prepare colloidal silicon nanocrystals. The samples were prepared by femtosecond laser ablation using Ti: sapphire laser (wavelength 800 nm, pulse duration 100 fs, pulse energy 0.06 mJ - 0.7 mJ, repetition rate 1 kHz) and characterised by time-integrated photoluminescence spectroscopy, extinction measurements, transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and time-resolved measurements of photoluminescence. The time-integrated photoluminescence spectrum demonstrated a blue emission. In addition, we observed that aging of nanocrystals in deionized water for several weeks improved the photoluminescence intensity. It is generally accepted that the unique properties of Si nanocrystals result from both quantum confinement size effect and surface states. Modification and oxide passivation of surface states and defects in oxide layer can effectively increase the photoluminescence intensity. Using extinction measurement it was found that absorption of nanocrystals is...
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Time-resolved spectroscopy of semiconductor nanostructures
Kořínek, Miroslav ; Trojánek, František (advisor) ; Herynková, Kateřina (referee) ; Němec, Hynek (referee)
Title: Time-resolved spectroscopy of semiconductor nanostructures Author: RNDr. Miroslav Kořínek Department: Department of Chemical Physics and Optics Supervisor: doc. RNDr. František Trojánek, Ph.D., Department of Chemi- cal Physics and Optics, Faculty of Mathematics and Physics, Charles University in Prague Abstract: This Ph.D. thesis is focused on the study of relaxation and re- combination processes in silicon nanocrystals embedded in dielectric (SiO2, SiC and Si3N4) matrices that were fabricated within the EU 7th Framework Pro- gramme Silicon Nanodots for Solar Cell Tandem (NASCEnT). Different host ma- terials, in which silicon nanocrystals are incorporated, not only provide different transport properties, but also differently affect the nanocrystal surfaces. A large part of the thesis is devoted to research of SiO2-embedded silicon nanocrystals having various sizes (in the order of nanometers) and various inter-nanocrystal separation, that differ also in the manner of an additional annealing. Experimen- tal techniques of optical spectroscopy are used to monitor the photoexcited charge carrier dynamics on a wide time scale from picoseconds to milliseconds. The initial (picosecond) dynamics is characterized very well using a relevant rate equation. We propose a theoretical description of how the...
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Nonlinear optical properties of semiconductor nanostructures
Kořínek, Miroslav
Title: Nonlinear optical properties of semiconductor nanostructures Abstract: Laser ablation of solid state wafer in liquids is a simple and reliable method for creation of nanocrystals of almost any kind of metals and semiconductors. We performed pulsed laser ablation of a silicon wafer in deionized water to prepare colloidal silicon nanocrystals. The samples were prepared by femtosecond laser ablation using Ti: sapphire laser (wavelength 800 nm, pulse duration 100 fs, pulse energy 0.06 mJ - 0.7 mJ, repetition rate 1 kHz) and characterised by time-integrated photoluminescence spectroscopy, extinction measurements, transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and time-resolved measurements of photoluminescence. The time-integrated photoluminescence spectrum demonstrated a blue emission. In addition, we observed that aging of nanocrystals in deionized water for several weeks improved the photoluminescence intensity. It is generally accepted that the unique properties of Si nanocrystals result from both quantum confinement size effect and surface states. Modification and oxide passivation of surface states and defects in oxide layer can effectively increase the photoluminescence intensity. Using extinction measurement it was found that absorption of nanocrystals is...
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The concept of control in consolidated financial statements
Kořínek, Miroslav ; Vašek, Libor (advisor) ; Zelenka, Vladimír (referee)
The concept of control is an important determinant of consolidated financial statements. Group of economically related entities and its consolidated financial statements are identified by control concept. Conception of control lies in the model of determination of entities controlled. The evolution of control concept points out, that some entities have not always been integrated in the group or have not been considered controlled. Information value of consolidated financial statements resulting from the control concept is directly influenced by this non-integration represented e.g. by off-balance sheet accounting and Special Purpose Entities. Thesis examines and analyzes present and previous models of control concept of U.S. GAAP, IAS/IFRS and its converged principles.
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Financial consolidation - data processing
Kořínek, Miroslav ; Vašek, Libor (advisor)
The consolidation process within an international group is illustrated in a Czech company view. Based on Parent Corporation's system, the individual financial statements are modified in order to aggregate consolidated statements. The theoretical section refers to consolidation terms and rules in accordance with Czech legislation. The data processing is reviewed and several procedures are detailed such as the intercompany confirmation scheme. Resulting operations are applied and summarized on practical corporation - based consolidation exercise.
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