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Deposition of GaN nano structures on Si(111) 7x7
Šťastný, Jakub ; Horák, Michal (referee) ; Mach, Jindřich (advisor)
The thesis is focused on the study of growth of 2D GaN nanocrystals on Si(111) 7x7. In the theoretical part of this thesis the properties of 3D and 2D GaN, main methods used for growth of GaN and 2D GaN and applications of GaN are described. The experimental part of this thesis describes in detail the method of low temperature droplet epitaxy with assistance of ions, which was used for series of deposition of 2D GaN under different angles of ion beam. The deposition was done in the complex UHV system in the ÚFI VUT labs in Brno. The nanocrystals were analysed by SEM and AFM.
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Nanoscopy, spectroscopy and modication of individual nanoobjects in liquid environment
Smísitel, Petr ; Valenta, Jan (advisor) ; Galář, Pavel (referee)
In this diploma thesis we will study the luminescence properties of nanocrystals. We will summarize the basic division according to size and standard method of theoretical description of semiconductor and metal nanocrystals. We will describe the luminescence properties of nanocrystals and the influence of the surrounding environment. In the se- cond part of the thesis we will follow up the construction of an apparatus for imaging luminescence spectroscopy intended for the measurement of individual nanoobjects in a liquid environment. Finally, we will study luminescence properties of organixally passi- vated metal clusters in a liquid environment with changes in temperature and excitation intensity. We compare the luminescence of gold nanocrystals with and without long po- lyethylene glycol chains bound on the surface. 1
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Study of optical nonlinearities in semiconductors and semiconductor nanostructures
Chlouba, Tomáš ; Trojánek, František (advisor) ; Filip, Radim (referee) ; Herynková, Kateřina (referee)
In the main part of this thesis I study the relaxation mechanisms of charge carriers in silicon nanocrystals in SiO2 matrix. One of the potential applications of these structures lies in photovoltaics, specifically in construction of all-silicon tandem solar cells. I studied the dynamics of carriers in these structures by methods of ultrafast spectroscopy which helped to unravel the microscopic behaviour of carriers, their transport, localization etc. Furthermore I investigated the doping of such structures as the technology of doping is crucial for manufacture of pn- junctions which are the core component of solar cells. At the end I delve into the dissipative Jaynes-Cummings model by mathematical modeling and theoretical calculations which describes among others microlasers and as such comes under a field of cavity quantum electrodynamics.
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Nanoscopy, spectroscopy and modication of individual nanoobjects in liquid environment
Smísitel, Petr ; Valenta, Jan (advisor) ; Galář, Pavel (referee)
In this diploma thesis we will study the luminescence properties of nanocrystals. We will summarize the basic division according to size and standard method of theoretical description of semiconductor and metal nanocrystals. We will describe the luminescence properties of nanocrystals and the influence of the surrounding environment. In the se- cond part of the thesis we will follow up the construction of an apparatus for imaging luminescence spectroscopy intended for the measurement of individual nanoobjects in a liquid environment. Finally, we will study luminescence properties of organixally passi- vated metal clusters in a liquid environment with changes in temperature and excitation intensity. We compare the luminescence of gold nanocrystals with and without long po- lyethylene glycol chains bound on the surface. 1
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Study of optical nonlinearities in semiconductors and semiconductor nanostructures
Chlouba, Tomáš ; Trojánek, František (advisor) ; Filip, Radim (referee) ; Herynková, Kateřina (referee)
In the main part of this thesis I study the relaxation mechanisms of charge carriers in silicon nanocrystals in SiO2 matrix. One of the potential applications of these structures lies in photovoltaics, specifically in construction of all-silicon tandem solar cells. I studied the dynamics of carriers in these structures by methods of ultrafast spectroscopy which helped to unravel the microscopic behaviour of carriers, their transport, localization etc. Furthermore I investigated the doping of such structures as the technology of doping is crucial for manufacture of pn- junctions which are the core component of solar cells. At the end I delve into the dissipative Jaynes-Cummings model by mathematical modeling and theoretical calculations which describes among others microlasers and as such comes under a field of cavity quantum electrodynamics.
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Terahertz radiation in nanostructures
Hendrych, Erik ; Ostatnický, Tomáš (advisor) ; Kozák, Martin (referee)
We explore conductivity of nanostructures in the terahertz range. We model the nanostructure as a square potential well with a barrier inside. We examine how the conductivity depends on temperature, material constants and dimensions of the potential well. The conductivity of the material determines the complex refractive index and thus influences its optical properties such as reflexivity, transmittance and attenuation coefficient. We construct the functional dependency of the conductivity on the electric field frequency. The maxima of this functional dependency correspond to spectral lines. We examined the dependency of the frequencies of the maxima (spectral lines) on various parameters. We got the most interesting result when we continuously changed the position of the barrier inside the potential well. For different heights of the barrier we got qualitatively different results. With high barrier the system behaves as two separate potential wells where we can see monotonous functional dependency of the spectral lines on the position of the barrier. With low potential barrier we get oscillating dependencies. For gallium arsenide and 2 nm width of the potential barrier, high barrier is higher than 1 eV, while low barrier is lower than 0, 05 eV.
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