Preparation and characterization of silicon-based materials

Název práce: Příprava a charakterizace materiálů na bázi nanostrukturního křemíku Autor: Miroslav Šlechta Katedra / Ústav: Katedra chemické fyziky a optiky Vedoucí bakalářské práce: doc. RNDr. Juraj Dian, Csc., Katedra chemické fyziky a optiky Abstrakt: Porézní křemík je nanostrukturní materiál na bázi křemíku. Byl připraven anodickým leptáním krystalického křemíku v kyselině fluorovodíkové. Fyzikální a chemické vlastnosti porézního křemíku vyplývají z rozměrů nanokrystalů, které se pohybují v rozmezí jednotek až desítek nanometrů. U nanostrukturního křemíku se, v porovnání s objemovým krystalickým křemíkem, projevují unikátní vlastnosti které závisí na míře kvantového rozměrového jevu a jevech na jeho velkém vnitřním povrchu. Vhodnou volbou použitého křemíkového substrátu, zejména z hlediska vodivosti a krystalografické orientace, a technologických podmínek (zejména složení elektrolytu, doby leptání a proudové hustoty), lze připravit nanostrukturní materiál o různé velikosti pórů - makroporézní, mesoporézní a mikroporézní křemík a o různém zastoupení vazeb Si-O a Si-H. Morfologie a chemické složení povrchu porézního křemíku o něm dovolují uvažovat jako o vhodném materiálu pro oblast aplikací - zvláště senzorů chemických látek a biosenzorů, optoelektroniky a aplikací biomedicínských. Byly připraveny vzorky...Title: Preparation and characterization of silicon-based materials Author: Miroslav Šlechta Department: Department of Chemical Physics and Optics Supervisor: doc. RNDr. Juraj Dian, Csc., Department of Chemical Physics and Optics Abstract: Porous silicon is nanostructured material based on silicon. He was prepared by anodic etching of crystalline silicon in hydrofluoric acid. Physical and chemical properties of porous silicon nanocrystals resulting from the dimensions, which range from units to tens of nanometers. For nanostructured silicon compared to crystalline silicon, exhibit unique properties that depend on the degree of quantum dimensional phenomena and phenomena on its large internal surface. Suitable choice of the silicon substrate, particularly in terms of conductivity and crystallographic orientation, and technological conditions (in particular electrolyte composition, the etching time and current density) can be prepared nanostructured materials of different pore sizes - macroporous, mesoporous and microporous silicon and varying representation Si-O and Si-H bonds. Morphology and chemical composition of the surface of porous silicon allows to think of it as a suitable material for a range of applications - particularly chemical sensors and biosensors, optoelectronics and biomedical applications....Department of Chemical Physics and OpticsKatedra chemické fyziky a optikyFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Spectroscopy of close visual binary components of the stable shell star 1 Del

Stable shell stars are ideal objects for studying basic physical principles of the formation of disks in Be stars. If these stars have a close unresolved visual companion, its contribution toward the modelling of the disk cannot be overlooked, as is sometimes done. The study aims to spectroscopically resolve close visual binary Be (shell) star 1 Del, which up to now was only resolved by speckle or micrometric measurements. The integral field spectroscopy obtained by the SINFONI spectrograph at the VLT telescope in the European Southern Observatory (ESO) in the infrared region was used; we supplemented these observations with visual spectroscopy with the Perek Telescope at the Ondrejov Observatory. Spectra of 1 Del were successfully resolved, and, for the first time, spectra of 1 Del B were obtained. We found that 1 Del A is a Be/shell star, while 1 Del B is not an emission-line object.Comment: accepted to Astronomy And Astrophysic

Emission features in a B[e] binary system V2028 Cyg

We present a preliminary analysis of our six-year observation campaign of the B[e] stellar system V2028 Cyg (MWC 623). The time variability of spectral features is described

Vliv povrchové úpravy a elektrických kontaktů na transport náboje v halogenidových perovskitech

V této diplomové práci se zabývám transportem náboje v halogenidových perovskitech. To je provedeno pomocí charakterizační metody, kterou je zde voltampérová charakteristika. Tou je studován vliv proudu a napětí na připravený vzorek, také při různých teplotách. Byla zjištěna značná citlivost materiálu na historii měření. Odvozená vyhodnocení, této měřící techniky, dále poskytují možnosti detekce hysterezního chování a také vyhodnocení měření v čase pro zjištění časové stability sběru nosičů. Tímto byl také prokázán jev elektromigrace defektů. Z časových měření byly dále spočteny transportní parametry, které poukazují na jejich nemonotónní vývoj v rostoucích teplotách. Byly navrženy teoretický model, vysvětlující takové chování, jako možnost dalšího výzkumu na perovskitech a rozvinutí tohoto tématu.In this thesis, I study charge transport in halide perovskites. This is done using the characterization method, which here is the I-V characteristics. It studies the effect of current and voltage on the prepared sample, also at different temperatures. A significant sensitivity of the material to the measurement history was found. Derived evaluations of this measurement technique further provide possibilities for the detection of hysteresis behavior as well as the evaluation of measurements over time to determine the temporal stability of carrier collection. This also proved the phenomenon of electromigration of defects. Furthermore, transport parameters were calculated from the time measurements, which point to their non-monotonic development in increasing temperatures. A theoretical model explaining such behavior was proposed as a possibility for further research on perovskites and development of this topic.Fyzikální ústav UKInstitute of Physics of Charles UniversityMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Preparation and characterization of silicon-based materials

Title: Preparation and characterization of silicon-based materials Author: Miroslav Šlechta Department: Department of Chemical Physics and Optics Supervisor: doc. RNDr. Juraj Dian, Csc., Department of Chemical Physics and Optics Abstract: Porous silicon is nanostructured material based on silicon. He was prepared by anodic etching of crystalline silicon in hydrofluoric acid. Physical and chemical properties of porous silicon nanocrystals resulting from the dimensions, which range from units to tens of nanometers. For nanostructured silicon compared to crystalline silicon, exhibit unique properties that depend on the degree of quantum dimensional phenomena and phenomena on its large internal surface. Suitable choice of the silicon substrate, particularly in terms of conductivity and crystallographic orientation, and technological conditions (in particular electrolyte composition, the etching time and current density) can be prepared nanostructured materials of different pore sizes - macroporous, mesoporous and microporous silicon and varying representation Si-O and Si-H bonds. Morphology and chemical composition of the surface of porous silicon allows to think of it as a suitable material for a range of applications - particularly chemical sensors and biosensors, optoelectronics and biomedical applications...

Charge transport in halide perovskites affected by the surface treatment and metalization.

In this thesis, I study charge transport in halide perovskites. This is done using the characterization method, which here is the I-V characteristics. It studies the effect of current and voltage on the prepared sample, also at different temperatures. A significant sensitivity of the material to the measurement history was found. Derived evaluations of this measurement technique further provide possibilities for the detection of hysteresis behavior as well as the evaluation of measurements over time to determine the temporal stability of carrier collection. This also proved the phenomenon of electromigration of defects. Furthermore, transport parameters were calculated from the time measurements, which point to their non-monotonic development in increasing temperatures. A theoretical model explaining such behavior was proposed as a possibility for further research on perovskites and development of this topic

Specification of Short Sea Shipping and its use as an alternative to truck transportation

The goal of the thesis is to find out wether it's possible to consider short sea shipping as an adequate alternative to trucking. The thesis describes the specifics of Short Sea Shipping and its main maritime route. It also compares the advantages and disadvantages of short sea shipping and truck transportation. Furthermore the thesis assesses their economical aspects and the potential risks associated with these means of transport. The conclusion of the thesis recommends the suitable routes and comes up with other circumstances that should be considered while using Short Sea Shipping as a trucking alternative