National Repository of Grey Literature 67 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Interaction of organic molecules with metal passivated semiconductor surfaces studied via STM
Zimmermann, Petr ; Sobotík, Pavel (advisor)
Title Interaction of Organic Molecules with Metal Passivated Silicon Surfaces Studied via STM Author Petr Zimmermann Department Department of Plasma and Surface Science Supervisor Doc. RNDr. Pavel Sobotík, CSc. Department of Plasma and Surface Science Abstract Organic molecules offer a wide range of optical, electronic or chemical properties. Coupling them to silicon could pave way to novel applications and devices, however, a controlled molecular functionalization of silicon remains challenging due to the presence of highly reactive dangling bonds on its surfaces. We attempt to decrease the reactivity of low index silicon surfaces with an ultra-thin layer of a metal adsorbates and study their interaction with organic molecules via scanning tunnelling microscopy. In the first part we investigate the interaction of ethylene, a small unsaturated molecule, with tin and indium 1D chains grown on Si(001) - 2 × 1. The chains consist of dimers structurally analogous to the dimers of the underlying Si(001) - 2 × 1 surface. Aided by photoelectron spectroscopy we find that the Sn chains are less reactive than the Si(001) surface and that the absence of a π dimer bond renders indium chains inert. In the second part we study the interaction of copper phthalocyanine, a small macrocyclic heteroaromatic compound, with the...
High Efficiency n-type Monocrystalline Silicon Solar Cells
Mojrová, Barbora ; Kolařík, Vladimír (referee) ; Poruba,, Aleš (referee) ; Boušek, Jaroslav (advisor)
Tato dizertační práce je zaměřena vývoj a ověřování nových postupů přispívajících ke zvýšení účinnosti bifaciálních solárních článků založených na monokrystalickém křemíku n-typové vodivosti. Tato práce přináší nové poznatky o vylepšených výrobních procesech a postupech použitých během výroby článků v ISC Konstanz. V rámci práce byly vyrobeny solární články typu n-PERT (Passivated Emitter Rear Totally diffused) s vysokou účinností, a to pomocí standartních procesů a zařízení používaných běžně při průmyslové výrobě. Zapojení těchto průmyslových postupů a metod umožnilo ověřit možnosti výroby n-typových článků za použití téměř totožného vybavení, jaké je potřeba pro výrobu p-typových článků. Zvýšení účinnosti bylo založeno především na vylepšení jednotlivých procesních kroků. Experimenty popsané v této práci dosvědčují zlepšení procesu difúze bóru, přizpůsobení parametrů pasivační a antireflexní vrstvy nově navrženému emitoru, zlepšení procesu metalizace ve smyslu využití past neobsahujících hliník, testování tisku rozličných motivů spolu s různými sekvencemi výpalu. V rámci práce byla testována možnost zamezení jevu potenciální indukované degradace (Potential Induced Degradation – PID) pomocí vhodného složení ARC a pasivační vrstvy. Vyrobené n-typové solární články dosáhly maximální hodnoty účinnosti 20,9 %.
Interaction of organic molecules with metal passivated semiconductor surfaces studied via STM
Zimmermann, Petr ; Sobotík, Pavel (advisor) ; Plšek, Jan (referee) ; Šikola, Tomáš (referee)
Title Interaction of Organic Molecules with Metal Passivated Silicon Surfaces Studied via STM Author Petr Zimmermann Department Department of Plasma and Surface Science Supervisor Doc. RNDr. Pavel Sobotík, CSc. Department of Plasma and Surface Science Abstract Organic molecules offer a wide range of optical, electronic or chemical properties. Coupling them to silicon could pave way to novel applications and devices, however, a controlled molecular functionalization of silicon remains challenging due to the presence of highly reactive dangling bonds on its surfaces. We attempt to decrease the reactivity of low index silicon surfaces with an ultra-thin layer of a metal adsorbates and study their interaction with organic molecules via scanning tunnelling microscopy. In the first part we investigate the interaction of ethylene, a small unsaturated molecule, with tin and indium 1D chains grown on Si(001) - 2 × 1. The chains consist of dimers structurally analogous to the dimers of the underlying Si(001) - 2 × 1 surface. Aided by photoelectron spectroscopy we find that the Sn chains are less reactive than the Si(001) surface and that the absence of a π dimer bond renders indium chains inert. In the second part we study the interaction of copper phthalocyanine, a small macrocyclic heteroaromatic compound, with the...
Morphology study of ultra thin layers by XPS analysis of multiple peaks of a single element
Pokorný, David ; Šik, Ondřej (referee) ; Polčák, Josef (advisor)
This diploma thesis deals with methodology of thin film thickness determination using X-ray radiation of silver anode which provides radiation with energy of 2984,3 eV. This energy is twice as high as the standard aluminium radiation which allows a measurement of new photoelectron lines with higher bonding energy and it also provides thanks to the higher photoelectron energy greater information depth. In order to get the right results it was necessary to calibrate the spectrometer Kratos Axis Supra in the silver anode mode first and found out the form of the transmission function. The determination of the thickness of the thin layer was demonstrated by the comparation of the ratio of different photoelectron lines intensities with the theoretical model. For that purpose was specifically used the Si 1s and Si 2p peak bound in the substrate in the Si-Si bonding or in the thin oxid layer in the Si-O bonding. The results show that for thin SiO2/Si film thickness determination is the best to use the intensity ratio of only one photoelectron line. A silver anode however provides greater information depth.
Luminescence Diagnostic of Photovoltaic Cells
Stojan, Radek ; Frantík, Ondřej (referee) ; Šály,, Vladimír (referee) ; Vaněk, Jiří (advisor)
Diagnostic of photovoltaic cells defects is one of the key step in production. This dissertation thesis deals about diagnosis of photovoltaic cells by radiative recombination of electron - hole pairs. This radiative recombination is known as luminescence. Diagnostic methods using this local light emission in infrared region have innovative potential. The method of electroluminescence is one of the most widely used luminescence methods whose modifications are applied across the industry, especially in semiconductors. The main area of this thesis research is focused on non-destructive analysis of radiated infrared radiation of monocrystalline and polycrystalline solar cells in various modifications of standard electroluminescence method. In this research there are used two types of CCD cameras are used as luminescent radiation detectors. Method of photon emission microscopy is used for magnification element. Local light emission inspection by microscopy should have benefit to qualitative evaluation of solar cells defects. Radiation emitted by the solar cell has a wave character. This fact brings the potential of using some of the characteristics of the waves. We are talking about the intensity and mainly about new characterization by polarization during the detection of defects in the solar cell surface. Innovation of the measuring workplace of the standard electroluminescence method to use polarization analysis is one of the goals of this dissertation thesis.
Study of catalytic decomposition of silica
Štubian, Martin ; Kolíbal, Miroslav (referee) ; Bábor, Petr (advisor)
This thesis deals with catalytic decomposition of silica using electron microscopy and Auger spectroscopy. The thesis is primarily focused on the Au-Si phase, which is created during in the reaction. In the theoretical part, the principle of used methods is described and recherche on the catalytic decomposition of silica is presented. The practical part contains the results of the measurements and their interpretation.
Nickel silicides layer by electron beam melting of electro deposited layer
Petr, Jiří ; Pantělejev, Libor (referee) ; Jan, Vít (advisor)
This master’s thesis deals with the possibility of creating a compact nickel-silicide layer on austenitic substrates. The theoretical part describes a variety of surface treatments, silicide division, and basic principles of electron beam. The experimental part contains a description of used experimental methods for evaluation of samples, creation of Ni-Si coating using electroplating, and the parameters of electron beam used for melting the sample coating. The last part is devoted to structural evaluation of the sample coating and its microhardness.
Influence of Si surface passivation on growth and ordering of nanostructures
Matvija, Peter ; Kocán, Pavel (advisor) ; Rezek, Bohuslav (referee) ; de la Torre, Bruno (referee)
Silicon is currently the most widely used semiconductor material with applications ranging from solar cells and sensors to electronic devices. Surface functionalization of silicon with molecular monolayers can be used to tune properties of the material toward a desired application. However, site-specific adsorption of molecules or molecular patterning on silicon surfaces is a difficult task due to the high reactivity of silicon. In this work, we use scanning tunneling microscopy, ab-initio calculations and kinetic Monte Carlo simulations to study adsorption of organic molecules on a bare and thallium-passivated Si(111) surface. We show that the polarity of molecules has a large impact on bonding of the molecules with the bare surface. We demonstrate that, in comparison with the bare surface, molecules or single-atom adsorbates deposited on the Tl-passivated surface have significantly higher mobility. The increased mobility induces formation of 2D gases on the surface and enables formation of self-assembled molecular structures. We propose a novel method to directly visualize the 2D surface gases and we show that a phase of surface gases containing molecule-bound dipoles can be controlled by a non-homogeneous electric field. 1
Electrochemical etching of silicon
Vrzal, Pavel ; Voborný, Stanislav (referee) ; Šamořil, Tomáš (advisor)
The electrochemical etching is very used technique for semiconductor materials modification. Different structures which find applications in many fields (biotechnology, nanotechnology or electronics) can be prepared by this technique. The task of bachelor’s thesis was preparation of porous silicon using electrochemical etching. At first, a study dedicated to porous Si was carried out. Experimental part of this work deals with a design of etching cell which was used for preparation of porous silicon by electrochemical etching. In addition, the porous Si was prepared by metal assisted chemical etching. Subsequently, created structures were analyzed by scanning electron microscopy. Photoluminescence properties of porous silicon were studied as well.
Optical properties of silicon nanostructures for photovoltaics
Salava, Jan
Název práce: Optické vlastnosti křemíkových nanostruktur pro fotovoltaiku Autor: Bc. Jan Salava Katedra: Katedra chemické fyziky a optiky Vedoucí diplomové práce: doc. RNDr. František Trojánek, Ph.D., katedra chemické fyziky a optiky Abstrakt: V předložené práci jsou studovány křemíkové nanokrystaly umístěné v SiC matrici - jednotlivé vzorky se odlišují přidáním dopantu (boru) do příslušné vrstvy struktury během depozice metodou PECVD a pasivací vodíkem. Křemíkové nanokrystaly jsou významné zejména tím, že oproti své objemové verzi vykazují účinnou fotoluminiscenci a absorpci ve viditelné oblasti spektra. Změnami parametr· při přípravě lze ladit jejich vlastnosti s ohledem na konkrétní aplikaci. Základní myšlenka integrace křemíkových nanostruktur do solárních článk· spočívá ve zvýšení účinnosti konverze slunečního spektra kombinací několika tenkých vrstev s nanokrystaly a objemového Si článku tak, aby každá vrstva sluneční cely absorbo- vala určitou část spektra. Procesy, které se v těchto strukturách dějí krátce po excitaci nosič· náboje, však stále nejsou zcela popsány. Cílem práce je charakterizace těchto jev· metodami ča- sově rozlišené spektroskopie. Dalším úkolem je popsat vliv dopování jednotlivých částí materiálu a jeho pasivace ve vodíkové atmosféře na chování fotoexcitovaných nosič· a intenzitu...

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