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Materiály pro sluneční články založené na tenkých vrstvách křemíku
Fekete, Ladislav
Thin lm microcrystalline silicon is the most promising materiál for large area PN junction solar cells. As microcrystalline silicon is a heterogenous material composed of two phases (amorphous silicon tissue from which crystalline grains of micrometric dimension grow). The Raman spectra are commonly used to determine the crystallinity of mixed phase silicon thin lms by analyzing the contributions of amorphous and crystalline phase to TO phonon band. Many dierent empirical or semi-empirical methods of evaluating crystallinity from the Raman spectra exist. In this master's thesis the microcrystalline Raman spectra were studied and a better way of evaluating crystallinity was searched for. The decomposition of the microcrystalline spectra of the series of the samples, where a single deposition parameter was changing,by tting them with Gaussian bands was performed. We also report on the development of a special software for the band decomposition by non-linear least-squares tting based on Marquardt-Levenberg algorithm and demonstrate its use for a series of lms with structure changing from amorphous to fully microcrystalline.
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Potential-driven On/Off Switch Strategy for the Electrosynthesis of [7]Helicene-derived Polymers.
Žádný, Jaroslav ; Storch, Jan ; Strašák, Tomáš ; Církva, Vladimír ; Hrbáč, J. ; Fekete, Ladislav ; Pokorný, Jan ; Bulíř, Jiří ; Vacek, J.
3-([7]H elicen-9-yl)-thiophene hybrid monomer was electrooxidized in acetonitrile by cyclic voltammetry with anodic potential limits of +1.5 V or +2.5 V, resulting in a conductive and non-conductive polymer, respectively. The electrochemical findings were supplemented by microscopy investigations; UV-Vis, fluorescence and vibrational spectroscopies, ellipsometry measurements and computational chemistry. The electrodeposited polymers could be used for the further development of materials applicable in organic electronics and sensing technologies.
Plný tet: SKMBT_C22017111612582 -  PDF
Plný text: content.csg - PDF
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Materiály pro sluneční články založené na tenkých vrstvách křemíku
Fekete, Ladislav
Thin lm microcrystalline silicon is the most promising materiál for large area PN junction solar cells. As microcrystalline silicon is a heterogenous material composed of two phases (amorphous silicon tissue from which crystalline grains of micrometric dimension grow). The Raman spectra are commonly used to determine the crystallinity of mixed phase silicon thin lms by analyzing the contributions of amorphous and crystalline phase to TO phonon band. Many dierent empirical or semi-empirical methods of evaluating crystallinity from the Raman spectra exist. In this master's thesis the microcrystalline Raman spectra were studied and a better way of evaluating crystallinity was searched for. The decomposition of the microcrystalline spectra of the series of the samples, where a single deposition parameter was changing,by tting them with Gaussian bands was performed. We also report on the development of a special software for the band decomposition by non-linear least-squares tting based on Marquardt-Levenberg algorithm and demonstrate its use for a series of lms with structure changing from amorphous to fully microcrystalline.
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(100) substrate processing optimization for fabrication of smooth boron doped epitaxial diamond layer by PE CVD
Mortet, Vincent ; Fekete, Ladislav ; Ashcheulov, Petr ; Taylor, Andrew ; Hubík, Pavel ; Trémouilles, D. ; Bedel-Pereira, E.
Boron doped diamond layers were grown in an SEKI AX5010 microwave plasma enhanced chemical vapour deposition system. Effect of surface preparation, i.e. polishing and O2/H2 plasma etching on epitaxial growth on type Ib (100) HPHT synthetic diamonds were investigated. Using optimized substrate preparation, smooth (RRMS ~ 1 nm) boron doped diamond layers with metallic conduction and free of un-epitaxial crystallites were grown with a relatively high growth rate of 3.7 μm/h. Diamond were characterized by optical microscopy, optical profilometry, atomic force microscopy and Hall effect.
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Production of nitrogen vacancy centers in nanocrystalline diamond thin film for quantum biosensing applications
Jakl Krečmarová, Marie ; Gulka, Michal ; Fekete, Ladislav ; Remeš, Zdeněk ; Petráková, Vladimíra ; Mortet, Vincent ; Nesládek, M.
Due to its excellent properties such as chemical stability and biocompatibility, diamond is an ideal material for bio sensing application. In particular, nitrogen vacancy (NV) centres in diamond are promising candidates for optical bio-sensing application in nanodiamond particles and single crystal diamond by irradiation (electron, proton, neutron, particles) followed by annealing has been recently developer. Production of NV centres in CVD diamond thin film is important for fabrication of new bio sensor.
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Nanodiamond seeding of rough substrates
Vlčková, M. ; Stefanovič, M. ; Petrák, V. ; Fendrych, František ; Taylor, Andrew ; Fekete, Ladislav ; Nesládek, M.
Efficient growth of nanocrystalline diamond (NCD) requires nucleation enhancement before chemical vapour deposition step. Nanodiamond (ND) seeding is a commonly used technique that yields high nucleation densities. This technique is well established for conventional planar substrates with low surface roughness. However, many engineering application requires NCD grow on rough and/or non-planar substrates. In this work, we investigate quality of nanodiamond seeding on silicon substrates of high surface roughness (RMS roughness <1 mm). Seeded substrates and deposited diamond films were analysed by atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman spectroscopy. We discuss influence of nanodiamond particles in seeding solution and seeding technique on nucleation density and quality of deposited NCD film.
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