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Effect of EU doping on the optical properties of ZnO nanorods prepared by chemical bath deposition
Yatskiv, Roman ; Bašinová, Nikola ; Grym, Jan ; Vaniš, Jan
We report on the properties of Eu-doped ZnO nanorods prepared by chemical bath deposition from aqueous solutions in an autoclave. The autoclave enables to grow the nanorods above the boiling point of water. The nanorods were characterized by scanning electron microscopy, secondary ion mass spectroscopy, and low temperature photoluminescence spectroscopy. Under the UV light excitation, the nanorods show a strong blue emission at 450 nm, which is associated with the 4f(6)5d - 4f(4) transitions of Eu2+ ions. We discuss the mechanisms responsible for the blue luminescence. We further clarify how the growth parameters affect the morphology and the optical properties of the nanorods. Growth temperatures above the boiling point of water significantly influence the intensity ratio of the near band edge emission to the deep level emission and greatly enhance optical quality of the nanorods.
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Optoelectrical characterization of well oriented n-type zno nanorod arrays on p-type GaN templates
Yatskiv, Roman ; Grym, Jan ; Schenk, Antonín ; Vaniš, Jan ; Roesel, David ; Chlupová, Šárka
A heterojunction formed between a single n-type ZnO nanorod and p-type GaN template was successfully prepared by low cost chemical bath deposition technique. Periodic circular patterns were fabricated by focused ion beam etching through poly(methyl methacrylate) mask to control the size, position, and periodicity of the ZnO nanorods. A possible growth mechanism is introduced to explain the growth process of the nanorods. Optical and electrical properties of the heterojunctions were investigated by low temperature photoluminescence spectroscopy and by the measurement of current-voltage (I-V) characteristics. The I-V characteristics were measured by directly contacting single ZnO nanorods with the conductive atomic force microscopy tip. The diode-like rectifying behavior was observed with a turn-on voltage of 2.3 V and the reverse breakdown voltage was 5 V
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Electrical properties of nanoscale heterojunctions formed between GaN and ZnO nanorods
Tiagulskyi, Stanislav ; Yatskiv, Roman ; Grym, Jan ; Schenk, Antonín ; Roesel, David ; Vaniš, Jan ; Hamplová, Marie
Vertical periodic arrays of ZnO nanorods are prepared by hydrothermal growth on GaN templates patterned by focused ion beam. Electro-physical properties of a single vertically-oriented ZnO nanorod are investigated by measuring the current-voltage characteristics using a nanoprobe in a scanning electron microscope. This technique enables to observe the surface morphology of ZnO nanorods simultaneously with their electrical characterization in vacuum. The vacuum chamber rejects the impact of gas adsorption and light irradiation, which both affect the properties of ZnO nanorods. Moreover, mechanical damage and strain induced during the nanorod transfer are eliminated. Nonlinear current-voltage characteristics under the forward bias are explained by the tunneling-recombination process and by the space charge limited current. The high reverse bias current in the p-n heterojunction is attributed to direct tunneling via a narrow tunnel barrier
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Scanning thermal microscopy of thermoelectric pulsed laser deposited nanostructures
Vaniš, Jan ; Zelinka, Jiří ; Zeipl, Radek ; Jelínek, Miroslav ; Kocourek, Tomáš ; Remsa, Jan ; Navrátil, Jiří
New materials with high possible figure of merit ZT are of high interest as a promising candidates for thermoelectric applications such as energy harvesting. Miniaturization of such systems tends toward developing of the suitable characterization method with nanometer resolution ability. In our contribution, we present the development and experimental results of a simple scanning probe microscopy method for the relative thermal conductivity characterization. The possibility of the setup is demonstrated on the set of different thin thermoelectric layers grown from hot pressed targets by pulsed laser deposition on the reference Si substrate. All the measurements were performed on the commercial Veeco Multimode scanning AFM/STM microscope with home developed controller and by using PicoCal Inc. bolometer probes with tungsten resistive path. All the experiments were done in the air at the ambient condition. Additional sample treatment for the measurement will be also briefly described
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Strategická analýza společnosti ČEZ Distribuce, a.s.
Vaniš, Jan ; Machek, Ondřej (vedoucí práce) ; Boukal, Petr (oponent)
Tato bakalářská práce se zabývá analýzou společnosti ČEZ Distribuce, a.s., působící na českém distribučním trhu s elektrickou energií ve strategické rovině s cílem poskytnou čtenáři komplexní informace nejen o analyzované společnosti, ale i o odvětví samotném pohledem externího analytika. Práce je rozdělena na dva celky, část teoretickou a praktickou. V teoretické části jsou popsány základní pojmy a informace potřebné k analýze samotné. Důraz je kladen na části věnující se definování firemní strategie, mikro i makrookolí společnosti, ekonomické analýze zahrnující analýzu finanční a analýzu naturálních ukazatelů a v neposlední řadě na souhrnnou SPACE a SWOT analýzu. Praktická část je zaměřena již na aplikaci těchto analytických nástrojů na vybranou společnost a odvětví. Tato část práce má za úkol čtenáři osvětlit základní principy, bariéry či trendy ve zkoumané části ekonomiky. Krom toho je v praktické části (zejména v ekonomické analýze) kladen důraz na srovnání s ostatními dvěma distributory elektrické energie působícími na českém trhu.
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