National Repository of Grey Literature 13 records found  1 - 10next  jump to record: Search took 0.01 seconds. 
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.
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
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
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
Strategic analysis of ČEZ Distribuce, a.s.
Vaniš, Jan ; Machek, Ondřej (advisor) ; Boukal, Petr (referee)
The goal of this Bachelor's Thesis is to conduct a strategic analysis of ČEZ Distribuce, a.s., which is part of the biggest Czech energy group. It provides the reader with detailed information about the power distribution company itself as well as the Czech power distribution sector from the point of view of an external analyst. The thesis is divided into two parts: theoretical and practical. The first part gives information about the fundamental terms and mechanisms needed for the analysis itself. The focus is on definition of corporate strategy, analysis of micro and macro environments, economic analysis and summarizing SPACE and SWOT analyses. The second part aims to apply the above mentioned analytical methods to the particular case of ČEZ Distribuce, a.s. and the power distribution sector. It clarifies the main principles, barriers and trends in the power distribution sector in the Czech Republic. Additionally, the thesis stresses comparison with rest of the competitors performing on the Czech market (especially in the economic analysis part).
Graphite/n-InP Schottky barrier with electrophoretically deposited Pt nanoparticles for hydrogen and nitrogen-monoxide detection
Žďánský, Karel ; Vaniš, Jan ; Černohorský, Ondřej ; Kacerovský, Pavel ; Fojtík, A.
N-type InP was deposited with Pt nanoparticles (NPs) by electrophoresis. The Pt NPs density was varied from a tenth of monolayer to several monolayers. Schottky contacts were made by colloidal graphite on the InP wafer site covered with Pt NPs. It was observed that H2 was detected by an increase of the current while NO was detected by its decrease. For explanation, we discuss mechanism which involves negative charging of adsorbed H atoms with electrons by increasing affinity level due to correlation efects
Fulltext: content.csg - Download fulltextPDF
Plný tet: UFE 0387602 - Download fulltextPDF
Microscopy of nanoparticles and films with nanoparticles
Kacerovský, Pavel ; Žďánský, Karel ; Procházková, Olga ; Vaniš, Jan ; Grym, Jan ; Vasiliev, A. ; Pašajev, E. M.
To study the electrophoreticaly deposited nanolayers of reverse micelles with Pd nano-particles on n-type InP substrates a wide range of current microscopic methods has been used. What concerns analytical methods the X-ray diffraction and mass spectrometry SIMS were used. The most relevant results about Pd nanoparticles in the layer were obtained by using HRTEM microscopy and SIMS spectrometry. In nanolayers crystallographic arrangement of Pd nanoparticles has not been found.
Measurement of electrical and mechanical oscillations of yeast cells membrane in acoustic frequency range
Jelínek, František ; Pokorný, Jiří ; Vaniš, Jan ; Hašek, Jiří ; Šimša, Jan
The paper describes the measurement of electric activity of yeast cells at frequencies around 1 kHz and of mechanical vibrations of cell membrane. Synchronized and non-synchronized tubulin mutants of yeast cells were measured. The paper includes a description of the laboratory equipment with a platinum wire point sensor and a spectrum analyzer. Obtained results are in good agreement with AFM findings.
Preliminary balistic electron emission microscopy/spectroscopy characterization of InAs quantum dots in AlGaAs/GaAs heterostructure
Vaniš, Jan ; Henini, M. ; Šroubek, Filip ; Walachová, Jarmila
We presented a characterization of InAs self assembled quantum dots embedded in quantum well of the AlGaAs/GaAs heterostructure using ballistic electron emission microscopy/spectroscopy BEEM/BEES. Structures are grown by MBE. Results of spectroscopic measurements "on the dot" and "out of the dot" are also presented.
Modification of Bi.sub.2./sub.Te.sub.3./sub. nanolayers
Zeipl, Radek ; Pavelka, Martin ; Jelínek, Miroslav ; Vaniš, Jan ; Šroubek, Filip ; Walachová, Jarmila
Our Bi.sub.2./sub.Te.sub.3./sub. nanolayers were prepared by laser ablation. If we use different depositon condition, prepared layers will have different properties, exactly with rising temperature of substrate during deposition laeyrs becoming smoother. We present STM picture of 60nm thick Bi.sub.2./sub.Te.sub.3./sub. prepared on substrate with temperature during deposition of 400.sup.0.sup.C. We also present modification of layer after many scans were realized by STM on the same place.

National Repository of Grey Literature : 13 records found   1 - 10next  jump to record:
See also: similar author names
1 Vaniš, J.
2 Vaniš, Jakub
2 Vániš, Jiří
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