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The peculiar outburst activity of the symbiotic binary AG Draconis
Gális, R.; Merc, J.; Leedjärv, L.; Vrašťák, M.; Karpov, Sergey
2019 - anglický
AG Draconis is a strongly interacting binary system which manifests characteristic symbiotic activity of alternating quiescent and active stages. The latter ones consist of the series of individual outbursts repeating at about a one-year interval. After seven years of flat quiescence following the 2006–2008 major outbursts, in the late spring of 2015, the symbiotic system AG Dra started to become brighter again toward what appeared to be a new minor outburst. The current outburst activity of AG Dra was confirmed by the following three outbursts in April 2016, May 2017 and April 2018. The photometric and spectroscopic observations suggest that all these outbursts are of the hot type. Such behaviour is considerably peculiar in almost 130-year history of observing of this object, because the major outbursts at the beginning of active stages are typically cool ones. In the present work, the current peculiar activity of the symbiotic binary AG Dra is described in detail.\n
Klíčová slova:
AG Draconis; LC; outburst
Dokument je dostupný na externích webových stránkách.
The peculiar outburst activity of the symbiotic binary AG Draconis
AG Draconis is a strongly interacting binary system which manifests characteristic symbiotic activity of alternating quiescent and active stages. The latter ones consist of the series of individual ...
Model of carrier multiplication due to impurity impact ionization in boron-doped diamond
Mortet, Vincent; Lambert, Nicolas; Hubík, Pavel; Soltani, A.
2019 - anglický
Boron-doped diamond exhibits a characteristic S-shaped I-V curve at room temperature [1] with two electrical conductivity states, i.e., low and high conductivity, at high electric fields (50 – 250 kV.cm-1) due to the carrier freeze-out and impurity impact ionization avalanche effect. To our knowledge, the carrier multiplication during the change of the conductivity state has not been studied. In this article, we investigate theoretically the effect of acceptor concentration and compensation level on the carrier multiplication coefficient at room temperature to determine the optimal dopants concentration of maximum carrier multiplication. The room temperature hole concentration of boron-doped diamond has been calculated for various acceptor concentration and compensation ratio by solving numerically the charge neutrality equation within the Boltzmann approximation of the Fermi-Dirac statistic.\n
Klíčová slova:
Boron-doped diamond; semiconductor; carrier multiplication coefficient; impurity impact ionization
Dokument je dostupný na externích webových stránkách.
Model of carrier multiplication due to impurity impact ionization in boron-doped diamond
Boron-doped diamond exhibits a characteristic S-shaped I-V curve at room temperature [1] with two electrical conductivity states, i.e., low and high conductivity, at high electric fields (50 – 250 ...
Germanium and tin nanoparticles encapsulated in amorphous silicon matrix for optoelectronic application
Stuchlíková, The-Ha; Remeš, Zdeněk; Stuchlík, Jiří
2019 - anglický
The plasma enhanced chemical vapour deposition was combined with in situ deposition of Ge and Sn thin film by evaporation technique at surface temperature about 220 °C to form nanoparticles on the surface of hydrogenated silicon thin films to prepare diodes. Formation of nanoparticles was additionally stimulated by plasma treatment through a low pressure hydrogen glow discharge. The diodes based on PIN diode structures with and without the embedded Ge or Sn nanoparticles were characterized by temperature dependence of electrical conductivity, activation energy of conductivity, measurement of volt-ampere characteristics in dark and under solar illumination\n
Klíčová slova:
Ge NPs; a-Si:H; Sn NPs; diode structures; I-V characteristics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Germanium and tin nanoparticles encapsulated in amorphous silicon matrix for optoelectronic application
The plasma enhanced chemical vapour deposition was combined with in situ deposition of Ge and Sn thin film by evaporation technique at surface temperature about 220 °C to form nanoparticles on the ...
ZnMg0.8Ca/Sr0.2 ternary alloys - the influence of the third element on material properties
Čapek, Jaroslav; Pinc, Jan; Kubásek, J.; Molnárová, Orsolya; Maňák, Jan; Drahokoupil, Jan
2019 - anglický
Zinc-based materials alloyed with the elements of the 2nd group of the periodic table have been studied as potential materials for the fabrication of various biodegradable implants. In this study, we prepared two ternary alloys: ZnMg0.8Ca0.2 (wt.%) and ZnMg0.8Sr0.2. The microstructure of both ternary alloys was similar, the main difference was in the size and morphology of the Ca/SrZn13 phase. The SrZn13 phase formed fine particles with a submicron size and had more significant hardening effect in the as-cast state compared to the CaZn13 phase. The annealing led to a transformation of the eutectic structure into the “massive” Mg2Zn11 phase which caused a significant increase of both hardness and compressive yield stress. In the annealed states, comparable hardness was observed for both alloys and higher compressive yield strength for the Ca-containing alloy.
Klíčová slova:
biodegradable zinc alloys; mechanical properties; microstructure
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
ZnMg0.8Ca/Sr0.2 ternary alloys - the influence of the third element on material properties
Zinc-based materials alloyed with the elements of the 2nd group of the periodic table have been studied as potential materials for the fabrication of various biodegradable implants. In this study, we ...
Book of Abstracts of the 28th Joint Seminar "Development of Materials Science in Research and Education"
Kožíšek, Zdeněk; Král, Robert; Zemenová, Petra
2018 - anglický
Topics:\n- Trends in development of materials research \n- Education of materials science at the universities\n- Information about the research programmes of individual institutions \n- Information on equipment for preparation and characterisation of materials \n- Results of materials science research
Klíčová slova:
material sciences
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Book of Abstracts of the 28th Joint Seminar "Development of Materials Science in Research and Education"
Topics:\n- Trends in development of materials research \n- Education of materials science at the universities\n- Information about the research programmes of individual institutions \n- Information on ...
The hydrogen plasma doping of ZnO thin films and nanoparticles
Remeš, Zdeněk; Neykova, Neda; Potocký, Štěpán; Chang, Yu-Ying; Hsu, H.S.
2018 - anglický
The optical absorptance and photoluminescence studies has been applied on the hydrogen and oxygen plasma treated, nominally undoped ZnO thin films and aligned nanocolumns grown on the nucleated glass substrate by the hydrothermal process in an oil bath containing a flask with ZnO nutrient solution. The localized defect states at 2.3 eV below the optical absorption edge were detected by photothermal deflection spectroscopy (PDS) in a broad spectral range from near UV to near IR. The optical absorptance spectroscopy shows that hydrogen doping increases free electron concentration changing ZnO to be electrically conductive (hydrogen doping).\n
Klíčová slova:
ZnO; nanoparticles; hydrothermal growth; hotoluminescence spectroscopy; PDS
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The hydrogen plasma doping of ZnO thin films and nanoparticles
The optical absorptance and photoluminescence studies has been applied on the hydrogen and oxygen plasma treated, nominally undoped ZnO thin films and aligned nanocolumns grown on the nucleated glass ...
Influence of Si doping in different layers on luminescence properties of InGaN/GaN multiple quantum well structure
Hájek, František; Hospodková, Alice; Oswald, Jiří; Slavická Zíková, Markéta
2018 - anglický
Luminescence of InGaN/GaN multiple quantum well (MQW) structure is strongly affected by spontaneous and piezoelectric polarizations. To suppress them, doping with shallow impurities (e. g. Si) can be used. This works presents the effects of Si doping in different layers around the MQW area. On the basis of photoluminescence and cathodoluminescence measurements and band structure simulation, the piezoelectric field is most efficiently reduced when both layers under and over MQW area are Si doped.\n
Klíčová slova:
nitrides; quantum wells; luminescence; semiconductor doping
Dokument je dostupný na externích webových stránkách.
Influence of Si doping in different layers on luminescence properties of InGaN/GaN multiple quantum well structure
Luminescence of InGaN/GaN multiple quantum well (MQW) structure is strongly affected by spontaneous and piezoelectric polarizations. To suppress them, doping with shallow impurities (e. g. Si) can be ...
XXIII Czech-Polish seminar: Structural and ferroelectric phase transitions
Hlinka, Jiří; Pokorný, Jan; Bubnov, Alexej
2018 - anglický
This is the Book of Abstracts for the XXIII Czech-Polish Seminar (CPSEM-2018 conference) held in Kouty on May 21 - 25, 2018. The special objective of the conference is expressed in the conference subtitle: Structural and Ferroelectric Phase Transitions. The continuous worldwide interest to this conference series is proving that it has a respected position within the series of International/European conferences covering all interdisciplinary field of the research related to structural and ferroelectric phase transitions. At the CPSEM-2018 conference more than 110 participants from 14 countries all over the world presented 16 invited lectures and selected 36 oral contributions. About 60 posters were presented during two poster sessions.
Klíčová slova:
ferroelectric phase transitions; structural
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
XXIII Czech-Polish seminar: Structural and ferroelectric phase transitions
This is the Book of Abstracts for the XXIII Czech-Polish Seminar (CPSEM-2018 conference) held in Kouty on May 21 - 25, 2018. The special objective of the conference is expressed in the conference ...
Modeling of monocrystalline magnesium microbeam bending
Němeček, J.; Maňák, Jan; Němeček, J.
2018 - anglický
This paper presents a numerical simulation of a micro-scale experiment on a magnesium alloy. Three dimensional numerical FE model with elastoplastic behavior respecting crystal anisotropy was used to fit experimental load displacement curves.
Klíčová slova:
magnesium; microbeams; crystal anisotropy; FE model
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Modeling of monocrystalline magnesium microbeam bending
This paper presents a numerical simulation of a micro-scale experiment on a magnesium alloy. Three dimensional numerical FE model with elastoplastic behavior respecting crystal anisotropy was used to ...
Characterization of hydrogenated silicon thin films and diode structures with integrated germanium nanoparticles
Stuchlík, Jiří; Fajgar, Radek; Kupčík, Jaroslav; Remeš, Zdeněk; Stuchlíková, The-Ha
2018 - anglický
Substrates with ZnO (or ITO) conductive layers were covered by thin film of a-Si:H deposited by PECVD technique. Under a turbo-molecular vacuum (10-4 Pa) the reactive laser ablation (RLA) was used to cover this a-Si:H thin film by germanium NPs. The RLA was performed using focused excimer ArF laser beam (193 nm, 100 mJ/pulse) under SiH4 background atmosphere (0.5 Pa). As a target the elemental germanium was used. Reaction between ablated Ge and silane led to formation of Ge NPs covered by thin SiGe layer. Then the deposited NPs were covered and stabilized by a-Si:H layer by PECVD. Those two deposition processes was alternated and applied a few times. The Si:H thin films with integrated Ge NPs were characterized by microscopic, spectroscopic and diffraction techniques. I-V characteristics of final diode structures without and under illumination were measured as well as their electroluminescence behaviour.
Klíčová slova:
PECVD; a-Si:H diode structures; Ge; nanoparticles
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Characterization of hydrogenated silicon thin films and diode structures with integrated germanium nanoparticles
Substrates with ZnO (or ITO) conductive layers were covered by thin film of a-Si:H deposited by PECVD technique. Under a turbo-molecular vacuum (10-4 Pa) the reactive laser ablation (RLA) was used to ...
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