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Relation between optical and microscopic properties of hydrogenated silicon thin films with integrated germanium and tin nanoparticles
Stuchlík, Jiří; Stuchlíková, The-Ha; Čermák, Jan; Kupčík, Jaroslav; Fajgar, Radek; Remeš, Zdeněk
2019 - anglický
The hydrogenated amorphous silicon layers (a-Si:H) were deposited by PECVD method on quartz substrates. During interruption of PECVD process the vacuum chamber was pumped up to 10-5 Pa and 1 nm thin films of Germanium or Tin were evaporated on the surface. The materials form isolated nanoparticles (NPs) on the a-Si:H surface. Then the deposited NPs were covered and stabilized by a-Si:H layer by PECVD. Those two deposition processes were alternated 5 times. The a-Si:H thin films with integrated Ge or Sn NPs were characterized optically by PDS and CPM methods, and microscopically by SEM and AFM microscopies. Optical and microscopic properties of the structures are correlated and discussed considering their application in photovoltaics.\n
Klíčová slova:
thin films; a-Si:H; nanoparticles; germanium; tin
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Relation between optical and microscopic properties of hydrogenated silicon thin films with integrated germanium and tin nanoparticles
The hydrogenated amorphous silicon layers (a-Si:H) were deposited by PECVD method on quartz substrates. During interruption of PECVD process the vacuum chamber was pumped up to 10-5 Pa and 1 nm thin ...
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 ...
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 ...
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 ...
Controlled structuring of self–assembled polystyrene microsphere arrays by two different plasma systems
Domonkos, Mária; Ižák, Tibor; Štolcová, L.; Proška, J.; Kromka, Alexander
2013 - anglický
In this study we present a successful manipulation of microspheres by reactive ion etching (RIE). A self-assembled monolayer close-packed array of monodisperse polystyrene microspheres (PM) with diameter of 471 nm was used as the primary template. The PM templates were processed in two different RIE systems: (i) capacitively coupled radiofrequency plasma (CCP) and (ii) dual plasma system which combines CCP and pulsed linear-antenna microwave plasma (PLAMWP). The influence of process conditions on the PM geometry was systematically studied by scanning electron microscopy (SEM). The process conditions were controlled by varying radiofrequency (RF) power, gas mixture (O2:CF4 ratio) and process duration.
Klíčová slova:
nanosphere lithography; reactive ion etching; pulsed linear-antenna microwave plasma; polystyrene microspheres; Langmuir-Blodgett monolayers
Dokument je dostupný na externích webových stránkách.
Controlled structuring of self–assembled polystyrene microsphere arrays by two different plasma systems
In this study we present a successful manipulation of microspheres by reactive ion etching (RIE). A self-assembled monolayer close-packed array of monodisperse polystyrene microspheres (PM) with ...
Volumic dependence of nucleation barrier at critical supersaturation
Kožíšek, Zdeněk; Demo, Pavel; Sveshnikov, Alexey
2010 - anglický
Kinetic equations of nucleation are solved numerically to found conditions, under which first nuclei are formed. Critical supercooling is determined from the size distribution of nuclei. It is shown that nucleation barrier at critical supercooling depends logarithmically on droplet volume.
Klíčová slova:
nucleation; critical supersaturation; nucleation barrier
Dokument je dostupný na externích webových stránkách.
Volumic dependence of nucleation barrier at critical supersaturation
Kinetic equations of nucleation are solved numerically to found conditions, under which first nuclei are formed. Critical supercooling is determined from the size distribution of nuclei. It is shown ...
Equilibrium shape of a liquid nucleus on a highly curved surface of a nanofiber
Sveshnikov, Alexey; Demo, Pavel; Kožíšek, Zdeněk
2010 - anglický
Approximate equilibrium shape of a liquid nucleus on a nanofiber was determined by minimalization of its free energy under condition of the constant volume of the nucleus. The nucleus is stretched in the direction parallel to the nanofiber axis. The deviation of the shape from a sphere is larger for well-wetting cases.
Klíčová slova:
nucleus shape; highly curved surface; nanofibers
Dokument je dostupný na externích webových stránkách.
Equilibrium shape of a liquid nucleus on a highly curved surface of a nanofiber
Approximate equilibrium shape of a liquid nucleus on a nanofiber was determined by minimalization of its free energy under condition of the constant volume of the nucleus. The nucleus is stretched in ...
Testování oduhličené vrstvy oceli metodou Barkhausenova šumu
Stupakov, Oleksandr; Tomáš, Ivan; Skrbek, L.
2010 - český
Průmyslově nežádoucí proces oduhličení povrchové vrstvy běžné pružinové oceli ČSN 414260 (EN 54SiCr6) byl simulován žíháním na vzduchu při teplotě 800oC s různým časem výdrže v peci. Byly připraveny tři série vzorků s různě ošetřeným povrchem: (i) bez povrchové úpravy (s okujemi oxidů železa), (ii) s mořením v kyselině chlorovodíkové a (iii) s povrchem otryskaným pískem. Získané povrchové oduhličené vrstvy s tloušťkou v rozmezí 0,1-0,35 mm byly zkoumány optickým mikroskopem, vlnovým disperzním spektrometrem a metodou povrchové rentgenové difrakce. Magnetic Barkhausen noise technique was tested for applicability of non-destructive charaterization of the decarburized layer depth. A newly introduced parameter, Barkhausen noise coercivity, was proposed for practical use due to its sensitivity to the tested decarburization and its stability to the measurement conditions.
Klíčová slova:
magnetic Barkhausen noise; surface magnetic field; surface decarburization; carbon steel; magnetic non-destructive testing
Dokument je dostupný na externích webových stránkách.
Testování oduhličené vrstvy oceli metodou Barkhausenova šumu
Průmyslově nežádoucí proces oduhličení povrchové vrstvy běžné pružinové oceli ČSN 414260 (EN 54SiCr6) byl simulován žíháním na vzduchu při teplotě 800oC s různým časem výdrže v peci. Byly připraveny ...
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