Number of found documents: 558
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Nanostructured layer enhancing light extraction from GaN-based scintillator using MOVPE
Vaněk, Tomáš; Hubáček, Tomáš; Hájek, František; Dominec, Filip; Pangrác, Jiří; Kuldová, Karla; Oswald, Jiří; Hospodková, Alice
2021 - English
Light extraction (LE) efficiency of GaN buffer layer was studied by angle-resolved photoluminescence. We measured enhancement of light extraction efficiency (LEE) up to 154% by introducing the SiNx layer atop the GaN buffer and subsequent GaN light extraction layer (LEL) overgrowth. Morphological properties of GaN. Keywords: MOVPE; GaN; light extraction; SiNx; scintillator Available at various institutes of the ASCR
Nanostructured layer enhancing light extraction from GaN-based scintillator using MOVPE

Light extraction (LE) efficiency of GaN buffer layer was studied by angle-resolved photoluminescence. We measured enhancement of light extraction efficiency (LEE) up to 154% by introducing the SiNx ...

Vaněk, Tomáš; Hubáček, Tomáš; Hájek, František; Dominec, Filip; Pangrác, Jiří; Kuldová, Karla; Oswald, Jiří; Hospodková, Alice
Fyzikální ústav, 2021

Plasma hydrogenation of hydrothermally grown ZnO micropods
Remeš, Zdeněk; Aubrechtová Dragounová, Kateřina; Mičová, J.
2021 - English
The hydrothermally grown ZnO micropods have been placed on grounded stainless-steel holder and exposed to an inductively coupled plasma (ICP) monitored in-situ by optical emission spectroscopy (OES). OES shows the immediate release of oxygen during Ar ion bombardment. The prolonged exposure to hydrogen plasma leads to deterioration of the optical properties as well. The exposure, rf power and hydrogen pressure have been optimized to enhance UV-photoluminescence peak at the wavelength 384 nm related to surface bounded excitons and reduce the defect-related photoluminescence in red spectral range. The strong UV photoluminescence appears just after 1 minute of plasma hydrogenation in a radio frequency plasma discharge with power density 40 W/dm3 and hydrogen pressure 17 Pa. Keywords: ZnO; micropods; inductively coupled plasma; optical emission spectroscopy; photoluminescence spectroscopy; Raman spectroscopy; infrared absorption spectroscopy Available at various institutes of the ASCR
Plasma hydrogenation of hydrothermally grown ZnO micropods

The hydrothermally grown ZnO micropods have been placed on grounded stainless-steel holder and exposed to an inductively coupled plasma (ICP) monitored in-situ by optical emission spectroscopy (OES). ...

Remeš, Zdeněk; Aubrechtová Dragounová, Kateřina; Mičová, J.
Fyzikální ústav, 2021

Growth and properties of diamond films prepared on 4-inch substrates by cavity plasma systems
Babčenko, Oleg; Potocký, Štěpán; Aubrechtová Dragounová, Kateřina; Szabó, Ondrej; Bergonzo, P.; Rezek, B.; Kromka, Alexander
2021 - English
We compare two microwave (2.45 GHz) plasma systems with ellipsoidal and multimode clamshell cavity for diamond synthesis by chemical vapor deposition. We use H2/CH4/CO2 gas mixture for diamond film deposition on Si <100> wafers. Both systems are capable of high pressure (up to 20 kPa) operation and high growth rates (several µm/h). We compare the cavity systems from the point of diamond quality (Raman shift measurement), substrate size (2” versus 4”) and grown film homogeneity together with surface morphology (SEM), deposition rate and parasitic doping levels (photoluminescence). Keywords: large area diamond; microwave cavity plasma; high-power density plasma Available at various institutes of the ASCR
Growth and properties of diamond films prepared on 4-inch substrates by cavity plasma systems

We compare two microwave (2.45 GHz) plasma systems with ellipsoidal and multimode clamshell cavity for diamond synthesis by chemical vapor deposition. We use H2/CH4/CO2 gas mixture for diamond film ...

Babčenko, Oleg; Potocký, Štěpán; Aubrechtová Dragounová, Kateřina; Szabó, Ondrej; Bergonzo, P.; Rezek, B.; Kromka, Alexander
Fyzikální ústav, 2021

Nanopowders of R.sub.2./sub.Fe.sub.14./sub.B-type compounds in high magnetic fields: The effects of substitutional and interstitial atoms on inter-sublattice exchange interaction
Paukov, M.; Ivanov, L.; Tereshina, I.; Tereshina-Chitrova, Evgenia; Gorbunov, D.; Andreev, A. V.; Pyatakov, A.P.; Granovsky, S.A.; Doerr, M.; Drulis, H.
2020 - English
The fundamental magnetic characteristics of R2Fe14B intermetallics are highly sensitive to atomic substitutions and interstitial absorption of light elements. In this work, both were combined, and the influence of the substitutions in the R-sublattice and hydrogen absorption on the magnetization of (RR’) 2Fe14BHx (R is Tm or Er, and R’ is Nd) in magnetic fields up to 58 T was studied. By using direct hydrogen absorption, (R0.5Nd0.5)2Fe14BHx compounds were obtained with hydrogen content 0≤x≤5.5. Magnetic measurements were carried out on nanopowders. The strength of the inter-sublattice coupling in (R0.5Nd0.5)2Fe14B and their hydrides is estimated by analysing high-field magnetization data. It is shown that hydrogenation weakens the inter-sublattice exchange interaction up to 45 %. Keywords: rare earth; intermetallics; powder metallurgy; magnetism in solids; hydride properties Available at various institutes of the ASCR
Nanopowders of R.sub.2./sub.Fe.sub.14./sub.B-type compounds in high magnetic fields: The effects of substitutional and interstitial atoms on inter-sublattice exchange interaction

The fundamental magnetic characteristics of R2Fe14B intermetallics are highly sensitive to atomic substitutions and interstitial absorption of light elements. In this work, both were combined, and the ...

Paukov, M.; Ivanov, L.; Tereshina, I.; Tereshina-Chitrova, Evgenia; Gorbunov, D.; Andreev, A. V.; Pyatakov, A.P.; Granovsky, S.A.; Doerr, M.; Drulis, H.
Fyzikální ústav, 2020

CrystalCMP: examples of use
Rohlíček, Jan
2020 - English
The program CrystalCMP can be used for comparison of crystal structures containing separated molecular objects as it is, for instance, in molecular crystals or some metal-organic compounds. The program can be useful in many different situations. This article shows the use of the program CrystalCMP on three basic exam ples for which the program was primarily intended. Keywords: molecular packing; comparison; similarity Available at various institutes of the ASCR
CrystalCMP: examples of use

The program CrystalCMP can be used for comparison of crystal structures containing separated molecular objects as it is, for instance, in molecular crystals or some metal-organic compounds. The ...

Rohlíček, Jan
Fyzikální ústav, 2020

Nanosecond laser damage of metallic mirrors
Muresan, Mihai-George; Pilná, Kateřina; Čech, Pavel; Mydlář, Martin; Vanda, Jan; Navrátil, Petr
2020 - English
Laser surface processing is an established method to introduce surface functionalities on solid surfaces with the required throughputs for a commercial process. Fabrication of laser induced surface structures in an effective matter is done by laser interaction studies, which reveal the best processing parameters (laser wavelength, fluence, repetition, together with the processing speed and environment). Customized solutions are providing the best yields and they are being implemented faster than ever. However, the optics manufacturers are not being to keep up the pace with the new requirements, so they turn instead on older, but safer technology. In order to get a better understanding of optics capabilities, thorough testing is required. Common laser metallic mirrors, commercially available, are being rigorously tested using a nanosecond Yb:YAG laser and the results are compared with the vendor’s information.\n Keywords: laser patterning; metallic mirrors; LIDT; nanosecond laser testing Available at various institutes of the ASCR
Nanosecond laser damage of metallic mirrors

Laser surface processing is an established method to introduce surface functionalities on solid surfaces with the required throughputs for a commercial process. Fabrication of laser induced surface ...

Muresan, Mihai-George; Pilná, Kateřina; Čech, Pavel; Mydlář, Martin; Vanda, Jan; Navrátil, Petr
Fyzikální ústav, 2020

Závěrečná zpráva projektu „Efektivní využití odpadního tepla“ reg. č. CZ.07.1.02/0.0/0.0/16_040/0000384 realizovaném v rámci výzvy č. 24 OP PPR , technologie 3, stacionární vysokopotenciální zdroje odpadního tepla
Hejtmánek, Jiří; Stachura, Jan
2020 - Czech
Cílem projektu bylo ověřit možnost využití termoelektrických generátorů (dále TEG) k výrobě elektrické energie z odpadního tepla, které je produkováno spalováním fosilního paliva v dopravních prostředcích. S ohledem na charakter jízdního cyklu prostředků veřejné dopravy jsme se na základě konzultací a prozkoumání možností experimentálního testování soustředili na ověření možnosti lepšího využití energie produkované nezávislým topením (NT) s cílem alespoň částečného pokrytí jeho potřeby elektrické energie, která je nutná k jeho provozu. Při provozu NT v autobuse dochází totiž k odběru elektrické energie cca 360 W z elektrické soustavy autobusu, která je potřeba pro pohon oběhového čerpadla, ventilátorů topení a řídící elektroniky NT.\n The aim of the project was to use the waste thermal energy of flue gases or hot steam to produce electricity through thermoelectric generators (TEG). The local production of electricity at the place of its consumption will enable, for example, power source of autonomous sensors, including wireless transmission of necessary information to the control center or power source of safety lights, without installation of the electric cables from the distant power source, which is sometimes technologically difficult. Another specific possible utilization was aimed at the replacement of disposable batteries, which supply the necessary sensors and at the same time serve for sending data to the control center, which is energy demanding.\n Keywords: využití odpadniho tepla; termoelektrická konverse Available at various institutes of the ASCR
Závěrečná zpráva projektu „Efektivní využití odpadního tepla“ reg. č. CZ.07.1.02/0.0/0.0/16_040/0000384 realizovaném v rámci výzvy č. 24 OP PPR , technologie 3, stacionární vysokopotenciální zdroje odpadního tepla

Cílem projektu bylo ověřit možnost využití termoelektrických generátorů (dále TEG) k výrobě elektrické energie z odpadního tepla, které je produkováno spalováním fosilního paliva v dopravních ...

Hejtmánek, Jiří; Stachura, Jan
Fyzikální ústav, 2020

Studium vlivu složení ve směsi CsCl-HfCl.sub.4./sub. na její tepelné vlastnosti v uzavřeném systému pomocí DSC analýzy
Král, Robert; Zemenová, Petra; Vaněček, Vojtěch; Bystřický, Aleš
2020 - Czech
Příspěvek se zabývá studiem tepelného chování směsi CsCl-HfCl4 o různém složení (nadbytek Cs- nebo Hf-složky) v uzavřeném systému (křemenné ampuli) pomocí neizotermní DSC analýzy. Ze získaných výsledků a jejich porovnáním s fázovým diagramem CsCl-HfCl4 bylo možné získat důležité informace potřebné k optimalizaci růstu krystalů Cs2HfCl6 vertikální Bridgmanovou metodou. This contribution deals with the study of thermal behavior of CsCl-HfCl4 mixture of various composition (containing excess of Cs- or Hf-component) in enclosed system (quartz ampoule) by non-isothermal DSC analysis. Important information necessary for optimization of the Cs2HfCl6 crystal growth by the vertical Bridgman method were obtained from the comparison of the recorded results and the CsCl-HfCl4 phase diagram. Keywords: CsCl-HfCl.sub.4./sub.; thermal properties; DSC analysis in closed system Available at various institutes of the ASCR
Studium vlivu složení ve směsi CsCl-HfCl.sub.4./sub. na její tepelné vlastnosti v uzavřeném systému pomocí DSC analýzy

Příspěvek se zabývá studiem tepelného chování směsi CsCl-HfCl4 o různém složení (nadbytek Cs- nebo Hf-složky) v uzavřeném systému (křemenné ampuli) pomocí neizotermní DSC analýzy. Ze získaných ...

Král, Robert; Zemenová, Petra; Vaněček, Vojtěch; Bystřický, Aleš
Fyzikální ústav, 2020

Compression of ecaped titanium micro-pillars for two principal orientations
Vokoun, David; Maňák, Jan; Tesař, Karel; Habr, Stanislav
2020 - English
The thermomechanical processing by equal-channel angular pressing (ECAP) is used for certain metals and alloys in order to make their structure fine and to increase material strength. In the previous study done at our institute, grade 2 titanium was successfully processed using four consecutive route A passes via a 90° ECAP die with high backpressure at room temperature. Orientation dependence of compressive and tensile loading of ECAPed titanium samples was demonstrated at macro-scale. However, scarce attention has been paid so far to the mechanical behavior of ECAPed titanium samples at micro-scale. In the present study, compression experiments on titanium micro-pillars, fabricated using focused ion beam, are carried out for two main directions in respect to preceding ECAP pressing (insert and extrusion directions). The purpose of this study is to discuss the orientation dependence of mechanical response during compression of the as-ECAPed titanium micro-pillars. Keywords: ECAP; micro-pillar; titanium Available in digital repository of the ASCR
Compression of ecaped titanium micro-pillars for two principal orientations

The thermomechanical processing by equal-channel angular pressing (ECAP) is used for certain metals and alloys in order to make their structure fine and to increase material strength. In the previous ...

Vokoun, David; Maňák, Jan; Tesař, Karel; Habr, Stanislav
Fyzikální ústav, 2020

Mass production of hydrogenated ZnO nanorods
Chang, Yu-Ying; Remeš, Zdeněk; Míčová, J.
2020 - English
We have developed an inexpensive and efficient technology of hydrothermal growth of ZnO nanorods from zinc nitrate hexahydrate (Zn(NO3)2·6H2O), as a precursor and hexamethylenetetramine (HMTA) (C6H12N4), as a surfactant followed by plasma hydrogenation in a novel inductively coupled plasma (ICP) quartz reactor and equipped with the rotary sample holder to stir powder during plasma treatment. We have optimized the photoluminescence spectroscopy for measuring optical scattering samples with the high sensitivity, precise sample positioning and very low influence of the scattered excitation light. Here we present the latest results on the enhancement of the UV photoluminescence of the ZnO nanorods after plasma hydrogenation. The exciton-related photoluminescence has been significantly enhanced whereas the deep defect related yellow photoluminescence has been significantly decreased.\n Keywords: nanomaterials; ZnO; photoluminescence; excitons; inductively coupled plasma; hydrogenation Available at various institutes of the ASCR
Mass production of hydrogenated ZnO nanorods

We have developed an inexpensive and efficient technology of hydrothermal growth of ZnO nanorods from zinc nitrate hexahydrate (Zn(NO3)2·6H2O), as a precursor and hexamethylenetetramine (HMTA) ...

Chang, Yu-Ying; Remeš, Zdeněk; Míčová, J.
Fyzikální ústav, 2020

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