Number of found documents: 434
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Transformation of ZnO-based structures under heavy Mo doping: Defect states and luminescence
Buryi, Maksym; Remeš, Zdeněk; Děcká, Kateřina; Mičová, J.; Landová, Lucie
2021 - English
Hydrothermally grown ZnO-based structures were heavily doped with Mo (various doping levels from 2 to 25%). It has been found that Mo strongly affects the ZnO structure and morphology rather resulting in the complex, mixed zinc and molybdenum oxides creation. Moreover, the material phases transformation upon the increased Mo content was observed. ZnO material phase was observed only at low Mo doping level (2 and 5%). This correlated very well to the changes in the luminescence and electron paramagnetic resonance signals. Keywords: ZnO; Mo doping; material phase transformation; luminescence; electron paramagnetic resonance Fulltext is available at external website.
Transformation of ZnO-based structures under heavy Mo doping: Defect states and luminescence

Hydrothermally grown ZnO-based structures were heavily doped with Mo (various doping levels from 2 to 25%). It has been found that Mo strongly affects the ZnO structure and morphology rather resulting ...

Buryi, Maksym; Remeš, Zdeněk; Děcká, Kateřina; Mičová, J.; Landová, Lucie
Fyzikální ústav, 2021

General overview of GaN devices and transport properties of AlGaN/GaN HEMT structures - impact of dislocation density and improved design
Hulicius, Eduard; Hájek, František; Hospodková, Alice; Hubík, Pavel; Gedeonová, Zuzana; Hubáček, Tomáš; Pangrác, Jiří; Kuldová, Karla
2021 - English
GaN-based nanostructures are used for many present semiconductor devices. The main topics are structures for blue LEDs and LDs, but there are also other interesting and important GaN devices namely for power electronics, scintillators and detectors as well as High Electron Mobility Transistors (HEMT). Reduction of dislocation density considerably increases electron mobility in 2DEG. All presented results support our expectation that a suitably designed AlGaN back barrier can help to prevent this phenomenon. Keywords: GaN devices; HEMT; MOVPE epitaxy; dislocation Available at various institutes of the ASCR
General overview of GaN devices and transport properties of AlGaN/GaN HEMT structures - impact of dislocation density and improved design

GaN-based nanostructures are used for many present semiconductor devices. The main topics are structures for blue LEDs and LDs, but there are also other interesting and important GaN devices namely ...

Hulicius, Eduard; Hájek, František; Hospodková, Alice; Hubík, Pavel; Gedeonová, Zuzana; Hubáček, Tomáš; Pangrác, Jiří; Kuldová, Karla
Fyzikální ústav, 2021

TCO work function tuning by nanodiamonds
Čermák, Jan; Miliaieva, Daria; Sokeng-Djoumessi, A.; Hoppe, H.; Stehlík, Štěpán
2021 - English
Deposition of nanodiamonds is found to be able to adjust the work function of transparent conductive oxides that are commonly used in photovoltaics. It also turned out that the change is dependent on the nanodiamond surface termination and that it is not stable in time. Keywords: nanodiamonds; Kelvin probe force microscopy; work function; stability Fulltext is available at external website.
TCO work function tuning by nanodiamonds

Deposition of nanodiamonds is found to be able to adjust the work function of transparent conductive oxides that are commonly used in photovoltaics. It also turned out that the change is dependent on ...

Čermák, Jan; Miliaieva, Daria; Sokeng-Djoumessi, A.; Hoppe, H.; Stehlík, Štěpán
Fyzikální ústav, 2021

Polyvinylpyrrolidone coating for nanodiamond stabilization in saline solution and silver nanoparticle decoration
Kolářová, Kateřina; Miliaieva, Daria; Stehlík, Štěpán
2021 - English
This work presents use of polyvinylpyrrolidone (PVP) for multipurpose coating of oxidized high-pressure high-temperature and detonation nanodiamonds. This simple way of nanodiamonds surface modification aims to improve their colloidal stability in biological environments and reduce their proneness to agglomeration. PVP immobilized on nanodiamond surface also provides for nanodiamond-supported AgNPs preparation by in situ synthesis using AgNO3 as a metallic nanoparticles precursor. Dynamic light scattering (DLS) and UV-vis spectroscopy were used for evaluation of nanoparticles size distribution and dispersibility in water and after exposition of nanoparticles in saline solution. Images acquired by scanning electron microscopy and transmission electron microscope validate the possibility of binding ~ 10 nm AgNPs to nanodiamonds surface. Keywords: nanodiamonds; silver nanoparticles; colloid solution Fulltext is available at external website.
Polyvinylpyrrolidone coating for nanodiamond stabilization in saline solution and silver nanoparticle decoration

This work presents use of polyvinylpyrrolidone (PVP) for multipurpose coating of oxidized high-pressure high-temperature and detonation nanodiamonds. This simple way of nanodiamonds surface ...

Kolářová, Kateřina; Miliaieva, Daria; Stehlík, Štěpán
Fyzikální ústav, 2021

Time-lapse monitoring of cell mechanical properties
Přibyl, J.; Rotrekl, V.; Pešl, M.; Jelínková, Š.; Kratochvílová, Irena
2021 - English
Atomic force microscopy (AFM) is a highly sensitive non-invasive surface method able to provide insight into cells' mechanical parameters. Membrane and sub-membrane development, as well as internal cellular properties, can be monitored. The stiffness of cells is a fundamental phenomenon that reflects changes in cell physiology. More importantly, changes in cell mechanical properties are also often found to be closely associated with various disease conditions. Cell mechanics are mainly dependent on cytoskeletal architecture. The development of cryopreserved cells' mechanical properties (stiffness) after thawing was studied using AFM.\n Keywords: atomic force microscopy; mechanical Mapping; cell stiffness; cryopreservation Available at various institutes of the ASCR
Time-lapse monitoring of cell mechanical properties

Atomic force microscopy (AFM) is a highly sensitive non-invasive surface method able to provide insight into cells' mechanical parameters. Membrane and sub-membrane development, as well as internal ...

Přibyl, J.; Rotrekl, V.; Pešl, M.; Jelínková, Š.; Kratochvílová, Irena
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

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

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

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

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