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Ab-initio study of surface energies and structural influece of vacancies in titanium nitride nanolayer
Lebeda, M.; Vlčák, P.; Veřtát, P.; Drahokoupil, Jan
2021 - English
The surface energies of 8 crystallographic planes and effects of nitrogen vacancies on the lattice parameter in rock salt-like structure of TiN (σ-TiN) were studied using ab-initio method of density functional theory (DFT) with the generalized gradient approximation functional (GGA) as parametrized by Perdex, Burke and Ernzerhof (PBE). The linear decrease of lattice parameter with the increasing presence of nitrogen vacancies up to ca. 80% was observed.\n
Keywords:
titanium nitride; TiNx; ab initio simulation; density functional theory; DFT; vacancies; lattice parameter; surface energy
Fulltext is available at external website.
Ab-initio study of surface energies and structural influece of vacancies in titanium nitride nanolayer
The surface energies of 8 crystallographic planes and effects of nitrogen vacancies on the lattice parameter in rock salt-like structure of TiN (σ-TiN) were studied using ab-initio method of density ...
Effect of the substrate crystalline orientation on the surface morphology and boron incorporation into epitaxial diamond layers
Voves, J.; Pošta, A.; Davydova, Marina; Laposa, A.; Povolný, V.; Hazdra, P.; Lambert, Nicolas; Sedláková, Silvia; Mortet, Vincent
2021 - English
Epitaxial growth of diamond is critically important for the fabrication of diamond-based electronic devices. The emerging study of the epitaxial diamond growth on the (113) vicinal surfaces evidences highly needed high growth rates and low structural defects concentrations with both p- and n-type doping. In this work, we compare the morphology and dopant concentration incorporation of heavily boron-doped (113) epitaxial diamond layers with conventionally studied (100) and (111) epitaxial layers. Epitaxial layers were grown using resonance cavity Microwave Plasma Enhanced Chemical Vapor Deposition (MWPECVD) system. The surface morphology of epitaxial layers was studied by optical microscopy and atomic force microscopy, whereas the boron incorporation homogeneity was determined by Raman spectroscopy mapping.
Keywords:
diamond; epitaxy; defects; boron doping; Raman mapping
Available at various institutes of the ASCR
Effect of the substrate crystalline orientation on the surface morphology and boron incorporation into epitaxial diamond layers
Epitaxial growth of diamond is critically important for the fabrication of diamond-based electronic devices. The emerging study of the epitaxial diamond growth on the (113) vicinal surfaces evidences ...
Emergence of dark ZnO nanorods by hydrogen plasma treatment
Remeš, Zdeněk; Buryi, Maksym; Sharma, Dhananjay K.; Artemenko, Anna; Mičová, J.; Rezek, B.; Poruba, A.; Hsu, H.S.; Potocký, Štěpán; Babin, Vladimir
2021 - English
We employed a custom-built inductively coupled plasma (ICP) 13.56 MHz reactor with up to 300 W RF discharge power. Hydrothermally grown ZnO nanorods were exposed to the ICP plasma with a mixture of hydrogen and argon for up to 30 min, followed in-situ by plasma oxidation. Plasma properties were monitored by optical emission spectroscopy (OES) and by measuring the self-bias potential of the stainless steel sample holder separated from the ground by a blocking capacitor. The exciton-related UV photoluminescence of ZnO nanorods and optical absorption increases significantly after the plasma treatment. We attribute it to the complex changes of ZnO surface electronic states that also give rise to its black color visually.
Keywords:
ZnO; ICP; photoluminescence
Fulltext is available at external website.
Emergence of dark ZnO nanorods by hydrogen plasma treatment
We employed a custom-built inductively coupled plasma (ICP) 13.56 MHz reactor with up to 300 W RF discharge power. Hydrothermally grown ZnO nanorods were exposed to the ICP plasma with a mixture of ...
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 ...
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 ...
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 ...
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 ...
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 ...
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). ...
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 ...
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