Number of found documents: 583
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Magnetocrystalline anisotropy of Ni-Mn-Ga-Co-Cu martensite
Rameš, Michal; Straka, Ladislav; Sozinov, A.; Heczko, Oleg
2022 - English
The martensites of Heusler alloys based on Ni-Mn-Ga exhibit magnetically-induced reorientation resulting in giant field-induced strain. Up to 12% strain was observed in Ni-Mn-Ga-Co-Cu with 4 at.% of Co and Cu. The driving force of the phenomenon is the magnetocrystalline anisotropy. We studied evolution of the anisotropy with temperature and compositions using magnetiyation curve measurements in four different single crystalline Ni-Mn-Ga-Co-Cu and compared with non-doped Ni-Mn-Ga. The anisotropy of martensite decreases with increasing average doping (Co+Cu)/2 but it does not scale with tetragonal ratio or valence electron concentration. Keywords: martensite; magnetocrystalline anisotropy; Heusler alloys; Ni-Mn-Ga Available at various institutes of the ASCR
Magnetocrystalline anisotropy of Ni-Mn-Ga-Co-Cu martensite

The martensites of Heusler alloys based on Ni-Mn-Ga exhibit magnetically-induced reorientation resulting in giant field-induced strain. Up to 12% strain was observed in Ni-Mn-Ga-Co-Cu with 4 at.% of ...

Rameš, Michal; Straka, Ladislav; Sozinov, A.; Heczko, Oleg
Fyzikální ústav, 2022

Chemická depozice diamantových tenkých vrstev z par plynů
Kromka, Alexander
2022 - Czech
Příprava diamantových vrstev a jejich (nano-) struktur vyžaduje zvládnutí více technologických kroků. V prvním kroku „diamantové technologie” je důležité aktivovat povrch nediamantové podložky vhodným procesem známým jako nukleace nebo zárodkování. Nejčastěji se jedná o proces pokrytí povrchu podložky (nano-) částicemi diamantu nebo aktivace povrchu podložky iontovým bombardováním. Druhým klíčovým krokem je samotný růst diamantové vrstvy tzv. chemickou depozicí z par plynů (tzv. „Chemical Vapor Deposition” - CVD) za nízkých tlaků (10 ÷ 10 000 Pa) a teplot v rozsahu 250 ÷ 1000 °C, která je nejčastěji realizována v plynné směsi metanu a vodíku v systému žhaveného vlákna nebo mikrovlnného plazmatu. V tomto příspěvku jsou oba technologické kroky, nukleace a růst, diskutovány se zřetelem aktuálních trendů a experimentálních aktivit probíhajících v laboratořích Fyzikálního ústavu AV ČR (FZÚ).\n The preparation of diamond layers and their (nano-) structures requires the optimization of several technological steps. In the first step of “diamond technology” it is important to activate the surface of the non-diamond substrate by a suitable process known as nucleation or nucleation. The second key step is the growth of the diamond layer itself by chemical vapor deposition (CVD) under low pressures (10 ÷ 10,000 Pa) and temperatures in the range of 250 ÷ 1000 °C, and from a gas mixture of methane and hydrogen commonly used in a hot filament or microwave plasma CVD systems. In this paper, both technological steps, nucleation and growth, are discussed in light of current trends and experimental activities taking place in the laboratories of the Institute of Physics of the Academy of Sciences of the Czech Republic (FZÚ). Keywords: diamond technology; nucleation; chemical vapor deposition Available at various institutes of the ASCR
Chemická depozice diamantových tenkých vrstev z par plynů

Příprava diamantových vrstev a jejich (nano-) struktur vyžaduje zvládnutí více technologických kroků. V prvním kroku „diamantové technologie” je důležité aktivovat povrch nediamantové podložky vhodným ...

Kromka, Alexander
Fyzikální ústav, 2022

Development and measurement of gas sensors for room temperature applications
Kočí, Michal
2022 - English
Gas sensing properties of a nanocrystalline diamond with a hydrogen-terminated surface (H-terminated NCD) and a molybdenum disulphide (MoS2) are investigated as conductivity sensors with built-in interdigital metal electrode structures. The H-terminated NCD was prepared by plasma-enhanced chemical vapour deposition (PECVD), and the MoS2 by a carbide-free one-zone sulfurization method. The sensor's responses were measured for oxidizing (NO2) and reducing (NH3) gases by the same equipment and setup. The parameters of the tested sensors are compared and critically evaluated. Advantageously, the MoS2/H-terminated NCD heterostructure enhances the gas sensing response at room temperature compared to the H-terminated NCD and MoS2 layers. Keywords: gas sensor; nanocrystalline diamond (NCD); transition metal dichalcogenide (TMD) Fulltext is available at external website.
Development and measurement of gas sensors for room temperature applications

Gas sensing properties of a nanocrystalline diamond with a hydrogen-terminated surface (H-terminated NCD) and a molybdenum disulphide (MoS2) are investigated as conductivity sensors with built-in ...

Kočí, Michal
Fyzikální ústav, 2022

Effect of molecular structure on liquid crystalline behaviour for chiral lactic acid derivatives
Mironov, Sergei; Bubnov, Alexej
2022 - English
Liquid crystals are self-organizing materials that have great potential for practical applications. The relationship has not been fully established and understood despite numerous studies. We discuss a relatively broad subclass of calamitic chiral lactic acid derivatives and provide specific examples of effective tuning of their mesomorphic and electro-optical behaviour using various types of lateral substitution placed on the molecular core. Keywords: chiral liquid crystals; lateral substitution; ferroelectric smectic phase; spontaneous polarization; lactic acid Available at various institutes of the ASCR
Effect of molecular structure on liquid crystalline behaviour for chiral lactic acid derivatives

Liquid crystals are self-organizing materials that have great potential for practical applications. The relationship ...

Mironov, Sergei; Bubnov, Alexej
Fyzikální ústav, 2022

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-synthesised zinc oxide nanoparticle behavior in liquids
Rutherford, D.; Jíra, J.; Kolářová, Kateřina; Matolínová, I.; Remeš, Zdeněk; Kuliček, J.; Padmanaban, D.; Maguire, P.; Mariotti, D.; Rezek, B.
2021 - English
ZnO nanoparticles have been synthesized using non-thermal atmospheric pressure plasma (ZnO-NTP). We investigated the behavior of these ligand-free as a colloid suspension using different solvents, from deionized water to physiological saline and microbial culture broth. We found that the zeta potential of ZnONTP became more negative after exposure to microbial culture broth relative to water, which suggests increased colloid stability. Photoluminescence spectra of ZnO-NTP were similar regardless of liquid type, yet optical and fluorescent images of samples showed different agglomeration behaviour depending on liquid type. Scanning electron microscopy images revealed large agglomerates of ZnO-NTP interacting with the surface of bacteria cells, ranging in size from 200 nm up to 2 µm. We also studied effect of sub-lethal concentrations of ZnO-NTP on bacteria under illumination. There was no significant difference in viable bacteria concentration after 24h exposure to 10 µg/mL ZnO-NTP. Keywords: zinc oxide; nanotechnology; colloid suspension; bacteria Available at various institutes of the ASCR
Plasma-synthesised zinc oxide nanoparticle behavior in liquids

ZnO nanoparticles have been synthesized using non-thermal atmospheric pressure plasma (ZnO-NTP). We investigated the behavior of these ligand-free as a colloid suspension using different solvents, ...

Rutherford, D.; Jíra, J.; Kolářová, Kateřina; Matolínová, I.; Remeš, Zdeněk; Kuliček, J.; Padmanaban, D.; Maguire, P.; Mariotti, D.; Rezek, B.
Fyzikální ústav, 2021

Radical-based tuning the surface functionality of MXene
Olshtrem, A.; Chertopalov, Sergii; Guselnikova, O.; Švorčík, V.; Lyutakov, O.
2021 - English
The family of MAX phases and their derivative MXenes are continuously growing in terms of both crystalline and composition varieties. MXenes are a new family of two-dimensional (2D) transition metal carbides, carbonitrides and nitrides, with a general formula Mn+1AXn, where n = 1–3, M denotes a transition metal, A is an element such as aluminum or silicon, and X is either carbon or nitrogen. Considering the various elemental composition possibilities, surface functional tunability, various magnetic orders, and large spin–orbit coupling, MXene can truly be considered as multifunctional materials that can be used to realize highly correlated phenomena. Keywords: chemical transformation; MXene; surface grafting; tuned functionalization Available at various institutes of the ASCR
Radical-based tuning the surface functionality of MXene

The family of MAX phases and their derivative MXenes are continuously growing in terms of both crystalline and composition varieties. MXenes are a new family of two-dimensional (2D) transition metal ...

Olshtrem, A.; Chertopalov, Sergii; Guselnikova, O.; Švorčík, V.; Lyutakov, O.
Fyzikální ústav, 2021

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 ...

Lebeda, M.; Vlčák, P.; Veřtát, P.; Drahokoupil, Jan
Fyzikální ústav, 2021

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 ...

Voves, J.; Pošta, A.; Davydova, Marina; Laposa, A.; Povolný, V.; Hazdra, P.; Lambert, Nicolas; Sedláková, Silvia; Mortet, Vincent
Fyzikální ústav, 2021

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 ...

Remeš, Zdeněk; Buryi, Maksym; Sharma, Dhananjay K.; Artemenko, Anna; Mičová, J.; Rezek, B.; Poruba, A.; Hsu, H.S.; Potocký, Štěpán; Babin, Vladimir
Fyzikální ústav, 2021

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