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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 ...
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, ...
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 ...
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 ...
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 ...
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 ...
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