No (412)
Number of found documents:
412
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to
Diamond coated AlGaN/GaN high electron mobility transistors - effect of deposition process on gate electrode
Vanko, G.; Ižák, Tibor; Babchenko, O.; Kromka, Alexander
2015 - English
We studied the influence of the diamond deposition on the degradation of Schottky gate electrodes (i.e. Ir or IrO2) and on the electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs). In present study, the diamond films were selectively deposited on the AlGaN/GaN circular HEMT by focused (ellispoidal cavity reactor) and linear antenna (surface wave) microwave plasma at different temperatures from 400°C to 1100°C. The preliminary results on electrical measurements on the diamond-coated c-HEMTs showed degraded electrical properties comparing to c-HEMTs before deposition process, which was attributed to degradation of the Ir gate electrodes even at temperatures as low as 400°C. On the other hand, metal oxide gate electrode layer (IrO2) can withstand diamond CVD process even at high temperatures (~900°C) which make it suitable for fabrication of all-in-diamond c-HEMT devices for high-power applications.
Keywords:
GaN HEMT; CVD diamond; iridium oxide; thermal stability; IV characteristics
Available at various institutes of the ASCR
Diamond coated AlGaN/GaN high electron mobility transistors - effect of deposition process on gate electrode
We studied the influence of the diamond deposition on the degradation of Schottky gate electrodes (i.e. Ir or IrO2) and on the electrical characteristics of AlGaN/GaN high electron mobility ...
Scanning thermal microscopy of thermoelectric pulsed laser deposited nanostructures
Vaniš, Jan; Zelinka, Jiří; Zeipl, Radek; Jelínek, Miroslav; Kocourek, Tomáš; Remsa, Jan; Navrátil, Jiří
2015 - English
New materials with high possible figure of merit ZT are of high interest as a promising candidates for thermoelectric applications such as energy harvesting. Miniaturization of such systems tends toward developing of the suitable characterization method with nanometer resolution ability. In our contribution, we present the development and experimental results of a simple scanning probe microscopy method for the relative thermal conductivity characterization. The possibility of the setup is demonstrated on the set of different thin thermoelectric layers grown from hot pressed targets by pulsed laser deposition on the reference Si substrate. All the measurements were performed on the commercial Veeco Multimode scanning AFM/STM microscope with home developed controller and by using PicoCal Inc. bolometer probes with tungsten resistive path. All the experiments were done in the air at the ambient condition. Additional sample treatment for the measurement will be also briefly described
Keywords:
Scanning thermal microscopy; figure of merit; thermoeletric materials
Available at various institutes of the ASCR
Scanning thermal microscopy of thermoelectric pulsed laser deposited nanostructures
New materials with high possible figure of merit ZT are of high interest as a promising candidates for thermoelectric applications such as energy harvesting. Miniaturization of such systems tends ...
Modeling of nanofibers interaction with the environment
Klicmanová, I.; Sveshnikov, Alexey
2015 - English
Nanomaterials change our life. Every day they find applications in new branches of technology. At the same time, some branches of technology, like civil engineering, are rather conservative and do not accept new approaches lightly. Nanotextiles exhibit a number of qualities that make them a promising material for civil engineering applications. They can potentially play a role of filters, protective layers, armature and others. Properties of the nanotextiles can be significantly influenced by parameters of technological process. Pure experimental search of the optimal technological parameters to achieve the desired properties of the final material can be very tedious. Thus, a theoretical dependence of the properties of the nanotextile on parameters of the technological process must be established. Two independent tasks must be solved for this: the dependence of nanotextile structure on technological parameters, and determination of physical, chemical or biological properties of a nanotextile of a given structure. In this paper we discuss steps necessary for the solution of the second task.
Keywords:
Van der Waals; DLVO potential; Monte Carlo simulations
Available at various institutes of the ASCR
Modeling of nanofibers interaction with the environment
Nanomaterials change our life. Every day they find applications in new branches of technology. At the same time, some branches of technology, like civil engineering, are rather conservative and do not ...
Study of photocatalytic activity of Zn.sub.x./sub.Cd.sub.1-x./sub.S quantum dots in dependence on their composition using methylene blue
Praus, P.; Svoboda, L.; Hospodková, Alice; Mamulová Kutláková, K.
2015 - English
ZnCdS quantum dots (QDs) with the different composition were prepared by precipitation of zinc and cadmium acetates with sodium sulphide in the presence of cetyltrimethylammonium bromide (CTAB) used for stabilization of their aqueous colloid dispersions. Transition energies of these quantum dots were determined from the UV-VIS spectra of QDs colloid dispersions and consequently used for calculation of the QDs sizes according to the Schrodinger equation. The ZnCdS QDs size was found to be significantly influenced by their composition: the QDs size decreased with the increasing Zn content. The photocatalytic activity of the ZnCdS QDs was studied using the methylene blue decomposition under UV irradiation. Different photocatalytic activity depending on the composition x was observed and explained. The maximal photocatalytic activity was achieved for x = 0.6 when the energy of the irradiation photons was still sufficient to generate electron-hole pairs in majority of the QDs and at the same time the photocatalytic surface area was maximal.\n
Keywords:
quantum dots; ZnCdS; photocatalysis; UV-VIS absorption; x-ray diffraction
Available at various institutes of the ASCR
Study of photocatalytic activity of Zn.sub.x./sub.Cd.sub.1-x./sub.S quantum dots in dependence on their composition using methylene blue
ZnCdS quantum dots (QDs) with the different composition were prepared by precipitation of zinc and cadmium acetates with sodium sulphide in the presence of cetyltrimethylammonium bromide (CTAB) used ...
AlSb/InAsSb/AlSb deep QWs for the two band high temperature superlinear luminescence
Hulicius, Eduard; Hospodková, Alice; Pangrác, Jiří; Mikhailova, M.
2015 - English
InAlAsSb/GaSb based hetero-nanostructures with deep quantum wells grown on GaSb are promising materials for the optoelectronic devices for near- and mid-IR spectral regions. Optical power and quantum efficiency of the LEDs based on the narrow bandgap semiconductor compounds (InGa)(AsSb) are limited by the nonradiative Auger recombination. Earlier we have proposed a method to increase the optical power in the bulk narrow bandgap and later in GaSb-based nanostructures with a deep QW by the effect of impact ionization on the QW with high band offset.
Keywords:
quantum wells; luminescence; AlSb/InAsSb/AlSb
Available at various institutes of the ASCR
AlSb/InAsSb/AlSb deep QWs for the two band high temperature superlinear luminescence
InAlAsSb/GaSb based hetero-nanostructures with deep quantum wells grown on GaSb are promising materials for the optoelectronic devices for near- and mid-IR spectral regions. Optical power and quantum ...
BRK Technologies s.r.o. - Laser incineration of toxic medical wastes: towards to 100% safety
Rostohar, Danijela; Bulgakova, Nadezhda M.; Flimelová, Miroslava
2015 - English
The aim of the project is to design, construct and optimize a prototype of a laser incineration chamber (LICh) for treatment of toxic medical wastes. The LICh must provide safe incineration of organic wastes by an intense laser beam generating very high temperature of the incineration process. The LICh and involved technology must be relatively cheap and mobile for easy installation near the medical institutions producing toxic wastes. The most important aspect is the control of incineration products to ensure 100% safety of the gases issuing into atmosphere from the LICh. This is the first step of the whole project with aim to do the state of the art study and propose next steps.
Keywords:
laser incineration chamber; waste removal; toxic wastes
Available at various institutes of the ASCR
BRK Technologies s.r.o. - Laser incineration of toxic medical wastes: towards to 100% safety
The aim of the project is to design, construct and optimize a prototype of a laser incineration chamber (LICh) for treatment of toxic medical wastes. The LICh must provide safe incineration of organic ...
Investigation of thermal depolarization in high-power TGG ceramic rods
Lucianetti, Antonio
2015 - English
Wavefront deformation and thermal stress birefringence were evaluated for high-power TGG ceramic rods. The real laser beam profile used to heat the TGG ceramics was considered in the calculations. The numerical model was bench-marked with experimental data at about 100 W and then used to study the scalability of a similar TGG-based optical isolator up to 1 kW average power.
Keywords:
thermal modeling; optical isolation; birefringence
Available at various institutes of the ASCR
Investigation of thermal depolarization in high-power TGG ceramic rods
Wavefront deformation and thermal stress birefringence were evaluated for high-power TGG ceramic rods. The real laser beam profile used to heat the TGG ceramics was considered in the calculations. The ...
Characterization of amorphous and microcrystalline Si layers and ZnO layers on glass
Vaněček, Milan; Holovský, Jakub; Poruba, Aleš; Remeš, Zdeněk; Purkrt, Adam
2015 - English
Optical and photoelectrical properties of materials from TEL Solar were characterized in the Institute of Physics, AS CR in a broad spectral region and a high dynamic range. Conclusions on material properties with respect to thin film silicon solar cells were drawn.
Keywords:
optical properties; amorphous silicon; microcrystalline silicon; ZnO
Available at various institutes of the ASCR
Characterization of amorphous and microcrystalline Si layers and ZnO layers on glass
Optical and photoelectrical properties of materials from TEL Solar were characterized in the Institute of Physics, AS CR in a broad spectral region and a high dynamic range. Conclusions on material ...
In situ XPS characterization of diamond films after AR.sup.+./sup. cluster ion beam sputtering
Artemenko, Anna; Babchenko, Oleg; Kozak, Halyna; Ukraintsev, Egor; Ižák, Tibor; Romanyuk, Olexandr; Potocký, Štěpán; Kromka, Alexander
2015 - English
In this work, in situ XPS analysis of chemical composition of H- and O-terminated nano- and microcrystalline diamond (NCD and MCD) films before and after their sputtering by the Ar+ cluster ion beam was investigated. Scanning electron microscopy confirmed sputtering of all diamond surfaces with a rate about 0.5 nm/min. Raman spectroscopy and XPS revealed surface graphitization of diamond surface induced by sputtering. Moreover, XPS data showed the presence of about 0.7 % of Ar atoms on the investigated diamond surface after 66 min of sputtering. Also, oxygen residuals were still presented on the H-NCD surface after 66 min of sputtering. In contrast, no oxygen was found on the H-MCD surface just after 2 min of sputtering. Surface composition is discussed in respect to the diamond films growth parameters and surface structure.
Keywords:
diamond; depth profiling; XPS; sputtering; Raman
Available at various institutes of the ASCR
In situ XPS characterization of diamond films after AR.sup.+./sup. cluster ion beam sputtering
In this work, in situ XPS analysis of chemical composition of H- and O-terminated nano- and microcrystalline diamond (NCD and MCD) films before and after their sputtering by the Ar+ cluster ion beam ...
Wettability enhancement of polymeric and glass micro fiber reinforcement by plasma treatment
Trejbal, J.; Šmilauer, V.; Kromka, Alexander; Potocký, Štěpán; Kopecký, L.
2015 - English
Plasma treatments were used to modify surface properties of polyethylene terephthalate (PET) and glass micro fibers, to improve their wettability. PET fibers, having diameter of 400 μm, and glass fibers (14 μm) were exposed to low pressure oxygen plasma. A direct horizontal optical method was used for contact angle measurements on fiber surfaces submerged into distilled water. Surface morphology changes before and after treatment were characterized by scanning electron microscopy. Finally, cement paste specimens reinforced with PET and lime-based mortars reinforced with glass fibers were made and after 28 days of mixture curing tested by four-point bending tests. After oxygen plasma treatment contact angles decreased by 60 % on PET fibers and by 25 % on glass fibers in comparison with untreated fibers. Next, SEM images revealed the significant surface damages of PET fibers and minor damages of glass fibers. Both four-point tested samples reinforced with treated fibers exhibited the maximum bending strength loss about to 10 to 20 percent compared to samples with untreated reinforcement.
Keywords:
plasma treatments; cool oxygen plasma; wettability; contact angle; micro fibers
Available at various institutes of the ASCR
Wettability enhancement of polymeric and glass micro fiber reinforcement by plasma treatment
Plasma treatments were used to modify surface properties of polyethylene terephthalate (PET) and glass micro fibers, to improve their wettability. PET fibers, having diameter of 400 μm, and glass ...
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