No (412)
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412
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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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
Book of Abstracts of the 30.sup.th./sup. Joint Seminar of the Development of Materials Science in Research and Education
Kožíšek, Zdeněk; Král, Robert; Zemenová, Petra
2020 - English
Conference topics: \n- Trends in development of materials research\n- Education of materials science at the universities \n- Information about the research programmes of individual institutions \n- Information on equipment for preparation and characterisation of materials \n- Results of materials science research.
Keywords:
material sciences
Available at various institutes of the ASCR
Book of Abstracts of the 30.sup.th./sup. Joint Seminar of the Development of Materials Science in Research and Education
Conference topics: \n- Trends in development of materials research\n- Education of materials science at the universities \n- Information about the research programmes of individual institutions \n- ...
Mass production of hydrogenated ZnO nanorods
Chang, Yu-Ying; Remeš, Zdeněk; Míčová, J.
2020 - English
We have developed an inexpensive and efficient technology of hydrothermal growth of ZnO nanorods from zinc nitrate hexahydrate (Zn(NO3)2·6H2O), as a precursor and hexamethylenetetramine (HMTA) (C6H12N4), as a surfactant followed by plasma hydrogenation in a novel inductively coupled plasma (ICP) quartz reactor and equipped with the rotary sample holder to stir powder during plasma treatment. We have optimized the photoluminescence spectroscopy for measuring optical scattering samples with the high sensitivity, precise sample positioning and very low influence of the scattered excitation light. Here we present the latest results on the enhancement of the UV photoluminescence of the ZnO nanorods after plasma hydrogenation. The exciton-related photoluminescence has been significantly enhanced whereas the deep defect related yellow photoluminescence has been significantly decreased.\n
Keywords:
nanomaterials; ZnO; photoluminescence; excitons; inductively coupled plasma; hydrogenation
Available at various institutes of the ASCR
Mass production of hydrogenated ZnO nanorods
We have developed an inexpensive and efficient technology of hydrothermal growth of ZnO nanorods from zinc nitrate hexahydrate (Zn(NO3)2·6H2O), as a precursor and hexamethylenetetramine (HMTA) ...
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