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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
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.
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Time-lapse monitoring of cell mechanical properties
Přibyl, J. ; Rotrekl, V. ; Pešl, M. ; Jelínková, Š. ; Kratochvílová, Irena
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
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Polyvinylpyrrolidone coating for nanodiamond stabilization in saline solution and silver nanoparticle decoration
Kolářová, Kateřina ; Miliaieva, Daria ; Stehlík, Štěpán
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.
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Radical-based tuning the surface functionality of MXene
Olshtrem, A. ; Chertopalov, Sergii ; Guselnikova, O. ; Švorčík, V. ; Lyutakov, O.
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.
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Chemical deposition of diamond thin films from gas vapors
Kromka, Alexander
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).
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