Search

A fractal-percolation system that includes extended defects and random fluctuations in the alloy composition is formed during the growth of device structures based on Group-III nitrides. It is established that the specific features of this system are determined not only by the growth conditions. It is shown that the diversity of the electrical and optical properties of InGaN/GaN LEDs (light-emitting diodes) emitting at wavelengths of 450–460 and 519–530 nm, as well as that of the electrical properties of AlGaN/GaN HEMT (high-electron-mobility transistor) structures, is due to modification of the properties of the fractal-percolation system both during the growth process and under the action of the injection current and irradiation. The influence exerted by these specific features on the service life of light-emitting devices and on the reliability of AlGaN/GaN HEMT structures is discussed.

The sensitivity of classical n +/n – GaAs and AlGaN/GaN structures with a 2D electron gas (HEMT) and field-effect transistors based on these structures to γ-neutron exposure is studied. The levels of their radiation hardness were determined. A method for experimental study of the structures on the basis of a differential analysis of their current–voltage characteristics is developed. This method makes it possible to determine the structure of the layers in which radiation-induced defects accumulate. A procedure taking into account changes in the plate area of the experimentally measured barrier-contact capacitance associated with the emergence of clusters of radiation-induced defects that form dielectric inclusions in the 2D-electron-gas layer is presented for the first time.

The crystal structure and non-linear optical properties of CsNbMoO6 and CsTaMoO6 defect pyrochlores have been studied. The single crystals of these compounds grown by the flux method possess an octahedral faceting and reach up to 50 µm in size. The crystal structures of CsBVMoO6 (BV=Nb, Ta) were investigated by X-ray diffraction method. Both compounds crystallize in the cubic symmetry with noncentrosymmetric space group F-43m. The second harmonic generation of CsNbMoO6 and CsTaMoO6was found to be 1.6×10−2 and 8.5×10−4 of lithium niobate, correspondingly. It has been determined that distortions of [MO6] polyhedra (M=Nb, Ta, Mo) as well as polarizability and covalency of Nb–O and Ta–O bonds have a great effect on the second harmonic generation.

A 90WC-10Co powder mixture with TaC, VC and Cr3C2 grain growth inhibitors with average particle size about 50 nm was produced by deposition of Co. Two different sintering techniques had been used for consolidation. Microhardness and fracture toughness measurements of sintered materials had showed agreement with Hall-Petch equation. The corrosion behavior was investigated in neutral and acid solutions by electrochemical methods. The observed pseudo-passive transition had been associated with the so-called salt passivity — formation of cobalt sulfate salt layer on hard alloy surfaces.

The crystal structure and non-linear optical properties of CsNbMoO6 and CsTaMoO6 defect pyrochlores have been studied. The single crystals of these compounds grown by the flux method possess an octahedral faceting and reach up to 50 µm in size. The crystal structures of CsBVMoO6 (BV=Nb, Ta) were investigated by X-ray diffraction method. Both compounds crystallize in the cubic symmetry with noncentrosymmetric space group F-43m. The second harmonic generation of CsNbMoO6 and CsTaMoO6was found to be 1.6×10−2 and 8.5×10−4 of lithium niobate, correspondingly. It has been determined that distortions of [MO6] polyhedra (M=Nb, Ta, Mo) as well as polarizability and covalency of Nb–O and Ta–O bonds have a great effect on the second harmonic generation.

International audience; Composite InGaN/GaN/InAlN quantum dots (QDs) have been formed and studied. The structural properties of thin InAlN layers overgrown with GaN have been analyzed, and it is shown that 3D islands with lateral sizes of ∼(20–30) nm are formed in structures of this kind. It is demonstrated that deposition of a thin InGaN layer onto the surface of InAlN islands overgrown with a thin GaN layer leads to transformation of the continuous InGaN layer to an array of isolated QDs with lateral sizes of 20–30 nm and heights of 2–3 nm. The position of these QDs in the growth direction correlates with that of InAlN islands.

Construction of algebra of fuzzy numbers by Fourier holography techniques is presented. Implementation of arithmetic operations on both conventional and VSOP fuzzy numbers by both with plane reference wave and joint- transform setups is discussed. Realization of both addition and subtraction operations is presented.