Vol 87, No 6 (2023)

The influence of fiber diameter and addition of composite filler magnetite/reduced graphene oxide on the properties of electrospun scaffolds of poly(3-hydroxybutyrate) has been studied. The magnetic composite filler provides good magnetic properties and piezoresponse of the scaffolds, while changing the fiber diameter allows controlling the ductility, crystallinity, and surface electric potential.

Effect of spark plasma sintering temperature on the formation of Co filler particles in the Bi₂Te_2.1Se_0.9 matrix has been examined. Owing to high-temperature diffusion redistribution of atoms in the matrix and filler materials and chemical interaction between these materials, in the Bi₂Te_2.1Se_0.9 + 0.33 wt % Co, core–shell filler particles (Co@CoTe₂) are formed. With increasing the sintering temperature, fraction of the “CoTe₂ shell” in the particles increases, while fraction of the “Co core” decreases. This behavior is due to an increasing in the diffusion coefficient of Co in the Bi₂Te_2.1Se_0.9 matrix with increasing in the sintering temperature. The concentration profiles of the Co distribution of in the Bi₂Te_2.1Se_0.9 matrix, governed by diffusion, are well described using Fick’s second law for diffusion from a limited source of a diffusing substance. The diffusion coefficient of Co increases with increasing un the sintering temperature in accordance with the Arrhenius law and with an activation energy of ~0.61 eV.

Numerical micromagnetic modeling used to study the modes of propagation of spin waves and processes of power transfer in the considered arrays of microwaves in the configuration corresponding to excitation in two central channels of one of the layers of surface and inverse bulk magnetostatic spin waves is conducted. It is shown that the proposed structure performs the functions of spatial-frequency signal selection, the efficiency of which depends on the mutual orientation of the submagnetization field and the direction of wave propagation.

The high-temperature organic synthesis of hydrophobic superparamagnetic nanocomposites of the Fe₃O₄/ZnS and Fe₃O₄/ZnSe core–shell type is discussed. An analysis of the absorption, luminescence, magnetic circular dichroism (MCD) and morphology spectra of hydrophobic magnetoluminescent nanocomposites is presented. It is shown that nanocomposites have luminescent properties, and the growth of the shell on the Fe₃O₄ core retains the magnetic properties of the particles. An analysis of the MCD spectra shows that the magnetic field induces spin-dependent chiral magneto-optical activity. An estimate of the dependence of the g factor on the magnitude and sign of the external magnetic field demonstrates a change in the magnetization of the resulting nanocomposites relative to Fe₃O₄.

Magnetic elastomers based on polydimethylsiloxane polymer with a filler of barium hexaferrite microparticles with a homogeneous and porous microstructure have been obtained. The microstructure, magnetic and mechanical properties of the obtained samples were studied. The filler leaching method used in the work makes it possible to obtain magnetic elastomers with a porosity of about 58%. It is shown that the porous microstructure leads to a significant decrease in the Young’s modulus of the samples from 0.63 MPa (homogeneous) to 27 kPa (porous) and doesn’t produce any significant changes in the magnetic properties of the sample.

Pinning of the Fermi level on the oxidized (110) surface of AIII-Sb semiconductors (GaSb, Ga_0.78In_0.22As_0.18Sb_0.82, Ga_0.66Al_0.34As_0.025Sb_0.975) was studied. It is shown that the Fermi level is pinned at 4.65 ± 0.1 eV from the vacuum level. The presence of Sb was shown for the photooxidized Ga_0.78In_0.22As_0.18Sb_0.82 and Ga_0.66Al_0.34As_0.025Sb_0.975 surfaces. The formation of Sb on the surface because of faster oxidation of group III elements results in pinning of the Fermi level at the same distance from the vacuum level in III-Sb compounds.

On the single crystals of Hg_{1 – x}Fe_xSe (х ≤ 0.06 at %) with an extremely low concentration of the impurity iron atoms at room temperature (T = 300 K), high-temperature ferromagnetism of a new type in a impurity donor electron system was experimentally discovered.

A theoretical explanation is proposed for the shape of the long-wavelength edge of the luminescence line, which is caused by the recombination of a free electron and a hole of a neutral acceptor. The formation of complexes, in which a single hole is localized by the field of two attracting ions (\(A_{2}^{ - }\) complexes) and the subsequent recombination of holes in such complexes with electrons of the conduction band are considered. The Coulomb repulsion in the final state after recombination and the dispersion of the complexes in terms of the interionic distance provide an extended long-wavelength tail of the luminescence line, comparable in magnitude to the ionization energy of a single acceptor.

The energy position of size quantization levels size levels in the multiple Hg_0.3Cd_0.7Te/HgTe quantum wells grown by molecular beam epitaxy on (013)GaAs substrate has been studied. The experimental and calculated values of the energy position of three size quantization levels are obtained.

Domain instability in nonequilibrium electron-hole plasma leads to the formation of narrow moving regions of the ionizing electric field—collapsing Gunn domains. In pulse power electronics devices based on gallium arsenide, impact ionization in collapsing domains acts as an efficient mechanism for the generation of nonequilibrium carriers at low voltages and weak average electric fields.

A biexciton radiative cascade was recorded in the photoluminescence spectra of an InAs/GaAs QD embedded in a λ-cavity with a relatively high-quality factor of 4600, formed in a micropillar with GaAs/AlGaAs distributed Bragg reflectors. The spectrum and kinetics of the radiation, measured under conditions of two-photon excitation, demonstrated a significant effect of the microcavity on the emission process. A possible improvement based on this effect in the generation of entangled photon pairs is discussed.

The effective parameter of the electron-phonon interaction in a semiconductor film on ionic substrates has been determined. It is shown that interface phonons “transfer” the polarization of the medium from the substrate to the film. As a result, the polaron binding energy and the effective mass of carriers in the same film on different substrates can vary by tens or even hundreds of percent. Conditions for the realization of strong interaction for various films are found.

We proposed several types of design of terahertz emitters based on the perfect AlGaAs/GaAs superlattices obtained by molecular-beam epitaxy. Transition energies, gain, and losses are calculated for the developed structures, which determined the design of the created experimental structures.