In this work, the effect of the action of gamma quanta and neutrons on the magnetic properties of Ta/feromagnet/IrMn/Ta bilayer films with an exchange bias of the hysteresis loop is studied. The samples were fabricated by magnetron sputtering, and their structure was studied by small-angle X-ray reflectometry and X-ray diffractometry. The measurement of the magnetic hysteresis loops of the irradiated and non-irradiated samples was carried out by the methods of magneto-optical Kerr magnetometry. As a result, the effect of broadening of the magnetic hysteresis loop after irradiation was found. The maximum broadening of the hysteresis loop was observed in the NiFe/IrMn film under neutron irradiation; in this case, the loop width increased by more than 2.5 times. No noticeable change in the field of the exchange bias of the hysteresis loops was observed in the entire range of radiation exposure.

The influence of methane plasma parameters on the deposition rate and on the content of the hydrogen and the sp3-carbon fraction in hydrogenated diamond-like carbon films (DLC) was investigated. It was shown that the proportion of the sp3-carbon fraction mainly depends on the inductive power and the argon addition to the plasma; the latter also contributes to a decrease of hydrogen in the films.

Magnetotransport measurements were carried out for YBa_2Cu_3O_{7-x} (YBCO) thin films in external perpendicular magnetic fields of H. The studies were performed both for the virgin samples and for the irradiated ones. Xenon ions were used as an external irradiation. Thus we studied features of the broadening of superconducting transition in YBCO films (virgin and irradiated). The broadening of superconducting drop was analyzed depending on an external magnetic field H, as well as on an irradiation dose n_D. When processing the experimental data R(H, T), we studied a criterion for determination of temperature dependence of the upper critical field H_{c2}(T). The criterion was analyzed depending on the defect concentration in the film corresponding to a certain value of n_D. It was found out that for a virgin sample, H_{c2} should be determined by the resistance level R = 0.4R_N inside the superconducting transition, where R_N = R(T = 100 K). With a gradual increase in n_D, this resistance level decreases. At sufficiently high radiation doses n_D > 7·10^{12} cm^{-2}, the H_{c2}(T) phase transition line should be determined by the level R ≈ 0.

As one of the approaches to improve p-HEMT, we studied the effect of misorientation of GaAs substrates on the surface morphology, structure, and electrical properties of pseudomorphic heterostructures, as well as the parameters of transistors based on them. In a single technological cycle, heterostructures were formed on vicinal substrates with (100) orientation and misoriented by 2° to (110) by the method of MOCVD (MOCVD) in a single technological cycle. It has been established that on misoriented substrates, the growth of structurally consistent and stressed epitaxial layers occurs according to a layered-step mechanism with the formation of macrosteps. On vicinal substrates, the formation of monatomic growth steps was observed. The comparative characteristics of p-HEMT obtained using two types of substrates are considered.

The results of a study of nitrogen-containing active regions based on superlattices grown on GaAs substrates are presented. Active regions based on alternating InAs and GaAsN layers were fabricated by molecular−beam epitaxy using a nitrogen plasma source. Based on the XRD analysis, the thicknesses and average composition of superlattice layers are estimated. The study of dark-field images obtained by transmission electron microscopy showed the presence of interdiffusion of InAs into GaAsN. The results of a study of the photoluminescence and electroluminescence spectra at different pump levels are presented. Efficient electroluminescence is demonstrated near 1150 nm with a full width at half-maximum of about 90 meV.

This paper presents the results of studying the growth of InGaN layers with a high (50-80%) indium content by molecular beam epitaxy with nitrogen plasma activation on sapphire substrates with GaN/AlN buffer layers. It is shown that the processes of dissociation and phase separation of the growing InGaN layer, which occur in structures with an indium fraction of about 50%, cannot be suppressed due to the transition to a lower temperature growth (470°C - 390°C) without significant degradation of the crystalline quality of the formed structures and a sharp decrease in their emissivity. As an alternative approach to suppressing diffusion processes on the growth surface and, as a result, obtaining homogeneous InGaN layers with an [In] content of ~ 50%, high-temperature (470°C) growth under highly nitrogen-enriched conditions (flux ratio III/V ~ 0.6) was tested. The InGaN layers grown in this way show intense photoluminescence, while at the same time showing no signs of phase separation according to X-ray diffraction data. This is critically important for the possibility of implementing optical amplification and laser generation in such structures in the red region of the spectrum and in the immediately adjacent part of the near infrared region.

Experimental studies of the relaxation of electrophysical parameters of SOI structures with different doses of hydrogen implantation after exposure to stationary X-ray radiation are presented.Investigation of high-frequency CV characteristics and pseudo-MOS transistors made it possible to obtain information about the accumulated charge, the density of surface states, mobility of carriers. The impurity composition and depth profileof hydrogen concentration were determined by the SIMS method. Structural perfection of the layers and interfaces was evaluated using the XRR and XRD methods. A different nature of the relaxation dependence and the recovery time of the electrophysical parameters for SOI structures with different doses of hydrogen implantation are recorded. The values of mobility and charge density are higher for the structure with a lower hydrogen implantation dose.

The features of the process of growth of multilayer heterostructures with InN/InGaN quantum wells (QWs) by the method of molecular-beam epitaxy with nitrogen plasma activation in the mode of modulated metal fluxes are studied. To compensate for elastic stresses in the structure, the active region was formed in the form of an InN/InGaN superlattice matched over the average lattice parameter with the underlying InGaN buffer layer. It has been shown that during the growth of relatively narrow InN QWs up to 3 nm wide, there is no relaxation of elastic stresses in the active region of the structure, and the dislocation density remains at the level ND ∼ (3−4) · 10^10 cm−2, which corresponds to the dislocation density in InGaN buffer. Such structures demonstrate the most intense PL in the wavelength range of 1.3−1.5 µm. With the growth of wider QWs, the imperfection of the structures sharply increases (ND > 10^11 cm−2), which is accompanied by a decrease in the emission intensity. The structures grown with InN/InGaN QWs demonstrated an order of magnitude better temperature stability of PL compared to bulk InN layers (PL quenching by ∼ 3 and ∼ 25 times, respectively, in the temperature range of 77−300 K). Nevertheless, at a low temperature (T = 77 K), the PL intensity of the studied structures with InN/InGaN QWs is noticeably inferior to that for the bulk InN layer, which apparently indicates a significant role of nonradiative recombination by the Shockley−Reed−Hall mechanism in structures with QWs (as opposed to Auger recombination in bulk InN).

In paper the influence of parameters of inductively coupled chloropentafluoroethane plasma on the rate and characteristics of gallium arsenide etching was studied. Etched GaAs profiles by white light interferometry and scanning electron microscopy were investigated. It turned out that the process rate does not depend on freon flow, but forward and inductive power, as well as pressure determined. In this case, when the power of the plasma generator increase, the surface morphology changes significantly, that manifests itself in roughness increase and the detection of defects on GaAs and mask. Carrying out a process at low pressure leads to the deposition of single large inhomogeneities on the substrate. The transition from pulsed to continuous etching is accompanied by deterioration in the anisotropy of a process due to the polymer layer deposition on side walls.

The disorder effect on superconducting properties of thin-film YBCO nanostructures in external magnetic fields is experimentally studied. The disorder was produced by irradiation with xenon ions. The research included transport measurements of narrow bridges based on HTSC YBCO films (thickness 50 nm) in strong magnetic fields (up to 12 T). Thus, for samples with different degrees of disorder, critical dependencies have been studied, i.e. the Hc2(T) phase transition line, the Hirr(T) irreversibility line, etc. The dependences of the mean-free path and critical temperature on the concentration of defects created by ion irradiation have been experimentally studied. The experimental data are described using formulas obtained within the framework of well-known models, such as the Ginzburg-Landau theory, the Drude theory and the Gorkov equations.

The possibilities of controlled exposure to ion irradiation (He+ with an energy of 20 keV and a fluence in the range from 3×1014 to 3×1015 cm–2) as a method for modifying the magnetic properties and domain structure of Co0.35Pt0.65 thin ferromagnetic films have been studied. It was found that the ion irradiation causes a change in the Dzyaloshinsky-Moriya interaction constant and a change in the skyrmion density that correlates with it. This result shows the possibility of homogeneous ion irradiation as a way to control the micromagnetic structure, namely the process of formation of skyrmion states.

The influence of thermal annealing on the transport properties of Ti/AlGaN/GaN low-barrier Mott diodes with near-surface polarization-induced δ-doping has been studied. It is shown that annealing provides additional possibilities for controlling the effective barrier height of diodes, improving and fine-tuning their transport characteristics. Thermal annealing can be used to fabricate low-barrier diodes designed to operate at high temperatures.

The technique of grazing incidence X-ray diffractometry (GIXRD) was used to study damaged layers in NaNd(WO4)2 and NaNd(MoO4)2 ceramics irradiated with high-energy ions. The possibilities and applicability limits of the technique for the analysis of such samples are shown. Estimates of the degree of amorphization in near-surface layers of ceramics are given depending on the irradiation dose. The higher resistance of NaNd(MoO4)2 ceramics to external radiation exposure as compared to NaNd(WO4)2 has been demonstrated.

GaAs-based heterostructures grown by metalorganic vapor-phase epitaxy on virtual Ge/Si substrates using an AlxGa1-xAs seed layer with different aluminum content x in the solid solution are investigated. The effect of solid solution composition on the density and size of antiphase domains emerging on the sample surface and on the optical properties of the GaAs layer is shown. Si(100) substrates with a small unintentional miscut of 0.7° to [110] were used for growth.

In this work, the dependence of plasma-chemical etching rate and the roughness of the surface of gallium arsenide crater on chloropentafluoroethane (C2F5Cl) concentration in a mixture with chlorine, forward power and etching duration were studied. Characteristics of GaAs etching crater were studied by white light interferometry and scanning electron microscopy. It is shown that C2F5Cl addition in chlorine-containing inductively coupled plasma led to a nonlinear change of gallium arsenide etching rate with time which can be explained by passivation of substrate surface at the initial stage by products of freon decay. Along with this, characteristics of the etching profile of GaAs are significantly improved. Forward power increase contributes to development of roughness, while the etching rate increases nonlinearly.

This paper presents the results of studying the properties of InGaN layers with a high InN content (80-90%) obtained by molecular beam epitaxy with plasma activation of nitrogen on sapphire substrates with AlN / GaN buffer layers. The InGaN layers were formed using the metal modulated epitaxy (MME) method, as well as in nitrogen and metal rich conditions. It was found that the use of the MME method leads to a decrease in the density of threading dislocations in the InGaN layers. Nevertheless, despite the higher dislocation density, the smallest threshold of stimulated emission of ~ 20 kW / cm2 at 77 K was obtained for the In0.8Ga0.2N layer grown under nitrogen rich conditions, which is associated with the lowest background electron concentration in this sample (1.6•1019 cm-3).

A new approach to the analysis of carbon-containing materials by the method of secondary ion mass spectrometry is studied, which allows one to determine the concentration of carbon atoms in the states of sp2 and sp3 hybridization. It is proposed to use the ratio of the intensities of cluster secondary ions C8/C7 as the main parameter of the mass spectra of secondary ions characterizing the concentration of N(sp3). From measurements of several test structures, a calibration dependence of N (sp3) on the C8/C7 ratio was obtained. The N(sp3) profiles of diamond-like carbon samples grown on diamond and silicon substrates were measured, showing an N(sp3) concentration of 0.3 to 0.6 for different growth modes and an inhomogeneous distribution of the N(sp3) concentration over the thickness of the samples.

The microstructure of Mo / Be multilayer periodic systems was studied by X-ray reflectivity and diffractometry and EXAFS spectroscopy. It was found that in the Mo / Be system, mixed zones of different compositions form at the boundaries. At the Mo-on-Be border, there is a mixed zone, similar in composition to MoBe22, and at the Be-on-Mo border, with MoBe2. As a result of thermal annealing for one hour, the structure of the transition boundaries in the multilayer system remains stable. With further annealing, diffusion processes occur that lead to the formation of another compound at the interface — MoBe2, instead of MoBe22, however, the period of the structure remains unchanged. This behavior explains the increase in the reflection coefficient of Mo / Be mirrors after annealing for one hour and a further decrease in the reflection coefficient with a longer annealing time.