Black phosphorus (b-P) single crystals having the n-type electrical conductivity produced in a high pressure set-up (~1 GPa) with six diamond anvils at 800 °C for 12 h have been studied. The electrical conductivity σ(Т,В) and the Hall constant R_h(Т,В) have been analyzed within one-band and two-band models as functions of temperature in the 2 < Т < 300 K range and magnetic field in the 0 < В < 8 T range. Fitting of the experimental σ(Т,В) and R_h(Т,В) curves suggests the following key properties of the crystals: (1) intrinsic conductivity type, (2) approximately equal electron and hole concentrations and mobilities, (3) anisotropic behavior of electron and hole conductivities, concentrations and mobilities and (4) combination of negative and positive contributions to magnetoresistance (magnetoresistive effect, MR). In a zero magnetic field the anisotropy coefficient α = [σ_а(Т) – σ_с(Т)]/σ_с(Т) below 50—70 K is positive whereas above 220 K its sign changes to negative due to a specific combination of the temperature dependences of carrier concentration and mobility. It has been shown that the negative sign of relative MR (negative magnetoresistive effect) dominates at T < 25 K and B < 6 T and is presumably caused by the effects of strong localization resulting from structural disorder. The positive MR sign (positive magnetoresistive effect) is associated with the Lorentz mechanism of carrier movement and exhibits itself above 25 K in 6–8 T magnetic fields.

The current condition and outlooks of the world semiconductor and polycrystalline silicon (poly-Si) markets have been analyzed. A long period of low PS prices which hindered the growth of investments into the industry has now changed for price recovery to an investment attractive level. Demand and offer balance for the period until 2024 and for the long term has been analyzed, and the main currently used PS processes have been reviewed. The current poly-Si market proficiency is expected to remain in the near and medium terms. However the “green turn” of the energy industry announced by all the governments, the development of local markets and the price recovery to an investment attractive level have promoted the development of new PS fab projects. Of special importance for Russia is the choice of Siemens trichlorosilane process parameters. A specific feature of the Russian market is the presence of several very important fields (solar energy, microelectronics, high-power electronics, photonics and fiber optics) which are small by international standards and equally face raw material shortage. It appears that Russia will greatly benefit from integral projects delivering solutions of multiple raw materials supply problems.

In the present work, we investigated the effect of prolonged exposure on the electrical conductivity of crystals with a charged domain wall (CDW) in congruent lithium niobate crystals (LiNbO3, LN) of a nonpolar x-cut. Bidomain ferroelectric structures containing charged head-to-head domain boundaries were formed in the samples using methods of diffusion annealing in the air near the Curie temperature and infrared annealing in an oxygen-free environment. Reduction annealing of crystals in a nitrogen atmosphere was carried out to form color centers and concomitant increase in conductivity. Using an atomic force microscope (AFM) we observed the effect of degradation of the current value recorded when measuring the I-V curve. The influence of storage conditions on the electrical conductivity of CDW was studied. It was found that this effect was not related to the influence of the surrounding atmosphere on the surface but was presumably related to the redistribution of charge carriers shielding the bound charge of the CDW.

In this work, solid solutions of La_0.7Sr_0.3Mn_0.95Fe_0.05O_3-δ with different oxygen content were obtained by the solid-phase reactions technique. Based on the investigation of the dynamics of changes in the oxygen index (3 – δ) during heating of the samples, the formation of a stressed state in their grains as a result of annealing was established. This results in a decrease in the mobility of oxygen vacancies during the reduction of cations according to the Mn⁴⁺ + e^– → Mn³⁺ scheme and explains the decrease of released oxygen amount with an increase of δ as well as the heating rate of the samples. When studying the magnetic properties of the obtained samples, it was found that the temperature dependence of the magnetization obeys the Curie–Weiss law and as the oxygen defficiency increases, the Curie temperature for solid solutions decreases. It was found that the particles are in a frozen ferromagnetic state when measured in the low-temperature region of the М(Т) dependence in “zero-field mode” at Т ˂ Т_В. The presence of ferromagnetism at Т ˃ Т_В leads to a magnetically ordered state, in which the resulting magnetic moment of the magnetic particle is influenced by thermal fluctuations. When considering the temperature values of the magnetization of lanthanum-strontium manganite samples, it was found that with an increase of temperature in the low-temperature region, magnetic ordering is disturbed due to the excitation of magnons with a quadratic dependence of the energy from the wave vector, the number of which increases in proportion to T^3/2. This results in a decrease in the manganite magnetization. The observed temperature dependence of the magnetization measured in the “field-cooling mode” was approximated taking into account the quadratic and non-quadratic dispersion laws of the magnon spectrum.

Introduction of substitution atoms into carbon nanotubes is an efficient tool of controlling their physicochemical properties which allows one to expand their practical applications. Boron is one of the most promising materials used for the modification of carbon nanotubes. However until now there has been no systematization of research data on the effect of boron impurity atoms on the properties of carbon nanotubes, and this limits potential industrial applications of this nanomaterial. In this work the most efficient currently existing methods of synthesizing carbon nanotubes containing boron impurity atoms have been discussed and the physicochemical properties of the obtained nanomaterials have been analyzed. Furthermore predictions as to their potential application domains have been made on the basis of available theoretical and experimental results. Comparison of the developed technologies has shown that the most efficient synthesis method is the catalytic vapor phase deposition. The mechanical, electronic and chemical properties of boron-carbon nanotubes have also been reviewed. For a more comprehensive analysis of the dependence of the physicochemical properties of carbon nanotubes on the concentration of boron impurity a model experiment has been carried out involving quantum mechanics instruments which has shown a direct correlation between the band gap of the material and the number of boron impurity atoms. The main practical application trends of boron-containing carbon nanotubes have been outlined.

ZnO single crystals are used for the fabrication of laser targets for high-energy electron irradiated UV laser cathode-ray tubes and homoepitaxial substrates for lasers. The technology of ZnO based UV LEDs imposes strict requirements to surface quality. Chemical-mechanical polishing delivers good surface quality but it is known that polishing of ZnO polar faces may yield different results. Surface-sensitive high-resolution X-ray diffraction (HRXRD) and X-ray reflectometry (XRR) methods have been used for studying the structure of (0001) and (000–1) polar faces of ZnO after chemical-mechanical polishing. Two double-sided polished (0001) ZnO substrates have been cut out from different hydrothermally grown ingots. The damage and density depth profiles for the Zn and O faces of the specimens have been retrieved from the X-ray diffraction curves and the specular reflection curves, respectively. Intensity distributions in the vicinity of the (0002) and (0000) reciprocal lattice points have been taken on a D8 Discover X-ray diffractometer (Bruker-AXS, Germany) in a triple-axis setup. For separating the coherent and incoherent scattering components, the intensity profiles have been analyzed along sections perpendicular to the diffraction vector and located at different distances from the reciprocal lattice sites. The HRXRD and XRR data have been compared with atomic force microscopy (AFM) data. The HRXRD method has revealed damaged layers at both faces of the specimens, with the layer thicknesses differing for the Zn and O faces, i.e., 5–7 nm for the Zn face and 10–11 nm for the O face. The XRR method has shown that both faces are sufficiently smooth. These results have been confirmed by AFM (RMS roughness ~ 0.23 ± 0.07 nm). However, the concentration of electrons in the superficial layers has been found to change. The layer thickness proves to be greater for the O face. We have hypothesized that the phenomena observed are caused by the difference in the chemical interaction of the Zn and O faces with the polishing agents.