


Vol 60, No 11 (2018)
- Year: 2018
- Articles: 32
- URL: https://bakhtiniada.ru/1064-8887/issue/view/14839
Article
Admittance of MIS-Structures Based on HgCdTe with a Double-Layer CdTe/Al2O3 Insulator
Abstract
Admittance of MIS structures based on n(p)- Hg1–xCdxTe (at x from 0.22 to 0.40) with SiO2/Si3N4, Al2O3, and CdTe/Al2O3 insulators is studied experimentally at 77 K. Growth of an intermediate CdTe layer during epitaxy results in the almost complete disappearance of the hysteresis of electrophysical characteristics of MIS structures based on graded-gap n-HgCdTe for a small range of the voltage variation. For a wide range of the voltage variation, the hysteresis of the capacitance-voltage characteristics appears for MIS structures based on n-HgCdTe with the CdTe/Al2O3 insulator. However, the hysteresis mechanism differs from that in case of a single-layer Al2O3 insulator. For MIS structures based on p-HgCdTe, introduction of an additional CdTe layer does not lead to a significant decrease of the hysteresis phenomena, which may be due to the degradation of the interface properties when mercury leaves the film as a result of low-temperature annealing changing the conductivity type of the semiconductor.



Effect of a Stepped Si(100) Surface on the Nucleation Process of Ge Islands
Abstract
Nucleation of Ge islands on a stepped Si(100) surface is studied. It is shown by diffraction of fast electrons that at a temperature of 600°C, constant flux of Si, and deposition rate of 0.652 Å/s, a series of the 1×2 superstructure reflections completely disappears, if the Si (100) substrate deviated by an angle of 0.35° to the (111) face is preliminarily heated to 1000°C. The disappearance of the 1×2 superstructure reflexes is due to the transition from the surface with monoatomic steps to that with diatomic ones. Investigations of the Ge islands’ growth were carried out on the Si(100) surface preliminarily annealed at temperatures of 800 and 1000°C. It is shown that the islands tend to nucleate at the step edges.



Comparison of the Growth Processes of Germanium Quantum Dots on the Si(100) and Si(111) Surfaces
Abstract
A comparative analysis is carried out of the growth peculiarities under molecular-beam epitaxy of germanium quantum dots on the silicon surfaces with different crystallographic orientations Si(100) and Si(111), including the case of the presence of tin surfactant on the surface. The free energy change, activation barrier of nucleation, critical thickness of the transition from two-dimensional growth to three-dimensional one, as well as the surface density and size distribution function of quantum dots in these systems are calculated.



Magnetic Field of Conductive Objects as Superposition of Elementary Eddy Currents and Eddy Current Tomography
Abstract
The paper represents induced currents in an electrically conductive object as a totality of elementary eddy currents. The proposed scanning method includes measurements of only one component of the secondary magnetic field. Reconstruction of the current distribution is performed by deconvolution with regularization. Numerical modeling supported by the field experiments show that this approach is of direct practical relevance.



Status and Prospects for Developing Electromagnetic Methods and Facilities for Engineer Reconnaissance in Russia
Abstract
An analysis of the most effective methods, techniques and scientific-research developments of induction mine detectors is performed, their comparative tactical-technical characteristics are reported, and priority avenues for further research are outlined.



Analysis of Dielectric Spectra of Water with Conductive Impurities in a Wide Frequency Range
Abstract
Experimental and theoretical studies of the electrophysical characteristics of water with different concentrations of conductive impurity, including the complex dielectric permittivity, complex conductivity, and complex impedance spectra are performed at frequencies in the range from 20 Hz to 40 GHz. It is demonstrated that the complex dielectric permittivity spectrum at frequencies in the range 500 MHz – 40 GHz is well described by the Debye model with a single relaxation time. In the low-frequency range, one more region of dispersion is observed caused by the phenomena occurring on the liquid-electrode interface. The characteristics of this dispersion region depend significantly on the dc electrical conductivity. It is demonstrated that in the examined frequency range, the influence of the interface phenomena on the complex impedance spectra of water with conductive impurity are well described by adding the impedance of an constant phase element. For the examined samples, the electrophysical characteristics and the parameters of the constant phase element are determined. The static dielectric permittivity and the parameters characterizing the double electric layer increase with the electrical conductivity.



Physical Principles of Development of the State Standard of Biological Cell Polarizability
Abstract
A new state standard of biological cell polarizability based on micron-size latex particles has been developed. As a standard material, it is suggested to use polystyrene. Values of the polarizability calculated for erythrocytes and values of the polarizability of micron-size spherical latex particles measured with measuring-computing complexes agree within the limits of satisfactory relative error. The Standard allows one the unit of polarizability measurements [m3] to be assigned to cells and erythrocytes for the needs of medicine.



Diffractive Hyperbola of a Skin Layer
Abstract
Based on an analysis of physics of the phase transition from the quasistatic state field to the running wave field of elementary electric and magnetic dipoles located in absorbing media, it is concluded that the skin layer is formed at the boundary of this phase transition. The possibility is considered of obtaining the diffractive hyperbola of the skin layer and its subsequent application for sensing of objects in strongly absorbing media.



Properties of Gallium Oxide Films Obtained by HF-Magnetron Sputtering
Abstract
The results of an analysis of structure and phase composition of gallium oxide films obtained by HF-magnetron sputtering are presented. It is shown that in the interval 290–350 K, the increase in the film conductivity with increasing temperature is due to the excitation of electrons from a local level Еt located 0.95 eV below the conduction band bottom.



Investigation of Backward Reflection from Aqueous Media at Arbitrary Grazing Angles
Abstract
A model of backward reflection is presented which is distinguished by the fact that it takes account of excitation of counterpropagating waves in bounding media. For the case of a homogeneous aqueous medium, it is shown that the proposed model describes distinguishing features of the angular dependence of the backward reflection coefficients for all angles of incidence of the waves on the air–water interface. Characteristic regions of the angular dependence, associated with different mechanisms of formation of the backward reflection, are elucidated.



Synthesis and Magnetic Properties of Fe–Co–Ni/С Nanocomposites
Abstract
Nanoparticles of the Fe–Co–Ni ternary alloy, encapsulated in the carbon matrix of nanocomposites, have been synthesized, The structure, phase composition, and magnetic properties of the obtained materials have been determined with the help of diffractometry and magnetometry. It has been established that nanoparticles of the ternary alloy are formed due to solution of cobalt in the Fe–Ni alloy. The composition of the nanoparticles of the alloy depends on the mass percent ratio of the metas in the precursor. With growth of the iron content, nanoparticles of the ternary alloy with various composition are formed with FCC and BCC crystal lattice structure. As the synthesis temperature and relative iron content are increased, the magnetization of the Fe–Co–Ni/C nanocomposites increases from 26 to 157 A·m2/kg. The coercive force is determined by the synthesis temperature, the size of the nanoparticles, and the composition of the alloy, and its value varies from 330 to 43 Oe.



Anisotropy of Nernst–Ettingshausen Effect in Superlattices During Scattering on Phonons
Abstract
The paper focuses on anisotropy of the transverse Nernst–Ettingshausen effect in superlattices depending on the degree of mini-band filling and magnetic field direction during scattering on acoustic and polar optical phonons. The authors demonstrate that in the case of scattering on polar optical phonons one observes considerable anisotropy and, depending on the magnetic field direction, the Nernst–Ettingshausen coefficient may change its sign.



Investigation of Transport Parameters of Graphene-Based Nanostructures
Abstract
The paper presents results of computer simulation of the main transport parameters of nanostructures obtained through the row-by-row removal of carbon atoms from graphene ribbon. Research into the electrical parameters is carried out within the density functional theory using the non-equilibrium Green functions in the local-density approximation. Virtual NanoLab based on Atomistix ToolKit is used to construct structures and analyze simulation results. Current-voltage characteristics, differential conductivity and transmittance spectra of nanostructures are calculated at different values of bias voltage. It is found that there is a large region of negative differential resistance in current-voltage characteristics of nanostructures caused by resonant tunneling of quasi-particles. Differential (dI/dV) characteristic also has similar changes. The obtained results can be useful for building novel electronic devices in the field of nanoelectronics.



Magnetic Properties and Structural Characteristics of BaFe12O19 Hexaferrites Synthesized by the Zol-Gel Combustion
Abstract
The phase structure, structural parameters, and basic magnetic characteristics of BaFe12O19 hexaferrites prepared by the zol-gel combustion method with subsequent annealing at a temperature of 850°С for 6 h are investigated. The influence of the organic fuel type on the properties of synthesized materials is analyzed. Values of the saturation magnetization and the anisotropy field are determined. It is established that they depend on the organic fuel type. It is shown that powders synthesized with citric acid used as a fuel have the largest particle sizes and the highest saturation magnetization.



The Effect of External Magnetic Field on Dielectric Permeability of Multiphase Ferrofluids
Abstract
Nowadays, ferrofluids are applied in various fields of science and technology, namely space, medicine, geology, biology, automobile production, etc. In order to investigate the feasibility of applying ferrofluids in magnetic field sensors, the paper presents research into the influence of the external magnetic field on dielectric permeability of ferrofluids comprising magnetite nanopowder, multiwall carbon nanotubes, propanetriol and deionized water. The real and imaginary parts of the dielectric permeability change respectively by 3.7 and 0.5% when applying the magnetic field parallel to the electric. The findings suggest that the considered ferrofluid can be used as a magnetic level gauge or in design of variable capacitors.



Validation of the Remote Method of Determining the Temperature and Concentration of High-temperature Water Vapor from the Reference Transmission Spectra
Abstract
The remote method of simultaneous determination of the temperature and concentration of hot gases from experimental spectral characteristics is validated on the example of the transmission spectra of water vapor measured with an average error of 5% at temperatures in the range 500–1770 K and concentrations 0.17–1 atm with resolution of 1 cm–1. When solving the direct optical problem, the parameters of water vapor spectral lines comprised in the HITEMP2010 database are analyzed with allowance for the last measurements of the absorption spectra with high resolution at Т ≈ 1300 K. It is demonstrated that overestimated values of the intensities of some hot water vapor spectral lines can be a reason for the deviation of the theoretical absorption predicted on the basis of the HITEMP2010 database from the experimental one. To increase the accuracy of solving the inverse optical problem, the data from several (up to eight) fragments of the spectral ranges 1000–2500 and 2600–4400 cm–1 are used. As a result, it is demonstrated that this allows the average error of determining reference values of the water vapor temperature and concentration to be decreased approximately to 0.3%, which corresponds to the average approximation error of theoretical values of its transmission function.



Holographic Formation of Diffraction Elements for Transformation of Light Beams in Liquid Crystal – Photopolymer Compositions
Abstract
A theoretical model of holographic formation of diffractive optical elements for transformation of light beam field into Bessel-like fields in liquid crystal – photopolymer (LC–PPM) composite materials with a dyesensitizer is developed. Results of numerical modeling of kinetics ofvariation of the refractive index of a material in the process of formation with different relationships between the photopolymerization rates and diffusion processes are presented. Based on the results of numerical simulation, it is demonstrated that when the photopolarization process dominates, the diffractive element being formed is distorted. This leads to a change in the light field distribution at its output and consequently, to ineffective transformation of the reading beam. Thus, the necessity of optimizing of the recording conditions and of the prepolymeric composition to increase the transformation efficiency of light beam fields is demonstrated.



Physical Approaches to Designing a Two-Cascade Terahertz Laser Generating Difference-Frequency Radiation in a Nonlinear Optical ZnGeP2 Crystal
Abstract
An optical layout of a two-cascade frequency converter of the mid-IR laser radiation into the terahertz (THz) radiation is proposed. In the first stage it is assumed to convert the Tm:YLF-laser frequency in a Cr+2:ZnSe polycrystal into the radiation with the wavelength ~2–3 μm. The second cascade can be presented as a parametric conversion of the frequencies of two laser sources operating in the ~2–3 μm range into the THz radiation via the difference-frequency mixing in a nonlinear optical ZnGeP2 crystal. The estimates of the terahertz output signal are reported.



Kinetics of the Active Medium of a Copper Vapor Brightness Amplifier
Abstract
A spatiotemporal kinetics of the active medium of a copper vapor brightness amplifier is described that allows gain characteristics to be investigated during the pump pulse. Model calculations show that changing the discharge parameters allows the radial gain profiles to be improved significantly, as well as the gain and the inversion duration to be increased. The data obtained will be used to choose the operating conditions for the active medium in the brightness amplifier mode.



Thermal Stability of Microstructure and Microhardness of Heterophase BCC-Alloys After Torsional Deformation on Bridgman Anvils
Abstract
The results of investigations of thermal stability of microstructure and microhardness of alloys of the V–4Ti–4Cr and Mo–47Re systems, subjected to torsional deformation by high quasi-hydrostatic pressure at room temperature, are reported. It is shown that submicrocrystalline and nanocrystalline states, and the respective high values of microhardness, persist up to the upper bound (~0.4 Тmelt) of the temperature interval of their recovery and polygonization in a single-phase state. The main factors ensuring thermal stability of highlydefective states in heterophase alloys are discussed.



Influence of After-Growth Treatments on the Optical Parameters of Teraherz ZnGeP2 Crystals
Abstract
Results of investigations are presented of the THz spectra of the refractive index n(v) and of the extinction coefficient k(v) for ZnGeP2 single crystals with different degrees of technological treatment – after growth by the vertical Bridgman technique, after heat treatment at temperatures above the Debye temperature for the highest-frequency phonons, and after modification of the single-crystal properties under irradiation by fast electrons (~4 MeV).



Effect of Orientation of Ice Crystals in Cirrus on Direct and Scattered Solar Radiation Fluxes
Abstract
The problem of solar radiation transfer by cirrus containing horizontally oriented ice crystals urgent today is considered. The results of a complex radiation experiment are described in which solar radiation fluxes at the Earth’s surface are measured and high-level clouds are vertically sensed by a polarization lidar. The lidar allows the full backscattering phase matrix (BSPM) to be determined. The degree of orientation of ice crystals in cirrus is estimated from the form of the BSPM elements and their interrelations. It is shown experimentally for the first time that the degree of orientation of crystalline particles in cirrus has a significant effect on the direct and scattered solar radiation fluxes arriving at the Earth’s surface.



Quasilinear Relaxation as a Mechanism for Electron Temperature Saturation in the Earth’s Plasmasphere
Abstract
A mechanism is presented according to which quasi-linear relaxation can cause electron temperature saturation at the observed level when the plasmasphere is heated by magnetohydrodynamic waves. An algorithm for calculating saturation temperatures is proposed, and they are numerically estimated. At low wave frequencies, saturation occurs at temperatures of 3–5 eV, and in the vicinity of cyclotron frequencies, it occurs at 2–4 eV.



Verifying Digital Components of Physical Systems: Experimental Evaluation of Test Quality
Abstract
This paper continues the study of high quality test derivation for verifying digital components which are used in various physical systems; those are sensors, data transfer components, etc. We have used logic circuits b01-b010 of the package of ITC’99 benchmarks (Second Release) for experimental evaluation which as stated before, describe digital components of physical systems designed for various applications. Test sequences are derived for detecting the most known faults of the reference logic circuit using three different approaches to test derivation. Three widely used fault types such as stuck-at-faults, bridges, and faults which slightly modify the behavior of one gate are considered as possible faults of the reference behavior. The most interesting test sequences are short test sequences that can provide appropriate guarantees after testing, and thus, we experimentally study various approaches to the derivation of the so-called complete test suites which detect all fault types. In the first series of experiments, we compare two approaches for deriving complete test suites. In the first approach, a shortest test sequence is derived for testing each fault. In the second approach, a test sequence is pseudo-randomly generated by the use of an appropriate software for logic synthesis and verification (ABC system in our study) and thus, can be longer. However, after deleting sequences detecting the same set of faults, a test suite returned by the second approach is shorter. The latter underlines the fact that in many cases it is useless to spend ‘time and efforts’ for deriving a shortest distinguishing sequence; it is better to use the test minimization afterwards. The performed experiments also show that the use of only randomly generated test sequences is not very efficient since such sequences do not detect all the faults of any type. After reaching the fault coverage around 70%, saturation is observed, and the fault coverage cannot be increased anymore. For deriving high quality short test suites, the approach that is the combination of randomly generated sequences together with sequences which are aimed to detect faults not detected by random tests, allows to reach the good fault coverage using shortest test sequences.



Electric Current Transmission Through Tissues of the Vestibular Labyrinth of a Patient: Perfection of the Vestibular Implant
Abstract
An electric model of current transmission through tissues of the vestibular labyrinth of a patient is suggested. To stimulate directly the vestibular nerve in surgical operation, terminations of the electrodes are implanted through the bone tissue of the labyrinth into the perilymph in the vicinity of the vestibular nerve. The biological tissue of the vestibular labyrinth surrounding the electrodes and having heterogeneous composition possesses conductive and dielectric properties. Thus, when a current pulse from the vestibular implant is applied to one of the electrodes, conductive disturbance currents may arise between the electrodes and the vestibular nerves that can significantly deteriorate the direct signal quality. To study such signals and to compensate for the conductive disturbance currents, an equivalent electric circuit with actual electric impedance properties of tissues of the vestibular system is suggested, and the time parameters of the conductive disturbance current transmission are calculated. It is demonstrated that these parameters can reach large values. The suggested electric model and the results of calculations can be used for perfection of the vestibular implant.



Principles of Structure and Phase Composition Formation in Composite Master Alloys of the Al–Ti–B/B4c Systems Used for Aluminum Alloy Modification
Abstract
The principles of formation of structure and properties of materials produced by self-propagating hightemperature synthesis (SHS) from the Al–Ti–B/B4C powder systems are identified. It is shown that the SHSmaterials produced from the Al–Ti–B powder systems consist of a TiAl intermetallic matrix with inclusions of titanium diboride particles. It is found out that an introduction of 1 wt.% of TiB2 particles into the melt of the AD35 aluminum alloy allows reducing the grain size from 620 to 220 μm and gives rise to an increase in the ultimate tensile strength of as-cast specimens from 100 to 145 MPa and in the plasticity from 7 to 9%.






Increase in the Lasing Efficiency of Thin-Film Lasers Based on 1.4- Distirylbenzene
Abstract
The possibility of development of a thin-film 1,4-distirylbenzene–based laser lasing in the blue spectral range in solutions and films is investigated. The stimulated emission of 1,4-distirylbenzene in a polymethylmethacrylate film with transverse pumping by a YAG-Nd3+ laser is obtained for the threshold power density W = 0.44 MW/cm2. It is shown that incorporation of the additional amorphous SiO2 layer, improving the condition of total internal reflection on the boundary of the active medium, decreases the lasing threshold to 50–70 kW/cm2; in this case, the efficiency of radiation conversion is equal to 20%.



Kinetic Model of the Initial Stage of the Nanowire Growth
Abstract
A kinetic model of the formation of pyramid-like bulges (pedestals) at the bases of vertical nanowires is proposed. The formation of the pedestals at the early stage of the nanowire growth is assumed to be induced by a higher nucleation rate of two-dimensional islands under the catalyst droplet, as compared to the nucleation rate at the non-activated surface areas. Kinetics of the nucleation and propagation of the steps in the pyramid is described with a model of the multilayer growth, taking into account that the catalyst droplet at the nanowire top is a strong sink for adatoms. It is shown that the transition from the growth of the pyramid to the axial growth of the nanowire is possible if the appearance of a nucleus of the new layer under the catalyst droplet results in a partial dissolution of the underlying layer. In this case a segment of the nanowire sidewall is formed, preventing the lateral growth of the layers generated by the droplet.



Physical Principles of the Method for Determination of Geometrical Characteristics and Particle Recognition in Digital Holography
Abstract
The physical principles of a method for determination of geometrical characteristics of particles and particle recognition based on the concepts of digital holography, followed by processing of the particle images reconstructed from the digital hologram, using the morphological parameter are reported. An example of application of this method for fast plankton particle recognition is given.



Coatings Based on Nanodispersed Oxide Materials Produced by the Method of Pneumatic Spraying
Abstract
New approaches are proposed, relying on which the coatings from nanodispersed oxide materials are formed on polypropylene fibers. It is shown that in the course of the viscous fluid – solid state transition of the polymer its nanoparticles are stabilized on the surface of the formed fibers.



Correction


