bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication and characterization of AlGaN/GaN HEMTs with high power gain and efficiency at 8 GHz
Authors: Wang Quan , Chen Changxi , Li Wei , Qin Yanbin , Jiang Lijuan , Feng Chun , Wang Qian , Xiao Hongling , Chen Xiufang , Liu Fengqi , Wang Xiaoliang , Xu Xiangang , Wang Zhanguo
Published: December 2021

State-of-the-art AlGaN/GaN high electron mobility structures were grown on semi-insulating 4H-SiC substrates by MOCVD and X-band microwave power high electron mobility transistors were fabricated and characterized. Hall mobility of 2291.1 cm2/(V·s) and two-dimensional electron gas density of 9.954 × 1012 cm–2 were achieved at 300 K. The HEMT devices with a 0.45-μm gate length exhibited maximum drain current density as high as 1039.6 mA/mm and peak extrinsic transconductance of 229.7 mS/mm. The f
T of 30.89 GHz and f
max of 38.71 GHz were measured on the device. Load-pull measurements were performed and analyzed under (–3.5, 28) V, (–3.5, 34) V and (–3.5, 40) V gate/drain direct current bias in class-AB, respectively. The uncooled device showed high linear power gain of 17.04 dB and high power-added efficiency of 50.56% at 8 GHz when drain biased at (–3.5, 28) V. In addition, when drain biased at (–3.5, 40) V, the device exhibited a saturation output power density up to 6.21 W/mm at 8 GHz, with a power gain of 11.94 dB and a power-added efficiency of 39.56%. Furthermore, the low f
max/f
T ratio and the variation of the power sweep of the device at 8 GHz with drain bias voltage were analyzed.
Humidity sensing properties of spray deposited Fe doped TiO2 thin film
Authors: Gapale Dipak L , Bardapurkar Pranav P. , Arote Sandeep A. , Dalvi Sanjaykumar , Baviskar Prashant , Borse Ratan Y
Published: December 2021

In the present work, ferrite (Fe) doped TiO2 thin films with different volume percentage (vol%) were synthesized using a spray pyrolysis technique. The effect of Fe doping on structural properties such as crystallite size, texture coefficient, microstrain, dislocation densities etc. were evaluated from the X ray diffratometry (XRD) data. XRD data revealed a polycrystalline anatase TiO2 phase for sample synthesized up to 2 vol% and mixed anatase and rutile crystalline phase for sample synthesized at 4 vol% Fe doped TiO2. The crystalline size was observed to decrease with increase in Fe dopant vol% and also other structural parameters changes with Fe dopant percentage. In the present work, electrical resistance was observed to decrease with a rise in Fe dopant vol% and temperature of the sample. Thermal properties like temperature coefficient of resistance and activation energy also showed strong correlation with Fe dopant vol%. Humidity sensing properties of the synthesized sample altered with a change in Fe dopant vol%. In the present paper, maximum sensitivity of about 88.7% for the sample synthesized with 2 vol% Fe doped TiO2 and also the lowest response and recovery time of about 52 and 3 s were reported for the same sample.
Framework for TCAD augmented machine learning on multi- I–V characteristics using convolutional neural network and multiprocessing
Authors: Hirtz Thomas , Huurman Steyn , Tian He , Yang Yi , Ren Tian-Ling
Published: December 2021

In a world where data is increasingly important for making breakthroughs, microelectronics is a field where data is sparse and hard to acquire. Only a few entities have the infrastructure that is required to automate the fabrication and testing of semiconductor devices. This infrastructure is crucial for generating sufficient data for the use of new information technologies. This situation generates a cleavage between most of the researchers and the industry. To address this issue, this paper will introduce a widely applicable approach for creating custom datasets using simulation tools and parallel computing. The multi-I–V curves that we obtained were processed simultaneously using convolutional neural networks, which gave us the ability to predict a full set of device characteristics with a single inference. We prove the potential of this approach through two concrete examples of useful deep learning models that were trained using the generated data. We believe that this work can act as a bridge between the state-of-the-art of data-driven methods and more classical semiconductor research, such as device engineering, yield engineering or process monitoring. Moreover, this research gives the opportunity to anybody to start experimenting with deep neural networks and machine learning in the field of microelectronics, without the need for expensive experimentation infrastructure.
On electron acceleration by mildly-relativistic shocks: PIC simulations
Authors: Romansky V I , Bykov A M , Osipov S M
Published: December 2021

Radio observations revealed a presence of relativistic supernovae - a class of objects intermediate between the regular supernovae and gamma-ray bursts. The typical Lorentz-factors of plasma flows in relativistic radio-bright supernovae were estimated to be about 1.5. Mildly relativistic shocks in electron-ion plasmas are known to efficiently accelerate radio-emitting electrons if the shock is subluminous. The inclination angle of the velocity of subluminous shock to the ambient magnetic field should be below a critical angle which depends on the Mach number and the plasma magnetization parameter. In this paper we present particle-in-cell modeling of electron acceleration by mildly-relativistic collisionless shock of different obliquity in a plasma with ratio of the magnetic energy to the bulk kinetic energy σ ≈ 0.004 which is of interest for the relativistic supernovae modeling. It was shown earlier that a development of the ion scale Bell-type instability in electron-ion relativistic shock may have a strong influence on the electron injection and acceleration. In the time period of about

1500

ω

p
i

−
1

(ωpi
is the ion plasma frequency) after the shock initialization the magnetic field fluctuations generated by Bell’s instability may significantly decreases number of accelerated electrons even in a sub-luminous shock. We study here the evolution of the electron spectra of subluminous shocks of different obliquity. This is important to for modeling of synchrothron spectra from relativistic supernovae.
The candidates for Class I methanol masers
Authors: Nesterenok A V
Published: December 2021

The collisional excitation of methanol molecule in non-dissociative magnetohydro-dynamic shock waves is considered. All essential chemical processes that determine methanol abundance in the gas are taken into account in the shock model. The large velocity gradient approximation is used in the calculations of energy level populations of the molecule. We calculate the optical depth for inverted methanol transitions, and present the list of candidates for Class I methanol masers that have collisional pumping mechanism.
Self-consistent Monte Carlo model of particle acceleration by relativistic shocks
Authors: Osipov S M , Bykov A M , Lemoine M
Published: December 2021

We present a self-consistent Monte Carlo model of particle acceleration by relativistic shock waves. The model includes the magnetic field amplification in the shock upstream by cosmic ray driven plasma instabilities. The parameters of the Monte Carlo model are obtained based on PIC calculations. We present the spectra of accelerated particles simulated in the frame of the model.
Interaction of rotational discontinuities with energetic ions in the precursor of the Earth’s bow shock
Authors: Kropotina Julia A , Artemyev Anton V. , Bykov Andrei M. , Vainchtein Dmitri L.
Published: December 2021

We combined in-situ solar wind observations by ARTEMIS and MMS missions with kinetic hybrid simulations to study the interaction of solar wind rotational discontinuities (RDs) with the foreshock of the Earth’s bow shock. We found that whistler modes excited by diffuse energetic particles were strongly coupled with RDs and lead to their temporary dissociation. At the same time, RDs trigger the steepening of whistler waves and the generation of ’shocklets’ - small localised shock-like structures, capable of trapping energetic particles and growing up by absorbing the particles energy.
Fundamental parameters modeling for the lunar telescope
Authors: Andreev A O , Petrova N K , Nefedyev Y A , Zagidullin A A
Published: December 2021

The powerful flow of highly accurate and multiparameter information produced by spacecrafts has caused a surge interest in the industrial robotic exploration of the Moon and manned flight to Mars after the creation of long-term lunar bases. The modern level of both ongoing and planned lunar studies is characterized by a high level of observation accuracy and a large variety of observation methods. The study of the Moon’s rotational parameters (MRP) is of important value. For this reason, new methods for analyzing big data sets on observation of MRP and extracting the highest possible amount of scientific information from them are needed. Such space technologies require the creation of in-situ telescopes on the Moon. The long-term laser measurements have supplied comprehensive observational information about the Moon. This allows for a description of the Moon’s dynamics with the accuracy required at the current stage - the error of determining the distance to the Moon should be less than a meter, while the one of establishing rotational parameters - arc milliseconds. Nevertheless, there is a necessity to obtain observation data independent of laser measurements. One of the ways to do it is to place on the lunar surface one or several optical telescopes, that will allow determining lunar rotational parameters by measuring the trajectories of the stars and will also be used to solve astrophysical and astrometric problems in the future. This work considers the results of computer modeling of observations taken by lunar in-situ telescopes located at various selenographic latitudes. The sensitivity of MRP to the observed selenographic coordinates of the stars is assessed. Based on the analysis of the simulation results, the optimum location of the telescope is concluded to be at a latitude of 30–45°. The constructive suggestions on the described experiment’s implementation are presented in the paper. The details that will allow implementing or declining the practical implementation of the in-situ telescope are discussed.
Structural analysis of the comet 45P/Honda based on isophote modeling
Authors: Churkin K O , Andreev A O , Nefedyev Y A , Arkhipova A A , Demina N Y
Published: December 2021

The work focuses on using the isophote method to construct a 45P/Honda comet model. At the same time, important problems were solved for modeling the physical surface of a comet and studying the structure of the cometary nucleus. This is due to the fact that, on the basis of modern studies of meteoroids, complex internal processes and dynamic phenomena on their surface have been discovered. The study of comet nuclei is of great importance, since, according to the theory of their formation, they were formed from the matter of the protoplanetary disk. Thus, modeling and analysis of the structure of various comets make it possible to create a more accurate theory of their evolution. This made it possible to evaluate the structural parameters more accurately and reliably. This allowed for the evaluation of the structural parameters more accurately and reliably. Isophotes of the nucleus, coma and tail of comet 45P/Honda were determined. Depending on the point where the comet is located on the trajectory of its orbit, one can see structural changes in the comet’s brightness from the nucleus to the peripheral region. Near the cometary nucleus, the isophotes are circular in shape. If in the center of the model the isophotes have a shape close to narrow rings, then elongations in the direction of the cometary tail and thickening of their structure appear towards the peripheral regions. Large and small tail rays can be distinguished, and the nucleus is well marked. In the future, the author’s method for modeling isophotes, developed in this work, will allow studying the structure of various cometary objects, and, based on the results, determine the degree of comet activity. On the other hand, about the development of the theory of dynamic processes and the evolution of the Solar system, one can use the data on changes in cometary activity in the process of its movement around the Sun.
Unusual asteroid 2020 SO: astrometric investigation of the American rocket booster that returned to near-Earth space
Authors: Petrova S N , Devyatkin A V , Gorshanov D L , L’vov V N , Rusov S A
Published: December 2021

In the frame of this study astrometric observations of an unusual object 2020 SO - a newly discovered asteroid that turned out to be a Centaur upper-stage booster from 1960s - during its two close approaches to the Earth in December, 2020 and February, 2021 were carried out using two telescopes of Pulkovo observatory. The orbit of the object in question was determined and its future orbital evolution was modelled.
Constraints on the temperature-density relation of the intergalactic medium with non-negligible absorber spatial structure
Authors: Telikova K N , Shternin P S , Balashev S A
Published: December 2021

We investigate evolution of physical parameters of the intergalactic medium using an analysis of Lya forest lines detected towards distant quasars. We used the enlarged sample of 98 quasars obtained with Keck/HIRES and VLT/UVES. We show that taking into account a finite spatial size of absorbers, regulated by pressure smoothing, significantly affects the inferred thermal parameters of the intergalactic gas, such as the hydrogen photoionization rate and parameters of the temperature-density relation. Using Bayesian framework we constrained for the first time the scale parameter between the Jeans length and characteristic size of the absorbers. We also discuss limitations of the method based on the analysis of the minimal broadending of Lya lines, which stem from the patchy nature of He II reionization.
The influence of small-scale magnetic field on the heating of J0250+5854 polar cap
Authors: Barsukov D P , Matevosyan A A , Morozov I K , Popov A N , Vorontsov M V
Published: December 2021

The influence of surface small-scale magnetic field on the heating of PSR J0250+5854 polar cap is considered. It is assumed that the polar cap is heated only by reverse positrons accelerated in pulsar diode. It is supposed that pulsar diode is located near the star surface (polar cap model) and operates in the steady state space charge-limited flow regime. The reverse positron current is calculated in the framework of two models: rapid and gradually screening. To calculate the production rate of electron-positron pairs we take into account only the curvature radiation of primary electrons and its absorption in magnetic field. It is assumed that some fraction of electron-positron pairs may be created in bound state that can later be photoionized by thermal photons from star surface.
Measurement of the photon detection efficiency of silicon photomultipliers for the new detector cluster of the Cherenkov gamma-ray telescope TAIGA-IACT equipped with UV filters
Authors: Kuleshov D O , Simonyan V A , Bogdanov A A , Kholupenko E E , Tuboltsev Yu V , Chichagov Yu V , Krassilchtchikov A M
Published: December 2021

This study was devoted to measurements of the UV-range photon detection efficiency (PDE) of OnSemi MicroFJ SiPM detectors use together with custom UV filters and of the transmission coefficient of these filters at 277 nm. The final goal of these measurements was to determine feasibility of the filters for the new detector cluster of the TAIGA-IACT telescope. PicoQuant PLS-270 UV source emitting pulses at 277 nm was calibrated. The obtained dependences of the registered radiation power on the distance between the emission source and the reference detector are well approximated by the inverse square function, hence no significant scattering or absorption influenced the PDE measurements. The dependences of the number of detected photons on the distance between the source and the detector were obtained. These dependencies are also well approximated by the inverse square function. The PDE of SiPM MicroFJ-60035 detector was measured at the level of 10.0 ± 0.7%. The transmission coefficients of the considered set of filters at the wavelength of 277 nm were also obtained. The SL 240-300 filter has a sufficiently high transmission coefficient and it is advisable to use it as a bandpass ultraviolet filter in the new detector cluster of the TAIGA-IACT telescope; the SL 290-590 filter absorbs ultraviolet light quite well and is applicable in the visible range.
The effect of gamma quanta absorption due to interaction with thermal bremsstrahlung photons of hot gas in galaxy clusters
Authors: Popov A N , Barsukov D P , Ivanchik A V , Bobashev S V
Published: December 2021

The interaction of gamma quantum from distant sources with thermal bremsstrahlung photons of hot intracluster gas with producing electron-positron pair in case of 10 galaxy clusters is considered. It is supposed that intracluster gas in considered clusters is isothermal and electron number density may be described by β distribution with β = 2/3. It is presented that the optical depth due to considered interaction is about 10−8 — 10−.
Dynamics of Langmuir waves due to induced scattering on thermal electrons of solar plasma
Authors: Kudryavtsev I V
Published: December 2021

The temporal evolution of Langmuir waves due to induced scattering on thermal electrons of solar plasma for a case of anisotropic distribution of waves is considered. The results of calculations are submitted. It is shown that the induced scattering of waves on thermal electrons does not lead to isotropization of Langmuir waves. But effective transition of energy from waves with the large wave vectors to waves with smaller wave vectors occurs similar to the isotropic case.
The impact of laser-induced thermocoagulation effects on the optical spectra of brain tissues
Authors: Israpov E Kh , Giraev K M , Ashurbekov N A , Rabadanov K M , Magomedov M A
Published: December 2021

In this work, the results of spectral and optical studies of the grey matter tissues of the brain by a laser hyperthermia action are presented. The coefficients of optical absorption and transport scattering in the spectral range of 250-1500 nm are determined, and the features of the spatial distribution of the laser radiation intensity in the studied objects are identified. It is shown that the coagulation effects lead to compaction and an increase in the concentration of endogenous chromophores and structural elements, which is reflected in the optical properties of biological objects.
Comparative analysis of the secondary structure of non-histone chromatin proteins HMGB1 and HMGB2
Authors: Chikhirzhina E V , Osinnikova D N , Polyanichko A M
Published: December 2021

The non-histone chromosomal proteins HMGB1 and HMGB2 were found in the cells of all studied eukaryotes. They are involved in cell decision and many biological processes such as replication, transcription, repair, etc. In this work, the secondary structure of the HMGB1 and HMGB2 proteins was studied by the circular dichroism method. It was shown that, despite the high homology between them, the secondary structure of these proteins is different. The revealed structural features, most likely, should influence their functions in the cell nucleus, in particular, the interaction with DNA and other proteins.
Performance characteristics of bistable active ring resonators based on ferrite films
Authors: Vitko V V , Haponchyk R V , Nikitin A A , Ustinov A B
Published: December 2021

A bistability phenomenon in a ring resonator consisting of a delay line on surface spin waves and a microwave amplifier has been experimentally investigated. It is shown that an enhancement of the gain coefficient above a specified value provides an appearance of a hysteresis at the resonator transmission characteristic. A frequency range of the bistability broadens due to an increase of the gain coefficient as well as the external magnetic field. While the value of the gain is limited from above by a transition of the ring into a self-oscillating regime, an increase in the magnetic field from 1150 Oe up to 3150 Oe provides an expansion of the frequency range of the hysteresis from 77 kHz to 185 kHz.
Local stress fields in solids estimated by acoustical emission method
Authors: Hilarov V L , Damaskinskaya E E
Published: December 2021

Based on the Zhurkov’s kinetic concept of solids’ fracture a local internal stress estimation method is introduced. Stress field is computed from the time series of acoustic emission intervals between successive signals. For the case of two structurally different materials the time evolution of these stresses is examined. It is shown that temporal changes of these stresses’ accumulation law may serve as a precursor of incoming macroscopic fracture.
Application of the liquid bridges theory to find the melt menisci shape when growing cylindrical crystals
Authors: Galaktionov E V , Bakholdin S I , Galaktionova N E , Tropp E A
Published: December 2021

A vertical liquid bridge of small volume between a conical shaper and a convex crystallization front was investigated. Two variants of the front crystallization shape selection are considered: a conical and a spherical fronts. A variational statement of the original problem is given. As the boundary conditions we used the condition of engagement at the edge of the shaper and a given growth angle at the crystallization front. The Bond number was assumed to be small, and to find a solution of the problem the asymptotic approach was applied. The calculations are carried out for small diameter cylindrical sapphire crystals, grown from the melt by the Stepanov method. The results of the menisci shapes calculations are presented. The comparison of the results of calculations for conical and spherical crystallization fronts is carried out.
Simulation of pulse wave propagation using one-dimensional models of hemodynamics
Authors: Krivovichev G V , Egorov N V
Published: December 2021

The models of hemodynamics, corresponding to the inviscid, Newtonian, and non-Newtonian models, are compared. The models are constructed by the averaging of the hydrodynamic system on the vessel cross-section. For the inviscid case, the analytical solution of the problem for pulse propagation is obtained. As the result of the comparison, the deviations of the solutions for non-Newtonian models from the Newtonian and inviscid cases are demonstrated.
Investigation of defects in structures based on BP/Si heterojunction
Authors: Maksimova A A , Baranov A I , Uvarov A V , Kudryashov D A , Gudovskikh A S
Published: December 2021

In this work the properties of the BP/Si heterojunction interface were investigated by capacitance methods, the deep levels transient spectroscopy method and admittance spectroscopy. Admittance spectroscopy did not detect any defects, but the deep level transient spectroscopy showed response with activation energy of 0.33 eV and capture cross-section σn=(1-10)·10-19 cm2 and defect concentration (NT) is in the order of 1013 cm-3. This defect level is a trap for electron with position of 0.33 eV below the conduction band in region near the BP/Si interface.
Raman studies of amorphous nanocarbon obtained by laser sputtering
Authors: Eliseyev I A , Smirnov A N , Davydov V Yu , Platonov A V , Yavsin D A , Gurevich S A
Published: December 2021

The structural properties of amorphous nanocarbon films fabricated by laser sputtering of a graphite target are investigated by means of Raman spectroscopy. Analysis of the spectral features in the region of 100–3600 cm-1allowed us to determine the allotrope composition of the films and the degree of disorder in terms of average crystallite size. The results obtained are important for application of such films in the field of electrode coatings.
Ultra-heat resistant nanocomposites based on heterocyclic networks: structure, properties, origin of thermal stability
Authors: Yakushev P N , Bershtein V A , Fainleib A M , Kirilenko D A , Melnychuk O G
Published: December 2021

A series of the hybrid Bisphenol A based Phthalonitrile (BAPhN)/amino-Montmorillonite (amino-MMT) polymer nanocomposites with the complex heterocyclic matrix network and 0.03–5.0 wt.% amino-MMT were synthesized and studied. Their molecular structure, nanostructure, molecular dynamics, thermal, relaxation and elastic properties were characterized using TEM, EDXS, DMA, TGA, FTIR and Far-IR spectroscopies including also the experiments in flowing nitrogen medium. Depending on nanofiller content, different extents of MMT stacks exfoliation, from a single nanolayer to stacks with tens nanolayers-thickness, were registered in these nanocomposites. The exceptional combining of high temperature properties was revealed for these nanocomposites.
Development of self-cleaning SERS-active nanostructures based on ZnO nanorods and Ag nanoparticles
Authors: Novikov D V , Malakhov N S , Tarasov A M , Savitskiy A I , Dubkov S V , Gromov D G , Eganova E M
Published: December 2021

This work demonstrates the possibility of using a combination of zinc oxide nanorods with silver nanoparticles as a self-cleaning SERS substrate. In addition to Raman scattering enhancement such structures demonstrate the self-cleaning effect during UV treatment. The ZnO nanorods (NRs) array was synthesized on a ZnO seed layer by the hydrothermal method. The Ag nanoparticles (NPs) array was formed by vacuum thermal evaporation over the ZnO NRs. Rhodamine-B 230 μM solution has been detected using the formed SERS-substrates without additional mathematical processing of the Raman spectra. Subsequent UV radiation treatment showed a 3-fold decrease in the intensity of the spectral peaks of the analyte.
Study of the electrophysical and gas-sensitive properties of thin ZnO-SnO2 films formed by the sol-gel method
Authors: Starnikova A P , Gulyaeva I A , Storozhenko V Yu , Volkova M G , Bayan E M , Petrov V V
Published: December 2021

Thin films of ZnO-SnO2, with a molar ratio of Zn: Sn = 0:100, 1:99, and 5:95, were synthesized by the sol-gel method. As a result of a study of the electrophysical and gas-sensitive properties of thin ZnO-SnO2 films, the effect of a decrease in the working temperature at low concentrations of zinc oxide was found. The value of the coefficient of gas sensitivity of ZnO-SnO2 films correlates with the activation energy of conduction. For sensor structures based on films with a composition of: 5:95 at a working temperature of 200 °C, a higher gas sensitivity coefficient and the fastest response among all the samples under study are observed.
Elliptic flow for φ-mesons in Cu+Au and U+U collisions
Authors: Mitrankov Iu M , Bannikov E V , Berdnikov A Ya , Berdnikov Ya A , Kotov D O
Published: December 2021

An important goal of current ultra-relativistic heavy ion research is the investigation of the quark-gluon plasma (QGP). Measurements of elliptic flow lend insight on reaction dynamics and are important for defining parameters of viscous hydrodynamic, which can describe QGP behavior. In this paper elliptic flow for φ-mesons in Cu+Au collisions at

s

N
N

=
200

GeV

and in U+U collisions at

s

N
N

=
193

GeV

GeV is studied as a function of kinetic properties and centrality. The obtained results are compared to hydrodynamic model predictions. New FVTX detector and combinations of different approaches of flow measurements provide a possibility to measure the elliptic flow for the φ-mesons for the first time as a function of centrality at PHENIX. The elliptic flow for φ-mesons in Cu+Au and U+U collisions as function of transverse kinetic energy per one quark follows the trend for other hadrons with respect to the number of quarks in hadrons, regardless of centrality. This result along with agreement of obtained data to hydrodynamic model iEBE-VISHNU predictions suggests that QGP can be described with viscous hydrodynamic with specific viscosity η/s = 1/(4π).
Influence of α-particles irradiation on the properties and performance of silicon semiconductor detectors
Authors: Bakhlanov S V , Bazlov N V , Chernobrovkin I D , Derbin A V , Drachnev I S , Kotina I M , Konkov O I , Kuzmichev A M , Mikulich M S , Muratova V N , Trushin M V , Unzhakov E V
Published: December 2021

Deterioration of the operation parameters of p-type Si surface-barrier detector and Si(Li) p-i-n detector upon irradiation by alpha-particles was investigated. The detectors were irradiated at room temperature up to a total number of the registered α-particles Nα
equal to 6 × 109. Prolonged irradiation has resulted in a deterioration of the detectors energy resolution ability and it was found that the increase of α-peaks broadening can be described by a linear function of Nα
with a slope Δσ/ΔNα
∼ (1.4–1.8) × 10–9 keV/α for both detectors. Resolution deterioration was associated with the increase of the detectors leakage current, which proceeds linearly with the number of absorbed α-particles with the slope ΔI/ΔNα ∼ (7-17) × 10-17 A/α. The increase of the detectors reverse current was related with appearance of radiation-induced defect level at 0.56 eV above the valence band.
Optical and structural studies of Hg0.7Cd0.3Te samples grown by various methods
Authors: Andryushchenko D A , Ruzhevich M S , Smirnov A M , Bazhenov N L , Mynbaev K D
Published: December 2021

Photoluminescence and X-ray diffraction (XRD) were used for the studies of the properties of HgCdTe samples with CdTe molar fraction x=0.3 grown by various methods. According to the results of photoluminescence studies, all samples possessed a considerable degree of alloy disorder, yet the scale of the disorder seemed not to be directly related to the structural quality of the material as revealed using XRD. Prospects of using HgCdTe material grown by various methods in optoelectronic devices are discussed.
Influence of attenuation on the generation of optical vortices in multihelicoidal optical fibers
Authors: Alexeyev C N , Alieva S S , Barshak E V , Lapin B P , Yavorsky M A
Published: December 2021

In this paper we have studied influence of attenuation on conversion processes of the fundamental mode (FM) in multihelicoidal optical fibers (MHF) in the vicinity of the point of accidental spectrum degeneracy within the framework of the scalar approximation. To this end, we have obtained expressions for modes of the MHF, which consist of the FM and an optical vortex (OV), and shown that conversion of the FM into the OV takes place. The difference in the attenuation coefficients for the partial fields of MHF’s modes leads to deterioration in the conversion process even with an ideal system’s tuning. At sufficiently large values of attenuation coefficients the conversion of the incoming FM into the vortex vanishes. Also we have shown the presence of exceptional point (EP) in the spectra of modes of the MHF and demonstrated enhanced sensitivity of the fiber in the vicinity of the EP to perturbations.
Influence of small additives of germanium on the physical properties of chalcogenide glasses based on composition As30.5S44.5I25
Authors: Klinkov V A
Published: December 2021

Advanced for the infrared region of the spectrum chalcogenide glass composition As30.5S44.5I25with small germanium additives were investigated. The concentration dependences of some physical and chemical properties indicate an increase in the performance of glasses due to the modification of the glass network. The character of the change in the short-wavelength absorption edge with an increase in the content of germanium atoms had an exponential character, shifting from 597 to 582 nm. A non-monotonic dependences were also found for the values of density, refractive index, and glass transition temperature. A joint analysis of the results obtained and structural studies described in the literature for similar glass systems made it possible to propose possible structural groups of glass compositions under investigation.
NEXAFS study of carbonate substituted bioapatite
Authors: Petrova O V , Bakina K A , Ehrlich H
Published: December 2021

The investigation of unique carbonate substituted bioapatite of Champsocephalus gunnari icefish jaw and skull bones was carried out using NEXAFS spectroscopy. It has been established that these bones contain the B-type carbonate substituted hydroxyapatit with a content [CO3]2- anion of about 0.79-3.07 wt.%.
The research of the composition of mineral component of compact bone tissue after flow delipidation using the optic method
Authors: Timchenko P E , Timchenko E V , Pisareva E V , Vlasov M Y , Frolov O O , Volova L T , Samigullin R T , Sergeeva S S
Published: December 2021

The results of the research of bone mineral component (BMC) composition using the Raman spectroscopy method are presented in the work. The subjects of the research were the groups of BMC samples made of compact bone tissue of cows using “Lyoplast”® technology where vacuum delipidation of initial material was replaced by the flow one by washing it out in hydrogen peroxide and ether. The solution filtration after bone tissue demineralization was used as additional treatment. The results of the experiment show that the flow delipidation can be used for preparing this biomaterial (BMC), which is cost-effective compared to standard vacuum cleaning and additional filtration stage can be rejected.
Fullerite C60 optical constants in the C 1s NEXAFS region
Authors: Sivkov D V , Nekipelov S V , Petrova O V , Bogachuk D V , Skandakov R N , Sivkov V N
Published: December 2021

Using data on the absorption cross sections the refraction coefficient spectral dependence n(E) and the spectra of the remaining optical coefficients (reflection coefficient, phase shift, and atomic form factor) in the fullerite C60 C 1s near edge X-ray absorption fine structure (NEXAFS) region (280–350 eV) were determined. For the n(E) calculations the Kramers-Kronig integral relations (KKRs) were used. The KKR computations were performed using data on atomic carbon absorption cross sections in the 10–30000 eV range and on solid and gaseous C60 – in the 0–120 eV. Absorption cross section spectrum in the fullerite C60 C 1s NEXAFS region were measured.
Investigation of spectral properties of potassium-aluminum-borate glass with CuCl - CuBr nanocrystals
Authors: Babkina A N , Zyryanova K S , Egorova Y B , Kulagina A S , Gavrilov R R , Monogarova A A
Published: December 2021

Heat treatment conditions effect on the characteristics of exciton absorption and luminescence of CuCl and CuBr nanocrystals in potassium-aluminaborate glass is studied. The size effect of the band edge absorption and luminescence energy is confirmed. The simultaneous presence of copper halide nanocrystals and free monovalent copper ions in the glass matrix is shown. Possible conditions for the formation of mixed CuCl-CuBr crystals are considered.
Spectral Fourier-microscopy of the periodic structures based on Ge2Sb2Te5
Authors: Solomonov A I , Pavlov S I , Lazarenko P I , Kovalyuk V V , Golikov A D , Prokhodtsov A I , Goltsman G N , Kozyukhin S A , Dyakov S A , Gippius N A , Tikhodeev S G , Pevtsov A B
Published: December 2021

The method of spectral Fourier microscopy was used to study the reflection spectra with an angular resolution of submicron periodic gratings based on amorphous and crystalline Ge2Sb2Te5. The form of the dispersion curves of quasi-waveguide modes in the structures under study was established. The experimental data were compared with the calculations of dispersion curves in synthesized diffraction gratings. Reasonable agreement between theoretical and experimental data was obtained.
The model of degradation of an InGaN/GaN LED during current tests taking into account the inhomogeneous distribution of the defects density in the heterostructure
Authors: Frolov I V , Hodakov A M , Sergeev V A , Radaev O A
Published: December 2021

A model of the optical power degradation of an InGaN/GaN LED during testing under direct current, which takes into account the inhomogeneous distribution of the defects density in the heterostructure, is presented. According to the simulation results, the rate of degradation of the LED optical power significantly depends on the degree of inhomogeneity of the defects density distribution profile. Experimental testing of the model has been carried out. The proposed model makes it possible to predict the rate of degradation of InGaN-based LEDs with varying degrees of inhomogeneity of the defects density distribution profile and can be used to develop a technique for rejecting defective and potentially unreliable LEDs.
Induced electronic phenomena in crystals of p-GaSe semiconductor promising for optoelectronics
Authors: Babayeva R F
Published: December 2021

An induced impurity photoconductivity by the electric field, thermally stimulated conductivity and spontaneous pulsations of the dark current were found in the undoped (with a dark resistivity P77≈3•104÷108 Ω-cm at T≈77 K) and erbium doped (NEr=10–5÷10–1 at.%) p-GaSe crystals in the temperature range of T≤240÷250 K at electric field strengths (E) creating a noticeable injection. It was found that the value of the observed impurity photoconductivity (M) monotonically increase at low illumination in undoped crystals with increasing P77 and its spectrum smoothly expands towards longer waves. The value of ∆ii
and the width of its spectrum change non-monotonically with increasing NEr
in doped crystal and it gets its maximum value at NEr
≈5•10-4 at.%. The intensity of spontaneous pulsations increases with increasing E at the higher electric field strengths. However, the impurity photoconductivity and the peak of thermally stimulated conductivity gradually disappeared. The amplitude and frequency of the observed spontaneous pulsations of the dark current is increased with increasing in the injection ability of the contacts. Moreover, the pulsations of the dark current gradually disappeared with increasing T. It was shown that all these three phenomena are directly caused by the recharge of sticking levels with a depth
Er
≈+0.42 eV and a density Nt≈ 1015 cm-3 by injected holes. However, in high-resistance undoped and doped
Er

≤10-2 at.% crystals, it is also necessary to consider the presence of random macroscopic defects in the samples to explain their features. A qualitative explanation is proposed based on the obtained results.
Plasma semiconductor antenna
Authors: Brusentsev A S , Bogachev N N , Dogaev S G , Yu Kazantsev S , Sattarova A I , Titovets P A
Published: December 2021

The purposes of this work was to study the possibility of using photoconductive semiconductor antenna based on Ge or GaAs for receiving information signals in the frequency communications and satellite navigation bands and to study a scattering parameter S11 – a return loss (a reflection coefficient) of configurable loop antennas with laser-plasma control based on semiconductor photoresistor. It is shown that the addition of semiconductor photoresistor element in the loop antenna makes it possible to significantly expand its functionality and control its characteristics using an external laser source.
Piezostack deformable mirror with high technological effectiveness
Authors: Toporovsky V V , Kudryashov A V , Samarkin V V , Panich A A , Sokallo A I , Yu Malykhin A
Published: December 2021

Deformable mirror (DM) is an active element that can change the shape of the surface to compensate for wavefront aberrations. Historically, the development of DMs started from piezostack deformable mirrors (PDM) due to their large stroke, flexibility in actuators geometry, high resonant frequency. However, the cost of PDMs is comparatively high because of their labor-intensive process of manufacturing. In the article innovative design of PDM is presented. The assembling of unconventional PDMs was carried out using piezoceramic combs. This step should allow to decrease number of technological steps, increase spatial resolution of the mirror and thereby reduce the cost of final product.
Influence of QD array positioning in GaAs solar cell p-n junction on their photoelectric characteristics
Authors: Salii R A , Mintairov M A , Mintairov S A , Nakhimovich M V , Shvarts M Z , Kalyuzhnyy N A
Published: December 2021

In the work, the effect of In0.8Ga0.2As quantum dots position in the i-region of a GaAs solar cell on its spectral and photoelectric characteristics has been investigated. Three solar cell structures were obtained by metal-organic vapor-phase epitaxy, in which layers of quantum dots were placed in the middle of the i-region and also have been shifted to the base and the emitter. As a result, it has been shown that the solar cell with a quantum dot array shifted to the base demonstrates the smallest open-circuit voltage drop and, accordingly, a higher efficiency value.
Current—voltage characteristics of connecting tunnel diodes at temperature heating up to 80°C
Authors: Kontrosh E V , Klimko G V , Kalinovskii V S , Yuferev V S , Vaulin N V , Ya Ber B
Published: December 2021

Investigations of the temperature stability of the peak tunneling current density of connecting tunneling diodes, which are necessary for the creation on their basis of multijunction photoconverters of powerful optical radiation, have been carried out. The structures of n++-GaAs/i-GaAs/i-AlGaAs/p++-AlGaAs of connecting TD with an intermediate undoped layer thickness of 7.5 nm and a growth temperature of 500 °C (structure ”A”) and with a thickness of 10 nm and a temperature of 450 °C (structure ”B”) were investigated. When heated to 80 °C, an increase in the peak tunneling current density of the TD structure ”B” by 4% is observed. However, for structure ”A”, a decrease in the peak tunneling current density by 5% with heating is observed. The factors leading to the appearance of a negative or positive temperature coefficient of the peak tunneling current density are determined using mathematical modeling of tunneling diodes based on GaAs/AlGaAs materials. By reducing the epitaxial growth temperature of n++–GaAs/i-GaAs/i-AlGaAs/p++–AlGaAs tunnel diode structure to 450 °C and including an undoped i-layer 10 nm thick between the degenerate layers ensure the temperature stability of peak current density when heated to 80 °C.
Detection of oscillatory solutions in a vacuum diode with total electron reflection
Authors: Kuznetsov V I , Morozov IK
Published: December 2021

Stability features of steady-state solutions for a vacuum diode with complete deceleration of electron beam is studied. A boundary line on the (inter-electrode gap, external voltage)-plane separating stable solutions from unstable ones is built up. An instability development is shown to end in a state with non-linear oscillations of the electric field but with no virtual cathode in a plasma. Existence of non-linear oscillations of the electric field in a vacuum diode with total reflection of an electron beam points out that such a diode can be a basis to create microwave generator.
Features of flow around transport aircraft model with running propellers by modelled engine failure in wind tunnel
Authors: Chernousov V I , Krutov A A , Pigusov E A
Published: December 2021

This paper presents the experiment results of modelling the one engine failure at the landing mode on a model of a light transport airplane in the T-102 TsAGI low speed wind tunnel. The effect of starboard and port engines failure on the aerodynamic characteristics and stability of the model is researched. The model maximum lift coefficient is reduced about ≈8% and there are the same moments in roll and yaw for starboard and port engines failure case. It was found that the failure of any engine has little impact on the efficiency of control surfaces. Approaches of compensation of forces and moments arising in the engine failure case were investigated.
Numerical analysis of the flow in the model of a venous valve: normal and surgical corrected
Authors: Gataulin Y A , Yukhnev A D , Rosukhovskiy D A
Published: December 2021

The present study aimed to modeling of surgically corrected venous valve. The Arbitrary Lagrangian-Eulerian (ALE) method was used to model the blood–leaflet interactions. The contact process between leaflets was evaluated using a frictionless contact method. The results of the numerical study of the flow in the venous valve after extravasal correction was compared with the results for the normal venous valve.
Suppression of relaxation of higher polarization moments of alkali atoms in superfrequent spin-exchange collisions
Authors: Okunevich A I
Published: December 2021

Consideration of nonlinear spin-exchange equations showed that, in addition to the well-known suppression of the relaxation of the transverse orientation of atoms in a low magnetic field, relaxation of higher polarization moments (alignment, octupole, hexadecapole, etc) are also suppressed. Such suppression of relaxation is caused by the conservation of the transverse angular momentum of atoms in collisions.
Molecular mobility in bulk and in near-surface nano-layers of ultra-high-molecular-weight polyethylene
Authors: Siklitsky V I , Gladkov A K , Ivan’kova E M , Lebedev D V , Myasnikova L P , Marikhin V A , Solov’eva O Yu
Published: December 2021

A comparative study of molecular dynamics in near-surface nanolayers and in a bulk of polyethylene is presented. Molecular mobility in near-surface nanolayers of polyethylene reactor powders and melt-crystallized films of various molecular weights prepared in different crystallization conditions were studied with the help of thermoluminescence technique using high frequency glow dicharge Ar plasma for surface activation. Molecular mobility in a bulk of the same samples was investigated by the method of radio thermoluminescence, in which a deeply penetrating γ-quanta from 60Co radiation was used for activation of the bulk. A marked difference in a temperature position of the peaks on the glow curves of plasma-induced thermoluminescence and those of radiothermoluminescence correspoding to γ- and ß-transitions was found to depend on crystallisation conditions and molecular weight. Quasi-independent segmental mobility (ß-relaxation) in the near-surface nano-layers of UHMWPE reactor powder particles synthesized at low temperatures appeared to be unexpectedly unfreezed at the temperature higher than that in the bulk. It was supposed that this happend because of crystallization under the confinement conditions during low-temperature polymerization leads to formation of a specific surface structure.
Mechanical Properties of Particleboard using Acacia Mangium Wood Particles Binded With Seaweed-Based Adhesives
Authors: Liew K C , Samin A R
Published: December 2021

The purpose of this study was to evaluate the mechanical properties of particleboards made from Acacia mangium wood particles binded with three different types of seaweed-based adhesive. Red seaweed (RS), brown seaweed (BS) and green seaweed (GS) were used as the seaweed-based adhesives., while particleboard using urea formaldehyde (UF) adhesive was produced as control. Adhesives and wood particles were mixed and then undergone mat-forming, pre-pressing, hot-pressing and conditioning process. The test pieces for bending test (Modulus of Elasticity, MOE; Modulus of Rupture, MOR), and internal bonding strength (IB) were cut into size according to JIS A 5908: 2003. From mechanical properties results attained, for internal bonding strength test, all boards using RS, BS and GS adhesives were found to be significantly different at p≤0.05. Apart from that, RS adhesive showed highest MOE and MOR at 529.4259 N/mm2 and 1.7900 N/mm2, respectively. As a conclusion, the mechanical properties of particleboard using RS, BS, and GS adhesives showed RS stands out as the better adhesive among them which have significant effects on its strength.