bluuebunny/crossref_metadata_2025 huggingface dataset:
RUKYATUL HILAL INSTRUMENT DESIGN BASED ON ARDUINO
Authors: Fajrullah Fajrullah , Hadi Zikrullah , Nisastra Andi Evan
Published: September 2022

Arduino is a Microcontroller platform consisting of a computer chip that is used to control electronic equipment that is flexible and easy to use. In this modern era, the implementation of Rukyatul Hilal can be done using instruments such as Hilal locater, telescope and theodolite. However, these tools are quite expensive and have a fairly heavy load and require long time to prepare. Therefore, this research provides breakthroughs and new innovations in designing the Rukyatul Hilal Instrument based on Arduino. The research uses the Research and Development model type of research, the development model that the researcher will do is to develop an Arduino Microcontroller so that it can be used as a Rukyatul Hilal Instrument. Based on 4 observations of the Moon, The Arduino-based Rukyatul Hilal instrument can successfully show the position of the Moon and verify the data used by the author is correct and the author can also photograph the image of the Moon clearly using a smartphone. However, it should be noted that the position of the Moon when viewed from the Arduino-based Rukyatul Hilal Instrument telescope is not in the middle of the telescope, but sometimes at the bottom, side and top.
AHMAD GHAZALI'S THOUGHTS IN THE BOOK OF ANFA' AL-WASĪLAH ON DETERMINING ‘ASR TIME PRAYER
Authors: Makhturoh Siti , Shabir Muslich , Izzuddin Ahmad
Published: September 2022

Ḥanafī's opinion differs from that of Al-Shāfi’ī in determining the entry of the time for the 'Asr prayer and the time for the Isha prayer. These two different determinations can be easily identified using the contextual method (calculation). The data needed in calculation is the high value of the Sun, so the thought of Ahmad Ghazali, an astronomer from Madura, explained about the height of the Sun based on two schools of thought. This provides a treasure of knowledge to someone in determining the entry of prayer times based on madhhab, just by looking at the clock. The type of method used in this study is qualitative field research with a descriptive approach, the aim is to describe Ahmad Ghazali's thoughts and to analyze in the field the given method. The results of the Anfa’ al-Wasīlah calculation with the addition of 1 in the irtifā’ formula is in accordance with the opinion of Al-Shāfi’ī, and an additional 2 in the irtifā’ formula according to the opinion of Ḥanafī, while from Ahmad Ghazali's opinion it states that the two early determinations of the time for the Asr prayer This is true, but it is more appropriate to use the ‘Aṣr Awwal time, because the ‘Aṣr Awwal opinion is supported by a number of scholars and strong arguments.
brincar possível em tempos de isolamento
Authors: Lima Aline Patricia Campos Tolentino de , Andrade Joana de Jesus de
Published: September 2022

Este estudo busca investigar o desenvolvimento das funções psíquicas superiores da memória e da imaginação no momento da brincadeira de faz de conta. A pesquisa está fundamentada na Psicologia Histórico-Cultural que contempla o desenvolvimento das funções psíquicas superiores, considerando que o processo de desenvolvimento cultural da criança é o alicerce para a constituição das funções psíquicas. Partindo desse referencial teórico, a pesquisa, de cunho qualitativo, foi realizada com os seguintes recursos metodológicos: investigação participativa e a observação. Com este estudo, foi possível ampliar a discussão teórica sobre como se constituiu a brincadeira de faz de conta mesmo em um momento de isolamento e distanciamento social no cotidiano da Educação Infantil, contribuindo para o desenvolvimento da memória e da imaginação.
“Eu não tenho cara de estudante de medicina”
Authors: Fernandes Natália Rigueira , Oliveira Breynner Ricardo de
Published: September 2022

O artigo analisa a trajetória de um estudante de camada popular, as interações com guichês discriminantes em uma universidade pública mineira e suas percepções sobre seu cotidiano como estudante-alvo de políticas sociais. A partir de uma abordagem qualitativa, realizou-se uma entrevista-narrativa, contemplando quatro dimensões: (1) sua trajetória familiar e escolar antes do ingresso na universidade; (2) estratégias e percepções sobre políticas de inclusão social que contribuíram para seu ingresso na universidade; (3) sua experiência como estudante de Medicina e as interações com os pares; (4) sua interação com os setores na universidade, nos seus guichês. Os resultados indicam mudança no perfil socioeconômico nas universidades públicas a partir do governo Lula e o ingresso dos “estudantes improváveis”, por meio da Lei de Cotas e outras políticas destinadas às famílias. Revelam, também, guichês discriminantes e estigmas que se processam, a partir da reprodução de desigualdades no processo de implementação de políticas.
la docencia presencial a la docencia virtual
Authors: Braz Marcelo , Moneo Sergio , Lleixà Teresa
Published: September 2022

El presente artículo aborda el tema de la docencia en la formación del profesorado de Educación Física en tiempos pandémicos, de la Covid-19, en España. Para eso, nos ocuparemos de reflexionar sobre las estrategias metodológicas alternativas a las clases de práctica físico-deportiva, en el paso de la docencia presencial a la docencia no presencial o semi presencial. Tres serán los temas clave en la fundamentación: a) El conocimiento práctico en la formación del profesorado de Educación Física; b) Los entornos virtuales y tecnologías de la información y la comunicación en la formación del profesorado de Educación Física; c) La Educación Física escolar en tiempos de Covid-19. Para finalizar, hemos realizado una reflexión con respecto a la subjetividad de la actividad docente en tiempos pandémicos.
Estar presente é estar incluído? Análise de situações em que a inclusão escolar não acontece
Authors: Martins Bárbara Amaral , Chacon Miguel Claudio Moriel
Published: September 2022

Estudantes público da Educação Especial devem frequentar, preferencialmente, escolas regulares de ensino. Apesar dos avanços em termos legislativos e de matrículas, nem sempre a inclusão escolar acontece, verdadeiramente, no interior das instituições escolares. Por isso, objetivamos descrever e analisar situações de sala de aula em que a inclusão escolar não acontece de fato. Participaram 16 professoras e 22 alunos público da Educação Especial matriculados em escolas públicas de Corumbá e Ladário em Mato Grosso do Sul. Os dados foram coletados por meio de filmagens e analisados a partir do Protocolo de Observação de Situações Educacionais Inclusivas. Quatro situações de sala de aula foram consideradas não inclusivas e revelaram a falta de atenção individualizada das professoras aos estudantes público da Educação Especial, ausência de flexibilização curricular, oferecimento de atividades desvinculadas do trabalho desenvolvido pelos demais alunos e falta de respostas pedagógicas condizentes com o nível de desenvolvimento desses discentes.
Governance enigma: Concerns and human security challenges to Pakistan
Authors:   Political Science Department, Government College Women University Sialkot, Punjab, Pakistan, et al. Yaseen
Published: September 2022

This study explains the concept of good governance in Pakistan and discusses the issues and challenges of governance in Pakistan and the expectations of the people from the setup. This work also estimates the past and present status of governance in Pakistan and proposes an idea for a fruitful and successful future. Good governance in Pakistan is probably ideal governance because its goals are difficult to achieve. Pakistan must control its shortcomings such as corruption, poor accountability and nepotism, lack of accountability, and mismanagement through the legislative framework to make sure good governance. This opinion has been reached with the help of the Normative Model of Governance.
Numerical higher-order Runge-Kutta methods in transient and damping analysis
Authors:   Department of BS & RS, QUEST, Nawabshah, Pakistan, et al. Shaikh
Published: September 2022

Transient analysis of an RLC circuit (or LCR circuit) comprising of a resistor, an inductor, and a capacitor are analyzed. Kirchhoff’s voltage and current laws were used to generate equations for voltages and currents across the elements in an RLC circuit. From Kirchhoff’s law, the resulting first-order and second-order differential equations, The different higher-order Runge-Kutta methods are applied with MATLAB simulations to check how changes in resistance affect transient which is transitory bursts of energy induced upon power, data, or communication lines; characterized by extremely high voltages that drive tremendous amounts of current into an electrical circuit for a few millionths, up to a few thousandths, of a second, and are very sensitive as well important their critical and careful analysis is also very important. The Runge-Kutta 5th and Runge-Kutta 8th order methods are applied to get nearer exact solutions and the numerical results are presented to illustrate the robustness and competency of the different higher-order Runge-Kutta methods in terms of accuracy.
Emission spectra of molecular gases CHF-=SUB=-3-=/SUB=-, CCl-=SUB=-2-=/SUB=-F-=SUB=-2-=/SUB=-, SF-=SUB=-6-=/SUB=- in the range 3-20 nm under pulsed laser excitation using various gas jets as targets
Authors: Guseva V. E.  , Nechay A. N.  , Perekalov A. A.  , Salashchenko N. N.  , Chkhalo N. I.
Published: September 2022

The article considers the results of studies of the emission spectra of CHF3, CCl2F2, SF6 upon excitation by pulsed laser radiation. We used Nd : YAG laser, λ = 1064 nm, tau = 5 ns, and Epulse = 0.8 J. The spectral range of 3-20 nm was studied. We used capillary and supersonic conical nozzles with dcrit = 145 μm, 2α = 12o, L = 5 mm, and dcrit = 450 μm, 2α = 11o, L = 5 mm to form an atomic cluster beam. The emission spectra for various gas targets were obtained, the obtained spectra were deciphered, and the ions emitting in this spectral range were determined. We observed that with increasing particle concentration in the zone of laser spark, the radiation intensity increases. In this case, the intensity of ion lines with high degrees of ionization increases faster. Keywords: cluster beams, extreme ultraviolet radiation, emission spectra, laser spark, x-ray spectrometer-monochromator.
Luminescence of boron difluoride ditoluoylmethanate. Formation of J-aggregatess
Authors: Mirochnik A. G.  , Fedorenko E.V.  , Beloliptsev  A. Yu.
Published: September 2022

The processes of the formation of J-aggregates during the dissolution 2,2-difluoro-4,6-di(4'-methylphenyl)-1,3,2-dioxaborine crystals ( 1) and their subsequent dissociation have been studied by absorption and luminescence spectroscopy and quantum-chemical modeling. It is shown that two luminescent centers are observed in the solution 1: monomeric luminescence and luminescence of J-aggregates (dual luminescence). Evolution of absorption, excitation and luminescence spectra is observed over time, indicating a slow dissociation of J-aggregates. Keywords: luminescence, absorption spectra, boron difluoride complexes, J-aggregates.
Optical and photoluminescent properties of the thin film zinc oxide on the LiTaO-=SUB=-3-=/SUB=- substrate
Authors: Grigoryev L. V.  , Semenov A. A.  , Mikhailov A. V.
Published: September 2022

Presents the results of the study of the structural, optical and photo luminescent properties of the thin films ZnO on LiNbO3 substrate. The results of X-ray structural analysis of a zinc oxide film synthesized on a single-crystal LiTaO3 substrate and on a KU-1 quartz substrate are presented. Present the transmission spectra, reflection spectra and the spectral dependence of zinc oxide thin films on substrate LiTaO3 and the structure of ZnO-SiO2 in the ultraviolet and visible spectral ranges. Keywords:zinc oxide, laser ablation, ferroelectric materials, X-ray structural analysis, atomic-force microscopy surface, photoconductivity, method Tikhonov-Lavrentiev regularization.
Investigation of dielectric functions of a layer of Ag nanoparticles on silicon using spectro-ellipsometry and spectrophotometry
Authors: Tolmachev V. A.  , Zharova Yu. A.  , Ermina A. A.  , Bolshakov V.O.
Published: September 2022

An investigation of the optical characteristics of a layer of Ag nanoparticles deposited from an AgNO3 solution on the surface of single-crystal Si is presented. The measurements were carried out using spectroscopic ellipsometry and spectrophotometry at the same tilt angle and sample probe location in a wide spectral range from 200 to 1700 nm. From the obtained experimental data, the parameters of the Drude-Lorentz model and the complex dielectric function were determined, which was compared with the pseudo-dielectric function. Both dependences revealed resonances of a bulk plasmon near the energy E = 3.8 eV, while a localized plasmon was detected in the pseudo-dielectric function at E = 1.65 eV, and in the dielectric function at E = 1.84 eV. Keywords: dielectric function, Drude-Lorentz model, silver nanoparticles, plasmon, pseudo-dielectric function, spectrophotometry, ellipsometry
Luminescent chemosensor for detecting dimethylamine and ammonia vapors
Authors: Shishov A. S.  , Mirochnik A. G.
Published: September 2022

The interaction of tris-dibenzoylmethanate Eu(III) with dimethylamine and ammonia vapors was investigated. It was found that when vapors of aqueous solutions of analytes are exposed to tris-dibenzoylmethanate Eu(III) impregnated into the SiO2 matrix, an optical response is observed in the form of an increase in the luminescence intensity of Eu(III). Changes in the luminescence spectra and luminescence excitation of this sensor are analyzed, both under the quenching action of water vapor and under the sensitizing action of analyte vapors. The main points recorded in the excitation spectra are noted, which are important for understanding the processes occurring in the near environment of the lanthanide center. The luminescent chemosensor is promising for creating sensors for detecting ammonia and amines in food safety control and environmental monitoring. Keywords: europium(III), beta-diketonates, luminescence, ammonia, dimethylamine, sensors.
Spectral response of a microresonator containing a double quantum dot modified by Coulomb interaction of localized electrons
Authors: Tsukanov A. V.
Published: September 2022

A theoretical model of a semiconductor nanostructure consisting of a single-mode microresonator containing two quantum dots is considered. It is shown that the Coulomb interaction between electrons localized in the quantum dots modifies a spectral response of the system to an external laser field. The possibility of its use for detecting an elementary charge in the third (optically inactive) quantum dot is discussed. The influence of both diagonal (Stark effect) and non-diagonal (Foerster effect) Coulomb matrix elements of the Hamiltonian on the detection accuracy is studied. The dependences of a measuring contrast on the parameters of the resonator and the quantum dots are calculated. The existence of such structural configurations for which the contrast retains an optimal value even at large distances to the measured dot is established. Keywords: quantum dots, microresonators, nanophotonics, semiconductors, laser, measurement
Luminescence of colloidal quantum points Ag-=SUB=-2-=/SUB=-S/SiO-=SUB=-2-=/SUB=-, decorated by small nanoparticles Au
Authors: Grevtseva I. G.  , Ovchinnikov O. V.  , Smirnov M. S.  , Kondratenko T. S.  , Perepelitsa A. S.  , Hussein A. M. H.
Published: September 2022

Ten-fold increase in quantum yield of defect luminescence was found in area 750 nm with simultaneuous growth of its attenuation from 4 to 200 ns, caused by decoration of quantum point (QP) Ag2S/SiO2 (5.0±1.5 nm) surface with nanoparticles (NP) Au (2.0±0.5 nm). Based on analysis of luminescence kinetics at 77 and 300 K the conclusion was drawn on non-specific manifestation of plasmon-exiton interaction caused by polarization effects from NP Au at properties of small traps that participate in generation of defect luminescence kinetics of QP Ag2S/SiO2. Keywords: IR luminescence; luminescence attenuation kinetics; quantum points, plasmon nanoparticles, plasmon-exiton interaction.
Study of features in recording of optical response from X-ray luminophores for X-ray photodynamic therapy
Authors: Medvedev P.S.  , Pankin I. A.  , Soldatov M. A.  , Polozhentsev O. E.  , Soldatov A.V.
Published: September 2022

A description is given of a facility to study optical response of X-ray luminophores considered as a component of composite materials for X-ray photodynamic therapy. The concept and basic principles of X-ray photodynamic therapy are presented. Test results of the developed facility are presented, methods of optimizing the signal/noise ratio by varying the parameters of the X-ray source and optimizing the experiment geometry are discussed. Examples of measuring X-ray excited luminescence signal for concentrated powdered samples and diluted samples in the form of colloidal solutions are discussed. Keywords reactive oxygen species, photosensitizer, energy transfer.
Quantization of the spectrum of spinon pairs in a magnetic field and formation of bosons in the form of fragments of 1D-waves of charge/spin density in SmMnO-=SUB=-3+delta-=/SUB=-
Authors: Bukhanko F. N  , Bukhanko A. F.
Published: September 2022

Quantum oscillations of the temperature dependences of magnetization of SmMnO3+delta in magnetic fields H=100 and 350 Oe, 1 and 3.5 kOe are studied within a temperature interval of 4.2-12 K. The continuum of thermal excitations of spinon pairs in magnetic field H=100 Oe is divided into three overlapping Landau bands with energies En (n=1,2,3) and fractional band filling factors ν. The symmetric intense "supermagnetization" doublet consisting of two overlapping peaks around mean excitation temperature Tspinon=~8 K produces the primary contribution to magnetization. As the field increases to H=1 kOe, the spinon excitation spectrum transforms into a broad sinusoid peak with its apex around Tspinon=~8 K, which is typical of the excitation continuum of spinon pairs with strong dispersion in the regime of their confinement. The thermal excitation spectrum of spinons changes significantly in magnetic field H=3.5 kOe: a new type of quantization of the spinon spectrum in the form of magnetization features shaped like narrow steps (plateaus), which correspond to integer filling with spinons of three Landau bands with a finite gap, emerges in Landau bands with n=1,2, and 3. The evolution of the boson spectrum in the form of thermal excitations of gapless quasi-one-dimensional waves of charge/spin density in the Luttinger liquid at temperatures below 60 K is examined. A continuous quantum phase transition of the quantum spin liquid into the Luttinger liquid state induced by an increase in the magnetic field intensity is found at temperatures around T=0. This transition has features typical of the formation of 1D-waves of charge/spin density induced by the confinement of spinon pairs and is accompanied by strong field hysteresis. Keywords: quantum spin liquid, Luttinger liquid, confinement of spinon pairs, spinon --- gauge field system, landau quantization, 1D-waves of charge/spin density, quantum oscillations.
Nuclear spin dynamics and noise in anisotropic large box model-=SUP=-*-=/SUP=-
Authors: Shumilin A. V.  , Smirnov D. S.
Published: September 2022

We consider the central spin model in the box approximation taking into account external magnetic field and anisotropy of the hyperfine interaction. From the exact Hamiltonian diagonalization we obtain analytical expressions for the nuclear spin dynamics in the limit of many nuclear spins. We predict the nuclear spin precession in zero magnetic field for the case of anisotropic interaction between electron and nuclear spins. We calculate and describe the nuclear spin noise spectra in the thermodynamic equilibrium. The obtained results can be used for the analysis of the nuclear spin induced current fluctuations in organic semiconductors. Keywords: central spin model, box model, nuclear spin dynamics.
Magnetic interactions in Aurivillius phase Bi-=SUB=-5-=/SUB=-FeTi-=SUB=-3-=/SUB=-O-=SUB=-15-=/SUB=- structure
Authors: Yastrebov S. G.  , Lomanova N. A.
Published: September 2022

This paper analysis the temperature dependence of FC and ZFC magnetization for Bi5FeTi3O15 multiferroic. It has Aurivillius four-layer phase structure. The analysis evidence on the influence of the grains of this material on its overall magnetic properties. The lack of a dramatic temperature threshold in the FC(ZFC) dependences may result in spin canting induced by the Dzyaloshinskii--Moriya interaction. Keywords: Aurivillius phases, perovskites, magnetic properties.
The phase composition and structure of the BiFeO-=SUB=-3-=/SUB=- film grown on MgO(001) substrate by high frequency cathode deposition in oxygen atmosphere
Authors: Pavlenko A.V.  , Stryukov D. V.  , Kubrin S.P.
Published: September 2022

The crystal structure and Mossbauer spectroscopy studies results for BiFeO3 film growth on the MgO(001) single crystal substrate are present in the paper. It been shown that film have high crystal perfection and low defectiveness which results in appearing of narrow lines during the theta-2theta and φ scanning and the small (lower than 0.7o) disorientation of film and substrate crystal axes. It is been revealed that unit cell of BiFeO3/MgO(001) heterostructure possess monoclinic symmetry and deformation of unit cell is negligible. The Mossbauer study shows that magnetic subsystem of film has spatial spin-modulated structure with zero value of anharmonicity parameter (m). This indicate that at room temperature the magnetic anisotropy changes from the "easy axis" type to "easy plane" type. Keywords: thin films, bismuth ferrite, Mossbauer effect.
Features of dependence of Raman spectra of cluster structures of three-dimensionally polymerized fullerite on pressure
Authors: Khorobrykh F.S.  , Churkin V.D.  , Popov M.Yu.
Published: September 2022

We study the effect of high hydrostatic pressure on 3D polymerized fullerite C60. We do not observe further structural changes until 150 GPa after a formation of 3D C60 under hydrostatic pressure 28 GPa. It is experimentally shown that the obtained samples consist of different clusters formed by sp3 bonds with a different set of force constants, the values of which vary within 20% and exceed the diamond force constants by the factor of 1.3-1.5. The influence of the exposure of laser radiation on the process of 3D polymerization of C60 under pressure was found. Increasing of the exposure by the factor of 15 leads to a decrease in the bulk modulus of 3D C60 from 610 GPa to 504 GPa. Keywords: bulk modulus, ultrahard fullerite, high pressures, Raman spectroscopy.
Investigation of the influence of weak magnetic fields on thermodynamic properties of the Potts model with the number of spin states q=4 on a hexagonal lattice
Authors: Ramazanov M. K.  , Murtazaev А. K.  , Magomedov M. A.  , Mazagaeva M. K.  , Dzhamaludinov M. R.
Published: September 2022

The replica exchange algorithm of the Monte Carlo method was used to study phase transitions and thermodynamic properties of the two-dimensional Potts model with the number of spin states q=4 on a hexagonal lattice in weak magnetic fields. The studies were carried out for the interval of the magnetic field value 0.0≤ H≤3.0 with a step of 1.0. It is found that a first-order phase transition is observed in the considered range of field values. Keywords: Frustration, Phase transitions, Monte Carlo method, Potts model.
Thermodynamics and kinetics of elastic calorific effect in shape memory alloys
Authors: Malygin G. A.
Published: September 2022

The mechanism of elastic calorific effect in crystals of alloys with SME is theoretically discussed within the framework of the theory of diffuse thermoelastic martensitic transitions, that the structural transitions in alloys with shape memory effect (SME) are. The theory provides an adequate description of the elastic calorific effect under adiabatic unloading of the crystal and stable behavior of the martensitic transition. Flexibility of the theory is also applicable to kinetically unstable (with a burst) martensitic transitions caused by structural features of the crystal, as is the case, according to literature, of Ni50Fe19Ga27Co4 alloy crystal compression along the direction of [011]. Key words: alloys with SME, elastic calorific effect, thermoelastic martensitic transitions, stable and unstable kinetics of martensitic transition.
To the model description of electronic spectrum for the graphene-like Janus structures
Authors: Davydov C. Yu.
Published: September 2022

Model of C-AB-D Janus structure as the compound formed by the interacting through atoms A and B dimers A-C and B-D, where A and B atoms are in the sites of two-dimensional hexagonal lattice and C and D atoms are on the opposite sides from AB list is proposed. In the scope of tight-binding theory and Green's function method general equation for the dispersion low is obtained. The particular cases of C-AA-D and A-AB-B compounds are considered and analytical expressions for their electronic spectra is fulfilled. The effect of the external mechanical deformation on the band parameters including effective masses is examined. Problem of the magnetic states in Janus compounds is discussed. Keywords: model of interacting dimers, electronic spectrum, effect of deformation, magnetic states.
Structural transition in cellulose triacetate films
Authors: Novikov D.V.
Published: September 2022

Electron microscopy data are used to comparative analysis of the topological structure of the surface of two samples of cellulose triacetate (CTA) films. The samples were obtained from CTA solutions without use (sample N 1) and with the use of a small sodium fluoride additive that lowers the viscosity of the solution (sample N2). It is shown that in sample N 1, the nodes of the physical network of macromolecules are periodically alternating regions of local orientation order --- microdomains of average size d~18 nm. In sample N 2, due to repackaging of microdomains on the scale R>d, a uniformly disordered fractal cluster of the mesophase CTA is formed. The fractalization of the surface and the growth of structural anisotropy are consistent with the decrease in the viscosity of the solution and explain the change in the deformation properties of sample N 2 compared to N 1. Keywords: polymer films, electron microscopy, microdomains, mesophase, structural transition, fractal clusters.
Estimation of the influence of icosahedric "magic" numbers of thermal stability of small silver nanoclusters
Authors: Ryzhkova D. A.  , Gafner S. L.  , Gafner Y. Ya.
Published: September 2022

A comparative analysis of thermally induced structural transitions in silver nanoclusters, the number of atoms of which corresponded to the "magic" numbers of the icosahedral (Ih) structure with variation of their initial morphology, was carried out by the molecular dynamics method using the modified tight-binding potential TB-SMA. It is shown that, in the case of the initial fcc phase, the formation of the Ih modification, depending on the particle size, occurred either at the stage of preliminary thermal relaxation or during further heating. At the initial amorphous morphology, the nature of the structural transitions underwent significant changes. Thus, even in the case of Ag55 clusters, the icosahedral structure was formed only in 50-60% of the experiments performed. Based on the data obtained, it was concluded that to create a stable Ih structure, it is necessary to use the thermal cycling procedure. Keywords: nanoclusters, silver, computer simulation, "magic" numbers, structure of nanoclusters.
Non-Heisenberg ferrimagnet with single-ion anisotropy
Authors: Kosmachev O. A.  , Yarygina E .A.  , Matyunina Ya. Yu.  , Friedman Yu. A.
Published: September 2022

We have investigated the effect of single-ion anisotropy of the "easy plane" type on the phase states of a ferrimagnet with S=1 and sigma=1/2 sublattices and non-Heisenberg (bilinear and biquadratic in spins) exchange interaction for the sublattice with S=1. It is shown that taking into account both the non-Heisenberg exchange interaction and the single-ion anisotropy of the sublattice with S=1 leads to the realization of a phase with vector order parameters (ferrimagnetic phase) and a phase characterized by both vector and tensor order parameters (quadrupole-ferrimagnetic). It is shown that taking into account single-ion anisotropy changes the type of phase transition in comparison with an isotropic non-Heisenberg ferrimagnet. A phase diagram is constructed, and the condition for the compensation of the sublattice spins is determined. Keywords: ferrimagnet, biquadratic exchange interaction, single-ion anisotropy "easy plane", quadrupole-ferrimagnetic phase, phase transition.
On the possibility of incorporation of the iron impurity into A sites in SrTiO-=SUB=-3-=/SUB=-
Authors: Sluchinskaya I. A.  , Lebedev A. I.
Published: September 2022

The local environment and oxidation state of the Fe impurity in strontium titanate are studied using XAFS spectroscopy. The influence of annealing temperature and deviation from stoichiometry on the possibility of incorporation of the impurity into the A and B sites of the perovskite structure is studied. The results obtained from the X-ray diffraction, XANES spectra, and EXAFS spectra suggest that at high annealing temperature the iron atoms, at least partially (up to 30%), enter the A sites in SrTiO3. The obtained results agree with results of first-principles calculations, according to which the iron at the A site exhibits strong off-centering (the displacement of ~1 Angstrem), similar to that previously established in SrTiO3 samples doped with Mn and Co. Keywords: strontium titanate, iron, doping, XAFS, off-center atoms.
Dependence of the energy of emission molecular orbitals in short open carbon nanotubes on the electric field
Authors: Tomilin O. B.  , Rodionova E. V.  , Rodin E.A.  , Poklonski N. A.  , Anikeyev I. I.  , Ratkevich S. V.
Published: September 2022

On the examples of short open carbon nanotubes of armchair type (n,n), for n=3, 4, and zigzag (n,0), for n=5, 6, 7, the influence of the magnitude and direction of the external constant electric field vector on their field emission properties was studied. It is shown that the deviation of the field vector from the nanotube axis leads to an increase in the field strength to generate electron field emission. Emission orbitals in carbon nanotubes (n,n) found as a result of a new type of conjugation of p-electrons in cylindrical conjugated systems are more sensitive to a change in the direction of the electric field vector compared to emission orbitals in nanotubes (n,0). When the electric field vector deviates from the nanotube axis, the emission orbitals of carbon nanotubes change the less, the larger the nanotube diameter. Keywords: short open carbon nanotubes, field emission, conjugation of p-electrons, emission molecular orbital.
Effect of deuteration on phase transitions in (NH-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=-VOF-=SUB=-5-=/SUB=-
Authors: Bogdanov E.V.  , Bondarev V.S.  , Gorev M.V.  , Molokeev M.S.  , Flerov I.N.
Published: September 2022

The (ND4)3VOF5 crystal was grown with a high degree of deuteration (D~92%). Structural and thermophysical studies have been carried out, the parameters of phase transitions have been determined. It was found that the deuteration of the ammonium cation in (NH4)3VOF5 led to a change in the chemical pressure, which was accompanied by an increase in the unit cell volume and an increase in the phase transition temperatures. The baric coefficients dTi/dp were determined and the phase T-p diagram (ND4)3VOF5 was constructed. A decrease in the temperature stability of the initial cubic phase Fm3m in (ND4)3VOF5, as well as a wedging out of the intermediate monoclinic phase at a lower pressure as compared to (NH4)3VOF5, was found. Keywords: oxyfluorides, phase transitions, heat capacity, thermal expansion, pressure.
Electronic states structure of Gd-=SUB=-5-=/SUB=-Sb-=SUB=-3-=/SUB=- and Gd-=SUB=-5-=/SUB=-Ge-=SUB=-2-=/SUB=-Sb compounds according to band calculations and optical spectroscopy
Authors: Knyazev Yu. V.  , Lukoyanov A. V.  , Kuz'min Yu. I.  , Samatham S. S.  , Patel A. K.  , Suresh K. G.
Published: September 2022

Results of investigations of the electronic structure and optical properties of Gd5Sb3 and Gd5Ge2Sb compounds are presented. Calculations of band spectra were carried out in frame of local density approximation with a correction for strong correlation effects in 4f shell of rare-earth ion (DFT + U + SO method). Optical constants of these materials were measured by ellipsometric technique in wide wavelength interval. Energy dependencies of a number of spectral parameters were determined. The nature of quantum light absorption is discussed on the base of comparative analysis of the experimental and calculated spectra of optical conductivity. Keywords: Gd5Sb3, Gd5Ge2Sb compounds, optical properties, electronic structure.
Scanning tunneling microscopy in chalcogenide thermoelectrics (Bi, Sb)-=SUB=-2-=/SUB=-(Te, Se, S)-=SUB=-3-=/SUB=-
Authors: Lukyanova L. N.  , Makarenko I. V.  , Usov O. A.
Published: September 2022

The morphology studies of the interlayer surface (0001) were carried out by the method of scanning tunneling microscopy in the n-Bi1.6Sb0.4Te2.94Se0.06, n-Bi1.8Sb0.2Te2.82Se0.09S0.09, p-Bi0.8Sb1.2Te2.91Se0.09 and p-Bi0.7Sb1.3Te2.91Se0.09 solid solutions. On the surface (0001), impurity and native defects were found (vacancies of tellurium, antisite defects, adatoms), formed in the compositions due to substitutions of atoms in the Bi2Te3 sublattices. The average values of Hm and the standard deviations of HS in height in the distribution of atoms on the surface are determined depending on the composition of the solid solution. The effect of detected defects on the thermoelectric properties of solid solutions has been established. Keywords: bismuth telluride, solid solutions, scanning tunneling microscopy, imputity and native defects, Seebeck coefficient.
Application of radio spectroscopy methods for the study of thermoelectrics with a chalcopyrite structure
Authors: Matukhin V. L.  , Gavrilenko A. N.  , Schmidt E. V.  , Orlinskii S. B.  , Sevastianov I. G.  , Garkavyi S. O.  , Navratil J.  , Novak P.
Published: September 2022

Doped chalcopyrite compounds are considered. The results of studying the spectral parameters by the 63,65Cu NMR method in a local field, as well as by the EPR method in the temperature range 15-300 K are presented. The observed broadening of the resonance lines of the NMR spectra and the detection of a paramagnetic signal in the sample at a temperature of 15 K indicate the appearance of anti-structural defects. The rapid change in the shape of the EPR spectrum line, in the temperature range 100-130 K, is associated with the structural-phase transition. Keywords: thermoelectrics, chalcopyrite compounds, antisite defects.
Galvanomagnetic properties and thermoelectric power of ultrathin films of the bismuth-antimony system on a mica substrate
Authors: Gerega V. A.  , Suslov A. V.  , Komarov V. A.  , Grabov V. M.  , Demidov E. V.  , Kolobov A. V.
Published: September 2022

The study of the electronic properties of ultrathin films of pure bismuth and bismuth-antimony alloys is of interest, since an increase in conductivity with decreasing sample thickness was found. This paper presents the results of an experimental study of the structure, electrical, galvanomagnetic and thermoelectric properties of pure bismuth and Bi1-xSbx thin films (x=0.05 and 0.12) on a mica substrate in the thickness range of 10-30 nm. An increase in the conductivity with a decrease in the thickness of the samples was found. It may be due to the presence of topologically protected surface states. It is shown that the features of the manifestation of this effect are significantly influenced by the alloys band structure. The form of the temperature dependences of the Seebeck coefficient casts doubt on the fact that surface states have a positive effect on the thermoelectric efficiency of thin bismuth-antimony films. However, the detection of a positive thermoelectric power in Bi0.88Sb0.12 samples can become an important factor for searching for the possibility of creating a p-branch of thermoelectric converters. Keywords: bismuth, antimony, thin films, surface states, thermoelectric power.
Interband two-photon linear-circular dichroism in semiconductors in the Kane approximation
Authors: Rasulov V.R.  , Rasulov R. Ya.  , Akhmedov B.B.  , Muminov I.A.
Published: September 2022

The dependences of the partial coefficients of interband two-photon absorption of light, which differ from each other by the types of optical transitions, are analyzed depending on the degree of polarization of the light, and a quantitative analysis of the coefficient of linear-circular dichroism of two-photon absorption of light is carried out. Expressions are obtained for the spectral dependence of the coefficient of interband two-photon absorption of light in narrow-gap semiconductors in the Kane model. Keywords: initial, virtual and final states, interband two-photon absorption of light, Kane's approximation.
Study of the multiband exciton spectrum of ZnSe in the range of 477-490 nm
Authors: Morozova N. K.  , Abbasov I. I.  , Gavrishuk E. M.  , Musayev M. A.  , Huseynov J. I.  , Mammadova A. J.
Published: September 2022

The photoluminescence spectra of CVD (chemical vapour deposition) ZnSe polycrystalline grown with a large excess of selenium and containing \O*Se-Cu+i\ complexes at stacking faults are studied. Absorbance was measured to complement these data. The features of the PL spectra in comparison with cathodoluminescence are considered. It is shown that PL bands identical to CL are observed as somewhat shorter wavelengths. For the studied crystals, a band model is presented according to the data obtained in this work. The low-energy shift of the PL spectra with decreasing excitation energy corresponds to a shift on the energy scale of the band model with a corresponding change in the type of radiative transitions. It is shown that identical photoluminescence bands are observed as somewhat shorter wavelengths than cathodoluminescence bands. For the crystals under study, a band model is presented according to the data obtained in the given decreasing work. The low-energy shift of the photoluminescence spectra upon the excitation energy corresponds to a shift along the energy scale of the band model with a corresponding change in the type of radiative transitions. Changes have been introduced that characterize the nature of the group of equidistant bands 477-490 nm, which are characteristic of ZnSe samples with an excess of oxygen and Se. The results can be useful for a more complete study of the structure of multiphonon exciton spectra of photo and cathodoluminescence of AIIBVI crystals. Keywords: band model, narrow-line multi-photon spectra, exciton radiation, stacking faults, isoelectronic oxygen impurity, carrying effective negative charge.
Multiple changes in the electron-phonon interaction in quantum wells with dielectrically different barriers
Authors: Maslov A.Yu.  , Proshina O.V.
Published: September 2022

The specific features of the interaction of charged particles with polar optical phonons have been studied theoretically for quantum wells with the barriers that are asymmetric in their dielectric properties. It is shown that the interaction with interface phonon modes makes the greatest contribution in narrow quantum wells. The parameters of the electron-phonon interaction were found for the cases of different values of the phonon frequencies in the barrier materials. It turned out that a significant (by almost an order of magnitude) change in the parameters of the electron-phonon interaction can occur in such structures. This makes it possible, in principle, to trace the transition from weak to strong interactions in quantum wells of the same type but with different compositions of barrier materials. The conditions are found under which an enhancement of the electron-phonon interaction is possible in an asymmetric structure in comparison with a symmetric one with the barriers of the same composition. Keywords: quantum well, electron-phonon interaction, polaron, asymmetric barriers.
Effect of a parallel magnetic field on the photocurrent in GaAs/AlAs p-i-n-structures
Authors: Larkin I.A.  , Khanin Yu.N.  , Vdovin E.E.
Published: September 2022

The behavior of the photocurrent in GaAs/AlAs p-i-n-heterostructures is studied in a magnetic field parallel to the heterolayers in the wavelength range from 395 to 650 nm. A strong dependence of the non-oscillating component of the photocurrent on the radiation wavelength associated with the suppression of the diffusion current by the magnetic field was found. It is shown that the behavior of the oscillating component of the photocurrent in a magnetic field does not depend on the wavelength of light and is determined by the transfer of electrons through the dimensional quantization level in a triangular near-barrier well. It is shown that the suppression of the oscillating component by the magnetic field is due to the smearing of the level in the triangular well due to the motion of electrons parallel to the walls of the well and perpendicular to the magnetic field. Keywords: heterostructures, photoconductivity, magnetotunneling.
Electromagnetic properties of polymer composites Li-=SUB=-0.33-=/SUB=-Fe-=SUB=-2.29-=/SUB=-Zn-=SUB=-0.21-=/SUB=-Mn-=SUB=-0.17-=/SUB=-O-=SUB=-4-=/SUB=-/P(VDF-TFE) in the frequency range 100-7000 MHz
Authors: Isaev I.M.  , Kostishin V.G.  , Shakirzyanov R.I.  , Kayumova A.R.  , Salogub D.V.
Published: September 2022

The article describes electromagnetic and microwave properties of the polymer composite with the lithium spinel ferrite inclusion of composition Li0.33Fe2.29Zn0.21Mn0.17O4 in the frequency range 100-7000 MHz. It is shown that samples with a mass fraction of ferrite 60, 80% have pronounced radio-absorbing properties, measured using the reflection coefficient on a metal plate (return losses). For a composite with 80% ferrite, the minimum return loss was -37.5 dB at 2.71 GHz with an absorption width at -10 dB of 3 GHz. High absorption characteristics are directly related to the use of ferroelectric polymer P(VDF-TFE) as a binder, which is expressed in the combined action of the absorption mechanisms of the magnetic and ferroelectric phases. Keywords: lithium ferrite, polymer composite, polyvinylidene fluoride, radio-absorbing material.
Low Temperature Electrical Properties of CVD Graphene on LiNbO-=SUB=-3-=/SUB=-: Acoustic Studies
Authors: Drichko I. L.  , Smirnov I. Yu.  , Galperin Yu. M.  , Dementev P. A.  , Rybin M. G.
Published: September 2022

Contactless acoustic methods were used to determine electrical parameters --- electrical conductivity, carrier mobility and their concentration --- in single-layer graphene deposited on the surface of lithium niobate. Keywords: graphene, acousto-electronic effects, low temperatures, high-frequency magnetotransport.
Effect of nickel on the lifetime of charge carriers in silicon solar cells
Authors: Bakhadyrkhanov M.K.  , Kenzhaev Z.T.  , Koveshnikov S. V.  , Ayupov K. S.  , Kosbergenov E. Zh.
Published: September 2022

It has been shown experimentally that nickel clusters on the surface of a silicon sample contain a large amount of oxygen and recombination impurities --- Cu, Fe, Cr, and so shows good gettering properties of clusters. The optimum temperature of nickel diffusion into silicon is determined as 800-850oC. Doping with impurity nickel atoms with the formation of clusters makes it possible to increase the lifetime of nonequilibrium charge carriers in the base of a solar cell by up to 2 times, while the formation of a nickel-enriched region in the face layer is more efficient. It is shown that the effect of additional doping with nickel weakly depends on the sequence of the processes of nickel diffusion and the creation of a working p-n-junction. Keywords: silicon solar cells, nickel diffusion, nonequilibrium charge carriers, gettering, p-n junction.
Influence of chemical treatment and surface topology on the blocking voltage of GaAs thyristor mesastructures, grown by MOCVD
Authors: Chigineva A. B.  , Baidus N. V.  , Nekorkin S. M.  , Zhidyaev K. S.  , Kotomina V. E.  , Samartsev I. V.
Published: September 2022

The effect of sulfide passivation (chemical treatment in a peroxide-sulfur etchant and in a solution of Na2S in isopropanol) and complication of the profile of the lateral surface of thyristor mesastructures on the blocking ability of GaAs thyristor mesastructures is investigated. It is shown that the blocking voltage of the chips increases several times both after chemical treatment of the surface and with the complication of the surface topology. Keywords: thyristors, blocking voltage, sulfide passivation, gallium arsenide, mesastructure.
Thermoelectric heat transfer intensifiers
Authors: Drabkin I. A.  , Ershova  L. B.
Published: September 2022

The work of thermoelectric heat transfer intensifier is analyzed in the paper. Criteria for the efficiency of such intensifiers are given. The advantage of using a thermoelectric cooler is evaluated depending on the temperature difference on the heat sink when applied without a thermoelectric module. It is shown that in many cases a thermoelectric cooler cannot intensify heat transfer. In case a thermoelectric cooler is used to reduce the object temperature, it is also necessary to reduce the heat sink thermal resistance. Keywords: thermoelectric cooler, heat exchange, intensifier, efficiency.
Methods for investigation of electrical contact resistance in a metal film--semiconductor structure
Authors: Shtern M. Yu.  , Karavaev I. S.  , Rogachev M. S.  , Shtern Yu. I.  , Mustafoev B. R.  , Korchagin E. P.  , Kozlov A. O.
Published: September 2022

The electrical contact resistance significantly affects the efficiency of thermoelements. In the case of high doped thermoelectric materials, the tunneling mechanism of conductivity prevails at metal-semiconductor interface, which makes it possible to obtain a contact resistance of less than 10-8 Ohm·m2. Low resistance values significantly complicate its experimental determination. Work present three techniques and a measuring stand for the investigation of contact resistance. The techniques are based on the measurement of the total electrical resistance, which consists of transient contact resistance and the resistance of the thermoelectric material with its subsequent exclusion. The developed techniques differ in the arrangement of the investigated contacts on the samples, in the methods of measurement and processing of the obtained results, and make it possible to determine the specific contact resistance of the order of 10-10 Ohm·m2. Keywords: thermoelements, film contacts, contact resistance, measurement techniques.
Thermal Activation of Valley-Orbit States of Neutral Magnesium in Silicon
Authors: Abraham R.J.S.  , Shuman V.B.  , Portsel L.M.  , Lodygin A.N.  , Astrov Yu.A.  , Abrosimov N.V.  , Pavlov S. G.  , Hübers H.-W.  , Simmons S.  , Thewalt M.L.W.
Published: September 2022

Interstitial magnesium acts as a moderately deep double donor in silicon, and is relatively easily introduced by diffusion. Unlike the case of the chalcogen double donors, parameters of the even-parity valley-orbit excited states 1s(T2) and 1s(E) have remained elusive. Here we report on further study of these states in neutral magnesium through temperature dependence absorption measurements. The results demonstrate thermal activation from the ground state 1s(A1) to the valley-orbit states, as observed by transitions from the thermally populated levels to the odd-parity states 2p0 and 2p±. Analysis of the data makes it possible to determine the thermal activation energies of transitions from the donor ground state to 1s(T2) and 1s(E) levels, as well as the binding energies of an electron with the valley-orbit excited states. Keywords: magnesium impurity in silicon, deep center, optical spectroscopy.