Electrophysical Properties Research Articles

Enhanced Thermoelectric Performance of Na0.55CoO2 Ceramics Doped by Transition and Heavy Metal Oxides

Using the solid-state reactions method Na0.55(Co,M)O2 (M = Cr, Ni, Zn, W, and Bi) ceramics were prepared and their crystal structure, microstructure, electrophysical, thermophysical, and thermoelectric properties were studied. Doping of Na0.55CoO2 by transition or heavy metal oxides led to the increase in the grain size of ceramics, a decrease in electrical resistivity and thermal diffusivity values, and a sharp increase in the Seebeck coefficient, which resulted in essential enhancement of their thermoelectric properties. The largest power factor (1.04 mW/(m·K2) at 1073 K) and figure of merit (0.702 at 1073 K) among the studied samples possessed the Na0.55Co0.9Bi0.1O2 compound, which also demonstrated the highest values of the Seebeck coefficient (666 μV/K at 1073 K). The obtained results show that the doping of layered sodium cobaltite by different metal oxides allows for improving its stability, microstructure, and functional properties, which proves the effectiveness of the doping strategy for developing new thermoelectric oxides with enhanced thermoelectric performance.

Specificity of electrophysical and gas-sensitive properties of nanocomposite ZnO–TiO2 films formed by solid-phase pyrolysis

ZnO–TiO2 thin films containing 0.5 mol%, 1.0 mol%, and 5.0 mol% ZnO were synthesized by oxidative solid-phase pyrolysis. The materials contained anatase and rutile phases with particle size of 6–13 nm, as confirmed using X-ray phase analysis and scanning electron microscopy. When a certain number of ZnO crystallites appeared in the TiO2 film structure in the temperature range of room temperature to 220 °C, a two-level response of the film resistance was observed, differing by approximately 10%, as obtained by electrophysical measurements. The two-level response correlates with the formation of two donor energy levels of 0.28 and 0.33 eV in the band structure of the ZnO–TiO2 films. The donor level with a higher activation energy corresponded to the Ti vacancy (V−Ti), and that with a lower activation energy corresponded to the Zn vacancy (V−Zn). Two levels of gas-sensitive properties were noted for 0.5ZnO–TiO2, 1ZnO–TiO2, and 5ZnO–TiO2 under the influence of 50 ppm NO2 at 250 °C. Such two-level responses can be ascribed to the pinning of the Fermi level on ZnO and TiO2 nanocrystallites. The mechanism of the beak-shaped and two-level responses of sensors based on composite nanomaterials when exposed to various gases was elucidated.

Silicon with Binary Compounds GexSi1-x

This paper presents the results of studies of the electrophysical, photoelectric, and magnetic properties of silicon samples doped by diffusion of germanium impurity atoms. It has been shown that impurity germanium atoms form in silicon binary compounds of the GexSi1-x type, the concentration of which varies with the depth of the original silicon. The developed diffusion technology of silicon doping with impurity germanium atoms made it possible to obtain a material with different concentrations of impurity germanium atoms, resistivity, and the type of conductivity. The optimal electrophysical parameters of the obtained samples for studying the electrophysical parameters and the magnetic properties were determined, which made it possible to show the possibilities of creating new types of sensors and devices for semiconductor electronics. The presented studies make it possible to develop respective directions in the field of materials science with magnetic properties and the creation of efficient photovoltaic cells for photoenergetics.

Influence of Synthesis Conditions on the Structural, Optical, and Electrophysical Properties of TiO2/CuxO Nanocomposites

Influence of Synthesis Conditions on the Structural, Optical, and Electrophysical Properties of TiO2/CuxO Nanocomposites

A facile approach for design of novel semiconducting thiazolo[5,4-d]thiazole-based conjugated polymers in ambient conditions

The design of conjugated polymers with advanced properties is a significant task for the development of organic electronics. At the same time, it is important to pay attention to the methods of their synthesis, excluding toxic and expensive reagents, following the trends in sustainability. In this study, six thiazolothiazole-based conjugated polymers with thiophene, fluorene, phenylene, and benzodithiophene moieties were synthesized and thoroughly characterized. All materials were obtained through a non-catalyzed condensation reaction of carbonyl derivatives with rubeanic acid under ambient conditions. It is shown that the optoelectronic and electrophysical properties of polymers are suitable for their application in organic or hybrid electronic devices. The certain polymers are found to be promising hole-transport interlayer materials in perovskite solar cells, thus featuring the great potential of proposed methods of development of organic semiconductors.

Development of white organic light emitting diodes based on carbazole-derived compounds

The object of research is the thermal, photophysical, and electrophysical properties of newly synthesized carbazole-derived compounds and organic light-emitting structures based on them. The problem consists in the comprehensive solution of scientific and technical problems of improving the characteristics of white organic light-emitting diodes (OLED), expanding their emission spectrum, improving color and energy characteristics. The results of the thermal, electrophysical and photophysical properties of the investigated carbazole compounds were obtained. They demonstrated good thermal stability. Absorption spectra in solid films were recorded in the range of 300–350 nm. Photoluminescence spectra were observed at a wavelength of 407 nm for the first and second compounds and 430 nm for the third. The quantum yield of photoluminescence in films for compounds 1, 2, and 3 was 16 %, 7 %, and 7 %, respectively. Organic light-emitting structures of white emission color with color coordinates (0.31, 0.35), (0.32, 0.34) and (0.38, 0.34) close to natural white light (0.33, 0.33) were formed using the thermovacuum sputtering method. The turn-on voltage of the white OLED is 6 V, the maximum brightness of the light-emitting structures was 10,000 cd/m2. The devices demonstrated a sufficiently high external quantum efficiency of 5 % to 7 %. The obtained results are explained by the mixing of different types of electroluminescence, namely excitonic and electromeric. Electromeric radiation is obtained due to transport layers. This approach improves such an important parameter of white light as its quality, which includes color coordinates and color rendering index. Due to their color characteristics, white light-emitting diodes based on carbazole-derived compounds are promising candidates for use in modern lighting systems. A separate advantage of these light-emitting structures is the dependence of the color gamut of their radiation on the applied voltage. In addition, organic LEDs based on carbazole-derived compounds have low energy consumption and are environmentally friendly due to the absence of toxic substances in their design, which creates prerequisites for both global energy savings and a reduction of the industrial burden on the environment.

Approaching Technological Limit for Wet‐Pulling Technique

Carbon nanotube fibers (CNTFs) are a promising economical replacement material for contemporary metallic wired conductors due to their lightweight and advanced electromechanical properties. The wet‐pulling technique for CNTF manufacturing is highly versatile, adaptable for both laboratory as well as industrial‐scale production, and can be optimized for the maximum enhancement of electrophysical properties. Herein, a mechanosolvent‐based postfabrication approach for maximizing densification and improving electrical properties of wet‐pulled CNTFs is examined. The experimental process results in fibers achieving 60% of the theoretically maximum density and conductivity of maximally densified metallic single‐walled carbon nanotube bundles. The technique allows a corresponding increase of ≈700% in fiber density (from 100 to 704 kg m−3), a simultaneous ≈530% increase in electrical conductivity (from 748 to 3990 S cm−1), and reduced volume defects from 18% to 2%. The approach was combined with a step‐wise microstructure monitoring using focused ion beam–scanning electron microscopy to determine the mechanisms behind the optimized structures. This work is the first to provide an experimental and theoretical base for the postfabrication optimization of wet‐pulled CNTFs and lays the foundation for further enhancement with techniques such as chemical doping, fiber compounding, and combined infiltration/densification mechanisms.

Study of adsorption of household gas molecules on electrophysical properties of porous silicon

Purpose. This research comprehensively investigates the adsorption of household gas molecules on porous silicon surfaces and its impact on the electrophysical properties of the material. The primary aim is to understand how the adsorption process influences the electrical conductivity and capacitance of porous silicon. Methodology. The study employs various electrophysical analysis methods to measure changes in the material's conductivity and capacitance caused by gas adsorption. Furthermore, the research explores optimal conditions for detecting household gas and establishes the correlation between the degree of adsorption and alterations in electrophysical parameters. Originality. The research contributes novelty by not only revealing increased conductivity due to adsorption but also significant changes in capacitance, providing a foundation for developing efficient gas sensors. Additionally, the article discusses the potential applications of porous silicon in developing novel materials for gas sensors to detect various airborne pollutants. Results. In addition to the previously mentioned findings, the article highlights the results of experiments studying the influence of different concentrations of household gas on the electrophysical characteristics of porous silicon. This insight refines optimal parameters for the effective detection of gas pollutants. The research also discusses the applicability of the results in producing environmentally friendly and highly efficient sensor systems. Practical Value. The obtained conclusions deepen our understanding of the interaction between porous silicon and household gas, crucial for advancing gas sensor technologies. The study opens broad possibilities for applying porous silicon in highly sensitive and reliable gas sensors for diverse practical applications, including safety monitoring and air quality control in industrial and domestic settings. The practical implications extend to the development of real-time, eco-friendly sensor systems.

STUDY OF THE DISTRIBUTION PROFILE OF ION- IMPLANTED IN SILICON AND INFLUENCE THERMAL ANNEALING ON THE STRUCTYRE OF IRON SILICIDES

The paper presents the results of studies of the distribution profiles of implanted iron atoms in silicon depending on the irradiation dose and annealing temperature by the RBS method. The obtained results confirm similar data obtained by SIMS. The influence of thermal annealing on the distribution of iron and other impurities, in particular oxygen, has been studied. The possibility of using the RBS method for the analysis of the concentration distribution and the interaction of impurities with each other is presented. At the same time, the crystal structure of the surface and the electrophysical properties of ion-doped layers were studied.

Study of the copper structure samples externed to extreme influences

This work is devoted to the study of changes in the crystal structure, chemical and phase composition of copper samples subjected to extreme effects of temperature, pressure and electromagnetic fields. With the help of X-ray diffraction, as well as microanalysis, it was revealed that the plastic deformation of copper wires in the car power supply system leads to the formation of a superconducting Cu2O phase. This is the reason for the rapid ignition of the car, as it leads to a sharp increase in the magnitude of the electric current and temperature in the plastic deformation zone of copper wires. During explosion welding of copper samples, the Cu2O phase appears on their surface, which has superconducting properties. This significantly changes the electrophysical properties of copper samples. In metallurgical processes during the smelting of copper products, there is a possibility of the appearance of a superconducting Cu2O phase. When modifying a copper melt with hardening additives, the superconducting Cu2O phase makes it possible to obtain fracture-resistant copper products with high electrical conductivity. Plastic deformation of a copper foil 30 mkm thick by a magnetic field generated by a current of 180 kA leads to the formation of a texture and rupture of the foil. This has been detected using X-ray diffraction, as well as optical and scanning electron microscopy.

Structure, electrophysical and magnetic properties of (1 – x)SmFeO3–xNaNbO3 composites

Structure, electrophysical and magnetic properties of (1 – x)SmFeO3–xNaNbO3 composites

CONDUCTIVITY OF HAFNIUM OXIDE LMS OBTAINED BY ELECTRON BEAM SPUTTERING

Films of hafnium oxide HfOx with a thickness of about 40 nm were obtained by electron beam sputtering at di erent oxygen ow rates in the chamber. The electrophysical properties of lms in air and vacuum were studied. It is shown that the temperature dependences of lm conductivity, measured in vacuum inthe temperature range from 20 to 180 ◦C, have an activation character with an activation energy of 0.82 ±0.02 eV. It has been suggested that charge transfer in the resulting lms is determined by the activation of electrons into the conduction band from the donor level associated with oxygen vacancies. It was found that the conductivity of lms in air changes greatly with varying oxygen ow, while in vacuum the conductivity is practically independent of the oxygen ow. This indicates signi cant di erences in the surface properties of lms obtained at di erent oxygen ows in the chamber during the deposition process.

Технология и результаты изучения взаимодействия поверхности с потоком заряженных частиц низкотемпературной плазмы

An analysis of approaches to studying the interaction of the surface with a stream of charged particles is presented in order to increase the efficiency of the process of low-temperature plasma modification of the surface layer. The results of the analysis showed that it is theoretically difficult to study the interaction, therefore, it is interesting to study it empirically using electrochemistry methods that allow us to investigate the phenomena of mixing and spreading of a liquid placed on the surface caused by molecular interaction processes. An off-the-shelf technology for studying surface interaction for charged particles flow in a low-temperature plasma has been found. The technology is based on the surface interaction for a particle flow simulator, using an aqueous 3,0 % NaCl salt solution. During the course of studying, it was found, firstly, that the results of interaction are actively influenced by chemical processes between the surface and the ions of the solution, depending on the value of the potential of the electric field applied to the surface, as well as due to its microrelief, and secondly, that the main boundary process running under surface interaction and solution is adsorption. The data of the analysis of the effects of exposure to the plasma surface are presented. They proved the reliability of study results, since the course of chemical and adsorption processes also take place. In general, the materials presented in the article allowed making conclusion that the developed technology makes it possible to determine the conditions that ensure an increase in the efficiency of the low-temperature plasma modification process contributing to the improvement of both surface (electrochemical) and volumetric (physical mechanical and electrophysical) properties if it is used either in the initial state or in the state changed by plasma particles.

Structural and electrophysical properties of nanoporous carbon materials obtained from apricot pits

The dependencies of the electrophysical characteristics of nanoporous carbon material (NCM) on the compaction degree of its particles have been investigated in the presented study. It has been found that the maximum value of the electrical conductivity is achieved at a pressure of 2.5 MPa. Furthermore, it has been revealed that the formation of O-compounds on the surface of the studied materials leads to a decrease in electrical conductivity. The correlation between structural-adsorption and electrical-conductive properties of NCMs has been established. Moreover, it has been demonstrated that an increase in the amount of potassium hydroxide results in a decrease in electrical conductivity due to the breakdown of small carbon particles and an increase in contact resistance, while the specific surface area enlarges due to the development of porosity and an increase in the total pore volume.

Effect of eccentricity on electromagnetic logging signals with LWD and VEMKZ instruments (numerical simulation results from some publications)

During drilling, formation fluids are pushed aside by mud filtrate. As a result, the electrophysical properties of rocks near the borehole wall change. Sounding methods are used to determine the resistivity of the part of the reservoir that is remote from the well and unchanged during drilling. Among these methods, electromagnetic logging has the best spatial resolution. However, when analyzing the practical data of electromagnetic sounding, "wrong" ratios of signals from probes of different lengths are often observed, including those showing penetration in impermeable rocks. One of the reasons may be the influence of the shift of the device from the axis of symmetry of the medium. The paper considers the results of numerical simulation of signals from decentralized probes of LWD and VEMKZ instruments in some models.

Electrophysical properties of silicon doped with lutetium

This article discusses the electrical properties of silicon doped with lutetium. The diffusion method is used in the fabrication of silicon structures doped with lutetium. n-Si, p-Si, n-Si<Lu> and p-Si<Lu> were prepared to measure electrophysical parameters. The resistivity of the samples, the mobility of charge carriers, the concentration and the distribution of electrophysical parameters depending on the temperature and thickness of the sample have been studied. These parameters were determined by the four-probe van der Pauw method. Research work was carried out at room temperature and in the range of 77÷300 K. Ohmic contact was obtained through a mixture of 1% Sb + 99% Au for measuring samples on the HMS500 instrument. The resistivity and concentration of charge carriers were also studied, taken from a distance of 2 µm from the surface of the samples. The electrical parameters of the samples were measured using an Ecopia Hall effect measurement system. The electrical parameters of the p-Si and p-Si<Lu> samples did not change significantly. Changes in the surface morphology of these samples were observed in the results obtained in ACM.

Дослідження розподілу кисню по довжині монокристалів кремнію, легованих компонентами з різним типом провідності

The purpose of the article is the study of convective flows and their influence on the growth of single crystals of silicon by the Czochralsky method from a large melt, which contributes to the emergence of non-stationary convection. Therefore, simulation of convection for the growth of silicon single crystals is an important step in the development of conditions for the growth of perfect single crystals. Silicon substrates are used to manufacture more than 90% of semiconductor devices and solar cells. A special role in the development of electronics is played by monocrystalline silicon, which is used for the manufacture of semiconductor devices and integrated microcircuits. The main requirements for the development of technology for the production of silicon substrates is an increase in quality at a decrease in cost. Promising technologies of 10-nm size and 3D-transistor structures significantly increase the requirements for uniformity of distribution of components, including layering in silicon single crystals. For the mathematical modeling of convective flows, melt flows were considered for a cylindrical crucible with a radius of 150 mm at a melt height of up to 40 mm. Such parameters ensure stationary convection in molten silicon. Methods of reducing stratification have been studied and developed for more than 50 years, but have not yet found a definitive solution. This method of single crystal growth is the most controlled and allows to influence the convective flows in the silicon melt below the phase interface with ultrasonic waves in the megahertz range. The effectiveness of using ultrasound in the extraction of semiconductor single crystals depends on the creation of special conditions for introducing them into the melt. 
 Reducing the influence of oxygen on the electrophysical properties of silicon single crystals is an intractable problem of silicon technology. One of the ways to solve this problem is alloying with an isomorphic impurity, for example, tin. The development of a method of doping single crystals of silicon with tin requires determination of its concentration in the liquid and solid phases

Advances in the Application of Black Phosphorus-Based Composite Biomedical Materials in the Field of Tissue Engineering.

Black Phosphorus (BP) is a new semiconductor material with excellent biocompatibility, degradability, and optical and electrophysical properties. A growing number of studies show that BP has high potential applications in the biomedical field. This article aims to systematically review the research progress of BP composite medical materials in the field of tissue engineering, mining BP in bone regeneration, skin repair, nerve repair, inflammation, treatment methods, and the application mechanism. Furthermore, the paper discusses the shortcomings and future recommendations related to the development of BP. These shortcomings include stability, photothermal conversion capacity, preparation process, and other related issues. However, despite these challenges, the utilization of BP-based medical materials holds immense promise in revolutionizing the field of tissue repair.

Properties of ferroelectric composites in the microwave range

Ferroelectric ceramics of barium titanate and its solid solutions have found wide applications in technology, while compositions of a binary system with strontium titanate are most in demand. Electrically controlled components based on the barium titanate – strontium titanate ferroelectric ceramics are widely used in accelerator technology and the use of these materials is relevant at the present time. In the microwave range, composites based on the solid solution system barium titanate – strontium titanate ВаxSr1–xTiO3 (BST). Ferroelectric samples based on ВаxSrx–1TiO3 compound, where x = 0; 0.1; 0.3; 0.5; 0.7 were obtained using a conventional ceramic technology. The temperature dependences of the electrical properties of bulk ceramic samples based on ferroelectric composites were received in the temperature range 100°C to 350°C at a frequency of 1 kHz. It has been established that dielectric parameters significantly depend on the BaTiO3 content in BST compositions. To carry out a research in the frequency range from 0.1 to 8.5 GHz, an experimental setup was manufactured for measuring the electrical properties of ferroelectric materials based on an Agilent E5071C vector analyzer and a microstrip line. To conduct temperature studies, a microstrip line with a controlled sample was placed in a heat, cold and moisture chamber of the Bench-Top SU-261 series, in which it has been heated up to 60°C. The amplitude-frequency characteristics of the transmission coefficient (S21) of samples when heated from 20 °C to 60°C with an interval of 10 degrees were studied. The resonant frequency and quality factor of the resonator have been determined from the amplitude-frequency characteristic. Based on the value of the resonant frequency and the geometric dimensions of the sample, the dielectric constant of the sample material was calculated. It has been shown that with increasing barium titanate content (x = 0.1–0.3), the dielectric constant of the samples under study increases, and the resonant frequency shifts to lower frequencies. For samples with a barium titanate content of 50% and higher (x≥0.5), there are no resonance dependences and strong absorption of electromagnetic waves is observed. It has been established that with increasing temperature, the resonant frequency of composite material samples shifts to higher frequencies. Frequency dispersion of the dielectric constant is observed, which indicates the relaxor properties of the ceramic samples under study. Experimental investigations were carried out using a microwave strip line, a coaxial measuring cell and a capacitive converter; this made it possible to measure the dielectric constant of materials with values of more than several hundred in the microwave range and significantly reduce the control time when conducting thermal studies. It was shown that with a change in temperature, the electrophysical properties of the samples change significantly, which can be used in various systems and devices to change the reflection coefficient and phase of the electromagnetic wave.

Electrophysical properties of composite materials based on graphene oxide and polyaniline

The Hall method was used to study the electrical characteristics of composite materials based on polyaniline (PANI), graphene oxide (GO), and manganese. A comparison of these characteristics of GO-PANI and GO-PANI-Mn composite systems with GO and PANI monomaterials was carried out. It was demonstrated that the electrical conductivity of composites was significantly higher than that of monomaterials and was determined by the charge carrier mobility. Based on UV-visible and IR spectroscopy data, it was shown that the optical band gap (Eg) of the GO-PANI composite increased with the addition of metal, but decreased compared to PANI; the shift of characteristic vibrations to lower frequencies indicated a covalent interaction of the GO-PANI composite with manganese cations