Electrophysical Characteristics Research Articles

Электрофизические и температурные характеристики тонких слоёв квантовых точек Ag2S

В работе представлено исследование электрофизических свойств тонких плёнок коллоидных квантовых точек сульфида серебра (КТ Ag2S/SiO2) и квантовых точек сульфида серебра, декорированных плазмонными наночастицами золота (КТ Ag2S/SiO2/Au). Проведено исследование температурных зависимостей проводимости в диапазоне температур от 300 до 360 К. Были получены значения энергии активации из линейных аппроксимаций вольт-амперных характеристик в координатах Аррениуса. Показано, что декорирование КТ Ag2S/SiO2 плазмонными наночастицами золота приводит к увеличению ширины запрещенной зоны с 0.29 до 0.89 эВ. В работе рассчитан фактор идеальности и определены основные механизмы проводимости представленных тонкоплёночных структур. Показано, что декорирование КТ Ag2S/SiO2 наночастицами Au приводит к изменению типа проводимости. Согласно модели Мотта-Герни рассчитана подвижности носителей заряда.

Comparative studies of GaN, n-GaN and n+-GaN contact layers on GaN/c-Al2O3 virtual substrates synthesized by PA MBE

An approach to create ohmic contacts to GaN layers without using the high-temperature annealing procedure is described in the paper. The results of comparative studies of structural, morphological, optical, and electrical properties of undoped GaN and silicon-doped n-GaN and n+-GaN doped contact layers are presented.The contact layer technology can be successfully realized using a plasma-assisted molecular beam epitaxy (PA MBE) setup of industrial type, where due to characteristic design features, the growth of nitride AIIIN compounds occurs using small streams of activated nitrogen, which significantly limits the possibility of varying the technological parameters.For the first time it is demonstrated that using the proposed technology for the creation of post-grown GaN, n-GaN and n+-GaN contact layers to GaN/c-Al2O3 virtual substrates in Ga-enriched conditions of epitaxial PA MBE growth at relatively low temperatures Ts = 700oC an effective filtration of dislocations threading from the buffer GaN layer of the virtual substrate formed by MOCVD can be realized.Calculations of in-plane εxx and out-of-plane εzz deformations, as well as residual biaxial stresses based on X-ray diffraction and Raman microspectroscopy data indicate at high structural quality of the formed contact layer regardless of the silicon doping level. At the same time PA MBE contact layers GaN, n-GaN and n+-GaN demonstrate close optical properties (refractive index and photoluminescence) in a wide range (400–850 nm), as well as minimal influence of defects associated with the formation of silicon clusters at high doping levels.The contact resistance reduced to the pad width determined using the transmission line method for the structure with n+-GaN contact layer was of ∼0.11 Ohm*mm and ∼0.5 Ohm*mm for n-GaN. Note that electrophysical characteristics of n-GaN and n+-GaN contact layers do not degrade under high-dose exposure of high-energy X-ray irradiation.The technique developed in our work to create ohmic contacts to GaN layers, as well as the obtained experimental results, have important implications for understanding the physics of AIIIN nanoheterostructures and will contribute to their potential applications in their fabrication.

Analysis of the State of Moisture Control to Ensure and Regulate the Quality of Grain and Grain Products

The article discusses the methods for determining the maturity of grain and describes its behavior during harvesting, to optimize the selection of the grain moisture state, discusses the requirements for the choice of measurement method and the design of moisture control measuring devices, as well as its high accuracy and the possibility of measuring from field conditions, collection, storage, transportation, and industrial processing and release of finished products of granular materials. The purpose of the study is to improve the efficiency of control and management of complex technological processes and moisture control devices for granular bulk materials of plant origin through the development of systems for automatic and automated control of the electrophysical characteristics of grain products and to increase the reliability of quantitative and qualitative assessments of production and technological measurement information. To achieve this goal, it is necessary to conduct analytical and experimental studies of the possibility of creating an express method for controlling the moisture content of grain and products of their industrial processing and the development of a moisture meter for automated control of raw material parameters during acceptance and storage at grain processing enterprises. The article discusses the scientific and methodological foundations for measuring the electrophysical characteristics of grain products of agricultural production and the implementation on this basis of the functional subsystem of information support by the Automated Process Control System for Controlling the Mass Ratio of Moisture of Plant Origin Materials. A critical analysis of the current state of the theory and practice of automatic control of electrophysical characteristics of grain products and the identification of the trend of their further development and improvement are carried out. A mathematical model of the interaction of a high-frequency field with a granular material has been constructed, where the influence of the elastic properties of the grain on the electrical characteristics of the electromagnetic wave, which distinguishes its behavior in the field of a high-frequency wave from many other dielectrics, has been substantiated, and the influence of a large number of various disturbing factors has been studied, often the measurement results cannot be applied in the control of the technological process due to the uneliminated error, which is the cause of inaccurate information. Primary measuring transducers of electrophysical parameters of grain products are proposed, and their mathematical models are considered. A functional scheme of the measuring device based on the dielcometric method of moisture control of grain and granular materials has been developed, and metrological characteristics have been given.

ИМПЕДАНСНЫЙ АНАЛИЗ ПРОЦЕССОВ ПЕРЕНОСА ЗАРЯДА В СТРУКТУРЕ МЕТАЛЛ/ПОЛИМЕР/МЕТАЛЛ

The reaserch is devoted to the experimental study of charge transfer processes in thin films of an electroactive polymer from the class of polyarylene phthalides – poly (diphenylene phthalide). The method of impedance analysis of thin polymer films was used in this work. The material is quite well studied using other methods, such as thermally stimulated methods, optical spectroscopy, etc. However, frequency measurements were carried out mainly only in the field of determining capacitance-voltage characteristics. And since the polymer is electroactive, we should expect to identify features associated with charge transfer in the alternating field mode. In this regard, the work carried out an impedance analysis of thin films of poly (diphenylene phthalide) in the frequency range from 0.1 to 106 Hz. Typically, in impedance analysis, in addition to an ac field, a small DC bias voltage is applied to the metal/polymer/metal structure. This makes it possible to obtain data on surface polarization, charge carrier mobility, and the Maxwell-Wagner effect in the case of studying multilayer films. However, taking into account the electrical activity of the studied material, even impedance analysis in an alternating field, but with an effective voltage range from 0.1 to 10 V, made it possible to evaluate some of the electrophysical characteristics of the behavior of thin films. It was found that the slope of the impedance curve depends on the mechanism of transport of charge carriers in the polymer film. As the voltage increases from 0.1 to 10 V, an increase in the slope of the graph is observed. With an increase in the magnitude of the effective voltage, a transition occurs from the ohmic to the injection mechanism of transport of charge carriers limited by traps. When reaching 2 V, a mode of complete filling of the traps is observed, as a result of which an increase in voltage ceases to affect the slope of the frequency response. The dependence of the transition frequency fc on voltage has been plotted. This frequency corresponds to the transition from the predominance of the active to the reactive component of the impedance. Here, an exponential dependence on the magnitude of the applied voltage is observed, which also indicates the dependence of the mechanisms of transport of charge carriers in the polymer film on voltage (electric field).

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.

Electrophysical Characteristics of $c$BN–NbN Composite Ceramics Doped with Al$_{2}$O$_{3}$, Si$_{3}$N$_{4}$, and SiC

Electrophysical Characteristics of $c$BN–NbN Composite Ceramics Doped with Al$_{2}$O$_{3}$, Si$_{3}$N$_{4}$, and SiC

Characterization of a Heterojunction Silicon Solar Cell by Means of Impedance Spectroscopy.

Impedance spectroscopy provides relevant knowledge on the recombination and extraction of photogenerated charge carriers in various types of photovoltaic devices. In particular, this method is of great benefit to the study of crystalline silicon (c-Si)-based solar cells, a market-dominating commercial technology, for example, in terms of the comparison of various types of c-Si devices. This study investigates the dark and light electrophysical characteristics of a heterojunction silicon solar cell fabricated using plasma-enhanced chemical vapor deposition. The measurements are performed at various applied biases, enabling the determination of complex resistance, characteristic time, capacitive response and impurity concentration within the semiconductor junction and to correlate them with the device performance. In addition, the impedance spectra of the studied cell were investigated as a function of temperature. Studies of the frequency and temperature dependences of capacitance do not reveal a significant presence of thermally activated centers of free carrier capture, concomitant with a very small value of the activation energy extracted from an Arrhenius-type analysis. This leads to a conclusion that these centers are likely not impactful on the device operation and efficiency.

Numerical and analytical solution of temperature distribution in foamed soy suspension during vacuum microwave drying

Objective. Technologies of vacuum dehydration of solutions in the microwave field are constantly developing in the direction of increasing the energy efficiency of the drying process and reducing the cost of target products. This scientific direction fully applies to vacuum microwave drying of soy suspension in a foamed state. In this regard, the most important task is to improve mathematical modeling, which provides significant assistance in the study of heat and mass transfer processes occurring in vacuum dryers with microwave power supply; in the design of new installations and the development of effective modes of their operation; the development of optimal modes of vacuum drying foamed soy suspension, taking into account thermophysical and electrophysical characteristics. Method. The research is based on computer simulation methods. Result. Using the results of previous studies, a mathematical apparatus was obtained for finding the temperature in a foamy product during vacuum microwave drying. Its difference from existing mathematical models lies in the possibility of using simple methods for analyzing differential equations with fewer unknown variables. A method of numerical and analytical solution of a mathematical model of the process of vacuum microwave drying of foamed suspension is proposed. Experimental verification showed quite satisfactory convergence of the simulation results with an error of 10-12%. Conclusion. The study of numerical methods for solving the formulated problem makes it possible to determine the temperature at any point of the soybean suspension, taking into account the thermophysical and electrical characteristics of the suspension in a wide range of operating parameters.

Facile Synthesis of Stable Nanosized Silver Clusters in Plasma Discharge Under Ultrasonic Cavitation

This work is devoted to the study of plasma-chemical processes determined by the combination of the effect of thermally nonequilibrium, low-temperature plasma and intensive ultrasonic vibrations in the regime of intensive cavitation on liquid-phase media. This method for the realization of plasma-chemical transformations has been proven to be of significant interest and to have advantages for the creation of new nano-sized materials with special properties because it allows for varying the electrophysical and acoustic characteristics of the process when carrying out plasma-chemical reactions and fusion reactions. In this work, a novel facile technique for the synthesis of nanosized silver clusters in plasma discharge under ultrasonic cavitation is reported. Such a type of plasma involves the simultaneous effect of high-intensity cavitation and steady electric discharge in a liquid phase between electrodes of desired material. As a result, stable tiny silver nanoclusters with around a 1-nm size and a relatively narrow particle size distribution were obtained using toluene as a liquid medium. The nanoclusters were characterized with dynamic light scattering, transmission electron microscopy, electron diffraction, and optical methods. The results confirmed the formation of nanoclusters with an absorbance peak around 300 nm and the absence of 400-nm peaks typical for silver nanoparticles. Fluorescence tests allowed for establishing the amorphous structure of the synthesized nanoclusters occupying the intermediate position between few-atom nanoclusters and nanoparticles. The nanoclusters obtained were proven to be stable for more than 3 months. The experiments also revealed the possibility of performing high-temperature plasma-chemical reactions that can be applied in fusion technology.

Effect of Ultrasonic Dispersion on Electrophysical Characteristics of Composites Based on Carbon Nanotubes

Effect of Ultrasonic Dispersion on Electrophysical Characteristics of Composites Based on Carbon Nanotubes

Temperature−Frequency Dependences of the Electrophysical Characteristics of Polyfunctional Compounds Using Guaiacol as an Example

Temperature−Frequency Dependences of the Electrophysical Characteristics of Polyfunctional Compounds Using Guaiacol as an Example

Macroscopic and Mesoscopic Inhomogeneities of Electrophysical, Optical, and Photoelectric Characteristics in Chromium Compensated Gallium Arsenide Wafers

Macroscopic and Mesoscopic Inhomogeneities of Electrophysical, Optical, and Photoelectric Characteristics in Chromium Compensated Gallium Arsenide Wafers

Technology for studying the electrophysical characteristics of sedimentary rocks of South Yakutia at the railway station Kyurgellyakh using the method of remote inductive probing

The possibilities of a new technology for applying the method of remote inductive sensing at a frequency of 1,125 and 0,281 MHz in the separation interval of the emitting and receiving antennas in terms of quantitative assessment of electrophysical characteristics in the rock foundation of engineering structures at the railway station Kyurgellyakh in South Yakutia are studied. In the strata of icy and clay deluvial-eluvial formations and sedimentary rocks (dolomites, limestones), a general increase in depth of the effective values of the electrical resistance and the real part of the complex relative permittivity, which is atypical in AC geoelectrics, has been established. The range of variability of resistivity and permeability is 600–1600 Ohm·m and 3–7 arb. units. According to a sharp change (from a smaller to a larger one) in the growth rate of resistance and permeability, two boundaries were found. The first structural boundary lies at a depth of about 10 m and corresponds to the lower boundary of the area of intense weathering. The second petrophysical boundary lies at a depth of about 20 m and characterizes the transition of the highly weathered and highly fractured upper part of the sedimentary rock mass into the lower consolidated solid part located in the area of thermal rest. The obtained results give grounds to recommend a proven technology for solving the problems of geomechanics and thermophysics of frozen soils in terms of determining their strength and depth of the lower boundary of the layer of annual heat exchanges.

Characterization of the electrical properties of MPS schottky structures incorporating Fe doped polyvinyl chloride (PVC)

This paper explores the effects of the organic interfacial layer on the electrophysical characteristics of Schottky barrier diodes (SBDs). Three types of SBDs were fabricated: Au-Si (referred to as MS), Au/PVC/Si (referred to as MPS1), and Au-/PVC:Fe/Si (referred to as MPS2). Fe nanopowders were subjected to analysis using XRD, SEM, and EDX techniques to investigate their structural and optical characteristics. To investigate the conduction mechanisms of these diodes, I-V characteristics were examined using thermionic-emission (TE), Cheung, and Norde functions. The surface-state density (N ss ) distribution of energy was determined by analyzing the current–voltage (IF-VF) curve under forward bias conditions. This analysis considered the voltage-dependent barrier height (BH) and ideality factor (n(V)). The results demonstrated that the polymeric interlayer without Fe nanoparticles reduced N ss by a factor of 7, while the presence of Fe nanoparticles led to a two-order magnitude decrease, resulting in improved efficiency in comparison with MS structures. The obtained results indicated that including a polymeric layer in MPS structure enhanced their electrophysical features compared to MS diodes, and significantly increased rectification by 15–45 times. In summary, the existence of an organic interfacial layer significantly altered the conduction mechanisms and electrophysical characteristics of MPS diodes. It was found that the addition of Fe nanoparticles in the interlayer resulted in substantial improvements in N ss , efficiency, rectification, and conduction characteristics compared to MS diodes.

Impact of the thickness of phthalocyanine films and its metal complexes on optical and electrical properties

The paper presents the results of a study of the structural, optical and electrophysical characteristics of phthalocyanine films and its metal complexes with different thicknesses. Films of phthalocyanine and its metal complexes were obtained on the conductive surface of the FTO by thermal evaporation in vacuum. It is shown that the observed broadening of the B and Q bands and the hypsochromic shift of the maxima in the absorption spectra are associated with the central atom. With a decrease in the thickness of MPc films, there is a decrease in the value of the half-width of the absorption spectra. The effect of the thickness of phthalocyanine films on the efficiency of generation and transport of charge carriers in the FTO/MPc/Al cell was studied. It is shown that the VAC increases almost 2.5 times compared to a photocell based on a metal-free phthalocyanine. From the obtained impedance measurement data, it was found that the electrophysical parameters of phthalocyanines depend on the values of optical density, broadening of absorption bands in the short-wave and visible spectral regions, which is consistent with the data of the volt-ampere characteristic.

Influence of silicon characteristics on the parameters of manufactured photonics cells

The paper investigates the influence of the electrophysical characteristics of silicon on the final parameters of photoelectronic elements using p-i-n photodiodes as an example. It has been found that photodiode samples made on the basis of silicon with a higher resistivity are more prone to the formation of inversion channels at the oxide-semiconductor interface. Also, the dark current and responsivity of such photodiodes reach saturation at a lower voltage. It has also been shown that silicon-based photodiodes with a longer lifetime of non-basic charge carriers have lower dark current values. It has been shown that products with crystallographic orientation [111] have a much lower density of surface dislocations after technological operations than in the case of silicon with orientation [100]. It was also found that materials with different crystallographic orientations have different phosphorus diffusion coefficients. It has been experimentally established that a silicon oxide film grows faster on the surface of crystallographic orientation silicon [111] than on the surface of crystallographic orientation silicon [100]. This is due to the difference in the surface density of silicon atoms inherent in different crystallographic planes.

THE METHOD OF ADJUSTING THE MULTI-FREQUENCY PROBING RADAR SIGNAL PARAMETERS AND THE TROPOSPHERIC RADIO WAVEGUIDE CHARACTERISTICS

Peculiarities of air circulation in the coastal zone of large reservoirs (large lakes or inland seas such as the Black and Azov Seas) can lead to a significant departure from the standard spatial distribution of meteorological and, accordingly, radiophysical characteristics of air.
 As a result, it is possible for regions of space with an abnormally low attenuation level of radio waves of certain frequency ranges to appear – tropospheric radio waveguides (TWG). The appearance of TWG leads to multi-beam propagation of radio waves and fluctuations of radar signals. Fluctuations of the radar signal lead to a decrease in the range of detection of aerial objects by radars. For single-frequency radar signals, it is only possible to estimate the degree of distortion and the amount of radar detection range loss. A paradoxical situation arises when, due to TWG, it is possible to increase the range of detection of aerial objects, but due to the distortion of the radar signal in TWG, the detection performance decreases. For multi-frequency signals, it is potentially possible to adjust the parameters of the radar signal with the parameters of the radar channel (in this case, the tropospheric radio waveguide).
 The adjustable parameters of a multifrequency signal include: the number of frequency components; bandwidth of the frequency component; average frequency of the frequency component; signal duration; period.
 The characteristics of TWG, on which the parameters of the multifrequency signal depend, include: the lower transmission frequency of TWG; the upper transmission frequency of TWG; the delay time of the rays in the TWG.
 The bandwidth and beam delay values can be obtained directly by emitting and receiving a test multi- frequency pilot signal, but this method requires the presence of a reference reflector in space, which is difficult to implement in practice.
 The electrophysical characteristics of the tropospheric waveguide can be determined from the data of meteorological observations. The method developed in the article allows, based on the known characteristics of the tropospheric waveguide, to determine and adjust the parameters of a multi-frequency signal, which reduces the fluctuations of the sounding signal and increases the aerial objects detection rang.

Calculation of Electrophysical Characteristics of Semiconductor Quantum Wire Device Structures with One-Dimensional Electron Gas

Calculation of Electrophysical Characteristics of Semiconductor Quantum Wire Device Structures with One-Dimensional Electron Gas

The Influence of Temperature on Electrophysical Characteristics of Carbon-Containing Polymer Composites

The Influence of Temperature on Electrophysical Characteristics of Carbon-Containing Polymer Composites

Analysis of the Electrophysical Characteristics of the RF MEMS Switch Taking into Account the Influence of the Substrate Material

Analysis of the Electrophysical Characteristics of the RF MEMS Switch Taking into Account the Influence of the Substrate Material