Elemental Semiconductors Research Articles

The effect of the thyristor energy router on harmonics

Energy routers (ER) are the key equipment of the energy internet that provides control over bidirectional power flows and the voltage level of an electric network. The paper presents the thyristor-powered ER (TER) for an Internet-style medium voltage distribution electric network (6, 10, 20 kV). The developed scheme of the device implements longitudinal and transverse voltage regulation at the ER connection point and it allows changing the power flow and the voltage level in the network. The article is devoted to the study of the harmonic components of voltage introduced into the electrical network by the semiconductor elements of the TER. A mathematical and a computer model and a prototype of an electric network section with a TER have been developed. The studies carried out with the help of the developed models have shown that the device does not significantly distort sinusoidally. The harmonic components factor of the output voltage has acceptable values over the entire range of an effective regulation.

Hydrogen-assisted growth of one-dimensional tellurium nanoribbons with unprecedented high mobility

High-mobility van der Waals ambipolar semiconductors are promising in logic and reconfigurable circuits, integrated optoelectronic circuits, due to the excellent gate-controlled capability and effectively tunability of major charge carriers by electrostatic field. Controllable growth of high-quality ambipolar semiconductors with high mobility and stability is highly glamorous and indispensable for further research. Here, we demonstrate a straightforward space-confined chemical vapor deposition (CVD) method to synthesize high-quality quasi-one-dimensional (1D) tellurium (Te) nanoribbons (NRs). By introducing H2 into the gas flow, endothermic compound H2Te was generated from the reaction of liquid Te with H2, and consequently decomposed into elemental Te at low temperature. Further, the Te NRs have been utilized for in-situ fabrication of field-effect transistors (FETs) without transferring process. Ambipolar features are achieved using nickel (Ni) as an ohmic contact. More importantly, the mobilities of the Te NR transistor for hole/electron are as high as 1755/28.6 cm2V−1s−1 and 4024/278 cm2V−1s−1 at room temperature and under a temperature below 20 K, respectively. Our findings confirm the novel strategy for synthesizing 1D elemental semiconductors and their applications with ambipolar behaviors.

Elemental semiconductor red phosphorus/ZnO nanohybrids as high performance photocatalysts

The solar energy conversion through the photocatalyst for the pollutant degradation is important effort for development of the visible light photocatalysts for the practical application in various filed. In this work, elemental semiconductor red phosphorus/ZnO nanohybrid (Z-Rp) through simple, cost-effective, and sustainable ball milling approach and further studied its visible light driven-photocatalytic activity towards the pollutant degradation under visible irradiation. The prepared Z-Rp were characterized by the various stereoscopic and microscopic technique which shows improvement of the structural, optical, and physical properties of the zinc oxide after addition of the elemental red phosphorous. The Diffuse reflectance spectroscopy and valence band spectra shows the shifting of the energy band towards the visible light region after incorporating of the red phosphorus which are father supported by the visible light degradation process. The optimized Z-Rp nanohybrids displayed the excellent visible light driven photocatalytic activity toward the methyl orange dye degradation as compared to the bare materials, which further prove the optimal reaction parameter could effectively enhanced visible light photocatalytic activity. This easy fabrication process and inexpensive earth abundant Rp compared to the silver and gold-based plasmonic metal, which are also used to enhance the photocatalytic performance of the metal oxide nanoparticles, can be a good and sustainable approach for the solar energy conversion for various application.

Tailoring the epitaxial growth of oriented Te nanoribbon arrays

As an elemental semiconductor, tellurium (Te) has been famous for its high hole-mobility, excellent ambient stability and topological states. Here, we realize the controllable synthesis of horizontal Te nanoribbon arrays (TRAs) with an angular interval of 60°on mica substrates by physical vapor deposition strategy. The growth of Te nanoribbons (TRs) is driven by two factors, where the intrinsic quasi-one-dimensional spiral chain structure promotes the elongation of their length; the epitaxy relationship between [110] direction of Te and [110] direction of mica facilitates the oriented growth and the expansion of their width. The bending of TRs which have not been reported is induced by grain boundary. Field-effect transistors based on TRs demonstrate high mobility and on/off ratio corresponding to 397cm2V-1s-1 and 1.5×105, respectively. These phenomena supply an opportunity to deep insight into the vapor-transport synthesis of low-dimensional Te and explore its underlying application in monolithic integration.

On the brittleness of elementary semiconductors

It is shown that the brittleness of a single-component covalent crystal (diamond, Si, Ge) is due to the "duplicity" of the paired potential of interatomic interaction for elastic (reversible) and for plastic (irreversible) deformation. This leads to the fact that the specific surface energy during plastic deformation of a covalent crystal is more than two times less than the specific surface energy during elastic deformation. Therefore, with a small deformation of a covalent crystal, it is energetically more advantageous to create a surface by irreversible breaking than by reversible elastic stretching. It is indicated that the brittle-ductile transition in a single-component covalent crystal is accompanied by metallization of covalent bonds on the surface. It is shown that the brittle-ductile transition temperature (TBDT) for single-component covalent crystals under static load has an upper limit: TBDT/Tm<0.45, where Tm --- is the melting temperature. Keywords: interatomic covalent bond, brittleness, ductility, elementary semiconductors, brittle-ductile transition.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ ПРЕОБРАЗОВАТЕЛЯ ЧАСТОТЫ С ПРОСТРАНСТВЕННО-ВЕКТОРНОЙ ШИРОТНО-ИМПУЛЬСНОЙ МОДУЛЯЦИЕЙ

The article presents the stages of developing and building a mathematical model for a semi-conductor frequency converter with space vector pulse width modulation, which consists of a power circuit made of power semiconductor elements. The mathematical simulation is performed in the MATLAB/Simulink soft-ware environment. The main principles of the model’s components performance are formulated. Using switching diagrams, calculated data for building a functional management system for the power keys of a frequency con-verter are presented. Based on the simulation results, oscillography records of phase and linear load voltages are obtained. Dependences of output voltage quality on the frequency of pulse width modulation are identified. The main advantages of using space vector pulse width modulation are described in designing sinusoids of output voltage in a frequency converter when working with an active inductive load. The authors draw conclusions on the usage of the vector method for building an output voltage of a frequency converter in the industry.

Application of numerical and graphical methods of analysis in nonlinear resistive circuits of electronic devices

The article discusses the research issues and methods of analysis of semiconductor circuits used in electronic circuits of contactless switching devices, provides analytical, graphic and numerical methods for the analysis of nonlinear semiconductor resistive circuits. The approximations of the Volt-Ampere characteristics (VACh) of semiconductor elements and the solution of the differential equations of state of electrical circuits by a numerical method using a computer are given. Diode, thyristor semiconductor nonlinear resistive circuits with active and inductive loads are considered. In the analysis of steady-state modes and transient processes, numerical methods for solving differential equations of states by the Euler method were used.

OBTAINING DECORATIVE ALKALINE-ACTIVATED CEMENT BY USING SLAGS WITH A HIGH CONTENT OF IRON OXIDE

The soft start device is designed to control the process of starting, operation and stopping of electric motors and enables smooth acceleration, smooth stopping, reduction of the starting current of the motor and coordination of the motor torque with the load moment. The article the control system of the triac device of the smooth start of an asynchronous motor with a constant load moment is considered. The control provides a reduction in the starting current and starting torque of the asynchronous motor. The principle of operation and the main technical parameters of the soft start device are described. The method of reducing power losses in power semiconductor elements of the soft start device is considered. The study of electromechanical processes in the soft start device when working with an asynchronous motor was carried out due to simulated computer modeling in the Matlab / Simulink software environment. The results of simulation modeling are given: oscillograms of input currents of the soft start device, dynamics of speed change and starting torque of an asynchronous motor. In the course of the simulation, it was established that the operation of the soft start device allows to reduce the starting current and starting torque by almost half. It is shown that the adjustment of the time to reach the full opening angle of the power switches of the soft start device and the starting angle of the opening of the power switches, which determines the acceleration dynamics of the asynchronous motor, significantly affects the value of the maximum amplitude value of the current and torque. The results of theoretical studies were implemented in a real physical prototype of the soft start device. The image of the boards of the developed soft start device is shown and its technical characteristics are indicated.

Modelling of basic reversible molecular logic gates and molecular full adder using a molecular diode model

ABSTRACT The modelling of semi-conductor elements in molecular electronics as an emerging technological field requires further development. Using circuit elements, a typical model is presented in this paper. Taking the advantage of this model, a pyridine derivative molecular diode is modelled and the theory behind the components of the molecule model is explained. Subsequently, the physical properties of the proposed pyridine derivative molecular diode, including the electric potential drop along the molecule, rectification ratio, diode current, power consumption, transmission spectrum, and electron density along the molecular diode, are investigated. Then, using the molecular diode model, the basic logic gates including AND, OR, NOT, and XOR gates are modelled and using the basic gate model, the modelling of basic reversible molecular logic gates including Feynman, Toffoli, BVF, and Peres gates are implemented. Moreover, a full adder is modelled using the two Peres gate model.

Assessment of harmonic mitigation performance of electric springs with different inverter topologies

Electric spring (ES) is a new technology inspired by the idea of realization a system that is equivalent to mechanical springs in terms of functionality within power systems. Electric springs are comprised from a DC voltage source, an inverter and an LC filter at the grid side. It can be used effectively in power systems to perform many functions such as voltage regulation, reactive power compensation, demand management and energy storage. On the other hand, due to the semiconductor elements in ES structure, it causes distortion on voltage and current waveforms. However, various control approaches have been proposed in the literature in order to prevent the aforementioned distortions. In this study, three different ESs has been modeled with the inverter topologies chosen from the frequently preferred once used in applications, namely Half-Bridge, Full-Bridge, and Neutral Point Clamped Multi-Level Inverter (NPC-MLI). The disruptive effects of electric springs with different inverter topologies on the grid and their performance in harmonic elimination have been examined through the results obtained from simulations realized in MATLAB/Simulink®.

Family of Nonisolated Fully Soft Switched Bidirectional Converters With Single Switch Auxiliary Circuit

In this article, a family of nonisolated zero voltage switching (ZVS) bidirectional dc–dc converters (BDCs) with simple auxiliary circuit and continuous current at low voltage side source ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V_L$</tex-math></inline-formula> ) is proposed. The auxiliary circuit is only composed of a single switch, a capacitor, and a small inductor which is applied to all proposed nonisolated BDCs to provide soft switching condition for all semiconductor elements. Thus, in terms of components count, the presented converters are superior to other counterpart BDCs. In addition, the continuous current at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V_L$</tex-math></inline-formula> is maintained, while the main and auxiliary switches in both operating modes are turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> at ZVS. Moreover, all diodes turn <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> at zero current switching which mitigate the reverse recovery problem. Hence, a suitable overall efficiency is achieved in all proposed BDCs. The proposed bidirectional buck/boost converter is analyzed for both step-up and step-down operating modes in details and a 100 W converter prototype is implemented to verify the main converter features and the theoretical analysis.

Innovative Bidirectional Isolated High-Power Density On-Board Charge for Vehicle-to-Grid.

This paper deals with developing and implementing a bidirectional galvanically isolated on-board charger of a high-power density. The power density of the new charger was 4 kW/kg and 2.46 kW/dm3, and the maximum efficiency was 96.4% at 3.4 kW. Due to the requirement to achieve a high-power density, a single-stage inverter topology was used. Regarding switching losses, due to the topology of the circuit with so-called hard switching, the switching frequency was set to 150 kHz. A laboratory prototype was built to verify the properties and operating principles of the described charger topology. The on-board charger has been tested in a microgrid test platform. Due to the parasitic properties of the transformer and other electronic components, overvoltage with subsequent oscillations occurred on the primary side of the transformer and damped resonance on its secondary side. These parasitic properties caused interference and especially voltage stress on the semiconductor elements. These undesirable phenomena have been eliminated by adding an active element to the charger topology and a new transistor control strategy. This new switching control strategy of transistors has been patented.

Polarization due to emergent polarity in elemental semiconductor thinfilms under bending

Polarization via strain engineering provides a facial way to functionalize materials. We investigate the origin of electronic polarization in the bent elemental semiconductor thinfilms by combining analytical modeling with quantum mechanical simulation. A bond orbital model reveals a polarity of covalent bonds induced by strain gradient such that polarization along the strain gradient dimension can be induced, giving rise to the flexoelectric effect. At strain gradient nm−1, the net charge differences between the two sides are , and for C, Si and Ge films respectively. On the other hand, due to the emergent bond polarity, the polarization can be effectively tuned by normal strain applied to the bent film, mimicking the piezoelectric effect. Simulations using the generalized Bloch theorem strongly support this revelation. Findings have important implications for delineating the formation of polarization and related phenomena in semiconductors.

An Interleaved Soft Switched High Step-Up Boost Converter With High Power Density for Renewable Energy Applications

In this article, a novel soft switched interleaved boost structure with a simple auxiliary circuit is proposed which is suitable for stand-alone loads or ac grid applications. In this topology, coupled inductors and switched capacitor cells of parallel modules are merged to obtain high voltage conversion ratio. The converter also has the capability of adding extra switched capacitor cells to attain very high voltage gain. To provide soft-switching condition in the wide range of output power, a new zero-voltage transition auxiliary circuit is employed which is responsible for soft switching of both phases and benefits from low conduction losses, the minimum number of semiconductor elements, and only one auxiliary gate-driver. These merits provide very high efficiency at both full-load and light loads. More importantly, no auxiliary magnetic components are utilized by taking advantage of the leakage inductance of coupled inductors for the resonant network. All semiconductor components operate under soft switching alleviating the reverse recovery problem and switching losses. Besides, the converter benefits from common ground between input and output which simplify voltage feedback. The experimental results of the interleaved converter prototype with 400-V output voltage at 400 W and 100 kHz switching frequency are provided. The full load efficiency of 98% was achieved and the power density was observed 1.9 W/Cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Possibilities to reduce the impact of vfd on the quality of electric power in the networks of enterprises and the cost of its use

Purpose. Simulation modeling of internal power supply systems and comparative assessment on its basis of the total distortion coefficients of the sinusoidal voltage curve. Methodology. Methods of simulating modeling of internal power supply systems. Numerous methods for processing the obtained results. Methods for calculating the discrete Fourier transform. Findings. To increase the level of automation of technological processes in industrial electrical installations, frequency converters are widely used. Together with all the advantages of using a variable frequency drive, it leads to a distortion of the sinusoidal shape of the voltage graph. The article evaluates the total distortion factor of the sinusoidal voltage curve for two options for constructing an internal network of an industrial enterprise. The proposed solution makes it possible to improve the shape of the voltage curve by reducing the number of non-linear semiconductor elements in the power supply system and reduce the influence of higher harmonic components on the power grid. At the same time, this makes it possible to reduce the cost of using VFD at the enterprise. Originality. Through experimental research, it has been established that the use of a common rectifier in combination with a common DC bus and individual inverters can reduce the total distortion coefficient of the sinusoidal voltage curve. Practical value. The developed simulation models of the workshop network’s operation make it possible to study the indicators of the electric energy quality both in stationary and in transient modes of operation.

A Single Switch High Step-Up DC-DC Converter Based on Tri-Winding Coupled Inductor for Renewable Energy Applications

This article introduces a novel nonisolated single-switch high step-up DC-DC converter using a tri-winding coupled inductor (TWCL) for renewable energy applications such as PV systems. Also, the voltage multiplier cell (VMC) is used to attain a high voltage gain. The used VMC acts as a passive clamp circuit and reduces the voltage stress across the power switch. So, a low voltage-rated power switch can be used in the presented converter. The suggested topology uses only one power switch with low on-state resistance (RDS-ON), which leads to a simple control circuit and decreases the conduction losses. Highefficiency, operating with low duty cycle, low peak voltage over semiconductor elements, low turns ratio, the number of the coupled inductor, and high voltage conversion ratio are the significant benefits of the recommended DC-DC converter. To show the achievement of the presented structure, operational mode principles, steady-state, efficiency calculations, and comparison results are provided. Finally, a 120 W experimental prototype with 200 V output voltage and 50 kHz switching frequency is built to prove the usefulness of the suggested high step-up converter. The efficiency is measured 92.11% at rated power.

First-principles investigation of a-line Shockley partial dislocations in wurtzite GaN: core reconstruction and electronic structure

Αtomistic simulations based on density functional theory were performed to investigate Shockley partial dislocations, parallel to the <11–20> direction, in wurtzite gallium nitride. The cores of both 30° and 90° Shockley partial dislocations, their possible reconstructions and their electronic structures were analyzed and compared systematically. Shockley partial dislocations were found to have a variety of core structures while exhibiting different bonding states like: deformed Ga–N bonds, Ga–Ga and N–N homo-nuclear bonds, as well as Ga– and N–dangling bonds. We have demonstrated that the core reconstruction of these dislocations is not always energetically favourable in wurtzite GaN, as it is the case in elemental semiconductors. It results from interplay between the energy gain from eliminating dangling and forming homo-nuclear bonds and the energy excess from the induced strain of hetero-nuclear Ga–N bonds within the core. Depending on their core configurations, Shockley partial dislocations are expected to have different electronic behaviours in wurtzite GaN, as they can act either as sources of parasitic luminescence or non-radiative recombination centres, or give pathways to leakage currents. We have demonstrated that deep states associated with dislocations are not due to the dangling bonds, as generally believed, but rather to Ga–Ga bonds in their cores, and that N–N bonds do not lead to any gap states. These results are of high relevance as guidelines in defect engineering strategies aiming at producing dislocations with a particular electronic behaviour in wurtzite GaN.

An integrated of buck and half‐bridge high step‐down converter utilizing single‐stage driving design for high‐efficiency energy conversions

AbstractIn this paper, an integrated of buck and half‐bridge high step‐down converter utilizing single‐stage driving design for high‐efficiency energy conversion is proposed. The proposed converter has the ability to instantly and synchronously transfer energy from input to output within one conversion period. The proposed topology is capable of lowering the primary side voltage of the transformer, so the turns ratio could be reduced. The coupling rate is therefore better along with the leakage inductance. Furthermore, the duty cycle operated in an extreme situation is not necessary. As a combination of the advantages of high step‐down conversion, lower voltage stresses, and fewer amount of semiconductor elements, the feasibility of the proposed topology is verified by the implementation of a 300 W prototype. The proposed integrated topology utilizes the single‐stage energy transfer control algorithm to verify that the proposed experimental circuit has a full load efficiency of 92.4%, in the case of input voltage 380 V and output voltage 5 V, and the maximum efficiency, occurring at 100 W, is 94.55%.

ZVT High Step-Up Boost Converter With Wide Input Voltage and Wide Output Power for Renewable Energy Applications

In this article, a high-efficiency, high step-up dc–dc converter is introduced by utilizing a new soft-switching circuit based on the zero-voltage transition (ZVT) technique. Soft-switching performance is independent of the output load and input voltage. The simple auxiliary circuit benefits from a low number of components. The resonant circuit comprises merely one switch and one small capacitor, and in comparison to the existing ZVT high step-up converters, no extra auxiliary diode and resonant inductor are used to provide soft switching. The proposed auxiliary circuit can be applied to coupled inductor (CI)-based step-up topologies, because of exploiting the leakage inductance of the CI cell in the resonant network. Providing soft-switching performance for all the semiconductor elements alleviates the reverse recovery and switching losses, which considerably enhances the efficiency. The proposed topology is a competitive structure in terms of efficiency, voltage gain ratio, and the number of components due to the mentioned features. The theoretical results are validated on a 200-W laboratory prototype with a 400-V output voltage.

Comparison and Analysis of Impedance According to the Winding Method of Superconducting Element Connected to DC Circuit Breaker

DC Interruption technology is essentially required as DC systems and microgrids have increased. The Interruption technology also includes current limiting technology. Until now, many hybrid Interruption technologies have been proposed in which a semiconductor element or a superconducting element is combined with a mechanical DC circuit breaker. In this paper, an interrupting test was performed by combining a superconductor and a DC circuit breaker. The advantage of circuit breakers combined with superconducting elements is that they do not cause losses and effectively limit the fault current. When the fault occurs, if the fault current exceeds the critical value of the superconducting material, resistance occurs in the superconducting element. The fault current is limited by the resistance generated during quenching and resonates due to the LC divergence oscillation circuit. The current flowing through the mechanical circuit breaker reaches zero-point by resonance. After that, the mechanical breaker is completely opened, and the fault current is interrupted. Superconducting elements exhibit different characteristics depending on their winding method, material, and length. The purpose of this study is to comparatively analyze solenoid and toroid coil type superconducting elements. Both types are made with the same number of turns, permeability, and length. As a result of the experiment, the toroid coil has generated more impedance than the solenoid coil.