Conventional Current-voltage Research Articles

Ultrasound-enabled adaptive protocol for fast charging of lithium-ion batteries

Abstract This paper introduces an ultrasound-assisted multi-stage constant current (UA-MSCC) charging protocol to enhance the charging performance of lithium-ion batteries. In this approach, ultrasound is applied during the final portion of each multi-stage constant current (MSCC) charging phase. Experimental results demonstrate that ultrasound decreases the internal resistance of pouch cells by up to 7%, leading to significant increase in charging capacity during each MSCC stage. The overall charging time is reduced by 26% compared to the conventional constant current constant voltage (CCCV) protocol. The performance improvement delivered by this ultrasound-assisted charging approach is especially large when the battery is charged at low temperatures and to a partial capacity. Notably, the application of ultrasound improves the coulombic efficiency to levels comparable to that at the room temperature when charging in cold environments (0°C). This approach can be applied to commercial batteries to immediately improve their charging performance, and can be seamlessly integrated into battery management systems. Unlike approaches that necessitate electrode material modifications or electrolyte additives, which require a long development time, this UA-MSCC charging protocol offers a practical and easily applicable solution for improving the battery charging performance.

Health-conscious optimal control of Li-ion cell using simplified full homogenized macro-scale model

This article presents the optimal charging of a Li-ion cell based on a simplified full homogenized macro-scale (FHM) model. A solid electrolyte interface (SEI) layer model is included in the simplified FHM model to quantify cell degradation. With these models, a multi-objective optimal control problem subject to constraints from safety concerns is formulated to achieve health-conscious optimal charging. This constrained optimal control problem is converted to a nonlinear programming problem (NLP). A nonlinear model predictive control (NMPC) strategy is adopted by solving the NLP at each sampling time using the pseudo-spectral optimization method. The effect of the input current upper bound on the cell film resistance Rfilm and state of health (SoH) reveals that Rfilm and SoH are more sensitive to input current upper bound at lower values of input current upper bound. Simulation results show that the simplified model and pseudo-spectral method are crucial for reducing the computational load of the model. The proposed algorithm is more efficient in reducing health degradation than the conventional constant current constant voltage (CCCV) charging algorithm since it can explicitly handle the film resistance and capacity as health parameters. Multiple cycle charging simulations revealed that the health-conscious algorithm decreases health degradation and increases battery life.

Reliable Accessibility of Intermediate Polarization States in Textured Ferroelectric Al0.66Sc0.34N Thin Film

AbstractFerroelectric materials are promising candidates for neuromorphic computing synaptic devices due to the nonvolatile multiplicity of spontaneous polarization. To ensure a sufficient memory window, ferroelectric materials with a large coercivity are urgently required for practical applications in highly scaled multi‐bit memory devices. Herein, a remarkable reliability of intermediate ferroelectric polarization states is demonstrated in a textured Al0.66Sc0.34N thin film with a coercive field of 2.4 MV cm−1. Al0.66Sc0.34N thin films are prepared at 300 °C on Pt (111)/Ti/SiO2/Si substrates using a radio frequency reactive sputtering method. Al0.66Sc0.34N thin films exhibit viable ferroelectricity with a large remanent polarization value of >100 µC cm−2. Through the conventional current–voltage characteristics, polarization switching kinetics, and temperature dependence of coercivity, the reproducibility of multiple polarization states with apparent accuracy is attributed to a small critical volume (3.7 × 10−28 m3) and a large activation energy (3.3 × 1027 eV m−3) for nucleation of the ferroelectric domain. This study demonstrates the potential of ferroelectric Al1‐xScxN for synaptic weight elements in neural network hardware.

A new prospect to measure the built-in potential for photodiodes

We present a novel approach to determine the built-in potential for photodiodes, which depends on the excitation of the photodiode by a pulsed or modulated light under forward bias. The proposed method was tested for commercially available photodiodes and the measurement results were compared with the values, which were obtained by conventional current–voltage and capacitance–voltage measurements. It was found that the proposed method gave consistent results with current–voltage and capacitance–voltage measurements. For the confirmation of the accuracy of this method, temperature dependent measurements were also performed for Si photodiode in a temperature range of 298−333 K to compare the obtained built-in potential values with theory. This analysis showed that the results of the proposed method were more reliable than the conventional measurements.

Comparison of Two Different Battery Charging Methods

Abstract This paper describes charging of battery stack using model predictive control (MPC) algorithm. Temperature model and hybrid electrical model are used in algorithm. The battery stack consists of four serially connected valve-regulated lead-acid (VRLA) batteries. The objective of the optimization is to charge the proposed battery stack without violating the constraints in order to maintain the battery health. Validation of MPC algorithm for battery charging is performed using comparison between closed-loop MPC simulations and obtained characteristics of actual MPC charging. Previously, the conventional constant current constant voltage (CCCV) algorithm was proved as good, taking into account the degradation effects but not considering the speed of the charging. The comparison between charging of proposed battery stack using MPC algorithm and CCCV algorithm is performed and the comparison in charging proves MPC algorithm as better compared to the CCCV algorithm.

Design of Stable Digital V2 Controllers for the Synchronous Noninverting Buck–Boost Converter

The non-inverting buck-boost converter is suitable for battery powered applications as it can operate in buck, buck-boost, and boost modes. Traditional current mode and voltage mode controllers are generally employed to control it in closed loop. It is well established that a peak V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> controller provides superior load-transient performance compared to conventional current mode and voltage mode controllers. However, a peak V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> controller cannot be applied to the non-inverting buck-boost converter during boost and buck-boost modes because of its non-minimum phase behavior. This paper proposes a digital peak V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> controller which can work effectively during all the modes. The proposed controller samples both the inductor current and output voltage at the rate of the switching frequency. Thus, digital implementation of this controller does not need high-speed ADCs. Unlike traditional peak V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> controllers, the proposed controller does not depend on effective series resistance (ESR) of the output capacitor. An average model-based small-signal model of the proposed controller is presented. Analysis shows that a sufficient current loop gain can make the system behave like a first order system. This enables the designer to employ a PI controller to achieve superior transient performance in all the modes. Furthermore, fast-scale stability analysis of the controller is carried out using approximate discrete-time models to derive an analytical stability boundary of slope compensation. A non-inverting buck-boost converter prototype is fabricated and the proposed controller is implemented using an FPGA platform. Experimental results show close correlation with the analysis.

Comparison of Fitting Current–Voltage Characteristics Curves of FinFET Transistors with Various Fixed Parameters

In the deep submicron regime, FinFET successfully suppresses the leakage current using a 3D fin-like channel substrate, which gets depleted and blocks possible leakage as the gate is applied with a bias wholly wrapping the channel. Fortunately, a scanning photo-lithography using extensive ultraviolet (EUV) and multi-mask task carefully resolves critical dimension issues. The ensuing anisotropic plasma dry etching is somehow a subsequent challenging process, which consumes the edge of original ‘I’-shape epitaxial silicon and causes dimension loss, and thus produces fin-like bodies as prepared channels. In order to protect the transistors from malfunction due to dimension over-etching, fin width is taken to be 120 nanometers, while the channel lengths vary. The prepared transistors are measured and characteristic curves are fitted for analysis. Measured current versus voltage characteristic curves are fitted with three parameters (transistor geometry constant, threshold voltage, and Early voltage) in the conventional current-voltage formula, which are allowed to vary as the short channel effects or process-related issues are taken into account. In this paper, one of the three is deliberately set to be fixed for a transistor, and the others are freely chosen and determined to reach minimum variation. Various conclusions through comparisons and analysis may give important feasible applications in the future.

Robust Tracking Control of a Three-Phase Bidirectional Charger for Electric Vehicle

This paper presents a robust control strategy for an electric vehicle's three-phase off-board bidirectional AC-DC battery charger. The conventional constant current (CC) and constant voltage (CV) charging mode are considered to provide a fast-charging performance for the batteries. The bidirectional charger also allows using of the vehicle as an energy storage system for the grid i.e., charging during the peak-off times and delivering the energy back to the grid during peak times of electrical consumption. In discharging mode, the bidirectional charger maintains constant active power flow to the grid with a given reference. For both cases, user of a robust state feedback controller with integral action is made in the DQ-synchronous frame. The set of stabilizing gains of this controller are determined by a linear matrix inequality (LMI)-based optimization so that the convergence time to steady stead is minimized in the occurrence of the parametric uncertainties of the L-filter. The efficacy of the proposed controller is verified through simulation and experimental results on 102.4 V Lithium iron phosphate (LiFePO4) batteries.

Scanning tunneling spectroscopy of two-dimensional Dirac materials on substrates with a band gap

In this paper we show that conventional current-voltage spectroscopy can provide quantitative information on the dispersion relation of the low-energy electrons of monoelemental group-IV two-dimensional (2D) Dirac materials provided that (1) the 2D material is placed on a substrate with a band gap and (2) the density of states of the scanning tunneling microscopy tip is constant. We have derived an expression for the differential conductivity of a monoelemental group-IV 2D Dirac material that is placed on a substrate with a band gap. The differential conductivity scales as $|E\ensuremath{-}{E}_{D}|{e}^{b|E\ensuremath{-}{E}_{D}|},$ rather than the commonly assumed $|E\ensuremath{-}{E}_{D}|$ scaling, where $E$ and ${E}_{D}$ refer to the energy of the electrons and the Dirac point, respectively. The parameter $b$ is inversely proportional to the Fermi velocity.

Deep-Learning-Assisted Physics-Driven MOSFET Current-Voltage Modeling

In this work, we propose using deep learning to improve the accuracy of the partially-physics-based conventional MOSFET current-voltage model. The benefits of having some physics-driven features in the model are discussed. Using a portion of the Berkeley Short-channel IGFET Common-Multi-Gate (BSIM-CMG), the industry-standard FinFET and GAAFET compact model, as the physics model and a 3-layer neural network with 6 neurons per layer, the resultant model can well predict IV, output conductance, and transconductance of a TCAD-simulated gate-all-around transistor (GAAFET) with outstanding 3-sigma errors of 1.3%, 4.1%, and 2.9%, respectively. Implications for circuit simulation are also discussed.

Pulsed Nanoelectrospray Ionization Boosts Ion Signal in Whole Protein Mass Spectrometry

Electrospray ionisation (ESI) is renowned for its ability to ionise intact proteins for sensitive detection by mass spectrometry (MS). However, the use of a conventional direct current ESI voltage can result in the formation of relatively large initial droplet sizes, which can limit efficient ion desolvation and sensitivity. Here, pulsed nanoESI (nESI) MS using nanoscale emitters with inner diameters of ~250 nm is reported. In this approach, the nESI voltage is rapidly pulsed from 0 to ~1.5 kV with sub-nanosecond rise times, duty cycles from 10 to 90%, and repetition rates of 10 to 350 kHz. Using pulsed nESI, the performance of MS for the detection of intact proteins can be improved in terms of increased ion abundances and decreased noise. The absolute ion abundances and signal-to-noise levels of protonated ubiquitin, cytochrome C, myoglobin, and carbonic anhydrase II formed from standard denaturing solutions can be increased by up to 82% and 154% using an optimal repetition rate of ~200 kHz compared to conventional nESI-MS. Applying pulsed nESI-MS to a mixture of four proteins resulted in the signal for each protein increasing by up to 184% compared to the more conventional nESI-MS. For smaller ions (≤1032 m/z), the signal can also be increased by the use of high repetition rates (200–250 kHz), which is consistent with the enhanced performance depending more on general factors associated with the ESI process (e.g., smaller initial droplet sizes and reduced Coulombic repulsion in the spray plume) rather than analyte-specific effects (e.g., electrophoretic mobility). The enhanced sensitivity of pulsed nESI is anticipated to be beneficial for many different types of tandem mass spectrometry measurements.

Electron transport characteristics of FeGa, Ni/n-Si junctions by impedance spectroscopy

In this work, we have investigated electron transport across Galfenol (Fe x Ga 1-x ) and Nickel-based Schottky contacts deposited onto n-Si substrates using conventional DC current-voltage (I–V) measurements and have uniquely studied the effects of improper back contact causing additional bias dependent Resistance-capacitance (R–C) components using AC Impedance spectroscopy by choosing proper equivalent circuit models. Junction barrier height and ideality factor were obtained from DC current-voltage characteristics, and bias dependent impedance measurements have been carried out. From Impedance spectroscopy analysis the magnitudes of depletion layer capacitance and barrier height have been calculated and have been compared for both the junctions, and the effect of additional components has been distinguished. Negative capacitance behaviour at lower frequencies and higher forward bias regime has been observed, which might be attributed to interface states in presence of injected charge carriers and by choosing an equivalent circuit having inductor-resistor (R-L) type relaxation, better fit of experimental Nyquist plots of FeGa Schottky junction have been achieved. • FeGa and Nickel based Schottky Junctions have been deposited onto n-Si substrates using RF magnetron Sputtering. • Junction parameters have been calculated using conventional DC and, AC Impedance measurements. • Using equivalent circuit; bias dependency of both Schottky and Ohmic interfaces for has been studied.

Non-enzymatic simultaneous detection of acetylcholine and ascorbic acid using ZnO·CuO nanoleaves: Real sample analysis

A facile wet-chemical technique used to prepare the zinc oxide doped copper oxide nanoleaves (ZnO·CuO nanoleaves) in alkaline phase. ZnO·CuO nanoleaves were examined using a variety of conventional techniques for example UV–Visible, FTIR, XRD, FESEM equipped XEDS, and XPS. A non-enzymatic sensor was prepared with modification of a slightly deposited of ZnO·CuO nanoleaves onto a flat GCE, which fabricated through a conducting nafion polymer matrix in order to detect selective acetylcholine and ascorbic acid simultaneously. Analytical performances such as sensitivity, LOD, LOQ, LDR, and durability of the selective acetylcholine and ascorbic acid sensors were examined through a conventional current–voltage method. Calibration graphs of acetylcholine and ascorbic acid sensors were found linear (R2 = 0.9049 and 0.9201) over a good concentration range (100.0 pM–100.0 mM) respectively. Sensitivity (317.0 and 94.94 pAμM-1cm−2), LOD (14.7 and 12.0 pM), and LOQ (490.0 and 367.0 mM) of acetylcholine and ascorbic acid sensors were calculated correspondingly from the slope of the linear portion of calibration graph. Preparation of ZnO·CuO nanoleaves using wet-chemical technique is an excellent approach for the advancement of nanomaterial based on sensor development in support of enzyme free detection of biological molecules for the safety in healthcare and biomedical fields. This expected sensor applied for the specific determination of acetylcholine and ascorbic acid in real samples (Human, mouse, and rabbit serum, orange juice, and urine) and found satisfactory and acceptable results.

Dynamic Electrical Pathway Tuning in Neuromorphic Nanowire Networks

AbstractNeurobiology‐inspired phenomena such as winner‐takes‐all competition and critical dynamics have been recently reported to arise in neuromorphic nanowire networks. These are unique systems where interactions between memristive elements creates emergent conductance pathways between discrete electrodes. This mode of operation can offer substantial advantages to create a truly concomitant plastic‐static system for integration in neuromorphic devices. However, critical aspects such as pathway controllability and stability are yet to be explored. In this study, pathway formation in self‐assembled neuromorphic networks formed by Ag nanowires decorated with TiO2 nanoparticles is investigated. Direct visualization of pathway formation through a neuromorphic network is attained using the lock‐in thermography technique. Using this technique, it is demonstrated that how networks preserve information from previously used pathways through increased local junction connectivity. This effect directly reshapes subsequent formation of pathways whenever the spatial location of the electrodes is dynamically changed. Combining these results with conventional current–voltage measurements, which show that the network electrically acts as a volatile switching memristor, a unique interaction between short‐term and long‐term memory arises. This produces unexpected collective dynamical states of potentiation and inhibition of network conductance whenever different spatiotemporal signals are dynamically fed to the network.

Design and implementation of adaptive battery charging method considering the battery temperature

Today, batteries are widely used in mobile devices, vehicles and military applications. Batteries meet the energy needs of the equipment on the vehicle in military vehicles which is one of the application areas. During the military vehicle is stationary, the vehicle engine must not work for camouflage. Therefore, it needs a battery charge circuit. Controlled charging/discharging of the batteries is very important for the cycle life and safety of the batteries. Many conventional battery chargers units charge it without considering the battery temperature. In this study, adaptive battery charging method design and circuit is taken into consideration, considering the battery temperature. The adaptive battery charging algorithm has been applied to charge the batteries of military vehicles and in accordance with military standards (MIL-STD-1275-E voltage surges and MIL-HDBK-454B electronic equipment standard). In this study, experiments with different charge rates have been made and conventional constant current and constant voltage method and proposed adaptive battery charging method result are compared. Experimental results show that the battery temperature decreases 15°C with the proposed charging method. This adaptive battery charging method has been shown to prevent overheating of the battery.

Investigation, analysis and comparison of current-voltage characteristics for Au/Ni/GaN Schottky structure using I-V-T simulation

Abstract In this work, we have presented a theoretical study of Au/Ni/GaN Schottky diode based on current-voltage (I-V) measurement for temperature range of 120 K to 400 K. The electrical parameters of Au/Ni/GaN, such as barrier height (Φb), ideality factor and series resistance have been calculated employing the conventional current-voltage (I-V), Cheung and Chattopadhyay method. Also, the variation of Gaussian distribution (P (Φb)) as a function of barrier height (Φb) has been studied. Therefore, the modified ( ( ln ⁡ ( I 0 T 2 ) − ( q 2 σ s 0 2 2 kT 2 ) = ln ⁡ ( AA * ) − q ∅ B 0 kT ) vs . ( 1 kT ) ) ( {( {\ln \left( {{{{\rm{I}}_0 } \over {{\rm{T}}^2 }}} \right) - \left( {{{{\rm{q}}^2 \sigma _{{\rm{s}}0}^2 } \over {2{\rm{kT}}^2 }}} \right) = \ln ( {{\rm{AA}}^*} ) - {{{\rm{q}}\emptyset_{{\rm B}0} } \over {{\rm{kT}}}}} ){\rm{vs}}.( {{1 \over {{\rm{kT}}}}} )} ) relation has been extracted from (I-V) characteristics, where the values of ΦB0 and A Simul * {\rm{A}}_{{\rm{Simul}}}^* have been found in different temperature ranges. The obtained results have been compared to the existing experimental data and a good agreement was found.

Temperature Effect on Electronic Parameters of CuPc/n-Si Heterojunction

This paper reports the effect of temperature on electronic properties of Al/CuPC/n-Si heterostructure diodes. The diode-controlling parameters are extracted from the conventional current–voltage (I–V) curve of the fabricated Al/CuPc/n-Si heterojunction diode. The calculated parameters, such as barrier height (Φb), ideality factor (n), and series resistance (Rs), obtained from experimental results, show significant temperature dependence and demonstrate improvement in their values in the temperature ranging from 300 K to 330 K. These extracted values are further verified by determining them while using Cheung functions and Norde’s technique. The values of n and Φb show that the former and the latter decreases and increases, respectively, with increasing temperature. This is attributed to thermionic emission theory. The fabricated heterojunction diode shows thermal stability, and the space-charge-limited current (SCLC) transport is the most frequently occurring process in the fabricated device at all temperatures.

A General Approach to Probe Dynamic Operation and Carrier Mobility in Field‐Effect Transistors with Nonuniform Accumulation

AbstractRevealing the intrinsic electrical properties is the basis of understanding new functional materials and developing their applications. However, in nonideal field‐effect transistors (FETs), conventional current–voltage characterizations do not accurately probe charge transport, particularly for newly developed semiconductors. Here, a generalized gated four‐probe (G‐GFP) technique is developed, which detects dynamic changes in carrier accumulation and transport. The technique is suitable for exploring the intrinsic properties of semiconductors in FETs with arbitrary contacts and in any operational regimes above the threshold. Application to simulated transistors confirms its accuracy in probing the evolution of channel potential, drift field, and gate‐dependent carrier mobility for devices with a contact‐limited operation and disordered semiconductors. Comparative experiments are performed based on FETs with various materials, device structures, and operational temperatures. The G‐GFP technique proves to exclude the various injection properties, to detect in situ how carriers are accumulated, and to clarify carrier mobility of the semiconductors. In particular, the well‐known “double‐slope” features in the current–voltage relations are controllably generated and their origins are identified. The approach could be used to explore electronic properties of newly developed materials such as organic, oxide, or 2D semiconductors.

Comparison of hydrogen detection by WOx/SiC and Pt/WOx/SiC structures using amperometric and potentiometric modes of measurement

Hydrogen sensors were fabricated with a well-known structure, formed by depositing WOx films (with or without an additional Pt overlayer) onto SiC substrates. These sensors differed in terms of the morphology and nanostructure of the WOx films, which were pulsed laser deposited (PLD) under varying conditions. The sensory characteristics of WOx/SiC and Pt/WOx/SiC samples were analyzed using conventional current–voltage measurements. In addition, the possibility of detecting an electrical signal in these structures without applying an external voltage (EMF-powered mode) was investigated. The sensor response strongly depended on the qualities of the metal oxide film, including its strength, uniformity, continuity, and adhesion to the SiC substrate. Optimization of the PLD allowed the formation of triclinic WOx<3 and monoclinic W18O49 films with relatively good quality. The current measured at 300 °C by the amperometric method for the WOx/SiC sensors increased by 15 times (up to 24 μA at a voltage of 0.5 V) when 2% H2 was added to air. For the Pt/WOx/SiC sensors, the current increased by up to 100 times. The highest response to 2% H2 in the potentiometric mode of measurement was found for the WOx/SiC sensor containing W18O49 film. The EMF-initiated voltage increased by >27 times. The highest voltage detected for an external load of 1 kΩ was ~400 μV. The Pt film deposition markedly worsened the sensory properties of Pt/WOx/SiC structures measured by the EMF-powered mode. Possible mechanisms of the appearance of the EMF in the prepared structures are considered.

Direct evaluation of influence of electron damage on the subcell performance in triple-junction solar cells using photoluminescence decays

Tandem solar cells are suited for space applications due to their high performance, but also have to be designed in such a way to minimize influence of degradation by the high energy particle flux in space. The analysis of the subcell performance is crucial to understand the device physics and achieve optimized designs of tandem solar cells. Here, the radiation-induced damage of inverted grown InGaP/GaAs/InGaAs triple-junction solar cells for various electron fluences are characterized using conventional current-voltage (I–V) measurements and time-resolved photoluminescence (PL). The conversion efficiencies of the entire device before and after damage are measured with I–V curves and compared with the efficiencies predicted from the time-resolved method. Using the time-resolved data the change in the carrier dynamics in the subcells can be discussed. Our optical method allows to predict the absolute electrical conversion efficiency of the device with an accuracy of better than 5%. While both InGaP and GaAs subcells suffered from significant material degradation, the performance loss of the total device can be completely ascribed to the damage in the GaAs subcell. This points out the importance of high internal electric fields at the operating point.