Capacitance Field Research Articles

Engineering negative capacitance Fully Depleted Silicon-on-insulator FET for improved performance

Achieving sub-60 mV/decade subthreshold swing in short channel Negative Capacitance Field Effect Transistor (NCFET) devices requires the utilization of a thicker Ferroelectric (FE) layer, where due to an interplay between the thickness and polarization gradient of the FE material, undesired effects such as Hysteresis and Negative Differential Resistance (NDR) may be seen in the device characteristics, which limits the expected improvement in the performance. In this work, with a Fully Depleted Silicon-on-insulator (FDSOI) baseline architecture, at a channel length of 14 nm, through utilizing a drain-sided Paraelectric (PE) spacer along with reduced drain doping while laterally splitting the gate stack into two halves such that the nature of the material on the source-sided and drain-sided stack is Ferroelectric and Paraelectric respectively, we show an NDR-free output characteristic. This also enables the incorporation of a thicker FE layer, without observing Hysteresis in the transfer characteristics, while ensuring significantly high Gain (gm/gds) along with sub-60 mV/decade subthreshold swing, at lower supply voltages.

Shape optimisation of basin insulator for DC gas insulated switchgear/gas insulated transmission lines based on artificial bee colony algorithm

AbstractThe surface charge accumulation on the basin insulator is a particular problem in high‐voltage direct current (HVDC) gas insulated switchgears (GIS) and gas insulated transmission lines (GIL), which restricts the development and application of extra/ultra high‐voltage (EHV/UHV) technology. The surface charge distribution and anti‐flashover performance are closely related to the insulator shape. To obtain the optimal basin insulator, a shape optimisation model based on artificial bee colony algorithm was established, and the minimisation objective functions based on capacitive (initial) electric field distribution and resistive (steady‐state) electric field distribution were respectively constructed. The optimisation results of the two objective functions were calculated, and the electric field and charge distribution on the surface of the insulator before and after optimisation were evaluated and compared using the simulation model. The results indicated that the optimisation based on the capacitive electric field can significantly inhibit the surface charge accumulation, and the optimised insulator can significantly reduce the surface normal electric field and make the distribution of the tangential electric field more uniform, and the maximum tangential electric field can be reduced by 10%; the optimisation based on resistive electric field can achieve similar results, but requires more computational resources. Based on the results, the ‘anti‐charge’ basin insulator structure suitable for the DC field was given.

DFT based atomic modeling and Analog/RF analysis of ferroelectric HfO2 based improved FET device

In this study, we systematically investigated the Analog/RF and linearity parameter of SM DGNCFET (single metal double gate negative capacitance field effect transistor) and DM DGNCFET (double metal double gate negative capacitance Field effect transistor) with the help of Cogenda Visual TCAD simulator, and also demonstrated the enhancement in the electronic and optical properties of Si-doping bulk structure by using the Quantum ATK. The analog parameters are enhanced for SM DGNCFET such better performance of switching ratio 279 times better, DIBL 54% lower, SS decay, and some other improved parameter transconductance, TGF and Radio frequency parameter is also enhanced, transconductance frequency product (TFP) for improving reliability and stability of device. Linearity parameters like that second and third order transconductance (gm2, g m3), voltage intercept point for 2nd, 3rd. Tran Blaha modified Becke Johnson (TB-mBJ) approxiamation gives the accurate band gap of crystal. In DFT based atomic study, 12.5% of Si doping in bulk structure reveals better results for ferroelectric HfO2 based crystal in the direct band gap of bandstructure is zero, Density of state (DOS) is also improved conductivity for Si doping crystal. Hence, Si doping in crystal structure is also better for conductivity.

Measurement of switching transient overvoltages with a capacitive electric field sensor

This paper presents a case study of measurements of switching transient overvoltages using a capacitive electric field sensor. The system was developed and installed in a substation after the failure of a surge arrester during the energization of a 420 kV transmission line. First, the closing operation was simulated in an electromagnetic transient simulation program to estimate the switching transient overvoltages for this event. Then, the concept and design of the measurement system are explained. The system calibration performed in the high-voltage laboratory is presented. Afterward, the installation of the measurement system in the substation is discussed, with a special focus on the calibration of the voltage ratio considering the physical configuration where it is installed. Finally, the measurement results are presented and compared with simulations. The results show that the transient overvoltages caused by the energization of the transmission line should not cause the failure of the surge arrester. The measurement system has been demonstrated to be capable of measuring switching transient voltages of a 420 kV transmission line and can be considered a flexible solution for the long-term monitoring of transient overvoltages in substations.

Optimization of Subthreshold Swing and Hysteresis in Hf0.5Zr0.5O2-Based MoS2 Negative Capacitance Field-Effect Transistors by Modulating Capacitance Matching.

Negative capacitance field effect transistors made of Hf0.5Zr0.5O2 (HZO) are one of the most promising candidates for low-power-density devices because of the extremely steep subthreshold swing and high open-state currents resulting from the addition of ferroelectric materials in the gate dielectric layer. In this paper, HZO thin films were prepared by magnetron sputtering combined with rapid thermal annealing. Their ferroelectric properties were adjusted by changing the annealing temperature and the thickness of HZO. Two-dimensional MoS2 back-gate negative capacitance field-effect transistors (NCFETs) based on HZO were prepared as well. Different annealing temperatures, thicknesses of HZO thin films, and Al2O3 thicknesses were studied to achieve optimal capacitance matching, aiming to reduce both the subthreshold swing of the transistor and the hysteresis of the NCFET. The NCFET exhibits a minimum subthreshold swing as low as 27.9 mV/decade, negligible hysteresis (∼20 mV), and the ION/IOFF of up to 1.58 × 107. Moreover, a negative drain-induced barrier lowering effect and a negative differential resistance effect have been observed. This steep-slope transistor is compatible with standard CMOS manufacturing processes and attractive for 2D logic and sensor applications as well as future energy-efficient nanoelectronic devices with scaled power supplies.

Capacitive Electrode-Based Electric Field Treatments on Redox-Toxic Iron Deposits in Transgenic AD Mouse Models: The Electroceutical Targeting of Alzheimer's Disease Feasibility Study.

Iron accumulation in the brain accelerates Alzheimer's disease progression. To cure iron toxicity, we assessed the therapeutic effects of noncontact transcranial electric field stimulation to the brain on toxic iron deposits in either the Aβ fibril structure or the Aβ plaque in a mouse model of Alzheimer's disease (AD) as a pilot study. A capacitive electrode-based alternating electric field (AEF) was applied to a suspension of magnetite (Fe3O4) to measure field-sensitized reactive oxygen species (ROS) generation. The increase in ROS generation compared to the untreated control was both exposure-time and AEF-frequency dependent. The frequency-specific exposure of AEF to 0.7-1.4 V/cm on a magnetite-bound Aβ-fibril or a transgenic Alzheimer's disease (AD) mouse model revealed the degradation of the Aβ fibril or the removal of the Aβ-plaque burden and ferrous magnetite compared to the untreated control. The results of the behavioral tests show an improvement in impaired cognitive function following AEF treatment on the AD mouse model. Tissue clearing and 3D-imaging analysis revealed no induced damage to the neuronal structures of normal brain tissue following AEF treatment. In conclusion, our results suggest that the effective degradation of magnetite-bound amyloid fibrils or plaques in the AD brain by the electro-Fenton effect from electric field-sensitized magnetite offers a potential electroceutical treatment option for AD.

Comparative study of Negative Capacitance Field Effect Transistors with different doped hafnium oxides

Negative Capacitance Field Effect Transistors are well known for their superior performance over MOSFET and are a viable candidate to succeed the baseline FET in time ahead. We have studied the performance of 32 nm planar MOSFET with doped hafnium dioxide as a ferroelectric material. The functioning of the NCFET is entirely dependent on the equivalence between the ferroelectric and MOS capacitance. Our simulation results clearly indicated that the Sr doped HfO2 has close capacitance matching with MOS capacitance, when compared with other dopant material (Si, Al and Zr). This also reflects in the performance parameters (drain current and transconductance characteristics) of the device designed. Also, we have designed a resistive load inverter with doped hafnium dioxide, Sr doped among them has an edge over the other ferroelectric material in terms of noise margin and static power dissipation.

Analysis and Mitigation of Negative Differential Resistance effects in Double-Gate Silicon-on-Insulator Negative Capacitance Field Effect Transistor with improved analog performance

Negative Capacitance Field Effect Transistors (NCFETs) offer the possibility of enhancing channel length scalability, with a key challenge being to ensure hysteresis and Negative Differential Resistance (NDR) free behavior. In this context, through TCAD-based simulations, for a symmetric Double-gate Silicon-on-Insulator (DG-SOI) baseline architecture with a Metal–Ferroelectric–Insulator–Semiconductor (MFIS) configuration, we first examine the root cause of NDR as being the FE layer with a small number of strongly coupled domains, which allows the drain to lower the surface potential (ΨSs) and internal gate voltage (Vint) on the source side. With this understanding of NDR, the inclusion of a paraelectric (PE) layer on the drain side of the gate stack, by splitting the stack into two halves laterally, while keeping the thickness of the stack unchanged, minimizes the drain’s influence on the source-sided electrostatics. This results in the mitigation of NDR effects along with superior analog performance parameters, thus making these FE–PE gate stack-based NCFET devices suitable for analog circuit applications.

The Potential of ferroelectric HfO2 for Next-Generation Memory Device: Ferroelectric Properties and Applications

The discovery of the ferroelectricity of HfO<sub>2</sub> in 2011 has opened up new avenues for the application of ferroelectric technology. With the stability of ferroelectricity in a few nm scales, HfO<sub>2</sub> has become a valuable material for the development of next-generation electronic memory devices. The unique structure of HfO<sub>2</sub> gives rise to various ferroelectric properties and behaviors that can be utilized in different types of devices such as ferroelectric field effect transistors (FeFETs), negative capacitance field effect transistors (NCFETs), ferroelectric tunnel junctions (FTJs), and ferroelectric capacitors (FeCAPs). In this review, we explore the potential of HfO<sub>2</sub> for the high-density storage of data and low-energy consumption in next-generation devices. We demonstrate the operating principles and strengths of HfO<sub>2</sub> in various device applications, shedding light on how this material can help address the electronics industry's current challenges.

The System’s Point of View Applied to Dielectrophoresis in Plate Capacitor and Pointed-versus-Pointed Electrode Chambers

The DEP force is usually calculated from the object's point of view using the interaction of the object's induced dipole moment with the inducing field. Recently, we described the DEP behavior of high- and low-conductive 200-µm 2D spheres in a square 1 × 1-mm chamber with a plane-versus-pointed electrode configuration from the system's point of view. Here we extend our previous considerations to the plane-versus-plane and pointed-versus-pointed electrode configurations. The trajectories of the sphere center and the corresponding DEP forces were calculated from the gradient of the system's overall energy dissipation for given starting points. The dissipation's dependence on the sphere's position in the chamber is described by the numerical "conductance field", which is the DC equivalent of the capacitive charge-work field. While the plane-versus-plane electrode configuration is field-gradient free without an object, the presence of the highly or low-conductive spheres generates structures in the conductance fields, which result in very similar DEP trajectories. For both electrode configurations, the model describes trajectories with multiple endpoints, watersheds, and saddle points, very high attractive and repulsive forces in front of pointed electrodes, and the effect of mirror charges. Because the model accounts for inhomogeneous objectpolarization by inhomogeneous external fields, the approach allows the modeling of the complicated interplay of attractive and repulsive forces near electrode surfaces and chamber edges. Non-reversible DEP forces or asymmetric magnitudes for the highly and low-conductive spheres in large areas of the chamber indicate the presence of higher-order moments, mirror charges, etc.

Hybrid of pyrazine based π-conjugated organic molecule and MXene for hybrid capacitive deionization

In this work, we report a hybrid material of pyrazine based π-conjugated organic molecule, hexaazatrinaphthalene (HATN), and MXene. In this hybrid, MXene serves as a conductive substrate and HATN provides multiple electroactive sites, which are jointly combined to build a unique 3D structure with more ion transport channels for accelerating the charge transfer and ion diffusion rates. The as-obtained HATN/MXene composite displays a superior desalination capacity of 57.5 mg g−1 with an excellent desalination rate of 13.2 mg g−1 min−1 and good long-term stability. This work provides a meaningful guidance for designing and applying organic molecules in capacitive deionization field.

Flexible boron-doped diamond spiral electrode for application in brain–computer interface based on steady-state visual evoked potential

We propose a flexible boron-doped diamond (BDD) spiral electrode for electroencephalography (EEG) recording and introduce the application of a flexible BDD-based EEG cap in brain–computer interfaces (BCI). The B-doping difference of diamond crystal planes in flexible polycrystalline BDD electrodes makes them act like a microelectrode. Hydrogen bonds between hydroxy fatty acid in the cuticle and BDD surface terminal and electrostatic adsorption between BDD-boron sites and the cuticle enhance the capacitive electric field. Combining a skin-conformal BDD electrode cap with the simplest feature extraction and classification coding can record highly stable EEG in steady-state visual evoked potential (SSVEP), with a high average SNR of 8.6 dB. The BCI system demonstrated competitive accuracy and information transfer rate in five channels in the occipital and parietal areas. Collectively, the BDD-based SSVEP-BCI system offers unique advantages for the real-time monitoring of brain signals, neurological rehabilitation, and disease diagnosis.

Impact of temperature on a ferroelectric interfaced negative capacitance double gate junctionless accumulation mode field effect transistor-compact model

Ferroelectric interfaced negative capacitance field effect transistors are gaining popularity for low power applications; however, as temperature is a constant influencing factor, further study is required to comprehend how these devices are influenced. Through a proposed compact model, this paper analytically investigates the influence of temperature on a ferroelectric interfaced negative capacitance double gate junctionless accumulation mode field effect transistor. This device integrates the benefits of negative capacitance with the junctionless accumulation mode structure. An extensive comparison of the proposed device is made with the existing structure to evaluate the benefits offered by the ferroelectric layer at different temperatures. The Landau–Khalatnikov equation and Pao–Sah integral are employed to obtain the surface potential and drain current model with temperature variation. Various key parameters of the device have been analysed extensively by varying the temperature from 200 to 500 K. It has been found that internal voltage amplification declines as temperature rises, but the sub-threshold swing increases from 46 to 72 mV decade −1 with an increase in temperature. Additionally, with a progressive rise in temperature, the loss of gain and degradation of gate capacitance are observed.

Pulse Capacitive Coupling Electric Field Regulates Cell Migration, Proliferation, Polarization, and Vascularization to Accelerate Wound Healing.

Objectives: Accelerating wound healing using continuous exogenous electrical stimulation is limited due to some serious side effects, including thermal damage. Many previous studies based on direct current contact stimulation may cause chemical burns or blisters, thereby increasing patients suffering. The aim of this study was to develop a safer and more convenient pulse capacitive coupling electrical field (PCCEF) stimulation to accelerate wound healing. Approach: A PCCEF-generating platform was self-designed to facilitate wound healing. The promoting effects and appropriate pulse width were explored by applying PCCEFs (54 mV/mm, 60 Hz) of different pulse widths to various cells involved in wound healing and mouse models for 2 h daily. Results: PCCEFs of ≥10 μs pulse width showed marked promotion of the migration and proliferation of human dermal fibroblasts and HaCaT cells, enhanced the M2-type polarization and YPA/TAZ expression of macrophages, and facilitated the wound healing of mouse models. Comprehensive histological results suggested that PCCEF of 100 μs pulse width exerted the most positive effects. Innovation: A safe and effective PCCEF was developed to promote wound healing, which prevented prolonged stimulation and averted direct contact. Conclusion: PCCEF accelerated wound healing, especially at the optimal 100 μs pulse width, and was expected to be translated to clinical application, helping alleviate patient suffering, while reducing side effects.

Investigation on the Negative Capacitance Field Effect Transistor with Dual Ferroelectric Region

This paper proposes a new structure of the negative capacitance field effect transistor (NCFET), which features of the dual ferroelectric region (DFR) when compared to the conventional NCFET. The dual ferroelectric region with FE1 region and FE2 region forms a non-uniform voltage amplification effect, leads to the significantly improvement of the gate control ability and modulates the electric characteristics of the NCFET. The mechanism of the voltage amplification effect, polarization reversal, channel surface electric field, and ferroelectric polarization intensity distributions are investigated. The influences of the ferroelectric parameters α and β on the electric characteristics are discussed. The results show that the DFR-NCFET is able to obtain a subthreshold swing (SS) below the Boltzmann limit (60 mV/dec) by increasing the ferroelectric parameter α of the FE2 region.

Geometrical Optimization of Printed Interdigitated Electrode Sensors to Improve Soil Moisture Sensitivity

Printing electronics allows us to fabricate low-cost, simple sensor networks. Distributed soil moisture sensors in agriculture industry will result in better water management practices; however, price and reliability do not allow for ubiquitous availability. Here, we demonstrate the fabrication of low-cost, flexible, interdigitated electrode (IDE) soil moisture sensors with the electrode widths of 537, 877, 1055, 1204, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1916~\mu \text{m}$ </tex-math></inline-formula> on polyimide (PI) substrates using a silver nanoparticle (Ag NP) ink. The sensors were tested in sandy textured soil with a volumetric water content ranging from 0.05 to 0.25 m3/m3. Analytically, the sensitivities of all the sensors are expected to be equal, as the proposed mechanisms dictate that the capacitance should depend linearly on the dielectric constant of the moist soil. However, we found the sensitivity for the widest IDE, which measured <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1916~\mu \text{m}$ </tex-math></inline-formula> to be 442 pF/H2O volumetric percentage, whereas the sensitivity for the sensor with 537- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> -wide electrodes to be only 221 pF/H2O volumetric percentage. We hypothesized that the increase in sensitivity can be directly related to the increase in the capacitive fringing field height, which results in increased sensing volume for the widest IDE. The increased sensing volume leads to increased water molecule polarization, increasing the overall capacitance change with respect to changing water content. To validate the hypothesis, we conducted electric fringing field experiments to observe the trend between the maximum fringing field height and the electrode width of an IDE. Results confirmed that increased sensing volume was caused by the increased fringing field height of the electrode in an IDE.

FE/PE/DE gate stack enabling improved analog performance in partially Junction-less NCFETs

Given the short-channel effect immunity of junction-less architectures, further improvement in device performance can be obtained by using a Negative Capacitance based gate stack over such baseline devices. By benchmarking the baseline device, which is a partially Junction-less MOSFET structure, essentially a combination of the Junction-less and Bulk MOSFET device architectures, with experimental data, we then investigate the relative effect of the inclusion of a Ferroelectric (FE) material and Ferroelectric-Paraelectric (FE-PE) stack, respectively, on the existing dielectric (DE) gate stack of the baseline device, resembling a more practical Metal-Ferroelectric-Insulator-Semiconductor (MFIS) NCFET (Negative Capacitance Field Effect Transistor) structure. By ensuring Hysteresis-free transfer characteristics, positive output conductance and Sub-threshold Slope/Threshold Voltage invariability to drain voltage, the FE layer thickness and power supply voltage (maximum drain–source voltage) of the FE-DE and FE-PE-DE gate stacks are determined, which are nearly equivalent capacitively and therefore show similar digital device performance, with the FE-PE-DE gate stack based NCFET showing significantly better analog device performance.

Effect of shifted gate stack engineering over negative capacitance tunnel field effect transistor (NCTFET)

In this work, the performance of negative capacitance field effect transistor is closely investigated with different source material to improvise the transfer characteristics and sub-threshold swing. Tunnel Field Effect Transistor (TFET) being a strong competitor of conventional MOSFET for low power applications has its abilities to pull down Subthreshold Swing (SS) below fundamental limit but it has its own limitations of lower ION current and existence of ambipolar region for lower VGS voltage range. This ambipolar behavior is strongly seen in case of silicon source NCTFET but when source material is replaced with Germanium, a heterojunction is formed at source channel junction, and because of that, improvised result is obtained in terms of steeper subthreshold slope and ION/IOFF ratio. This work compares the transfer characteristics obtained in case of Si-Source and Ge-Source Negative Capacitance Tunnel Field Effect Transistor (NCTFET). The results obtained indicates that heterojunction NCTFET gives a subthreshold swing of 56.6 mV dec−1 and enhances ION/IOFF ratio to 0.24 × 108 in magnitude.

Study of scaling effect of ferroelectric gate stack in planar InGaAs MOSFET

AbstractNegative capacitance field effect transistors is found to be a promising option for low power VLSI devices in the advanced technology node. In this article, through extensive numerical simulation, we report the scaling effect of ferroelectric gate stack, channel thickness and gate length on electrostatic integrity, DC, analog and RF performance of InGaAs quantum well MOS transistor. The different DC and analog figure of merits such as on current (), switching ratio (), threshold voltage roll‐off, sub‐threshold swing (SS), trans‐conductance (), transconductance efficiency () of the test device has been analyzed for different ferroelectric layer thicknesses and compared with the baseline device. We have investigated RF performance such as gate capacitance, unity‐gain cut‐off frequency and small signal voltage gain of the device. Improvement in DC and analog figure of merits is proportional to the ferroelectric layer thickness. However, for higher values of ferroelectric thickness, the hysteresis effect gradually became prominent. MOS transistor with optimum ferroelectric layer thickness shows the negligible amount of threshold voltage roll‐off and improved transconductance‐frequency product compared to the baseline device. In presence of ferroelectric layer, the effect of channel thickness variation on device performance is reduced. The role of ferroelectric gate stack is found to be more prominent at shorter gate length.

Study on the effects of alternating capacitive electric fields with different frequencies on promoting wound healing

Some researches to facilitate wound healing by using electrical stimulation are based on electric current stimulation, which may cause secondary damage and the imbalance of the microenvironment in vivo. In this study, alternating capacitive electric field (ACEF) was applied via a self-designed system so as to avoid direct contact with cells and to maintain stable microenvironment for cell growth. The influences of 58 ​mV/mm ACEFs with various frequencies of 10, 60 and 110 ​Hz on epidermal cells, fibroblasts and macrophages which involve in wound healing were comprehensively explored. The results suggested that ACEFs of 10, 60 and 110 ​Hz all significantly promoted the proliferation of human dermal fibroblasts (HDFs) and human epidermal keratinocyte cell line (HaCaT) cells, and 60 ​Hz ACEF furtherly accelerated the migration of these two kinds of cells. Moreover, ACEFs of all different studied frequencies facilitated M2-type polarization of macrophages, and YAP/TAZ expression of macrophages were enhanced under the stimulations of 10 and 60 ​Hz ACEFs. The enhancements in cell activity, migration rate and M2-type polarizability indicated that 58 ​mV/mm ACEFs especially at 60 ​Hz possessing potentially affirmative applications for wound healing without the risks of secondary damage and microenvironment imbalance.