Resistance Capacitance Research Articles

A novel carbonized natural silk nanofiber/graphene oxide aerogel for supercapacitor

In this study, we established a novel electrode material for supercapacitors using carbonizing natural silk nanofibers/graphene oxide (SNF/GO) aerogel. Particularly, the SNF/GO electrode fabricated at 800 °C carbonization exhibited unique microstructure, high stability. In terms of its electrochemical performances, the 800 °C SNF/GO electrode showed lower resistance and higher capacitance. After 10,000 cycles of charging, the 800 °C SNF/GO supercapacitor presented remarkable capacitance stability, indicating great potential in supercapacitor and other energy storage systems.

Analysis of Fractional Electrical Circuit Containing Two RC Ladder Elements of Different Fractional Orders

Abstract The study addresses the topic of different fractional orders in the context of simulation as well as experiments using real electrical elements of fractional-order circuit. In studying the two solutions of the resistance-capacitance (RC) ladder circuit of appropriate parameters, different fractional orders of the electrical circuit are considered. Two fractional-order (non-integer) elements were designed based on the Continued Fraction Expansion (CFE) approximation method. The CFE method itself was modified to allow free choice of centre pulsation. It was also proposed that when making individual ladder circuits, in the absence of elements with the parameters specified by the program, they should be obtained by connecting commercially available elements in series or parallel. Finally, the theoretical analysis of such a circuit is presented using state-space method and verified experimentally.

Oxygen vacancy enhancing intrinsic conductivity of rGO@MnO2−x electrode for efficient hybrid capacitive deionization

The poor intrinsic conductivity and serious aggregation of MnO2 has limited its further application in capacitive deionization (CDI). In the present work, GO was introduced as the growth substrate to alleviate the aggregation behavior of MnO2, while oxygen vacancies were created in the MnO2 crystal by calcination to improve the intrinsic conductivity of MnO2. The uniform dispersion and the expanded layer spacing of δ-MnO2 provide larger specific surface area and more active sites for ion adsorption and storage, while the abundant oxygen vacancies in the crystal enhance the intrinsic conductivity and provide convenient ion transport channels for ion movement and transport. The electrochemical tests show that the rGO@MnO2−x electrode presents higher specific capacitance (284 F g−1) and lower equivalent series resistance (1.11 Ω) than those of MnO2 electrode (128 F g−1 and 1.25 Ω). Meanwhile, the desalination tests display that the hybrid GO||rGO@MnO2−x cell demonstrates prominent desalination capacity (58.75 mg g−1) and ultrahigh charge efficiency (95.01%) compared to GO||MnO2 cell (38.25 mg g−1 and 83.81%) in 500 mg L−1 NaCl solution at 1.2 V. The proposed design offers an optional strategy to improve the intrinsic conductivity of MnO2 and enables synthesis of a novel composite to achieve efficient desalination.

Nonlinear compact thermal modeling of self-adaptability for GaN high-electron-mobility-transistors using Gaussian process predictor and ensemble Kalman filter

Thermal issue has been regarded as one of the bottlenecks for GaN high-electron-mobility transistor (HEMT) performance and reliability, which highlights the importance of accurate thermal modeling. In the present work, we propose a GP (Gaussian process)-resistor–capacitor compact thermal model integrated with the ensemble Kalman filter (EnKF) to handle the nonlinear problems attributed to the temperature-dependent properties of GaN HEMTs under large-signal working conditions. The GP predictor is employed for the nonlinear correction term, with strong ability and extendibility to characterize various temperature-dependent relations resulting from different design configurations and materials. The model is identified via the EnKFs by inputting a sequence of channel temperature oscillations induced by imposing a large-signal continuous wave heating source to the device. Furthermore, an adaptation mode is devised for the in situ and timely update of the model parameters to adapt to the thermal variability of GaN devices, avoiding storing a large amount of historical data and repeated offline regressions. The validation of our modeling scheme is conducted through the case study on GaN-on-SiC HEMT’s detailed 3D finite element method simulations.

Well-modulated interfacial ion transport enables D-sorbitol/PEDOT:PSS fibers to sense brain electrophysiological signals in vivo.

A neuroelectrode can be easily prepared using a wet-spun fiber of D-sorbitol/PEDOT:PSS. At a D-sorbitol/PEDOT:PSS weight ratio of 6, the fiber is well-modulated with suitable characters, including the morphology, crystallization, diffusion resistance (179 kΩ), and electric double-layer capacitance (2.72 μF), for sensitive recording of brain activity during somatosensory stimulation and seizures. Additionally, the fiber is highly biocompatible with the brain. This study presents a simple and controllable strategy for the chemical construction of conducting polymer-based neurosensors.

Impact of Current on the Parallel Resistance and Junction Capacitance of Light-Emitting Diodes

Impact of Current on the Parallel Resistance and Junction Capacitance of Light-Emitting Diodes

Импеданс проточной измерительной электрохимической ячейки с системой планарных встречно-штыревых микроэлектродов

The article considers a flow-through electrochemical cell with planar interdigitated microelectrodes intended for impedance studies of liquids. To assess the influence of the cell height and geometric parameters of the interdigitated microelectrodes on the cell impedance, an analytical approach is proposed that uses several levels of modeling electrochemical processes in the cell. At first, an elementary two-dimensional subdomain is distinguished in the cell structure, for which the potential distribution is determined by solving the differential equation of electrical conductivity. Using the obtained potential distribution, the linear parameters of the elementary subdomain, its linear resistance and linear capacitance are determined, on the basis of which the resistance and capacitance of the interdigitated microelectrode system are found. The impedance of an electrochemical cell with interdigitated microelectrodes is determined using its equivalent electrical circuit, which includes the resistance and capacitance of the interdigitated microelectrode system, the capacitance of the double electric layer on the surface of each microelectrode, and the resistances of the interdigitated microelectrode leads. Using the expression for the impedance of the electrochemical cell, its Nyquist and Bode diagrams are determined for different values of the cell height and geometric parameters of the interdigitated microelectrode system. The presented approach can be used to analyze processes in a flow-through electrochemical cell with interdigitated microelectrodes, its design, and the development of methodological support for impedance studies of liquid substances with help of it.

Nonylphenol polybenzoxazines-derived nitrogen-rich porous carbon (NRPC)-supported g-C3N4/Fe3O4 nanocomposite for efficient high-performance supercapacitor application.

In this work, a straightforward and scalable method was used to generate nitrogen-rich porous carbon (NRPC), which was then incorporated with a graphitic carbon nitride and magnetite (g-C3N4/Fe3O4) nanocomposite, fabricated with Fe3O4 nanoparticles as an eco-friendly and economically viable component. The fabricated NRPC/g-C3N4/Fe3O4 nanocomposite was applied as an electrode in supercapacitor applications. The synthesized NRPC/g-C3N4/Fe3O4 nanocomposite, NRPC, g-C3N4, and Fe3O4 were characterized by analytical and morphological analyses. The spherically shaped Fe3O4 nanoparticles were analyzed by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The specific surface area of NRPC/g-C3N4/Fe3O4 was determined to be 479 m2 g-1. All the crosslinked composites showed exceptional electrochemical performance and exhibited a pseudo-capacitance behaviour. In comparison to the Fe3O4 and g-C3N4/Fe3O4 electrodes, the NRPC/g-C3N4/Fe3O4 electrode showed a lower charge-transfer resistance and higher capacitance. The prepared NRPC/g-C3N4/Fe3O4 electrode exhibited the highest specific capacitance of 385 F g-1 at 1 A g-1 compared to Fe3O4 (112 F g-1) and g-C3N4/Fe3O4 (150 F g-1). Furthermore, the cycling efficiency of NRPC/g-C3N4/Fe3O4 remained at 94.3% even after 2000 cycles. The introduction of NRPC to g-C3N4/Fe3O4 improved its suitability for application in high-performance supercapacitors.

An in-depth investigation of lead-free KGeCl3 perovskite solar cells employing optoelectronic, thermomechanical, and photovoltaic properties: DFT and SCAPS-1D frameworks.

Potassium germanium chloride (KGeCl3) has emerged as a promising contender for use as an absorber material for lead-free perovskite solar cells (PSCs), offering significant potential in this domain. In this study, we conducted a density functional theory (DFT) investigation to analyze and assess the structural, electronic, thermomechanical, and optical characteristics of the cubic KGeCl3 absorber. The positive phonon dispersion curve confirmed the dynamical stability of KGeCl3. The elastic constant satisfied the Born criteria, validating the mechanical stability and ductility of solid KGeCl3. The electronic band structure and density of states (DOS) confirmed that the KGeCl3 material is a semiconductor with a direct band gap of 0.754 eV (GGA) and 0.803 eV (mGGA-RSCAN). The study identified key optical parameters, including absorption, conductivity, reflectivity, dielectric function, refractive index, and loss function, revealing the potential suitability of KGeCl3 for solar applications. The Helmholtz free energy (F), internal energy (E), entropy (S), and specific heat capacity (Cv) are computed based on the phonon density of states. Additionally, we investigated twenty-four configurations comprising different combinations of electron transport layers (ETLs) and hole transport layers (HTLs) in SCAPS-1D software. For this purpose, ETLs such as Ws2, ZnSe, PCBM, and C60 and HTLs such as CBTS, CdTe, CFTS, Cu2O, P3HT, and PEDOT:PSS are employed. The highlighted structure, ITO/CBTS/KGeCl3/Ws2/Ni, demonstrates remarkable performance with an efficiency of 22.01%, a Voc of 0.6799 V, a Jsc of 41.439 mA cm-2, and a FF of 78.12%. To analyze photovoltaic (PV) performance, we chose the top four solar cell (SC) configurations. Moreover, a comprehensive examination was conducted to assess the impact of various factors, including the thickness of different layers, capacitance, Mott-Schottky behavior, series and shunt resistance, temperature, and generation-recombination rates, as well as J-V (current-voltage density) and quantum efficiency (QE) characteristics.

EFFECT OF SURFACE TREATMENT ON THE ELECTROCHEMICAL ACTIVITY OF Ti3SiC2/TiC/TiSi COMPOSITE MATERIAL IN THE HYDROGEN EVOLUTION REACTION

The effect of treatment of the surface layer of the Ti3SiC2/TiC/TiSi composite material on its electrochemical activity in the of hydrogen evolution reaction in 0.5M H2SO4 has been studied. Surface treatment has been carried out by chemical etching in solutions of 15, 30, 45% HF for 15, 30, 45 min at 25 and 60 °C. It has been established that the cathodic polarization curves of the Ti3SiC2/TiC/TiSi-electrode without and with surface treatment have a Tafel section with a slope of 0.060–0.076 V and they are characterized by an overvoltage value of 0.20–0.26 V at i = 1 mA/cm2. The rate of the cathodic reaction as a result of treatment increases by ~1.6-9.8 times. The greatest increase is caused by high-temperature etching in a solution of 30% HF for 30 min while stirring the solution. The impedance spectra of the Ti3SiC2/TiC/TiSi-electrode at Tafel region potentials consist of a capacitive semicircle with a displaced center. On the impedance graphs of the treated electrode, a straight section with a slope above 45º was registered in the region of the highest frequencies, indicating the presence of pores in the surface layer of the electrode. To describe the hydrogen evolution reaction on Ti3SiC2/TiC/TiSi, we used an equivalent electrical circuit, the Faraday impedance of which consists of charge transfer resistances R1 connected in series and a parallel R2C2-chain corresponding to the adsorption of atomic hydrogen on the electrode surface. The equivalent circuit also includes the electrolyte resistance Rs and the double layer capacitance impedance, which is modeled by the constant phase element CPE1. It has been shown that the results of polarization and impedance measurements agree satisfactorily with the discharge–electrochemical desorption mechanism with a quasi-equilibrium discharge stage when the logarithmic Temkin adsorption isotherm for adsorbed atomic hydrogen is fulfilled. It has been concluded that the composite material Ti3SiC2/TiC/TiSi in sulfuric acid electrolyte is a promising electrode material for the electrochemical production of hydrogen.

Silicon distyryl-BODIPY hybrid photodiode: moving a step ahead from organic interface layer to type II band alignment

Organic-inorganic heterojunctions are becoming an attractive topic of research for their applications in hybrid photodetectors, solar cells, resistive switching memory devices etc. The easy chemical synthesis and low-cost fabrication for organic thin films come with the benefit of high light absorptivity, high fluorescence quantum yield and band gap tunability along with high charge carrier lifetime that could be combined with the existing silicon-based technology. In this aspect, various organic dyes utilised as an interfacial layer with silicon Schottky junction are reported earlier. However, the photo responses are quite limited. Here, in this report, a Type II Silicon/Distyryl-BODIPY p-n junction has been proposed as an organic-inorganic hybrid photodetector which has not been explored extensively yet. The transformation from a mere organic interfacial layer to band aligned junction enhances the charge carrier separation providing higher photo-responsive behaviour. With the simple spin-coating technique, the Distyryl-BODIPY derivative with phenolic functionalities is coated to fabricate the p-n junction diode. To further improve the performance, pyramidal surface texturization on silicon is deployed using wet chemical etching that supplements the light absorption with internal reflections. Both the devices have been investigated for their photo-response characteristic where a high photo-responsivity of 4353 A W−1 is attained for the textured device as compared to 118 A W−1 for the planar silicon device at a − 3 V bias with an ultra-high specific detectivity of 1012 Jones and 1010 Jones respectively. The behaviours of interfacial states have been demonstrated using the capacitance (C), conductance (G) and series resistance (RS) vs voltage (V) curves at different frequencies. Further calculations of interfacial state density revealed the existence of 1000 times higher interfacial states in planar device leading to lower performance as compared to pyramidal device. The findings in this report suggest that dye-based organic-inorganic heterostructures find potential applications in photodetectors and other optoelectronic devices.

Research Status and Trend of Axis-torsion Two-Component Force Senso

Axis-torsion two-component force sensor can simultaneously detect axial force and torque component information. With the progress of modern engineering technology and the improvement of the requirements for measurement accuracy and dynamic response ability, the sensor is widely used in many fields such as industry, national defense science and technology, and medical treatment. The axis-torsion twocomponent force sensor based on the measurement principles of resistance strain type, capacitance type and magnetostrictive effect is introduced. Because the resistance strain type axis-torsion two-component force sensor has a high degree of accuracy, good stability, simple structure and strong anti-electromagnetic interference ability, the resistance strain type axis-torsion two-component force sensor is the most widely used and the most technologically mature class of sensor. The structural characteristics of the elastic body of the combined and integral axis-torsion two-component force sensor are summarized. At present, the elastic body structure of the axis-torsion two-component force sensor is mainly studied and improved. The purpose is to improve the sensor’s measurement accuracyand reduce the inter-dimensional coupling error, so as to achieve accurate measurement in practical applications. The application status of the axis-torsion two-component force sensor in the cutting force detection, torque coefficient detection of high-strength bolted joints, and quantitative analysis of traditional Chinese medicine acupuncture techniques were analyzed. Finally, combined with the research and application status of the axis-torsion two-component force sensor, the development trend of the axis-torsion two-component force sensor is prospected.

IMPEDANCE ANALYSIS FOR FOUR TYPES OF MINERAL WATER AND AQUADES USING ELECTRICAL IMPEDANCE SPECTROSCOPY (EIS) AT FREQUENCIES OF 1 Hz - 50 kHz

The Electrical Impedance Spectroscopy (EIS) method can be used to identify minerals in mineral water. The EIS method measures the impedance of a material by injecting alternating current in a certain frequency range, which is non-invasive and non-destructive. This study aims to analyze the impedance of mineral water and aquades based on the influence of the dissolved content using EIS equipment that provides flexibility in adjusting the desired frequency spectrum. The study used a frequency range from 1 Hz to 50 kHz with a four-electrode configuration. The measurement graph results were analyzed using Bode graph with impedance plot and phase shift angle to determine the impedance characteristics of mineral water. Equivalent circuit modeling helped to identify the electrochemical properties of materials such as the Warburg circuit, Constant Phase Element (CPE), and Randles circuit. The results show that the aquades has a higher impedance compared to the four mineral waters. Additionally, the four mineral waters exhibit varying impedances, attributed to their respective mineral content. Mineral water is characterized by an impedance that is dominated by Warburg impedance (Zw) at low frequencies, charge transfer resistance (Rct) and double layer capacitance (Cdl) at middle frequencies, and electrolyte resistance at high frequencies. However, the impedance of aquades dominated by electrolyte resistance (Re) at low frequency and Re+Rct at high frequency.

Three-dimensional cross-linked sugarcane bagasse carbon material: A substitute for graphene with excellent performance in capacitive deionization and highly efficient Cu2+ removal

Capacitive deionization (CDI) is a high-performance, low-energy consumption, and environmentally friendly water treatment technology with a broad application prospect in heavy metal removal. Selecting electrode materials with high capacitance and low resistance is essential for improving CDI's desalting efficiency. This article discusses the utilization of sugarcane bagasse (C-N-X) and the production procedures of CDI materials. The unique 3D cross-linked structure of C-N-X provides excellent mass transfer properties and significant advantages in capacitance and conductivity. The results of X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectrometer (FTIR) show that bagasse biochar with graphene-like structure and abundant functional groups provides active sites for Cu2+ removal. In this paper, C-N-X is first used as CDI electrode material to remove Cu2+. Electrochemical tests show that the specific capacitance of C-N-X is still stable at about 47 F g−1, and the removal capacity of Cu2+ (25 mg L−1) reaches 66.79 mg g−1 within 4 h after 700 cycles. The experimental results and DFT calculations confirm the adsorption selectivity of C-N-700 for Cu2+.

Electrochemical Frequency Modulation: Investigation of Double Layer Capacitance and Solution Resistance

Electrochemical frequency modulation (EFM) is increasingly finding acceptance for the estimation of corrosion current and the Tafel parameters due to the fact that it does not cause damage to the specimen under examination. In addition, EFM assumes the open-circuit potential corresponds to the corrosion potential of the specimen. However, the current methods do not consider the influence of the double layer capacitance and solution resistance in determining the corrosion parameters. In this study we have thoroughly investigated the effect of these variables in determination of the corrosion characteristics. Two approaches involving determination of the current vs time and harmonics using a semi-analytical and numerical approach were investigated. The data show a high degree of agreement between the two approaches. In addition, our method also allows for the determination of the corrosion potential.

Investigating the Effect of Plasma Parameters on the Dielectric Constant of Sicoh Thin Films Grown by PECVD Using Dimethyldimethoxysilane

The demand for high-performance, low-power, and high-density semiconductor devices has led to the reduction in size of semiconductor chips, resulting in resistance-capacitance (RC) delay. To mitigate the RC delay, low dielectric constant (low-k) insulators have been developed, with the focus on developing new materials with lower dielectric constant. In this report, we present our investigation into the effect of electron density and temperature on the reduction of dielectric constant in SiCOH thin films, utilizing dimethyldimethoxysilane (DMDMS) as a variable with respect to pressure. Our results reveal that both electron density and temperature decline with increasing pressure due to localized electron kinetics and increased inelastic collisions between electrons and neutral species in the chamber, respectively. Our findings also show that the dielectric constant and refractive index of SiCOH thin films decrease at low electron density and temperature. Quadrupole mass spectroscopy reveals that CH3 radicals dissociate less at higher pressures, while Fourier transform infrared spectroscopy confirms an increase in Si-CH3 bonds in SiCOH thin films with increasing pressure. Our findings provide insights into the relationship between electron density and temperature and the dielectric constant of SiCOH thin films, which can contribute to the development of low-k insulators for high-performance semiconductor devices for applications such as big data, mobility, and the Internet of Things (IoT).

Novel T-Shaped Gate Structure of AlGaN/GaN HEMTs on Si for RF Application

Due to the high electron saturation velocity and breakdown electric field, GaN-based high electron mobility transistors (HEMTs) have been widely used in high frequency and power application, such as telecommunication, satellite communication, and radar system [1]. Since first demonstration of AlGaN/GaN HEMTs in 1993 [2], the RF performance of these device has continuously improved by the progress on epitaxy and device scaling technology [3].The current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) from the small-signal equivalent circuit of the HEMT are derived by the following equations [4].From these equations, it can be concluded that in order to achieve high frequency operation, HEMTs should be designed with a T-shaped gate structure that simultaneously achieves low gate resistance (Rg) and low parasitic capacitance (Cgs and Cgd). However, there are complex fabrication processes to form the T-shaped gate. Typically, the T-shaped gate structure is implemented through electron beam lithography process using a tri-layer resist such as PMMA/PMGI/PMMA, which requires multiple exposures or developments. Multiple exposures can cause overlay errors that can significantly affect the T-shaped gate with smaller gate lengths [5]. Also, it is difficult to obtain an undercut structure that enables a good lift-off and guarantees a high yield due to the need for precise dose control. In addition, since the T-shaped gate has an unstable structure in which a narrow foot supports the weight of a wide head, the gate may collapse during a subsequent process.In this work, we fabricated a novel T-shaped gate using the negative e-beam resist HSQ, which offers a simple T-shaped gate fabrication process. The HSQ that was exposed to e-beam is located underneath the gate head and on both sides of the gate foot in our novel T-shaped gate design, providing a robust structure. The HSQ-assisted gate HEMTs exhibit comparable DC/RF performance compared to conventional T-shaped gate HEMTs. Acknowledgement This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MIST) (No. NRF-2021M3C13097672).

Impact of Parasitic Gate Capacitance on RF Performance in GaN-Based HEMTs for X-Band Applications

GaN-based high-electron-mobility transistors (HEMTs) are intensively researched for high-power radio frequency (RF), low noise, and aerospace applications, thanks to their high breakdown electric field, high carrier mobility and density at the hetero-interface, and wide bandgap [1-2]. For the improvement of RF performance, various approaches have been reported, including T-gate structure [3-4], surface passivation [5], n+-regrown source and drain contact [6], thin barrier structure [7], and graded-channel [8]. Among them, the T-gate structure has been extensively employed for the reduction of the gate resistance (Rg ) and thereby improvement of the RF performance. However, the usage of the wide T-gate structure enlarges parasitic gate capacitance components, which deteriorates the RF performance. As a result, one should pay careful attention to the dimension of the wide T-gate structure to reduce Rg as much as possible, not to enlarge the parasitic gate capacitance components. This motivates us to explore the optimum dimension of the wide T-gate structure in GaN-based HEMTs for X-band RF applications.To investigate the detailed impact of the gate resistance and parasitic gate capacitance components, we fabricated LG = 0.15 μm GaN-based HEMTs with various dimensions of the T-gate head from 0.5 to 0.8 μm during an e-beam lithography process step. The unit gate width (WG ) and number of gate finger (NF ) were 100 μm and 2, respectively.For comparison of the device characteristics with respect to the dimension of the gate head, DC and RF measurements were conducted for the fabricated GaN-based HEMTs with various dimensions of T-gate head. The DC characteristics in terms of the threshold voltage (VTH ), the maximum transconductance (gm,max ), and the saturation drain current (Id,sat ) were almost identical, regardless of the dimension of the T-gate head. On the contrary, the current-gain cut-off frequency (fT ) and maximum oscillation frequency (fMAX ) were improved by 26.5% and 21.0%, respectively, when the T-gate head size was reduced from 0.8 to 0.5 μm.In an effort of explore the origin of the dependence of the T-gate head on the RF performance, we have carried out small-signal modeling to extract the parasitic gate capacitance and gate resistance components from the measured RF data. As the T-gate head size was reduced from 0.8 to 0.5 μm, the gate-source parasitic capacitance component (Cgs_par ) was reduced by 19%, while the gate resistance component was increased by 32%. In our device design and fabrication, it turned out that the reduction of Cgs_par was more beneficial than the increase of Rg , leading to the improved RF performance with the gate head size decrease.In this work, our systematic research revealed that, unlike earlier reports [3-4], the reduction of the parasitic gate capacitance was essential for the improvement of the RF performance as opposed to the reduction of the gate resistance in LG = 0.15 μm GaN-based HEMTs for X-band RF applications. Acknowledgement This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MIST) (No. NRF-2021M3C1C3097672).

Study on Morphology Control and N-Doping of Porous Carbon Cathode for Zinc-Ion Hybrid Supercapacitor

The growing use of renewable energy accelerates research on energy storage systems (ESSs) to accommodate the distributed nature of power sources and fluctuation in supply and demand. The commercially adopted system for ESSs is lithium-ion batteries (LIBs), which are actively studied for recent years. However, the use of rare resources such as Li, Ni and Co, as well as volatile and flammable organic electrolytes, cause environmental problems and fire hazards. Therefore, new type of environmentally friendly and safe ESSs are needed to meet the future demand.In this regard, the aqueous zinc-ion hybrid supercapacitors (ZHSCs) are assumed as the remarkable candidate for ESSs. ZHSCs consist of battery-type Zn metal anode and capacitor-type carbon cathode with different ion storage mechanisms. Because they have unique design of electrodes, they can combine the advantages of existing batteries and supercapacitors such as high energy/power density and long cycle lifespans. In addition, the use of Zn metal has lots of benefits compare to Li-based electrodes, for example, Zn has low standard potential (-0.76 V vs. standard hydrogen electrode), high theoretical gravimetric/volumetric capacity (820 mAh g-1 and 5845 Ah/L) and relatively low cost.In ZHSCs, they store energy through an electric double-layer capacitive mechanism in which Zn2+ ions or anions are adsorbed on the surface of carbon cathode while Zn2+ ions are inserted/extracted in Zn metal anode, or a pseudo-capacitive mechanism generated by redox reaction with functional groups on the carbon surface. To achieve higher electrochemical performance of ZHSCs, previously reported research focused on modifying carbon cathode with highly porous structure or introducing heteroatoms. The porous carbon with abundant micropores (<2nm) and mesopores (2-50nm) can be used to provide high surface area for ions to adsorb/desorb and serve as channels for electrolytes and ions to diffuse rapidly. Besides, modifying surface of carbon cathode by doping heteroatoms (N, O, S, B, P) can improve wettability and conductivity of electrode and produce additional capacitance from redox reactions.However, although many researchers have studied to reform carbon cathode, they rarely study the effect of carbon’s morphology on its electrochemical performance. In the electrode level, irregularly shaped carbon could result in poor volumetric capacitance and high resistance properties caused by low mass loading and poor particle contact. The proposed morphology to solve these issues is spherical shape. As the spherical particles have no edges, they hardly damaged and have good powder fluidity between particles, leading to higher tap density or electrode density. They can also provide short diffusion path for ions to move compared to irregularly shaped particles, since the thin electrode can be made using the same amount of active material. This can enhance overall electrochemical performance of ZHSCs by lowering internal resistance and improving high rate capability of electrodes.In this respect, we suggest “spherical and uniform shape” carbon cathode along with the pore modification and heteroatom doping to compare the factors affecting electrochemical performance in ZHSCs. Thus, we prepared three different types of mesoporous carbons, which are spherical mesoporous carbon foam (S-MCF), N-doped spherical mesocellular carbon foam (S-MCF-N) and irregular shaped mesocellular carbon foam (MSUF-C). The improved electrode density of ZHSCs are achieved in spherically-controlled carbons (S-MCF and S-MCF-N) with 2.9 times higher tap density than irregularly shaped carbon (MSUF-C). Besides, the introduction of nitrogen to carbon (S-MCF-N) affords abundant active sites on the surface of carbon, increasing electrical conductivity and inducing additional pseudo-capacitance. Figure 1

(Invited) Hybrid Bonding for 3D Applications: Improvements and Limitations

Wafer direct bonding has attracted considerable concerns since it takes advantage of the ability to achieve strong adherence between flat, clean, and smooth surface without the use of intermediate materials. This technology experienced a consequent rise with the More than Moore's law. With this trend, added value to devices is provided by incorporating functionalities that do not necessarily scale according to "Moore's Law”. Indeed, this aims to realize three-dimensional (3D) integration systems by stacking devices and interconnecting them using Through-Silicon-Via (TSV) or Cu-Cu interconnections. Hybrid bonding is preferred to other chip stacking technologies because Cu-Cu hybrid bonding is easily capable of scaling down and present excellent reliability results.Hybrid bonding is key technology to address several applications especially images sensor. Even more specialized applications or better performances could be obtained through hybrid bonding pitch reduction [1]. High quality bonding for 3D technology has been demonstrated using an accurate wafer bonding tool with optimized metrology [2]. The total overlay values reached is below 110 nm with residuals values below 80 nm and scaling inferior to 0.5 ppm for interconnect pitches from 6.9 µm down to 0.6 µm. The electrical properties have been checked and confirmed the robustness of the fine pitch hybrid bonding module and the stability of the bonding interface [3]. The latest process and hardware developments have made it possible to greatly reduce scaling. However, distortion remains the most complicated parameter to optimize. It is strongly linked to the design of the chip (number of metal levels, stress...). Today, a minimum critical dimension design rule should be respected to avoid short between front side and backside layers and this is preventing pixel shrink. To reduce pixel size, distortion value needs to be decreased. For that purpose, in situ monitoring of the bonding wave is necessary as well as bonding chucks multiple vacuum zones in order to achieve homogenous bonding wave propagation.Even if hybrid bonding integration and performance have been considerably improved, we can notice that thermal budget is a main limitation for this technology. Indeed, to reach strong bonding energy which is mandatory for subsequent mechanical manufacturing; a bonding anneal of 800°C is required. By using plasma treatment prior bonding, anneal temperature can be decreased to 400°C. However, some devices cannot withstand such thermal budget because of thermosensitive materials integration (GST or quantum dots for example). To overcome this limitation, many studies have been performed on developing low temperature direct bonding process. Surface activated bonding (SAB) is a promising method to achieve high bonding energy at room temperature, but chemical surface treatments (as amino-alcohol organic molecule for example [4]) are easiest to implement for mass volume production and allows highly strong bonding at 200°C that can stand high stress process steps (grinding, CMP and dicing).Although specific plasma or surface preparation could decrease the required annealing temperature, the copper oxide will limit electrical performances with annealing below 250°C for standard hydrophilic bonding. That is why, new ECD Cu deposition like oriented nano-twin Cu is very promising to facilitate oxygen diffusion. [5][1] AYOUB, B., LHOSTIS, S., MOREAU, S., et al. Impact of Process Variations on the Capacitance and Electrical Resistance down to 1.44 µm Hybrid Bonding Interconnects. In : 2020 IEEE 22nd Electronics Packaging Technology Conference (EPTC). IEEE, 2020. p. 453-458.[2] DETTONI.Florent, DELOFFRE, Emilie, GRAUER, Yoav, et al. Advanced overlay metrology for CIS bonding applications. ECTC 2023 to be published[3] AYOUB, Bassel, LHOSTIS, Sandrine, MOREAU, Stéphane, et al. Sub 1µm Pitch Achievement for Cu/SiO 2 Hybrid Bonding. In : 2022 IEEE 24th Electronics Packaging Technology Conference (EPTC). IEEE, 2022. p. 418-424.[4] FOURNEL, Frank, CALVEZ, Aziliz, LARREY, Vincent, et al. Impact of an Amino-Alcohol Organic Molecule on SiO2 and Si Bonding Energy. ECS Transactions, 2020, vol. 98, no 4, p. 3.[5] CHEN, Chih, JUANG, Jing-Ye, CHANG, Shih Yang, et al. Low-temperature Cu-to-Cu direct bonding enabled by highly (111)-oriented and nanotwinned Cu. In : 2019 6th International Workshop on Low Temperature Bonding for 3D Integration (LTB-3D). IEEE, 2019. p. 38-38.