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Herein, spin‐polarized calculation is performed based on density‐functional theory in the frame of generalized gradient approximation to examine the quantum capacitance (CQ) and surface charge storage of graphene(G)‐based supercapacitor electrodes modified with molybdenum, sulfur, nitrogen, and monovacancy. In total, 15 electrode models, including graphitic doping, monovacancy doping, and Mo adsorption on pristine and single‐vacancy graphene structures are analyzed. In the results, it is demonstrated that vacancy defects and N/S/Mo doping enhances the CQ of graphene. Among all configurations, pyrrolic‐S (d1S) shows the lowest CQ performance due to few states at the Fermi level. Electrodes with Mo adsorption exhibit the highest CQ, particularly when Mo is adsorbed at the top site of graphene. However, formation and adsorption energy calculations suggest that Mo is more likely to adsorb at hollow sites. Optimally, Mo can be most effectively utilized by loading it onto vacancy or N/S‐decorated vacancy sites. The significant contribution of Mo's 4dz2 and 4s states to CQ, along with the charge‐redistribution around the Mo complexes, may facilitate proton‐coupled electron transfer to enhance pseudocapacitance. In these findings, valuable insights into designing high quantum capacitance of 2D materials with electroactive sites for improved energy storage are offered. [ABSTRACT FROM AUTHOR]

A model has been developed and patterns of mutual influence of the electrophysical parameters of a transistor structure with a two-dimensional channel, due to the self-organization of charge and capacitive properties under conditions of charge instability, have been obtained. Transition metal dichalcogenides are considered as a material for a two-dimensional channel. The influence on the electrical parameters of a transistor structure with a two-dimensional semiconductor channel of the band gap of the channel material, the thickness of the gate dielectric, and the capacitance of interface states is considered. It is shown that under conditions of instability caused by an increase in the capacitance of interface states, the dependence of the electrochemical potential, electron concentration and quantum capacitance on the potential of the field electrode has an abrupt form. The results obtained are explained by the fact that, under conditions of instability, an increase in the capacitance of interface states leads to a mismatch between the electrical neutrality condition and the Fermi-Dirac statistics at certain val ues of the gate potential due to the limited nature of the density of states of the two-dimensional channel, which leads to the manifestation of a charge imbalance. The resulting effect is similar to the metal-semiconductor transition and can be attributed to bistable critical phenomena. The developed model and the results obtained can be used in computer-aided design systems for the element base of micro- and nanoelectronics.

The time dynamics of charge accumulation at the electrochemical interface between graphene and water is important for supercapacitors, batteries, and chemical and biological sensors. By using impedance spectroscopy, we have found that measured capacitance (Cm) at this interface with the gate voltage Vgate ≈ 0.1 V follows approximate laws Cm~T1.2 and Cm~T0.11 (T is Vgate period) in frequency ranges (1000–50,000) Hz and (0.02–300) Hz, respectively. In the first range, this dependence demonstrates that the interfacial capacitance (Cint) is only partially charged during the charging period. The observed weaker frequency dependence of the measured capacitance (Cm) at frequencies below 300 Hz is primarily determined by the molecular relaxation of the double-layer capacitance (Cdl) and by the graphene quantum capacitance (Cq), and it also implies that Cint is mostly charged. We have also found a voltage dependence of Cm below 10 Hz, which is likely related to the voltage dependence of Cq. The observation of this effect only at low frequencies indicates that Cq relaxation time is much longer than is typical for electron processes, probably due to Dirac cone reconstruction from graphene electrons with increased effective mass as a result of their quasichemical bonding with interfacial molecular charges. [ABSTRACT FROM AUTHOR]

Results of research in the quantum capacitance C q of quasi-2D-crystals are presented. The detected extraordinary behavior of C q manifests itself in the existence of such energy ranges in which it is practically equal to zero. The causes for the existence of such ranges are: (a) dimensional quantization as a result of the nanoscale of the van der Waals gap, (b) a certain value of the width of the allowed zone in the plane of the layers, which is determined by the value of the effective mass. Intercalation and external electric field are effective factors capable of changing the position of ranges. Thus, in a system connected in a series of electrostatic and quantum capacitances, the resulting capacitance will significantly depend on the C q behavior. Comparative analyses of structures, chemical bonds, majority of coinciding characteristics of physical quantities in graphite, transition metal dichalcogenides (TMD), and layered crystals A3B6 allow us to assert that the obtained qualitative conclusions can be applied for each of them. Calculations of density of states (DOS) of quasi-2D crystals performed by authors within the framework of the improved Kohn–Sham density functional theory (DFT), namely the DFT taking into account the van der Waals forces in it, show a step-like form of DOS qualitatively similar to ours. [ABSTRACT FROM AUTHOR]

Versatile properties of electric double layer supercapacitors such as high output power, safety, high efficiency and durability have gained so much attention for use as energy storage systems. On the other hand their applications have been limited due to an attributed low energy density. It therefore necessary to improve their quantum capacitance in an effective way. In this research, we have investigated the effects of monovacancy and divacancy, nonmetal doping and adsorption of transition metals (Co, Cu, Ni and Zn) on the quantum capacitance of monolayer SiC using first principles calculations. The calculated results show that, incorporating boron in defected 2D-SiC significantly improves the CQ of monolayer silicene. The corresponding CQ values for 1st, 2nd, 3rd and 4th boron substitutions are 59.4, 82.3, 110.2 and 79.4 µF/cm2 respectively, which were found to be good for anode materials for supercapacitors. Moreover, transitions metals adsorbed monolayer SiC were also found to significantly improve the CQ value with high output of 139.3 µF/cm2. Finally, embedding of these TMs (Co, Cu, Ni and Zn) in 2D SiC will provide better alternative to the use of toxic TMs embedded systems such Ti, Mo, Ba and so on. [ABSTRACT FROM AUTHOR]

Recently, the air pollution problem has become more serious issue due to its pernicious effects on human health. One of the most harmful pollutants, carbon monoxide (CO) has been adsorbed on the graphene for gas-sensing applications. In order to overcome these challenges, the proposed work demonstrates the impact of different numbers of CO molecules adsorption for different widths of graphene. The analysis suggests that the tetralayer demonstrates ∼69.2% better strength in adsorption than monolayer graphene for multiple pollutants, and is also found to be suitable for band-gap-related applications. Moreover, graphene has been studied as an electrode material due to its high surface area and good conductivity. The higher conductivity of porous graphene results in higher charge storage capability due to more conducting channels that play a major role in calculating the parasitic values. For more conducting channels, it is observed that the percentage change in quantum resistance and inductance are reduced by 21.62% and 26.67%, respectively for 10 atoms w.r.t. 8 atoms wide porous graphene. The quantum capacitance is increased by 11.5% for 10 atoms w.r.t. 8 atoms wide porous graphene that results in improved charge storage capability of graphene. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials promise advances in electronic devices beyond Moore's scaling law through extended functionality, such as non-monotonic dependence of device parameters on input parameters. However, the robustness and performance of effects like negative differential resistance (NDR) and anti-ambipolar behavior have been limited in scale and robustness by relying on atomic defects and complex heterojunctions. In this paper, we introduce a novel device concept that utilizes the quantum capacitance of junctions between 2D materials and molecular layers. We realized a variable capacitance 2D molecular junction (vc2Dmj) diode through the scalable integration of graphene and single layers of stearic acid. The vc2Dmj exhibits NDR with a substantial peak-to-valley ratio even at room temperature and an active negative resistance region. The origin of this unique behavior was identified through thermoelectric measurements and ab initio calculations to be a hybridization effect between graphene and the molecular layer. The enhancement of device parameters through morphology optimization highlights the potential of our approach toward new functionalities that advance the landscape of future electronics. [ABSTRACT FROM AUTHOR]

The charge properties and regularities of mutual influence of the electro-physical parameters in a metal (M)/insulator (I)/two-dimensional crystal heterostructure were studied. In one case, the transition metal dichalcogenide (TMD) MoS2 was considered as a two-dimensional crystal, and in another the Weyl semi-metal (WSM) ZrTe5, representative of a quasi-two-dimensional crystal was chosen for this purpose. By self-consistently solving the electrostatic equations of the heterostructures under consideration and the Fermi–Dirac distribution, the relationship between such parameters as the concentration of charge carriers, chemical potential, and quantum capacitance of the TMD (WSM), as well as the capacitance of the I layer and the interface capacitance I–TMD (WSM), and their dependence on the field electrode potential, have been derived. The conditions for the emergence of charge instability and the critical phenomena caused by it are also determined. [ABSTRACT FROM AUTHOR]

[Display omitted] Utilizing diverse material combinations in heterogeneous structures has become an effective approach for regulating interface characteristics and electronic structures. The g-C 3 N 4 /Co 3 O 4 heterostructures were fabricated by uniformly modifying Co 3 O 4 nanoparticles onto discrete clusters of g-C 3 N 4 nanosheets. Then, they were subsequently employed as positive electrode materials for assembling hybrid supercapacitors. According to the first-principles calculation, Co 3 O 4 and g-C 3 N 4 formed Co-N ionic bonds, establishing interfacial space symmetry-broken heterojunction and direct exchange and superexchange between ions at the interface and sub-interface. This resulted in a high-density spin–orbit hybrid heterogeneous polarization interface, significantly improving the quantum capacitance of heterojunction materials. Experimental results showed that the heterojunction had a specific capacitance of 2662 F g−1 at 1 A g−1. When the power density was 750 W kg−1, the energy density reached 128 Wh kg−1. Even when the power density was 16850 W kg−1, it could show an energy density of 62.5 Wh kg−1. The g-C 3 N 4 /Co 3 O 4 heterojunction could realize high energy density charge storage as the cathode material of supercapacitors. The construction of heterogeneous polarization interfaces for high-energy quantum capacitors provides a new and effective method for the energy storage field. [ABSTRACT FROM AUTHOR]

Double traditional metal (TM) Janus MXenes have more superior properties when compared with MXenes. The electronic and optical properties, Bader charge and quantum capacitance of ZrMCO 2 (M = Sc, Ti, V, Cr, Mn, Fe, Y, Zr, Nb, Mo, Hf, Ta, W) are explored by density functional theory (DFT). The stability of these systems is confirmed by cohesive energy. The substitution of Ti/Hf atoms results in the decrease of bandgap of ZrTiCO 2 /ZrHfCO 2 , which is induced by the redshift of conduction band minimum (CBM). ZrMCO 2 (M = Cr, Mn) are magnetic semiconductors and ZrMCO 2 (M = Sc, V, Y, Fe) are magnetic metals. All doping atoms except Hf improve the maximum quantum capacitance of ZrMCO 2 at positive bias. Wide voltage makes ZrMCO 2 (M = Nb, Ta, W) change into anode material and ZrFeCO 2 into cathode material. ZrMCO 2 (M = Sc, Mn, Y, Hf, Zr) and ZrMCO 2 (M = V, Cr) can serve as cathode and anode materials in whole voltage, respectively. Much charge accumulating between Fe and C atoms results in the smallest Fe–C bond among all M − C bonds, which indicates the strongest interaction between Fe and C atoms. Optical properties and work function are further explored. [ABSTRACT FROM AUTHOR]

Despite supercapacitors' high-power density and rapid charge transfer, limitations in energy density and stability drive research into cost-effective, efficient electrode materials. Emerging two-dimensional materials, especially transition metal sulfides, are of significant interest due to their tunable properties. Strategies such as phase engineering, defect creation, heterostructure formation, and advanced synthesis methods refine the electrochemical properties. In this study, different phases of tin sulfide, including α-SnS, π-SnS, and β-SnS, were effectively synthesized through hydrothermal and wet chemical methodologies. Following comprehensive characterization, electrochemical analysis offered valuable insights into the electrochemical behavior of each phase, notably showcasing superior performance in β-SnS to α-SnS and π-SnS. To further augment the electrochemical capabilities of β-SnS, a heterostructure was synthesized incorporating Ti3C2Tx MXene. The heterostructure displayed an exceptional capacitance of 615 mF/cm2 at a flow rate of 4 mA/cm2. This heterostructure was then employed in fabricating an asymmetric supercapacitor (β-SnS/Ti3C2Tx//Ti3C2Tx) operated at 1.5 V, displaying a high areal capacitance of 109 mF/cm2 along with the energy density and power density of 34.06 μWh/cm2 and 6.28 mW/cm2, respectively. With amazing cycling stability, the electrochemical performance and structural properties were corroborated through density functional theoretical simulations. [ABSTRACT FROM AUTHOR]

Increasing energy storage demands, and the reducing device size have led to the development of high surface area nanoporous materials. However, the energy storage in such materials do not typically scale as expected according to the increase in the surface area. This is because of another capacitance that appears in series with the electric double-layer capacitors used for energy storage. This capacitance is termed quantum capacitance, which is although present in all materials but becomes considerable in value for materials with low density of electronic states. The quantum capacitance and its effects can greatly enhance our understanding of the double-layer capacitance. In this review, we present the understanding built behind quantum capacitance based on some of the some recent work elucidating the vastness of the area that can be explored.

In this paper, we examine the response of charge carriers in a dual-gate graphene field-effect transistor (GFET). We have conducted an investigation into the input-output properties of both monolayer and bilayer graphene channels. Additionally, we demonstrated the relationship between surface potential and quantum capacitance using equivalent circuit modelling. We offer precise mathematical equations that define the border points separating distinct regions. These equations guarantee the continuity of the Jacobian matrix, which is crucial for the successful implementation of a circuit simulator. We can classify the current-voltage (I-V) characteristics of bilayer graphene into three distinct regions: triode, unipolar, and ambipolar. The equivalent circuit modelling findings indicated that GFETs had superior output characteristics and transconductance behavior compared to FETs. We observed a direct correlation between transconductance and gate voltage across various drain-to-source voltages.Nevertheless, with a higher gate voltage, there was a corresponding drop in the transconductance value. The threshold voltage for this dual-gate GFET is dependent on the back gate voltage. The GFET's threshold value decreased as the back gate voltage increased.

MXenes have superior catalytic activities, because of their excellent electronic properties. In this work, the electronic properties, quantum capacitance, and photocatalytic activity of Pt-doped Zr2CO2 (Pt-VO-Zr2CO2) nanosheets under biaxial strain are investigated by first-principles calculations. Pt-VO-Zr2CO2 are all indirect semiconductors under compressive strain and are direct semiconductors under tensile strain except at 10%. The red shift of Zr-d and O-p orbitals in conduction bands results in the decrease of band gaps under compressive strain. Pt-VO-Zr2CO2 under strain except at −8% are cathode materials in an aqueous system, especially for Pt-VO-Zr2CO2 with +10% strain with the maximum storage charge. Pt-VO-Zr2CO2 under strain can reduce water at pH 0 and perform overall water splitting in a neutral environment. Pt-VO-Zr2CO2 nanosheets with a strain larger than +4% can reduce CO2 to all products, and tensile strain enhances CO2 photocatalysis. The N2 reduction capability of Pt-VO-Zr2CO2 reduces in a neutral environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Enabling fabrication and exposure of merely graphene edges. • Utilizing quantum capacitance proportional to the density of states at edges. • Singular electrical field gradients at edges for trapping biomolecules. • Detecting biomolecules at 10 ag/mL concentrations within several minutes. Graphene, with its outstanding electrical properties, has appealed to the attention of researchers all over the world for biosensing applications. So far, much of the research has been conducted on the field-effect modulations of carriers in the basal plane of graphene after adsorbing charged biomolecules. However, another essential aspect--the graphene edge--has been largely ignored due to the difficulties in both manufacture and characterization. Here, we propose a facile intercalation and pressure sintering approach that enables the fabrication and exposure of only graphene edges. The quantum capacitance of the exposed edges is proportional to the local density of state (DOS) and can be harvested for biochemical sensing. Notably, due to fringe electric field enhancement and biomolecular convergence at the one-dimensional graphene edges, we are able to detect four representative amino acids at 0.01 fg/mL concentrations within several minutes. These achievements in innovative quantum capacitance measurements of graphene edges, combined with simple and robust device fabrication by eliminating complex micro-nano processing, offer a new avenue for the next generation of biochemical sensors with ever-demanding sensitivities. [ABSTRACT FROM AUTHOR]

MXenes for supercapacitor (SC) electrodes is a very promising area of research. Supercapacitors are still behind batteries when to be used as primary energy source due to their low energy densities. Hence, additional research is vital to explore materials like MXenes for SC electrodes. The electronic properties of molybdenum nitride Mo2N are studied and its quantum capacitance (QC) is calculated to explore its potential for SC electrodes. The MXene is found to be metallic in nature. The QC values for Mo2N MXene are extremely high around Fermi level. Maximum value of 746.69 µF cm−2 is achieved which is way higher than that of graphene. The value remains high for the negative bias voltage as well. [ABSTRACT FROM AUTHOR]

Functionalization of widely used graphene oxide (GO) can be beneficial not only in tuning its characteristics along with preventing the restacking of its layers and improving wettability but also in providing pseudocapacitance as a supercapacitor electrode. In this research, for the first time, the electrochemical performance of guanidine-functionalized graphene oxide (G-GO) examined by means of both computational and experimental methods. As a high-performance supercapacitor electrode, G-GO illustrates a high specific capacitance of 612F/g at the current density of 1.5 A/g together with extraordinary cyclic stability for 12,000 cycles at high current density of 10 A/g. Moreover, quantum capacitance together with the layer distance change during functionalization reaction, calculated via density functional theory (DFT), also exhibit the superior performance of G-GO.

Density functional theory (DFT) computation has been utilized to explore the effects of the transition metal oxides: CoO, CuO, NiO, and ZnO doping on the electronic properties, structural, and quantum capacitances of graphene oxide nanosheet. From the magnetic moment analysis CoO@GO was observed to have higher magnetic moment of 11.688 μB compared to the studied the transition metal oxide doped systems. Investigation into the electronic properties revealed that NiO@GO attained higher energy gap with value of 0.144 eV. It was observed that the GO O/C affects the bandgaps of the modelled systems. Perturbation theory analysis of fock matrix showed that CoO@GO and CuO@GO possessed higher second order stabilization energy with values 238.56 kcal/mol and 208.94 kcal/mol respectively. From the quantum capacitance studies, it was observed that the value of CQ for graphene oxide (GO) increased slightly from 72.276 µF/cm2 to ZnO@GO (121.550 µF/cm2) > NiO@GO (93.870 µF/cm2) > CoO@GO (90.52 µF/cm2) > CuO@GO (89.375 µF/cm2). The results obtained herein can provide an effective and simple new idea for the design of graphene-based supercapacitors that possess high energy density.

In semiconductor spin quantum bits (qubits), the radio-frequency (RF) gate-based readout is a promising solution for future large-scale integration, as it allows for a fast, frequency-multiplexed readout architecture, enabling multiple qubits to be read out simultaneously. This article introduces a theoretical framework to evaluate the effect of various parameters, such as the readout probe power, readout chain's noise performance, and integration time on the intrinsic readout signal-to-noise ratio, and thus readout fidelity of RF gate-based readout systems. By analyzing the underlying physics of spin qubits during readout, this work proposes a qubit readout model that takes into account the qubit's quantum mechanical properties, providing a way to evaluate the tradeoffs among the aforementioned parameters. The validity of the proposed model is evaluated by comparing the simulation and experimental results. The proposed analytical approach, the developed model, and the experimental results enable designers to optimize the entire readout chain effectively, thus leading to a faster, lower power readout system with integrated cryogenic electronics.

Graphene-based frameworks suffer from a low quantum capacitance due to graphene’s Dirac point at the Fermi level. This theoretical study investigated the effect structural defects, nitrogen and boron doping, and surface epoxy/hydroxy groups have on the electronic structure and capacitance of graphene. Density functional theory calculations reveal that the lowest energy configurations for nitrogen or boron substitutional doping occur when the dopant atoms are segregated. This elucidates why the magnetic transition for nitrogen doping is experimentally only observed at higher doping levels. We also highlight that the lowest energy configuration for a single vacancy defect is magnetic. Joint density functional theory calculations show that the fixed band approximation becomes increasingly inaccurate for electrolytes with lower dielectric constants. The introduction of structural defects rather than nitrogen or boron substitutional doping, or the introduction of adatoms leads to the largest increase in density of states and capacitance around graphene’s Dirac point. However, the presence of adatoms or substitutional doping leads to a larger shift of the potential of zero charge away from graphene’s Dirac point.

Density functional calculations were performed on 15 functionalized graphene models to investigate the enhancement of quantum capacitance (CQ) by common dopant elements N, P, S, and O from biomaterials. Geometry optimizations and formation energy calculations demonstrated that the van der Waals radius and additional covalent bonds influenced the mechanical stress and formation energy, particularly due to the distortion of the graphene lattice caused by larger S or P atoms replacing carbon atoms. According to both the CQ and formation energy calculations, nitrogen emerged as the most promising doping element for enhancing CQ, followed by phosphorus, while sulfur showed a relatively lower contribution. Electron density profiles indicated that the improvement of CQ was facilitated by the lone pair electrons at the defects. The effects of dopants on electronic structures were further elucidated through CQ characteristics, resulting in the classification of functionalized graphene models into three types. The ‘graphitic’ type represented configurations that preserved most of the electronic structure of pristine graphene, while ‘p-type’ and ‘n-type’ represented those experienced the loss and gain of valence electrons, respectively. This electronic structure-based classification of doping provides valuable insights for future designs, enabling control over sintering and doping conditions in biomass-derived electrode materials for supercapacitors.

MXenes have wide applications because of the structural flexibility and compositional diversity. Quantum capacitance, electronic and photocatalytic properties of Sc2CO2 monolayer under uniaxial strains are investigated by first‐principles calculation. Sc2CO2 monolayer can withstand stress up to 13.96 N/M and about 14% tensile uniaxial strain limit. Sc2CO2 undergoes a transition from semiconductor to metal at −15% uniaxial strain. Sc2CO2 under uniaxial strains are only used for the water reduction at pH = 0. Sc2CO2 under uniaxial strains of −10%, −7%, −3%, 0%, and 4% within the appropriate pH scope are potential photocatalysts for water redox reaction. Sc2CO2 with −15% uniaxial strain is promising anode material, and Sc2CO2 with tensile uniaxial strain is more potential cathode material. Wide voltage improves the top quantum capacitance at negative bias under uniaxial strain and keeps the type of electrode materials. Quantum capacitance of Sc2C with mixed termination (Sc2CO0.59F1.19(OH)0.22) under uniaxial strain is explored. The introduction of uniaxial strain and mixed termination has little effect on the electrode type of Sc2CO2 MXene. [ABSTRACT FROM AUTHOR]

MXenes are promising electrode materials due to their excellent performance. However, the quantum capacitance (Cdiff) and surface storage charge (Q) of bare M2C are little reported theoretically up to now. Herein, Cdiff and Q of 12 M2C MXenes related with 3d, 4d, and 5d transition metal (TM) atoms are investigated in aqueous and ionic/organic systems. All M2C MXenes are metallic. M2C with 5d TM are cathode materials. M2C with 4d TM are also cathode materials except Y2C MXene. For M2C with 3d TM, Sc2C and Mn2C are cathode materials, while Ti2C, V2C, and Cr2C are anode materials, especially for Ti2C and V2C with larger |Qp|/|Qn| and Qp. The broadened voltage maintains the type of electrode materials. W2C is the least promising cathode material in broad voltage. [ABSTRACT FROM AUTHOR]

MXene is widely used as electrode material because of its excellent performance. A new branch, i‐MXene is recently synthesized and confirmed to have superior performance. Density functional theory is used to investigate the structural and electronic properties, magnetic anisotropy and quantum capacitance of Cr2/3Sc1/3CO2 i‐MXene. The results indicate that the three models are stable and have magnetism, which originates from Cr‐d states. Cr2/3Sc1/3CO2 has higher work function and can be used as hole injection electrode. Model 2 prefers in‐plane as the magnetic easy direction, while the magnetic easy‐axis of model 3 is out‐of‐plane. The three models of Cr2/3Sc1/3CO2 are all suitable for anode material in whole voltage. Quantum capacitance, surface storage charges and electrode types at 233, 300, and 353 K are also investigated. [ABSTRACT FROM AUTHOR]

Using the intercalation technology, a biintercalated clathrate InSe <2 >+3>> was formed in which the guest components are placed in separate layers and alternately stage-ordered. Confirmation of this was obtained based on analysis of X-ray diffraction spectra for the initial single crystal and the single crystal intercalated with a ferroelectric and biintercalant. Due to weak interactions between the semiconductor matrix and guest components, periodic potential barriers of different natures (ferroelectric and ferromagnetic) were formed. This allowed observing such phenomena as quantum capacitance and negative capacitance. By the formation of magnetically active nano-centers through which it was possible to achieve the conditions of resonance tunneling, which as a consequence leads to the creation of EMF under normal conditions and under the influence of a constant magnetic field. This biintercalant clathrate acquires practical appeal for the manufacture of high-Q radio-frequency capacitors in terms of anomalous increase in dielectric constant in the megahertz range (εmax ≈ 5.5·104), simultaneously accepting the value of the dielectric loss tangent less than 1. At the same time, it also shows a negative magneto-capacitive effect was also obtained, which can be used for the construction of highly sensitive magnetic field sensors of capacitive type. Due to the ferroelectric guest component, this clathrate exhibits charge storage properties that can be used to create non-volatile memory so-called memristors. [ABSTRACT FROM AUTHOR]

MXenes have the excellent electrochemical properties as electrode of supercapacitors. Using density functional theory, we investigated the electronic properties and quantum capacitance of Zr2CO2 with atomic swap. The atomic swap results in the appearance of Frenkel‐type defect and Schottky defect. The negative binding energy confirms the stability of the studied systems. The atomic swap makes ZrC1, ZrC2, ZrO1, ZrO2, CO2 systems maintain the indirect semiconductor character, and CO2 system has the direct semiconductor character. The thermionic emission performance of Zr2CO2 MXene is greatly improved by atomic swap. ZrO1 and ZrO2 systems in aqueous system are appropriate anode materials. The wide voltage has little effect on the electrode type for perfect Zr2CO2, ZrO1, ZrO2, CO1, and CO2 systems, but changes ZrC1 and ZrC2 systems from cathode material in aqueous system to anode material in ionic/organic system. The work function and effective mass are also explored. [ABSTRACT FROM AUTHOR]

In recent years, supercapacitors have been widely used in the fields of energy, transportation, and industry. Among them, electrical double-layer capacitors (EDLCs) have attracted attention because of their dramatically high power density. With the rapid development of computational methods, theoretical studies on the physical and chemical properties of electrode materials have provided important support for the preparation of EDLCs with higher performance. Besides the widely studied double-layer capacitance (CD), quantum capacitance (CQ), which has long been ignored, is another important factor to improve the total capacitance (CT) of an electrode. In this paper, we survey the recent theoretical progress on the CQ of two-dimensional (2D) electrode materials in EDLCs and classify the electrode materials mainly into graphene-like 2D main group elements and compounds, transition metal carbides/nitrides (MXenes), and transition metal dichalcogenides (TMDs). In addition, we summarize the influence of different modification routes (including doping, metal-adsorption, vacancy, and surface functionalization) on the CQ characteristics in the voltage range of ±0.6 V. Finally, we discuss the current difficulties in the theoretical study of supercapacitor electrode materials and provide our outlook on the future development of EDLCs in the field of energy storage. [ABSTRACT FROM AUTHOR]

This study examined how gate dielectric materials affect drain current and quantum capacitance in wrap-around CNTFET devices. We examined CNTFET dielectric materials using Nanohub's FET toy simulator using the NEGF (non-equilibrium Green's function) model. We found that gate-dielectric choice affects the drain current and larger k values produced higher currents despite the same gate and drain voltages. However, the nano-metric device size limits electrons, causing drain current saturation early. Thus, dielectric and operational bias selection must be optimized. For high-k dielectrics, quantum capacitance dropped quickly after peaking. This can be explained by the fact that nano-sized materials have a lower density of energy states. [ABSTRACT FROM AUTHOR]

This paper presents an improved multi-level simulation framework for 2D material-based nanoelectronics, which expands from device simulation, physics-based compact modeling, and circuit benchmarking, using the germanane (GeH) metal-oxide-semiconductor field-effect transistors (MOSFETs) as an example. The device simulation employs the non-equilibrium Green's function method to obtain the characteristics of 2D GeH MOSFETs for both n-type MOSFETs and p-type MOSFETs. A compact model based on the MIT virtual source model is then revised to capture the unique behaviors of 2D-material-based MOSFETs, including voltage dependency of virtual source velocity and drain-induced barrier lowering, as well as the effect of quantum capacitance. HSPICE circuit simulations are performed to analyze and optimize CMOS digital benchmark circuits. The case study demonstrates that 2D material-based transistors favor a different range of supply voltage and threshold voltage than their silicon counterpart, to achieve the optimal energy-delay product. The impact of contact resistance is also analyzed using the proposed framework. This study offers a seamless multi-level simulation approach to bridge the gap between nanoelectronics and circuit behavior, thereby advancing the understanding of materials, devices, and circuits comprehensively. The framework tailored for GeH MOSFETs provides accurate device-circuit co-optimization which can be easily extended to devices based on other 2D materials. [ABSTRACT FROM AUTHOR]