Showing papers on "Capacitance published in 2009"
TL;DR: In this paper, a supercapacitor with a maximum specific capacitance of 205 F/g with a measured power density of 10 kW/kg at energy density of 28.5 Wh/kg in an aqueous electrolyte solution has been obtained.
Abstract: Graphene materials (GMs) as supercapacitor electrode materials have been investigated. GMs are prepared from graphene oxide sheets, and subsequently suffer a gas-based hydrazine reduction to restore the conducting carbon network. A maximum specific capacitance of 205 F/g with a measured power density of 10 kW/kg at energy density of 28.5 Wh/kg in an aqueous electrolyte solution has been obtained. Meanwhile, the supercapacitor devices exhibit excellent long cycle life along with ∼90% specific capacitance retained after 1200 cycle tests. These remarkable results demonstrate the exciting commercial potential for high performance, environmentally friendly and low-cost electrical energy storage devices based on this new 2D graphene material.
2,308 citations
TL;DR: The results strongly indicate that the long-standing puzzle about the interfacial capacitance in carbon-based electrodes has a quantum origin, and suggest that charged impurities also influences the quantum capacitance.
Abstract: Graphene has received widespread attention due to its unique electronic properties. Much of the research conducted so far has focused on electron mobility, which is determined by scattering from charged impurities and other inhomogeneities. However, another important quantity, the quantum capacitance, has been largely overlooked. Here, we report a direct measurement of the quantum capacitance of graphene as a function of gate potential using a three-electrode electrochemical configuration. The quantum capacitance has a non-zero minimum at the Dirac point and a linear increase on both sides of the minimum with relatively small slopes. Our findings -- which are not predicted by theory for ideal graphene -- suggest that charged impurities also influences the quantum capacitance. We also measured the capacitance in aqueous solutions at different ionic concentrations, and our results strongly indicate that the long-standing puzzle about the interfacial capacitance in carbon-based electrodes has a quantum origin.
1,492 citations
TL;DR: In this paper, the performance of MnO2 nanorods prepared by a precipitation reaction was investigated in 0.5 mol/L Li2SO4, Na2SO 4, and KSO4 aqueous electrolyte solutions.
Abstract: The electrochemical performance of MnO2 nanorods prepared by a precipitation reaction was investigated in 0.5 mol/L Li2SO4, Na2SO4, and K2SO4 aqueous electrolyte solutions. Results show that at the slow scan rates, the nanorods show the largest capacitance (201 F/g) in Li2SO4 electrolyte since the reversible intercalation/deintercalation of Li+ in the solid phase produces an additional capacitance besides the capacitance based on the absorption/desorption reaction. At fast scan rates they show the largest capacitance in the K2SO4 electrolyte due to the smallest hydration radius of K+, highest ionic conductivity, and lowest equivalent series resistance (ESR). An asymmetric activated carbon (AC)/K2SO4/MnO2 supercapacitor could be cycled reversibly between 0 and 1.8 V with an energy density of 17 Wh/kg at 2 kW/kg, much higher than those of the AC/K2SO4/AC supercapacitor and AC/Li2SO4/LiMn2O4 hybrid supercapacitor. Moreover, this supercapacitor exhibits excellent cycling behavior with no more than 6% capacita...
637 citations
TL;DR: In this paper, self-assembled monolayers and multilayers (SAMs) of organic molecules have been used to achieve low gate leakage currents and good chemical/thermal stability.
Abstract: Principal goals in organic thin-film transistor (OTFT) gate dielectric research include achieving: (i) low gate leakage currents and good chemical/thermal stability, (ii) minimized interface trap state densities to maximize charge transport efficiency, (iii) compatibility with both p- and n- channel organic semiconductors, (iv) enhanced capacitance to lower OTFT operating voltages, and (v) efficient fabrication via solution-phase processing methods. In this Review, we focus on a prominent class of alternative gate dielectric materials: self-assembled monolayers (SAMs) and multilayers (SAMTs) of organic molecules having good insulating properties and large capacitance values, requisite properties for addressing these challenges. We first describe the formation and properties of SAMs on various surfaces (metals and oxides), followed by a discussion of fundamental factors governing charge transport through SAMs. The last section focuses on the roles that SAMs and SAMTs play in OTFTs, such as surface treatments, gate dielectrics, and finally as the semiconductor layer in ultra-thin OTFTs.
595 citations
TL;DR: In this paper, an electric double layer transistor (EDLT) was found to exhibit very high transconductance and an ultrahigh carrier density in a fast, reversible, and reproducible manner.
Abstract: Very recently, electric-field-induced superconductivity in an insulator was realized by tuning charge carrier to a high density level (1 × 1014 cm−2). To increase the maximum attainable carrier density for electrostatic tuning of electronic states in semiconductor field-effect transistors is a hot issue but a big challenge. Here, ultrahigh density carrier accumulation is reported, in particular at low temperature, in a ZnO field-effect transistor gated by electric double layers of ionic liquid (IL). This transistor, called an electric double layer transistor (EDLT), is found to exhibit very high transconductance and an ultrahigh carrier density in a fast, reversible, and reproducible manner. The room temperature capacitance of EDLTs is found to be as large as 34 µF cm−2, deduced from Hall-effect measurements, and is mainly responsible for the carrier density modulation in a very wide range. Importantly, the IL dielectric, with a supercooling property, is found to have charge-accumulation capability even at low temperatures, reaching an ultrahigh carrier density of 8×1014 cm−2 at 220 K and maintaining a density of 5.5×1014 cm−2 at 1.8 K. This high carrier density of EDLTs is of great importance not only in practical device applications but also in fundamental research; for example, in the search for novel electronic phenomena, such as superconductivity, in oxide systems.
543 citations
TL;DR: In this paper, the authors synthesize interpenetrating carbon nanotubes and vanadium pentoxide (V 2 O 5 ) nanowires networks via a simple in situ hydrothermal process.
Abstract: Nanocomposites of interpenetrating carbon nanotubes and vanadium pentoxide (V 2 O 5 ) nanowires networks are synthesized via a simple in situ hydrothermal process. These fibrous nanocomposites are hierarchically porous with high surface area and good electric conductivity, which makes them excellent material candidates for supercapacitors with high energy density and power density. Nanocomposites with a capacitance up to 440 and 200 F g -1 are achieved at current densities of 0.25 and 10 A g -1 , respectively. Asymmetric devices based on these nanocomposites and aqueous electrolyte exhibit an excellent charge/discharge capability, and high energy densities of 16 W h kg -1 at a power density of 75 W kg -1 and 5.5 W h kg -1 at a high power density of 3750 W kg -1 . This performance is a significant improvement over current electrochemical capacitors and is highly competetive with Ni-MH batteries. This work provides a new platform for high-density electrical-energy storage for electric vehicles and other applications.
431 citations
TL;DR: In this paper, two methods of reducing the storage capacitance in the ac/dc power supplies for light emitting diode (LED) lighting were proposed to achieve a long power suppliespsila lifetime.
Abstract: This paper proposes two methods of reducing the storage capacitance in the ac/dc power supplies for light emitting diode (LED) lighting. In doing so, film capacitors can be adopted instead of electrolytic capacitors to achieve a long power suppliespsila lifetime. The voltage ripple of the storage capacitor is intentionally increased to reduce the storage capacitance. The method of determining the storage capacitance for ensuring that the boost power factor correction converter operates normally in the whole input voltage range is also discussed. For the purpose of further reducing the storage capacitance, a method of injecting the third harmonic current into the input current flow is proposed. While ensuring that the input power factor is always higher than 0.9 to comply with regulation standards such as ENERGY STAR, the storage capacitance can be reduced to 65.6% of that with an input power factor of 1. A 60-W experimental prototype is built to verify the proposed methods.
380 citations
TL;DR: The use of atomic layer deposition is reported to be used to fabricate arrays of metal-insulator-metal nanocapacitors in anodic aluminium oxide nanopores that have a capacitance per unit planar area significantly exceeding previously reported values.
Abstract: Nanostructured devices have the potential to serve as the basis for next-generation energy systems that make use of densely packed interfaces and thin films 1 . One approach to making such devices is to build multilayer structures of large area inside the open volume of a nanostructured template. Here, we report the use of atomic layer deposition to fabricate arrays of metal–insulator–metal nanocapacitors in anodic aluminium oxide nanopores. These highly regular arrays have a capacitance per unit planar area of 10 m Fc m 22 for 1-mm-thick anodic aluminium oxide and 100 m Fc m 22 for 10-mm-thick anodic aluminium oxide, significantly exceeding previously reported values for metal–insulator–metal capacitors in porous templates 2–6 . It should be possible to scale devices fabricated with this approach to make viable energy storage systems that provide both high energy density and high power density. The nanocapacitor structures in this Letter are formed of metal electrodes separated by a dielectric film; therefore they behave in the same manner as conventional electrostatic capacitors, in which charge is stored on opposing electrode surfaces. A characteristic feature of electrostatic capacitors is high power. This is because charge can be moved rapidly, with speeds limited only by external circuit RCs. However, energy storage is limited because only surface charge is used. In contrast, conventional electrochemical supercapacitors store charge in electric double layers or in faradic reactions, permitting larger energy density storage on the electrode surfaces. Power density is limited in these devices because of the requirement for mass transport of ions and/or redox reactions 7 . The use of highly regular nanostructures promises both high energy and high power density. For the nanocapacitors described in this Letter, the nanostructure significantly enhances capacitance density. The nanocapacitors demonstrate the high power (up to � 1 � 10 6 Wk g 21 ) typical of electrostatic capacitors while achieving the much higher energy density (� 0.7 Wh kg 21 ) characteristic of electrochemical supercapacitors. As a result, electrostatic nanocapacitors are attractive for high-burst-power applications requiring the energy density of supercapacitors. To obtain energy devices that achieve dense packing of active interfaces and thin films, nanoporous structures are required that have internal surfaces on which highly uniform films can be reproducibly formed. We make use of the self-assembly of regular nanopore arrays available from anodic aluminium oxide (AAO) formation together with multilayer atomic layer deposition (ALD) to form highly controlled, self-aligned nanocapacitors. ALD has become the leading process used to achieve such coatings, yielding a high degree of thickness control and conformality in the most demanding nanostructures, with features that are either highly ordered 8–10 or are random porous networks 11–13 . Nanostructures fabricated with AAO and ALD show a high degree of uniformity across massive arrays, imparting the regularity that is a key factor in the viability of any technology 8 . Our fabrication strategy makes use of AAO nanopore templates in combination with metal–insulator–metal (MIM) structures deposited in the nanopores by ALD. The anodization process produces an ultrahigh density (� 1 � 10 10 cm 22 ) of hexagonally arranged, uniform, self-assembled nanopores in AAO film on Al tens of micrometres deep, which provides a good template for
365 citations
TL;DR: In this article, a comprehensive characterization of electrolyte-gated polymer thin-film transistors (TFTs) incorporating solution processable polymer semiconductors and high capacitance gate dielectrics is presented.
Abstract: We report comprehensive characterization of electrolyte-gated polymer thin-film transistors (TFTs) incorporating solution processable polymer semiconductors and high capacitance “ion gel” gate dielectrics. The ion gel dielectrics comprise self-assembled networks of triblock copolymers such as poly(styrene-b-methylmethacrylate-b-styrene) [PS-PMMA-PS] that are swollen with ionic liquids, e.g., (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]). The capacitance of the gels is exceptionally large (>10 μF/cm2 at 10 Hz), which is derived from the high concentration of mobile ions and facilitates operation of ion gel-gated organic TFTs (GEL-OTFTs) at very low voltages (< 2.5 V). Gate-induced hole densities in GEL-OTFTs employing different polythiophene semiconductors in the channel are on the order of 1014 carriers/cm2, with associated saturation hole mobilities that are also remarkably large, ∼1 cm2/(V s), likely because of the large gate-induced carrier densities. Examination of the ...
321 citations
TL;DR: In this paper, an interesting effect of iodide ions has been observed for positive electrode operating in a narrow range of potential and giving extremely high capacitance values exceeding 1840 F/g.
250 citations
TL;DR: In this article, the effect of light-generated carriers and applied bias in the behavior of the solar cell under illumination is discussed, and different cell parameters, as series and parallel resistances, capacitance, diode factor, minority carrier lifetime, acceptor impurities density and depletion layer charge density have been obtained as a function of bias voltage for different light illumination intensities.
Abstract: Highly efficient silicon solar cells have been characterised by impedance spectroscopy and current–potential characteristic in the dark and with different illumination intensities. For each illumination the impedance behaviour has been analysed at different applied bias potentials, in the forward and reverse region, comparing the results with the current–potential characteristic. Different cell parameters, as series and parallel resistances, capacitance, diode factor, minority carrier lifetime, acceptor impurities density and depletion layer charge density have been obtained as a function of bias voltage for different light illumination intensities. The effect of light-generated carriers and applied bias in the behaviour of the solar cell under illumination is discussed.
TL;DR: In this paper, a cross-linked poly(4-vinylphenol) (PVP) was investigated as new gate dielectric materials for lowvoltage thin-film transistors.
Abstract: Cross-linked polymer films were investigated as new gate dielectric materials for low-voltage thin-film transistors. Poly(4-vinylphenol) (PVP) was cross-linked through esterification reactions with commercially available bifunctional anhydrides, acyl chlorides, and carboxylic acids. The polymer dielectric films were evaluated based on surface morphology, capacitance, leakage current, and their compatibility with organic semiconductors. Thin insulating PVP films cross-linked with dianhydrides yielded a capacitance as high as 400 nF/cm2 with leakage currents below 10−8 A/cm2. Organic thin-film transistors (OTFTs) fabricated on these gate dielectric layers exhibited charge carrier mobilities as high as 3 cm2/(V s) for p-channel pentacene on octadecyltriethoxylsilane (OTS)-modified PVP and 0.045 cm2/(V s) for n-channel perfluorinated copper phthalocyanine (FCuPc).
TL;DR: In this article, the self-discharge of an electrochemical capacitor is characterized by measuring the decline of open-circuit voltage of the electrochemical capacitance, and the mechanisms of selfdischarge, leakage current, and diffusion of ions at the electrode-electrolyte interfaces are modeled by an electrical equivalent circuit.
Abstract: The self-discharge of an electrochemical capacitor, also referred to as a supercapacitor, is an important factor in determining the duration of maintaining stored energy, especially in low-duty-cycle applications. The study of self-discharge is conducted as follows: first, the self-discharge is characterized by measuring the decline of open-circuit voltage of the electrochemical capacitor. Second, the mechanisms of self-discharge, leakage current, and diffusion of ions at the electrode-electrolyte interfaces are modeled by an electrical equivalent circuit. The equivalent circuit elements are experimentally determined according to the self-discharge time behavior. In addition, the dependence of the self-discharge parameters on both temperature and initial voltage across the electrochemical capacitor is described in detail.
TL;DR: It is shown that waveguide integrated germanium detectors with capacitance as small as 2.4 fF and directly recorded impulse response as fast as 8.8 ps can be used for wavelength division demultiplexing.
Abstract: We demonstrate waveguide integrated germanium detectors with capacitance as small as 2.4 fF and directly recorded impulse response as fast as 8.8 ps. Based on such detectors and cascaded silicon microring resonators we also demonstrate a highly scalable wavelength division demultiplexing system that can potentially provide tera-bit/s (Tbps) bandwidth over a small area.
TL;DR: In this article, the transient response of double-gate thin-body-silicon interband tunnel field-effect transistor (TFET) with its metal-oxide-semiconductor field effect transistor counterpart was compared.
Abstract: We compare the transient response of double-gate thin-body-silicon interband tunnel field-effect transistor (TFET) with its metal-oxide-semiconductor field-effect transistor counterpart. Due to the presence of source side tunneling barrier, the silicon TFETs exhibit enhanced Miller capacitance, resulting in large voltage overshoot/undershoot in its large-signal switching characteristics. This adversely impacts the performance of Si TFETs for digital logic applications. It is shown that TFETs based on lower bandgap and lower density of states materials like indium arsenide show significant improvement in switching behavior due to its lower capacitance and higher ON current at reduced voltages.
21 Mar 2009
TL;DR: In this article, the authors show that a combination of an ac link converter and a ripple power port leads to a dramatic increase in reliability, with expected mean-time-between-failure ratings on the order of 1.4 million hours -sufficient for hundred-year operation in long-life applications such as photovoltaic converters and LED lamps.
Abstract: Energy storage requirements for converters with a dc port and a single-phase grid-connected port are evaluated, based on the unavoidable double-frequency power requirement. The minimum energy storage requirement is linked to a minimum capacitance requirement for converters that use capacitance energy storage. It is shown how to employ a ripple power port to manage energy storage and decouple capacitor ripple from power ripple. A ripple power port allows a designer to make a choice of capacitor voltage independent of system voltages. This in turn allows film capacitors of modest size to be used for energy storage in these applications. A combination of ac link converter and ripple power port leads to a dramatic increase in reliability: it is shown that converters with nominal ratings up to 200 W can be designed with expected mean-time-between-failure ratings on the order of 1.4 million hours - sufficient for hundred-year operation in long-life applications such as photovoltaic converters and LED lamps. This large increase in life is achieved with minimal extra cost.
TL;DR: It is concluded that the pseudocapacitance through faradic charge transfer is the most important factor to enhance the capacitance by N- or B-doping.
Abstract: Anodic aluminum oxide (AAO) with uniform straight nanochannels was completely coated with pure, N-doped, or B-doped carbon layer. Their electric double layer capacitances are measured in aqueous (1 M sulfuric acid) and organic (1 M Et4NBF4/polypropylene carbonate) electrolyte solutions in order to investigate the capacitance enhancement mechanisms caused by N- or B-doping. Since the three types of carbon-coated AAOs (pure, N-doped, or B-doped) have exactly the same pore structure, the observed capacitance enhancement was ascribable to only the following factors: (i) better wettability, (ii) the decrease of equivalent series resistance, (iii) the contribution of space-charge-layer capacitance, and (iv) the occurrence of pseudocapacitance. From the measurements of the wettability and the electrical resistance of the coated AAOs together with the electrochemical investigation (the cyclic voltammetry, the galvanostatic charge/discharge cycling, and the impedance analysis), it is concluded that the pseudocapac...
TL;DR: In this article, molecular dynamics simulations of the electrical double layers (EDLs) at the interface of ionic liquids [BMIM][NO3] and planar electrodes are presented.
Abstract: We report on the molecular dynamics simulations of the electrical double layers (EDLs) at the interface of ionic liquids [BMIM][NO3] and planar electrodes. Simulations confirm that a Helmholtz-like interfacial counterion layer exists when the electrode charge density is negative or strongly positive, but the counterion layer is not well-defined when the electrode charge density is weakly positive. The thickness of the EDL, as inferred from how deep the charge separation and orientational ordering of the ions penetrate into the bulk ILs, is about 1.1 nm. The liquid nature of the IL and the short-range ion−electrode and ion−ion interactions are found to significantly affect the structure of the EDL, particularly at low electrode charge densities. Charge delocalization of the ions is found to affect the mean force experienced by the ions and, thus, can play an important role in shaping the EDL structure. The differential capacitance of the EDLs is found to be nearly constant under negative electrode polariza...
TL;DR: In this article, closed-form expressions of the resistance, capacitance, and inductance for interplane 3D vias are presented, which account for the 3D via length, diameter, dielectric thickness, and spacing to ground.
Abstract: Closed-form expressions of the resistance, capacitance, and inductance for interplane 3-D vias are presented in this paper. The closed-form expressions account for the 3-D via length, diameter, dielectric thickness, and spacing to ground. A 3-D numerical simulation is used to extract electromagnetic solutions of the resistance, capacitance, and inductance for comparison with the closed-form expressions, revealing good agreement between simulation and the physical models. The maximum error for the resistance, capacitance, and inductance is less than 8%.
TL;DR: This paper provides an estimate of the effective output capacitance and drive current and a three-point model is proposed to extract the effective drive current from the real-time switching current trajectory in a TFET inverter.
Abstract: Through mixed-mode device and circuit simulation, this paper provides an estimate of the effective output capacitance (C EFF) and drive current (I EFF) for delay (tauf = 0.69 R sw C EFF, where R sw = V DD/2 I EFF) estimation of unloaded tunnel field-effect transistor (TFET) inverters. It is shown that unlike MOSFET inverters, where C EFF is approximately equal to the gate capacitance (C gg) , in TFET inverters, the output capacitance can be as high as 2.6 times the gate capacitance. A three-point model is proposed to extract the effective drive current from the real-time switching current trajectory in a TFET inverter.
01 Jan 2009
TL;DR: In this article, the authors proposed a combination of an AC-connector and aripple powerport to increase the lifetime of a single-input single-output (SISO) converter with nominal ratings up to 200W.
Abstract: Energystorage requirements forconverters withadc portandasingle-phase grid-connected portareevaluated, based ontheunavoidable double-frequency powerrequirement. The minimumenergystorage requirement islinked toaminimum capacitance requirement forconverters thatusecapacitance energy storage. Itisshownhowtoemployaripple powerportto manageenergystorage anddecouple capacitor ripple from powerripple. A ripple powerportallows adesigner tomakea choice ofcapacitor voltage independent ofsystem voltages. This inturnallows filmcapacitors ofmodestsize tobeusedforenergy storage inthese applications. A combination ofaclinkconverter andripple powerportleads toadramatic increase inreliability: itisshownthatconverters withnominal ratings upto200W can bedesigned withexpected mean-time-between-failure ratings on theorderof1.4million hours- sufficient forhundred-year operation inlong-life applications suchasphotovoltaic converters andLED lamps.Thislargeincrease inlife isachieved with minimal extra cost.
TL;DR: In this paper, the capacitance-resistance model (CRM) is used to evaluate the performance of waterflood performance using only production/injection data to predict performance, which provides simplicity and speed of calculation.
Patent•
02 Mar 2009
TL;DR: In this paper, a method and apparatus for use in a digitally tuning a capacitor in an integrated circuit device is described, which facilitates digitally controlling capacitance applied between a first and second terminal.
Abstract: A method and apparatus for use in a digitally tuning a capacitor in an integrated circuit device is described. A Digitally Tuned Capacitor DTC is described which facilitates digitally controlling capacitance applied between a first and second terminal. In some embodiments, the first terminal comprises an RF+ terminal and the second terminal comprises an RF− terminal. In accordance with some embodiments, the DTCs comprise a plurality of sub-circuits ordered in significance from least significant bit (LSB) to most significant bit (MSB) sub-circuits, wherein the plurality of significant bit sub-circuits are coupled together in parallel, and wherein each sub-circuit has a first node coupled to the first RF terminal, and a second node coupled to the second RF terminal. The DTCs further include an input means for receiving a digital control word, wherein the digital control word comprises bits that are similarly ordered in significance from an LSB to an MSB.
TL;DR: In this letter, it is proposed that this IS measurement is effective for evaluating the electric properties of several layers with capacitance components in organic thin-film solar cells.
Abstract: An inverted-type organic bulk-heterojunction solar cell inserting zinc oxide (ZnO) as an electron collection electrode, fluorine-doped tin oxide (FTO)/ZnO/[6,6]-phenyl-C61-butyric acid methyl ester:regioregular poly(3-hexylthiophene) (PCBM:P3HT)/poly(3,4-ethylenedioxylenethiophene):poly(4-styrenesulfonic acid) (PEDOT:PSS)/Au, was fabricated in air and characterized by an alternating current impedance spectroscopy (IS). In the IS measurement, we observed reproducibly the electric resistance and capacitance components originating from ZnO and organic active layers, and we found that the depletion layer functioning to take out the photocurrent to the external circuit was formed in both the ZnO and PCBM:P3HT layers at the ZnO/PCBM:P3HT interface. In this letter, we propose that this IS measurement is effective for evaluating the electric properties of several layers with capacitance components in organic thin-film solar cells.
TL;DR: In this article, an energy distribution density-of-states DOS of defects in the effective band gap of organic bulk heterojunctions is determined by means of capacitance methods, which consists of calculating the junction capacitance derivative with respect to the angular frequency of the small voltage perturbation applied to thin film poly3hexylthiopheneP3HT6,6-phenyl C61-butyric acid methyl ester PCBM solar cells.
Abstract: Energy distributions density-of-states DOS of defects in the effective band gap of organic bulk heterojunctions are determined by means of capacitance methods. The technique consists of calculating the junction capacitance derivative with respect to the angular frequency of the small voltage perturbation applied to thin film poly3-hexylthiopheneP3HT6,6-phenyl C61-butyric acid methyl ester PCBM solar cells. The analysis, which was performed on blends of different composition, reveals the presence of defect bands exhibiting Gaussian shape located at E 0.38 eV above the highest occupied molecular orbital level of the P3HT. The disorder parameter , which accounts for the broadening of the Gaussian DOS, lies within the range of 49‐66 meV. The total density of defects results of order 10 16 cm 3 .© 2009 American Institute of Physics.
TL;DR: In this article, activated carbon binderless monoliths with high consistency and large porosity, synthesised from a mesophase pitch, are studied as electrodes for supercapacitors.
TL;DR: In this article, a simple approximate expression for the resonant frequency of a singly split single ring that is among the first microwave resonators designed to be small relative to the wavelength is derived.
Abstract: A simple approximate expression is derived for the resonant frequency of a singly split single ring that is among the first microwave resonators designed to be small relative to the wavelength. In addition to the usual gap capacitance the concept of surface capacitance is introduced. The surface capacitance is determined analytically by two different methods, first using analytical expressions for the electric field of a split cylinder, and second by using conformal mapping. Taking two practical examples the resonant frequency, found analytically, is shown to agree with that obtained by numerical simulations. The model could be used for studies of the resonant properties of split rings in the terahertz region.
TL;DR: In this article, a wide band gap semiconducting layer of n-type ZnO thin film was fabricated on a Si substrate with electrochemical deposition technique and the currentvoltage (I-V) and capacitance-voltage/frequency (C-V/f) characteristics of the structure have been measured at room temperature.
TL;DR: In this article, the performance of the supercapacitor coin cells, assembled with nanostructured activated carbon fabric (ACF) as the electrode material and 1.M tetraethylammonium tetrafluoroborate (TEABF 4 ) in polypropylene carbonate (PC) solution as the electrolyte, was systematically studied within the set temperature window.
TL;DR: In this article, the number of stacking layers of multilayer graphene sheets by selective post-treatments was determined according to specific surface area, which is attributed to the dependence of space charge layer capacitance on number of layers.