Low voltage driven RF MEMS capacitive switch using reinforcement for reduced buckling

NASA Astrophysics Data System (ADS)

Bansal, Deepak; Bajpai, Anuroop; Kumar, Prem; Kaur, Maninder; Kumar, Amit; Chandran, Achu; Rangra, Kamaljit

2017-02-01

Variation in actuation voltage for RF MEMS switches is observed as a result of stress-generated buckling of MEMS structures. Large voltage driven RF-MEMS switches are a major concern in space bound communication applications. In this paper, we propose a low voltage driven RF MEMS capacitive switch with the introduction of perforations and reinforcement. The performance of the fabricated switch is compared with conventional capacitive RF MEMS switches. The pull-in voltage of the switch is reduced from 70 V to 16.2 V and the magnitude of deformation is reduced from 8 µm to 1 µm. The design of the reinforcement frame enhances the structural stiffness by 46 % without affecting the high frequency response of the switch. The measured isolation and insertion loss of the reinforced switch is more than 20 dB and 0.4 dB over the X band range.

Series asymmetric supercapacitors based on free-standing inner-connection electrodes for high energy density and high output voltage

NASA Astrophysics Data System (ADS)

Tao, Jiayou; Liu, Nishuang; Rao, Jiangyu; Ding, Longwei; Al Bahrani, Majid Raissan; Li, Luying; Su, Jun; Gao, Yihua

2014-11-01

Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO2 nanowire/carbon nanotube (CNT) composites and MoO3 nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm-3 at a scan rate of 2 mV s-1 and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm-3 at a power density of 261.4 mW cm-3, and exhibits excellent cycling performance of 99.6% capacitance retention over 10 000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage.Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO2 nanowire/carbon nanotube (CNT) composites and MoO3 nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm-3 at a scan rate of 2 mV s-1 and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm-3 at a power density of 261.4 mW cm-3, and exhibits excellent cycling performance of 99.6% capacitance retention over 10 000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04819a

Differences between direct current and alternating current capacitance nonlinearities in high-k dielectrics and their relation to hopping conduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaldi, O.; Kassmi, M.; El Manar University, LMOP, 2092 Tunis

2014-08-28

Capacitance nonlinearities were studied in atomic layer deposited HfO{sub 2} films using two types of signals: a pure ac voltage of large magnitude (ac nonlinearities) and a small ac voltage superimposed to a large dc voltage (dc nonlinearities). In theory, ac and dc nonlinearities should be of the same order of magnitude. However, in practice, ac nonlinearities are found to be an order of magnitude higher than dc nonlinearities. Besides capacitance nonlinearities, hopping conduction is studied using low-frequency impedance measurements and is discussed through the correlated barrier hopping model. The link between hopping and nonlinearity is established. The ac nonlinearitiesmore » are ascribed to the polarization of isolated defect pairs, while dc nonlinearities are attributed to electrode polarization which originates from defect percolation paths. Both the ac and dc capacitance nonlinearities display an exponential variation with voltage, which results from field-induced lowering of the hopping barrier energy.« less

Design and analysis of optimised class E power amplifier using shunt capacitance in the output structure

NASA Astrophysics Data System (ADS)

Hayati, Mohsen; Roshani, Sobhan; Zirak, Ali Reza

2017-05-01

In this paper, a class E power amplifier (PA) with operating frequency of 1 MHz is presented. MOSFET non-linear drain-to-source parasitic capacitance, linear external capacitance at drain-to-source port and linear shunt capacitance in the output structure are considered in design theory. One degree of freedom is added to the design of class E PA, by assuming the shunt capacitance in the output structure in the analysis. With this added design degree of freedom it is possible to achieve desired values for several parameters, such as output voltage, load resistance and operating frequency, while both zero voltage and zero derivative switching (ZVS and ZDS) conditions are satisfied. In the conventional class E PA, high value of peak switch voltage results in limitations for the design of amplifier, while in the presented structure desired specifications could be achieved with the safe margin of peak switch voltage. The results show that higher operating frequency and output voltage can also be achieved, compared to the conventional structure. PSpice software is used in order to simulate the designed circuit. The presented class E PA is designed, fabricated and measured. The measured results are in good agreement with simulation and theory results.

Polymer/metal oxide hybrid dielectrics for low voltage field-effect transistors with solution-processed, high-mobility semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Held, Martin; Schießl, Stefan P.; Gannott, Florentina

Transistors for future flexible organic light-emitting diode (OLED) display backplanes should operate at low voltages and be able to sustain high currents over long times without degradation. Hence, high capacitance dielectrics with low surface trap densities are required that are compatible with solution-processable high-mobility semiconductors. Here, we combine poly(methyl methacrylate) (PMMA) and atomic layer deposition hafnium oxide (HfO{sub x}) into a bilayer hybrid dielectric for field-effect transistors with a donor-acceptor polymer (DPPT-TT) or single-walled carbon nanotubes (SWNTs) as the semiconductor and demonstrate substantially improved device performances for both. The ultra-thin PMMA layer ensures a low density of trap states atmore » the semiconductor-dielectric interface while the metal oxide layer provides high capacitance, low gate leakage and superior barrier properties. Transistors with these thin (≤70 nm), high capacitance (100–300 nF/cm{sup 2}) hybrid dielectrics enable low operating voltages (<5 V), balanced charge carrier mobilities and low threshold voltages. Moreover, the hybrid layers substantially improve the bias stress stability of the transistors compared to those with pure PMMA and HfO{sub x} dielectrics.« less

Measurement of n-type Dry Thermally Oxidized 6H-SiC Metal-oxide Semiconductor Diodes by Quasistatic and High-Frequency Capacitance Versus Voltage and Capacitance Transient Techniques

NASA Technical Reports Server (NTRS)

Neudeck, P.; Kang, S.; Petit, J.; Tabib-Azar, M.

1994-01-01

Dry-oxidized n-type 6H-SiC metal-oxide-semiconductor capacitors are investigated using quasistatic capacitance versus voltage (C-V), high-frequency C-V, and pulsed high-frequency capacitance transient (C-t) analysis over the temperature range from 297 to 573 K. The quasistatic C - V characteristics presented are the first reported for 6H-SiC MOS capacitors, and exhibit startling nonidealities due to nonequilibrium conditions that arise from the fact that the recombination/generation process in 6H-SiC is extraordinarily slow even at the highest measurement temperature employed. The high-frequency dark C-V characteristics all showed deep depletion with no observable hysteresis. The recovery of the high-frequency capacitance from deep depletion to inversion was used to characterize the minority-carrier generation process as a function of temperature. Zerbst analysis conducted on the resulting C-t transients, which were longer than 1000 s at 573 K, showed a generation lifetime thermal activation energy of 0.49 eV.

High temperature 1 MHz capacitance-voltage method for evaluation of border traps in 4H-SiC MOS system

NASA Astrophysics Data System (ADS)

Peng, Zhao-Yang; Wang, Sheng-Kai; Bai, Yun; Tang, Yi-Dan; Chen, Xi-Ming; Li, Cheng-Zhan; Liu, Ke-An; Liu, Xin-Yu

2018-04-01

In this work, border traps located in SiO2 at different depths in 4H-SiC MOS system are evaluated by a simple and effective method based on capacitance-voltage (C-V) measurements. This method estimates the border traps between two adjacent depths through C-V measurement at various frequencies at room and elevated temperatures. By comparison of these two C-V characteristics, the correlation between time constant of border traps and temperatures is obtained. Then the border trap density is determined by integration of capacitance difference against gate voltage at the regions where border traps dominate. The results reveal that border trap concentration a few nanometers away from the interface increases exponentially towards the interface, which is in good agreement with previous work. It has been proved that high temperature 1 MHz C-V method is effective for border trap evaluation.

High frequency capacitance-voltage characteristics of thermally grown SiO2 films on beta-SiC

NASA Technical Reports Server (NTRS)

Tang, S. M.; Berry, W. B.; Kwor, R.; Zeller, M. V.; Matus, L. G.

1990-01-01

Silicon dioxide films grown under dry and wet oxidation environment on beta-SiC films have been studied. The beta-SiC films had been heteroepitaxially grown on both on-axis and 2-deg off-axis (001) Si substrates. Capacitance-voltage and conductance-voltage characteristics of metal-oxide-semiconductor structures were measured in a frequency range of 10 kHz to 1 MHz. From these measurements, the interface trap density and the effective fixed oxide charge density were observed to be generally lower for off-axis samples.

Broadband linear high-voltage amplifier for radio frequency ion traps.

PubMed

Kuhlicke, Alexander; Palis, Klaus; Benson, Oliver

2014-11-01

We developed a linear high-voltage amplifier for small capacitive loads consisting of a high-voltage power supply and a transistor amplifier. With this cost-effective circuit including only standard parts sinusoidal signals with a few volts can be amplified to 1.7 kVpp over a usable frequency range at large-signal response spanning four orders of magnitude from 20 Hz to 100 kHz under a load of 10 pF. For smaller output voltages the maximum frequency shifts up to megahertz. We test different capacitive loads to probe the influence on the performance. The presented amplifier is sustained short-circuit proof on the output side, which is a significant advantage over other amplifier concepts. The amplifier can be used to drive radio frequency ion traps for single charged nano- and microparticles, which will be presented in brief.

Chloride and salicylate influence prestin-dependent specific membrane capacitance: support for the area motor model.

PubMed

Santos-Sacchi, Joseph; Song, Lei

2014-04-11

The outer hair cell is electromotile, its membrane motor identified as the protein SLC26a5 (prestin). An area motor model, based on two-state Boltzmann statistics, was developed about two decades ago and derives from the observation that outer hair cell surface area is voltage-dependent. Indeed, aside from the nonlinear capacitance imparted by the voltage sensor charge movement of prestin, linear capacitance (Clin) also displays voltage dependence as motors move between expanded and compact states. Naturally, motor surface area changes alter membrane capacitance. Unit linear motor capacitance fluctuation (δCsa) is on the order of 140 zeptofarads. A recent three-state model of prestin provides an alternative view, suggesting that voltage-dependent linear capacitance changes are not real but only apparent because the two component Boltzmann functions shift their midpoint voltages (Vh) in opposite directions during treatment with salicylate, a known competitor of required chloride binding. We show here using manipulations of nonlinear capacitance with both salicylate and chloride that an enhanced area motor model, including augmented δCsa by salicylate, can accurately account for our novel findings. We also show that although the three-state model implicitly avoids measuring voltage-dependent motor capacitance, it registers δCsa effects as a byproduct of its assessment of Clin, which increases during salicylate treatment as motors are locked in the expanded state. The area motor model, in contrast, captures the characteristics of the voltage dependence of δCsa, leading to a better understanding of prestin.

Linear electromagnetic excitation of an asymmetric low pressure capacitive discharge with unequal sheath widths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lieberman, M. A., E-mail: lieber@eecs.berkeley.edu; Lichtenberg, A. J.; Kawamura, E.

It is well-known that standing waves having radially center-high radio frequency (rf) voltage profiles exist in high frequency capacitive discharges. In this work, we determine the symmetric and antisymmetric radially propagating waves in a cylindrical capacitive discharge that is asymmetrically driven at the lower electrode by an rf voltage source. The discharge is modeled as a uniform bulk plasma which at lower frequencies has a thicker sheath at the smaller area powered electrode and a thinner sheath at the larger area grounded electrode. These are self-consistently determined at a specified density using the Child law to calculate sheath widths andmore » the electron power balance to calculate the rf voltage. The fields and the system resonant frequencies are determined. The center-to-edge voltage ratio on the powered electrode is calculated versus frequency, and central highs are found near the resonances. The results are compared with simulations in a similar geometry using a two-dimensional hybrid fluid-analytical code, giving mainly a reasonable agreement. The analytic model may be useful for finding good operating frequencies for a given discharge geometry and power.« less

A MEMS Interface IC With Low-Power and Wide-Range Frequency-to-Voltage Converter for Biomedical Applications.

PubMed

Arefin, Md Shamsul; Redouté, Jean-Michel; Yuce, Mehmet Rasit

2016-04-01

This paper presents an interface circuit for capacitive and inductive MEMS biosensors using an oscillator and a charge pump based frequency-to-voltage converter. Frequency modulation using a differential crossed coupled oscillator is adopted to sense capacitive and inductive changes. The frequency-to-voltage converter is designed with a negative feedback system and external controlling parameters to adjust the sensitivity, dynamic range, and nominal point for the measurement. The sensitivity of the frequency-to-voltage converter is from 13.28 to 35.96 mV/MHz depending on external voltage and charging current. The sensitivity ranges of the capacitive and inductive interface circuit are 17.08 to 54.4 mV/pF and 32.11 to 82.88 mV/mH, respectively. A capacitive MEMS based pH sensor is also connected with the interface circuit to measure the high acidic gastric acid throughout the digestive tract. The sensitivity for pH from 1 to 3 is 191.4 mV/pH with 550 μV(pp) noise. The readout circuit is designed and fabricated using the UMC 0.18 μm CMOS technology. It occupies an area of 0.18 mm (2) and consumes 11.8 mW.

Differential Depletion Capacitance Approximation Analysis Under DC Voltage for Air-Exposed Cu/n-Si Schottky Diodes

NASA Astrophysics Data System (ADS)

Korkut, A.

It is well known that the semiconductor surface is easily oxidized by air-media in time. This work studieds the characterization of Schottky diodes and changes in depletion capacitance, which is caused by air exposure of a group of Cu/n-Si/Al Schottky diodes. First, data for current-voltage and capacitance-voltage were a Ren, and then ideality factor, barrier height, built-in potential (Vbi), donor concentration and Fermi level, interfacial oxide thickness, interface state density were calculated. It is seen that depletion capacitance was calculate; whereafter built-in potential played an important role in Schottky diodes characteristic. Built-in potential directly affects the characteristic of Schottky diodes and a turning point occurs. In case of forward and reverse bias, depletion capacitance versus voltage graphics are matched, but in an opposite direction. In case of forward bias, differential depletion capacitance begins from minus values, it is raised to first Vbi, then reduced to second Vbi under the minus condition. And it sharply gones up to positive apex, then sharply falls down to near zero, but it takes positive values depending on DC voltage. In case of reverse bias, differential depletion capacitance takes to small positive values. In other respects, we see that depletion characteristics change considerably under DC voltage.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Astrophysics Data System (ADS)

Sarma, Garimella R.; Barranger, John P.

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solution shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects for environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and a typical application are included.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Astrophysics Data System (ADS)

Sarma, G. R.; Barranger, J. P.

1986-05-01

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solutions shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects the environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and typical application are included.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Technical Reports Server (NTRS)

Sarma, Garimella R.; Barranger, John P.

1986-01-01

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solution shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects for environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and a typical application are included.

Ramp-integration technique for capacitance-type blade-tip clearance measurement

NASA Technical Reports Server (NTRS)

Sarma, G. R.; Barranger, J. P.

1986-01-01

The analysis of a proposed new technique for capacitance type blade tip clearance measurement is presented. The capacitance between the blade tip and a mounted capacitance electrode within a guard ring forms one of the feedback elements of a high speed operational amplifier. The differential equation governing the operational amplifier circuit is formulated and solved for two types of inputs to the amplifier - a constant voltage and a ramp. The resultant solutions shows an output that contains a term that is proportional to the derivative of the product of the input voltage and the time constant of the feedback network. The blade tip clearance capacitance is obtained by subtracting the output of a balancing reference channel followed by integration. The proposed sampled data algorithm corrects the environmental effects and varying rotor speeds on-line, making the system suitable for turbine instrumentation. System requirements, block diagrams, and typical application are included.

Preamplifiers for non-contact capacitive biopotential measurements.

PubMed

Peng, GuoChen; Ignjatovic, Zeljko; Bocko, Mark F

2013-01-01

Non-contact biopotential sensing is an attractive measurement strategy for a number of health monitoring applications, primarily the ECG and the EEG. In all such applications a key technical challenge is the design of a low-noise trans-impedance preamplifier for the typically low-capacitance, high source impedance sensing electrodes. In this paper, we compare voltage and charge amplifier designs in terms of their common mode rejection ratio, noise performance, and frequency response. Both amplifier types employ the same operational-transconductance amplifier (OTA), which was fabricated in a 0.35 um CMOS process. The results show that a charge amplifier configuration has advantages for small electrode-to-subject coupling capacitance values (less than 10 pF--typical of noncontact electrodes) and that the voltage amplifier configuration has advantages for electrode capacitances above 10 pF.

Novel high-frequency energy-efficient pulsed-dc generator for capacitively coupled plasma discharge

NASA Astrophysics Data System (ADS)

Mamun, Md Abdullah Al; Furuta, Hiroshi; Hatta, Akimitsu

2018-03-01

The circuit design, assembly, and operating tests of a high-frequency and high-voltage (HV) pulsed dc generator (PDG) for capacitively coupled plasma (CCP) discharge inside a vacuum chamber are reported. For capacitive loads, it is challenging to obtain sharp rectangular pulses with fast rising and falling edges, requiring intense current for quick charging and discharging. The requirement of intense current generally limits the pulse operation frequency. In this study, we present a new type of PDG consisting of a pair of half-resonant converters and a constant current-controller circuit connected with HV solid-state power switches that can deliver almost rectangular high voltage pulses with fast rising and falling edges for CCP discharge. A prototype of the PDG is assembled to modulate from a high-voltage direct current (HVdc) input into a pulsed HVdc output, while following an input pulse signal and a set current level. The pulse rise time and fall time are less than 500 ns and 800 ns, respectively, and the minimum pulse width is 1 µs. The maximum voltage for a negative pulse is 1000 V, and the maximum repetition frequency is 500 kHz. During the pulse on time, the plasma discharge current is controlled steadily at the set value. The half-resonant converters in the PDG perform recovery of the remaining energy from the capacitive load at every termination of pulse discharge. The PDG performed with a high energy efficiency of 85% from the HVdc input to the pulsed dc output at a repetition rate of 1 kHz and with stable plasma operation in various discharge conditions. The results suggest that the developed PDG can be considered to be more efficient for plasma processing by CCP.

Novel high-frequency energy-efficient pulsed-dc generator for capacitively coupled plasma discharge.

PubMed

Mamun, Md Abdullah Al; Furuta, Hiroshi; Hatta, Akimitsu

2018-03-01

The circuit design, assembly, and operating tests of a high-frequency and high-voltage (HV) pulsed dc generator (PDG) for capacitively coupled plasma (CCP) discharge inside a vacuum chamber are reported. For capacitive loads, it is challenging to obtain sharp rectangular pulses with fast rising and falling edges, requiring intense current for quick charging and discharging. The requirement of intense current generally limits the pulse operation frequency. In this study, we present a new type of PDG consisting of a pair of half-resonant converters and a constant current-controller circuit connected with HV solid-state power switches that can deliver almost rectangular high voltage pulses with fast rising and falling edges for CCP discharge. A prototype of the PDG is assembled to modulate from a high-voltage direct current (HVdc) input into a pulsed HVdc output, while following an input pulse signal and a set current level. The pulse rise time and fall time are less than 500 ns and 800 ns, respectively, and the minimum pulse width is 1 µs. The maximum voltage for a negative pulse is 1000 V, and the maximum repetition frequency is 500 kHz. During the pulse on time, the plasma discharge current is controlled steadily at the set value. The half-resonant converters in the PDG perform recovery of the remaining energy from the capacitive load at every termination of pulse discharge. The PDG performed with a high energy efficiency of 85% from the HVdc input to the pulsed dc output at a repetition rate of 1 kHz and with stable plasma operation in various discharge conditions. The results suggest that the developed PDG can be considered to be more efficient for plasma processing by CCP.

Hysteresis in Lanthanide Aluminum Oxides Observed by Fast Pulse CV Measurement

PubMed Central

Zhao, Chun; Zhao, Ce Zhou; Lu, Qifeng; Yan, Xiaoyi; Taylor, Stephen; Chalker, Paul R.

2014-01-01

Oxide materials with large dielectric constants (so-called high-k dielectrics) have attracted much attention due to their potential use as gate dielectrics in Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). A novel characterization (pulse capacitance-voltage) method was proposed in detail. The pulse capacitance-voltage technique was employed to characterize oxide traps of high-k dielectrics based on the Metal Oxide Semiconductor (MOS) capacitor structure. The variation of flat-band voltages of the MOS structure was observed and discussed accordingly. Some interesting trapping/detrapping results related to the lanthanide aluminum oxide traps were identified for possible application in Flash memory technology. After understanding the trapping/detrapping mechanism of the high-k oxides, a solid foundation was prepared for further exploration into charge-trapping non-volatile memory in the future. PMID:28788225

Cavallo's multiplier for in situ generation of high voltage

NASA Astrophysics Data System (ADS)

Clayton, S. M.; Ito, T. M.; Ramsey, J. C.; Wei, W.; Blatnik, M. A.; Filippone, B. W.; Seidel, G. M.

2018-05-01

A classic electrostatic induction machine, Cavallo's multiplier, is suggested for in situ production of very high voltage in cryogenic environments. The device is suitable for generating a large electrostatic field under conditions of very small load current. Operation of the Cavallo multiplier is analyzed, with quantitative description in terms of mutual capacitances between electrodes in the system. A demonstration apparatus was constructed, and measured voltages are compared to predictions based on measured capacitances in the system. The simplicity of the Cavallo multiplier makes it amenable to electrostatic analysis using finite element software, and electrode shapes can be optimized to take advantage of a high dielectric strength medium such as liquid helium. A design study is presented for a Cavallo multiplier in a large-scale, cryogenic experiment to measure the neutron electric dipole moment.

Submicrosecond linear pulse transformer for 800 kV voltage with modular low-inductance primary power supply

NASA Astrophysics Data System (ADS)

Bykov, Yu. A.; Krastelev, E. G.; Popov, G. V.; Sedin, A. A.; Feduschak, V. F.

2016-12-01

A pulsed power source with voltage amplitude up to 800 kV for fast charging (350-400 ns) of the forming line of a high-current nanosecond accelerator is developed. The source includes capacitive energy storage and a linear pulse transformer. The linear transformer consists of a set of 20 inductors with circular ferromagnetic cores surrounded by primary windings inside of which a common stock adder of voltage with film-glycerol insulation is placed. The primary energy storage consists of ten modules, each of which is a low-inductance assembly of two capacitors with a capacitance of 0.35 μF and one gas switch mounted in the same frame. The total energy stored in capacitors is 5.5 kJ at the operating voltage of 40 kV. According to test results, the parameters of the equivalent circuit of the source are the following: shock capacitance = 17.5 nF, inductance = 2 μH, resistance = 3.2 Ω.

Submicrosecond linear pulse transformer for 800 kV voltage with modular low-inductance primary power supply

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bykov, Yu. A.; Krastelev, E. G., E-mail: ekrastelev@yandex.ru; Popov, G. V.

A pulsed power source with voltage amplitude up to 800 kV for fast charging (350–400 ns) of the forming line of a high-current nanosecond accelerator is developed. The source includes capacitive energy storage and a linear pulse transformer. The linear transformer consists of a set of 20 inductors with circular ferromagnetic cores surrounded by primary windings inside of which a common stock adder of voltage with film-glycerol insulation is placed. The primary energy storage consists of ten modules, each of which is a low-inductance assembly of two capacitors with a capacitance of 0.35 μF and one gas switch mounted inmore » the same frame. The total energy stored in capacitors is 5.5 kJ at the operating voltage of 40 kV. According to test results, the parameters of the equivalent circuit of the source are the following: shock capacitance = 17.5 nF, inductance = 2 μH, resistance = 3.2 Ω.« less

Series asymmetric supercapacitors based on free-standing inner-connection electrodes for high energy density and high output voltage.

PubMed

Tao, Jiayou; Liu, Nishuang; Rao, Jiangyu; Ding, Longwei; Al Bahrani, Majid Raissan; Li, Luying; Su, Jun; Gao, Yihua

2014-12-21

Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO(2) nanowire/carbon nanotube (CNT) composites and MoO(3) nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm(-3) at a scan rate of 2 mV s(-1) and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm(-3) at a power density of 261.4 mW cm(-3), and exhibits excellent cycling performance of 99.6% capacitance retention over 10,000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage.

Significance of the double-layer capacitor effect in polar rubbery dielectrics and exceptionally stable low-voltage high transconductance organic transistors.

PubMed

Wang, Chao; Lee, Wen-Ya; Kong, Desheng; Pfattner, Raphael; Schweicher, Guillaume; Nakajima, Reina; Lu, Chien; Mei, Jianguo; Lee, Tae Hoon; Wu, Hung-Chin; Lopez, Jeffery; Diao, Ying; Gu, Xiaodan; Himmelberger, Scott; Niu, Weijun; Matthews, James R; He, Mingqian; Salleo, Alberto; Nishi, Yoshio; Bao, Zhenan

2015-12-14

Both high gain and transconductance at low operating voltages are essential for practical applications of organic field-effect transistors (OFETs). Here, we describe the significance of the double-layer capacitance effect in polar rubbery dielectrics, even when present in a very low ion concentration and conductivity. We observed that this effect can greatly enhance the OFET transconductance when driven at low voltages. Specifically, when the polar elastomer poly(vinylidene fluoride-co-hexafluoropropylene) (e-PVDF-HFP) was used as the dielectric layer, despite a thickness of several micrometers, we obtained a transconductance per channel width 30 times higher than that measured for the same organic semiconductors fabricated on a semicrystalline PVDF-HFP with a similar thickness. After a series of detailed experimental investigations, we attribute the above observation to the double-layer capacitance effect, even though the ionic conductivity is as low as 10(-10) S/cm. Different from previously reported OFETs with double-layer capacitance effects, our devices showed unprecedented high bias-stress stability in air and even in water.

Significance of the double-layer capacitor effect in polar rubbery dielectrics and exceptionally stable low-voltage high transconductance organic transistors

PubMed Central

Wang, Chao; Lee, Wen-Ya; Kong, Desheng; Pfattner, Raphael; Schweicher, Guillaume; Nakajima, Reina; Lu, Chien; Mei, Jianguo; Lee, Tae Hoon; Wu, Hung-Chin; Lopez, Jeffery; Diao, Ying; Gu, Xiaodan; Himmelberger, Scott; Niu, Weijun; Matthews, James R.; He, Mingqian; Salleo, Alberto; Nishi, Yoshio; Bao, Zhenan

2015-01-01

Both high gain and transconductance at low operating voltages are essential for practical applications of organic field-effect transistors (OFETs). Here, we describe the significance of the double-layer capacitance effect in polar rubbery dielectrics, even when present in a very low ion concentration and conductivity. We observed that this effect can greatly enhance the OFET transconductance when driven at low voltages. Specifically, when the polar elastomer poly(vinylidene fluoride-co-hexafluoropropylene) (e-PVDF-HFP) was used as the dielectric layer, despite a thickness of several micrometers, we obtained a transconductance per channel width 30 times higher than that measured for the same organic semiconductors fabricated on a semicrystalline PVDF-HFP with a similar thickness. After a series of detailed experimental investigations, we attribute the above observation to the double-layer capacitance effect, even though the ionic conductivity is as low as 10–10 S/cm. Different from previously reported OFETs with double-layer capacitance effects, our devices showed unprecedented high bias-stress stability in air and even in water. PMID:26658331

Nanostructured bilayer anodic TiO2/Al2O3 metal-insulator-metal capacitor.

PubMed

Karthik, R; Kannadassan, D; Baghini, Maryam Shojaei; Mallick, P S

2013-10-01

This paper presents the fabrication of high performance bilayer TiO2/Al2O3 Metal-Insulator-Metal capacitor using anodization technique. A high capacitance density of 7 fF/microm2, low quadratic voltage coefficient of capacitance of 150 ppm/V2 and a low leakage current density of 9.1 nA/cm2 at 3 V are achieved which are suitable for Analog and Mixed signal applications. The influence of anodization voltage on structural and electrical properties of dielectric stack is studied in detail. At higher anodization voltages, we have observed the transformation of amorphous to crystalline state of TiO2/Al2O3 and improvement of electrical properties.

High-Voltage, Asymmetric-Waveform Generator

NASA Technical Reports Server (NTRS)

Beegle, Luther W.; Duong, Tuan A.; Duong, Vu A.; Kanik, Isik

2008-01-01

The shapes of waveforms generated by commercially available analytical separation devices, such as some types of mass spectrometers and differential mobility spectrometers are, in general, inadequate and result in resolution degradation in output spectra. A waveform generator was designed that would be able to circumvent these shortcomings. It is capable of generating an asymmetric waveform, having a peak amplitude as large as 2 kV and frequency of several megahertz, which can be applied to a capacitive load. In the original intended application, the capacitive load would consist of the drift plates in a differential-mobility spectrometer. The main advantage to be gained by developing the proposed generator is that the shape of the waveform is made nearly optimum for various analytical devices requiring asymmetric-waveform such as differential-mobility spectrometers. In addition, this waveform generator could easily be adjusted to modify the waveform in accordance with changed operational requirements for differential-mobility spectrometers. The capacitive nature of the load is an important consideration in the design of the proposed waveform generator. For example, the design provision for shaping the output waveform is based partly on the principle that (1) the potential (V) on a capacitor is given by V=q/C, where C is the capacitance and q is the charge stored in the capacitor; and, hence (2) the rate of increase or decrease of the potential is similarly proportional to the charging or discharging current. The proposed waveform generator would comprise four functional blocks: a sine-wave generator, a buffer, a voltage shifter, and a high-voltage switch (see Figure 1). The sine-wave generator would include a pair of operational amplifiers in a feedback configuration, the parameters of which would be chosen to obtain a sinusoidal timing signal of the desired frequency. The buffer would introduce a slight delay (approximately equal to 20 ns) but would otherwise leave the fundamental timing signal unchanged. The buffered timing signal would be fed as input to the level shifter. The output of the level shifter would serve as a timing and control signal for the high-voltage switch, causing the switch to alternately be (1) opened, allowing the capacitive load to be charged from a high-voltage DC power supply; then (2) closed to discharge the capacitive load to ground. Hence, the output waveform would closely approximate a series of exponential charging and discharging curves (see Figure 2).

Capacitance-voltage characterization of Al/Al2O3/PVA-PbSe MIS diode

NASA Astrophysics Data System (ADS)

Gawri, Isha; Sharma, Mamta; Jindal, Silky; Singh, Harpreet; Tripathi, S. K.

2018-05-01

The present paper reports the capacitance-voltage characterization of Al/Al2O3/PVA-PbSe MIS diode using chemical bath deposition method. Here anodic alumina layer prepared using electrolytic deposition method on Al substrate is used as insulating material. Using the capacitance-voltage variation at a fixed frequency, the different parameters such as Depletion layer width, Barrier height, Built-in voltage and Carrier concentration has been calculated at room temperature as well as at temperature range from 123 K to 323 K. With the increase in temperature the barrier height and depletion layer width follow a decreasing trend. Therefore, the capacitance-voltage characterization at different temperatures characterization provides strong evidence that the properties of MIS diode are primarily affected by diode parameters.

Contamination of current-clamp measurement of neuron capacitance by voltage-dependent phenomena

PubMed Central

White, William E.

2013-01-01

Measuring neuron capacitance is important for morphological description, conductance characterization, and neuron modeling. One method to estimate capacitance is to inject current pulses into a neuron and fit the resulting changes in membrane potential with multiple exponentials; if the neuron is purely passive, the amplitude and time constant of the slowest exponential give neuron capacitance (Major G, Evans JD, Jack JJ. Biophys J 65: 423–449, 1993). Golowasch et al. (Golowasch J, Thomas G, Taylor AL, Patel A, Pineda A, Khalil C, Nadim F. J Neurophysiol 102: 2161–2175, 2009) have shown that this is the best method for measuring the capacitance of nonisopotential (i.e., most) neurons. However, prior work has not tested for, or examined how much error would be introduced by, slow voltage-dependent phenomena possibly present at the membrane potentials typically used in such work. We investigated this issue in lobster (Panulirus interruptus) stomatogastric neurons by performing current clamp-based capacitance measurements at multiple membrane potentials. A slow, voltage-dependent phenomenon consistent with residual voltage-dependent conductances was present at all tested membrane potentials (−95 to −35 mV). This phenomenon was the slowest component of the neuron's voltage response, and failure to recognize and exclude it would lead to capacitance overestimates of several hundredfold. Most methods of estimating capacitance depend on the absence of voltage-dependent phenomena. Our demonstration that such phenomena make nonnegligible contributions to neuron responses even at well-hyperpolarized membrane potentials highlights the critical importance of checking for such phenomena in all work measuring neuron capacitance. We show here how to identify such phenomena and minimize their contaminating influence. PMID:23576698

Organic memory device with self-assembly monolayered aptamer conjugated nanoparticles

NASA Astrophysics Data System (ADS)

Oh, Sewook; Kim, Minkeun; Kim, Yejin; Jung, Hunsang; Yoon, Tae-Sik; Choi, Young-Jin; Jung Kang, Chi; Moon, Myeong-Ju; Jeong, Yong-Yeon; Park, In-Kyu; Ho Lee, Hyun

2013-08-01

An organic memory structure using monolayered aptamer conjugated gold nanoparticles (Au NPs) as charge storage nodes was demonstrated. Metal-pentacene-insulator-semiconductor device was adopted for the non-volatile memory effect through self assembly monolayer of A10-aptamer conjugated Au NPs, which was formed on functionalized insulator surface with prostate-specific membrane antigen protein. The capacitance versus voltage (C-V) curves obtained for the monolayered Au NPs capacitor exhibited substantial flat-band voltage shift (ΔVFB) or memory window of 3.76 V under (+/-)7 V voltage sweep. The memory device format can be potentially expanded to a highly specific capacitive sensor for the aptamer-specific biomolecule detection.

Synaptic transistor with a reversible and analog conductance modulation using a Pt/HfOx/n-IGZO memcapacitor

NASA Astrophysics Data System (ADS)

Yang, Paul; Kim, Hyung Jun; Zheng, Hong; Beom, Geon Won; Park, Jong-Sung; Kang, Chi Jung; Yoon, Tae-Sik

2017-06-01

A synaptic transistor emulating the biological synaptic motion is demonstrated using the memcapacitance characteristics in a Pt/HfOx/n-indium-gallium-zinc-oxide (IGZO) memcapacitor. First, the metal-oxide-semiconductor (MOS) capacitor with Pt/HfOx/n-IGZO structure exhibits analog, polarity-dependent, and reversible memcapacitance in capacitance-voltage (C-V), capacitance-time (C-t), and voltage-pulse measurements. When a positive voltage is applied repeatedly to the Pt electrode, the accumulation capacitance increases gradually and sequentially. The depletion capacitance also increases consequently. The capacitances are restored by repeatedly applying a negative voltage, confirming the reversible memcapacitance. The analog and reversible memcapacitance emulates the potentiation and depression synaptic motions. The synaptic thin-film transistor (TFT) with this memcapacitor also shows the synaptic motion with gradually increasing drain current by repeatedly applying the positive gate and drain voltages and reversibly decreasing one by applying the negative voltages, representing synaptic weight modulation. The reversible and analog conductance change in the transistor at both the voltage sweep and pulse operations is obtained through the memcapacitance and threshold voltage shift at the same time. These results demonstrate the synaptic transistor operations with a MOS memcapacitor gate stack consisting of Pt/HfOx/n-IGZO.

Synaptic transistor with a reversible and analog conductance modulation using a Pt/HfOx/n-IGZO memcapacitor.

PubMed

Yang, Paul; Jun Kim, Hyung; Zheng, Hong; Won Beom, Geon; Park, Jong-Sung; Jung Kang, Chi; Yoon, Tae-Sik

2017-06-02

A synaptic transistor emulating the biological synaptic motion is demonstrated using the memcapacitance characteristics in a Pt/HfOx/n-indium-gallium-zinc-oxide (IGZO) memcapacitor. First, the metal-oxide-semiconductor (MOS) capacitor with Pt/HfOx/n-IGZO structure exhibits analog, polarity-dependent, and reversible memcapacitance in capacitance-voltage (C-V), capacitance-time (C-t), and voltage-pulse measurements. When a positive voltage is applied repeatedly to the Pt electrode, the accumulation capacitance increases gradually and sequentially. The depletion capacitance also increases consequently. The capacitances are restored by repeatedly applying a negative voltage, confirming the reversible memcapacitance. The analog and reversible memcapacitance emulates the potentiation and depression synaptic motions. The synaptic thin-film transistor (TFT) with this memcapacitor also shows the synaptic motion with gradually increasing drain current by repeatedly applying the positive gate and drain voltages and reversibly decreasing one by applying the negative voltages, representing synaptic weight modulation. The reversible and analog conductance change in the transistor at both the voltage sweep and pulse operations is obtained through the memcapacitance and threshold voltage shift at the same time. These results demonstrate the synaptic transistor operations with a MOS memcapacitor gate stack consisting of Pt/HfOx/n-IGZO.

Functional Carbon Materials for Electrochemical Energy Storage

NASA Astrophysics Data System (ADS)

Zhou, Huihui

The ability to harvest and convert solar energy has been associated with the evolution of human civilization. The increasing consumption of fossil fuels since the industrial revolution, however, has brought to concerns in ecological deterioration and depletion of the fossil fuels. Facing these challenges, humankind is forced to seek for clean, sustainable and renewable energy resources, such as biofuels, hydraulic power, wind power, geothermal energy and other kinds of alternative energies. However, most alternative energy sources, generally in the form of electrical energy, could not be made available on a continuous basis. It is, therefore, essential to store such energy into chemical energy, which are portable and various applications. In this context, electrochemical energy-storage devices hold great promises towards this goal. The most common electrochemical energy-storage devices are electrochemical capacitors (ECs, also called supercapacitors) and batteries. In comparison to batteries, ECs posses high power density, high efficiency, long cycling life and low cost. ECs commonly utilize carbon as both (symmetric) or one of the electrodes (asymmetric), of which their performance is generally limited by the capacitance of the carbon electrodes. Therefore, developing better carbon materials with high energy density has been emerging as one the most essential challenges in the field. The primary objective of this dissertation is to design and synthesize functional carbon materials with high energy density at both aqueous and organic electrolyte systems. The energy density (E) of ECs are governed by E = CV 2/2, where C is the total capacitance and V is the voltage of the devices. Carbon electrodes with high capacitance and high working voltage should lead to high energy density. In the first part of this thesis, a new class of nanoporous carbons were synthesized for symmetric supercapacitors using aqueous Li2SO4 as the electrolyte. A unique precursor was adopted to create uniformly distributed nanopores with large surface area, leading to high-performance electrodes with high capacitance, excellent rate performance and stable cycling, even under a high working voltage of 1.6V. The second part of this dissertation work further improved the capacitance of the carbon electrodes by fluorine doping. This doping process enhances the affinity of the carbon surface with organic electrolytes, leading to further improved capacitance and energy density. In the third part, carbon materials were synthesized with high surface area, capacitance and working voltage of 4V in organic electrolyte, leading to the construction of prototyped devices with energy density comparable to those of the current lead-acid batteries. Besides the abovementioned research, hierarchical graphitic carbons were also explored for lithium ion batteries and supercapacitors. Overall, through rational design of carbons with optimized pore configuration and surface chemistry, carbon electrodes with improved energy density and rate performance were improved significantly. Collectively, this thesis work systematically unveils simple yet effective strategies to achieve high performance carbon-based supercapacitors with high power density and high energy density, including the following aspects: 1) Constructed electrodes with high capacitance through building favorable ion/electron transportation pathways, tuning pore structure and pore size. 2) Improved the capacitance through enhancing the affinity between the carbon electrodes and electrolytes by doping the carbons with heteroatoms. 3) Explored and understand the roles of heteroatom doping in the capacitive behavior by both experimental measurement and computational modeling. 4) Improved energy density of carbon electrodes by enlarging their working voltage in aqueous and organic electrolyte. 5) Scalable and effective production of hierarchically porous graphite particles through aerosol process for use as the anode materials of lithium ion batteries. These strategies can be extended as a general design platform for other high-performance energy storage materials such as fuel cells and lithium-ion batteries.

Preamplifiers for non-contact capacitive biopotential measurements*

PubMed Central

Peng, GuoChen; Ignjatovic, Zeljko; Bocko, Mark F.

2014-01-01

Non-contact biopotential sensing is an attractive measurement strategy for a number of health monitoring applications, primarily the ECG and the EEG. In all such applications a key technical challenge is the design of a low-noise trans-impedance preamplifier for the typically low-capacitance, high source impedance sensing electrodes. In this paper, we compare voltage and charge amplifier designs in terms of their common mode rejection ratio, noise performance, and frequency response. Both amplifier types employ the same operational-transconductance amplifier (OTA), which was fabricated in a 0.35um CMOS process. The results show that a charge amplifier configuration has advantages for small electrode-to-subject coupling capacitance values (less than 10 pF - typical of noncontact electrodes) and that the voltage amplifier configuration has advantages for electrode capacitances above 10 pF. PMID:24109979

Temperature aspect of degradation of electrochemical double-layer capacitors (EDLC)

NASA Astrophysics Data System (ADS)

Baek, Dong-Cheon; Kim, Hyun-Ho; Lee, Soon-Bok

2015-03-01

Electric double layer capacitors (EDLC) cells have a process variation and temperature dependency in capacitance so that balancing is required when they are connected in series, which includes electronic voltage management based on capacitance monitoring. This paper measured temperature aspect of capacitance periodically to monitor health and degradation behavior of EDLC stressed under high temperatures and zero below temperatures respectively, which enables estimation of the state of health (SOH) regardless of temperature. At high temperature, capacitance saturation and delayed expression of degradation was observed. After cyclic stress at zero below temperature, less effective degradation and time recovery phenomenon were occurred.

Capacitively coupled RF voltage probe having optimized flux linkage

DOEpatents

Moore, James A.; Sparks, Dennis O.

1999-02-02

An RF sensor having a novel current sensing probe and a voltage sensing probe to measure voltage and current. The current sensor is disposed in a transmission line to link all of the flux generated by the flowing current in order to obtain an accurate measurement. The voltage sensor is a flat plate which operates as a capacitive plate to sense voltage on a center conductor of the transmission line, in which the measured voltage is obtained across a resistance leg of a R-C differentiator circuit formed by the characteristic impedance of a connecting transmission line and a capacitance of the plate, which is positioned proximal to the center conductor.

High-voltage pulse generator developed for wide-gap spark chambers

NASA Technical Reports Server (NTRS)

Keller, L. P.; Walschon, E. G.

1968-01-01

Low-inductance, high-capacitance Marx pulse generator provides for minimization of internal inductance and suppression of external electromagnetic radiation. The spark gaps of the generator are enclosed in a pressurized nitrogen atmosphere which allows the charging voltage to be varied by changing the nitrogen pressure.

Capacitively-coupled inductive sensor

DOEpatents

Ekdahl, Carl A.

1984-01-01

A capacitively coupled inductive shunt current sensor which utilizes capacitive coupling between flanges having an annular inductive channel formed therein. A voltage dividing capacitor is connected between the coupling capacitor and ground to provide immediate capacitive division of the output signal so as to provide a high frequency response of the current pulse to be detected. The present invention can be used in any desired outer conductor such as the outer conductor of a coaxial transmission line, the outer conductor of an electron beam transmission line, etc.

Nonlinear antiferroelectric-like capacitance-voltage curves in ferroelectric BiFeO3 thin films

NASA Astrophysics Data System (ADS)

Jiang, A. Q.; Zhang, D. W.; Tang, T. A.

2013-07-01

The ferroelectric capacitance is usually nonlinear against increasing/decreasing voltage in sweeping time longer than 1 s and achieves a maximum value at around a coercive voltage within each loop. With the improved short-pulse measurements, we estimated the differential capacitance of ferroelectric Au/BiFeO3/LaNiO3/SrTiO3 thin-film capacitors from a nanosecond discharging current induced by a delta voltage after a stressing voltage pulse with widths of 500 ns-50 ms. With the shortening of the voltage sweeping time, we clearly observed two capacitance maxima from each branch of a capacitance-voltage (C-V) loop, reminiscent of an antiferroelectric behavior. After transformation of nanosecond domain switching current transients under pulses into polarization-voltage hysteresis loops, we further measured time dependent polarization retention as well as imprint in the range of 100 ns-1 s. Both positive and negative polarizations decay exponentially at characteristic times of 2.25 and 198 μs, suggesting the coexistence of preferred domains pointing to top and bottom electrodes in most epitaxial films. This exponential time dependence is similar to the dielectric degradation under a dc voltage, and the polarization retention can be improved through long-time opposite voltage stressing. With this improvement, the additional antiferroelectric-like dielectric maximum within each branch of a C-V loop disappears. This experiment provides the strong evidence of the effect of time-dependent charge injection on polarization retention and dielectric degradation.

Capacitance of Ti 3C 2T x MXene in Ionic Liquid Electrolyte

DOE PAGES

Lin, Zifeng; Barbara, Daffos; Taberna, Pierre-Louis; ...

2016-04-14

Ti 3C 2T x MXene, a two-dimensional (2D) early transition metal carbide, has shown an extremely high volumetric capacitance in aqueous electrolytes, but in a narrow voltage window (less than 1.23 V). The utilization of MXene materials in ionic liquid electrolytes with a large voltage window has never been addressed. Here, we report the preparation of the Ti 3C 2T x MXene ionogel film by vacuum filtration for use as supercapacitor electrodes operating in 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI) neat ionic liquid electrolyte. Due to the disordered structure of the Ti 3C 2T x hydrogel film and a stable spacing after vacuummore » drying, achieved through ionic liquid electrolyte immersion of the Ti 3C 2T x hydrogel film, the Ti 3C 2T x surface became accessible to EMI + and TFSI - ions. A capacitance of 70 F g -1 together with a large voltage window of 3 V was obtained at a scan rate of 20 mV s -1 in neat EMI-TFSI electrolyte. The electrochemical signature indicates a capacitive behavior even at a high scan rate (500 mV s -1) and a high power performance. This work opens up the possibilities of using MXene materials with various ionic liquid electrolytes.« less

Analysis of capacitive force acting on a cantilever tip at solid/liquid interfaces

NASA Astrophysics Data System (ADS)

Umeda, Ken-ichi; Kobayashi, Kei; Oyabu, Noriaki; Hirata, Yoshiki; Matsushige, Kazumi; Yamada, Hirofumi

2013-04-01

Dielectric properties of biomolecules or biomembranes are directly related to their structures and biological activities. Capacitance force microscopy based on the cantilever deflection detection is a useful scanning probe technique that can map local dielectric constant. Here we report measurements and analysis of the capacitive force acting on a cantilever tip at solid/liquid interfaces induced by application of an alternating voltage to explore the feasibility of the measurements of local dielectric constant by the voltage modulation technique in aqueous solutions. The results presented here suggest that the local dielectric constant measurements by the conventional voltage modulation technique are basically possible even in polar liquid media. However, the cantilever deflection is not only induced by the electrostatic force, but also by the surface stress, which does not include the local dielectric information. Moreover, since the voltage applied between the tip and sample are divided by the electric double layer and the bulk polar liquid, the capacitive force acting on the apex of the tip are strongly attenuated. For these reasons, the lateral resolution in the local dielectric constant measurements is expected to be deteriorated in polar liquid media depending on the magnitude of dielectric response. Finally, we present the criteria for local dielectric constant measurements with a high lateral resolution in polar liquid media.

Lumped transmission line avalanche pulser

DOEpatents

Booth, R.

1995-07-18

A lumped linear avalanche transistor pulse generator utilizes stacked transistors in parallel within a stage and couples a plurality of said stages, in series with increasing zener diode limited voltages per stage and decreasing balanced capacitance load per stage to yield a high voltage, high and constant current, very short pulse. 8 figs.

Lumped transmission line avalanche pulser

DOEpatents

Booth, Rex

1995-01-01

A lumped linear avalanche transistor pulse generator utilizes stacked transistors in parallel within a stage and couples a plurality of said stages, in series with increasing zener diode limited voltages per stage and decreasing balanced capacitance load per stage to yield a high voltage, high and constant current, very short pulse.

Method and apparatus for measuring low currents in capacitance devices

DOEpatents

Kopp, M.K.; Manning, F.W.; Guerrant, G.C.

1986-06-04

A method and apparatus for measuring subnanoampere currents in capacitance devices is reported. The method is based on a comparison of the voltages developed across the capacitance device with that of a reference capacitor in which the current is adjusted by means of a variable current source to produce a stable voltage difference. The current varying means of the variable current source is calibrated to provide a read out of the measured current. Current gain may be provided by using a reference capacitor which is larger than the device capacitance with a corresponding increase in current supplied through the reference capacitor. The gain is then the ratio of the reference capacitance to the device capacitance. In one illustrated embodiment, the invention makes possible a new type of ionizing radiation dose-rate monitor where dose-rate is measured by discharging a reference capacitor with a variable current source at the same rate that radiation is discharging an ionization chamber. The invention eliminates high-megohm resistors and low current ammeters used in low-current measuring instruments.

New experimental techniques for solar cells

NASA Technical Reports Server (NTRS)

Lenk, R.

1993-01-01

Solar cell capacitance has special importance for an array controlled by shunting. Experimental measurements of solar cell capacitance in the past have shown disagreements of orders of magnitude. Correct measurement technique depends on maintaining the excitation voltage less than the thermal voltage. Two different experimental methods are shown to match theory well, and two effective capacitances are defined for quantifying the effect of the solar cell capacitance on the shunting system.

Attofarad resolution capacitance-voltage measurement of nanometer scale field effect transistors utilizing ambient noise.

PubMed

Gokirmak, Ali; Inaltekin, Hazer; Tiwari, Sandip

2009-08-19

A high resolution capacitance-voltage (C-V) characterization technique, enabling direct measurement of electronic properties at the nanoscale in devices such as nanowire field effect transistors (FETs) through the use of random fluctuations, is described. The minimum noise level required for achieving sub-aF (10(-18) F) resolution, the leveraging of stochastic resonance, and the effect of higher levels of noise are illustrated through simulations. The non-linear DeltaC(gate-source/drain)-V(gate) response of FETs is utilized to determine the inversion layer capacitance (C(inv)) and carrier mobility. The technique is demonstrated by extracting the carrier concentration and effective electron mobility in a nanoscale Si FET with C(inv) = 60 aF.

Memristor-integrated voltage-stabilizing supercapacitor system.

PubMed

Liu, Bin; Liu, Boyang; Wang, Xianfu; Wu, Xinghui; Zhao, Wenning; Xu, Zhimou; Chen, Di; Shen, Guozhen

2014-08-06

Voltage-stabilized supercapacitors: A single supercapacitor formed with PCBM/Pt/IPS nanorod-array electrodes is designed and delivers enhanced areal capacitance, capacitance retention, and excellent electrical stability under bending, while a significant voltage-decrease is observed during the discharging process. Once integrated with the memristor, the memristor-integrated supercapacitor systems deliver an extremely low voltage-drop, indicating greatly enhanced voltage-stabilizing features. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Self-Nulling Lock-in Detection Electronics for Capacitance Probe Electrometer

NASA Technical Reports Server (NTRS)

Blaes, Brent R.; Schaefer, Rembrandt T.

2012-01-01

A multi-channel electrometer voltmeter that employs self-nulling lock-in detection electronics in conjunction with a mechanical resonator with noncontact voltage sensing electrodes has been developed for space-based measurement of an Internal Electrostatic Discharge Monitor (IESDM). The IESDM is new sensor technology targeted for integration into a Space Environmental Monitor (SEM) subsystem used for the characterization and monitoring of deep dielectric charging on spacecraft. Use of an AC-coupled lock-in amplifier with closed-loop sense-signal nulling via generation of an active guard-driving feedback voltage provides the resolution, accuracy, linearity and stability needed for long-term space-based measurement of the IESDM. This implementation relies on adjusting the feedback voltage to drive the sense current received from the resonator s variable-capacitance-probe voltage transducer to approximately zero, as limited by the signal-to-noise performance of the loop electronics. The magnitude of the sense current is proportional to the difference between the input voltage being measured and the feedback voltage, which matches the input voltage when the sense current is zero. High signal-to-noise-ratio (SNR) is achieved by synchronous detection of the sense signal using the correlated reference signal derived from the oscillator circuit that drives the mechanical resonator. The magnitude of the feedback voltage, while the loop is in a settled state with essentially zero sense current, is an accurate estimate of the input voltage being measured. This technique has many beneficial attributes including immunity to drift, high linearity, high SNR from synchronous detection of a single-frequency carrier selected to avoid potentially noisy 1/f low-frequency spectrum of the signal-chain electronics, and high accuracy provided through the benefits of a driven shield encasing the capacitance- probe transducer and guarded input triaxial lead-in. Measurements obtained from a 2- channel prototype electrometer have demonstrated good accuracy (|error| < 0.2 V) and high stability. Twenty-four-hour tests have been performed with virtually no drift. Additionally, 5,500 repeated one-second measurements of 100 V input were shown to be approximately normally distributed with a standard deviation of 140 mV.

A high-performance supercapacitor electrode based on N-doped porous graphene

NASA Astrophysics Data System (ADS)

Dai, Shuge; Liu, Zhen; Zhao, Bote; Zeng, Jianhuang; Hu, Hao; Zhang, Qiaobao; Chen, Dongchang; Qu, Chong; Dang, Dai; Liu, Meilin

2018-05-01

The development of high-performance supercapacitors (SCs) often faces some contradictory and competing requirements such as excellent rate capability, long cycling life, and high energy density. One effective strategy is to explore electrode materials of high capacitance, electrode architectures of fast charge and mass transfer, and electrolytes of wide voltage window. Here we report a facile and readily scalable strategy to produce high-performance N-doped graphene with a high specific capacitance (∼390 F g-1). A symmetric SC device with a wide voltage window of 3.5 V is also successfully fabricated based on the N-doped graphene electrode. More importantly, the as-assembled symmetric SC delivers a high energy density of 55 Wh kg-1 at a power density of 1800 W kg-1 while maintaining superior cycling life (retaining 96.6% of the initial capacitance after 20,000 cycles). Even at a power density as high as 8800 W kg-1, it still retains an energy density of 29 Wh kg-1, higher than those of previously reported graphene-based symmetric SCs.

Ultrahigh surface area meso/microporous carbon formed with self-template for high-voltage aqueous supercapacitors

NASA Astrophysics Data System (ADS)

Yang, Jie; Hu, Jiangtao; Zhu, Min; Zhao, Yan; Chen, Haibiao; Pan, Feng

2017-10-01

A new hierarchically porous carbon has been synthesized with self-template of silica phase from a commercial silicone resin by pyrolysis and subsequent NaOH activation. The obtained carbon materials achieve an ultrahigh specific surface area (2896 m2 g-1) with abundant mesopores. The C800 sample demonstrates excellent performance in supercapacitors, with a high capacitance of 322 F g-1 at 0.5 A g-1 and outstanding rate capability (182 F g-1 at 100 A g-1) in a three-electrode system using 6.0 mol L-1 KOH electrolyte. The energy density is improved by widening the voltage window using 1.0 mol L-1 alkali metal nitrate solutions (LiNO3, NaNO3, KNO3) in which the strong solvation of alkali metal cations and nitrate anions effectively reduce the activity of water. In a symmetric supercapacitor, the maximum operating voltage is essentially restricted by the potential of positive electrode and the total capacitance is dominated by the capacitance of the anion at the positive electrode. The symmetric supercapacitors based on C800 deliver a high energy density of 22.4 Wh kg-1 at a power density of 0.23 kW kg-1 in 1.0 mol L-1 LiNO3 with a voltage of 1.8 V and long-term stability with a retention of 89.87% after 10000 cycles.

Estimation of intrinsic and extrinsic capacitances of graphene self-switching diode using conformal mapping technique

NASA Astrophysics Data System (ADS)

Singh, Arun K.; Auton, Gregory; Hill, Ernie; Song, Aimin

2018-07-01

Due to a very high carrier concentration and low band gap, graphene based self-switching diodes do not demonstrate a very high rectification ratio. Despite that, it takes the advantage of graphene’s high carrier mobility and has been shown to work at very high microwave frequencies. However, the AC component of these devices is hidden in the very linear current–voltage characteristics. Here, we extract and quantitatively study the device capacitance that determines the device nonlinearity by implementing a conformal mapping technique. The estimated value of the nonlinear component or curvature coefficient from DC results based on Shichman–Hodges model predicts the rectified output voltage, which is in good agreement with the experimental RF results.

Disinfection by electrohydraulic treatment.

PubMed

Allen, M; Soike, K

1967-04-28

Electrohydraulic treatment was applied to suspensions of Escherichia coli, spores of Bacillus subtilis var. niger, Saccharomyces cerevisiae, and bacteriophage T2 at an input energy that, in most cases, was below the energy required to sterilize. The input energy was held relatively constant for each of these microorganisms, but the capacitance and voltage were varied. Data are presented which show the degree of disinfection as a function of capacitance and voltage. In all cases, the degree of disinfection for a given input energy increases as both capacitance and voltage are lowered.

Increased Multilayer Fabrication and RF Characterization of a High-Density Stacked MIM Capacitor Based on Selective Etching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tseng, VFG; Xie, HK

2014-07-01

This paper presents the fabrication and characterization of a high-density multilayer stacked metal-insulator-metal (MIM) capacitor based on a novel process of depositing the MIM multilayer on pillars followed by polishing and selective etching steps to form a stacked capacitor with merely three photolithography steps. In this paper, the pillars were made of glass to prevent substrate loss, whereas an oxide-nitride-oxide dielectric was employed for lower leakage, better voltage/frequency linearity, and better stress compensation. MIM capacitors with six dielectric layers were successfully fabricated, yielding capacitance density of 3.8 fF/mu m(2), maximum capacitance of 2.47 nF, and linear and quadratic voltage coefficientsmore » of capacitance below 21.2 ppm/V and 2.31 ppm/V-2. The impedance was measured from 40 Hz to 3 GHz, and characterized by an analytically derived equivalent circuit model to verify the radio frequency applicability. The multilayer stacking-induced plate resistance mismatch and its effect on the equivalent series resistance (ESR) and effective capacitance was also investigated, which can be counteracted by a corrected metal thickness design. A low ESR of 800 m Omega was achieved, whereas the self-resonance frequency was >760 MHz, successfully demonstrating the feasibility of this method to scale up capacitance densities for high-quality-factor, high-frequency, and large-value MIM capacitors.« less

Side-gate modulation effects on high-quality BN-Graphene-BN nanoribbon capacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yang; Chen, Xiaolong; Ye, Weiguang

High-quality BN-Graphene-BN nanoribbon capacitors with double side-gates of graphene have been experimentally realized. The double side-gates can effectively modulate the electronic properties of graphene nanoribbon capacitors. By applying anti-symmetric side-gate voltages, we observed significant upward shifting and flattening of the V-shaped capacitance curve near the charge neutrality point. Symmetric side-gate voltages, however, only resulted in tilted upward shifting along the opposite direction of applied gate voltages. These modulation effects followed the behavior of graphene nanoribbons predicted theoretically for metallic side-gate modulation. The negative quantum capacitance phenomenon predicted by numerical simulations for graphene nanoribbons modulated by graphene side-gates was not observed,more » possibly due to the weakened interactions between the graphene nanoribbon and side-gate electrodes caused by the Ga{sup +} beam etching process.« less

Permanent split capacitor single phase electric motor system

DOEpatents

Kirschbaum, Herbert S.

1984-01-01

A permanent split capacitor single phase electric motor achieves balanced operation at more than one operating point by adjusting the voltage supplied to the main and auxiliary windings and adjusting the capacitance in the auxiliary winding circuit. An intermediate voltage tap on an autotransformer supplies voltage to the main winding for low speed operation while a capacitive voltage divider is used to adjust the voltage supplied to the auxiliary winding for low speed operation.

Fast capacitive probe for electromagnetic pulse diagnostic.

PubMed

Lorusso, A; Nassisi, V; Siciliano, M V

2008-06-01

In this work, we report the study and the development of a capacitive probe which is suitable for getting fast and high voltage/current measurements. Due to the fact that fast pulses propagate generally in coaxial structures, the probe realized in this work was a capacitive divider with the divider electrode properly designed to assure the same characteristic impedance of the coaxial structure and the recombination time of the split signals during the propagation. It was a folded cylindrical ring of 1.4 cm long and 0.8 cm thick, which introduce a theoretical delay time of about 100 ps. Analyzing the behavior of the probe closed on 520 Omega, the voltage amplification resulted to be of (3.6+/-0.1) x 10(-4) and, as a consequence, the current attenuation factor of 56+/-1 AV. The response rise time was less than 320 ps, which was limited by oscilloscope bandwave. The capacitor probe can operate voltage measurements of the order of 100 kV.

Macro Fiber Piezocomposite Actuator Poling Study

NASA Technical Reports Server (NTRS)

Werlink, Rudy J.; Bryant, Robert G.; Manos, Dennis

2002-01-01

The performance and advantages of Piezocomposite Actuators are to provide a low cost, in-situ actuator/sensor that is flexible, low profile and high strain per volt performance in the same plane of poled voltage. This paper extends reported data for the performance of these Macrofiber Composite (MFC) Actuators to include 4 progressively narrower Intedigitized electrode configurations with several line widths and spacing ratios. Data is reported for max free strain, average strain per applied volt, poling (alignment of the electric dipoles of the PZT ceramic) voltage vs. strain and capacitance, time to poling voltage 95% saturation. The output strain per volt progressively increases as electrode spacing decreases, with saturation occurring at lower poling voltages. The narrowest spacing ratio becomes prone to voltage breakdown or short circuits limiting the spacing width with current fabrication methods. The capacitance generally increases with increasing poling voltage level but has high sensitivity to factors such as temperature, moisture and time from poling which limit its usefulness as a simple indicator. The total time of applied poling voltage to saturate or fully line up the dipoles in the piezoceramic was generally on the order of 5-20 seconds. Less sensitivity to poling due to the applied rate of voltage increase over a 25 to 500 volt/second rate range was observed.

High performance, flexible, poly(3,4-ethylenedioxythiophene) supercapacitors achieved by doping redox mediators in organogel electrolytes

NASA Astrophysics Data System (ADS)

Zhang, Huanhuan; Li, Jinyu; Gu, Cheng; Yao, Mingming; Yang, Bing; Lu, Ping; Ma, Yuguang

2016-11-01

The relatively low energy density is now a central issue hindering the development of supercapacitors as energy storage devices. Various approaches are thus developed to enhance the energy density, mainly centering on the fabrication of electrode materials or optimization of cell configurations. Compared with these approaches, modifications in electrolytes are much simple and versatile. Herein, we integrate the wide voltages endowed by organic electrolytes and the additional capacitances brought by redox mediators, to fabricate high energy density supercapacitors. On the basis of this idea, supercapacitors with poly(3,4-ethylenedioxythiophene) (PEDOT) as electrode material exhibit extended operating voltage of 1.5 V, extraordinary capacitance of 363 F g-1 and high energy density of 27.4 Wh kg-1. The redox mediators reported here, ferrocene and 4-oxo-2,2,6,6-tetramethylpiperidinooxy, are the first time being applied in supercapacitors, especially in the gel state. While providing additional faradaic capacitances, they also exhibit synergistic interaction with PEDOT and improve the cycling stability of supercapacitors.

Voltage and frequency dependence of prestin-associated charge transfer

PubMed Central

Sun, Sean X.; Farrell, Brenda; Chana, Matthew S.; Oster, George; Brownell, William E.; Spector, Alexander A.

2009-01-01

Membrane protein prestin is a critical component of the motor complex that generates forces and dimensional changes in cells in response to changes in the cell membrane potential. In its native cochlear outer hair cell, prestin is crucial to the amplification and frequency selectivity of the mammalian ear up to frequencies of tens of kHz. Other cells transfected with prestin acquire voltage-dependent properties similar to those of the native cell. The protein performance is critically dependent on chloride ions, and intrinsic protein charges also play a role. We propose an electro-diffusion model to reveal the frequency and voltage dependence of electric charge transfer by prestin. The movement of the combined charge (i.e., anion and protein charges) across the membrane is described with a Fokker-Planck equation coupled to a kinetic equation that describes the binding of chloride ions to prestin. We found a voltage-and frequency-dependent phase shift between the transferred charge and the applied electric field that determines capacitive and resistive components of the transferred charge. The phase shift monotonically decreases from zero to -90 degree as a function of frequency. The capacitive component as a function of voltage is bell-shaped, and decreases with frequency. The resistive component is bell-shaped for both voltage and frequency. The capacitive and resistive components are similar to experimental measurements of charge transfer at high frequencies. The revealed nature of the transferred charge can help reconcile the high-frequency electrical and mechanical observations associated with prestin, and it is important for further analysis of the structure and function of this protein. PMID:19490917

Phase-Discriminating Capacitive Sensor System

NASA Technical Reports Server (NTRS)

Vranish, John M.; Rahim, Wadi

1993-01-01

Crosstalk eliminated by maintaining voltages on all electrodes at same amplitude, phase, and frequency. Each output feedback-derived control voltage, change of which indicates proximity-induced change in capacitance of associated sensing electrode. Sensors placed close together, enabling imaging of sort. Images and/or output voltages used to guide robots in proximity to various objects.

High voltage bushing having weathershed and surrounding stress relief collar

DOEpatents

Cookson, Alan H.

1981-01-01

A high voltage electric bushing comprises a hollow elongated dielectric weathershed which encloses a high voltage conductor. A collar formed of high voltage dielectric material is positioned over the weathershed and is bonded thereto by an interface material which precludes moisture-like contaminants from entering between the bonded portions. The collar is substantially thicker than the adjacent weathershed which it surrounds, providing relief of the electric stresses which would otherwise appear on the outer surface of the weathershed. The collar may include a conductive ring or capacitive foil to further relieve electric stresses experienced by the bushing.

Permanent split capacitor single phase electric motor system

DOEpatents

Kirschbaum, H.S.

1984-08-14

A permanent split capacitor single phase electric motor achieves balanced operation at more than one operating point by adjusting the voltage supplied to the main and auxiliary windings and adjusting the capacitance in the auxiliary winding circuit. An intermediate voltage tap on an autotransformer supplies voltage to the main winding for low speed operation while a capacitive voltage divider is used to adjust the voltage supplied to the auxiliary winding for low speed operation. 4 figs.

Electropolymerized polyazulene as active material in flexible supercapacitors

NASA Astrophysics Data System (ADS)

Suominen, Milla; Lehtimäki, Suvi; Yewale, Rahul; Damlin, Pia; Tuukkanen, Sampo; Kvarnström, Carita

2017-07-01

We report the capacitive behavior of electrochemically polymerized polyazulene films in different ionic liquids. The ionic liquids in this study represent conventional imidazolium based ionic liquids with tetrafluoroborate and bis(trifluoromethylsulfonyl)imide anions as well as an unconventional choline based ionic liquid. The effect of different ionic liquids on the polymerization and capacitive performance of polyazulene films is demonstrated by cyclic voltammetry and electrochemical impedance spectroscopy in a 3-electrode cell configuration. The films exhibit the highest capacitances in the lowest viscosity ionic liquid (92 mF cm-2), while synthesis in high viscosity ionic liquid shortens the conjugation length and results in lower electroactivity (25 mF cm-2). The obtained films also show good cycling stabilities retaining over 90% of their initial capacitance over 1200 p-doping cycles. We also demonstrate, for the first time, flexible polyazulene supercapacitors of symmetric and asymmetric configurations using the choline based ionic liquid as electrolyte. In asymmetric configuration, capacitance of 55 mF (27 mF cm-2) with an equivalent series resistance of 19 Ω is obtained at operating voltage of 1.5 V. Upon increasing the operating voltage up to 2.4 V, the capacitance increases to 72 mF (36 mF cm-2).

Threshold-Voltage Shifts in Organic Transistors Due to Self-Assembled Monolayers at the Dielectric: Evidence for Electronic Coupling and Dipolar Effects.

PubMed

Aghamohammadi, Mahdieh; Rödel, Reinhold; Zschieschang, Ute; Ocal, Carmen; Boschker, Hans; Weitz, R Thomas; Barrena, Esther; Klauk, Hagen

2015-10-21

The mechanisms behind the threshold-voltage shift in organic transistors due to functionalizing of the gate dielectric with self-assembled monolayers (SAMs) are still under debate. We address the mechanisms by which SAMs determine the threshold voltage, by analyzing whether the threshold voltage depends on the gate-dielectric capacitance. We have investigated transistors based on five oxide thicknesses and two SAMs with rather diverse chemical properties, using the benchmark organic semiconductor dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene. Unlike several previous studies, we have found that the dependence of the threshold voltage on the gate-dielectric capacitance is completely different for the two SAMs. In transistors with an alkyl SAM, the threshold voltage does not depend on the gate-dielectric capacitance and is determined mainly by the dipolar character of the SAM, whereas in transistors with a fluoroalkyl SAM the threshold voltages exhibit a linear dependence on the inverse of the gate-dielectric capacitance. Kelvin probe force microscopy measurements indicate this behavior is attributed to an electronic coupling between the fluoroalkyl SAM and the organic semiconductor.

Hybrid MnO2/carbon nanotube-VN/carbon nanotube supercapacitors

NASA Astrophysics Data System (ADS)

Su, Y.; Zhitomirsky, I.

2014-12-01

Composite materials, containing fibrous VN nanoparticles and multiwalled carbon nanotubes (MWCNT) are prepared by a chemical method for application in electrochemical supercapacitors. We demonstrate for the first time that VN-MWCNT electrodes exhibit good capacitive behavior in 0.5 M Na2SO4 electrolyte in a negative voltage window of 0.9 V. Quartz crystal microbalance studies provide an insight into the mechanism of charge storage. Composite VN-MWCNT materials show significant improvement in capacitance, compared to individual VN and MWCNT materials. Testing results indicate that VN-MWCNT electrodes exhibit high specific capacitance at high mass loadings in the range of 10-30 mg cm-2, good capacitance retention at scan rates in the range of 2-200 mV s-1 and good cycling stability. The highest specific capacitance of 160 F g-1 is achieved at a scan rate of 2 mV s-1. The new findings open a new and promising strategy in the fabrication of hybrid devices based on VN. The proof-of-principle is demonstrated by the fabrication of hybrid supercapacitor devices based on VN-MWCNT negative electrodes and MnO2 -MWCNT positive electrodes with voltage window of 1.8 V in aqueous 0.5 M Na2SO4 electrolyte. The hybrid VN-MWCNT/MnO2-MWCNT supercapacitor cells show promising capacitive and power-energy characteristics.

Isolating the effect of pore size distribution on electrochemical double-layer capacitance using activated fluid coke

NASA Astrophysics Data System (ADS)

Zuliani, Jocelyn E.; Tong, Shitang; Kirk, Donald W.; Jia, Charles Q.

2015-12-01

Electrochemical double-layer capacitors (EDLCs) use physical ion adsorption in the capacitive electrical double layer of high specific surface area (SSA) materials to store electrical energy. Previous work shows that the SSA-normalized capacitance increases when pore diameters are less than 1 nm. However, there still remains uncertainty about the charge storage mechanism since the enhanced SSA-normalized capacitance is not observed in all microporous materials. In previous studies, the total specific surface area and the chemical composition of the electrode materials were not controlled. The current work is the first reported study that systematically compares the performance of activated carbon prepared from the same raw material, with similar chemical composition and specific surface area, but different pore size distributions. Preparing samples with similar SSAs, but different pores sizes is not straightforward since increasing pore diameters results in decreasing the SSA. This study observes that the microporous activated carbon has a higher SSA-normalized capacitance, 14.1 μF cm-2, compared to the mesoporous material, 12.4 μF cm-2. However, this enhanced SSA-normalized capacitance is only observed above a threshold operating voltage. Therefore, it can be concluded that a minimum applied voltage is required to induce ion adsorption in these sub-nanometer micropores, which increases the capacitance.

Combined electrical transport and capacitance spectroscopy of a MoS2-LiNbO3 field effect transistor

NASA Astrophysics Data System (ADS)

Michailow, Wladislaw; Schülein, Florian J. R.; Möller, Benjamin; Preciado, Edwin; Nguyen, Ariana E.; von Son, Gretel; Mann, John; Hörner, Andreas L.; Wixforth, Achim; Bartels, Ludwig; Krenner, Hubert J.

2017-01-01

We have measured both the current-voltage ( ISD - VGS ) and capacitance-voltage (C- VGS ) characteristics of a MoS2-LiNbO3 field effect transistor. From the measured capacitance, we calculate the electron surface density and show that its gate voltage dependence follows the theoretical prediction resulting from the two-dimensional free electron model. This model allows us to fit the measured ISD - VGS characteristics over the entire range of VGS . Combining this experimental result with the measured current-voltage characteristics, we determine the field effect mobility as a function of gate voltage. We show that for our device, this improved combined approach yields significantly smaller values (more than a factor of 4) of the electron mobility than the conventional analysis of the current-voltage characteristics only.

Nanostructured Anodic Multilayer Dielectric Stacked Metal-Insulator-Metal Capacitors.

PubMed

Karthik, R; Kannadassan, D; Baghini, Maryam Shojaei; Mallick, P S

2015-12-01

This paper presents the fabrication of Al2O3/TiO2/Al2O3 metal-insulator-metal (MIM) capacitor using anodization technique. High capacitance density of > 3.5 fF/μm2, low quadratic voltage coefficient of capacitance of < 115 ppm/V2 and a low leakage current density of 4.457 x 10(-11) A/cm2 at 3 V are achieved which are suitable for analog and mixed signal applications. We found that the anodization voltage played a major role in electrical and structural properties of the thin film. This work suggests that the anodization method can offer crystalline multilayer dielectric stack required for high performance MIM capacitor.

The Influence of Materials of Electrodes of Sensitized Solar Cells on Their Capacitive and Electrical Characteristics

NASA Astrophysics Data System (ADS)

Lazarenko, P. I.; Kozyukhin, S. A.; Mokshina, A. I.; Sherchenkov, A. A.; Patrusheva, T. N.; Irgashev, R. A.; Lebedev, E. A.; Kozik, V. V.

2018-05-01

An estimation is made of the internal capacitance of sensitized solar cells (SSCs) manufactured by the method of extraction pyrolysis. The structures under study are characterized by a hysteresis in the current-voltage characteristic obtained in the direct and reverse modes of voltage variation. The investigations of SSCs demonstrate a high inertness of the parameters under connection and disconnection of the light source. The use of a transparent conductive ITO-electrode, manufactured by the extraction pyrolysis, increases the external capacitance of the cell and decelerates the processes of current decay after the light source connection compared to the commercial FTO-electrode. The values of charges, capacitances, and SSC charge conservation efficiencies are calculated and the internal resistance of the SSCs under study is estimated. According to the estimations performed, the specimen with an ITO-layer possesses a capacitance equal to C1 = 1.23·10-3 F, which is by two orders of magnitude higher than that of the specimen with a FTO-layer (C2 = 2.06·10-5 F).

Regulation of a lightweight high efficiency capacitator diode voltage multiplier dc-dc converter

NASA Technical Reports Server (NTRS)

Harrigill, W. T., Jr.; Myers, I. T.

1976-01-01

A method for the regulation of a capacitor diode voltage multiplier dc-dc converter has been developed which has only minor penalties in weight and efficiency. An auxiliary inductor is used, which only handles a fraction of the total power, to control the output voltage through a pulse width modulation method in a buck boost circuit.

A Novel Optoelectronic Device Based on Correlated Two-Dimensional Fermions

NASA Astrophysics Data System (ADS)

Dianat, Pouya

Conventional metallic contacts can be replicated by quantum two dimensional charge (of Fermion) systems (2DFS). Unlike metals, the particle concentration of these "unconventional" systems can be accurately controlled in an extensive range and by means of external electronic or optical stimuli. A 2DFS can, hence, transition from a high-density kinetic liquid into a dilute-but highly correlated-gas state, in which inter-particle Coulombic interactions are significant. Such interactions contribute negatively, by so-called exchange-correlation energies, to the overall energetics of the system, and are manifested as a series negative quantum capacitance. This dissertation investigates the capacitive performance of a class of unconventional devices based on a planar metal-semiconductor-metal structure with an embedded 2DFS. They constitute an opto-electronically controlled variable capacitor, with record breaking figures-of-merit in capacitance tuning ranges of up to 7000 and voltage sensitivities as large as 400. Internal eld manipulations by localized depletion of a dense 2DFS account for the enlarged maximum and reduced minimum capacitances. The capacitance-voltage characteristics of these devices incur an anomalous "Batman" shape capacitance enhancement (CE) of up to 200% that may be triggered optically. The CE is attributed to the release and storage of exchange-correlation energies; from the "unconventional" plate and in the dielectric, respectively. This process is enforced by density manipulation of the 2DFS by a hybrid of an external eld and light-generated carriers. Under moderate optical powers, the capacitance becomes 43 times greater than the dark value; thus a new capacitance-based photodetection method is offered. This new capacitance based photodetection method has a range of applications in optoelectronics, particularly in the next generation of photonic integrated systems.

A transient simulation approach to obtaining capacitance-voltage characteristics of GaN MOS capacitors with deep-level traps

NASA Astrophysics Data System (ADS)

Fukuda, Koichi; Asai, Hidehiro; Hattori, Junichi; Shimizu, Mitsuaki; Hashizume, Tamotsu

2018-04-01

In this study, GaN MOS capacitance-voltage device simulations considering various interface and bulk traps are performed in the transient mode. The simulations explain various features of capacitance-voltage curves, such as plateau, hysteresis, and frequency dispersions, which are commonly observed in measurements of GaN MOS capacitors and arise from complicated combinations of interface and bulk deep-level traps. The objective of the present study is to provide a good theoretical tool to understand the physics of various nonideal measured curves.

Profiling of barrier capacitance and spreading resistance using a transient linearly increasing voltage technique.

PubMed

Gaubas, E; Ceponis, T; Kusakovskij, J

2011-08-01

A technique for the combined measurement of barrier capacitance and spreading resistance profiles using a linearly increasing voltage pulse is presented. The technique is based on the measurement and analysis of current transients, due to the barrier and diffusion capacitance, and the spreading resistance, between a needle probe and sample. To control the impact of deep traps in the barrier capacitance, a steady state bias illumination with infrared light was employed. Measurements of the spreading resistance and barrier capacitance profiles using a stepwise positioned probe on cross sectioned silicon pin diodes and pnp structures are presented.

FAST TRACK COMMUNICATION High mobility and low operating voltage ZnGaO and ZnGaLiO transistors with spin-coated Al2O3 as gate dielectric

NASA Astrophysics Data System (ADS)

Xia, D. X.; Xu, J. B.

2010-11-01

Spin-coated alumina serving as a gate dielectric in thin film transistors shows interesting dielectric properties for low-voltage applications, despite a moderate capacitance. With Ga singly doped and Ga, Li co-doped ZnO as the active channel layers, typical mobilities of 4.7 cm2 V-1 s-1 and 2.1 cm2 V-1 s-1 are achieved, respectively. At a given gate bias, the operation current is much smaller than the previously reported values in low-voltage thin film transistors, primarily relying on the giant-capacitive dielectric. The reported devices combine advantages of high mobility, low power consumption, low cost and ease of fabrication. In addition to the transparent nature of both the dielectric and semiconducting active channels, the superior electrical properties of the devices may provide a new avenue for future transparent electronics.

Generation of a pulsed low-energy electron beam using the channel spark device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elgarhy, M. A. I., E-mail: elgarhy@azhar.edu.eg; Hassaballa, S. E.; Rashed, U. M.

2015-12-15

For the generation of low-energy electron beam, the design and characteristics of channel spark discharge (CSD) operating at a low voltage are presented in this paper. The discharge voltage, discharge current, X-ray emissions, and electron beam current were experimentally determined. The effects of the applied voltage, working gas pressure, and external capacitance on the CSD and beam parameters were measured. At an applied voltage of 11 kV, an oxygen gas pressure of 25 mTorr, and an external capacitance of 16.45 nF, the maximum measured current was 900 A. The discharge current increased with the increase in the pressure and capacitance,more » while its periodic time decreased with the increase in the pressure. Two types of the discharge were identified and recorded: the hollow cathode discharge and the conduction discharge. A Faraday cup was used to measure the beam current. The maximum measured beam current was 120 A, and the beam signal exhibited two peaks. The increase in both the external capacitance and the applied discharge voltage increased the maximum electron beam current. The electron-beam pulse time decreased with the increase in the gas pressure at a constant voltage and increased with the decrease in the applied discharge voltage. At an applied voltage of 11 kV and an oxygen gas pressure of 15 mTorr, the maximum beam energy was 2.8 keV. The X-ray signal intensity decreased with the increase in the gas pressure and increased with the increase in the capacitance.« less

Estimation of carrier mobility and charge behaviors of organic semiconductor films in metal-insulator-semiconductor diodes consisting of high-k oxide/organic semiconductor double layers

NASA Astrophysics Data System (ADS)

Chosei, Naoya; Itoh, Eiji

2018-02-01

We have comparatively studied the charge behaviors of organic semiconductor films based on charge extraction by linearly increasing voltage in a metal-insulator-semiconductor (MIS) diode structure (MIS-CELIV) and by classical capacitance-voltage measurement. The MIS-CELIV technique allows the selective measurement of electron and hole mobilities of n- and p-type organic films with thicknesses representative of those of actual devices. We used an anodic oxidized sputtered Ta or Hf electrode as a high-k layer, and it effectively blocked holes at the insulator/semiconductor interface. We estimated the hole mobilities of the polythiophene derivatives regioregular poly(3-hexylthiophene) (P3HT) and poly(3,3‧‧‧-didodecylquarterthiophene) (PQT-12) before and after heat treatment in the ITO/high-k/(thin polymer insulator)/semiconductor/MoO3/Ag device structure. The hole mobility of PQT-12 was improved from 1.1 × 10-5 to 2.1 × 10-5 cm2 V-1 s-1 by the heat treatment of the device at 100 °C for 30 min. An almost two orders of magnitude higher mobility was obtained in MIS diodes with P3HT as the p-type layer. We also determined the capacitance from the displacement current in MIS diodes at a relatively low-voltage sweep, and it corresponded well to the classical capacitance-voltage and frequency measurement results.

Line transients with corona

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saied, M.M.; Safar, Y.A.; Salama, M.H.

1987-01-01

This paper investigates the effect of corona on the electromagnetic transients along high voltage overhead lines. A method is presented to simulate the line by dividing it into a number of sections connected in cascade. For {ital n} line sections, the number of the unknown variables is 2{ital n} + 1. The method allows any waveform of the exciting voltage function, as well as any impedance loading condition. The corona is represented by voltage-dependent shunt current sources. A systematic way for writing a sufficient number of differential equations is shown. For their solution, a digital computer subroutine based on themore » Runge--Kutta--Verner method was used. An artificial frequency-dependent damping by means of linear resistors was used to suppress the Gibb's oscillations in the solution. The proposed method is applied to study the transients on a 40 km high voltage line with 30-ft flat phase spacing and a single 1.4 inch ACSR conductor per phase. The exciting voltage has a double-exponential impulse waveform. Solutions are given for three values of resistive loads Z{sub {ital c}}2Z{sub {ital c}} and Z{sub {ital c}}/2, where Z{sub {ital c}} is the line surge impedance. The results of two interesting cases of inductive and capacitive loads are also given. Physical interpretations for the different solutions are given. Also, the current-voltage duality between inductive and capacitive loads is recognized. The corona was found to attenuate and distort the travelling waves. For example, during one wave excursion, the reduction of the current wave peaks can reach values as high as 8.5%. The effect is more noticeable in the current than in the voltage waves. As expected, it increases also with the line corona losses. The effect of the increase of the line effective capacitance due to the corona discharge is also demonstrated.« less

A parallel input composite transimpedance amplifier.

PubMed

Kim, D J; Kim, C

2018-01-01

A new approach to high performance current to voltage preamplifier design is presented. The design using multiple operational amplifiers (op-amps) has a parasitic capacitance compensation network and a composite amplifier topology for fast, precision, and low noise performance. The input stage consisting of a parallel linked JFET op-amps and a high-speed bipolar junction transistor (BJT) gain stage driving the output in the composite amplifier topology, cooperating with the capacitance compensation feedback network, ensures wide bandwidth stability in the presence of input capacitance above 40 nF. The design is ideal for any two-probe measurement, including high impedance transport and scanning tunneling microscopy measurements.

A parallel input composite transimpedance amplifier

NASA Astrophysics Data System (ADS)

Kim, D. J.; Kim, C.

2018-01-01

A new approach to high performance current to voltage preamplifier design is presented. The design using multiple operational amplifiers (op-amps) has a parasitic capacitance compensation network and a composite amplifier topology for fast, precision, and low noise performance. The input stage consisting of a parallel linked JFET op-amps and a high-speed bipolar junction transistor (BJT) gain stage driving the output in the composite amplifier topology, cooperating with the capacitance compensation feedback network, ensures wide bandwidth stability in the presence of input capacitance above 40 nF. The design is ideal for any two-probe measurement, including high impedance transport and scanning tunneling microscopy measurements.

Module Eleven: Capacitance; Basic Electricity and Electronics Individualized Learning System.

ERIC Educational Resources Information Center

Bureau of Naval Personnel, Washington, DC.

In this module the student will learn about another circuit quantity, capacitance, and discover the effects of this component on circuit current, voltage, and power. The module is divided into seven lessons: the capacitor, theory of capacitance, total capacitance, RC (resistive-capacitive circuit) time constant, capacitive reactance, phase and…

Investigation of Defect Distributions in SiO2/AlGaN/GaN High-Electron-Mobility Transistors by Using Capacitance-Voltage Measurement with Resonant Optical Excitation

NASA Astrophysics Data System (ADS)

Kim, Tae-Soo; Lim, Seung-Young; Park, Yong-Keun; Jung, Gunwoo; Song, Jung-Hoon; Cha, Ho-Young; Han, Sang-Woo

2018-06-01

We investigated the distributions and the energy levels of defects in SiO2/AlGaN/GaN highelectron-mobility transistors (HEMTs) by using frequency-dependent ( F- D) capacitance-voltage ( C- V) measurements with resonant optical excitation. A Schottky barrier (SB) and a metal-oxidesemiconductor (MOS) HEMT were prepared to compare the effects of defects in their respective layers. We also investigated the effects of those layers on the threshold voltage ( V th ). A drastic voltage shift in the C- V curve at higher frequencies was caused by the large number of defect levels in the SiO2/GaN interface. A significant shift in V th with additional light illumination was observed due to a charging of the defect states in the SiO2/GaN interface. The voltage shifts were attributed to the detrapping of defect states at the SiO2/GaN interface.

Capacitance probe for detection of anomalies in non-metallic plastic pipe

DOEpatents

Mathur, Mahendra P.; Spenik, James L.; Condon, Christopher M.; Anderson, Rodney; Driscoll, Daniel J.; Fincham, Jr., William L.; Monazam, Esmail R.

2010-11-23

The disclosure relates to analysis of materials using a capacitive sensor to detect anomalies through comparison of measured capacitances. The capacitive sensor is used in conjunction with a capacitance measurement device, a location device, and a processor in order to generate a capacitance versus location output which may be inspected for the detection and localization of anomalies within the material under test. The components may be carried as payload on an inspection vehicle which may traverse through a pipe interior, allowing evaluation of nonmetallic or plastic pipes when the piping exterior is not accessible. In an embodiment, supporting components are solid-state devices powered by a low voltage on-board power supply, providing for use in environments where voltage levels may be restricted.

Multifunctional voltage source inverter for renewable energy integration and power quality conditioning.

PubMed

Dai, NingYi; Lam, Chi-Seng; Zhang, WenChen

2014-01-01

In order to utilize the energy from the renewable energy sources, power conversion system is necessary, in which the voltage source inverter (VSI) is usually the last stage for injecting power to the grid. It is an economical solution to add the function of power quality conditioning to the grid-connected VSI in the low-voltage distribution system. Two multifunctional VSIs are studied in this paper, that is, inductive-coupling VSI and capacitive-coupling VSI, which are named after the fundamental frequency impedance of their coupling branch. The operation voltages of the two VSIs are compared when they are used for renewable energy integration and power quality conditioning simultaneously. The operation voltage of the capacitive-coupling VSI can be set much lower than that of the inductive-coupling VSI when reactive power is for compensating inductive loads. Since a large portion of the loads in the distribution system are inductive, the capacitive-coupling VSI is further studied. The design and control method of the multifunctional capacitive-coupling VSI are proposed in this paper. Simulation and experimental results are provided to show its validity.

Multifunctional Voltage Source Inverter for Renewable Energy Integration and Power Quality Conditioning

PubMed Central

Dai, NingYi; Lam, Chi-Seng; Zhang, WenChen

2014-01-01

In order to utilize the energy from the renewable energy sources, power conversion system is necessary, in which the voltage source inverter (VSI) is usually the last stage for injecting power to the grid. It is an economical solution to add the function of power quality conditioning to the grid-connected VSI in the low-voltage distribution system. Two multifunctional VSIs are studied in this paper, that is, inductive-coupling VSI and capacitive-coupling VSI, which are named after the fundamental frequency impedance of their coupling branch. The operation voltages of the two VSIs are compared when they are used for renewable energy integration and power quality conditioning simultaneously. The operation voltage of the capacitive-coupling VSI can be set much lower than that of the inductive-coupling VSI when reactive power is for compensating inductive loads. Since a large portion of the loads in the distribution system are inductive, the capacitive-coupling VSI is further studied. The design and control method of the multifunctional capacitive-coupling VSI are proposed in this paper. Simulation and experimental results are provided to show its validity. PMID:25177725

LaF3 insulators for MIS structures

NASA Technical Reports Server (NTRS)

Sher, A.; Tsuo, Y. H.; Moriarty, J. A.; Miller, W. E.; Crouch, R. K.; Seiber, B. A.

1979-01-01

Thin films of LaF3 deposited on Si or GaAs substrates have been observed to form blocking contacts with very high capacitances. This results in comparatively hysteresis-free and sharp C-V (capacitance-voltage) characteristics for MIS structures. Such structures have been used to study the interface states of GaAs with increased resolution and to construct improved photocapacitive infrared detectors.

Characteristics of arc currents on a negatively biased solar cell array in a plasma

NASA Technical Reports Server (NTRS)

Snyder, D. B.

1984-01-01

The time dependence of the emitted currents during arcing on solar cell arrays is being studied. The arcs are characterized using three parameters: the voltage change of the array during the arc (i.e., the charge lost), the peak current during the arc, and the time constant describing the arc current. This paper reports the dependence of these characteristics on two array parameters, the interconnect bias voltage and the array capacitance to ground. It was found that the voltage change of the array during an arc is nearly equal to the bias voltage. The array capacitance, on the other hand, influences both the peak current and the decay time constant of the arc. Both of these characteristics increase with increasing capacitance.

Conductivity Variation Observed by Polarization and Depolarization Current Measurements of High-Voltage Equipment Insulation System

NASA Astrophysics Data System (ADS)

Jamail, Nor Akmal Mohd; Piah, Mohamed Afendi Mohamed; Muhamad, Nor Asiah

2012-09-01

Nondestructive and time domain dielectric measurement techniques such as polarization and depolarization current (PDC) measurements have recently been widely used as a potential tool for determining high-voltage insulation conditions by analyzing the insulation conductivity. The variation in the conductivity of an insulator was found to depend on several parameters: the difference between the polarization and depolarization currents, geometric capacitance, and the relative permittivity of the insulation material. In this paper the conductivities of different types of oil-paper insulation material are presented. The insulation conductivities of several types of electrical apparatus were simulated using MATLAB. Conductivity insulation was found to be high at high polarizations and at the lowest depolarization current. It was also found to increase with increasing relative permittivity as well as with decreasing geometric capacitance of the insulating material.

Negative capacitance in a ferroelectric capacitor.

PubMed

Khan, Asif Islam; Chatterjee, Korok; Wang, Brian; Drapcho, Steven; You, Long; Serrao, Claudy; Bakaul, Saidur Rahman; Ramesh, Ramamoorthy; Salahuddin, Sayeef

2015-02-01

The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of a phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here, we report the observation of negative capacitance in a thin, epitaxial ferroelectric film. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time--in exactly the opposite direction to which voltage for a regular capacitor should change. Analysis of this 'inductance'-like behaviour from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material and could pave the way for completely new applications.

Temporal differentiation of pH-dependent capacitive current from dopamine.

PubMed

Yoshimi, Kenji; Weitemier, Adam

2014-09-02

Voltammetric recording of dopamine (DA) with fast-scan cyclic voltammetry (FSCV) on carbon fiber microelectrodes have been widely used, because of its high sensitivity to dopamine. However, since an electric double layer on a carbon fiber surface in a physiological ionic solution behaves as a capacitor, fast voltage manipulation in FSCV induces large capacitive current. The faradic current from oxidation/reduction of target chemicals must be extracted from this large background current. It is known that ionic shifts, including H(+), influence this capacitance, and pH shift can cause confounding influences on the FSCV recordings within a wide range of voltage. Besides FSCV with a triangular waveform, we have been using rectangular pulse voltammetry (RPV) for dopamine detection in the brain. In this method, the onset of a single pulse causes a large capacitive current, but unlike FSCV, the capacitive current is restricted to a narrow temporal window of just after pulse onset (<5 ms). In contrast, the peak of faradic current from dopamine oxidation occurs after a delay of more than a few milliseconds. Taking advantage of the temporal difference, we show that RPV could distinguish dopamine from pH shifts clearly and easily. In addition, the early onset current was useful to evaluate pH shifts. The narrow voltage window of our RPV pulse allowed a clear differentiation of dopamine and serotonin (5-HT), as we have shown previously. Additional recording with RPV, alongside FSCV, would improve identification of chemicals such as dopamine, pH, and 5-HT.

Frequency and voltage dependent electrical responses of poly(triarylamine) thin film-based organic Schottky diode

NASA Astrophysics Data System (ADS)

Anuar Mohamad, Khairul; Tak Hoh, Hang; Alias, Afishah; Ghosh, Bablu Kumar; Fukuda, Hisashi

2017-11-01

A metal-organic-metal (MOM) type Schottky diode based on poly (triarylamine) (PTAA) thin films has been fabricated by using the spin coating method. Investigation of the frequency dependent conductance-voltage (G-V-f) and capacitance-voltage (C-V-f) characteristics of the ITO/PTAA/Al MOM type diode were carried out in the frequency range from 12 Hz to 100 kHz using an LCR meter at room temperature. The frequency and bias voltage dependent electrical response were determined by admittance-based measured method in terms of an equivalent circuit model of the parallel combination of resistance and capacitance (RC circuit). Investigation revealed that the conductance is frequency and a bias voltage dependent in which conductance continuous increase as the increasing frequency, respectively. Meanwhile, the capacitance is dependent on frequency up to a certain value of frequency (100 Hz) but decreases at high frequency (1 - 10 kHz). The interface state density in the Schottky diode was determined from G-V and C-V characteristics. The interface state density has values almost constant of 2.8 x 1012 eV-1cm-2 with slightly decrease by increasing frequencies. Consequently, both series resistance and interface trap density were found to decrease with increasing frequency. The frequency dependence of the electrical responses is attributed the distribution density of interface states that could follow the alternating current (AC) signal.

Solid structures with bioorganic films on silicon

NASA Astrophysics Data System (ADS)

Tutov, E. A.

2012-06-01

The electrophysical parameters of ovalbumin/silicon and propolis/silicon heterostructures are studied using impedance spectroscopy and high-frequency capacitance-voltage characteristics under water vapor sorption conditions.

Graphene/Polyaniline Aerogel with Superelasticity and High Capacitance as Highly Compression-Tolerant Supercapacitor Electrode

NASA Astrophysics Data System (ADS)

Lv, Peng; Tang, Xun; Zheng, Ruilin; Ma, Xiaobo; Yu, Kehan; Wei, Wei

2017-12-01

Superelastic graphene aerogel with ultra-high compressibility shows promising potential for compression-tolerant supercapacitor electrode. However, its specific capacitance is too low to meet the practical application. Herein, we deposited polyaniline (PANI) into the superelastic graphene aerogel to improve the capacitance while maintaining the superelasticity. Graphene/PANI aerogel with optimized PANI mass content of 63 wt% shows the improved specific capacitance of 713 F g-1 in the three-electrode system. And the graphene/PANI aerogel presents a high recoverable compressive strain of 90% due to the strong interaction between PANI and graphene. The all-solid-state supercapacitors were assembled to demonstrate the compression-tolerant ability of graphene/PANI electrodes. The gravimetric capacitance of graphene/PANI electrodes reaches 424 F g-1 and retains 96% even at 90% compressive strain. And a volumetric capacitance of 65.5 F cm-3 is achieved, which is much higher than that of other compressible composite electrodes. Furthermore, several compressible supercapacitors can be integrated and connected in series to enhance the overall output voltage, suggesting the potential to meet the practical application.

Graphene/Polyaniline Aerogel with Superelasticity and High Capacitance as Highly Compression-Tolerant Supercapacitor Electrode.

PubMed

Lv, Peng; Tang, Xun; Zheng, Ruilin; Ma, Xiaobo; Yu, Kehan; Wei, Wei

2017-12-19

Superelastic graphene aerogel with ultra-high compressibility shows promising potential for compression-tolerant supercapacitor electrode. However, its specific capacitance is too low to meet the practical application. Herein, we deposited polyaniline (PANI) into the superelastic graphene aerogel to improve the capacitance while maintaining the superelasticity. Graphene/PANI aerogel with optimized PANI mass content of 63 wt% shows the improved specific capacitance of 713 F g -1 in the three-electrode system. And the graphene/PANI aerogel presents a high recoverable compressive strain of 90% due to the strong interaction between PANI and graphene. The all-solid-state supercapacitors were assembled to demonstrate the compression-tolerant ability of graphene/PANI electrodes. The gravimetric capacitance of graphene/PANI electrodes reaches 424 F g -1 and retains 96% even at 90% compressive strain. And a volumetric capacitance of 65.5 F cm -3 is achieved, which is much higher than that of other compressible composite electrodes. Furthermore, several compressible supercapacitors can be integrated and connected in series to enhance the overall output voltage, suggesting the potential to meet the practical application.

Raman spectrum method for characterization of pull-in voltages of graphene capacitive shunt switches

NASA Astrophysics Data System (ADS)

Li, Peng; You, Zheng; Cui, Tianhong

2012-12-01

An approach using Raman spectrum method is reported to measure pull-in voltages of graphene capacitive shunt switches. When the bias excesses the pull-in voltage, the Raman spectrum's intensity largely decreases. Two factors that contribute to the intensity reduction are investigated. Moreover, by monitoring the frequency shift of G peak and 2D band, we are able to detect the pull-in voltage and measure the strain change in graphene beams during switching.

Voltage equalization of an ultracapacitor module by cell grouping using number partitioning algorithm

NASA Astrophysics Data System (ADS)

Oyarbide, E.; Bernal, C.; Molina, P.; Jiménez, L. A.; Gálvez, R.; Martínez, A.

2016-01-01

Ultracapacitors are low voltage devices and therefore, for practical applications, they need to be used in modules of series-connected cells. Because of the inherent manufacturing tolerance of the capacitance parameter of each cell, and as the maximum voltage value cannot be exceeded, the module requires inter-cell voltage equalization. If the intended application suffers repeated fast charging/discharging cycles, active equalization circuits must be rated to full power, and thus the module becomes expensive. Previous work shows that a series connection of several sets of paralleled ultracapacitors minimizes the dispersion of equivalent capacitance values, and also the voltage differences between capacitors. Thus the overall life expectancy is improved. This paper proposes a method to distribute ultracapacitors with a number partitioning-based strategy to reduce the dispersion between equivalent submodule capacitances. Thereafter, the total amount of stored energy and/or the life expectancy of the device can be considerably improved.

Analytical expressions for noise and crosstalk voltages of the High Energy Silicon Particle Detector

NASA Astrophysics Data System (ADS)

Yadav, I.; Shrimali, H.; Liberali, V.; Andreazza, A.

2018-01-01

The paper presents design and implementation of a silicon particle detector array with the derived closed form equations of signal-to-noise ratio (SNR) and crosstalk voltages. The noise analysis demonstrates the effect of interpixel capacitances (IPC) between center pixel (where particle hits) and its neighbouring pixels, resulting as a capacitive crosstalk. The pixel array has been designed and simulated in a 180 nm BCD technology of STMicroelectronics. The technology uses the supply voltage (VDD) of 1.8 V and the substrate potential of -50 V. The area of unit pixel is 250×50 μm2 with the substrate resistivity of 125 Ωcm and the depletion depth of 30 μm. The mathematical model includes the effects of various types of noise viz. the shot noise, flicker noise, thermal noise and the capacitive crosstalk. This work compares the results of noise and crosstalk analysis from the proposed mathematical model with the circuit simulation results for a given simulation environment. The results show excellent agreement with the circuit simulations and the mathematical model. The average relative error (AVR) generated for the noise spectral densities with respect to the simulations and the model is 12% whereas the comparison gives the errors of 3% and 11.5% for the crosstalk voltages and the SNR results respectively.

Role of the dielectric for the charging dynamics of the dielectric/barrier interface in AlGaN/GaN based metal-insulator-semiconductor structures under forward gate bias stress

NASA Astrophysics Data System (ADS)

Lagger, P.; Steinschifter, P.; Reiner, M.; Stadtmüller, M.; Denifl, G.; Naumann, A.; Müller, J.; Wilde, L.; Sundqvist, J.; Pogany, D.; Ostermaier, C.

2014-07-01

The high density of defect states at the dielectric/III-N interface in GaN based metal-insulator-semiconductor structures causes tremendous threshold voltage drifts, ΔVth, under forward gate bias conditions. A comprehensive study on different dielectric materials, as well as varying dielectric thickness tD and barrier thickness tB, is performed using capacitance-voltage analysis. It is revealed that the density of trapped electrons, ΔNit, scales with the dielectric capacitance under spill-over conditions, i.e., the accumulation of a second electron channel at the dielectric/AlGaN barrier interface. Hence, the density of trapped electrons is defined by the charging of the dielectric capacitance. The scaling behavior of ΔNit is explained universally by the density of accumulated electrons at the dielectric/III-N interface under spill-over conditions. We conclude that the overall density of interface defects is higher than what can be electrically measured, due to limits set by dielectric breakdown. These findings have a significant impact on the correct interpretation of threshold voltage drift data and are of relevance for the development of normally off and normally on III-N/GaN high electron mobility transistors with gate insulation.

Design and Development of Non-Contact Bio-Potential Electrodes for Pervasive Health Monitoring Applications.

PubMed

Portelli, Anthony J; Nasuto, Slawomir J

2017-01-01

For the advent of pervasive bio-potential monitoring, it will be necessary to utilize a combination of cheap, quick to apply, low-noise electrodes and compact electronics with wireless technologies. Once available, all electrical activity resulting from the processes of the human body could be actively and constantly monitored without the need for cumbersome application and maintenance. This could significantly improve the early diagnosis of a range of different conditions in high-risk individuals, opening the possibility for new treatments and interventions as conditions develop. This paper presents the design and implementation of compact, non-contact capacitive bio-potential electrodes utilising a low impedance current-to-voltage configuration and a bootstrapped voltage follower, demonstrating results applicable to research applications for capacitive electrocardiography and capacitive electromyography. The presented electrodes use few components, have a small surface area and are capable of acquiring a range of bio-potential signals.

Design and Development of Non-Contact Bio-Potential Electrodes for Pervasive Health Monitoring Applications

PubMed Central

Portelli, Anthony J.; Nasuto, Slawomir J.

2017-01-01

For the advent of pervasive bio-potential monitoring, it will be necessary to utilize a combination of cheap, quick to apply, low-noise electrodes and compact electronics with wireless technologies. Once available, all electrical activity resulting from the processes of the human body could be actively and constantly monitored without the need for cumbersome application and maintenance. This could significantly improve the early diagnosis of a range of different conditions in high-risk individuals, opening the possibility for new treatments and interventions as conditions develop. This paper presents the design and implementation of compact, non-contact capacitive bio-potential electrodes utilising a low impedance current-to-voltage configuration and a bootstrapped voltage follower, demonstrating results applicable to research applications for capacitive electrocardiography and capacitive electromyography. The presented electrodes use few components, have a small surface area and are capable of acquiring a range of bio-potential signals. PMID:28045439

Measuring charge nonuniformity in MOS devices

NASA Technical Reports Server (NTRS)

Maserjian, J.; Zamani, N.

1980-01-01

Convenient method of determining inherent lateral charge non-uniformities along silicon dioxide/silicon interface of metal-oxide-semiconductor (MOS) employs rapid measurement of capacitance of interface as function of voltage at liquid nitrogen temperature. Charge distribution is extracted by fast-Fourier-transform analysis of capacitance voltage (C-V) measurement.

All-solid-state asymmetric supercapacitors based on Fe-doped mesoporous Co3O4 and three-dimensional reduced graphene oxide electrodes with high energy and power densities.

PubMed

Zhang, Cheng; Wei, Jun; Chen, Leiyi; Tang, Shaolong; Deng, Mingsen; Du, Youwei

2017-10-19

An asymmetric supercapacitor offers opportunities to effectively utilize the full potential of the different potential windows of the two electrodes for a higher operating voltage, resulting in an enhanced specific capacitance and significantly improved energy without sacrificing the power delivery and cycle life. To achieve high energy and power densities, we have synthesized an all-solid-state asymmetric supercapacitor with a wider voltage range using Fe-doped Co 3 O 4 and three-dimensional reduced graphene oxide (3DrGO) as the positive and negative electrodes, respectively. In contrast to undoped Co 3 O 4 , the increased density of states and modified charge spatial separation endow the Fe-doped Co 3 O 4 electrode with greatly improved electrochemical capacitive performance, including high specific capacitance (1997 F g -1 and 1757 F g -1 at current densities of 1 and 20 A g -1 , respectively), excellent rate capability, and superior cycling stability. Remarkably, the optimized all-solid-state asymmetric supercapacitor can be cycled reversibly in a wide range of 0-1.8 V, thus delivering a high energy density (270.3 W h kg -1 ), high power density (9.0 kW kg -1 at 224.2 W h kg -1 ), and excellent cycling stability (91.8% capacitance retention after 10 000 charge-discharge cycles at a constant current density of 10 A g -1 ). The superior capacitive performance suggests that such an all-solid-state asymmetric supercapacitor shows great potential for developing energy storage systems with high levels of energy and power delivery.

Electric-Field Instrument With Ac-Biased Corona Point

NASA Technical Reports Server (NTRS)

Markson, R.; Anderson, B.; Govaert, J.

1993-01-01

Measurements indicative of incipient lightning yield additional information. New instrument gives reliable readings. High-voltage ac bias applied to needle point through high-resistance capacitance network provides corona discharge at all times, enabling more-slowly-varying component of electrostatic potential of needle to come to equilibrium with surrounding air. High resistance of high-voltage coupling makes instrument insensitive to wind. Improved corona-point instrument expected to yield additional information assisting in safety-oriented forecasting of lighting.

Energy-density enhancement of carbon-nanotube-based supercapacitors with redox couple in organic electrolyte.

PubMed

Park, Jinwoo; Kim, Byungwoo; Yoo, Young-Eun; Chung, Haegeun; Kim, Woong

2014-11-26

We demonstrate for the first time that the incorporation of a redox-active molecule in an organic electrolyte can increase the cell voltage of a supercapacitor. The redox molecule also contributes to increasing the cell capacitance by a faradaic redox reaction, and therefore the energy density of the supercapacitor can be significantly increased. More specifically, the addition of redox-active decamethylferrocene in an organic electrolyte results in an approximately 27-fold increase in the energy density of carbon-nanotube-based supercapacitors. The resulting high energy density (36.8 Wh/kg) stems from the increased cell voltage (1.1 V→2.1 V) and cell capacitance (8.3 F/g→61.3 F/g) resulting from decamethylferrocene addition. We found that the voltage increase is associated with the potential of the redox species relative to the electrochemical stability window of the supporting electrolyte. These results will be useful in identifying new electrolytes for high-energy-density supercapacitors.

Transfer printing of thermoreversible ion gels for flexible electronics.

PubMed

Lee, Keun Hyung; Zhang, Sipei; Gu, Yuanyan; Lodge, Timothy P; Frisbie, C Daniel

2013-10-09

Thermally assisted transfer printing was employed to pattern thin films of high capacitance ion gels on polyimide, poly(ethylene terephthalate), and SiO2 substrates. The ion gels consisted of 20 wt % block copolymer poly(styrene-b-ethylene oxide-b-styrene and 80 wt % ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)amide. Patterning resolution was on the order of 10 μm. Importantly, ion gels containing the block polymer with short PS end blocks (3.4 kg/mol) could be transfer-printed because of thermoreversible gelation that enabled intimate gel-substrate contact at 100 °C, while gels with long PS blocks (11 kg/mol) were not printable at the same temperature due to poor wetting contact between the gel and substrates. By using printed ion gels as high-capacitance gate insulators, electrolyte-gated thin-film transistors were fabricated that operated at low voltages (<1 V) with high on/off current ratios (∼10(5)). Statistical analysis of carrier mobility, turn-on voltage, and on/off ratio for an array of printed transistors demonstrated the excellent reproducibility of the printing technique. The results show that transfer printing is an attractive route to pattern high-capacitance ion gels for flexible thin-film devices.

Charge storage in β-FeSi2 nanoparticles

NASA Astrophysics Data System (ADS)

Theis, Jens; Bywalez, Robert; Küpper, Sebastian; Lorke, Axel; Wiggers, Hartmut

2015-02-01

We report on the observation of a surprisingly high specific capacitance of β-FeSi2 nanoparticle layers. Lateral, interdigitated capacitor structures were fabricated on thermally grown silicon dioxide and covered with β-FeSi2 particles by drop or spin casting. The β-FeSi2-nanoparticles, with crystallite sizes in the range of 10-30 nm, were fabricated by gas phase synthesis in a hot wall reactor. Compared to the bare electrodes, the nanoparticle-coated samples exhibit a 3-4 orders of magnitude increased capacitance. Time-resolved current voltage measurements show that for short times (seconds to minutes), the material is capable of storing up to 1 As/g at voltages of around 1 V. The devices are robust and exhibit long-term stability under ambient conditions. The specific capacitance is highest for a saturated relative humidity, while for a relative humidity below 40% the capacitance is almost indistinguishable from a nanoparticle-free reference sample. The devices work without the need of a fluid phase, the charge storing material is abundant and cost effective, and the sample design is easy to fabricate.

Hydrogenated TiO 2@reduced graphene oxide sandwich-like nanosheets for high voltage supercapacitor applications

DOE PAGES

Pham, Viet Hung; Nguyen-Phan, Thuy-Duong; Tong, Xiao; ...

2017-10-09

Hydrogenated TiO 2 has recently attracted considerable attention as potential electrode materials for supercapacitors due to its abundance, low cost, high conductivity, remarkable rate capability, and outstanding long-term cycling stability. In this paper, we demonstrate the synthesis of hydrogenated TiO 2 nanoparticles anchored on reduced graphene oxide nanosheets (HTG) in the form of sandwich-like nanosheet composites. Further, we explored their implementation as electrode materials for high voltage, symmetric supercapacitors, operating in the voltage window of 0–1.8 V. The HTGs were prepared by a sol-gel method, followed by hydrogenation in the temperature range 300–500 °C. Of the prepared composites, HTG preparedmore » at 400 °C exhibited the largest specific capacitance of 51 F g -1 at the current density of 1.0 A g -1 and excellent rate capability with 82.5% capacitance retention as the current density increased 40-fold, from 0.5 to 20.0 A g -1. HTG's excellent rate capability was attributed to its sandwich-like nanostructure, in which ultrasmall hydrogenated TiO 2 nanoparticles densely anchored onto both surfaces of the two-dimensional reduced graphene oxide sheets. Moreover, HTG-based supercapacitors also exhibited long-term cycling stability with the retention over 80% of its initial capacitance after 10,000 cycles. Finally, these properties suggest that HTG is a promising electrode material for the scalable manufacture of high-performance supercapacitors.« less

Hydrogenated TiO 2@reduced graphene oxide sandwich-like nanosheets for high voltage supercapacitor applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pham, Viet Hung; Nguyen-Phan, Thuy-Duong; Tong, Xiao

Hydrogenated TiO 2 has recently attracted considerable attention as potential electrode materials for supercapacitors due to its abundance, low cost, high conductivity, remarkable rate capability, and outstanding long-term cycling stability. In this paper, we demonstrate the synthesis of hydrogenated TiO 2 nanoparticles anchored on reduced graphene oxide nanosheets (HTG) in the form of sandwich-like nanosheet composites. Further, we explored their implementation as electrode materials for high voltage, symmetric supercapacitors, operating in the voltage window of 0–1.8 V. The HTGs were prepared by a sol-gel method, followed by hydrogenation in the temperature range 300–500 °C. Of the prepared composites, HTG preparedmore » at 400 °C exhibited the largest specific capacitance of 51 F g -1 at the current density of 1.0 A g -1 and excellent rate capability with 82.5% capacitance retention as the current density increased 40-fold, from 0.5 to 20.0 A g -1. HTG's excellent rate capability was attributed to its sandwich-like nanostructure, in which ultrasmall hydrogenated TiO 2 nanoparticles densely anchored onto both surfaces of the two-dimensional reduced graphene oxide sheets. Moreover, HTG-based supercapacitors also exhibited long-term cycling stability with the retention over 80% of its initial capacitance after 10,000 cycles. Finally, these properties suggest that HTG is a promising electrode material for the scalable manufacture of high-performance supercapacitors.« less

High voltage pulse conditioning

DOEpatents

Springfield, Ray M.; Wheat, Jr., Robert M.

1990-01-01

Apparatus for conditioning high voltage pulses from particle accelerators in order to shorten the rise times of the pulses. Flashover switches in the cathode stalk of the transmission line hold off conduction for a determinable period of time, reflecting the early portion of the pulses. Diodes upstream of the switches divert energy into the magnetic and electrostatic storage of the capacitance and inductance inherent to the transmission line until the switches close.

Decorating Graphene Oxide with Ionic Liquid Nanodroplets: An Approach Leading to Energy-Dense, High-Voltage Supercapacitors.

PubMed

She, Zimin; Ghosh, Debasis; Pope, Michael A

2017-10-24

A major stumbling block in the development of high energy density graphene-based supercapacitors has been maintaining high ion-accessible surface area combined with high electrode density. Herein, we develop an ionic liquid (IL)-surfactant microemulsion system that is found to facilitate the spontaneous adsorption of IL-filled micelles onto graphene oxide (GO). This adsorption distributes the IL over all available surface area and provides an aqueous formulation that can be slurry cast onto current collectors, leaving behind a dense nanocomposite film of GO/IL/surfactant. By removing the surfactant and reducing the GO through a low-temperature (360 °C) heat treatment, the IL plays a dual role of spacer and electrolyte. We study the effect of IL content and operating temperature on the performance, demonstrating a record high gravimetric capacitance (302 F/g at 1 A/g) for 80 wt % IL composites. At 60 wt % IL, combined high capacitance and bulk density (0.76 g/cm 3 ), yields one of the highest volumetric capacitances (218 F/cm 3 , at 1 A/g) ever reported for a high-voltage IL-based supercapacitor. While achieving promising rate performance and cycle-life, the approach also eliminates the long and costly electrolyte imbibition step of cell assembly as the electrolyte is cast directly with the electrode material.

Aging and failure mode of electrochemical double layer capacitors during accelerated constant load tests

NASA Astrophysics Data System (ADS)

Kötz, R.; Ruch, P. W.; Cericola, D.

Electrochemical double layer capacitors of the BCAP0350 type (Maxwell Technologies) were tested under constant load conditions at different voltages and temperatures. The aging of the capacitors was monitored during the test in terms of capacitance, internal resistance and leakage current. Aging was significantly accelerated by elevated temperature or increased voltage. Only for extreme conditions at voltages of 3.5 V or temperatures above 70 °C the capacitors failed due to internal pressure build-up. No other failure events such as open circuit or short circuit were detected. Impedance measurements after the tests showed increased high frequency resistance, an increased distributed resistance and most likely an increase in contact resistance between electrode and current collector together with a loss of capacitance. Capacitors aged at elevated voltages (3.3 V) exhibited a tilting of the low frequency component, which implies an increase in the heterogeneity of the electrode surface. This feature was not observed upon aging at elevated temperatures (70 °C).

Study on photoelectric parameter measurement method of high capacitance solar cell

NASA Astrophysics Data System (ADS)

Zhang, Junchao; Xiong, Limin; Meng, Haifeng; He, Yingwei; Cai, Chuan; Zhang, Bifeng; Li, Xiaohui; Wang, Changshi

2018-01-01

The high efficiency solar cells usually have high capacitance characteristic, so the measurement of their photoelectric performance usually requires long pulse width and long sweep time. The effects of irradiance non-uniformity, probe shielding and spectral mismatch on the IV curve measurement are analyzed experimentally. A compensation method for irradiance loss caused by probe shielding is proposed, and the accurate measurement of the irradiance intensity in the IV curve measurement process of solar cell is realized. Based on the characteristics that the open circuit voltage of solar cell is sensitive to the junction temperature, an accurate measurement method of the temperature of solar cell under continuous irradiation condition is proposed. Finally, a measurement method with the characteristic of high accuracy and wide application range for high capacitance solar cell is presented.

Dynamic characteristics of organic bulk-heterojunction solar cells

NASA Astrophysics Data System (ADS)

Babenko, S. D.; Balakai, A. A.; Moskvin, Yu. L.; Simbirtseva, G. V.; Troshin, P. A.

2010-12-01

Transient characteristics of organic bulk-heterojunction solar cells have been studied using pulsed laser probing. An analysis of the photoresponse waveforms of a typical solar cell measured by varying load resistance within broad range at different values of the bias voltage provided detailed information on the photocell parameters that characterize electron-transport properties of active layers. It is established that the charge carrier mobility is sufficient to ensure high values of the fill factor (˜0.6) in the obtained photocells. On approaching the no-load voltage, the differential capacitance of the photocell exhibits a sixfold increase as compared to the geometric capacitance. A possible mechanism of recombination losses in the active medium is proposed.

Strategies for dynamic soft-landing in capacitive microelectromechanical switches

NASA Astrophysics Data System (ADS)

Jain, Ankit; Nair, Pradeep R.; Alam, Muhammad A.

2011-06-01

Electromechanical dielectric degradation associated with the hard landing of movable electrode is a technology-inhibiting reliability concern for capacitive RF-MEMS switches. In this letter, we propose two schemes for dynamic soft-landing that obviate the need for external feedback circuitry. Instead, the proposed resistive and capacitive braking schemes can reduce impact velocity significantly without compromising other performance characteristics like pull-in voltage and pull-in time. Resistive braking is achieved by inserting a resistance in series with the voltage source whereas capacitive braking requires patterning of the electrode or the dielectric. Our results have important implications to the design and optimization of reliability aware electrostatically actuated MEMS switches.

MIS capacitor studies on silicon carbide single crystals

NASA Technical Reports Server (NTRS)

Kopanski, J. J.

1990-01-01

Cubic SIC metal-insulator-semiconductor (MIS) capacitors with thermally grown or chemical-vapor-deposited (CVD) insulators were characterized by capacitance-voltage (C-V), conductance-voltage (G-V), and current-voltage (I-V) measurements. The purpose of these measurements was to determine the four charge densities commonly present in an MIS capacitor (oxide fixed charge, N(f); interface trap level density, D(it); oxide trapped charge, N(ot); and mobile ionic charge, N(m)) and to determine the stability of the device properties with electric-field stress and temperature. The section headings in the report include the following: Capacitance-voltage and conductance-voltage measurements; Current-voltage measurements; Deep-level transient spectroscopy; and Conclusions (Electrical characteristics of SiC MIS capacitors).

An earth-isolated optically coupled wideband high voltage probe powered by ambient light.

PubMed

Zhai, Xiang; Bellan, Paul M

2012-10-01

An earth-isolated optically-coupled wideband high voltage probe has been developed for pulsed power applications. The probe uses a capacitive voltage divider coupled to a fast light-emitting diode that converts high voltage into an amplitude-modulated optical signal, which is then conveyed to a receiver via an optical fiber. A solar cell array, powered by ambient laboratory lighting, charges a capacitor that, when triggered, acts as a short-duration power supply for an on-board amplifier in the probe. The entire system has a noise level ≤0.03 kV, a DC-5 MHz bandwidth, and a measurement range from -6 to 2 kV; this range can be conveniently adjusted.

A mixed solution-processed gate dielectric for zinc-tin oxide thin-film transistor and its MIS capacitance

NASA Astrophysics Data System (ADS)

Kim, Hunho; Kwack, Young-Jin; Yun, Eui-Jung; Choi, Woon-Seop

2016-09-01

Solution-processed gate dielectrics were fabricated with the combined ZrO2 and Al2O3 (ZAO) in the form of mixed and stacked types for oxide thin film transistors (TFTs). ZAO thin films prepared with double coatings for solid gate dielectrics were characterized by analytical tools. For the first time, the capacitance of the oxide semiconductor was extracted from the capacitance-voltage properties of the zinc-tin oxide (ZTO) TFTs with the combined ZAO dielectrics by using the proposed metal-insulator-semiconductor (MIS) structure model. The capacitance evolution of the semiconductor from the TFT model structure described well the threshold voltage shift observed in the ZTO TFT with the ZAO (1:2) gate dielectric. The electrical properties of the ZTO TFT with a ZAO (1:2) gate dielectric showed low voltage driving with a field effect mobility of 37.01 cm2/Vs, a threshold voltage of 2.00 V, an on-to-off current ratio of 1.46 × 105, and a subthreshold slope of 0.10 V/dec.

A mixed solution-processed gate dielectric for zinc-tin oxide thin-film transistor and its MIS capacitance

PubMed Central

Kim, Hunho; Kwack, Young-Jin; Yun, Eui-Jung; Choi, Woon-Seop

2016-01-01

Solution-processed gate dielectrics were fabricated with the combined ZrO2 and Al2O3 (ZAO) in the form of mixed and stacked types for oxide thin film transistors (TFTs). ZAO thin films prepared with double coatings for solid gate dielectrics were characterized by analytical tools. For the first time, the capacitance of the oxide semiconductor was extracted from the capacitance-voltage properties of the zinc-tin oxide (ZTO) TFTs with the combined ZAO dielectrics by using the proposed metal-insulator-semiconductor (MIS) structure model. The capacitance evolution of the semiconductor from the TFT model structure described well the threshold voltage shift observed in the ZTO TFT with the ZAO (1:2) gate dielectric. The electrical properties of the ZTO TFT with a ZAO (1:2) gate dielectric showed low voltage driving with a field effect mobility of 37.01 cm2/Vs, a threshold voltage of 2.00 V, an on-to-off current ratio of 1.46 × 105, and a subthreshold slope of 0.10 V/dec. PMID:27641430

RF current sensor

DOEpatents

Moore, James A.; Sparks, Dennis O.

1998-11-10

An RF sensor having a novel current sensing probe and a voltage sensing probe to measure voltage and current. The current sensor is disposed in a transmission line to link all of the flux generated by the flowing current in order to obtain an accurate measurement. The voltage sensor is a flat plate which operates as a capacitive plate to sense voltage on a center conductor of the transmission line, in which the measured voltage is obtained across a resistance leg of a R-C differentiator circuit formed by the characteristic impedance of a connecting transmission line and a capacitance of the plate, which is positioned proximal to the center conductor.

Carrier transport and collection in fully depleted semiconductors by a combined action of the space charge field and the field due to electrode voltages

DOEpatents

Rehak, P.; Gatti, E.

1984-02-24

A semiconductor charge transport device and method for making same, characterized by providing a thin semiconductor wafer having rectifying functions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution.

Carrier transport and collection in fully depleted semiconductors by a combined action of the space charge field and the field due to electrode voltages

DOEpatents

Rehak, Pavel; Gatti, Emilio

1987-01-01

A semiconductor charge transport device and method for making same, characterized by providing a thin semiconductor wafer having rectifying junctions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution.

Carrier transport and collection in fully depleted semiconductors by a combined action of the space charge field and the field due to electrode voltages

DOEpatents

Rehak, P.; Gatti, E.

1987-08-18

A semiconductor charge transport device and method for making same are disclosed, characterized by providing a thin semiconductor wafer having rectifying junctions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution. 16 figs.

Development of high energy density electrical double layer capacitors

NASA Astrophysics Data System (ADS)

Devarajan, Thamarai selvi

Electrochemical Double Layer capacitors (EDLCs) have shown themselves as a viable energy storage alternative. EDLCs have high power density, faster charge/discharge, wide operating temperature and long cycle life compared to batteries since it stores charge by physical separation. Despites all their advantages, their low energy density stand as a bottleneck for capacitors. This research aims to increase the energy density of EDLC without compromising the power density. Energy is proportional to the square of cell voltage. Cell voltage is mainly dependent on electrolyte breakdown. Electrolytes also provide ions for charge separation and conduction. Therefore various electrolytes (Solutes and Solvents) which can give high concentration, solubility and decomposition potential were characterized in the first part of the research. In that study, a novel ionic liquid OPBF4 had higher capacitance and comparable voltage window compared to commercial TEABF4 in Acetonitrile. However, the increased polarity of the fixed ring O-atom and the ion-ion interaction in OPBF4 was responsible for lowering its conductivity. Oxygenated ionic compounds with alkyl groups had lower stability due to beta elimination between two electron withdrawing atoms. Volume based thermodynamics and quantum chemical calculations were used to calculate ion size, HOMO/LUMO energies, and free energy changes and establish relationship with capacitance, redox potential and melting points respectively. In addition free energy of fusion was used to predict the melting point. Ion size had correlation with capacitance due to compact double layer formation. Free energy changes did not explain the differences in melting point and predicted dielectric constant was inconsistent with the polarity. This is presumably due to using Van der Waals volume instead of crystal structure volume and insufficient incorporation of polarization term. The HOMO/LUMO energies gave direct relation between oxidation and reduction potential at 1mA/cm 2. A brief study on non-polar co-solvents for EDLC was studied. Among the solvents studied, fluorinated solvents had low melting point and viscosity due to incorporation of asymmetry. However, because of low dielectric constant, TEABF4 is insoluble and had to be mixed with other solvents. The mixed fluorinated solvents had slightly higher voltage window due to decreased donicity of lone pairs of electrons. The second approach to increasing energy density is to increase capacitance. Capacitance is mainly dependent on surface area and porosity of electrodes. Nanostructured materials which can offer multiple charge storage are currently of interest. Hence, novel NiSi nanotubes were studied as electrodes for supercapacitor applications. Silicon material has high capacity and these inert electrodes can enable higher capacitance by controlling the porosity and functional groups in specific electrolytes. The Silicon wafers were made porous by anodization using hydrofluoric acid. In order to improve the conductivity, the porous silicon was doped, then plated with Ni using electroless plating method and annealed to form nickel mono silicide. Gold was deposited on the back side of the electrode to enhance conductivity. Our porous NiSi electrodes gave capacitance of about 1185muF /cm2 in 0.5 M H 2SO4. Further investigation of oxide formation and modification of functional groups will help achieve higher capacitance.

Capacitive Behavior of Single Gallium Oxide Nanobelt

PubMed Central

Cai, Haitao; Liu, Hang; Zhu, Huichao; Shao, Pai; Hou, Changmin

2015-01-01

In this research, monocrystalline gallium oxide (Ga2O3) nanobelts were synthesized through oxidation of metal gallium at high temperature. An electronic device, based on an individual Ga2O3 nanobelt on Pt interdigital electrodes (IDEs), was fabricated to investigate the electrical characteristics of the Ga2O3 nanobelt in a dry atmosphere at room temperature. The current-voltage (I-V) and I/V-t characteristics show the capacitive behavior of the Ga2O3 nanobelt, indicating the existence of capacitive elements in the Pt/Ga2O3/Pt structure. PMID:28793506

The passive cable properties of hair cell stereocilia and their contribution to somatic capacitance measurements.

PubMed

Breneman, Kathryn D; Highstein, Stephen M; Boyle, Richard D; Rabbitt, Richard D

2009-01-01

Somatic measurements of whole-cell capacitance are routinely used to understand physiologic events occurring in remote portions of cells. These studies often assume the intracellular space is voltage-clamped. We questioned this assumption in auditory and vestibular hair cells with respect to their stereocilia based on earlier studies showing that neurons, with radial dimensions similar to stereocilia, are not always isopotential under voltage-clamp. To explore this, we modeled the stereocilia as passive cables with transduction channels located at their tips. We found that the input capacitance measured at the soma changes when the transduction channels at the tips of the stereocilia are open compared to when the channels are closed. The maximum capacitance is felt with the transducer closed but will decrease as the transducer opens due to a length-dependent voltage drop along the stereocilium length. This potential drop is proportional to the intracellular resistance and stereocilium tip conductance and can produce a maximum capacitance error on the order of fF for single stereocilia and pF for the bundle.

Capacitance of the Double Layer Formed at the Metal/Ionic-Conductor Interface: How Large Can It Be?

NASA Astrophysics Data System (ADS)

Skinner, Brian; Loth, M. S.; Shklovskii, B. I.

2010-03-01

The capacitance of the double layer formed at a metal/ionic-conductor interface can be remarkably large, so that the apparent width of the double layer is as small as 0.3 Å. Mean-field theories fail to explain such large capacitance. We propose an alternate theory of the ionic double layer which allows for the binding of discrete ions to their image charges in the metal. We show that at small voltages the capacitance of the double layer is limited only by the weak dipole-dipole repulsion between bound ions, and is therefore very large. At large voltages the depletion of bound ions from one of the capacitor electrodes triggers a collapse of the capacitance to the mean-field value.

Equilibrium charge fluctuations of a charge detector and its effect on a nearby quantum dot

NASA Astrophysics Data System (ADS)

Ruiz-Tijerina, David; Vernek, Edson; Ulloa, Sergio

2014-03-01

We study the Kondo state of a spin-1/2 quantum dot (QD), in close proximity to a quantum point contact (QPC) charge detector near the conductance regime of the 0.7 anomaly. The electrostatic coupling between the QD and QPC introduces a remote gate on the QD level, which varies with the QPC gate voltage. Furthermore, models for the 0.7 anomaly [Y. Meir et al., PRL 89,196802(2002)] suggest that the QPC lodges a Kondo-screened level with charge-correlated hybridization, which may be also affected by capacitive coupling to the QD, giving rise to a competition between the two Kondo ground states. We model the QD-QPC system as two capacitively-coupled Kondo impurities, and explore the zero-bias transport of both the QD and the QPC for different local gate voltages and coupling strengths, using the numerical renormalization group and variational methods. We find that the capacitive coupling produces a remote gating effect, non-monotonic in the gate voltages, which reduces the gate voltage window for Kondo screening in either impurity, and which can also drive a quantum phase transition out of the Kondo regime. Our study is carried out for intermediate coupling strengths, and as such is highly relevant to experiments; particularly, to recent studies of decoherence effects on QDs. Supported by MWN/CIAM and NSF PIRE.

From MEMRISTOR to MEMImpedance device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wakrim, T.; Univ. Grenoble Alpes, G2Elab, F-38000 Grenoble; Vallée, C., E-mail: christophe.vallee@cea.fr

2016-02-01

The behavior of the capacitance switching of HfO{sub 2} Resistive non-volatile Memories is investigated in view of realizing a MEMImpedance (MEM-Z) device. In such a Metal Insulator Metal structure, the impedance value can be tuned by the adjustment of both resistance and capacitance values. We observe a strong variation of capacitance from positive to negative values in a single layer Metal Insulator Metal device made of HfO{sub 2} deposited by Atomic Layer Deposition, but unfortunately no memory effect is observed. However, in the case of a two layer structure, a device has been obtained with a memory effect where bothmore » resistance and capacitance values can be tuned simultaneously, with a variation of capacitance down to negative values to get an inductive behavior. Negative capacitance values are observed for voltage values near SET voltage. A schematic model based on shaped oxygen vacancy density is proposed to account for this capacitance variation. The oxygen vacancies can be either isolated or connected in the bulk of the oxide.« less

Understanding Mott-Schottky Measurements under Illumination in Organic Bulk Heterojunction Solar Cells

NASA Astrophysics Data System (ADS)

Zonno, Irene; Martinez-Otero, Alberto; Hebig, Jan-Christoph; Kirchartz, Thomas

2017-03-01

The Mott-Schottky analysis in the dark is a frequently used method to determine the doping concentration of semiconductors from capacitance-voltage measurements, even for such complex systems as polymer:fullerene blends used for organic solar cells. While the analysis of capacitance-voltage measurements in the dark is relatively well established, the analysis of data taken under illumination is currently not fully understood. Here, we present experiments and simulations to show which physical mechanisms affect the Mott-Schottky analysis under illumination. We show that the mobility of the blend has a major influence on the shape of the capacitance-voltage curve and can be obtained from data taken under reverse bias. In addition, we show that the apparent shift of the built-in voltage observed previously can be explained by a shift of the onset of space-charge-limited collection with illumination intensity.

Superlattice barrier varactors

NASA Technical Reports Server (NTRS)

Raman, C.; Sun, J. P.; Chen, W. L.; Munns, G.; East, J.; Haddad, G.

1992-01-01

SBV (Single Barrier Varactor) diodes have been proposed as alternatives to Schottky barrier diodes for harmonic multiplier applications. However, these show a higher current than expected. The excess current is due to X valley transport in the barrier. We present experimental results showing that the use of a superlattice barrier and doping spikes in the GaAs depletion regions on either side of the barrier can reduce the excess current and improve the control of the capacitance vs. voltage characteristic. The experimental results consist of data taken from two types of device structures. The first test structure was used to study the performance of AlAs/GaAs superlattice barriers. The wafer was fabricated into 90 micron diameter mesa diodes and the resulting current vs. voltage characteristics were measured. A 10 period superlattice structure with a total thickness of approximately 400 A worked well as an electron barrier. The structure had a current density of about one A/sq cm at one volt at room temperature. The capacitance variation of these structures was small because of the design of the GaAs cladding layers. The second test structure was used to study cladding layer designs. These wafers were InGaAs and InAlAs layers lattice matched to an InP substrate. The layers have n(+) doping spikes near the barrier to increase the zero bias capacitance and control the shape of the capacitance vs. voltage characteristic. These structures have a capacitance ratio of 5:1 and an abrupt change from maximum to minimum capacitance. The measurements were made at 80 K. Based on the information obtained from these two structures, we have designed a structure that combines the low current density barrier with the improved cladding layers. The capacitance and current-voltage characteristics from this structure are presented.

Programmable Low-Power Low-Noise Capacitance to Voltage Converter for MEMS Accelerometers

PubMed Central

Royo, Guillermo; Sánchez-Azqueta, Carlos; Gimeno, Cecilia; Aldea, Concepción; Celma, Santiago

2016-01-01

In this work, we present a capacitance-to-voltage converter (CVC) for capacitive accelerometers based on microelectromechanical systems (MEMS). Based on a fully-differential transimpedance amplifier (TIA), it features a 34-dB transimpedance gain control and over one decade programmable bandwidth, from 75 kHz to 1.2 MHz. The TIA is aimed for low-cost low-power capacitive sensor applications. It has been designed in a standard 0.18-μm CMOS technology and its power consumption is only 54 μW. At the maximum transimpedance configuration, the TIA shows an equivalent input noise of 42 fA/Hz at 50 kHz, which corresponds to 100 μg/Hz. PMID:28042830

Programmable Low-Power Low-Noise Capacitance to Voltage Converter for MEMS Accelerometers.

PubMed

Royo, Guillermo; Sánchez-Azqueta, Carlos; Gimeno, Cecilia; Aldea, Concepción; Celma, Santiago

2016-12-30

In this work, we present a capacitance-to-voltage converter (CVC) for capacitive accelerometers based on microelectromechanical systems (MEMS). Based on a fully-differential transimpedance amplifier (TIA), it features a 34-dB transimpedance gain control and over one decade programmable bandwidth, from 75 kHz to 1.2 MHz. The TIA is aimed for low-cost low-power capacitive sensor applications. It has been designed in a standard 0.18-μm CMOS technology and its power consumption is only 54 μW. At the maximum transimpedance configuration, the TIA shows an equivalent input noise of 42 fA/ Hz at 50 kHz, which corresponds to 100 μg/ Hz .

In Situ High-Level Nitrogen Doping into Carbon Nanospheres and Boosting of Capacitive Charge Storage in Both Anode and Cathode for a High-Energy 4.5 V Full-Carbon Lithium-Ion Capacitor.

PubMed

Sun, Fei; Liu, Xiaoyan; Wu, Hao Bin; Wang, Lijie; Gao, Jihui; Li, Hexing; Lu, Yunfeng

2018-05-02

To circumvent the imbalances of electrochemical kinetics and capacity between Li + storage anodes and capacitive cathodes for lithium-ion capacitors (LICs), we herein demonstrate an efficient solution by boosting the capacitive charge-storage contributions of carbon electrodes to construct a high-performance LIC. Such a strategy is achieved by the in situ and high-level doping of nitrogen atoms into carbon nanospheres (ANCS), which increases the carbon defects and active sites, inducing more rapidly capacitive charge-storage contributions for both Li + storage anodes and PF 6 - storage cathodes. High-level nitrogen-doping-induced capacitive enhancement is successfully evidenced by the construction of a symmetric supercapacitor using commercial organic electrolytes. Coupling a pre-lithiated ANCS anode with a fresh ANCS cathode enables a full-carbon LIC with a high operating voltage of 4.5 V and high energy and power densities thereof. The assembled LIC device delivers high energy densities of 206.7 and 115.4 Wh kg -1 at power densities of 0.225 and 22.5 kW kg -1 , respectively, as well as an unprecedented high-power cycling stability with only 0.0013% capacitance decay per cycle within 10 000 cycles at a high power output of 9 kW kg -1 .

Role of Copper in the Performance of CdS/CdTe Solar Cells (Poster)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demtsu, S.; Albin, D.; Sites, J.

2006-05-01

The performance of CdS/CdTe solar cells made with evaporated Cu as a primary back contact was studied through current-voltage (JV) at different intensities, quantum efficiency (QE) under light and voltage bias, capacitance-voltage (CV), and drive-level capacitance profiling (DLCP) measurements. The results show that while modest amounts of Cu enhance cell performance, excessive amounts degrade device quality and reduce performance. The analysis is supported with numerical simulations to reproduce and explain some of the experimental results.

A zero-voltage-switched three-phase interleaved buck converter

NASA Astrophysics Data System (ADS)

Hsieh, Yao-Ching; Huang, Bing-Siang; Lin, Jing-Yuan; Pham, Phu Hieu; Chen, Po-Hao; Chiu, Huang-Jen

2018-04-01

This paper proposes a three-phase interleaved buck converter which is composed of three identical paralleled buck converters. The proposed solution has three shunt inductors connected between each other of three basic buck conversion units. With the help of the shunt inductors, the MOSFET parasitic capacitances will resonate to achieve zero-voltage-switching. Furthermore, the decreasing rate of the current through the free-wheeling diodes is limited, and therefore, their reverse-recovery losses can be minimised. The active power switches are controlled by interleaved pulse-width modulation signals to reduce the input and output current ripples. Therefore, the filtering capacitances on the input and output sides can be reduced. The power efficiency is measured to be as high as 98% in experiment with a prototype circuit.

High voltage electrochemical double layer capacitors using conductive carbons as additives

NASA Astrophysics Data System (ADS)

Michael, M. S.; Prabaharan, S. R. S.

We describe here an interesting approach towards electrochemical capacitors (ECCs) using graphite materials (as being used as conductive additives in rechargeable lithium-ion battery cathodes) in a Li + containing organic electrolyte. The important result is that we achieved a voltage window of >4 V, which is rather large, compared to the standard window of 2.5 V for ordinary electric double layer capacitors (DLCs). The capacitor performance was evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge techniques. From charge-discharge studies of the symmetrical device (for instance, SFG6 carbon electrode), a specific capacitance of up to 14.5 F/g was obtained at 16 mA/cm 2 current rate and at a low current rate (3 mA/cm 2), a higher value was obtained (63 F/g). The specific capacitance decreased about 25% after 1000 cycles compared to the initial discharge process. The performances of these graphites are discussed in the light of both double layer capacitance (DLC) and pseudocapacitance (battery-like behavior). The high capacitance obtained was not only derived from the current-transient capacitive behavior but is also attributed to pseudocapacitance associated with some kind of faradaic reaction, which could probably occur due to Li + intercalation/deintercalation reactions into graphitic layers of the carbons used. The ac impedance (electrochemical impedances spectroscopy, EIS) measurements were also carried out to evaluate the capacitor parameters such as equivalent series resistance (ESR) and frequency dependent capacitance ( Cfreq). Cyclic voltammetry measurements were also performed to evaluate the cycling behavior of the carbon electrodes and the non-rectangular shaped voltammograms revealed the non-zero time constant [ τ( RC)≠0] confirming that the current contains a transient as well as steady-state components.

Opening of K+ channels by capacitive stimulation from silicon chip

NASA Astrophysics Data System (ADS)

Ulbrich, M. H.; Fromherz, P.

2005-10-01

The development of stable neuroelectronic systems requires a stimulation of nerve cells from semiconductor devices without electrochemical effects at the electrolyte/solid interface and without damage of the cell membrane. The interaction must rely on a reversible opening of voltage-gated ion channels by capacitive coupling. In a proof-of-principle experiment, we demonstrate that Kv1.3 potassium channels expressed in HEK293 cells can be opened from an electrolyte/oxide/silicon (EOS) capacitor. A sufficient strength of electrical coupling is achieved by insulating silicon with a thin film of TiO2 to achieve a high capacitance and by removing NaCl from the electrolyte to enhance the resistance of the cell-chip contact. When a decaying voltage ramp is applied to the EOS capacitor, an outward current through the attached cell membrane is observed that is specific for Kv1.3 channels. An open probability up to fifty percent is estimated by comparison with a numerical simulation of the cell-chip contact.

Low-Temperature Scanning Capacitance Probe for Imaging Electron Motion

NASA Astrophysics Data System (ADS)

Bhandari, S.; Westervelt, R. M.

2014-12-01

Novel techniques to probe electronic properties at the nanoscale can shed light on the physics of nanoscale devices. In particular, studying the scattering of electrons from edges and apertures at the nanoscale and imaging the electron profile in a quantum dot, have been of interest [1]. In this paper, we present the design and implementation of a cooled scanning capacitance probe that operates at liquid He temperatures to image electron waves in nanodevices. The conducting tip of a scanned probe microscope is held above the nanoscale structure, and an applied sample-to-tip voltage creates an image charge that is measured by a cooled charge amplifier [2] adjacent to the tip. The circuit is based on a low-capacitance, high- electron-mobility transistor (Fujitsu FHX35X). The input is a capacitance bridge formed by a low capacitance pinched-off HEMT transistor and tip-sample capacitance. We have achieved low noise level (0.13 e/VHz) and high spatial resolution (100 nm) for this technique, which promises to be a useful tool to study electronic behavior in nanoscale devices.

Electrochemical capacitance modulation in an interacting mesoscopic capacitor induced by internal charge transfer

NASA Astrophysics Data System (ADS)

Liu, Wei; He, Jianhong; Guo, Huazhong; Gao, Jie

2018-04-01

We report experiments on the dynamic response of an interacting mesoscopic capacitor consisting of a quantum dot with two confined spin-split levels of the lowest Landau level. In high magnetic fields, states inside the dot are regulated by a mixture of Coulomb interaction and Landau-level quantization, and electrons distribute on two spatially separated regions. Quantum point contact voltage and magnetic field are employed to manipulate the number and distribution of electrons inside the quantum dot. We find that the periodicity of the electrochemical capacitance oscillations is dominated by the charging energy, and their amplitudes, due to internal charge transfer and strong internal capacitive coupling, show rich variations of modulations. Magnetocapacitance displays a sawtoothlike manner and may differ in tooth directions for different voltages, which, we demonstrate, result from a sawtoothlike electrochemical potential change induced by internal charge transfer and field-sensitive electrostatic potential. We further build a charge stability diagram, which, together with all other capacitance properties, is consistently interpreted in terms of a double-dot model. The demonstrated technique is of interest as a tool for fast and sensitive charge state readout of a double-quantum-dot qubit in the gigahertz frequency quantum electronics.

Electrical characteristics of pentacene-based Schottky diodes

NASA Astrophysics Data System (ADS)

Lee, Y. S.; Park, J. H.; Choi, J. S.

2003-01-01

The current-voltage ( I-V), capacitance-frequency ( C-f), and capacitance-voltage ( C-V) characteristics of organic diodes with a pentacene/aluminum Sckottky contact have been investigated. From the measured diode capacitances, it is revealed that the frequency-dependent properties are related to the localized traps in the band gap of pentacene. The C-V characteristics for different test frequencies are presented. In the low frequency region, the capacitance is nearly constant with reverse bias and increase with the forward bias. With even higher forward bias, the capacitance gradually decreases, which is due to the detrapping of the trapped charges. The intrinsic charge carrier concentration in pentacene was extracted as 3.1×10 17 cm -3 from the C-V characteristics. The C-V properties of the pentacene-based metal-oxide-semiconductor structure have also studied.

Mapping Capacitive Coupling Among Pixels in a Sensor Array

NASA Technical Reports Server (NTRS)

Seshadri, Suresh; Cole, David M.; Smith, Roger M.

2010-01-01

An improved method of mapping the capacitive contribution to cross-talk among pixels in an imaging array of sensors (typically, an imaging photodetector array) has been devised for use in calibrating and/or characterizing such an array. The method involves a sequence of resets of subarrays of pixels to specified voltages and measurement of the voltage responses of neighboring non-reset pixels.

Experimental study of a variable-capacitance micromotor with electrostatic suspension

NASA Astrophysics Data System (ADS)

Han, F. T.; Wu, Q. P.; Wang, L.

2010-11-01

A variable-capacitance micromotor where the rotor is supported electrostatically in five degrees of freedom was designed, fabricated and tested in order to study the behavior of this electrostatic motor. The micromachined device is based on a glass/silicon/glass stack bonding structure, fabricated by bulk micromachining and initially operated in atmospheric environment. The analytical torque model is obtained by calculating the capacitances between different stator electrodes and the rotor. Capacitance values in the order of 10-13 pF and torque values in the order of 10-10 N m have been calculated from the motor geometry and attainable drive voltage. A dynamic model of the motor is proposed by further estimating the air-film damping effect in an effort to explain the experimental rotation measurements. Experimental results of starting voltage, continuous operation, switching response and electric bearing of the micromotor are presented and discussed. Preliminary measurements indicate that a rotor rotating speed of 73.3 r min-1 can be achieved at a drive voltage of 28.3 V, equivalent to a theoretical motive torque of 517 pN m. Starting voltage results obtained from experimental measurement are in agreement with the developed dynamic model.

A Charge-Based Low-Power High-SNR Capacitive Sensing Interface Circuit

PubMed Central

Peng, Sheng-Yu; Qureshi, Muhammad S.; Hasler, Paul E.; Basu, Arindam; Degertekin, F. L.

2008-01-01

This paper describes a low-power approach to capacitive sensing that achieves a high signal-to-noise ratio. The circuit is composed of a capacitive feedback charge amplifier and a charge adaptation circuit. Without the adaptation circuit, the charge amplifier only consumes 1 μW to achieve the audio band SNR of 69.34dB. An adaptation scheme using Fowler-Nordheim tunneling and channel hot electron injection mechanisms to stabilize the DC output voltage is demonstrated. This scheme provides a very low frequency pole at 0.2Hz. The measured noise spectrums show that this slow-time scale adaptation does not degrade the circuit performance. The DC path can also be provided by a large feedback resistance without causing extra power consumption. A charge amplifier with a MOS-bipolar pseudo-resistor feedback scheme is interfaced with a capacitive micromachined ultrasonic transducer to demonstrate the feasibility of this approach for ultrasound applications. PMID:18787650

Design and standalone characterisation of a capacitively coupled HV-CMOS sensor chip for the CLIC vertex detector

NASA Astrophysics Data System (ADS)

Kremastiotis, I.; Ballabriga, R.; Campbell, M.; Dannheim, D.; Fiergolski, A.; Hynds, D.; Kulis, S.; Peric, I.

2017-09-01

The concept of capacitive coupling between sensors and readout chips is under study for the vertex detector at the proposed high-energy CLIC electron positron collider. The CLICpix Capacitively Coupled Pixel Detector (C3PD) is an active High-Voltage CMOS sensor, designed to be capacitively coupled to the CLICpix2 readout chip. The chip is implemented in a commercial 180 nm HV-CMOS process and contains a matrix of 128×128 square pixels with 25μm pitch. First prototypes have been produced with a standard resistivity of ~20 Ωcm for the substrate and tested in standalone mode. The results show a rise time of ~20 ns, charge gain of 190 mV/ke- and ~40 e- RMS noise for a power consumption of 4.8μW/pixel. The main design aspects, as well as standalone measurement results, are presented.

Cell voltage versus electrode potential range in aqueous supercapacitors

PubMed Central

Dai, Zengxin; Peng, Chuang; Chae, Jung Hoon; Ng, Kok Chiang; Chen, George Z.

2015-01-01

Supercapacitors with aqueous electrolytes and nanostructured composite electrodes are attractive because of their high charging-discharging speed, long cycle life, low environmental impact and wide commercial affordability. However, the energy capacity of aqueous supercapacitors is limited by the electrochemical window of water. In this paper, a recently reported engineering strategy is further developed and demonstrated to correlate the maximum charging voltage of a supercapacitor with the capacitive potential ranges and the capacitance ratio of the two electrodes. Beyond the maximum charging voltage, a supercapacitor may still operate, but at the expense of a reduced cycle life. In addition, it is shown that the supercapacitor performance is strongly affected by the initial and zero charge potentials of the electrodes. Further, the differences are highlighted and elaborated between freshly prepared, aged under open circuit conditions, and cycled electrodes of composites of conducting polymers and carbon nanotubes. The first voltammetric charging-discharging cycle has an electrode conditioning effect to change the electrodes from their initial potentials to the potential of zero voltage, and reduce the irreversibility. PMID:25897670

A finite element procedure for radio-frequency sheath–plasma interactions based on a sheath impedance model

DOE PAGES

Kohno, H.; Myra, J. R.

2017-07-24

A finite element code that solves self-consistent radio-frequency (RF) sheath-plasma interaction problems is improved by incorporating a generalized sheath boundary condition in the macroscopic solution scheme. This sheath boundary condition makes use of a complex sheath impedance including both the sheath capacitance and resistance, which enables evaluation of not only the RF voltage across the sheath but also the power dissipation in the sheath. The newly developed finite element procedure is applied to cases where the background magnetic field is perpendicular to the sheath surface in one- and two-dimensional domains filled by uniform low- and high-density plasmas. The numerical resultsmore » are compared with those obtained by employing the previous capacitive sheath model at a typical frequency for ion cyclotron heating used in fusion experiments. It is shown that for sheaths on the order of 100 V in a high-density plasma, localized RF power deposition can reach a level which causes material damage. It is also shown that the sheath-plasma wave resonances predicted by the capacitive sheath model do not occur when parameters are such that the generalized sheath impedance model substantially modifies the capacitive character of the sheath. Here, possible explanations for the difference in the maximum RF sheath voltage depending on the plasma density are also discussed.« less

Penicillin biosensor based on a capacitive field-effect structure functionalized with a dendrimer/carbon nanotube multilayer.

PubMed

Siqueira, José R; Abouzar, Maryam H; Poghossian, Arshak; Zucolotto, Valtencir; Oliveira, Osvaldo N; Schöning, Michael J

2009-10-15

Silicon-based sensors incorporating biomolecules are advantageous for processing and possible biological recognition in a small, reliable and rugged manufactured device. In this study, we report on the functionalization of field-effect (bio-)chemical sensors with layer-by-layer (LbL) films containing single-walled carbon nanotubes (SWNTs) and polyamidoamine (PAMAM) dendrimers. A capacitive electrolyte-insulator-semiconductor (EIS) structure modified with carbon nanotubes (EIS-NT) was built, which could be used as a penicillin biosensor. From atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM) images, the LbL films were shown to be highly porous due to interpenetration of SWNTs into the dendrimer layers. Capacitance-voltage (C/V) measurements pointed to a high pH sensitivity of ca. 55 mV/pH for the EIS-NT structures. The biosensing ability towards penicillin of an EIS-NT-penicillinase biosensor was also observed as the flat-band voltage shifted to lower potentials at different penicillin concentrations. A dynamic response of penicillin concentrations, ranging from 5.0 microM to 25 mM, was evaluated for an EIS-NT with the penicillinase enzyme immobilized onto the surfaces, via constant-capacitance (ConCap) measurements, achieving a sensitivity of ca. 116 mV/decade. The presence of the nanostructured PAMAM/SWNT LbL film led to sensors with higher sensitivity and better performance.

A finite element procedure for radio-frequency sheath–plasma interactions based on a sheath impedance model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohno, H.; Myra, J. R.

A finite element code that solves self-consistent radio-frequency (RF) sheath-plasma interaction problems is improved by incorporating a generalized sheath boundary condition in the macroscopic solution scheme. This sheath boundary condition makes use of a complex sheath impedance including both the sheath capacitance and resistance, which enables evaluation of not only the RF voltage across the sheath but also the power dissipation in the sheath. The newly developed finite element procedure is applied to cases where the background magnetic field is perpendicular to the sheath surface in one- and two-dimensional domains filled by uniform low- and high-density plasmas. The numerical resultsmore » are compared with those obtained by employing the previous capacitive sheath model at a typical frequency for ion cyclotron heating used in fusion experiments. It is shown that for sheaths on the order of 100 V in a high-density plasma, localized RF power deposition can reach a level which causes material damage. It is also shown that the sheath-plasma wave resonances predicted by the capacitive sheath model do not occur when parameters are such that the generalized sheath impedance model substantially modifies the capacitive character of the sheath. Here, possible explanations for the difference in the maximum RF sheath voltage depending on the plasma density are also discussed.« less

Measured radial dependence of the peak sheath voltages present in very high frequency capacitive discharges

DOE PAGES

Barnat, E. V.; Miller, P. A.; Hebner, G. A.; ...

2007-05-16

In this paper, the radial distribution of the measured voltage drop across a sheath formed between a 300mm electrode and an argon plasma discharge is shown to depend on the excitation radio frequency, under constant power and pressure conditions. At a lower frequency of 13.56MHz, the voltage drop across the sheath is uniform across the 300mm electrode, while at higher frequencies of 60 and 162MHz the voltage drop becomes radially nonuniform. Finally, the magnitude and spatial extent of the nonuniformity become greater with increasing frequency.

Radial displacement sensor for non-contact bearings

NASA Technical Reports Server (NTRS)

McCormick, John A. (Inventor); Sixsmith, Herbert (Inventor)

1998-01-01

A radial position sensor includes four capacitive electrodes oriented about a shaft, arranged in two diametrically opposite pairs. Sensor circuitry generates an output signal in proportion to the capacitance between the electrodes and the shaft; the capacitance between an electrode and the shaft increases as the shaft approaches the electrode and decreases as the shaft recedes from the electrode. The sensor circuitry applies an alternating voltage to one electrode of a pair and a 180 degree out of phase alternating voltage to the other electrode of the pair. The electrical responses of the two electrodes to their respective input signals are summed to form a radial deviation signal which is relatively free from the alternating voltage and accurately represents the position of the shaft relative to the electrodes of the pair.

Capacitive micromachined ultrasonic transducers (CMUTs) with isolation posts.

PubMed

Huang, Yongli; Zhuang, Xuefeng; Haeggstrom, Edward O; Ergun, A Sanli; Cheng, Ching-Hsiang; Khuri-Yakub, Butrus T

2008-03-01

In this paper, an improved design of a capacitive micromachined ultrasonic transducer (CMUT) is presented. The design improvement aims to address the reliability issues of a CMUT and to extend the device operation beyond the contact (collapse) voltage. The major design novelty is the isolation posts in the vacuum cavities of the CMUT cells instead of full-coverage insulation layers in conventional CMUTs. This eliminates the contact voltage drifting due to charging caused by the insulation layer, and enables repeatable CMUT operation in the post-contact regime. Ultrasonic tests of the CMUTs with isolation posts (PostCMUTs) in air (electrical input impedance and capacitance vs. bias voltage) and immersion (transmission and reception) indicate acoustic performance similar to that obtained from conventional CMUTs while no undesired side effects of this new design is observed.

Paramagnetic defects and charge trapping behavior of ZrO2 films deposited on germanium by plasma-enhanced CVD

NASA Astrophysics Data System (ADS)

Mahata, C.; Bera, M. K.; Bose, P. K.; Maiti, C. K.

2009-02-01

Internal photoemission and magnetic resonance studies have been performed to investigate the charge trapping behavior and chemical nature of defects in ultrathin (~14 nm) high-k ZrO2 dielectric films deposited on p-Ge (1 0 0) substrates at low temperature (<200 °C) by plasma-enhanced chemical vapor deposition (PECVD) in a microwave (700 W, 2.45 GHz) plasma at a pressure of ~65 Pa. Both the band and defect-related electron states have been characterized using electron paramagnetic resonance, internal photoemission, capacitance-voltage and current-voltage measurements under UV illumination. Capacitance-voltage and photocurrent-voltage measurements were used to determine the centroid of oxide charge within the high-k gate stack. The observed shifts in photocurrent response of the Al/ZrO2/GeO2/p-Ge metal-insulator-semiconductor (MIS) capacitors indicate the location of the centroids to be within the ZrO2 dielectric near to the gate electrode. Moreover, the measured flat band voltage and photocurrent shifts also indicate a large density of traps in the dielectric. The impact of plasma nitridation on the interfacial quality of the oxides has been investigated. Different N sources, such as NO and NH3, have been used for nitrogen engineering. Oxynitride samples show a lower defect density and trapping over the non-nitrided samples. The charge trapping and detrapping properties of MIS capacitors under stressing in constant current and voltage modes have been investigated in detail.

A Transfer Voltage Simulation Method for Generator Step Up Transformers

NASA Astrophysics Data System (ADS)

Funabashi, Toshihisa; Sugimoto, Toshirou; Ueda, Toshiaki; Ametani, Akihiro

It has been found from measurements for 13 sets of GSU transformers that a transfer voltage of a generator step-up (GSU) transformer involves one dominant oscillation frequency. The frequency can be estimated from the inductance and capacitance values of the GSU transformer low-voltage-side. This observation has led to a new method for simulating a GSU transformer transfer voltage. The method is based on the EMTP TRANSFORMER model, but stray capacitances are added. The leakage inductance and the magnetizing resistance are modified using approximate curves for their frequency characteristics determined from the measured results. The new method is validated in comparison with the measured results.

Influence of deposition conditions on electrical and mechanical properties of Sm2O3-doped CeO2 thin films prepared by EB-PVD (+IBAD) methods. Part 1: Effective relative permittivity

NASA Astrophysics Data System (ADS)

Hartmanová, Mária; Nádaždy, Vojtech; Kundracik, František; Mansilla, Catina

2013-03-01

Study is devoted to the effective relative permittivity ɛr of CeO2 + x. Sm2O3 thin films prepared by electron-beam physical vapour deposition and ionic beam-assisted deposition methods; ɛr was investigated by three independent ways from the bulk parallel capacitance Cp, impedance capacitance Cimp, and accumulation capacitance Cacc in dependence on the deposition conditions (deposition temperature, dopant amount x and Ar+ ion bombardment during the film deposition) used. Investigations were performed using impedance spectroscopy, capacitance-voltage and current-voltage characteristics as well as deep level transient spectroscopy. Results obtained are described and discussed.

Capacitance-voltage measurement in memory devices using ferroelectric polymer

NASA Astrophysics Data System (ADS)

Nguyen, Chien A.; Lee, Pooi See

2006-01-01

Application of thin polymer film as storing mean for non-volatile memory devices is investigated. Capacitance-voltage (C-V) measurement of metal-ferroelectric-metal device using ferroelectric copolymer P(VDF-TrFE) as dielectric layer shows stable 'butter-fly' curve. The two peaks in C-V measurement corresponding to the largest capacitance are coincidental at the coercive voltages that give rise to zero polarization in the polarization hysteresis measurement. By comparing data of C-V and P-E measurement, a correlation between two types of hysteresis is established in which it reveals simultaneous electrical processes occurring inside the device. These processes are caused by the response of irreversible and reversible polarization to the applied electric field that can be used to present a memory window. The memory effect of ferroelectric copolymer is further demonstrated for fabricating polymeric non-volatile memory devices using metal-ferroelectric-insulator-semiconductor structure (MFIS). By applying different sweeping voltages at the gate, bidirectional flat-band voltage shift is observed in the ferroelectric capacitor. The asymmetrical shift after negative sweeping is resulted from charge accumulation at the surface of Si substrate caused by the dipole direction in the polymer layer. The effect is reversed for positive voltage sweeping.

Energy output of a single outer hair cell: Effect of resonance

NASA Astrophysics Data System (ADS)

Iwasa, Kuni H.

2018-05-01

The ability of the mammalian ear in processing high frequency sounds, up to ˜100 kHz, is based on the capability of outer hair cells (OHCs) in responding to stimulation at high frequencies. These cells show a unique motility in their cell body coupled with charge movement. With this motile element, voltage changes generated by stimuli at their hair bundles drive the cell body and that, in turn, amplifies the signal. In vitro experiments show that the movement of these charges significantly increases the membrane capacitance, limiting the motile activity by an additional attenuation of voltage changes. It was found, however, that such an effect is due to the absence of mechanical load. In the presence of mechanical load, particularly inertial load, such as under in vivo conditions, the movement of motile charges should reduce the membrane capacitance, enhancing the mechanical power output.

Junctionless Thin-Film Transistors Gated by an H₃PO₄-Incorporated Chitosan Proton Conductor.

PubMed

Liu, Huixuan; Xun, Damao

2018-04-01

We fabricated an H3PO4-incorporated chitosan proton conductor film that exhibited the electric double layer effect and showed a high specific capacitance of 4.42 μF/cm2. Transparent indium tin oxide thin-film transistors gated by H3PO4-incorporated chitosan films were fabricated by sputtering through a shadow mask. The operating voltage was as low as 1.2 V because of the high specific capacitance of the H3PO4-incorporated chitosan dielectrics. The junctionless transparent indium tin oxide thin film transistors exhibited good performance, including an estimated current on/off ratio and field-effect mobility of 1.2 × 106 and 6.63 cm2V-1s-1, respectively. These low-voltage thin-film electric-double-layer transistors gated by H3PO4-incorporated chitosan are promising for next generation battery-powered "see-through" portable sensors.

Series resonance inverter with triggered vacuum gaps

NASA Astrophysics Data System (ADS)

Damstra, Geert C.; Zhang, X.

1994-05-01

Series resonance inverters based on semi-conductor switching elements are well-known and have a wide range of application, mainly for lower voltages. For high voltage application many switching elements have to be put in series to obtain sufficient blocking voltage. Voltage grinding and multiple gate control elements are needed. There is much experience with the triggered vacuum gaps as high voltage/high current single shot elements, for example in reignition circuits for synthetic circuit breaker tests. These elements have a blocking voltage of 50 - 100 kV and are triggerable by a light fiber control device. A prototype inverter has been developed that generates 0.1 Hz, 30 kV AC voltages with a flat top for tests on cables and capacitors of many micro farads fed from a low voltage supply of about 600 V. Only two TVG elements are needed to switch the resonant circuit alternatively on the positive or negative supply. The resonant circuit itself consists of the capacitance of the testobject and a high quality inductor that determines the frequency and the peak current of the voltage reversing process.

Transient Performance Improvement Circuit (TPIC)s for DC-DC converter applications

NASA Astrophysics Data System (ADS)

Lim, Sungkeun

Gordon Moore famously predicted the exponential increase in transistor integration and computing power that has been witnessed in recent decades [1]. In the near future, it is expected that more than one billion transistors will be integrated per chip, and advanced microprocessors will require clock speeds in excess of several GHz. The increasing number of transistors and high clock speeds will necessitate the consumption of more power. By 2014, it is expected that the maximum power consumption of the microprocessor will reach approximately 150W, and the maximum load current will be around 150A. Today's trend in power and thermal management is to reduce supply voltage as low as possible to reduce delivered power. It is anticipated that the Intel cores will operate on 0.8V of supply voltage by 2014 [2]. A significant challenge in Voltage Regulator Module (VRM) development for next generation microprocessors is to regulate the supply voltage within a certain tolerance band during high slew rate load transitions, since the required supply voltage tolerance band will be much narrower than the current requirement. If VR output impedance is maintained at a constant value from DC to high frequency, large output voltage spikes can be avoided during load cur- rent transients. Based on this, the Adaptive Voltage Position (AVP) concept was developed to achieve constant VR output impedance to improve transient response performance [3]. However, the VR output impedance can not be made constant over the entire frequency range with AVP design, because the AVP design makes the VR output impedance constant only at low frequencies. To make the output impedance constant at high frequencies, many bulk capacitors and ceramic capacitors are required. The tight supply voltage tolerance for the next generation of microprocessors during high slew rate load transitions requires fast transient response power supplies. A VRM can not follow the high slew rate load current transients, because of the slow inductor current slew rate which is determined by the input voltage, output voltage, and the inductance. The remaining inductor current in the power delivery path will charge the output capacitors and develop a voltage across the ESR. As a result, large output voltage spikes occur during load current transients. Due to their limited control bandwidth, traditional VRs can not sufficiently respond rapidly to certain load transients. As a result, a large output voltage spike can occur during load transients, hence requiring a large amount of bulk capacitance to decouple the VR from the load [2]. If the remaining inductor current is removed from the power stage or the inductor current slew rate is changed, the output voltage spikes can be clamped, allowing the output capacitance to be reduced. A new design methodology for a Transient Performance Improvement Circuit(TPIC) based on controlling the output impedance of a regulator is presented. The TPIC works in parallel with a voltage regulator (VR)'s ceramic capacitors to achieve faster voltage regulation without the need for a large bulk capacitance, and can serve as a replacement for bulk capacitors. The specific function of the TPIC is to mimic the behavior of the bulk capacitance in a traditional VRM by sinking and sourcing large currents during transients, allowing the VR to respond quickly to current transients without the need for a large bulk capacitance. This will allow fast transient response without the need for a large bulk capacitor. The main challenge in applying the TPIC is creating a design which will not interfere with VR operation. A TPIC for a 4 Switch Buck-Boost (4SBB) converter is presented which functions by con- trolling the inductor current slew rate during load current transients. By increasing the inductor current slew rate, the remaining inductor current can be removed from the 4SBB power delivery path and the output voltage spike can be clamped. A second TPIC is presented which is designed to improve the performance of an LDO regulator during output current transients. A TPIC for a LDO regulator is proposed to reduce the over voltage spike settling time. During a load current step down transient, the only current discharging path is a light load current. However, it takes a long time to discharge the current charged in the output capacitors with the light load current. The proposed TPIC will make an additional current discharging path to reduce the long settling time. By reducing the settling time, the load current transient frequency of the LDO regulator can be increased. A Ripple Cancellation Circuit (RCC) is proposed to reduce the output voltage ripple. The RCC has a very similar concept with the TPIC which is sinking or injecting additional current to the power stage to compensate the inductor ripple current. The proposed TPICs and RCC have been implemented with a 0.6m CMOS process. A single-phase VR, a 4SBB converter, and a LDO regulator have been utilized with the proposed TPIC to evaluate its performance. The theoretical analysis will be confirmed by Cadence simulation results and experimental results.

Pulse power applications of silicon diodes in EML capacitive pulsers

NASA Astrophysics Data System (ADS)

Dethlefsen, Rolf; McNab, Ian; Dobbie, Clyde; Bernhardt, Tom; Puterbaugh, Robert; Levine, Frank; Coradeschi, Tom; Rinaldi, Vito

1993-01-01

Crowbar diodes are used for increasing the energy transfer from capacitive pulse forming networks. They also prevent voltage reversal on the energy storage capacitors. 52 mm diameter diodes with a 5 kV reverse blocking voltage, rated 40 kA were successfully used for the 32 MJ SSG rail gun. An uprated diode with increased current capability and a 15 kV reverse blocking voltage has been developed. Transient thermal analysis has predicted the current ratings for different pulse length. Analysis verification is obtained from destructive testing.

Ferroelectric, dielectric and electrical behavior of two-dimensional lead sulphide nanosheets

NASA Astrophysics Data System (ADS)

Afsar, M. F.; Jamil, Arifa; Rafiq, M. A.

2017-12-01

Two-dimensional pure cubic phase lead sulphide (PbS) nanosheets were synthesized using solid state reaction method at ambient pressure and low temperature ~190 °C. From 210 K-300 K, small polaron hopping conduction mechanism was found to be dominant in PbS nanosheets at frequencies 20 Hz-2 MHz. High values of dielectric constant (~200) and electrical conductivity (of the order of 10-3 S m-1 at 300 K) of PbS nanosheets were extracted suggesting that it is a proficient material for capacitive storage devices. A high value of density of states of the order of 1032 eV-1 cm-3 was obtained for PbS nanosheets. The capacitance-voltage (CV) measurements of PbS nanosheets resulted in a stable butterfly loop due to switching of ferroelectric polarization at 300 K. The permittivity calculated at 0 V capacitance was ~150 and the dielectric loss remained below ~0.50. The polarization-voltage (QV) measurements showed a remnant polarization 23 µC cm-2 in PbS nanosheets. The leakage current density was below 0.5 mA cm-2 in the range  ±5 V.

Scalable high-power redox capacitors with aligned nanoforests of crystalline MnO₂ nanorods by high voltage electrophoretic deposition.

PubMed

Santhanagopalan, Sunand; Balram, Anirudh; Meng, Dennis Desheng

2013-03-26

It is commonly perceived that reduction-oxidation (redox) capacitors have to sacrifice power density to achieve higher energy density than carbon-based electric double layer capacitors. In this work, we report the synergetic advantages of combining the high crystallinity of hydrothermally synthesized α-MnO2 nanorods with alignment for high performance redox capacitors. Such an approach is enabled by high voltage electrophoretic deposition (HVEPD) technology which can obtain vertically aligned nanoforests with great process versatility. The scalable nanomanufacturing process is demonstrated by roll-printing an aligned forest of α-MnO2 nanorods on a large flexible substrate (1 inch by 1 foot). The electrodes show very high power density (340 kW/kg at an energy density of 4.7 Wh/kg) and excellent cyclability (over 92% capacitance retention over 2000 cycles). Pretreatment of the substrate and use of a conductive holding layer have also been shown to significantly reduce the contact resistance between the aligned nanoforests and the substrates. High areal specific capacitances of around 8500 μF/cm(2) have been obtained for each electrode with a two-electrode device configuration. Over 93% capacitance retention was observed when the cycling current densities were increased from 0.25 to 10 mA/cm(2), indicating high rate capabilities of the fabricated electrodes and resulting in the very high attainable power density. The high performance of the electrodes is attributed to the crystallographic structure, 1D morphology, aligned orientation, and low contact resistance.

Application of the electroosmotic effect for thrust generation

NASA Astrophysics Data System (ADS)

Hansen, Thomas Edward

The present work focuses on demonstrating the capabilities of electroosmotic pumps, (EOP) to generate thrust. An underwater glider was successfully propelled by electroosmosis for the first time published - at 0.85 inches per second. Asymmetric AC voltage pulsing proved to produce higher flow rates then equivalent DC pumps for the same average voltage. Ultra-short pulsing proved 100 nanosecond rise times in EOP are possible, which surpassed published predictions by three orders of magnitude. Theories behind efficiency losses of high power EOP were investigated. Direct measurement of effective voltage at the face of a membrane is the most accurate way to determine voltage drop across the electrolyte of an EOP. Forced convection lowered efficiency of the EOP for low voltages by preventing capacitance charging, but proved to prolong pump life during high power application.

Capacitive Sensing of Glucose in Electrolytes Using Graphene Quantum Capacitance Varactors.

PubMed

Zhang, Yao; Ma, Rui; Zhen, Xue V; Kudva, Yogish C; Bühlmann, Philippe; Koester, Steven J

2017-11-08

A novel graphene-based variable capacitor (varactor) that senses glucose based on the quantum capacitance effect was successfully developed. The sensor utilizes a metal-oxide-graphene varactor device structure that is inherently compatible with passive wireless sensing, a key advantage for in vivo glucose sensing. The graphene varactors were functionalized with pyrene-1-boronic acid (PBA) by self-assembly driven by π-π interactions. Successful surface functionalization was confirmed by both Raman spectroscopy and capacitance-voltage characterization of the devices. Through glucose binding to the PBA, the glucose concentration in the buffer solutions modulates the level of electrostatic doping of the graphene surface to different degrees, which leads to capacitance changes and Dirac voltage shifts. These responses to the glucose concentration were shown to be reproducible and reversible over multiple measurement cycles, suggesting promise for eventual use in wireless glucose monitoring.

Capacitance changes in frog skin caused by theophylline and antidiuretic hormone.

PubMed

Cuthbert, A W; Painter, E

1969-09-01

1. Impedance loci for frog skins have been calculated by computer analysis from voltage transients developed across the tissues.2. Attention has been paid to simultaneous changes in conductance and capacitance of skins treated either with antidiuretic hormone (ADH) or with theophylline. These drugs always caused an increase in conductance and usually the skin capacitance also increased. However, changes in conductance were not correlated with capacitance changes.3. Changes in capacitance caused by the drugs may represent pore formation in the barrier to water flow, since both drugs increase hydro-osmotic flow in epithelia. If this interpretation is correct, then 0.14% of the membrane area forms water-permeable pores in response to a maximal dose of ADH. This value is somewhat less than the value obtained previously (0.3%) by graphical analysis.4. A theoretical account is given of the relative accuracy of the computer method and the graphical method for voltage transient analysis.

Millimeter-Wave Voltage-Controlled Oscillators in 0.13-micrometer CMOS Technology

DTIC Science & Technology

2006-06-01

controlled oscillators. Varactor , transistor, and in- ductor designs are optimized to reduce the parasitic capacitances. An investigation of tradeoff between...quality factor and tuning range for MOS varactors at 24 GHz has shown that the polysilicon gate lengths between 0.18 and 0.24 m result both good...millimeter wave, MOS varactor , quality factor, transmission line, voltage-controlled oscillator (VCO). I. INTRODUCTION WITH THE RAPID advance of high

Determination of bulk and interface density of states in metal oxide semiconductor thin-film transistors by using capacitance-voltage characteristics

NASA Astrophysics Data System (ADS)

Wei, Xixiong; Deng, Wanling; Fang, Jielin; Ma, Xiaoyu; Huang, Junkai

2017-10-01

A physical-based straightforward extraction technique for interface and bulk density of states in metal oxide semiconductor thin film transistors (TFTs) is proposed by using the capacitance-voltage (C-V) characteristics. The interface trap density distribution with energy has been extracted from the analysis of capacitance-voltage characteristics. Using the obtained interface state distribution, the bulk trap density has been determined. With this method, for the interface trap density, it is found that deep state density nearing the mid-gap is approximately constant and tail states density increases exponentially with energy; for the bulk trap density, it is a superposition of exponential deep states and exponential tail states. The validity of the extraction is verified by comparisons with the measured current-voltage (I-V) characteristics and the simulation results by the technology computer-aided design (TCAD) model. This extraction method uses non-numerical iteration which is simple, fast and accurate. Therefore, it is very useful for TFT device characterization.

Capacitance-voltage analysis of electrical properties for WSe2 field effect transistors with high-k encapsulation layer

NASA Astrophysics Data System (ADS)

Ko, Seung-Pil; Shin, Jong Mok; Jang, Ho Kyun; You, Min Youl; Jin, Jun-Eon; Choi, Miri; Cho, Jiung; Kim, Gyu-Tae

2018-02-01

Doping effects in devices based on two-dimensional (2D) materials have been widely studied. However, detailed analysis and the mechanism of the doping effect caused by encapsulation layers has not been sufficiently explored. In this work, we present experimental studies on the n-doping effect in WSe2 field effect transistors (FETs) with a high-k encapsulation layer (Al2O3) grown by atomic layer deposition. In addition, we demonstrate the mechanism and origin of the doping effect. After encapsulation of the Al2O3 layer, the threshold voltage of the WSe2 FET negatively shifted with the increase of the on-current. The capacitance-voltage measurements of the metal insulator semiconductor (MIS) structure proved the presence of the positive fixed charges within the Al2O3 layer. The flat-band voltage of the MIS structure of Au/Al2O3/SiO2/Si was shifted toward the negative direction on account of the positive fixed charges in the Al2O3 layer. Our results clearly revealed that the fixed charges in the Al2O3 encapsulation layer modulated the Fermi energy level via the field effect. Moreover, these results possibly provide fundamental ideas and guidelines to design 2D materials FETs with high-performance and reliability.

Anomalous C-V response correlated to relaxation processes in TiO{sub 2} thin film based-metal-insulator-metal capacitor: Effect of titanium and oxygen defects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kahouli, A., E-mail: kahouli.kader@yahoo.fr; University Grenoble Alpes, G2Elab, F-38000 Grenoble; Marichy, C.

2015-04-21

Capacitance-voltage (C–V) and capacitance-frequency (C–f) measurements are performed on atomic layer deposited TiO{sub 2} thin films with top and bottom Au and Pt electrodes, respectively, over a large temperature and frequency range. A sharp capacitance peak/discontinuity (C–V anomalous) is observed in the C–V characteristics at various temperatures and voltages. It is demonstrated that this phenomenon is directly associated with oxygen vacancies. The C–V peak irreversibility and dissymmetry at the reversal dc voltage are attributed to difference between the Schottky contacts at the metal/TiO{sub 2} interfaces. Dielectric analyses reveal two relaxation processes with degeneration of the activation energy. The low trapmore » level of 0.60–0.65 eV is associated with the first ionized oxygen vacancy at low temperature, while the deep trap level of 1.05 eV is associated to the second ionized oxygen vacancy at high temperature. The DC conductivity of the films exhibits a transition temperature at 200 °C, suggesting a transition from a conduction regime governed by ionized oxygen vacancies to one governed by interstitial Ti{sup 3+} ions. Both the C–V anomalous and relaxation processes in TiO{sub 2} arise from oxygen vacancies, while the conduction mechanism at high temperature is governed by interstitial titanium ions.« less

Harvesting dissipated energy with a mesoscopic ratchet

NASA Astrophysics Data System (ADS)

Roche, B.; Roulleau, P.; Jullien, T.; Jompol, Y.; Farrer, I.; Ritchie, D. A.; Glattli, D. C.

2015-04-01

The search for new efficient thermoelectric devices converting waste heat into electrical energy is of major importance. The physics of mesoscopic electronic transport offers the possibility to develop a new generation of nanoengines with high efficiency. Here we describe an all-electrical heat engine harvesting and converting dissipated power into an electrical current. Two capacitively coupled mesoscopic conductors realized in a two-dimensional conductor form the hot source and the cold converter of our device. In the former, controlled Joule heating generated by a voltage-biased quantum point contact results in thermal voltage fluctuations. By capacitive coupling the latter creates electric potential fluctuations in a cold chaotic cavity connected to external leads by two quantum point contacts. For unequal quantum point contact transmissions, a net electrical current is observed proportional to the heat produced.

Capacitance-type blade-tip clearance measurement system using a dual amplifier with ramp/dc inputs and integration

NASA Technical Reports Server (NTRS)

Sarma, Garimella R.; Barranger, John P.

1992-01-01

The analysis and prototype results of a dual-amplifier circuit for measuring blade-tip clearance in turbine engines are presented. The capacitance between the blade tip and mounted capacitance electrode within a guard ring of a probe forms one of the feedback elements of an operational amplifier (op amp). The differential equation governing the circuit taking into consideration the nonideal features of the op amp was formulated and solved for two types of inputs (ramp and dc) that are of interest for the application. Under certain time-dependent constraints, it is shown that (1) with a ramp input the circuit has an output voltage proportional to the static tip clearance capacitance, and (2) with a dc input, the output is proportional to the derivative of the clearance capacitance, and subsequent integration recovers the dynamic capacitance. The technique accommodates long cable lengths and environmentally induced changes in cable and probe parameters. System implementation for both static and dynamic measurements having the same high sensitivity is also presented.

Capacitance-type blade-tip clearance measurement system using a dual amplifier with ramp/dc inputs and integration

NASA Astrophysics Data System (ADS)

Sarma, Garimella R.; Barranger, John P.

1992-10-01

The analysis and prototype results of a dual-amplifier circuit for measuring blade-tip clearance in turbine engines are presented. The capacitance between the blade tip and mounted capacitance electrode within a guard ring of a probe forms one of the feedback elements of an operational amplifier (op amp). The differential equation governing the circuit taking into consideration the nonideal features of the op amp was formulated and solved for two types of inputs (ramp and dc) that are of interest for the application. Under certain time-dependent constraints, it is shown that (1) with a ramp input the circuit has an output voltage proportional to the static tip clearance capacitance, and (2) with a dc input, the output is proportional to the derivative of the clearance capacitance, and subsequent integration recovers the dynamic capacitance. The technique accommodates long cable lengths and environmentally induced changes in cable and probe parameters. System implementation for both static and dynamic measurements having the same high sensitivity is also presented.

Artificial sensory hairs based on the flow sensitive receptor hairs of crickets

NASA Astrophysics Data System (ADS)

Dijkstra, M.; van Baar, J. J.; Wiegerink, R. J.; Lammerink, T. S. J.; de Boer, J. H.; Krijnen, G. J. M.

2005-07-01

This paper presents the modelling, design, fabrication and characterization of flow sensors based on the wind-receptor hairs of crickets. Cricket sensory hairs are highly sensitive to drag-forces exerted on the hair shaft. Artificial sensory hairs have been realized in SU-8 on suspended SixNy membranes. The movement of the membranes is detected capacitively. Capacitance versus voltage, frequency dependence and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept.

On electron heating in a low pressure capacitively coupled oxygen discharge

NASA Astrophysics Data System (ADS)

Gudmundsson, J. T.; Snorrason, D. I.

2017-11-01

We use the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 to explore the charged particle densities, the electronegativity, the electron energy probability function, and the electron heating mechanism in a single frequency capacitively coupled oxygen discharge, when the applied voltage amplitude is varied. We explore discharges operated at 10 mTorr, where electron heating within the plasma bulk (the electronegative core) dominates, and at 50 mTorr, where sheath heating dominates. At 10 mTorr, the discharge is operated in a combined drift-ambipolar and α-mode, and at 50 mTorr, it is operated in the pure α-mode. At 10 mTorr, the effective electron temperature is high and increases with increased driving voltage amplitude, while at 50 mTorr, the effective electron temperature is much lower, in particular, within the electronegative core, where it is roughly 0.2-0.3 eV, and varies only a little with the voltage amplitude.

Extrinsic and Intrinsic Frequency Dispersion of High-k Materials in Capacitance-Voltage Measurements

PubMed Central

Tao, J.; Zhao, C.Z.; Zhao, C.; Taechakumput, P.; Werner, M.; Taylor, S.; Chalker, P. R.

2012-01-01

In capacitance-voltage (C-V) measurements, frequency dispersion in high-k dielectrics is often observed. The frequency dependence of the dielectric constant (k-value), that is the intrinsic frequency dispersion, could not be assessed before suppressing the effects of extrinsic frequency dispersion, such as the effects of the lossy interfacial layer (between the high-k thin film and silicon substrate) and the parasitic effects. The effect of the lossy interfacial layer on frequency dispersion was investigated and modeled based on a dual frequency technique. The significance of parasitic effects (including series resistance and the back metal contact of the metal-oxide-semiconductor (MOS) capacitor) on frequency dispersion was also studied. The effect of surface roughness on frequency dispersion is also discussed. After taking extrinsic frequency dispersion into account, the relaxation behavior can be modeled using the Curie-von Schweidler (CS) law, the Kohlrausch-Williams-Watts (KWW) relationship and the Havriliak-Negami (HN) relationship. Dielectric relaxation mechanisms are also discussed. PMID:28817021

Temperature dependence of frequency response characteristics in organic field-effect transistors

NASA Astrophysics Data System (ADS)

Lu, Xubing; Minari, Takeo; Liu, Chuan; Kumatani, Akichika; Liu, J.-M.; Tsukagoshi, Kazuhito

2012-04-01

The frequency response characteristics of semiconductor devices play an essential role in the high-speed operation of electronic devices. We investigated the temperature dependence of dynamic characteristics in pentacene-based organic field-effect transistors and metal-insulator-semiconductor capacitors. As the temperature decreased, the capacitance-voltage characteristics showed large frequency dispersion and a negative shift in the flat-band voltage at high frequencies. The cutoff frequency shows Arrhenius-type temperature dependence with different activation energy values for various gate voltages. These phenomena demonstrate the effects of charge trapping on the frequency response characteristics, since decreased mobility prevents a fast charge response for alternating current signals at low temperatures.

0.5 V 5.8 GHz highly linear current-reuse voltage-controlled oscillator with back-gate tuning technique

NASA Astrophysics Data System (ADS)

Ikeda, Sho; Lee, Sang-Yeop; Ito, Hiroyuki; Ishihara, Noboru; Masu, Kazuya

2015-04-01

In this paper, we present a voltage-controlled oscillator (VCO), which achieves highly linear frequency tuning under a low supply voltage of 0.5 V. To obtain the linear frequency tuning of a VCO, the high linearity of the threshold voltage of a varactor versus its back-gate voltage is utilized. This enables the linear capacitance tuning of the varactor; thus, a highly linear VCO can be achieved. In addition, to decrease the power consumption of the VCO, a current-reuse structure is employed as a cross-coupled pair. The proposed VCO was fabricated using a 65 nm Si complementary metal oxide semiconductor (CMOS) process. It shows the ratio of the maximum VCO gain (KVCO) to the minimum one to be 1.28. The dc power consumption is 0.33 mW at a supply voltage of 0.5 V. The measured phase noise at 10 MHz offset is -123 dBc/Hz at an output frequency of 5.8 GHz.

Forecasting of high voltage insulation performance: Testing of recommended potting materials and of capacitors

NASA Technical Reports Server (NTRS)

Bever, R. S.

1984-01-01

Nondestructive high voltage test techniques (mostly electrical methods) are studied to prevent total or catastrophic breakdown of insulation systems under applied high voltage in space. Emphasis is on the phenomenon of partial breakdown or partial discharge (P.D.) as a symptom of insulation quality, notably partial discharge testing under D.C. applied voltage. Many of the electronic parts and high voltage instruments in space experience D.C. applied stress in service, and application of A.C. voltage to any portion thereof would be prohibited. Suggestions include: investigation of the ramp test method for D.C. partial discharge measurements; testing of actual flight-type insulation specimen; perfect plotting resin samples with controlled defects for test; several types of plotting resins and recommendations of the better ones from the electrical characteristics; thermal and elastic properties are also considered; testing of commercial capaciters; and approximate acceptance/rejection/rerating criteria for sample test elements for space use, based on D.C. partial discharge.

Biasing of Capacitive Micromachined Ultrasonic Transducers.

PubMed

Caliano, Giosue; Matrone, Giulia; Savoia, Alessandro Stuart

2017-02-01

Capacitive micromachined ultrasonic transducers (CMUTs) represent an effective alternative to piezoelectric transducers for medical ultrasound imaging applications. They are microelectromechanical devices fabricated using silicon micromachining techniques, developed in the last two decades in many laboratories. The interest for this novel transducer technology relies on its full compatibility with standard integrated circuit technology that makes it possible to integrate on the same chip the transducers and the electronics, thus enabling the realization of extremely low-cost and high-performance devices, including both 1-D or 2-D arrays. Being capacitive transducers, CMUTs require a high bias voltage to be properly operated in pulse-echo imaging applications. The typical bias supply residual ripple of high-quality high-voltage (HV) generators is in the millivolt range, which is comparable with the amplitude of the received echo signals, and it is particularly difficult to minimize. The aim of this paper is to analyze the classical CMUT biasing circuits, highlighting the features of each one, and to propose two novel HV generator architectures optimized for CMUT biasing applications. The first circuit proposed is an ultralow-residual ripple (<5 [Formula: see text]) HV generator that uses an extremely stable sinusoidal power oscillator topology. The second circuit employs a commercially available integrated step-up converter characterized by a particularly efficient switching topology. The circuit is used to bias the CMUT by charging a buffer capacitor synchronously with the pulsing sequence, thus reducing the impact of the switching noise on the received echo signals. The small area of the circuit (about 1.5 cm 2 ) makes it possible to generate the bias voltage inside the probe, very close to the CMUT, making the proposed solution attractive for portable applications. Measurements and experiments are shown to demonstrate the effectiveness of the new approaches presented.

An HF coaxial bridge for measuring impedance ratios up to 1 MHz

NASA Astrophysics Data System (ADS)

Kucera, J.; Sedlacek, R.; Bohacek, J.

2012-08-01

A four-terminal pair coaxial ac bridge developed for calibrating both resistance and capacitance ratios and working in the frequency range from 100 kHz up to 1 MHz is described. A reference inductive voltage divider (IVD) makes it possible to calibrate ratios 1:1 and 10:1 with uncertainty of a few parts in 105. The IVD is calibrated by means of a series-parallel capacitance device (SPCD). Use of the same ac bridge with minimal changes for calibrating the SPCD, IVD and unknown impedances simplifies the whole calibration process. The bridge balance conditions are fulfilled with simple capacitance and resistance decades and by injecting voltage supplied from the auxiliary direct digital synthesizer. Bridge performance was checked on the basis of resistance ratio measurements and also capacitance ratio measurements.

Current transport and capacitance-voltage characteristics of an n-PbTe/p-GaP heterojunction prepared using the electron beam deposition technique

NASA Astrophysics Data System (ADS)

Nasr, Mahmoud; El Radaf, I. M.; Mansour, A. M.

2018-04-01

In this study, a crystalline n-PbTe/p-GaP heterojunction was fabricated using the electron beam deposition technique. The structural properties of the prepared heterojunction were examined by X-ray diffraction and scanning electron microscopy. The dark current-voltage characteristics of the heterojunction were investigated at different temperatures ranging from 298 to 398 K. The rectification factor, series resistance, shunt resistance, diode ideality factor, and effective barrier height (ϕb) were determined. The photovoltaic parameters were identified based on the current density-voltage characteristics under illumination. The capacitance-voltage characteristics showed that the junction was abrupt in nature.

Charge Gain, Voltage Gain, and Node Capacitance of the SAPHIRA Detector Pixel by Pixel

NASA Astrophysics Data System (ADS)

Pastrana, Izabella M.; Hall, Donald N. B.; Baker, Ian M.; Jacobson, Shane M.; Goebel, Sean B.

2018-01-01

The University of Hawai`i Institute for Astronomy has partnered with Leonardo (formerly Selex) in the development of HgCdTe linear mode avalanche photodiode (L-APD) SAPHIRA detectors. The SAPHIRA (Selex Avalanche Photodiode High-speed Infra-Red Array) is ideally suited for photon-starved astronomical observations, particularly near infrared (NIR) adaptive optics (AO) wave-front sensing. I have measured the stability, and linearity with current, of a 1.7-um (10% spectral bandpass) infrared light emitting diode (IR LED) used to illuminate the SAPHIRA and have then utilized this source to determine the charge gain (in e-/ADU), voltage gain (in uV/ADU), and node capacitance (in fF) for each pixel of the 320x256@24um SAPHIRA. These have previously only been averages over some sub-array. Determined from the ratio of the temporal averaged signal level to variance under constant 1.7-um LED illumination, I present the charge gain pixel-by-pixel in a 64x64 sub-array at the center of the active area of the SAPHIRA (analyzed separately as four 32x32 sub-arrays) to be about 1.6 e-/ADU (σ=0.5 e-/ADU). Additionally, the standard technique of varying the pixel reset voltage (PRV) in 10 mV increments and recording output frames for the same 64x64 subarray found the voltage gain per pixel to be about 11.7 uV/ADU (σ=0.2 uV/ADU). Finally, node capacitance was found to be approximately 23 fF (σ=6 fF) utilizing the aforementioned charge and voltage gain measurements. I further discuss the linearity measurements of the 1.7-um LED used in the charge gain characterization procedure.

Low-voltage electric-double-layer paper transistors gated by microporous SiO2 processed at room temperature

NASA Astrophysics Data System (ADS)

Sun, Jia; Wan, Qing; Lu, Aixia; Jiang, Jie

2009-11-01

Battery drivable low-voltage SnO2-based paper thin-film transistors with a near-zero threshold voltage (Vth=0.06 V) gated by microporous SiO2 dielectric with electric-double-layer (EDL) effect are fabricated at room temperature. The operating voltage is found to be as low as 1.5 V due to the huge gate specific capacitance (1.34 μF/cm2 at 40 Hz) related to EDL formation. The subthreshold gate voltage swing and current on/off ratio is found to be 82 mV/decade and 2.0×105, respectively. The electron field-effect mobility is estimated to be 47.3 cm2/V s based on the measured gate specific capacitance at 40 Hz.

High resolution space quartz-flexure accelerometer based on capacitive sensing and electrostatic control technology.

PubMed

Tian, W; Wu, S C; Zhou, Z B; Qu, S B; Bai, Y Z; Luo, J

2012-09-01

High precision accelerometer plays an important role in space scientific and technical applications. A quartz-flexure accelerometer operating in low frequency range, having a resolution of better than 1 ng/Hz(1/2), has been designed based on advanced capacitive sensing and electrostatic control technologies. A high precision capacitance displacement transducer with a resolution of better than 2 × 10(-6) pF/Hz(1/2) above 0.1 Hz, is used to measure the motion of the proof mass, and the mechanical stiffness of the spring oscillator is compensated by adjusting the voltage between the proof mass and the electrodes to induce a proper negative electrostatic stiffness, which increases the mechanical sensitivity and also suppresses the position measurement noise down to 3 × 10(-10) g/Hz(1/2) at 0.1 Hz. A high resolution analog-to-digital converter is used to directly readout the feedback voltage applied on the electrodes in order to suppress the action noise to 4 × 10(-10) g/Hz(1/2) at 0.1 Hz. A prototype of the quartz-flexure accelerometer has been developed and tested, and the preliminary experimental result shows that its resolution comes to about 8 ng/Hz(1/2) at 0.1 Hz, which is mainly limited by its mechanical thermal noise due to low quality factor.

Extraction of carrier mobility and interface trap density in InGaAs metal oxide semiconductor structures using gated Hall method

NASA Astrophysics Data System (ADS)

Chidambaram, Thenappan

III-V semiconductors are potential candidates to replace Si as a channel material in next generation CMOS integrated circuits owing to their superior carrier mobilities. Low density of states (DOS) and typically high interface and border trap densities (Dit) in high mobility group III-V semiconductors provide difficulties in quantification of Dit near the conduction band edge. The trap response above the threshold voltage of a MOSFET can be very fast, and conventional Dit extraction methods, based on capacitance/conductance response (CV methods) of MOS capacitors at frequencies <1MHz, cannot distinguish conducting and trapped carriers. In addition, the CV methods have to deal with high dispersion in the accumulation region that makes it a difficult task to measure the true oxide capacitance, Cox value. Another implication of these properties of III-V interfaces is an ambiguity of determination of electron density in the MOSFET channel. Traditional evaluation of carrier density by integration of the C-V curve, gives incorrect values for D it and mobility. Here we employ gated Hall method to quantify the D it spectrum at the high-K oxide/III-V semiconductor interface for buried and surface channel devices using Hall measurement and capacitance-voltage data. Determination of electron density directly from Hall measurements allows for obtaining true mobility values.

Frequency dispersion of capacitance-voltage characteristics in wide bandgap semiconductor-electrolyte junctions

NASA Astrophysics Data System (ADS)

Frolov, D. S.; Zubkov, V. I.

2016-12-01

The frequency dispersion of capacitance-voltage characteristics and derived charge carrier concentration with application to the junction between an electrolyte and wide band-gap semiconductors are investigated. To expand the measurement frequency range, the precision LCR-meter Agilent E4980A was connected to the electrochemical cell ECVPro Nanometrics via a specially designed switch unit. The influence of series resistance and degree of dopant ionization on the frequency dispersion of CV-measured characteristics are discussed. It was shown that in wide band-gap semiconductors one can get both total and ionized dopant concentration, depending on the test frequency choice for capacitance measurements.

Dielectric capacitors with three-dimensional nanoscale interdigital electrodes for energy storage.

PubMed

Han, Fangming; Meng, Guowen; Zhou, Fei; Song, Li; Li, Xinhua; Hu, Xiaoye; Zhu, Xiaoguang; Wu, Bing; Wei, Bingqing

2015-10-01

Dielectric capacitors are promising candidates for high-performance energy storage systems due to their high power density and increasing energy density. However, the traditional approach strategies to enhance the performance of dielectric capacitors cannot simultaneously achieve large capacitance and high breakdown voltage. We demonstrate that such limitations can be overcome by using a completely new three-dimensional (3D) nanoarchitectural electrode design. First, we fabricate a unique nanoporous anodic aluminum oxide (AAO) membrane with two sets of interdigitated and isolated straight nanopores opening toward opposite planar surfaces. By depositing carbon nanotubes in both sets of pores inside the AAO membrane, the new dielectric capacitor with 3D nanoscale interdigital electrodes is simply realized. In our new capacitors, the large specific surface area of AAO can provide large capacitance, whereas uniform pore walls and hemispheric barrier layers can enhance breakdown voltage. As a result, a high energy density of 2 Wh/kg, which is close to the value of a supercapacitor, can be achieved, showing promising potential in high-density electrical energy storage for various applications.

Dielectric capacitors with three-dimensional nanoscale interdigital electrodes for energy storage

PubMed Central

Han, Fangming; Meng, Guowen; Zhou, Fei; Song, Li; Li, Xinhua; Hu, Xiaoye; Zhu, Xiaoguang; Wu, Bing; Wei, Bingqing

2015-01-01

Dielectric capacitors are promising candidates for high-performance energy storage systems due to their high power density and increasing energy density. However, the traditional approach strategies to enhance the performance of dielectric capacitors cannot simultaneously achieve large capacitance and high breakdown voltage. We demonstrate that such limitations can be overcome by using a completely new three-dimensional (3D) nanoarchitectural electrode design. First, we fabricate a unique nanoporous anodic aluminum oxide (AAO) membrane with two sets of interdigitated and isolated straight nanopores opening toward opposite planar surfaces. By depositing carbon nanotubes in both sets of pores inside the AAO membrane, the new dielectric capacitor with 3D nanoscale interdigital electrodes is simply realized. In our new capacitors, the large specific surface area of AAO can provide large capacitance, whereas uniform pore walls and hemispheric barrier layers can enhance breakdown voltage. As a result, a high energy density of 2 Wh/kg, which is close to the value of a supercapacitor, can be achieved, showing promising potential in high-density electrical energy storage for various applications. PMID:26601294

Load insensitive electrical device. [power converters for supplying direct current at one voltage from a source at another voltage

NASA Technical Reports Server (NTRS)

Schwarz, F. C. (Inventor)

1974-01-01

A class of power converters is described for supplying direct current at one voltage from a source at another voltage. It includes a simple passive circuit arrangement of solid-state switches, inductors, and capacitors by which the output voltage of the converter tends to remain constant in spite of changes in load. The switches are sensitive to the current flowing in the circuit and are employed to permit the charging of capacitance devices in accordance with the load requirements. Because solid-state switches (such as SCR's) may be used with relatively high voltage and because of the inherent efficiency of the invention that permits relatively high switching frequencies, power supplies built in accordance with the invention, together with their associated cabling, can be substantially lighter in weight for a given output power level and efficiency of operation than systems of the prior art.

A microfabricated fringing field capacitive pH sensor with an integrated readout circuit

NASA Astrophysics Data System (ADS)

Arefin, Md Shamsul; Bulut Coskun, M.; Alan, Tuncay; Redoute, Jean-Michel; Neild, Adrian; Rasit Yuce, Mehmet

2014-06-01

This work presents a microfabricated fringe-field capacitive pH sensor using interdigitated electrodes and an integrated modulation-based readout circuit. The changes in capacitance of the sensor result from the permittivity changes due to pH variations and are converted to frequency shifts using a crossed-coupled voltage controlled oscillator readout circuit. The shift in resonant frequency of the readout circuit is 30.96 MHz for a change in pH of 1.0-5.0. The sensor can be used for the measurement of low pH levels, such as gastric acid, and can be integrated with electronic pills. The measurement results show high repeatability, low noise, and a stable output.

Optical control of capacitance in a metal-insulator-semiconductor diode with embedded metal nanoparticles

NASA Astrophysics Data System (ADS)

Mikhelashvili, V.; Ankonina, G.; Kauffmann, Y.; Atiya, G.; Kaplan, W. D.; Padmanabhan, R.; Eisenstein, G.

2017-06-01

This paper describes a metal-insulator-semiconductor (MIS) capacitor with flat capacitance voltage characteristics and a small quadratic voltage capacitance coefficient. The device characteristics resemble a metal-insulator-metal diode except that here the capacitance depends on illumination and exhibits a strong frequency dispersion. The device incorporates Fe nanoparticles (NPs), mixed with SrF2, which are embedded in an insulator stack of SiO2 and HfO2. Positively charged Fe ions induce dipole type traps with an electronic polarization that is enhanced by photogenerated carriers injected from the substrate and/or by inter nanoparticle exchange of carriers. The obtained characteristics are compared with those of five other MIS structures: two based on Fe NPs, one with and the other without SrF2 sublayers. Additionally, devices contain Co NPs embedded in SrF2 sublayers, and finally, two structures have no NPs, with one based on a stack of SiO2 and HfO2 and the other which also includes SrF2. Only structures containing Fe NPs, which are incorporated into SrF2, yield a voltage independent capacitance, the level of which can be changed by illumination. These properties are essential in radio frequency/analog mixed signal applications.

Experimental investigation of mode transitions in asymmetric capacitively coupled radio-frequency Ne and CF4 plasmas

NASA Astrophysics Data System (ADS)

Liu, Gang-Hu; Liu, Yong-Xin; Bai, Li-Shui; Zhao, Kai; Wang, You-Nian

2018-02-01

The dependence of the electron density and the emission intensity on external parameters during the transitions of the electron power absorption mode is experimentally studied in asymmetric electropositive (neon) and electronegative (CF4) capacitively coupled radio-frequency plasmas. The spatio-temporal distribution of the emission intensity is measured with phase resolved optical emission spectroscopy and the electron density at the discharge center is measured by utilizing a floating hairpin probe. In neon discharge, the emission intensity increases almost linearly with the rf voltage at all driving frequencies covered here, while the variation of the electron density with the rf voltage behaves differently at different driving frequencies. In particular, the electron density increases linearly with the rf voltage at high driving frequencies, while at low driving frequencies the electron density increases slowly at the low-voltage side and, however, grows rapidly, when the rf voltage is higher than a certain value, indicating a transition from α to γ mode. The rf voltage, at which the mode transition occurs, increases with the decrease of the driving frequency/the working pressure. By contrast, in CF4 discharge, three different electron power absorption modes can be observed and the electron density and emission intensity do not exhibit a simple dependence on the rf voltage. In particular, the electron density exhibits a minimum at a certain rf voltage when the electron power absorption mode is switching from drift-ambipolar to the α/γ mode. A minimum can also be found in the emission intensity at a higher rf voltage when a discharge is switching into the γ mode.

Impact of GaN cap on charges in Al₂O₃/(GaN/)AlGaN/GaN metal-oxide-semiconductor heterostructures analyzed by means of capacitance measurements and simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ťapajna, M., E-mail: milan.tapajna@savba.sk; Jurkovič, M.; Válik, L.

2014-09-14

Oxide/semiconductor interface trap density (D{sub it}) and net charge of Al₂O₃/(GaN)/AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT) structures with and without GaN cap were comparatively analyzed using comprehensive capacitance measurements and simulations. D{sub it} distribution was determined in full band gap of the barrier using combination of three complementary capacitance techniques. A remarkably higher D{sub it} (∼5–8 × 10¹²eV⁻¹ cm⁻²) was found at trap energies ranging from E C-0.5 to 1 eV for structure with GaN cap compared to that (D{sub it} ∼ 2–3 × 10¹²eV⁻¹ cm⁻²) where the GaN cap was selectively etched away. D{sub it} distributions were then used for simulation of capacitance-voltage characteristics. A good agreement betweenmore » experimental and simulated capacitance-voltage characteristics affected by interface traps suggests (i) that very high D{sub it} (>10¹³eV⁻¹ cm⁻²) close to the barrier conduction band edge hampers accumulation of free electron in the barrier layer and (ii) the higher D{sub it} centered about E C-0.6 eV can solely account for the increased C-V hysteresis observed for MOS-HEMT structure with GaN cap. Analysis of the threshold voltage dependence on Al₂O₃ thickness for both MOS-HEMT structures suggests that (i) positive charge, which compensates the surface polarization, is not necessarily formed during the growth of III-N heterostructure, and (ii) its density is similar to the total surface polarization charge of the GaN/AlGaN barrier, rather than surface polarization of the top GaN layer only. Some constraints for the positive surface compensating charge are discussed.« less

Dioxythiophene-based polymer electrodes for supercapacitor modules.

PubMed

Liu, David Y; Reynolds, John R

2010-12-01

We report on the electrochemical and capacitive behaviors of poly(2,2-dimethyl-3,4-propylene-dioxythipohene) (PProDOT-Me2) films as polymeric electrodes in Type I electrochemical supercapacitors. The supercapacitor device displays robust capacitive charging/discharging behaviors with specific capacitance of 55 F/g, based on 60 μg of PProDOT-Me2 per electrode, that retains over 85% of its storage capacity after 32 000 redox cycles at 78% depth of discharge. Moreover, an appreciable average energy density of 6 Wh/kg has been calculated for the device, along with well-behaved and rapid capacitive responses to 1.0 V between 5 to 500 mV s(-1). Tandem electrochemical supercapacitors were assembled in series, in parallel, and in combinations of the two to widen the operating voltage window and to increase the capacitive currents. Four supercapacitors coupled in series exhibited a 4.0 V charging/discharging window, whereas assembly in parallel displayed a 4-fold increase in capacitance. Combinations of both serial and parallel assembly with six supercapacitors resulted in the extension of voltage to 3 V and a 2-fold increase in capacitive currents. Utilization of bipolar electrodes facilitated the encapsulation of tandem supercapacitors as individual, flexible, and lightweight supercapacitor modules.

Mapping Electrical Crosstalk in Pixelated Sensor Arrays

NASA Technical Reports Server (NTRS)

Seshadri, Suresh (Inventor); Cole, David (Inventor); Smith, Roger M. (Inventor); Hancock, Bruce R. (Inventor)

2017-01-01

The effects of inter pixel capacitance in a pixilated array may be measured by first resetting all pixels in the array to a first voltage, where a first image is read out, followed by resetting only a subset of pixels in the array to a second voltage, where a second image is read out, where the difference in the first and second images provide information about the inter pixel capacitance. Other embodiments are described and claimed.

Mapping Electrical Crosstalk in Pixelated Sensor Arrays

NASA Technical Reports Server (NTRS)

Smith, Roger M (Inventor); Hancock, Bruce R. (Inventor); Cole, David (Inventor); Seshadri, Suresh (Inventor)

2013-01-01

The effects of inter pixel capacitance in a pixilated array may be measured by first resetting all pixels in the array to a first voltage, where a first image is read out, followed by resetting only a subset of pixels in the array to a second voltage, where a second image is read out, where the difference in the first and second images provide information about the inter pixel capacitance. Other embodiments are described and claimed.

Fabrication and Properties of Multilayer Structures

DTIC Science & Technology

1982-08-01

22- The relative voltage supported in each semiconductor is V -V NAc b 1 A227) Vb2 V2 NDlcl where V = V1 + V2. It is apparent that Eqs. 5-7 will...has more difficulty because the interface state capacitance must be extracted from the measured capacitance. When a voltage is applied, the interface...contain identical information about interface states. However, as Nicollian and Goetzberger (6 ) have shown, greater inaccuracies arise in extracting

Optical and Electrical Performance of MOS-Structure Silicon Solar Cells with Antireflective Transparent ITO and Plasmonic Indium Nanoparticles under Applied Bias Voltage.

PubMed

Ho, Wen-Jeng; Sue, Ruei-Siang; Lin, Jian-Cheng; Syu, Hong-Jang; Lin, Ching-Fuh

2016-08-10

This paper reports impressive improvements in the optical and electrical performance of metal-oxide-semiconductor (MOS)-structure silicon solar cells through the incorporation of plasmonic indium nanoparticles (In-NPs) and an indium-tin-oxide (ITO) electrode with periodic holes (perforations) under applied bias voltage. Samples were prepared using a plain ITO electrode or perforated ITO electrode with and without In-NPs. The samples were characterized according to optical reflectance, dark current voltage, induced capacitance voltage, external quantum efficiency, and photovoltaic current voltage. Our results indicate that induced capacitance voltage and photovoltaic current voltage both depend on bias voltage, regardless of the type of ITO electrode. Under a bias voltage of 4.0 V, MOS cells with perforated ITO and plain ITO, respectively, presented conversion efficiencies of 17.53% and 15.80%. Under a bias voltage of 4.0 V, the inclusion of In-NPs increased the efficiency of cells with perforated ITO and plain ITO to 17.80% and 16.87%, respectively.

Optical and Electrical Performance of MOS-Structure Silicon Solar Cells with Antireflective Transparent ITO and Plasmonic Indium Nanoparticles under Applied Bias Voltage

PubMed Central

Ho, Wen-Jeng; Sue, Ruei-Siang; Lin, Jian-Cheng; Syu, Hong-Jang; Lin, Ching-Fuh

2016-01-01

This paper reports impressive improvements in the optical and electrical performance of metal-oxide-semiconductor (MOS)-structure silicon solar cells through the incorporation of plasmonic indium nanoparticles (In-NPs) and an indium-tin-oxide (ITO) electrode with periodic holes (perforations) under applied bias voltage. Samples were prepared using a plain ITO electrode or perforated ITO electrode with and without In-NPs. The samples were characterized according to optical reflectance, dark current voltage, induced capacitance voltage, external quantum efficiency, and photovoltaic current voltage. Our results indicate that induced capacitance voltage and photovoltaic current voltage both depend on bias voltage, regardless of the type of ITO electrode. Under a bias voltage of 4.0 V, MOS cells with perforated ITO and plain ITO, respectively, presented conversion efficiencies of 17.53% and 15.80%. Under a bias voltage of 4.0 V, the inclusion of In-NPs increased the efficiency of cells with perforated ITO and plain ITO to 17.80% and 16.87%, respectively. PMID:28773801

A novel gate and drain engineered charge plasma tunnel field-effect transistor for low sub-threshold swing and ambipolar nature

NASA Astrophysics Data System (ADS)

Yadav, Dharmendra Singh; Raad, Bhagwan Ram; Sharma, Dheeraj

2016-12-01

In this paper, we focus on the improvement of figures of merit for charge plasma based tunnel field-effect transistor (TFET) in terms of ON-state current, threshold voltage, sub-threshold swing, ambipolar nature, and gate to drain capacitance which provides better channel controlling of the device with improved high frequency response at ultra-low supply voltages. Regarding this, we simultaneously employ work function engineering on the drain and gate electrode of the charge plasma TFET. The use of gate work function engineering modulates the barrier on the source/channel interface leads to improvement in the ON-state current, threshold voltage, and sub-threshold swing. Apart from this, for the first time use of work function engineering on the drain electrode increases the tunneling barrier for the flow of holes on the drain/channel interface, it results into suppression of ambipolar behavior. The lowering of gate to drain capacitance therefore enhanced high frequency parameters. Whereas, the presence of dual work functionality at the gate electrode and over the drain region improves the overall performance of the charge plasma based TFET.

Coexistence of high performance resistance and capacitance memory based on multilayered metal-oxide structures

PubMed Central

Yan, Z. B.; Liu, J. -M.

2013-01-01

The Au/DyMnO3/Nb:SrTiO3/Au stack was demonstrated to be not only a high performance memristor but also a good memcapacitor. The switching time is below 10 ns, the retention is longer than 105 s, and the change ratio of resistance (or capacitance) is larger than 100 over the 108 switching cycles. Moreover, this stack has a broad range of intermediate states that are tunable by the operating voltages. It is indicated that the memory effects originate from the Nb:SrTiO3/Au junction where the barrier profile is electrically modulated. The serial connected Au/DyMnO3/Nb:SrTiO3 stack behaves as a high nonlinear resistor paralleling with a capacitor, which raises the capacitance change ratio and enhances the memory stability of the device. PMID:23963467

A precision analogue integrator system for heavy current measurement in MFDC resistance spot welding

NASA Astrophysics Data System (ADS)

Xia, Yu-Jun; Zhang, Zhong-Dian; Xia, Zhen-Xin; Zhu, Shi-Liang; Zhang, Rui

2016-02-01

In order to control and monitor the quality of middle frequency direct current (MFDC) resistance spot welding (RSW), precision measurement of the welding current up to 100 kA is required, for which Rogowski coils are the only viable current transducers at present. Thus, a highly accurate analogue integrator is the key to restoring the converted signals collected from the Rogowski coils. Previous studies emphasised that the integration drift is a major factor that influences the performance of analogue integrators, but capacitive leakage error also has a significant impact on the result, especially in long-time pulse integration. In this article, new methods of measuring and compensating capacitive leakage error are proposed to fabricate a precision analogue integrator system for MFDC RSW. A voltage holding test is carried out to measure the integration error caused by capacitive leakage, and an original integrator with a feedback adder is designed to compensate capacitive leakage error in real time. The experimental results and statistical analysis show that the new analogue integrator system could constrain both drift and capacitive leakage error, of which the effect is robust to different voltage levels of output signals. The total integration error is limited within  ±0.09 mV s-1 0.005% s-1 or full scale at a 95% confidence level, which makes it possible to achieve the precision measurement of the welding current of MFDC RSW with Rogowski coils of 0.1% accuracy class.

Temperature dependent quasi-static capacitance-voltage characterization of SiO2/β-Ga2O3 interface on different crystal orientations

NASA Astrophysics Data System (ADS)

Zeng, Ke; Singisetti, Uttam

2017-09-01

The interface trap density (Dit) of the SiO2/β-Ga2O3 interface in ( 2 ¯ 01), (010), and (001) orientations is obtained by the Hi-Lo method with the low frequency capacitance measured using the Quasi-Static Capacitance-Voltage (QSCV) technique. QSCV measurements are carried out at higher temperatures to increase the measured energy range of Dit in the bandgap. At room temperature, higher Dit is observed near the band edge for all three orientations. The measurement at higher temperatures led to an annealing effect that reduced the Dit value for all samples. Comparison with the conductance method and frequency dispersion of the capacitance suggests that the traps at the band edge are slow traps which respond to low frequency signals.

Carbon Nanotube Tape Vibrating Gyroscope

NASA Technical Reports Server (NTRS)

Tucker, Dennis Stephen (Inventor)

2016-01-01

A vibrating gyroscope includes a piezoelectric strip having length and width dimensions. The piezoelectric strip includes a piezoelectric material and carbon nanotubes (CNTs) substantially aligned and polled along the strip's length dimension. A spindle having an axis of rotation is coupled to the piezoelectric strip. The axis of rotation is parallel to the strip's width dimension. A first capacitance sensor is mechanically coupled to the spindle for rotation therewith. The first capacitance sensor is positioned at one of the strip's opposing ends and is spaced apart from one of the strip's opposing faces. A second capacitance sensor is mechanically coupled to the spindle for rotation therewith. The second capacitance sensor is positioned at another of the strip's opposing ends and is spaced apart from another of the strip's opposing faces. A voltage source applies an AC voltage to the piezoelectric strip.

Modulating capacitive response of MoS2 flake by controlled nanostructuring through focused laser irradiation.

PubMed

Rani, Renu; Kundu, Anirban; Balal, Mohammad; Sheet, Goutam; Hazra, Kiran Shankar

2018-08-24

Unlike graphene nanostructures, various physical properties of nanostructured MoS 2 have remained unexplored due to the lack of established fabrication routes. Herein, we have reported unique electrostatic properties of MoS 2 nanostructures, fabricated in a controlled manner of different geometries on 2D flake by using focused laser irradiation technique. Electrostatic force microscopy has been carried out on MoS 2 nanostructures by varying tip bias voltage and lift height. The analysis depicts no contrast flip in phase image of the patterned nanostructure due to the absence of free surface charges. However, prominent change in phase shift at the patterned area is observed. Such contrast changes signify the capacitive interaction between tip and nanostructures at varying tip bias voltage and lift height, irrespective of their shape and size. Such unperturbed capacitive behavior of the MoS 2 nanostructures offer modulation of capacitance in periodic array on 2D MoS 2 flake for potential application in capacitive devices.

Electrochemical performance of microporous and mesoporous activated carbons in neat and diluted 1-ethyl-3-methylimidazolium tetrafluoroborate

NASA Astrophysics Data System (ADS)

Kumagai, Seiji; Hatomi, Masaki; Tashima, Daisuke

2017-03-01

1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIm·BF4), neat and diluted with propylene carbonate to 1 mol L-1, have been employed as electrolytes of electrical double-layer capacitors (EDLCs). The effects of microporosity and mesoporosity in activated carbon (AC) electrodes on the capacitive and resistive performances upon the use of neat and diluted EMIm·BF4 have been explored. In addition to cyclic voltammetry and galvanostatic charge-discharge tests, electrochemical impedance spectroscopy has been performed employing Kang's equivalent circuit model consisting of three resistances, three constant phase elements, and one bounded Warburg impedance. The overall impedance of the EDLC cell was separated into components of intrinsic resistance, bulk electrolyte, diffusion layer, and Helmholtz layer. The specific capacitance and the equivalent series resistance (ESR) of mesoporous AC were found to be highly dependent on the rate of ionic transfer. Lower cell voltage was identified as being responsible for lower specific capacitance and larger ESR of mesoporous AC, which was similarly seen in the neat and diluted EMIm·BF4, and could be alleviated by increasing the cell voltage. The inferior rate performance and the cell-voltage-dependent performance of mesoporous AC, which were more distinctly observed in the neat EMIm·BF4, could be attributed to the lower mobility of EMIm+ and BF4- in mesopores.

High-mobility low-temperature ZnO transistors with low-voltage operation

NASA Astrophysics Data System (ADS)

Bong, Hyojin; Lee, Wi Hyoung; Lee, Dong Yun; Kim, Beom Joon; Cho, Jeong Ho; Cho, Kilwon

2010-05-01

Low voltage high mobility n-type thin film transistors (TFTs) based on sol-gel processed zinc oxide (ZnO) were fabricated using a high capacitance ion gel gate dielectric. The ion gel gated solution-processed ZnO TFTs were found to exhibit excellent electrical properties. TFT carrier mobilities were 13 cm2/V s, ON/OFF current ratios were 105, regardless of the sintering temperature used for the preparation of the ZnO thin films. Ion gel gated ZnO TFTs are successfully demonstrated on plastic substrates for the large area flexible electronics.

Time varying voltage combustion control and diagnostics sensor

DOEpatents

Chorpening, Benjamin T [Morgantown, WV; Thornton, Jimmy D [Morgantown, WV; Huckaby, E David [Morgantown, WV; Fincham, William [Fairmont, WV

2011-04-19

A time-varying voltage is applied to an electrode, or a pair of electrodes, of a sensor installed in a fuel nozzle disposed adjacent the combustion zone of a continuous combustion system, such as of the gas turbine engine type. The time-varying voltage induces a time-varying current in the flame which is measured and used to determine flame capacitance using AC electrical circuit analysis. Flame capacitance is used to accurately determine the position of the flame from the sensor and the fuel/air ratio. The fuel and/or air flow rate (s) is/are then adjusted to provide reduced flame instability problems such as flashback, combustion dynamics and lean blowout, as well as reduced emissions. The time-varying voltage may be an alternating voltage and the time-varying current may be an alternating current.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elizondo-Decanini, Juan M.; Coleman, Phillip D.; Moorman, Matthew W.

Low- and high-voltage Soliton waves were produced and used to demonstrate collision and compression using diode-based nonlinear transmission lines. Experiments demonstrate soliton addition and compression using homogeneous nonlinear lines. We built the nonlinear lines using commercially available diodes. These diodes are chosen after their capacitance versus voltage dependence is used in a model and the line design characteristics are calculated and simulated. Nonlinear ceramic capacitors are then used to demonstrate high-voltage pulse amplification and compression. The line is designed such that a simple capacitor discharge, input signal, develops soliton trains in as few as 12 stages. We also demonstrated outputmore » voltages in excess of 40 kV using Y5V-based commercial capacitors. The results show some key features that determine efficient production of trains of solitons in the kilovolt range.« less

Rectifying properties of p-GaN nanowires and an n-silicon heterojunction vertical diode.

PubMed

Manna, Sujit; Ashok, Vishal D; De, S K

2010-12-01

The heterojunction of a Pd-doped p-GaN nanowire and n-Si (100) is fabricated vertically by the vapor-liquid-solid method. The average diameter of the nanowire is 40 nm. The vertical junction reveals a significantly high rectification ratio of 10(3) at 5 V, a moderate ideality factor of ∼2, and a high breakdown voltage of ∼40 V. The charge transport across the p-n junction is dominated by the electron-hole recombination process. The voltage dependence of capacitance indicates a graded-type junction. The resistance of the junction decreases with an increase in the bias voltage confirmed by impedance measurements.

Hysteresis in Lanthanide Zirconium Oxides Observed Using a Pulse CV Technique and including the Effect of High Temperature Annealing.

PubMed

Lu, Qifeng; Zhao, Chun; Mu, Yifei; Zhao, Ce Zhou; Taylor, Stephen; Chalker, Paul R

2015-07-29

A powerful characterization technique, pulse capacitance-voltage (CV) technique, was used to investigate oxide traps before and after annealing for lanthanide zirconium oxide thin films deposited on n-type Si (111) substrates at 300 °C by liquid injection Atomic Layer Deposition (ALD). The results indicated that: (1) more traps were observed compared to the conventional capacitance-voltage characterization method in LaZrO x ; (2) the time-dependent trapping/de-trapping was influenced by the edge time, width and peak-to-peak voltage of a gate voltage pulse. Post deposition annealing was performed at 700 °C, 800 °C and 900 °C in N₂ ambient for 15 s to the samples with 200 ALD cycles. The effect of the high temperature annealing on oxide traps and leakage current were subsequently explored. It showed that more traps were generated after annealing with the trap density increasing from 1.41 × 10 12 cm -2 for as-deposited sample to 4.55 × 10 12 cm -2 for the 800 °C annealed one. In addition, the leakage current density increase from about 10 - ⁶ A/cm² at V g = +0.5 V for the as-deposited sample to 10 -3 A/cm² at V g = +0.5 V for the 900 °C annealed one.

Development of a novel configuration for a MEMS transducer for low bias and high resolution imaging applications

NASA Astrophysics Data System (ADS)

Emadi, Tahereh Arezoo; Buchanan, Douglas A.

2014-03-01

A robust capacitive micromachined ultrasonic transducer has been developed. In this novel configuration, a stack of two deflectable membranes are suspended over a fixed bottom electrode. Similar to conventional capacitive ultrasonic transducers, a generated electrostatic force between the electrodes causes the membranes to deflect and vibrate. However, in this new configuration the transducer effective cavity height is reduced due to the deflection of two membranes. Therefore, the transducer spring constant is more susceptible to bias voltage, which in return reduces the required bias voltage. The transducers have been produced employing a MEMS sacrificial technique where two different membrane anchoring (curved- and flat- anchors) structures, with similar membrane radii were fabricated. Highly doped polysilicon was used as the membrane material. The resonant frequencies of the two transducers have been investigated. It was found that the transducers with curved membrane anchors exhibits a larger resonant frequency shift compared to the transducers with flat membranes for a given bias voltage. Comparison has been made between the spring constant of the flat membrane transducer and that of a conventional single membrane transducer. It is shown that the multiple moving membrane transducer exhibits a larger reduction in the spring constant compared to the conventional transducer, when driven with the same bias voltage. This results in a transducer with a higher power generation capability and sensitivity.

Nonlinear standing wave excitation by series resonance-enhanced harmonics in low pressure capacitive discharges

NASA Astrophysics Data System (ADS)

Lieberman, M. A.; Lichtenberg, A. J.; Kawamura, Emi; Marakhtanov, A. M.

2015-09-01

It is well known that standing waves having radially center-high rf voltage profiles exist in high frequency capacitive discharges. It is also known that in radially uniform discharges, the capacitive sheath nonlinearities excite strong nonlinear series resonance harmonics that enhance the electron power deposition. In this work, we consider the coupling of the series resonance-enhanced harmonics to the standing waves. A one-dimensional, asymmetric radial transmission line model is developed incorporating the wave and nonlinear sheath physics and a self-consistent dc potential. The resulting coupled pde equation set is solved numerically to determine the discharge voltages and currents. A 10 mT argon base case is chosen with plasma density 2 ×1016 m-3, gap width 2 cm and conducting electrode radius 15 cm, driven by a high frequency 500 V source with source resistance 0.5 ohms. We find that nearby resonances lead to an enhanced ratio of 4.5 of the electron power per unit area on axis, compared to the average. The radial dependence of electron power with frequency shows significant variations, with the central enhancement and sharpness of the spatial resonances depending in a complicated way on the harmonic structure. Work supported by DOE Fusion Energy Science Contract DE-SC000193 and by a gift from the Lam Research Corporation.

Interfacial Ordering and Accompanying Divergent Capacitance at Ionic Liquid-Metal Interfaces.

PubMed

Limmer, David T

2015-12-18

A theory is constructed for dense ionic solutions near charged planar walls that is valid for strong interionic correlations. This theory predicts a fluctuation-induced, first-order transition and spontaneous charge density ordering at the interface, in the presence of an otherwise disordered bulk solution. The surface ordering is driven by applied voltage and results in an anomalous differential capacitance, in agreement with recent simulation results and consistent with experimental observations of a wide array of systems. Explicit forms for the charge density profile and capacitance are given. The theory is compared with numerical results for the charge frustrated Ising model, which is also found to exhibit a voltage driven first-order transition.

Interfacial Ordering and Accompanying Divergent Capacitance at Ionic Liquid-Metal Interfaces

NASA Astrophysics Data System (ADS)

Limmer, David T.

2015-12-01

A theory is constructed for dense ionic solutions near charged planar walls that is valid for strong interionic correlations. This theory predicts a fluctuation-induced, first-order transition and spontaneous charge density ordering at the interface, in the presence of an otherwise disordered bulk solution. The surface ordering is driven by applied voltage and results in an anomalous differential capacitance, in agreement with recent simulation results and consistent with experimental observations of a wide array of systems. Explicit forms for the charge density profile and capacitance are given. The theory is compared with numerical results for the charge frustrated Ising model, which is also found to exhibit a voltage driven first-order transition.

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors.

PubMed

Giusi, G; Giordano, O; Scandurra, G; Rapisarda, M; Calvi, S; Ciofi, C

2016-04-01

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz(1/2), while DC performances are limited only by the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giusi, G.; Giordano, O.; Scandurra, G.

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz{sup 1/2}, while DC performances are limited only bymore » the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.« less

Optimizing growth and post treatment of diamond for high capacitance neural interfaces.

PubMed

Tong, Wei; Fox, Kate; Zamani, Akram; Turnley, Ann M; Ganesan, Kumaravelu; Ahnood, Arman; Cicione, Rosemary; Meffin, Hamish; Prawer, Steven; Stacey, Alastair; Garrett, David J

2016-10-01

Electrochemical and biological properties are two crucial criteria in the selection of the materials to be used as electrodes for neural interfaces. For neural stimulation, materials are required to exhibit high capacitance and to form intimate contact with neurons for eliciting effective neural responses at acceptably low voltages. Here we report on a new high capacitance material fabricated using nitrogen included ultrananocrystalline diamond (N-UNCD). After exposure to oxygen plasma for 3 h, the activated N-UNCD exhibited extremely high electrochemical capacitance greater than 1 mF/cm(2), which originates from the special hybrid sp(2)/sp(3) structure of N-UNCD. The in vitro biocompatibility of the activated N-UNCD was then assessed using rat cortical neurons and surface roughness was found to be critical for healthy neuron growth, with best results observed on surfaces with a roughness of approximately 20 nm. Therefore, by using oxygen plasma activated N-UNCD with appropriate surface roughness, and considering the chemical and mechanical stability of diamond, the fabricated neural interfaces are expected to exhibit high efficacy, long-term stability and a healthy neuron/electrode interface. Copyright © 2016 Elsevier Ltd. All rights reserved.

Design of capacitive sensor for water level measurement

NASA Astrophysics Data System (ADS)

Qurthobi, A.; Iskandar, R. F.; Krisnatal, A.; Weldzikarvina

2016-11-01

Capacitive sensor for water level detection has been fabricated. It has, typically, high-impedance sensor, particularly at low frequencies, as clear from the impedance (reactance) expression for a capacitor. Also, capacitive sensor is a noncontacting device in the common usage. In this research, water level sensor based on capacitive principal created using two copper plates with height (h), width (b), and distance (l) between two plates, respectively, 0.040 m, 0.015 m, and 0.010 m. 5 V pp 3 kHz AC signal is used as input signal for the system. Dielectric constant between two plates is proportional to water level. Hence, it can be used to determine water level from electrical characteristic as it inversely proportional to sensor impedance. Linearization, inverting amplifier, and rectifier circuits are used as signal conditioning for the system. Based on conducted experiment, the relationship between water level (x), capacitance (C), and output voltage (Vdc ) can be expressed as C(x) = 2.756x + 0.333 nF and Vdc (x) = 15.755 + 0.316 V.

Pentacene-based metal-insulator-semiconductor memory structures utilizing single walled carbon nanotubes as a nanofloating gate

NASA Astrophysics Data System (ADS)

Sleiman, A.; Rosamond, M. C.; Alba Martin, M.; Ayesh, A.; Al Ghaferi, A.; Gallant, A. J.; Mabrook, M. F.; Zeze, D. A.

2012-01-01

A pentacene-based organic metal-insulator-semiconductor memory device, utilizing single walled carbon nanotubes (SWCNTs) for charge storage is reported. SWCNTs were embedded, between SU8 and polymethylmethacrylate to achieve an efficient encapsulation. The devices exhibit capacitance-voltage clockwise hysteresis with a 6 V memory window at ± 30 V sweep voltage, attributed to charging and discharging of SWCNTs. As the applied gate voltage exceeds the SU8 breakdown voltage, charge leakage is induced in SU8 to allow more charges to be stored in the SWCNT nodes. The devices exhibited high storage density (˜9.15 × 1011 cm-2) and demonstrated 94% charge retention due to the superior encapsulation.

The investigation of a compact auto-connected wire-wrapped pulsed transformer

NASA Astrophysics Data System (ADS)

Wang, Yuwei; Zhang, Jiande; Chen, Dongqun; Cao, Shengguang; Li, Da; Zhang, Tianyang

2012-05-01

For the power conditioning circuit used to deliver power efficiently from flux compression generator (FCG) to the load with high impedance, an air-cored and wire-wrapped transformer convenient in coaxial connection to the other parts is investigated. To reduce the size and enhance the performance, an auto-connection is adopted. A fast and simple model is used to calculate the electrical parameters of the transformer. To evaluate the high voltage capability, the voltages across turns and the electric field distribution in the transformer are investigated. The calculated and the measured electrical parameters of the transformer show good agreements. And the safe operating voltage is predicted to exceed 500 kV. In the preliminary experiments, the transformer is tested in a power conditioning circuit with a capacitive power supply. It is demonstrated that the output voltage of the transformer reaches -342 kV under the input voltage of -81 kV.

The investigation of a compact auto-connected wire-wrapped pulsed transformer.

PubMed

Wang, Yuwei; Zhang, Jiande; Chen, Dongqun; Cao, Shengguang; Li, Da; Zhang, Tianyang

2012-05-01

For the power conditioning circuit used to deliver power efficiently from flux compression generator (FCG) to the load with high impedance, an air-cored and wire-wrapped transformer convenient in coaxial connection to the other parts is investigated. To reduce the size and enhance the performance, an auto-connection is adopted. A fast and simple model is used to calculate the electrical parameters of the transformer. To evaluate the high voltage capability, the voltages across turns and the electric field distribution in the transformer are investigated. The calculated and the measured electrical parameters of the transformer show good agreements. And the safe operating voltage is predicted to exceed 500 kV. In the preliminary experiments, the transformer is tested in a power conditioning circuit with a capacitive power supply. It is demonstrated that the output voltage of the transformer reaches -342 kV under the input voltage of -81 kV.

Investigation of structural and electrical properties on substrate material for high frequency metal-oxide-semiconductor (MOS) devices

NASA Astrophysics Data System (ADS)

Kumar, M.; Yang, Sung-Hyun; Janardhan Reddy, K.; JagadeeshChandra, S. V.

2017-04-01

Hafnium oxide (HfO2) thin films were grown on cleaned P-type <1 0 0> Ge and Si substrates by using atomic layer deposition technique (ALD) with thickness of 8 nm. The composition analysis of as-deposited and annealed HfO2 films was characterized by XPS, further electrical measurements; we fabricated the metal-oxide-semiconductor (MOS) devices with Pt electrode. Post deposition annealing in O2 ambient at 500 °C for 30 min was carried out on both Ge and Si devices. Capacitance-voltage (C-V) and conductance-voltage (G-V) curves measured at 1 MHz. The Ge MOS devices showed improved interfacial and electrical properties, high dielectric constant (~19), smaller EOT value (0.7 nm), and smaller D it value as Si MOS devices. The C-V curves shown significantly high accumulation capacitance values from Ge devices, relatively when compare with the Si MOS devices before and after annealing. It could be due to the presence of very thin interfacial layer at HfO2/Ge stacks than HfO2/Si stacks conformed by the HRTEM images. Besides, from current-voltage (I-V) curves of the Ge devices exhibited similar leakage current as Si devices. Therefore, Ge might be a reliable substrate material for structural, electrical and high frequency applications.

"Negative capacitance" in resistor-ferroelectric and ferroelectric-dielectric networks: Apparent or intrinsic?

NASA Astrophysics Data System (ADS)

Saha, Atanu K.; Datta, Suman; Gupta, Sumeet K.

2018-03-01

In this paper, we describe and analytically substantiate an alternate explanation for the negative capacitance (NC) effect in ferroelectrics (FE). We claim that the NC effect previously demonstrated in resistance-ferroelectric (R-FE) networks does not necessarily validate the existence of "S" shaped relation between polarization and voltage (according to Landau theory). In fact, the NC effect can be explained without invoking the "S"-shaped behavior of FE. We employ an analytical model for FE (Miller model) in which the steady state polarization strictly increases with the voltage across the FE and show that despite the inherent positive FE capacitance, reduction in FE voltage with the increase in its charge is possible in a R-FE network as well as in a ferroelectric-dielectric (FE-DE) stack. This can be attributed to a large increase in FE capacitance near the coercive voltage coupled with the polarization lag with respect to the electric field. Under certain conditions, these two factors yield transient NC effect. We analytically derive conditions for NC effect in R-FE and FE-DE networks. We couple our analysis with extensive simulations to explain the evolution of NC effect. We also compare the trends predicted by the aforementioned Miller model with Landau-Khalatnikov (L-K) model (static negative capacitance due to "S"-shape behaviour) and highlight the differences between the two approaches. First, with an increase in external resistance in the R-FE network, NC effect shows a non-monotonic behavior according to Miller model but increases according to L-K model. Second, with the increase in ramp-rate of applied voltage in the FE-DE stack, NC effect increases according to Miller model but decreases according to L-K model. These results unveil a possible way to experimentally validate the actual reason of NC effect in FE.

Liquid Nitrogen as Fast High Voltage Switching Medium

NASA Astrophysics Data System (ADS)

Dickens, J.; Neuber, A.; Haustein, M.; Krile, J.; Krompholz, H.

2002-12-01

Compact pulsed power systems require new switching technologies. For high voltages, liquid nitrogen seems to be a suitable switching medium, with high hold-off voltage, low dielectric constant, and no need for pressurized systems as in high pressure gas switches. The discharge behavior in liquid nitrogen, such as breakdown voltages, formative times, current rise as function of voltage, recovery, etc. are virtually unknown, however. The phenomenology of breakdown in liquid nitrogen is investigated with high speed (temporal resolution < 1 ns) electrical and optical diagnostics, in a coaxial system with 50-Ohm impedance. Discharge current and voltage are determined with transmission line type current sensors and capacitive voltage dividers. The discharge luminosity is measured with photomultiplier tubes. Preliminary results of self-breakdown investigations (gap 1 mm, breakdown voltage 44 kV, non-boiling supercooled nitrogen) show a fast (2 ns) transition from an unknown current level to several mA, a long-duration (100 ns) phase with constant current superimposed by ns-spikes, and a final fast transition to the impedance limited current during several nanoseconds. The optical measurements will be expanded toward spectroscopy and high speed photography with the aim of clarifying the overall breakdown mechanisms, including electronic initiation, bubble formation, bubble dynamics, and their role in breakdown, for different electrode geometries (different macroscopic field enhancements).

Transition metal sulfides grown on graphene fibers for wearable asymmetric supercapacitors with high volumetric capacitance and high energy density

NASA Astrophysics Data System (ADS)

Cai, Weihua; Lai, Ting; Lai, Jianwei; Xie, Haoting; Ouyang, Liuzhang; Ye, Jianshan; Yu, Chengzhong

2016-06-01

Fiber shaped supercapacitors are promising candidates for wearable electronics because they are flexible and light-weight. However, a critical challenge of the widespread application of these energy storage devices is their low cell voltages and low energy densities, resulting in limited run-time of the electronics. Here, we demonstrate a 1.5 V high cell voltage and high volumetric energy density asymmetric fiber supercapacitor in aqueous electrolyte. The lightweight (0.24 g cm-3), highly conductive (39 S cm-1), and mechanically robust (221 MPa) graphene fibers were firstly fabricated and then coated by NiCo2S4 nanoparticles (GF/NiCo2S4) via the solvothermal deposition method. The GF/NiCo2S4 display high volumetric capacitance up to 388 F cm-3 at 2 mV s-1 in a three-electrode cell and 300 F cm-3 at 175.7 mA cm-3 (568 mF cm-2 at 0.5 mA cm-2) in a two-electrode cell. The electrochemical characterizations show 1000% higher capacitance of the GF/NiCo2S4 as compared to that of neat graphene fibers. The fabricated device achieves high energy density up to 12.3 mWh cm-3 with a maximum power density of 1600 mW cm-3, outperforming the thin-film lithium battery. Therefore, these supercapacitors are promising for the next generation flexible and wearable electronic devices.

Transition metal sulfides grown on graphene fibers for wearable asymmetric supercapacitors with high volumetric capacitance and high energy density

PubMed Central

Cai, Weihua; Lai, Ting; Lai, Jianwei; Xie, Haoting; Ouyang, Liuzhang; Ye, Jianshan; Yu, Chengzhong

2016-01-01

Fiber shaped supercapacitors are promising candidates for wearable electronics because they are flexible and light-weight. However, a critical challenge of the widespread application of these energy storage devices is their low cell voltages and low energy densities, resulting in limited run-time of the electronics. Here, we demonstrate a 1.5 V high cell voltage and high volumetric energy density asymmetric fiber supercapacitor in aqueous electrolyte. The lightweight (0.24 g cm−3), highly conductive (39 S cm−1), and mechanically robust (221 MPa) graphene fibers were firstly fabricated and then coated by NiCo2S4 nanoparticles (GF/NiCo2S4) via the solvothermal deposition method. The GF/NiCo2S4 display high volumetric capacitance up to 388 F cm−3 at 2 mV s−1 in a three-electrode cell and 300 F cm−3 at 175.7 mA cm−3 (568 mF cm−2 at 0.5 mA cm−2) in a two-electrode cell. The electrochemical characterizations show 1000% higher capacitance of the GF/NiCo2S4 as compared to that of neat graphene fibers. The fabricated device achieves high energy density up to 12.3 mWh cm−3 with a maximum power density of 1600 mW cm−3, outperforming the thin-film lithium battery. Therefore, these supercapacitors are promising for the next generation flexible and wearable electronic devices. PMID:27248510

Anomalous single-electron transfer in common-gate quadruple-dot single-electron devices with asymmetric junction capacitances

NASA Astrophysics Data System (ADS)

Imai, Shigeru; Ito, Masato

2018-06-01

In this paper, anomalous single-electron transfer in common-gate quadruple-dot turnstile devices with asymmetric junction capacitances is revealed. That is, the islands have the same total number of excess electrons at high and low gate voltages of the swing that transfers a single electron. In another situation, two electrons enter the islands from the source and two electrons leave the islands for the source and drain during a gate voltage swing cycle. First, stability diagrams of the turnstile devices are presented. Then, sequences of single-electron tunneling events by gate voltage swings are investigated, which demonstrate the above-mentioned anomalous single-electron transfer between the source and the drain. The anomalous single-electron transfer can be understood by regarding the four islands as “three virtual islands and a virtual source or drain electrode of a virtual triple-dot device”. The anomalous behaviors of the four islands are explained by the normal behavior of the virtual islands transferring a single electron and the behavior of the virtual electrode.

The Breakdown Characteristics of the Silicone Oil for Electric Power Apparatus

NASA Astrophysics Data System (ADS)

Yoshida, Hisashi; Yanabu, Satoru

The basic breakdown characteristics of the silicone oil as an insulating medium was studied with aim of realization of electric power apparatus which may be considered to be SF6 free and flame-retarding. As the first step, the impulse breakdown characteristics was measured with three kinds of electrodes whose electric field distributions differed. The breakdown characteristics in silicone oil was explained in relation to stressed oil volume (SOV) and the breakdown stress. At the second step the surface breakdown characteristic for impulse voltage was measured with two kinds of insulators which was set to between plane electrodes. The surface breakdown characteristic for impulse voltage was explained in relation to the ratio of the relative permittivity of oil and insulator. And on the third step, the breakdown characteristics of oil gap after interrupting small capacitive current was studied. In this experiment, the disconnecting switch to interrupt capacitive current was simulated by oil gap after interrupting impulse current, and to measure breakdown characteristics the high impulse voltage was subsequently applied. The breakdown stress in silicone oil after application of impulse current was discussed for insulation recovery characteristics.

Microscopic Theory of Supercapacitors

NASA Astrophysics Data System (ADS)

Skinner, Brian Joseph

As new energy technologies are designed and implemented, there is a rising demand for improved energy storage devices. At present the most promising class of these devices is the electric double-layer capacitor (EDLC), also known as the supercapacitor. A number of recently created supercapacitors have been shown to produce remarkably large capacitance, but the microscopic mechanisms that underlie their operation remain largely mysterious. In this thesis we present an analytical, microscopic-level theory of supercapacitors, and we explain how such large capacitance can result. Specifically, we focus on four types of devices that have been shown to produce large capacitance. The first is a capacitor composed of a clean, low-temperature two-dimensional electron gas adjacent to a metal gate electrode. Recent experiments have shown that such a device can produce capacitance as much as 40% larger than that of a conventional plane capacitor. We show that this enhanced capacitance can be understood as the result of positional correlations between electrons and screening by the gate electrode in the form of image charges. Thus, the enhancement of the capacitance can be understood primarily as a classical, electrostatic phenomenon. Accounting for the quantum mechanical properties of the electron gas provides corrections to the classical theory, and these are discussed. We also present a detailed numerical calculation of the capacitance of the system based on a calculation of the system's ground state energy using the variational principle. The variational technique that we develop is broadly applicable, and we use it here to make an accurate comparison to experiment and to discuss quantitatively the behavior of the electrons' correlation function. The second device discussed in this thesis is a simple EDLC composed of an ionic liquid between two metal electrodes. We adopt a simple description of the ionic liquid and show that for realistic parameter values the capacitance can be as much as three times larger than that of a plane capacitor with thickness equal to the ion diameter. As in the previous system, this large capacitance is the result of image charge formation in the metal electrode and positional correlations between discrete ions that comprise the electric double-layer. We show that the maximum capacitance scales with the temperature to the power -1/3, and that at moderately large voltage the capacitance also decays as the inverse one third power of voltage. These results are confirmed by a Monte Carlo simulation. The third type of device we consider is that of a porous supercapacitor, where the electrode is made from a conducting material with a dense arrangement of narrow, planar pores into which ionic liquid can enter when a voltage is applied. In this case we show that when the electrode is metallic the narrow pores aggressively screen the interaction between neighboring ions in a pore, leading to an interaction energy between ions that decays exponentially. This exponential interaction between ions allows the capacitance to be nearly an order of magnitude larger than what is predicted by mean-field theories. This result is confirmed by a Monte Carlo simulation. We also present a theory for the capacitance when the electrode is not a perfect metal, but has a finite electronic screening radius. When this screening radius is larger than the distance between pores, ions begin to interact across multiple pores and the capacitance is determined by the Yukawa-like interaction of a three-dimensional, correlated arrangement of ions. Finally, we consider the case of supercapacitor electrodes made from a stack of graphene sheets with randomly-inserted "spacer" molecules. For such devices, experiments have produced very large capacitance despite the small density of states of the electrode material, which would seem to imply poor screening of the ionic charge. We show that these large capacitance values can be understood as the result of collective entrance of ions into the graphene stack (GS) and the renormalization of the ionic charge produced by nonlinear screening. The collective behavior of ions results from the strong elastic energy associated with intercalated ions deforming the GS, which creates an effective attraction between them. The result is the formation of "disks" of charge that enter the electrode collectively and have their charge renormalized by the strong, nonlinear screening of the surrounding graphene layers. This renormalization leads to a capacitance that at small voltages increases linearly with voltage and is enhanced over mean-field predictions by a large factor proportional to the number of ions within the disk to the power 9/4. At large voltages, the capacitance is dictated by the physics of graphite intercalation compounds and is proportional to the voltage raised to the power -4/5. We also examine theoretically the case where the effective fine structure constant of the GS is a small parameter, and we uncover a wealth of scaling regimes.

Effect of driving voltages in dual capacitively coupled radio frequency plasma: A study by nonlinear global model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bora, B., E-mail: bbora@cchen.cl

2015-10-15

On the basis of nonlinear global model, a dual frequency capacitively coupled radio frequency plasma driven by 13.56 MHz and 27.12 MHz has been studied to investigate the influences of driving voltages on the generation of dc self-bias and plasma heating. Fluid equations for the ions inside the plasma sheath have been considered to determine the voltage-charge relations of the plasma sheath. Geometrically symmetric as well as asymmetric cases with finite geometrical asymmetry of 1.2 (ratio of electrodes area) have been considered to make the study more reasonable to experiment. The electrical asymmetry effect (EAE) and finite geometrical asymmetry is found tomore » work differently in controlling the dc self-bias. The amount of EAE has been primarily controlled by the phase angle between the two consecutive harmonics waveforms. The incorporation of the finite geometrical asymmetry in the calculations shift the dc self-bias towards negative polarity direction while increasing the amount of EAE is found to increase the dc self-bias in either direction. For phase angle between the two waveforms ϕ = 0 and ϕ = π/2, the amount of EAE increases significantly with increasing the low frequency voltage, whereas no such increase in the amount of EAE is found with increasing high frequency voltage. In contrast to the geometrically symmetric case, where the variation of the dc self-bias with driving voltages for phase angle ϕ = 0 and π/2 are just opposite in polarity, the variation for the geometrically asymmetric case is different for ϕ = 0 and π/2. In asymmetric case, for ϕ = 0, the dc self-bias increases towards the negative direction with increasing both the low and high frequency voltages, but for the ϕ = π/2, the dc-self bias is increased towards positive direction with increasing low frequency voltage while dc self-bias increases towards negative direction with increasing high frequency voltage.« less

Apparatus for producing voltage and current pulses

DOEpatents

Kirbie, Hugh; Dale, Gregory E.

2010-12-21

An apparatus having one or more modular stages for producing voltage and current pulses. Each module includes a diode charging means to charge a capacitive means that stores energy. One or more charging impedance means are connected to the diode charging means to provide a return current pathway. A solid-state switch discharge means, with current interruption capability, is connected to the capacitive means to discharge stored energy. Finally, a control means is provided to command the switching action of the solid-state switch discharge means.

Dual-mode self-validating resistance/Johnson noise thermometer system

DOEpatents

Shepard, Robert L.; Blalock, Theron V.; Roberts, Michael J.

1993-01-01

A dual-mode Johnson noise and DC resistance thermometer capable of use in control systems where prompt indications of temperature changes and long term accuracy are needed. A resistance-inductance-capacitance (RLC) tuned circuit produces a continuous voltage signal for Johnson noise temperature measurement. The RLC circuit provides a mean-squared noise voltage that depends only on the capacitance used and the temperature of the sensor. The sensor has four leads for simultaneous coupling to a noise signal processor and to a DC resistance signal processor.

Simulation of Dual-Electrode Capacitively Coupled Plasma Discharges

NASA Astrophysics Data System (ADS)

Lu, Yijia; Ji, Linhong; Cheng, Jia

2016-12-01

Dual-electrode capacitively coupled plasma discharges are investigated here to lower the non-uniformity of plasma density. The dual-electrode structure proposed by Jung splits the electrode region and increases the flexibility of fine tuning non-uniformity. Different RF voltages, frequencies, phase-shifts and electrode areas are simulated and the influences are discussed. RF voltage and electrode area have a non-monotonic effect on non-uniformity, while frequency has a monotonic effect. Phase-shift has a cyclical influence on non-uniformity. A special combination of 224 V voltage and 11% area ratio with 10 MHz lowers the non-uniformity of the original set (200 V voltage and 0% area ratio with 10 MHz) by 46.5%. The position of the plasma density peak at the probe line has been tracked and properly tuning the phase-shift can obtain the same trace as tuning frequency or voltage. supported by National Natural Science Foundation of China (No. 51405261)

Exceptionally High Electric Double Layer Capacitances of Oligomeric Ionic Liquids.

PubMed

Matsumoto, Michio; Shimizu, Sunao; Sotoike, Rina; Watanabe, Masayoshi; Iwasa, Yoshihiro; Itoh, Yoshimitsu; Aida, Takuzo

2017-11-15

Electric double layer (EDL) capacitors are promising as next-generation energy accumulators if their capacitances and operation voltages are both high. However, only few electrolytes can simultaneously fulfill these two requisites. Here we report that an oligomeric ionic liquid such as IL4 TFSI with four imidazolium ion units in its structure provides a wide electrochemical window of ∼5.0 V, similar to monomeric ionic liquids. Furthermore, electrochemical impedance measurements using Au working electrodes demonstrated that IL4 TFSI exhibits an exceptionally high EDL capacitance of ∼66 μF/cm 2 , which is ∼6 times as high as those of monomeric ionic liquids so far reported. We also found that an EDL-based field effect transistor (FET) using IL4 TFSI as a gate dielectric material and SrTiO 3 as a channel material displays a very sharp transfer curve with an enhanced carrier accumulation capability of ∼64 μF/cm 2 , as determined by Hall-effect measurements.

Influence of nonelectrostatic ion-ion interactions on double-layer capacitance

NASA Astrophysics Data System (ADS)

Zhao, Hui

2012-11-01

Recently a Poisson-Helmholtz-Boltzmann (PHB) model [Bohinc , Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.031130 85, 031130 (2012)] was developed by accounting for solvent-mediated nonelectrostatic ion-ion interactions. Nonelectrostatic interactions are described by a Yukawa-like pair potential. In the present work, we modify the PHB model by adding steric effects (finite ion size) into the free energy to derive governing equations. The modified PHB model is capable of capturing both ion specificity and ion crowding. This modified model is then employed to study the capacitance of the double layer. More specifically, we focus on the influence of nonelectrostatic ion-ion interactions on charging a double layer near a flat surface in the presence of steric effects. We numerically compute the differential capacitance as a function of the voltage under various conditions. At small voltages and low salt concentrations (dilute solution), we find out that the predictions from the modified PHB model are the same as those from the classical Poisson-Boltzmann theory, indicating that nonelectrostatic ion-ion interactions and steric effects are negligible. At moderate voltages, nonelectrostatic ion-ion interactions play an important role in determining the differential capacitance. Generally speaking, nonelectrostatic interactions decrease the capacitance because of additional nonelectrostatic repulsion among excess counterions inside the double layer. However, increasing the voltage gradually favors steric effects, which induce a condensed layer with crowding of counterions near the electrode. Accordingly, the predictions from the modified PHB model collapse onto those computed by the modified Poisson-Boltzmann theory considering steric effects alone. Finally, theoretical predictions are compared and favorably agree with experimental data, in particular, in concentrated solutions, leading one to conclude that the modified PHB model adequately predicts the diffuse-charge dynamics of the double layer with ion specificity and steric effects.

Capacitor-Chain Successive-Approximation ADC

NASA Technical Reports Server (NTRS)

Cunningham, Thomas

2003-01-01

A proposed successive-approximation analog-to-digital converter (ADC) would contain a capacitively terminated chain of identical capacitor cells. Like a conventional successive-approximation ADC containing a bank of binary-scaled capacitors, the proposed ADC would store an input voltage on a sample-and-hold capacitor and would digitize the stored input voltage by finding the closest match between this voltage and a capacitively generated sum of binary fractions of a reference voltage (Vref). However, the proposed capacitor-chain ADC would offer two major advantages over a conventional binary-scaled-capacitor ADC: (1) In a conventional ADC that digitizes to n bits, the largest capacitor (representing the most significant bit) must have 2(exp n-1) times as much capacitance, and hence, approximately 2(exp n-1) times as much area as does the smallest capacitor (representing the least significant bit), so that the total capacitor area must be 2(exp n) times that of the smallest capacitor. In the proposed capacitor-chain ADC, there would be three capacitors per cell, each approximately equal to the smallest capacitor in the conventional ADC, and there would be one cell per bit. Therefore, the total capacitor area would be only about 3(exp n) times that of the smallest capacitor. The net result would be that the proposed ADC could be considerably smaller than the conventional ADC. (2) Because of edge effects, parasitic capacitances, and manufacturing tolerances, it is difficult to make capacitor banks in which the values of capacitance are scaled by powers of 2 to the required precision. In contrast, because all the capacitors in the proposed ADC would be identical, the problem of precise binary scaling would not arise.

Energy breakdown in capacitive deionization.

PubMed

Hemmatifar, Ali; Palko, James W; Stadermann, Michael; Santiago, Juan G

2016-11-01

We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages. We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). We show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

Energy breakdown in capacitive deionization

DOE PAGES

Hemmatifar, Ali; Palko, James W.; Stadermann, Michael; ...

2016-08-12

We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages.more » We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). As a result, we show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency.« less

Non-mean-field theory of anomalously large double layer capacitance

NASA Astrophysics Data System (ADS)

Loth, M. S.; Skinner, Brian; Shklovskii, B. I.

2010-07-01

Mean-field theories claim that the capacitance of the double layer formed at a metal/ionic conductor interface cannot be larger than that of the Helmholtz capacitor, whose width is equal to the radius of an ion. However, in some experiments the apparent width of the double layer capacitor is substantially smaller. We propose an alternate non-mean-field theory of the ionic double layer to explain such large capacitance values. Our theory allows for the binding of discrete ions to their image charges in the metal, which results in the formation of interface dipoles. We focus primarily on the case where only small cations are mobile and other ions form an oppositely charged background. In this case, at small temperature and zero applied voltage dipoles form a correlated liquid on both contacts. We show that at small voltages the capacitance of the double layer is determined by the transfer of dipoles from one electrode to the other and is therefore limited only by the weak dipole-dipole repulsion between bound ions so that the capacitance is very large. At large voltages the depletion of bound ions from one of the capacitor electrodes triggers a collapse of the capacitance to the much smaller mean-field value, as seen in experimental data. We test our analytical predictions with a Monte Carlo simulation and find good agreement. We further argue that our “one-component plasma” model should work well for strongly asymmetric ion liquids. We believe that this work also suggests an improved theory of pseudocapacitance.

Nanostructure selenium compounds as pseudocapacitive electrodes for high-performance asymmetric supercapacitor.

PubMed

Ma, Guofu; Hua, Fengting; Sun, Kanjun; Fenga, Enke; Peng, Hui; Zhang, Zhiguo; Lei, Ziqiang

2018-01-01

The electrochemical performance of an energy conversion and storage device like the supercapacitor mainly depends on the microstructure and morphology of the electrodes. In this paper, to improve the capacitance performance of the supercapacitor, the all-pseudocapacitive electrodes of lamella-like Bi 18 SeO 29 /BiSe as the negative electrode and flower-like Co 0.85 Se nanosheets as the positive electrode are synthesized by using a facile low-temperature one-step hydrothermal method. The microstructures and morphology of the electrode materials are carefully characterized, and the capacitance performances are also tested. The Bi 18 SeO 29 /BiSe and Co 0.85 Se have high specific capacitance (471.3 F g -1 and 255 F g -1 at 0.5 A g -1 ), high conductivity, outstanding cycling stability, as well as good rate capability. The assembled asymmetric supercapacitor completely based on the pseudocapacitive electrodes exhibits outstanding cycling stability (about 93% capacitance retention after 5000 cycles). Moreover, the devices exhibit high energy density of 24.2 Wh kg -1 at a power density of 871.2 W kg -1 in the voltage window of 0-1.6 V with 2 M KOH solution.

Memory characteristics of metal-oxide-semiconductor structures based on Ge nanoclusters-embedded GeO(x) films grown at low temperature.

PubMed

Lin, Tzu-Shun; Lou, Li-Ren; Lee, Ching-Ting; Tsai, Tai-Cheng

2012-03-01

The memory devices constructed from the Ge-nanoclusters embedded GeO(x) layer deposited by the laser-assisted chemical vapor deposition (LACVD) system were fabricated. The Ge nanoclusters were observed by a high-resolution transmission electron microscopy. Using the capacitance versus voltage (C-V) and the conductance versus voltage (G-V) characteristics measured under various frequencies, the memory effect observed in the C-V curves was dominantly attributed to the charge storage in the Ge nanoclusters. Furthermore, the defects existed in the deposited film and the interface states were insignificant to the memory performances. Capacitance versus time (C-t) measurement was also executed to evaluate the charge retention characteristics. The charge storage and retention behaviors of the devices demonstrated that the Ge nanoclusters grown by the LACVD system at low temperature are promising for memory device applications.

A voltage-controlled capacitive discharge method for electrical activation of peripheral nerves.

PubMed

Rosellini, Will M; Yoo, Paul B; Engineer, Navzer; Armstrong, Scott; Weiner, Richard L; Burress, Chester; Cauller, Larry

2011-01-01

A voltage-controlled capacitive discharge (VCCD) method was investigated as an alternative to rectangular stimulus pulses currently used in peripheral nerve stimulation therapies.  In two anesthetized Gottingen mini pigs, the threshold (total charge per phase) for evoking a compound nerve action potential (CNAP) was compared between constant current (CC) and VCCD methods. Electrical pulses were applied to the tibial and posterior cutaneous femoralis nerves using standard and modified versions of the Medtronic 3778 Octad.  In contrast to CC stimulation, the combined application of VCCD pulses with a modified Octad resulted in a marked decrease (-73 ± 7.4%) in the stimulation threshold for evoking a CNAP. This was consistent for different myelinated fiber types and locations of stimulation.  The VCCD method provides a highly charge-efficient means of activating myelinated fibers that could potentially be used within a wireless peripheral nerve stimulator system. © 2011 International Neuromodulation Society.

Annealing effects on capacitance-voltage characteristics of a-Si/SiN(x) multilayer prepared using hot-wire chemical vapour deposition.

PubMed

Panchal, A K; Rai, D K; Solanki, C S

2011-04-01

Post-deposition annealing of a-Si/SiN(x) multilayer films at different temperature shows varying shift in high frequency (1 MHz) capacitance-voltage (HFCV) characteristics. Various a-Si/SiN(x) multilayer films were deposited using hot wire chemical vapor deposition (HWCVD) and annealed in the temperature range of 800 to 900 degrees C to precipitate Si quantum dots (Si-QD) in a-Si layers. HFCV measurements of the as-deposited and annealed films in metal-insulator-semiconductor (MIS) structures show hysterisis in C-V curves. The hysteresis in the as-deposited films and annealed films is attributed to charge trapping in Si-dangling bonds in a-Si layer and in Si-QD respectively. The charge trapping density in Si-QD increases with temperature while the interface defects density (D(it)) remains constant.

Efficiency and weight of voltage multiplier type ultra lightweight dc-dc converters

NASA Technical Reports Server (NTRS)

Harrigill, W. T., Jr.; Myers, I. T.

1975-01-01

An analytical and experimental study was made of a capacitor-diode voltage multiplier without a transformer which offers the possibility of high efficiency with light weight. The dc-dc conversion efficiencies of about 94 percent were achieved at output powers of 150 watts at 1000 volts using 8x multiplication. A detailed identification of losses was made, including forward drop losses in component, switching losses, reverse junction capacitance charging losses, and charging losses in the main ladder capacitors.

Stretchable V2O5/PEDOT supercapacitors: a modular fabrication process and charging with triboelectric nanogenerators.

PubMed

Qi, Ruijie; Nie, Jinhui; Liu, Mingyang; Xia, Mengyang; Lu, Xianmao

2018-04-26

Stretchable energy storage devices are of great importance for the viable applications of wearable/stretchable electronics. Studies on stretchable energy storage devices, especially supercapacitors (SCs), have shown encouraging progress. However, challenges still remain in the pursuit of high specific capacitances and facile fabrication methods. Herein, we report a modular materials fabrication and assembly process for stretchable SCs. With a V2O5/PEDOT composite as the active material, the resulting stretchable SCs exhibited high areal specific capacitances up to 240 mF cm-2 and good capacitance retention at a strain of 50%. To demonstrate the facile assembly process, a stretchable wristband was fabricated by simply assembling SC cells in series to deliver a voltage higher than 2 V. Charging the wristband with a triboelectric nanogenerator (TENG) to light an LED was further demonstrated, indicating the potential to integrate our SCs with environmental energy harvesters for self-powered stretchable devices.

Note: Compact high voltage pulse transformer made using a capacitor bank assembled in the shape of primary.

PubMed

Shukla, Rohit; Banerjee, Partha; Sharma, Surender K; Das, Rashmita; Deb, Pankaj; Prabaharan, T; Das, Basanta; Adhikary, Biswajit; Verma, Rishi; Shyam, Anurag

2011-10-01

The experimental results of an air-core pulse transformer are presented, which is very compact (<10 Kg in weight) and is primed by a capacitor bank that is fabricated in such a way that the capacitor bank with its switch takes the shape of single-turn rectangular shaped primary of the transformer. A high voltage capacitor assembly (pulse-forming-line capacitor, PFL) of 5.1 nF is connected with the secondary of transformer. The transformer output voltage is 160 kV in its second peak appearing in less than 2 μS from the beginning of the capacitor discharge. The primary capacitor bank can be charged up to a maximum of 18 kV, with the voltage delivery of 360 kV in similar capacitive loads.

Soliton production with nonlinear homogeneous lines

DOE PAGES

Elizondo-Decanini, Juan M.; Coleman, Phillip D.; Moorman, Matthew W.; ...

2015-11-24

Low- and high-voltage Soliton waves were produced and used to demonstrate collision and compression using diode-based nonlinear transmission lines. Experiments demonstrate soliton addition and compression using homogeneous nonlinear lines. We built the nonlinear lines using commercially available diodes. These diodes are chosen after their capacitance versus voltage dependence is used in a model and the line design characteristics are calculated and simulated. Nonlinear ceramic capacitors are then used to demonstrate high-voltage pulse amplification and compression. The line is designed such that a simple capacitor discharge, input signal, develops soliton trains in as few as 12 stages. We also demonstrated outputmore » voltages in excess of 40 kV using Y5V-based commercial capacitors. The results show some key features that determine efficient production of trains of solitons in the kilovolt range.« less

The effect of radio-frequency self bias on ion acceleration in expanding argon plasmas in helicon sources

NASA Astrophysics Data System (ADS)

Wiebold, Matthew D.

Time-averaged plasma potential differences up to ˜ 165 V over several hundred Debye lengths are observed in low pressure (pn < 1 mTorr) expanding argon plasmas in the Madison Helicon Experiment. The potential gradient leads to ion acceleration exceeding Ei ≈ 7 kTe in some cases. Up to 1 kW of 13.56 MHz RF power is supplied to a half-turn, double-helix antenna in the presence of a nozzle magnetic field up to 1 kG. An RPA measures the IEDF and an emissive probe measures the plasma potential. Single and double probes measure the electron density and temperature. Two distinct mode hops, the capacitive-inductive (E-H) and inductive-helicon (H-W) transitions, are identified by jumps in electron density as RF power is increased. In the capacitive mode, large fluctuations of the plasma potential (Vp--p ≳ 140 V, Vp--p/Vp ≈ 150%) exist at the RF frequency, leading to formation of a self-bias voltage. The mobile electrons can flow from the upstream region during an RF cycle whereas ions cannot, leading to an initial imbalance of flux, and the self-bias voltage builds as a result. The plasma potential in the expansion chamber is held near the floating potential for argon (Vp ≈ 5kTe/e). In the capacitive mode, the ion acceleration is not well described by an ambipolar relation. The accelerated population decay is consistent with that predicted by charge-exchange collisions. Grounding the upstream endplate increases the self-bias voltage compared to a floating endplate. In the inductive and helicon modes, the ion acceleration more closely follows an ambipolar relation, a result of decreased capacitive coupling due to the decreased RF skin depth. The scaling of the potential gradient with the argon flow rate, magnetic field and RF power are investigated, with the highest potential gradients observed for the lowest flow rates in the capacitive mode. The magnitude of the self-bias voltage agrees well with that predicted for RF sheaths. Use of the self-bias effect in a plasma thruster is explored, possibly for a low thrust, high specific impulse mode in a multi-mode helicon thruster. This work could also explain similar potential gradients in expanding helicon plasmas that are ascribed to double layer formation in the literature.

Electrical Properties and Power Considerations of a Piezoelectric Actuator

NASA Technical Reports Server (NTRS)

Jordan, T.; Ounaies, Z.; Tripp, J.; Tcheng, P.

1999-01-01

This paper assesses the electrical characteristics of piezoelectric wafers for use in aeronautical applications such as active noise control in aircraft. Determination of capacitive behavior and power consumption is necessary to optimize the system configuration and to design efficient driving electronics. Empirical relations are developed from experimental data to predict the capacitance and loss tangent of a PZT5A ceramic as nonlinear functions of both applied peak voltage and driving frequency. Power consumed by the PZT is the rate of energy required to excite the piezoelectric system along with power dissipated due to dielectric loss and mechanical and structural damping. Overall power consumption is thus quantified as a function of peak applied voltage and driving frequency. It was demonstrated that by incorporating the variation of capacitance and power loss with voltage and frequency, satisfactory estimates of power requirements can be obtained. These relations allow general guidelines in selection and application of piezoelectric actuators and driving electronics for active control applications.

Direct Current Contamination of Kilohertz Frequency Alternating Current Waveforms

PubMed Central

Franke, Manfred; Bhadra, Niloy; Bhadra, Narendra; Kilgore, Kevin

2014-01-01

Kilohertz Frequency Alternating Current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current- and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage- and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms. PMID:24820914

ANSYS simulation of the capacitance coupling of quartz tuning fork gyroscope

NASA Astrophysics Data System (ADS)

Zhang, Qing; Feng, Lihui; Zhao, Ke; Cui, Fang; Sun, Yu-nan

2013-12-01

Coupling error is one of the main error sources of the quartz tuning fork gyroscope. The mechanism of capacitance coupling error is analyzed in this article. Finite Element Method (FEM) is used to simulate the structure of the quartz tuning fork by ANSYS software. The voltage output induced by the capacitance coupling is simulated with the harmonic analysis and characteristics of electrical and mechanical parameters influenced by the capacitance coupling between drive electrodes and sense electrodes are discussed with the transient analysis.

Fluctuation spectra in the NASA Lewis bumpy-torus plasma

NASA Technical Reports Server (NTRS)

Singh, C. M.; Krawczonek, W. M.; Roth, J. R.; Hong, J. Y.; Powers, E. J.

1978-01-01

The electrostatic potential fluctuation spectrum in the NASA Lewis bumpy-torus plasma was studied with capacitive probes in the low pressure (high impedance) mode and in the high pressure (low impedance) mode. Under different operating conditions, the plasma exhibited electrostatic potential fluctuations (1) at a set of discrete frequencies, (2) at a continuum of frequencies, and (3) as incoherent high-frequency turbulence. The frequencies and azimuthal wave numbers were determined from digitally implemented autopower and cross-power spectra. The azimuthal dispersion characteristics of the unstable waves were examined by varying the electrode voltage, the polarity of the voltage, and the neutral background density at a constant magnetic field strength.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasper, M.; Gramse, G.; Hoffmann, J.

We measured the DC and RF impedance characteristics of micrometric metal-oxide-semiconductor (MOS) capacitors and Schottky diodes using scanning microwave microscopy (SMM). The SMM consisting of an atomic force microscopy (AFM) interfaced with a vector network analyser (VNA) was used to measure the reflection S11 coefficient of the metallic MOS and Schottky contact pads at 18 GHz as a function of the tip bias voltage. By controlling the SMM biasing conditions, the AFM tip was used to bias the Schottky contacts between reverse and forward mode. In reverse bias direction, the Schottky contacts showed mostly a change in the imaginary part ofmore » the admittance while in forward bias direction the change was mostly in the real part of the admittance. Reference MOS capacitors which are next to the Schottky diodes on the same sample were used to calibrate the SMM S11 data and convert it into capacitance values. Calibrated capacitance between 1–10 fF and 1/C{sup 2} spectroscopy curves were acquired on the different Schottky diodes as a function of the DC bias voltage following a linear behavior. Additionally, measurements were done directly with the AFM-tip in contact with the silicon substrate forming a nanoscale Schottky contact. Similar capacitance-voltage curves were obtained but with smaller values (30–300 aF) due to the corresponding smaller AFM-tip diameter. Calibrated capacitance images of both the MOS and Schottky contacts were acquired with nanoscale resolution at different tip-bias voltages.« less

Effect of UV lamp irradiation during oxidation of Zr/Pt/Si structure on electrical properties of Pt/ZrO 2/Pt/Si structure

NASA Astrophysics Data System (ADS)

Bae, Joon Woo; Lim, Jae-Won; Mimura, Kouji; Uchikoshi, Masahito; Miyazaki, Takamichi; Isshiki, Minoru

2010-03-01

Metal-insulator-metal (MIM) capacitors were fabricated using ZrO 2 films and the effects of structural and native defects of the ZrO 2 films on the electrical and dielectric properties were investigated. For preparing ZrO 2 films, Zr films were deposited on Pt/Si substrates by ion beam deposition (IBD) system with/without substrate bias voltages and oxidized at 200 °C for 60 min under 0.1 MPa O 2 atmosphere with/without UV light irradiation ( λ = 193 nm, Deep UV lamp). The ZrO 2(˜12 nm) films on Pt(˜100 nm)/Si were characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM), capacitance-voltage ( C- V) and current-voltage ( I- V) measurements were carried out on MIM structures. ZrO 2 films, fabricated by oxidizing the Zr film deposited with substrate bias voltage under UV light irradiation, show the highest capacitance (784 pF) and the lowest leakage current density. The active oxygen species formed by UV irradiation are considered to play an important role in the reduction of the leakage current density, because they can reduce the density of oxygen vacancies.

Rational hybrid modulation of P, N dual-doped holey graphene for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Nazarian-Samani, Masoud; Haghighat-Shishavan, Safa; Nazarian-Samani, Mahboobeh; Kim, Myeong-Seong; Cho, Byung-Won; Oh, Si-Hyoung; Kashani-Bozorg, Seyed Farshid; Kim, Kwang-Bum

2017-12-01

A P, N dual-doped holey graphene (PNHG) material is prepared by a scalable, facile synthetic approach, using a mixture of glucose, dicyandiamide (DCDA), and phosphoric acid (H3PO4). H3PO4 successfully functions as an "acid catalyst" to encourage the uniform breakage of C=C bonds to create large, localized perforations over the graphene monolith. Further acid treatment and annealing introduce in-plane holes. The correlation between the capacitance of the PNHG and its structural parameters during the fabrication process is comprehensively evaluated. A thermally induced sp2→sp3 transformation occurs at high temperatures because of the substantial loss of graphitic sp2-type carbons, together with a dramatic reduction in capacitance. The target PNHG-400 electrode material delivers exceptionally high gravimetric capacitance (235.5 F g-1 at 0.5 A g-1), remarkable rate capability (84.8% at 70 A g-1), superior capacitance retention (93.2 and 92.7% at 10 and 50 A g-1 over 25000 cycles, respectively), and acceptable volumetric capacitance due to moderate density, when it is used with organic electrolytes in the voltage range between 0 and 3 V. These results suggest a pioneering defect-engineered strategy to fabricate dual-doped holey graphene with valuable structural properties for high-performance electric double layer supercapacitors, which could be used in next-generation energy storage applications.

Switching power pulse system

DOEpatents

Aaland, K.

1983-08-09

A switching system for delivering pulses of power from a source to a load using a storage capacitor charged through a rectifier, and maintained charged to a reference voltage level by a transistor switch and voltage comparator. A thyristor is triggered to discharge the storage capacitor through a saturable reactor and fractional turn saturable transformer having a secondary to primary turn ratio N of n:l/n = n[sup 2]. The saturable reactor functions as a soaker'' while the thyristor reaches saturation, and then switches to a low impedance state. The saturable transformer functions as a switching transformer with high impedance while a load coupling capacitor charges, and then switches to a low impedance state to dump the charge of the storage capacitor into the load through the coupling capacitor. The transformer is comprised of a multilayer core having two secondary windings tightly wound and connected in parallel to add their output voltage and reduce output inductance, and a number of single turn windings connected in parallel at nodes for the primary winding, each single turn winding linking a different one of the layers of the multilayer core. The load may be comprised of a resistive beampipe for a linear particle accelerator and capacitance of a pulse forming network. To hold off discharge of the capacitance until it is fully charged, a saturable core is provided around the resistive beampipe to isolate the beampipe from the capacitance until it is fully charged. 5 figs.

Triple voltage dc-to-dc converter and method

DOEpatents

Su, Gui-Jia

2008-08-05

A circuit and method of providing three dc voltage buses and transforming power between a low voltage dc converter and a high voltage dc converter, by coupling a primary dc power circuit and a secondary dc power circuit through an isolation transformer; providing the gating signals to power semiconductor switches in the primary and secondary circuits to control power flow between the primary and secondary circuits and by controlling a phase shift between the primary voltage and the secondary voltage. The primary dc power circuit and the secondary dc power circuit each further comprising at least two tank capacitances arranged in series as a tank leg, at least two resonant switching devices arranged in series with each other and arranged in parallel with the tank leg, and at least one voltage source arranged in parallel with the tank leg and the resonant switching devices, said resonant switching devices including power semiconductor switches that are operated by gating signals. Additional embodiments having a center-tapped battery on the low voltage side and a plurality of modules on both the low voltage side and the high voltage side are also disclosed for the purpose of reducing ripple current and for reducing the size of the components.

An equivalent circuit for small atrial trabeculae of frog.

PubMed Central

Jakobsson, E; Barr, L; Connor, J A

1975-01-01

An equivalent electrical circuit has been constructed for small atrial trabecula of frog in a double sucrose gap voltage clamp apparatus. The basic strategy in constructing the circuit was to derive the distribution of membrane capacitance and extracellular resistance from the preparation's response to small voltage displacements near the resting condition, when the membrane conductance is presumably quite low. Then standard Hodgkin-Huxley channels were placed in parallel with the capacitance and the results of voltage clamp experiments were simulated. The results suggest that the membranes of the preparation cannot in fact be clamped near the control voltage nor can the ionic currents be measured directly with reasonable accuracy by axon standards. It may or may not be a realizable goal in the future to define the preparation's electrical behavior well enough to permit the ultimate quantitative description of the membrane's specific ion conductances. The result of this paper suggest that if this goal is achieved using the double sucrose gap voltage clamp, it will be by a detailed quantitative accounting for substantial irreducible errors in voltage control, rather than by experimental achievement of good voltage control. PMID:1203441

Fabricating solid carbon porous electrodes from powders

DOEpatents

Kaschmitter, James L.; Tran, Tri D.; Feikert, John H.; Mayer, Steven T.

1997-01-01

Fabrication of conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive dionization, and waste treatment. Electrodes fabricated from low surface area (<50 m.sup.2 /gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon compositives with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to be high surface area carbons, fuel cell electrodes can be produced.

Fabricating solid carbon porous electrodes from powders

DOEpatents

Kaschmitter, J.L.; Tran, T.D.; Feikert, J.H.; Mayer, S.T.

1997-06-10

Fabrication is described for conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive deionization, and waste treatment. Electrodes fabricated from low surface area (<50 m{sup 2}/gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon composites with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to high surface area carbons, fuel cell electrodes can be produced. 1 fig.

Comparison of modified driver circuit and capacitor-transfer circuit in longitudinally excited N2 laser.

PubMed

Uno, Kazuyuki; Akitsu, Tetsuya; Nakamura, Kenshi; Jitsuno, Takahisa

2013-04-01

We developed a modified driver circuit composed of a capacitance and a spark gap, called a direct-drive circuit, for a longitudinally excited gas laser. The direct-drive circuit uses a large discharge impedance caused by a long discharge length of the longitudinal excitation scheme and eliminates the buffer capacitance used in the traditional capacitor-transfer circuit. We compared the direct-drive circuit and the capacitor-transfer circuit in a longitudinally excited N2 laser (wavelength: 337 nm). Producing high output energy with the capacitor-transfer circuit requires a large storage capacitance and a discharge tube with optimum dimensions (an inner diameter of 4 mm and a length of 10 cm in this work); in contrast, the direct-drive circuit requires a high breakdown voltage, achieved with a small storage capacitance and a large discharge tube. Additionally, for the same input energy of 792 mJ, the maximum output energy of the capacitor-transfer circuit was 174.2 μJ, and that of the direct-drive circuit was 344.7 μJ.

Global Model for Asymmetric, Diode-Type Dual Frequency Capacitive Discharge

NASA Astrophysics Data System (ADS)

Kim, Jisoo; Lieberman, M. A.; Lichtenberg, A. J.

2003-10-01

Dual frequency capacitive reactors can have desirable properties for dielectric etch: low cost, robust uniformity over large areas, and control of dissociation. In the ideal case, the high frequency power controls the plasma density (ion flux) and the low frequency voltage controls the ion bombarding energy. Typical operating conditions are: discharge radius 15-30 cm, length 1-3 cm, pressure 30-200 mTorr, high frequency 27.1-160 MHz, low frequency 2-13.6 MHz, and powers of 500-3000 W for both high and low frequencies. The decoupling of the high and low frequencies is an important feature of dual frequency capacitive discharges. In this work, we describe a global (volume-averaged) model having different top and bottom plate areas that incorporates particle balance, and ohmic and stochastic heating for high and low frequencies. The model is used to obtain the decoupling of high and low frequencies and to investigate limitations to ideal decoupling. Support provided by Lam Research, NSF Grant ECS-0139956, California industries, and UC-SMART Contract SM99-10051.

Integration of piezo-capacitive and piezo-electric nanoweb based pressure sensors for imaging of static and dynamic pressure distribution.

PubMed

Jeong, Y J; Oh, T I; Woo, E J; Kim, K J

2017-07-01

Recently, highly flexible and soft pressure distribution imaging sensor is in great demand for tactile sensing, gait analysis, ubiquitous life-care based on activity recognition, and therapeutics. In this study, we integrate the piezo-capacitive and piezo-electric nanowebs with the conductive fabric sheets for detecting static and dynamic pressure distributions on a large sensing area. Electrical impedance tomography (EIT) and electric source imaging are applied for reconstructing pressure distribution images from measured current-voltage data on the boundary of the hybrid fabric sensor. We evaluated the piezo-capacitive nanoweb sensor, piezo-electric nanoweb sensor, and hybrid fabric sensor. The results show the feasibility of static and dynamic pressure distribution imaging from the boundary measurements of the fabric sensors.

VHDL-AMS modelling and simulation of a planar electrostatic micromotor

NASA Astrophysics Data System (ADS)

Endemaño, A.; Fourniols, J. Y.; Camon, H.; Marchese, A.; Muratet, S.; Bony, F.; Dunnigan, M.; Desmulliez, M. P. Y.; Overton, G.

2003-09-01

System level simulation results of a planar electrostatic micromotor, based on analytical models of the static and dynamic torque behaviours, are presented. A planar variable capacitance (VC) electrostatic micromotor designed, fabricated and tested at LAAS (Toulouse) in 1995 is simulated using the high level language VHDL-AMS (VHSIC (very high speed integrated circuits) hardware description language-analog mixed signal). The analytical torque model is obtained by first calculating the overlaps and capacitances between different electrodes based on a conformal mapping transformation. Capacitance values in the order of 10-16 F and torque values in the order of 10-11 N m have been calculated in agreement with previous measurements and simulations from this type of motor. A dynamic model has been developed for the motor by calculating the inertia coefficient and estimating the friction-coefficient-based values calculated previously for other similar devices. Starting voltage results obtained from experimental measurement are in good agreement with our proposed simulation model. Simulation results of starting voltage values, step response, switching response and continuous operation of the micromotor, based on the dynamic model of the torque, are also presented. Four VHDL-AMS blocks were created, validated and simulated for power supply, excitation control, micromotor torque creation and micromotor dynamics. These blocks can be considered as the initial phase towards the creation of intellectual property (IP) blocks for microsystems in general and electrostatic micromotors in particular.

Asymmetric supercapacitors based on electrospun carbon nanofiber/sodium-pre-intercalated manganese oxide electrodes with high power and energy densities

NASA Astrophysics Data System (ADS)

Lin, Sheng-Chi; Lu, Yi-Ting; Chien, Yu-An; Wang, Jeng-An; Chen, Po-Yu; Ma, Chen-Chi M.; Hu, Chi-Chang

2018-07-01

The sodium-pre-intercalated δ-MnO2 is in-situ grown on carbon nanofiber via a simple, one-step method for the application of asymmetric supercapacitors. The pre-intercalation of Na ions into the layered structure of δ-MnO2 reduces the crystallinity, beneficial to Na+ diffusion into/out the interlayer structure and pseudocapacitive utilization of MnO2. This NaxMnO2@CNF nanocomposite with desirable pseudo-capacitance from δ-NaxMnO2 and high electric conductivity from CNF network shows a high specific capacitance of 321 F g-1 at 1 A g-1 with ca. 75.2% capacitance retention from 1 to 32 A g-1. An ASC cell consisting of this nanocomposite and activated carbon as the positive and negative electrodes can be reversibly charged and discharged to a cell voltage of 2.0 V in 1 M Na2SO4 and 4 mM NaHCO3 with specific energy and power of 21 Wh kg-1 and 1 kW kg-1, respectively. This ASC also shows excellent cell capacitance retention (7% decay) in the 2 V, 10,000-cycle stability test, revealing superior performance.

High-Performance Flexible Asymmetric Supercapacitor Based on CoAl-LDH and rGO Electrodes

NASA Astrophysics Data System (ADS)

Li, Shuoshuo; Cheng, Pengpeng; Luo, Jiaxian; Zhou, Dan; Xu, Weiming; Li, Jingwei; Li, Ruchun; Yuan, Dingsheng

2017-07-01

A flexible asymmetric supercapacitor (ASC) based on a CoAl-layered double hydroxide (CoAl-LDH) electrode and a reduced graphene oxide (rGO) electrode was successfully fabricated. The CoAl-LDH electrode as a positive electrode was synthesized by directly growing CoAl-LDH nanosheet arrays on a carbon cloth (CC) through a facile hydrothermal method, and it delivered a specific capacitance of 616.9 F g-1 at a current density of 1 A g-1. The rGO electrode as a negative electrode was synthesized by coating rGO on the CC via a simple dip-coating method and revealed a specific capacitance of 110.0 F g-1 at a current density of 2 A g-1. Ultimately, the advanced ASC offered a broad voltage window (1.7 V) and exhibited a high superficial capacitance of 1.77 F cm-2 at 2 mA cm-2 and a high energy density of 0.71 mWh cm-2 at a power density of 17.05 mW cm-2, along with an excellent cycle stability (92.9% capacitance retention over 8000 charge-discharge cycles).

Nano-structured variable capacitor based on P(VDF-TrFE) copolymer and carbon nanotubes

NASA Astrophysics Data System (ADS)

Lakbita, I.; El-Hami, K.

2018-02-01

A newly organic capacitor was conceived with a variable capacitance using the inverse piezoelectric effect. The device consists of two parallel plates of carbon nanotubes (CNTs), known for their large surface area, high sensitivity and high electric conductivity, separated by a thin film of a dielectric layer of Polyinylidene fluoride and trifluoroehtylene (P(VDF-TrFE)) promising material for piezoelectric and ferroelectric properties. The obtained architecture is the CNT/PVDF-TrFE/CNT capacitor device. In this study, an ultra-thin film of P(VDF-TrFE) (54/46) with thickness of 20 nm was elaborated on highly oriented pyrolytic graphite (HOPG) by spin-coating. The morphology of the ultra-thin film and the mechanical behavior of CNT/P(VDF-TrFE)/CNT system were studied using the atomic force microscopy (AFM) combined with a lock-in amplifier in contact mode. All changes in applied voltage induce a change in thin film thickness according to the inverse piezoelectric effect that affect, consequently the capacitance. The results showed that the ratio of capacitance change ΔC to initial capacitance C0 is ΔC/C0=5%. This value is sufficient to use P(VDF-TrFE) as variable organic capacitor.

Low voltage operation of IGZO thin film transistors enabled by ultrathin Al2O3 gate dielectric

NASA Astrophysics Data System (ADS)

Ma, Pengfei; Du, Lulu; Wang, Yiming; Jiang, Ran; Xin, Qian; Li, Yuxiang; Song, Aimin

2018-01-01

An ultrathin, 5 nm, Al2O3 film grown by atomic-layer deposition was used as a gate dielectric for amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). The Al2O3 layer showed a low surface roughness of 0.15 nm, a low leakage current, and a high breakdown voltage of 6 V. In particular, a very high gate capacitance of 720 nF/cm2 was achieved, making it possible for the a-IGZO TFTs to not only operate at a low voltage of 1 V but also exhibit desirable properties including a low threshold voltage of 0.3 V, a small subthreshold swing of 100 mV/decade, and a high on/off current ratio of 1.2 × 107. Furthermore, even under an ultralow operation voltage of 0.6 V, well-behaved transistor characteristics were still observed with an on/off ratio as high as 3 × 106. The electron transport through the Al2O3 layer has also been analyzed, indicating the Fowler-Nordheim tunneling mechanism.

Modeling and Simulation of Capacitance-Voltage Characteristics of a Nitride GaAs Schottky Diode

NASA Astrophysics Data System (ADS)

Ziane, Abderrezzaq; Amrani, Mohammed; Benamara, Zineb; Rabehi, Abdelaziz

2018-06-01

A nitride GaAs Schottky diode has been fabricated by the nitridation of GaAs substrates using a radio frequency discharge nitrogen plasma source with a layer thickness of approximately 0.7 nm of GaN. The capacitance-voltage (C-V) characteristics of the Au/GaN/GaAs structure were investigated at room temperature for different frequencies, ranging from 1 kHz to 1 MHz. The C-V measurements for the Au/GaN/GaAs Schottky diode were found to be strongly dependent on the bias voltage and the frequency. The capacitance curves depict an anomalous peak and a negative capacitance phenomenon, indicating the presence of continuous interface state density behavior. A numerical drift-diffusion model based on the Scharfetter-Gummel algorithm was elaborated to solve a system composed of the Poisson and continuities equations. In this model, we take into account the continuous interface state density, and we have considered exponential and Gaussian distributions of trap states in the band gap. The effects of the GaAs doping concentration and the trap state density are discussed. We deduce the shape and values of the trap states, then we validate the developed model by fitting the computed C-V curves with experimental measurements at low frequency.

Trap Healing for High-Performance Low-Voltage Polymer Transistors and Solution-Based Analog Amplifiers on Foil.

PubMed

Pecunia, Vincenzo; Nikolka, Mark; Sou, Antony; Nasrallah, Iyad; Amin, Atefeh Y; McCulloch, Iain; Sirringhaus, Henning

2017-06-01

Solution-processed semiconductors such as conjugated polymers have great potential in large-area electronics. While extremely appealing due to their low-temperature and high-throughput deposition methods, their integration in high-performance circuits has been difficult. An important remaining challenge is the achievement of low-voltage circuit operation. The present study focuses on state-of-the-art polymer thin-film transistors based on poly(indacenodithiophene-benzothiadiazole) and shows that the general paradigm for low-voltage operation via an enhanced gate-to-channel capacitive coupling is unable to deliver high-performance device behavior. The order-of-magnitude longitudinal-field reduction demanded by low-voltage operation plays a fundamental role, enabling bulk trapping and leading to compromised contact properties. A trap-reduction technique based on small molecule additives, however, is capable of overcoming this effect, allowing low-voltage high-mobility operation. This approach is readily applicable to low-voltage circuit integration, as this work exemplifies by demonstrating high-performance analog differential amplifiers operating at a battery-compatible power supply voltage of 5 V with power dissipation of 11 µW, and attaining a voltage gain above 60 dB at a power supply voltage below 8 V. These findings constitute an important milestone in realizing low-voltage polymer transistors for solution-based analog electronics that meets performance and power-dissipation requirements for a range of battery-powered smart-sensing applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of silicon-on-insulator wafers

NASA Astrophysics Data System (ADS)

Park, Ki Hoon

The silicon-on-insulator (SOI) is attracting more interest as it is being used for an advanced complementary-metal-oxide-semiconductor (CMOS) and a base substrate for novel devices to overcome present obstacles in bulk Si scaling. Furthermore, SOI fabrication technology has improved greatly in recent years and industries produce high quality wafers with high yield. This dissertation investigated SOI material properties with simple, yet accurate methods. The electrical properties of as-grown wafers such as electron and hole mobilities, buried oxide (BOX) charges, interface trap densities, and carrier lifetimes were mainly studied. For this, various electrical measurement techniques were utilized such as pseudo-metal-oxide-semiconductor field-effect-transistor (PseudoMOSFET) static current-voltage (I-V) and transient drain current (I-t), Hall effect, and MOS capacitance-voltage/capacitance-time (C-V/C-t). The electrical characterization, however, mainly depends on the pseudo-MOSFET method, which takes advantage of the intrinsic SOI structure. From the static current-voltage and pulsed measurement, carrier mobilities, lifetimes and interface trap densities were extracted. During the course of this study, a pseudo-MOSFET drain current hysteresis regarding different gate voltage sweeping directions was discovered and the cause was revealed through systematic experiments and simulations. In addition to characterization of normal SOI, strain relaxation of strained silicon-on-insulator (sSOI) was also measured. As sSOI takes advantage of wafer bonding in its fabrication process, the tenacity of bonding between the sSOI and the BOX layer was investigated by means of thermal treatment and high dose energetic gamma-ray irradiation. It was found that the strain did not relax with processes more severe than standard CMOS processes, such as anneals at temperature as high as 1350 degree Celsius.

Voltage and partial pressure dependent defect chemistry in (La,Sr)FeO3–δ thin films investigated by chemical capacitance measurements

PubMed Central

Rupp, Ghislain M.; Fleig, Jürgen

2018-01-01

La0.6Sr0.4FeO3–δ (LSF) thin films of different thickness were prepared by pulsed laser deposition on yttria stabilized zirconia (YSZ) and characterized by using three electrode impedance spectroscopy. Electrochemical film capacitance was analyzed in relation to oxygen partial pressure (0.25 mbar to 1 bar), DC polarization (0 m to –600 m) and temperature (500 to 650 °C). For most measurement parameters, the chemical bulk capacitance dominates the overall capacitive properties and the corresponding defect chemical state depends solely on the oxygen chemical potential inside the film, independent of atmospheric oxygen pressure and DC polarization. Thus, defect chemical properties (defect concentrations and defect formation enthalpies) could be deduced from such measurements. Comparison with LSF defect chemical bulk data from the literature showed good agreement for vacancy formation energies but suggested larger electronic defect concentrations in the films. From thickness-dependent measurements at lower oxygen chemical potentials, an additional capacitive contribution could be identified and attributed to the LSF|YSZ interface. Deviations from simple chemical capacitance models at high pressures are most probably due to defect interactions. PMID:29671421

Voltage and partial pressure dependent defect chemistry in (La,Sr)FeO3-δ thin films investigated by chemical capacitance measurements.

PubMed

Schmid, Alexander; Rupp, Ghislain M; Fleig, Jürgen

2018-05-03

La0.6Sr0.4FeO3-δ (LSF) thin films of different thickness were prepared by pulsed laser deposition on yttria stabilized zirconia (YSZ) and characterized by using three electrode impedance spectroscopy. Electrochemical film capacitance was analyzed in relation to oxygen partial pressure (0.25 mbar to 1 bar), DC polarization (0 m to -600 m) and temperature (500 to 650 °C). For most measurement parameters, the chemical bulk capacitance dominates the overall capacitive properties and the corresponding defect chemical state depends solely on the oxygen chemical potential inside the film, independent of atmospheric oxygen pressure and DC polarization. Thus, defect chemical properties (defect concentrations and defect formation enthalpies) could be deduced from such measurements. Comparison with LSF defect chemical bulk data from the literature showed good agreement for vacancy formation energies but suggested larger electronic defect concentrations in the films. From thickness-dependent measurements at lower oxygen chemical potentials, an additional capacitive contribution could be identified and attributed to the LSF|YSZ interface. Deviations from simple chemical capacitance models at high pressures are most probably due to defect interactions.

Stability of Triggering of the Switch with Sharply Non-Uniform Electric Field at the Electrode with Negative Potential

NASA Astrophysics Data System (ADS)

Kovalchuk, B. M.; Zherlitsyn, A. A.; Kumpyak, E. V.

2017-12-01

Results of investigations into a two-electrode high-pressure gas switch with sharply non-uniform field at the electrode with negative potential operating in the self-breakdown regime with pulsed charging of a highvoltage capacitive energy storage for 100 μs to voltage exceeding 200 kV are presented. It is demonstrated that depending on the air pressure and the gap length, the corona-streamer discharge, whose current increases with voltage, arises in the switch at a voltage of 0.2-0.3 of the self-breakdown voltage. At the moment of switch self-breakdown, the corona-streamer discharge goes over to one or several spark channels. The standard deviation of the triggering moment can be within 1.5 μs, which corresponds to the standard deviation of the self-breakdown voltage less than 2 kV. The voltage stability can be better than 1.5%.

Contact inspection of Si nanowire with SEM voltage contrast

NASA Astrophysics Data System (ADS)

Ohashi, Takeyoshi; Yamaguchi, Atsuko; Hasumi, Kazuhisa; Ikota, Masami; Lorusso, Gian; Horiguchi, Naoto

2018-03-01

A methodology to evaluate the electrical contact between nanowire (NW) and source/drain (SD) in NW FETs was investigated with SEM voltage contrast (VC). The electrical defects were robustly detected by VC. The validity of the inspection result was verified by TEM physical observations. Moreover, estimation of the parasitic resistance and capacitance was achieved from the quantitative analysis of VC images which were acquired with different scan conditions of electron beam (EB). A model considering the dynamics of EB-induce charging was proposed to calculate the VC. The resistance and capacitance can be determined by comparing the model-based VC with experimentally obtained VC. Quantitative estimation of resistance and capacitance would be valuable not only for more accurate inspection, but also for identification of the defect point.

rf Quantum Capacitance of the Topological Insulator Bi2Se3 in the Bulk Depleted Regime for Field-Effect Transistors

NASA Astrophysics Data System (ADS)

Inhofer, A.; Duffy, J.; Boukhicha, M.; Bocquillon, E.; Palomo, J.; Watanabe, K.; Taniguchi, T.; Estève, I.; Berroir, J. M.; Fève, G.; Plaçais, B.; Assaf, B. A.

2018-02-01

A metal-dielectric topological-insulator capacitor device based on hexagonal-boron-nitrate- (h -BN) encapsulated CVD-grown Bi2Se3 is realized and investigated in the radio-frequency regime. The rf quantum capacitance and device resistance are extracted for frequencies as high as 10 GHz and studied as a function of the applied gate voltage. The superior quality h -BN gate dielectric combined with the optimized transport characteristics of CVD-grown Bi2Se3 (n ˜1018 cm-3 in 8 nm) on h -BN allow us to attain a bulk depleted regime by dielectric gating. A quantum-capacitance minimum and a linear variation of the capacitance with the chemical potential are observed revealing a Dirac regime. The topological surface state in proximity to the gate is seen to reach charge neutrality, but the bottom surface state remains charged and capacitively coupled to the top via the insulating bulk. Our work paves the way toward implementation of topological materials in rf devices.

Low-crystalline iron oxide hydroxide nanoparticle anode for high-performance supercapacitors

PubMed Central

Owusu, Kwadwo Asare; Qu, Longbing; Li, Jiantao; Wang, Zhaoyang; Zhao, Kangning; Yang, Chao; Hercule, Kalele Mulonda; Lin, Chao; Shi, Changwei; Wei, Qiulong; Zhou, Liang; Mai, Liqiang

2017-01-01

Carbon materials are generally preferred as anodes in supercapacitors; however, their low capacitance limits the attained energy density of supercapacitor devices with aqueous electrolytes. Here, we report a low-crystalline iron oxide hydroxide nanoparticle anode with comprehensive electrochemical performance at a wide potential window. The iron oxide hydroxide nanoparticles present capacitances of 1,066 and 716 F g−1 at mass loadings of 1.6 and 9.1 mg cm−2, respectively, a rate capability with 74.6% of capacitance retention at 30 A g−1, and cycling stability retaining 91% of capacitance after 10,000 cycles. The performance is attributed to a dominant capacitive charge-storage mechanism. An aqueous hybrid supercapacitor based on the iron oxide hydroxide anode shows stability during float voltage test for 450 h and an energy density of 104 Wh kg−1 at a power density of 1.27 kW kg−1. A packaged device delivers gravimetric and volumetric energy densities of 33.14 Wh kg−1 and 17.24 Wh l−1, respectively. PMID:28262797

High performance asymmetric supercapacitor based on polypyrrole/graphene composite and its derived nitrogen-doped carbon nano-sheets

NASA Astrophysics Data System (ADS)

Zhu, Jianbo; Feng, Tianyu; Du, Xianfeng; Wang, Jingping; Hu, Jun; Wei, LiPing

2017-04-01

Neutral aqueous medium is a promising electrolyte for supercapacitors because it is low-cost, environmental-friendly and can achieve rapid charging/discharging with high power density. However, the energy density of such supercapacitor is significantly limited by its narrow operational voltage window. Herein, we demonstrated an effective approach to broaden the operational voltage window by fabricating an asymmetric supercapacitor (ASC) with polypyrrole/reduced graphene oxide (PPy/rGO) composite and its derived Nitrogen-doped carbon nano-sheets (NCs) as positive and negative electrode material, respectively. The homogeneous nano-sheet and mesoporous structure of PPy/rGO and NCs can facilitate rapid charge/ion migration and provide more active sites for ions adsorption/exchange to improve their electrochemical performance. Benefiting from high capacitance and good rate performance of PPy/rGO and NCs electrodes, the as-fabricated ASCs devices in a polyvinyl alcohol/LiCl gel electrolyte can realize a wide operational voltage of 1.6 V and deliver high energy density of 15.8 wh kg-1 (1.01 mWh cm-3) at 0.14 kW kg-1 (19.3 mW cm-3), which still remains 9.5 wh kg-1as power density increases to 6.56 kW kg-1, as well as excellent long-term cycling stability with about 88.7% capacitance retention after 10000 cycles. The remarkable performances suggest that the ASCs devices are promising for future energy storage applications.

The Design and Characterization of a Prototype Wideband Voltage Sensor Based on a Resistive Divider

PubMed Central

Garnacho, Fernando; Khamlichi, Abderrahim; Rovira, Jorge

2017-01-01

The most important advantage of voltage dividers over traditional voltage transformers is that voltage dividers do not have an iron core with non-linear hysteresis characteristics. The voltage dividers have a linear behavior with respect to over-voltages and a flat frequency response larger frequency range. The weak point of a voltage divider is the influence of external high-voltage (HV) and earth parts in its vicinity. Electrical fields arising from high voltages in neighboring phases and from ground conductors and structures are one of their main sources for systematic measurement errors. This paper describes a shielding voltage divider for a 24 kV medium voltage network insulated in SF6 composed of two resistive-capacitive dividers, one integrated within the other, achieving a flat frequency response up to 10 kHz for ratio error and up to 5 kHz for phase displacement error. The metal shielding improves its immunity against electric and magnetic fields. The characterization performed on the built-in voltage sensor shows an accuracy class of 0.2 for a frequency range from 20 Hz to 5 kHz and a class of 0.5 for 1 Hz up to 20 Hz. A low temperature effect is also achieved for operation conditions of MV power grids. PMID:29149085

The Design and Characterization of a Prototype Wideband Voltage Sensor Based on a Resistive Divider.

PubMed

Garnacho, Fernando; Khamlichi, Abderrahim; Rovira, Jorge

2017-11-17

The most important advantage of voltage dividers over traditional voltage transformers is that voltage dividers do not have an iron core with non-linear hysteresis characteristics. The voltage dividers have a linear behavior with respect to over-voltages and a flat frequency response larger frequency range. The weak point of a voltage divider is the influence of external high-voltage (HV) and earth parts in its vicinity. Electrical fields arising from high voltages in neighboring phases and from ground conductors and structures are one of their main sources for systematic measurement errors. This paper describes a shielding voltage divider for a 24 kV medium voltage network insulated in SF6 composed of two resistive-capacitive dividers, one integrated within the other, achieving a flat frequency response up to 10 kHz for ratio error and up to 5 kHz for phase displacement error. The metal shielding improves its immunity against electric and magnetic fields. The characterization performed on the built-in voltage sensor shows an accuracy class of 0.2 for a frequency range from 20 Hz to 5 kHz and a class of 0.5 for 1 Hz up to 20 Hz. A low temperature effect is also achieved for operation conditions of MV power grids.

Observation of negative differential capacitance (NDC) in Ti Schottky diodes on SiGe islands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rangel-Kuoppa, Victor-Tapio; Jantsch, Wolfgang; Tonkikh, Alexander

2013-12-04

The Negative Differential Capacitance (NDC) effect on Ti Schottky diodes formed on n-type Silicon samples with embedded Germanium Quantum Dots (QDs) is observed and reported. The NDC-effect is detected using capacitance-voltage (CV) method at temperatures below 200 K. It is explained by the capture of electrons in Germanium QDs. Our measurements reveal that each Ge QD captures in average eight electrons.

Asymptotically zero power charge-recycling bus architecture for battery-operated ultrahigh data rate ULSI's

NASA Astrophysics Data System (ADS)

Yamauchi, Hiroyuki; Akamatsu, Hironori; Fujita, Tsutomu

1995-04-01

An asymptotically zero power charge recycling bus (CRB) architecture, featuring virtual stacking of the individual bus-capacitance into a series configuration between supply voltage and ground, has been proposed. This CRB architecture makes it possible to reduce not only each bus-swing but also a total equivalent bus-capacitance of the ultramultibit buses running in parallel. The voltage swing of each bus is given by the recycled charge-supplying from the upper adjacent bus capacitance, instead of the power line. The dramatical power reduction was verified by the simulated and measured data. According to these data, the ultrahigh data rate of 25.6 Gb/s can be achieved while maintaining the power dissipation to be less than 100 mW, which corresponds to less than 10% that of the previously reported 0.9 V suppressed bus-swing scheme, at V(sub cc) = 3.6 V for the bus width of 512 b with the bus-capacitance of 14 pF per bit operating at 50 MHz.

A variable capacitance based modeling and power capability predicting method for ultracapacitor

NASA Astrophysics Data System (ADS)

Liu, Chang; Wang, Yujie; Chen, Zonghai; Ling, Qiang

2018-01-01

Methods of accurate modeling and power capability predicting for ultracapacitors are of great significance in management and application of lithium-ion battery/ultracapacitor hybrid energy storage system. To overcome the simulation error coming from constant capacitance model, an improved ultracapacitor model based on variable capacitance is proposed, where the main capacitance varies with voltage according to a piecewise linear function. A novel state-of-charge calculation approach is developed accordingly. After that, a multi-constraint power capability prediction is developed for ultracapacitor, in which a Kalman-filter-based state observer is designed for tracking ultracapacitor's real-time behavior. Finally, experimental results verify the proposed methods. The accuracy of the proposed model is verified by terminal voltage simulating results under different temperatures, and the effectiveness of the designed observer is proved by various test conditions. Additionally, the power capability prediction results of different time scales and temperatures are compared, to study their effects on ultracapacitor's power capability.

On the Relationship Between Schottky Barrier Capacitance and Mixer Performance at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Romanofsky, Robert R.

1996-01-01

The flat-band voltage is the Schottky junction voltage required to shrink the depletion width to zero. At cryogenic temperatures, mixer diodes are generally biased and/or pumped beyond the flat-band condition to minimize conversion loss and noise figure. This occurs despite the presumed sharp increase in junction capacitance near flat-band, which should instead limit mixer performance. Past moderate forward bias, the diode C-V relationship is difficult to measure. A simple analytic expression for C(V) is usually used to model and predict mixer performance. This letter provides experimental data on C(V) at 77 K based on a microwave measurement and modeling technique. Data is also provided on the conversion loss of a singly balanced mixer optimized for 77 K operation. The connection between junction capacitance, flat-band potential, and conversion loss is examined. It is shown that the analytic expression greatly overestimates the junction capacitance that occurs as flat-band is approached.

Non-intrusive high voltage measurement using slab coupled optical sensors

NASA Astrophysics Data System (ADS)

Stan, Nikola; Chadderdon, Spencer; Selfridge, Richard H.; Schultz, Stephen M.

2014-03-01

We present an optical fiber non-intrusive sensor for measuring high voltage transients. The sensor converts the unknown voltage to electric field, which is then measured using slab-coupled optical fiber sensor (SCOS). Since everything in the sensor except the electrodes is made of dielectric materials and due to the small field sensor size, the sensor is minimally perturbing to the measured voltage. We present the details of the sensor design, which eliminates arcing and minimizes local dielectric breakdown using Teflon blocks and insulation of the whole structure with transformer oil. The structure has a capacitance of less than 3pF and resistance greater than 10 GΩ. We show the measurement of 66.5 kV pulse with a 32.6μs time constant. The measurement matches the expected value of 67.8 kV with less than 2% error.

Fabrication and electrical characterization of a MOS memory device containing self-assembled metallic nanoparticles

NASA Astrophysics Data System (ADS)

Sargentis, Ch.; Giannakopoulos, K.; Travlos, A.; Tsamakis, D.

2007-04-01

Floating gate devices with nanoparticles embedded in dielectrics have recently attracted much attention due to the fact that these devices operate as non-volatile memories with high speed, high density and low power consumption. In this paper, memory devices containing gold (Au) nanoparticles have been fabricated using e-gun evaporation. The Au nanoparticles are deposited on a very thin SiO 2 layer and are then fully covered by a HfO 2 layer. The HfO 2 is a high- k dielectric and gives good scalability to the fabricated devices. We studied the effect of the deposition parameters to the size and the shape of the Au nanoparticles using capacitance-voltage and conductance-voltage measurements, we demonstrated that the fabricated device can indeed operate as a low-voltage memory device.

Delta connected resonant snubber circuit

DOEpatents

Lai, J.S.; Peng, F.Z.; Young, R.W. Sr.; Ott, G.W. Jr.

1998-01-20

A delta connected, resonant snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the dc supply voltage through the main inverter switches and the auxiliary switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter. 36 figs.

Delta connected resonant snubber circuit

DOEpatents

Lai, Jih-Sheng; Peng, Fang Zheng; Young, Sr., Robert W.; Ott, Jr., George W.

1998-01-01

A delta connected, resonant snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the dc supply voltage through the main inverter switches and the auxiliary switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter.

Ice detector

NASA Technical Reports Server (NTRS)

Weinstein, Leonard M. (Inventor)

1988-01-01

An ice detector is provided for the determination of the thickness of ice on the outer surface on an object (e.g., aircraft) independently of temperature or the composition of the ice. First capacitive gauge, second capacitive gauge, and temperature gauge are embedded in embedding material located within a hollowed out portion of the outer surface. This embedding material is flush with the outer surface to prevent undesirable drag. The first capacitive gauge, second capacitive gauge, and the temperature gauge are respectively connected to first capacitive measuring circuit, second capacitive measuring circuit, and temperature measuring circuit. The geometry of the first and second capacitive gauges is such that the ratio of the voltage outputs of the first and second capacitance measuring circuits is proportional to the thickness of ice, regardless of ice temperature or composition. This ratio is determined by offset and dividing circuit.

Nanostructure selenium compounds as pseudocapacitive electrodes for high-performance asymmetric supercapacitor

PubMed Central

Hua, Fengting; Sun, Kanjun; Fenga, Enke; Peng, Hui; Zhang, Zhiguo; Lei, Ziqiang

2018-01-01

The electrochemical performance of an energy conversion and storage device like the supercapacitor mainly depends on the microstructure and morphology of the electrodes. In this paper, to improve the capacitance performance of the supercapacitor, the all-pseudocapacitive electrodes of lamella-like Bi18SeO29/BiSe as the negative electrode and flower-like Co0.85Se nanosheets as the positive electrode are synthesized by using a facile low-temperature one-step hydrothermal method. The microstructures and morphology of the electrode materials are carefully characterized, and the capacitance performances are also tested. The Bi18SeO29/BiSe and Co0.85Se have high specific capacitance (471.3 F g–1 and 255 F g–1 at 0.5 A g–1), high conductivity, outstanding cycling stability, as well as good rate capability. The assembled asymmetric supercapacitor completely based on the pseudocapacitive electrodes exhibits outstanding cycling stability (about 93% capacitance retention after 5000 cycles). Moreover, the devices exhibit high energy density of 24.2 Wh kg–1 at a power density of 871.2 W kg–1 in the voltage window of 0–1.6 V with 2 M KOH solution. PMID:29410830

Effect of inductive and capacitive coupling on the current–voltage characteristic and electromagnetic radiation from a system of Josephson junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rahmonov, I. R., E-mail: rahmonov@theor.jinr.ru, E-mail: ilhom-tj@inbox.ru; Shukrinov, Yu. M.; Atanasova, P. Kh.

We have studied the current–voltage characteristic of a system of long Josephson junctions taking into account the inductive and capacitive coupling. The dependence of the average time derivative of the phase difference on the bias current and spatiotemporal dependences of the phase difference and magnetic field in each junction are considered. The possibility of branching of the current–voltage characteristic in the region of zero field step, which is associated with different numbers of fluxons in individual Josephson junctions, is demonstrated. The current–voltage characteristic of the system of Josephson junctions is compared with the case of a single junction, and itmore » is shown that the observed branching is due to coupling between the junctions. The intensity of electromagnetic radiation associated with motion of fluxons is calculated, and the effect of coupling between junctions on the radiation power is analyzed.« less

Varactor with integrated micro-discharge source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elizondo-Decanini, Juan M.; Manginell, Ronald P.; Moorman, Matthew W.

2016-10-18

An apparatus that includes a varactor element and an integrated micro-discharge source is disclosed herein. In a general embodiment, the apparatus includes at least one np junction and at least one voltage source that is configured to apply voltage across the np junction. The apparatus further includes an aperture that extends through the np junction. When the voltage is applied across the np junction, gas in the aperture is ionized, forming a plasma, in turn causing a micro-discharge (of light, charge particles, and space charge) to occur. The light (charge particles, and space charge) impinges upon the surface of themore » np junction exposed in the aperture, thereby altering capacitance of the np junction. When used within an oscillator circuit, the effect of the plasma on the np-junction extends the capacitance changes of the np-junction and extends the oscillator frequency range in ways not possible by a conventional voltage controlled oscillator (VCO).« less

Spiro-(1,1‧)-bipyrrolidinium tetrafluoroborate salt as high voltage electrolyte for electric double layer capacitors

NASA Astrophysics Data System (ADS)

Yu, Xuewen; Ruan, Dianbo; Wu, Changcheng; Wang, Jing; Shi, Zhiqiang

2014-11-01

A novel quaternary ammonium salt based on spiro-(1,1‧)-bipyrolidinium tetrafluoroborate (SBP-BF4) has been synthesized and dissolved in propylene carbonate (PC) with 1.5 mol L-1 (M) concentration for electric double-layer capacitors (EDLCs). The physic-chemical properties and electrochemical performance of SBP-BF4/PC electrolyte are investigated. Compared with the standard electrolyte 1.5 M TEMA-BF4 in PC, the novel SBP-BF4/PC electrolyte exhibited much better electrochemical performance due to its smaller cation size, lower viscosity and higher conductivity. The specific discharge capacitance of activated carbon electrode based EDLCs using SBP-BF4/PC electrolyte is 120 F g-1, the energy density and power density can reach 31 kW kg-1 and 6938 W kg-1, respectively, when the working voltage is 2.7 V and current density is 50 mA g-1. The withstand voltage of activated carbon based EDLCs with SBP-BF4/PC electrolyte can reach to 3.2 V, where the stable discharge capacitance and energy density are 121 F g-1 and 43 Wh kg-1, respectively.

Capacitors and Resistance-Capacitance Networks.

ERIC Educational Resources Information Center

Balabanian, Norman; Root, Augustin A.

This programed textbook was developed under a contract with the United States Office of Education as Number 5 in a series of materials for use in an electrical engineering sequence. It is divided into three parts--(1) capacitors, (2) voltage-current relationships, and (3) simple resistance-capacitance networks. (DH)

Solutions for transients in arbitrarily branching cables: III. Voltage clamp problems.

PubMed

Major, G

1993-07-01

Branched cable voltage recording and voltage clamp analytical solutions derived in two previous papers are used to explore practical issues concerning voltage clamp. Single exponentials can be fitted reasonably well to the decay phase of clamped synaptic currents, although they contain many underlying components. The effective time constant depends on the fit interval. The smoothing effects on synaptic clamp currents of dendritic cables and series resistance are explored with a single cylinder + soma model, for inputs with different time courses. "Soma" and "cable" charging currents cannot be separated easily when the soma is much smaller than the dendrites. Subtractive soma capacitance compensation and series resistance compensation are discussed. In a hippocampal CA1 pyramidal neurone model, voltage control at most dendritic sites is extremely poor. Parameter dependencies are illustrated. The effects of series resistance compound those of dendritic cables and depend on the "effective capacitance" of the cell. Plausible combinations of parameters can cause order-of-magnitude distortions to clamp current waveform measures of simulated Schaeffer collateral inputs. These voltage clamp problems are unlikely to be solved by the use of switch clamp methods.

Enhancing Graphene Capacitance by Nitrogen: Effects of Doping Configuration and Concentration

DOE PAGES

Zhan, Cheng; Cummings, Peter; Jiang, De-en

2016-01-08

Recent experiments have shown that nitrogen doping enhances capacitance in carbon electrode supercapacitors. However, a detailed study of the effect of N-doping on capacitance is still lacking. In this paper, we study the doping concentration and the configuration effect on the electric double-layer (EDL) capacitance, quantum capacitance, and total capacitance. It is found that pyridinic and graphitic nitrogens can increase the total capacitance by increasing quantum capacitance, but pyrrolic configuration limits the total capacitance due to its much lower quantum capacitance than the other two configurations. We also find that, unlike the graphitic and pyridinic nitrogens, the pyrrolic configuration's quantummore » capacitance does not depend on the nitrogen concentration, which may explain why some capacitance versus voltage measurements of N-doped graphene exhibit a V-shaped curve similar to that of undoped graphene. Our investigation provides a deeper understanding of the capacitance enhancement of the N-doping effect in carbon electrodes and suggests a potentially effective way to optimize the capacitance by controlling the type of N-doping.« less

A high-voltage cardiac stimulator for field shocks of a whole heart in a bath

NASA Astrophysics Data System (ADS)

Mashburn, David N.; Hinkson, Stephen J.; Woods, Marcella C.; Gilligan, Jonathan M.; Holcomb, Mark R.; Wikswo, John P.

2007-10-01

Defibrillators are a critical tool for treating heart disease; however, the mechanisms by which they halt fibrillation are still not fully understood and are the subject of ongoing research. Clinical defibrillators do not provide the precise control of shock timing, duration, and voltage or other features needed for detailed scientific inquiry, and there are few, if any, commercially available units designed for research applications. For this reason, we have developed a high-voltage, programmable, capacitive-discharge stimulator optimized to deliver defibrillation shocks with precise timing and voltage control to an isolated animal heart, either in air or in a bath. This stimulator is capable of delivering voltages of up to 500V and energies of nearly 100J with timing accuracy of a few microseconds and with rise and fall times of 5μs or less and is controlled only by two external timing pulses and a control computer that sets the stimulation parameters via a LABVIEW interface. Most importantly, the stimulator has circuits to protect the high-voltage circuitry and the operator from programming and input-output errors. This device has been tested and used successfully in field shock experiments on rabbit hearts as well as other protocols requiring high voltage.

Formation and characterization of Ta2O5/TaOx films formed by O ion implantation

NASA Astrophysics Data System (ADS)

Ruffell, S.; Kurunczi, P.; England, J.; Erokhin, Y.; Hautala, J.; Elliman, R. G.

2013-07-01

Ta2O5/TaOx (oxide/suboxide) heterostructures are fabricated by high fluence O ion-implantation into deposited Ta films. The resultant films are characterized by depth profiling X-ray photoelectron spectroscopy (XPS), cross-sectional transmission electron microscopy (XTEM), four-point probe, and current-voltage and capacitance-voltage measurements. The measurements show that Ta2O5/TaOx oxide/suboxide heterostructures can be fabricated with the relative thicknesses of the layers controlled by implantation energy and fluence. Electrical measurements show that this approach has promise for high volume manufacturing of resistive switching memory devices based on oxide/suboxide heterostructures.

Supercapacitors based on self-assembled graphene organogel.

PubMed

Sun, Yiqing; Wu, Qiong; Shi, Gaoquan

2011-10-14

Self-assembled graphene organogel (SGO) with 3-dimensional (3D) macrostructure was prepared by solvothermal reduction of a graphene oxide (GO) dispersion in propylene carbonate (PC). This SGO was used as an electrode material for fabricating supercapacitors with a PC electrolyte. The supercapacitor can be operated in a wide voltage range of 0-3 V and exhibits a high specific capacitance of 140 F g(-1) at a discharge current density of 1 A g(-1). Furthermore, it can still keep a specific capacitance of 90 F g(-1) at a high current density of 30 A g(-1). The maximum energy density of the SGO based supercapacitor was tested to be 43.5 Wh kg(-1), and this value is higher than those of the graphene based supercapacitors with aqueous or PC electrolytes reported previously. Furthermore, at a high discharge current density of 30 A g(-1), the energy and power densities of the supercapacitor were measured to be 15.4 Wh kg(-1) and 16,300 W kg(-1), respectively. These results indicate that the supercapacitor has a high specific capacitance and power density, and excellent rate capability.

Multi-level Capacitive Memory Effect in Metal/Oxide/Floating-Schottky Junction

NASA Astrophysics Data System (ADS)

Choi, Gahyun; Jung, Sungchul; Yoon, Hoon Hahn; Jeon, Youngeun; Park*, Kibog

2015-03-01

A memory computing (memcomputing) system can store and process information at the same physical location simultaneously. The essential components of memcomputing are passive devices with memory functionality, such as memristor, memcapacitor, and meminductor. We report the realization of a Schottky contact memcapacitor compatible with the current Si CMOS technology. Our memcapacitor is formed by depositing a stack of metal and oxide thin films on top of a Schottky contact. Here, the metal electrode of the Schottky contact is floating. The working principle of our memcapacitor is based on the fact that the depletion width of the Schottky contact varies according to the amount of charge stored in the floating metal electrode. The voltage pulse applied across the Metal/Oxide/Floating-Schottky junction controls charge flow in the Schottky contact and determines the amount of charge stored eventually. It is demonstrated experimentally that our memcapacitor exhibits hysteresis behaviors in capacitance-voltage curves and possesses multiple capacitance values that are switchable by the applied voltage pulse. Supported by NRF in South Korea (2013R1A1A2007070).

Low-voltage organic strain sensor on plastic using polymer/high- K inorganic hybrid gate dielectrics

NASA Astrophysics Data System (ADS)

Jung, Soyoun; Ji, Taeksoo; Varadan, Vijay K.

2007-12-01

In this paper, gate-induced pentacene semiconductor strain sensors based on hybrid-gate dielectrics using poly-vinylphenol (PVP) and high-K inorganic, Ta IIO 5 are fabricated on flexible substrates, polyethylene naphthalate (PEN). The Ta IIO 5 gate dielectric layer is combined with a thin PVP layer to obtain very smooth and hydrophobic surfaces which improve the molecular structures of pentacene films. The PVP-Ta IIO 5 hybrid-gate dielectric films exhibit a high dielectric capacitance and low leakage current. The sensors adopting thin film transistor (TFT)-like structures show a significantly reduced operating voltage (~6V), and good device characteristics with a field-effect mobility of 1.89 cm2/V•s, a threshold voltage of -0.5 V, and an on/off ratio of 10 3. The strain sensor, one of the practical applications in large-area organic electronics, was characterized with different bending radii of 50, 40, 30, and 20 mm. The sensor output signals were significantly improved with low-operating voltages.

Electronic Current Transducer (ECT) for high voltage dc lines

NASA Astrophysics Data System (ADS)

Houston, J. M.; Peters, P. H., Jr.; Summerayes, H. R., Jr.; Carlson, G. J.; Itani, A. M.

1980-02-01

The development of a bipolar electronic current transducer (ECT) for measuring the current in a high voltage dc (HVDC) power line at line potential is discussed. The design and construction of a free standing ECT for use on a 400 kV line having a nominal line current of 2000 A is described. Line current is measured by a 0.0001 ohm shunt whose voltage output is sampled by a 14 bit digital data link. The high voltage interface between line and ground is traversed by optical fibers which carry digital light signals as far as 300 m to a control room where the digital signal is converted back to an analog representation of the shunt voltage. Two redundant electronic and optical data links are used in the prototype. Power to operate digital and optical electronics and temperature controlling heaters at the line is supplied by a resistively and capacitively graded 10 stage cascade of ferrite core transformers located inside the hollow, SF6 filled, porcelain support insulator. The cascade is driven by a silicon controlled rectifier inverter which supplies about 100 W of power at 30 kHz.

Cross-Talk Limits of Highly Segmented Semiconductor Detectors

NASA Astrophysics Data System (ADS)

Pullia, Alberto; Weisshaar, Dirk; Zocca, Francesca; Bazzacco, Dino

2011-06-01

Cross-talk limits of monolithic highly-segmented semiconductor detectors for high-resolution X-gamma spectrometry are investigated. Cross-talk causes false signal components yielding amplitude losses and fold-dependent shifts of the spectral lines, which partially spoil the spectroscopic performance of the detector. Two complementary electrical models are developed, which describe quantitatively the inter-channel cross-talk of monolithic segmented detectors whose electrodes are read out by charge-sensitive preamplifiers. The first is here designated as Cross-Capacitance (CC) model, the second as Split-Charge (SC) model. The CC model builds around the parasitic capacitances Cij linking the preamplifier outputs and the neighbor channel inputs. The SC model builds around the finite-value of the decoupling capacitance CC used to read out the high-voltage detector electrode. The key parameters of the models are individuated and ideas are shown to minimize their impact. Using a quasi-coaxial germanium segmented detector it is found that the SC cross-talk becomes negligible for decoupling capacitances larger than 1 nF, where instead the CC cross-talk tends to dominate. The residual cross-talk may be reduced by minimization of stray capacitances Cij, through a careful design of the layout of the Printed Circuit Board (PCB) where the input transistors are mounted. Cij can be made as low as 5 fF, but it is shown that even in such case the impact of the CC cross-talk on the detector performance is not negligible. Finally, an algorithm for cross-talk correction is presented and elaborated.

Laser-Printed In-Plane Micro-Supercapacitors: From Symmetric to Asymmetric Structure.

PubMed

Huang, Gui-Wen; Li, Na; Du, Yi; Feng, Qing-Ping; Xiao, Hong-Mei; Wu, Xing-Hua; Fu, Shao-Yun

2018-01-10

Here, we propose and demonstrate a complete solution for efficiently fabricating in-plane micro-supercapacitors (MSCs) from a symmetric to asymmetric structure. By using an original laser printing process, symmetric MSC with reduced graphene oxide (rGO)/silver nanowire (Ag-NW) hybrid electrodes was facilely fabricated and a high areal capacitance of 5.5 mF cm -2 was achieved, which reaches the best reports on graphene-based MSCs. More importantly, a "print-and-fold" method has been creatively proposed that enabled the rapid manufacturing of asymmetric in-plane MSCs beyond the traditional cumbersome technologies. α-Ni(OH) 2 particles with high tapping density were successfully synthesized and employed as the pseudocapacitive material. Consequently, an improved supply voltage of 1.5 V was obtained and an areal capacitance as high as 8.6 mF cm -2 has been realized. Moreover, a demonstration of a miniaturized MSC pack was performed by multiply-folding the serial Ag-NW-connected MSC units. As a result, a compact MSC pack with a high supply voltage of 3 V was obtained, which can be utilized to power a light-emitting diode light. These presented technologies may pave the way for the efficiently producing high performance in-plane MSCs, meanwhile offering a solution for the achievement of practical power supply packs integrated in limited spaces.

Capacitance measuring device

DOEpatents

Andrews, W.H. Jr.

1984-08-01

A capacitance measuring circuit is provided in which an unknown capacitance is measured by comparing the charge stored in the unknown capacitor with that stored in a known capacitance. Equal and opposite voltages are repetitively simultaneously switched onto the capacitors through an electronic switch driven by a pulse generator to charge the capacitors during the ''on'' portion of the cycle. The stored charge is compared by summing discharge currents flowing through matched resistors at the input of a current sensor during the ''off'' portion of the switching cycle. The net current measured is thus proportional to the difference in value of the two capacitances. The circuit is capable of providing much needed accuracy and stability to a great variety of capacitance-based measurement devices at a relatively low cost.

Switching power pulse system

DOEpatents

Aaland, Kristian

1983-01-01

A switching system for delivering pulses of power from a source (10) to a load (20) using a storage capacitor (C3) charged through a rectifier (D1, D2), and maintained charged to a reference voltage level by a transistor switch (Q1) and voltage comparator (12). A thyristor (22) is triggered to discharge the storage capacitor through a saturable reactor (18) and fractional turn saturable transformer (16) having a secondary to primary turn ratio N of n:l/n=n.sup.2. The saturable reactor (18) functions as a "soaker" while the thyristor reaches saturation, and then switches to a low impedance state. The saturable transformer functions as a switching transformer with high impedance while a load coupling capacitor (C4) charges, and then switches to a low impedance state to dump the charge of the storage capacitor (C3) into the load through the coupling capacitor (C4). The transformer is comprised of a multilayer core (26) having two secondary windings (28, 30) tightly wound and connected in parallel to add their output voltage and reduce output inductance, and a number of single turn windings connected in parallel at nodes (32, 34) for the primary winding, each single turn winding linking a different one of the layers of the multilayer core. The load may be comprised of a resistive beampipe (40) for a linear particle accelerator and capacitance of a pulse forming network (42). To hold off discharge of the capacitance until it is fully charged, a saturable core (44) is provided around the resistive beampipe (40) to isolate the beampipe from the capacitance (42) until it is fully charged.

Aloe vera Derived Activated High-Surface-Area Carbon for Flexible and High-Energy Supercapacitors.

PubMed

Karnan, M; Subramani, K; Sudhan, N; Ilayaraja, N; Sathish, M

2016-12-28

Materials which possess high specific capacitance in device configuration with low cost are essential for viable application in supercapacitors. Herein, a flexible high-energy supercapacitor device was fabricated using porous activated high-surface-area carbon derived from aloe leaf (Aloe vera) as a precursor. The A. vera derived activated carbon showed mesoporous nature with high specific surface area of ∼1890 m 2 /g. A high specific capacitance of 410 and 306 F/g was achieved in three-electrode and symmetric two-electrode system configurations in aqueous electrolyte, respectively. The fabricated all-solid-state device showed a high specific capacitance of 244 F/g with an energy density of 8.6 Wh/kg. In an ionic liquid electrolyte, the fabricated device showed a high specific capacitance of 126 F/g and a wide potential window up to 3 V, which results in a high energy density of 40 Wh/kg. Furthermore, it was observed that the activation temperature has significant role in the electrochemical performance, as the activated sample at 700 °C showed best activity than the samples activated at 600 and 800 °C. The electron microscopic images (FE-SEM and HR-TEM) confirmed the formation of pores by the chemical activation. A fabricated supercapacitor device in ionic liquid with 3 V could power up a red LED for 30 min upon charging for 20s. Also, it is shown that the operation voltage and capacitance of flexible all-solid-state symmetric supercapacitors fabricated using aloe-derived activated carbon could be easily tuned by series and parallel combinations. The performance of fabricated supercapacitor devices using A. vera derived activated carbon in all-solid-state and ionic liquid indicates their viable applications in flexible devices and energy storage.

Direct current contamination of kilohertz frequency alternating current waveforms.

PubMed

Franke, Manfred; Bhadra, Niloy; Bhadra, Narendra; Kilgore, Kevin

2014-07-30

Kilohertz frequency alternating current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current- and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage- and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms. Published by Elsevier B.V.

Ultrafast Reverse Recovery Time Measurement for Wide-Bandgap Diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mauch, Daniel L.; Zutavern, Fred J.; Delhotal, Jarod J.

A system is presented that is capable of measuring sub-nanosecond reverse recovery times of diodes in wide-bandgap materials over a wide range of forward biases (0 – 1 A) and reverse voltages (0 – 10 kV). The system utilizes the step recovery technique and comprises a cable pulser based on a silicon (Si) Photoconductive Semiconductor Switch (PCSS) triggered with an Ultra Short Pulse Laser (USPL), a pulse charging circuit, a diode biasing circuit, and resistive and capacitive voltage monitors. The PCSS based cable pulser transmits a 130 ps rise time pulse down a transmission line to a capacitively coupled diode,more » which acts as the terminating element of the transmission line. The temporal nature of the pulse reflected by the diode provides the reverse recovery characteristics of the diode, measured with a high bandwidth capacitive probe integrated into the cable pulser. Furthermore, this system was used to measure the reverse recovery times (including the creation and charging of the depletion region) for two Avogy gallium nitride (GaN) diodes; the initial reverse recovery time was found to be 4 ns and varied minimally over reverse biases of 50 – 100 V and forward current of 1 – 100 mA.« less

Ultrafast Reverse Recovery Time Measurement for Wide-Bandgap Diodes

DOE PAGES

Mauch, Daniel L.; Zutavern, Fred J.; Delhotal, Jarod J.; ...

2017-03-01

A system is presented that is capable of measuring sub-nanosecond reverse recovery times of diodes in wide-bandgap materials over a wide range of forward biases (0 – 1 A) and reverse voltages (0 – 10 kV). The system utilizes the step recovery technique and comprises a cable pulser based on a silicon (Si) Photoconductive Semiconductor Switch (PCSS) triggered with an Ultra Short Pulse Laser (USPL), a pulse charging circuit, a diode biasing circuit, and resistive and capacitive voltage monitors. The PCSS based cable pulser transmits a 130 ps rise time pulse down a transmission line to a capacitively coupled diode,more » which acts as the terminating element of the transmission line. The temporal nature of the pulse reflected by the diode provides the reverse recovery characteristics of the diode, measured with a high bandwidth capacitive probe integrated into the cable pulser. Furthermore, this system was used to measure the reverse recovery times (including the creation and charging of the depletion region) for two Avogy gallium nitride (GaN) diodes; the initial reverse recovery time was found to be 4 ns and varied minimally over reverse biases of 50 – 100 V and forward current of 1 – 100 mA.« less

Two-Dimensional Porous Electrode Model for Capacitive Deionization

DOE PAGES

Hemmatifar, Ali; Stadermann, Michael; Santiago, Juan G.

2015-10-28

Here, ion transport in porous conductive materials is of great importance in a variety of electrochemical systems including batteries and supercapacitors. We here analyze the coupling of flow and charge transport and charge capacitance in capacitive deionization (CDI). In CDI, a pair of porous carbon electrodes is employed to electrostatically retain and remove ionic species from aqueous solutions. We here develop and solve a novel unsteady two-dimensional model for capturing the ion adsorption/desorption dynamics in a flow-between CDI system. We use this model to study the complex, nonlinear coupling between electromigration, diffusion, and advection of ions. We also fabricated amore » laboratory-scale CDI cell which we use to measure the near-equilibrium, cumulative adsorbed salt, and electric charge as a function of applied external voltage. We use these integral measures to validate and calibrate this model. We further present a detailed computational study of the spatiotemporal adsorption/desorption dynamics under constant voltage and constant flow conditions. We show results for low (20 mM KCl) and relatively high (200 mM KCl) inlet ion concentrations and identify effects of ion starvation on desalination. We show that in both cases electromigrative transport eventually becomes negligible and diffusive ion transport reduces the desalination rate.« less

Capacitively coupled hydrogen plasmas sustained by tailored voltage waveforms: excitation dynamics and ion flux asymmetry

DOE PAGES

Bruneau, B.; Diomede, P.; Economou, D. J.; ...

2016-06-08

Parallel plate capacitively coupled plasmas in hydrogen at relatively high pressure (~1 Torr) are excited with tailored voltage waveforms containing up to five frequencies. Predictions of a hybrid model combining a particle-in-cell simulation with Monte Carlo collisions and a fluid model are compared to phase resolved optical emission spectroscopy measurements, yielding information on the dynamics of the excitation rate in these discharges. When the discharge is excited with amplitude asymmetric waveforms, the discharge becomes electrically asymmetric, with different ion energies at each of the two electrodes. Unexpectedly, large differences in themore » $$\\text{H}_{2}^{+}$$ fluxes to each of the two electrodes are caused by the different $$\\text{H}_{3}^{+}$$ energies. When the discharge is excited with slope asymmetric waveforms, only weak electrical asymmetry of the discharge is observed. In this case, electron power absorption due to fast sheath expansion at one electrode is balanced by electron power absorption at the opposite electrode due to a strong electric field reversal.« less

Conduction-coupled Tesla transformer.

PubMed

Reed, J L

2015-03-01

A proof-of-principle Tesla transformer circuit is introduced. The new transformer exhibits the high voltage-high power output signal of shock-excited transformers. The circuit, with specification of proper circuit element values, is capable of obtaining extreme oscillatory voltages. The primary and secondary portions of the circuit communicate solely by conduction. The destructive arcing between the primary and secondary inductors in electromagnetically coupled transformers is ubiquitous. Flashover is eliminated in the new transformer as the high-voltage inductors do not interpenetrate and so do not possess an annular volume of electric field. The inductors are remote from one another. The high voltage secondary inductor is isolated in space, except for a base feed conductor, and obtains earth by its self-capacitance to the surroundings. Governing equations, for the ideal case of no damping, are developed from first principles. Experimental, theoretical, and circuit simulator data are presented for the new transformer. Commercial high-temperature superconductors are discussed as a means to eliminate the counter-intuitive damping due to small primary inductances in both the electromagnetic-coupled and new conduction-coupled transformers.

Anomalous or regular capacitance? The influence of pore size dispersity on double-layer formation

NASA Astrophysics Data System (ADS)

Jäckel, N.; Rodner, M.; Schreiber, A.; Jeongwook, J.; Zeiger, M.; Aslan, M.; Weingarth, D.; Presser, V.

2016-09-01

The energy storage mechanism of electric double-layer capacitors is governed by ion electrosorption at the electrode surface. This process requires high surface area electrodes, typically highly porous carbons. In common organic electrolytes, bare ion sizes are below one nanometer but they are larger when we consider their solvation shell. In contrast, ionic liquid electrolytes are free of solvent molecules, but cation-anion coordination requires special consideration. By matching pore size and ion size, two seemingly conflicting views have emerged: either an increase in specific capacitance with smaller pore size or a constant capacitance contribution of all micro- and mesopores. In our work, we revisit this issue by using a comprehensive set of electrochemical data and a pore size incremental analysis to identify the influence of certain ranges in the pore size distribution to the ion electrosorption capacity. We see a difference in solvation of ions in organic electrolytes depending on the applied voltage and a cation-anion interaction of ionic liquids in nanometer sized pores.

Transparent Flexible Active Faraday Cage Enables In Vivo Capacitance Measurement in Assembled Microsensor.

PubMed

Ahmadi, Mahdi; Rajamani, Rajesh; Sezen, Serdar

2017-10-01

Capacitive micro-sensors such as accelerometers, gyroscopes and pressure sensors are increasingly used in the modern electronic world. However, the in vivo use of capacitive sensing for measurement of pressure or other variables inside a human body suffers from significant errors due to stray capacitance. This paper proposes a solution consisting of a transparent thin flexible Faraday cage that surrounds the sensor. By supplying the active sensing voltage simultaneously to the deformable electrode of the capacitive sensor and to the Faraday cage, the stray capacitance during in vivo measurements can be largely eliminated. Due to the transparency of the Faraday cage, the top and bottom portions of a capacitive sensor can be accurately aligned and assembled together. Experimental results presented in the paper show that stray capacitance is reduced by a factor of 10 by the Faraday cage, when the sensor is subjected to a full immersion in water.

Off-set stabilizer for comparator output

DOEpatents

Lunsford, James S.

1991-01-01

A stabilized off-set voltage is input as the reference voltage to a comparator. In application to a time-interval meter, the comparator output generates a timing interval which is independent of drift in the initial voltage across the timing capacitor. A precision resistor and operational amplifier charge a capacitor to a voltage which is precisely offset from the initial voltage. The capacitance of the reference capacitor is selected so that substantially no voltage drop is obtained in the reference voltage applied to the comparator during the interval to be measured.

Mountain Plains Learning Experience Guide: Radio and T.V. Repair. Course: D.C. Circuits.

ERIC Educational Resources Information Center

Hoggatt, P.; And Others

One of four individualized courses included in a radio and television repair curriculum, this course deals with the basic electrical properties of current, voltage, resistance, magnetism, mutual induction, and capacitance. The course is comprised of ten units: (1) Current, (2) Voltage, (3) Resistance, (4) Measuring Voltage and Current in Series…

Effect of gate bias sweep rate on the threshold voltage of in-plane gate nanowire transistor

NASA Astrophysics Data System (ADS)

Liu, H. X.; Li, J.; Tan, R. R.

2018-01-01

In2O3 nanowire electric-double-layer (EDL) transistors with in-plane gate gated by SiO2 solid-electrolyte are fabricated on transparent glass substrates. The gate voltage sweep rates can effectively modulate the threshold voltage (Vth) of nanowire device. Both depletion mode and enhancement mode are realized, and the Vth shift of the nanowire transistors is estimated to be 0.73V (without light). This phenomenon is due to increased adsorption of oxygen on the nanowire surface by the slower gate voltage sweep rates. Adsorbed oxygens capture electrons and cause a surface of nanowire channel was depleted. The operation voltage of transistor was 1.0 V, because the EDL gate dielectric can lead to high gate dielectric capacitance. These transparent in-plane gate nanowire transistors are promising for “see-through” nanoscale sensors.

Nonlinear dynamics of capacitive charging and desalination by porous electrodes.

PubMed

Biesheuvel, P M; Bazant, M Z

2010-03-01

The rapid and efficient exchange of ions between porous electrodes and aqueous solutions is important in many applications, such as electrical energy storage by supercapacitors, water desalination and purification by capacitive deionization, and capacitive extraction of renewable energy from a salinity difference. Here, we present a unified mean-field theory for capacitive charging and desalination by ideally polarizable porous electrodes (without Faradaic reactions or specific adsorption of ions) valid in the limit of thin double layers (compared to typical pore dimensions). We illustrate the theory for the case of a dilute, symmetric, binary electrolyte using the Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae are available for salt adsorption and capacitive charging of the diffuse part of the double layer. We solve the full GCS mean-field theory numerically for realistic parameters in capacitive deionization, and we derive reduced models for two limiting regimes with different time scales: (i) in the "supercapacitor regime" of small voltages and/or early times, the porous electrode acts like a transmission line, governed by a linear diffusion equation for the electrostatic potential, scaled to the RC time of a single pore, and (ii) in the "desalination regime" of large voltages and long times, the porous electrode slowly absorbs counterions, governed by coupled, nonlinear diffusion equations for the pore-averaged potential and salt concentration.

Nonlinear dynamics of capacitive charging and desalination by porous electrodes

NASA Astrophysics Data System (ADS)

Biesheuvel, P. M.; Bazant, M. Z.

2010-03-01

The rapid and efficient exchange of ions between porous electrodes and aqueous solutions is important in many applications, such as electrical energy storage by supercapacitors, water desalination and purification by capacitive deionization, and capacitive extraction of renewable energy from a salinity difference. Here, we present a unified mean-field theory for capacitive charging and desalination by ideally polarizable porous electrodes (without Faradaic reactions or specific adsorption of ions) valid in the limit of thin double layers (compared to typical pore dimensions). We illustrate the theory for the case of a dilute, symmetric, binary electrolyte using the Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae are available for salt adsorption and capacitive charging of the diffuse part of the double layer. We solve the full GCS mean-field theory numerically for realistic parameters in capacitive deionization, and we derive reduced models for two limiting regimes with different time scales: (i) in the “supercapacitor regime” of small voltages and/or early times, the porous electrode acts like a transmission line, governed by a linear diffusion equation for the electrostatic potential, scaled to the RC time of a single pore, and (ii) in the “desalination regime” of large voltages and long times, the porous electrode slowly absorbs counterions, governed by coupled, nonlinear diffusion equations for the pore-averaged potential and salt concentration.

Scanning capacitance microscopy of ErAs nanoparticles embedded in GaAs pn junctions

NASA Astrophysics Data System (ADS)

Park, K. W.; Nair, H. P.; Crook, A. M.; Bank, S. R.; Yu, E. T.

2011-09-01

Scanning capacitance microscopy is used to characterize the electronic properties of ErAs nanoparticles embedded in GaAs pn junctions grown by molecular beam epitaxy. Voltage-dependent capacitance images reveal localized variations in subsurface electronic structure near buried ErAs nanoparticles at lateral length scales of 20-30 nm. Numerical modeling indicates that these variations arise from inhomogeneities in charge modulation due to Fermi level pinning behavior associated with the embedded ErAs nanoparticles. Statistical analysis of image data yields an average particle radius of 6-8 nm—well below the direct resolution limit in scanning capacitance microscopy but discernible via analysis of patterns in nanoscale capacitance images.

Maximizing the value of gate capacitance in field-effect devices using an organic interface layer

NASA Astrophysics Data System (ADS)

Kwok, H. L.

2015-12-01

Past research has confirmed the existence of negative capacitance in organics such as tris (8-Hydroxyquinoline) Aluminum (Alq3). This work explored using such an organic interface layer to enhance the channel voltage in the field-effect transistor (FET) thereby lowering the sub-threshold swing. In particular, if the values of the positive and negative gate capacitances are approximately equal, the composite negative capacitance will increase by orders of magnitude. One concern is the upper frequency limit (∼100 Hz) over which negative capacitance has been observed. Nonetheless, this frequency limit can be raised to kHz when the organic layer is subjected to a DC bias.

Three-dimensional vertical Si nanowire MOS capacitor model structure for the study of electrical versus geometrical Si nanowire characteristics

NASA Astrophysics Data System (ADS)

Hourdakis, E.; Casanova, A.; Larrieu, G.; Nassiopoulou, A. G.

2018-05-01

Three-dimensional (3D) Si surface nanostructuring is interesting towards increasing the capacitance density of a metal-oxidesemiconductor (MOS) capacitor, while keeping reduced footprint for miniaturization. Si nanowires (SiNWs) can be used in this respect. With the aim of understanding the electrical versus geometrical characteristics of such capacitors, we fabricated and studied a MOS capacitor with highly ordered arrays of vertical Si nanowires of different lengths and thermal silicon oxide dielectric, in comparison to similar flat MOS capacitors. The high homogeneity and ordering of the SiNWs allowed the determination of the single SiNW capacitance and intrinsic series resistance, as well as other electrical characteristics (density of interface states, flat-band voltage and leakage current) in relation to the geometrical characteristics of the SiNWs. The SiNW capacitors demonstrated increased capacitance density compared to the flat case, while maintaining a cutoff frequency above 1 MHz, much higher than in other reports in the literature. Finally, our model system has been shown to constitute an excellent platform for the study of SiNW capacitors with either grown or deposited dielectrics, as for example high-k dielectrics for further increasing the capacitance density. This will be the subject of future work.

Studying tantalum-based high-κ dielectrics in terms of capacitance measurements

NASA Astrophysics Data System (ADS)

Stojanovska-Georgievska, L.

2016-08-01

The trend of rapid development of microelectronics towards nano-miniaturization dictates the inevitable introduction of dielectrics with high permittivity (high-κ dielectrics), as alternative material for replacing SiO2. Therefore, studying these materials in terms of their characteristics, especially in terms of reliability, is of great importance for proper design and manufacture of devices. In this paper, alteration of capacitance in different frequency regimes is used, in order to determine the overall behavior of the material. Samples investigated here are MOS structures containing nanoscale tantalum based dielectrics. Layers of pure Ta2O5, but also Hf and Ti doped tantalum pentoxide, i.e. Ta2O5:Hf and Ta2O5:Ti are studied here. All samples are considered as ultrathin oxide layers with thicknesses less than 15 nm, obtained by radio frequent sputtering on p-type silicon substrate. Measuring capacitive characteristics enables determination of several specific parameters of the structures. The obtained results for capacitance in accumulation, the thickness and time evolution of the interfacial SiO2 layer, values of flatband and threshold voltage, density of oxide charges, interfacial and border states, and reliability properties favor the possibilities for more intensive use of studied materials in new nanoelectronic technologies.

Direct fabrication of 3D graphene on nanoporous anodic alumina by plasma-enhanced chemical vapor deposition

PubMed Central

Zhan, Hualin; Garrett, David J.; Apollo, Nicholas V.; Ganesan, Kumaravelu; Lau, Desmond; Prawer, Steven; Cervenka, Jiri

2016-01-01

High surface area electrode materials are of interest for a wide range of potential applications such as super-capacitors and electrochemical cells. This paper describes a fabrication method of three-dimensional (3D) graphene conformally coated on nanoporous insulating substrate with uniform nanopore size. 3D graphene films were formed by controlled graphitization of diamond-like amorphous carbon precursor films, deposited by plasma-enhanced chemical vapour deposition (PECVD). Plasma-assisted graphitization was found to produce better quality graphene than a simple thermal graphitization process. The resulting 3D graphene/amorphous carbon/alumina structure has a very high surface area, good electrical conductivity and exhibits excellent chemically stability, providing a good material platform for electrochemical applications. Consequently very large electrochemical capacitance values, as high as 2.1 mF for a sample of 10 mm3, were achieved. The electrochemical capacitance of the material exhibits a dependence on bias voltage, a phenomenon observed by other groups when studying graphene quantum capacitance. The plasma-assisted graphitization, which dominates the graphitization process, is analyzed and discussed in detail. PMID:26805546

Structure-based capacitance modeling and power loss analysis for the latest high-performance slant field-plate trench MOSFET

NASA Astrophysics Data System (ADS)

Kobayashi, Kenya; Sudo, Masaki; Omura, Ichiro

2018-04-01

Field-plate trench MOSFETs (FP-MOSFETs), with the features of ultralow on-resistance and very low gate–drain charge, are currently the mainstream of high-performance applications and their advancement is continuing as low-voltage silicon power devices. However, owing to their structure, their output capacitance (C oss), which leads to main power loss, remains to be a problem, especially in megahertz switching. In this study, we propose a structure-based capacitance model of FP-MOSFETs for calculating power loss easily under various conditions. Appropriate equations were modeled for C oss curves as three divided components. Output charge (Q oss) and stored energy (E oss) that were calculated using the model corresponded well to technology computer-aided design (TCAD) simulation, and we validated the accuracy of the model quantitatively. In the power loss analysis of FP-MOSFETs, turn-off loss was sufficiently suppressed, however, mainly Q oss loss increased depending on switching frequency. This analysis reveals that Q oss may become a significant issue in next-generation high-efficiency FP-MOSFETs.

Direct fabrication of 3D graphene on nanoporous anodic alumina by plasma-enhanced chemical vapor deposition.

PubMed

Zhan, Hualin; Garrett, David J; Apollo, Nicholas V; Ganesan, Kumaravelu; Lau, Desmond; Prawer, Steven; Cervenka, Jiri

2016-01-25

High surface area electrode materials are of interest for a wide range of potential applications such as super-capacitors and electrochemical cells. This paper describes a fabrication method of three-dimensional (3D) graphene conformally coated on nanoporous insulating substrate with uniform nanopore size. 3D graphene films were formed by controlled graphitization of diamond-like amorphous carbon precursor films, deposited by plasma-enhanced chemical vapour deposition (PECVD). Plasma-assisted graphitization was found to produce better quality graphene than a simple thermal graphitization process. The resulting 3D graphene/amorphous carbon/alumina structure has a very high surface area, good electrical conductivity and exhibits excellent chemically stability, providing a good material platform for electrochemical applications. Consequently very large electrochemical capacitance values, as high as 2.1 mF for a sample of 10 mm(3), were achieved. The electrochemical capacitance of the material exhibits a dependence on bias voltage, a phenomenon observed by other groups when studying graphene quantum capacitance. The plasma-assisted graphitization, which dominates the graphitization process, is analyzed and discussed in detail.

Research and Experiments on a Unipolar Capacitive Voltage Sensor

PubMed Central

Zhou, Qiang; He, Wei; Li, Songnong; Hou, Xingzhe

2015-01-01

Voltage sensors are an important part of the electric system. In service, traditional voltage sensors need to directly contact a high-voltage charged body. Sensors involve a large volume, complex insulation structures, and high design costs. Typically an iron core structure is adopted. As a result, ferromagnetic resonance can occur easily during practical application. Moreover, owing to the multilevel capacitor divider, the sensor cannot reflect the changes of measured voltage in time. Based on the electric field coupling principle, this paper designs a new voltage sensor; the unipolar structure design solves many problems of traditional voltage sensors like the great insulation design difficulty and high costs caused by grounding electrodes. A differential signal input structure is adopted for the detection circuit, which effectively restrains the influence of the common-mode interference signal. Through sensor modeling, simulation and calculations, the structural design of the sensor electrode was optimized, miniaturization of the sensor was realized, the voltage division ratio of the sensor was enhanced, and the phase difference of sensor measurement was weakened. The voltage sensor is applied to a single-phase voltage class line of 10 kV for testing. According to the test results, the designed sensor is able to meet the requirements of accurate and real-time measurement for voltage of the charged conductor as well as to provide a new method for electricity larceny prevention and on-line monitoring of the power grid in an electric system. Therefore, it can satisfy the development demands of the smart power grid. PMID:26307992

Fluid simulation of the bias effect in inductive/capacitive discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yu-Ru; Research Group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, Wilrijk, BE-2610 Antwerp; Gao, Fei

Computer simulations are performed for an argon inductively coupled plasma (ICP) with a capacitive radio-frequency bias power, to investigate the bias effect on the discharge mode transition and on the plasma characteristics at various ICP currents, bias voltages, and bias frequencies. When the bias frequency is fixed at 13.56 MHz and the ICP current is low, e.g., 6 A, the spatiotemporal averaged plasma density increases monotonically with bias voltage, and the bias effect is already prominent at a bias voltage of 90 V. The maximum of the ionization rate moves toward the bottom electrode, which indicates clearly the discharge mode transition in inductive/capacitivemore » discharges. At higher ICP currents, i.e., 11 and 13 A, the plasma density decreases first and then increases with bias voltage, due to the competing mechanisms between the ion acceleration power dissipation and the capacitive power deposition. At 11 A, the bias effect is still important, but it is noticeable only at higher bias voltages. At 13 A, the ionization rate is characterized by a maximum at the reactor center near the dielectric window at all selected bias voltages, which indicates that the ICP power, instead of the bias power, plays a dominant role under this condition, and no mode transition is observed. Indeed, the ratio of the bias power to the total power is lower than 0.4 over a wide range of bias voltages, i.e., 0–300 V. Besides the effect of ICP current, also the effect of various bias frequencies is investigated. It is found that the modulation of the bias power to the spatiotemporal distributions of the ionization rate at 2 MHz is strikingly different from the behavior observed at higher bias frequencies. Furthermore, the minimum of the plasma density appears at different bias voltages, i.e., 120 V at 2 MHz and 90 V at 27.12 MHz.« less

Conducted noise analysis and protection of 45 kJ/s, ±50 kV capacitor charging power supply when interfaced with repetitive Marx based pulse power system.

PubMed

Naresh, P; Patel, Ankur; Sharma, Archana

2015-09-01

Pulse power systems with highly dynamic loads like klystron, backward wave oscillator (BWO), and magnetron generate highly dynamic noise. This noise leads to frequent failure of controlled switches in the inverter stage of charging power supply. Designing a reliable and compatible power supply for pulse power applications is always a tricky job when charging rate is in multiples of 10 kJ/s. A ±50 kV and 45 kJ/s capacitor charging power supply based on 4th order LCLC resonant topology has been developed for a 10 Hz repetitive Marx based system. Conditions for load independent constant current and zero current switching (ZCS) are derived mathematically. Noise generated at load end due to dynamic load is tackled effectively and reduction in magnitude noise voltage is achieved by providing shielding between primary and secondary of high voltage high frequency transformer and with LCLC low pass filter. Shielding scales down the ratio between coupling capacitance (Cc) and the collector-emitter capacitance of insulated gate bi-polar transistor switch, which in turn reduces the common mode noise voltage magnitude. The proposed 4th order LCLC resonant network acts as a low pass filter for differential mode noise in the reverse direction (from load to source). Power supply has been tested repeatedly with 5 Hz repetition rate with repetitive Marx based system connected with BWO load working fine without failure of single switch in the inverter stage.

Conducted noise analysis and protection of 45 kJ/s, ±50 kV capacitor charging power supply when interfaced with repetitive Marx based pulse power system

NASA Astrophysics Data System (ADS)

Naresh, P.; Patel, Ankur; Sharma, Archana

2015-09-01

Pulse power systems with highly dynamic loads like klystron, backward wave oscillator (BWO), and magnetron generate highly dynamic noise. This noise leads to frequent failure of controlled switches in the inverter stage of charging power supply. Designing a reliable and compatible power supply for pulse power applications is always a tricky job when charging rate is in multiples of 10 kJ/s. A ±50 kV and 45 kJ/s capacitor charging power supply based on 4th order LCLC resonant topology has been developed for a 10 Hz repetitive Marx based system. Conditions for load independent constant current and zero current switching (ZCS) are derived mathematically. Noise generated at load end due to dynamic load is tackled effectively and reduction in magnitude noise voltage is achieved by providing shielding between primary and secondary of high voltage high frequency transformer and with LCLC low pass filter. Shielding scales down the ratio between coupling capacitance (Cc) and the collector-emitter capacitance of insulated gate bi-polar transistor switch, which in turn reduces the common mode noise voltage magnitude. The proposed 4th order LCLC resonant network acts as a low pass filter for differential mode noise in the reverse direction (from load to source). Power supply has been tested repeatedly with 5 Hz repetition rate with repetitive Marx based system connected with BWO load working fine without failure of single switch in the inverter stage.

Environmentally friendly power generator based on moving liquid dielectric and double layer effect.

PubMed

Huynh, D H; Nguyen, T C; Nguyen, P D; Abeyrathne, C D; Hossain, Md S; Evans, R; Skafidas, E

2016-06-03

An electrostatic power generator converts mechanical energy to electrical energy by utilising the principle of variable capacitance. This change in capacitance is usually achieved by varying the gap or overlap between two parallel metallic plates. This paper proposes a novel electrostatic micro power generator where the change in capacitance is achieved by the movement of an aqueous solution of NaCl. A significant change in capacitance is achieved due to the higher than air dielectric constant of water and the Helmholtz double layer capacitor formed by ion separation at the electrode interfaces. The proposed device has significant advantages over traditional electrostatic devices which include low bias voltage and low mechanical frequency of operation. This is critical if the proposed device is to have utility in harvesting power from the environment. A figure of merit exceeding 10000(10(8)μW)/(mm(2)HzV(2)) which is two orders of magnitude greater than previous devices, is demonstrated for a prototype operating at a bias voltage of 1.2 V and a droplet frequency of 6 Hz. Concepts are presented for large scale power harvesting.

High-performance supercapacitors based on vertically aligned carbon nanotubes and nonaqueous electrolytes

NASA Astrophysics Data System (ADS)

Kim, Byungwoo; Chung, Haegeun; Kim, Woong

2012-04-01

We demonstrate the high performance of supercapacitors fabricated with vertically aligned carbon nanotubes and nonaqueous electrolytes such as ionic liquids and conventional organic electrolytes. Specific capacitance, maximum power and energy density of the supercapacitor measured in ionic liquid were ˜75 F g-1, ˜987 kW kg-1 and ˜27 W h kg-1, respectively. The high power performance was consistently indicated by a fast relaxation time constant of 0.2 s. In addition, electrochemical oxidation of the carbon nanotubes improved the specific capacitance (˜158 F g-1) and energy density (˜53 W h kg-1). Both high power and energy density could be attributed to the fast ion transport realized by the alignment of carbon nanotubes and the wide operational voltage defined by the ionic liquid. The demonstrated carbon-nanotube- and nonaqueous-electrolyte-based supercapacitors show great potential for the development of high-performance energy storage devices.

High-performance supercapacitors based on vertically aligned carbon nanotubes and nonaqueous electrolytes.

PubMed

Kim, Byungwoo; Chung, Haegeun; Kim, Woong

2012-04-20

We demonstrate the high performance of supercapacitors fabricated with vertically aligned carbon nanotubes and nonaqueous electrolytes such as ionic liquids and conventional organic electrolytes. Specific capacitance, maximum power and energy density of the supercapacitor measured in ionic liquid were ~75 F g(-1), ~987 kW kg(-1) and ~27 W h kg(-1), respectively. The high power performance was consistently indicated by a fast relaxation time constant of 0.2 s. In addition, electrochemical oxidation of the carbon nanotubes improved the specific capacitance (~158 F g(-1)) and energy density (~53 W h kg(-1)). Both high power and energy density could be attributed to the fast ion transport realized by the alignment of carbon nanotubes and the wide operational voltage defined by the ionic liquid. The demonstrated carbon-nanotube- and nonaqueous-electrolyte-based supercapacitors show great potential for the development of high-performance energy storage devices. © 2012 IOP Publishing Ltd

Gate tunneling current and quantum capacitance in metal-oxide-semiconductor devices with graphene gate electrodes

NASA Astrophysics Data System (ADS)

An, Yanbin; Shekhawat, Aniruddh; Behnam, Ashkan; Pop, Eric; Ural, Ant

2016-11-01

Metal-oxide-semiconductor (MOS) devices with graphene as the metal gate electrode, silicon dioxide with thicknesses ranging from 5 to 20 nm as the dielectric, and p-type silicon as the semiconductor are fabricated and characterized. It is found that Fowler-Nordheim (F-N) tunneling dominates the gate tunneling current in these devices for oxide thicknesses of 10 nm and larger, whereas for devices with 5 nm oxide, direct tunneling starts to play a role in determining the total gate current. Furthermore, the temperature dependences of the F-N tunneling current for the 10 nm devices are characterized in the temperature range 77-300 K. The F-N coefficients and the effective tunneling barrier height are extracted as a function of temperature. It is found that the effective barrier height decreases with increasing temperature, which is in agreement with the results previously reported for conventional MOS devices with polysilicon or metal gate electrodes. In addition, high frequency capacitance-voltage measurements of these MOS devices are performed, which depict a local capacitance minimum under accumulation for thin oxides. By analyzing the data using numerical calculations based on the modified density of states of graphene in the presence of charged impurities, it is shown that this local minimum is due to the contribution of the quantum capacitance of graphene. Finally, the workfunction of the graphene gate electrode is extracted by determining the flat-band voltage as a function of oxide thickness. These results show that graphene is a promising candidate as the gate electrode in metal-oxide-semiconductor devices.

Electrical description of N2 capacitively coupled plasmas with the global model

NASA Astrophysics Data System (ADS)

Cao, Ming-Lu; Lu, Yi-Jia; Cheng, Jia; Ji, Lin-Hong; Engineering Design Team

2016-10-01

N2 discharges in a commercial capacitively coupled plasma reactor are modelled by a combination of an equivalent circuit and the global model, for a range of gas pressure at 1 4 Torr. The ohmic and inductive plasma bulk and the capacitive sheath are represented as LCR elements, with electrical characteristics determined by plasma parameters. The electron density and electron temperature are obtained from the global model in which a Maxwellian electron distribution is assumed. Voltages and currents are recorded by a VI probe installed after the match network. Using the measured voltage as an input, the current flowing through the discharge volume is calculated from the electrical model and shows excellent agreement with the measurements. The experimentally verified electrical model provides a simple and accurate description for the relationship between the external electrical parameters and the plasma properties, which can serve as a guideline for process window planning in industrial applications.

Comprehensive electrical analysis of metal/Al2O3/O-terminated diamond capacitance

NASA Astrophysics Data System (ADS)

Pham, T. T.; Maréchal, A.; Muret, P.; Eon, D.; Gheeraert, E.; Rouger, N.; Pernot, J.

2018-04-01

Metal oxide semiconductor capacitors were fabricated using p - type oxygen-terminated (001) diamond and Al2O3 deposited by atomic layer deposition at two different temperatures 250 °C and 380 °C. Current voltage I(V), capacitance voltage C(V), and capacitance frequency C(f) measurements were performed and analyzed for frequencies ranging from 1 Hz to 1 MHz and temperatures from 160 K to 360 K. A complete model for the Metal-Oxide-Semiconductor Capacitors electrostatics, leakage current mechanisms through the oxide into the semiconductor and small a.c. signal equivalent circuit of the device is proposed and discussed. Interface states densities are then evaluated in the range of 1012eV-1cm-2 . The strong Fermi level pinning is demonstrated to be induced by the combined effects of the leakage current through the oxide and the presence of diamond/oxide interface states.

High-frequency carbon supercapacitors from polyfurfuryl alcohol

NASA Astrophysics Data System (ADS)

Ruiz, V.; Pandolfo, A. G.

Porous carbons with controllable and narrow pore-size distributions are prepared from the chemical activation of polyfurfuryl alcohol (PFA). High apparent BET surface areas, up to 2600 m 2 g -1 (2611 m 2 g -1 by Density Functional Theory (DFT)), and good electrical conductivities (up to ∼130 S cm -1) are obtained. By varying the potassium hydroxide: carbon precursor ratio, the preparation of carbons with different proportions of micro- and fine mesoporosity (<5 nm) can be tailored to provide an ideal electronic and ionic pore structure for electrochemical energy-storage devices, such as electrical double-layer capacitors. High specific capacitance values are obtained up to 147 F g -1 in a voltage window of 2.5 V using 1 M tetraethyl ammonium tetrafluoroborate in acetonitrile. Moreover, excellent high-current and high-frequency performance is demonstrated: 100 F g -1 at 225 A g -1 (10 Hz) and ∼30 F g -1 at 100 Hz. When comparing the performance with commercial activated carbons (ACs) of similar textural properties, the PFA-derived ACs demonstrated better performance in terms of higher capacitance values and improved rate capabilities. There is a 125% increase in capacitance values at 1 kHz.

Development of AC-coupled, poly-silicon biased, p-on-n silicon strip detectors in India for HEP experiments

NASA Astrophysics Data System (ADS)

Jain, Geetika; Dalal, Ranjeet; Bhardwaj, Ashutosh; Ranjan, Kirti; Dierlamm, Alexander; Hartmann, Frank; Eber, Robert; Demarteau, Marcel

2018-02-01

P-on-n silicon strip sensors having multiple guard-ring structures have been developed for High Energy Physics applications. The study constitutes the optimization of the sensor design, and fabrication of AC-coupled, poly-silicon biased sensors of strip width of 30 μm and strip pitch of 55 μm. The silicon wafers used for the fabrication are of 4 inch n-type, having an average resistivity of 2-5 k Ω cm, with a thickness of 300 μm. The electrical characterization of these detectors comprises of: (a) global measurements of total leakage current, and backplane capacitance; (b) strip and voltage scans of strip leakage current, poly-silicon resistance, interstrip capacitance, interstrip resistance, coupling capacitance, and dielectric current; and (c) charge collection measurements using ALiBaVa setup. The results of the same are reported here.

Low-Cost and High-Productivity Three-Dimensional Nanocapacitors Based on Stand-Up ZnO Nanowires for Energy Storage.

PubMed

Wei, Lei; Liu, Qi-Xuan; Zhu, Bao; Liu, Wen-Jun; Ding, Shi-Jin; Lu, Hong-Liang; Jiang, Anquan; Zhang, David Wei

2016-12-01

Highly powered electrostatic capacitors based on nanostructures with a high aspect ratio are becoming critical for advanced energy storage technology because of their high burst power and energy storage capability. We report the fabrication process and the electrical characteristics of high capacitance density capacitors with three-dimensional solid-state nanocapacitors based on a ZnO nanowire template. Stand-up ZnO nanowires are grown face down on p-type Si substrates coated with a ZnO seed layer using a hydrothermal method. Stacks of AlZnO/Al2O3/AlZnO are then deposited sequentially on the ZnO nanowires using atomic layer deposition. The fabricated capacitor has a high capacitance density up to 92 fF/μm(2) at 1 kHz (around ten times that of the planar capacitor without nanowires) and an extremely low leakage current density of 3.4 × 10(-8) A/cm(2) at 2 V for a 5-nm Al2O3 dielectric. Additionally, the charge-discharge characteristics of the capacitor were investigated, indicating that the resistance-capacitance time constants were 550 ns for both the charging and discharging processes and the time constant was not dependent on the voltage. This reflects good power characteristics of the fabricated capacitors. Therefore, the current work provides an exciting strategy to fabricate low-cost and easily processable, high capacitance density capacitors for energy storage.

A compact model for selectors based on metal doped electrolyte

NASA Astrophysics Data System (ADS)

Zhang, Lu; Song, Wenhao; Yang, J. Joshua; Li, Hai; Chen, Yiran

2018-04-01

A selector device that demonstrates high nonlinearity and low switching voltages was fabricated using HfOx as a solid electrolyte doped with Ag electrodes. The electronic conductance of the volatile conductive filaments responsible for the switching was studied under both static and dynamic conditions. A compact model is developed from this study that describes the physical processes of the formation and rupture of the Ag filament(s). A dynamic capacitance model is used to fit the transient current traces under different voltage bias, which enables the extraction of parameters associated with the various parasitic components in the device.

Frequency dispersion analysis of thin dielectric MOS capacitor in a five-element model

NASA Astrophysics Data System (ADS)

Zhang, Xizhen; Zhang, Sujuan; Zhu, Huichao; Pan, Xiuyu; Cheng, Chuanhui; Yu, Tao; Li, Xiangping; Cheng, Yi; Xing, Guichao; Zhang, Daming; Luo, Xixian; Chen, Baojiu

2018-02-01

An Al/ZrO2/IL/n-Si (IL: interface layer) MOS capacitor has been fabricated by metal organic decomposition of ZrO2 and thermal deposition Al. We have measured parallel capacitance (C m) and parallel resistance (R m) versus bias voltage curves (C m, R m-V) at different AC signal frequency (f), and C m, R m-f curves at different bias voltage. The curves of C m, R m-f measurements show obvious frequency dispersion in the range of 100 kHz-2 MHz. The energy band profile shows that a large voltage is applied on the ZrO2 layer and IL at accumulation, which suggests possible dielectric polarization processes by some traps in ZrO2 and IL. C m, R m-f data are used for frequency dispersion analysis. To exclude external frequency dispersion, we have extracted the parameters of C (real MOS capacitance), R p (parallel resistance), C IL (IL capacitance), R IL (IL resistance) and R s (Si resistance) in a five-element model by using a three-frequency method. We have analyzed intrinsic frequency dispersion of C, R p, C IL, R IL and R s by studying the dielectric characteristics and Si surface layer characteristics. At accumulation, the dispersion of C and R p is attributed to dielectric polarization such as dipolar orientation and oxide traps. The serious dispersion of C IL and R IL are relative to other dielectric polarization, such as border traps and fixed oxide traps. The dispersion of R s is mainly attributed to contact capacitance (C c) and contact resistance (R c). At depletion and inversion, the frequency dispersion of C, R p, C IL, R IL, and R s are mainly attributed to the depletion layer capacitance (C D). The interface trap capacitance (C it) and interface trap resistance (R it) are not dominant for the dispersion of C, R p, C IL, R IL, and R s.

Safe and consistent method of spot-welding platinum thermocouple wires and foils for high temperature measurements.

PubMed

Orr, G; Roth, M

2012-08-01

A low-voltage (mV) electronically triggered spot welding system for fabricating fine thermocouples and thin sheets used in high-temperature characterization of materials' properties is suggested. The system is based on the capacitance discharge method with a timed trigger for obtaining reliable and consistent welds. In contrast to existing techniques based on employing high voltage DC supplies for charging the capacitor or supplies with positive and negative rails, this method uses a simple, standard dual power supply available at most of the physical laboratories or can be acquired at a low cost. In addition, an efficient and simple method of fabricating non-sticking electrodes that do not contaminate the weld area is suggested and implemented.

A method for computing ion energy distributions for multifrequency capacitive discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Alan C. F.; Lieberman, M. A.; Verboncoeur, J. P.

2007-03-01

The ion energy distribution (IED) at a surface is an important parameter for processing in multiple radio frequency driven capacitive discharges. An analytical model is developed for the IED in a low pressure discharge based on a linear transfer function that relates the time-varying sheath voltage to the time-varying ion energy response at the surface. This model is in good agreement with particle-in-cell simulations over a wide range of single, dual, and triple frequency driven capacitive discharge excitations.

Characterization system for research on energy storage capacitors.

PubMed

Noriega, J R; Iyore, O D; Budime, C; Gnade, B; Vasselli, J

2013-05-01

In this work a characterization system for high energy-density capacitors is described and demonstrated. Capacitors are being designed using thin-film technology in an attempt to achieve higher energy-density levels by operating the devices at a high voltage. These devices are fabricated from layers of 100 nm aluminum and a layer of polyvinylidene fluoride-hexafluoropropylene on a polyethylene naphthalate plastic substrate. The devices have been designed to store electrical charge at up to 200 V. Characterizations of these devices focus on the measurement of capacitance vs bias voltage and temperature, equivalent series resistance, and charge/discharge cycles. For the purpose of the characterization of these capacitors, an electronic charge/discharge interface was designed and tested.

Fiber-reinforced dielectric elastomer laminates with integrated function of actuating and sensing

NASA Astrophysics Data System (ADS)

Li, Tiefeng; Xie, Yuhan; Li, Chi; Yang, Xuxu; Jin, Yongbin; Liu, Junjie; Huang, Xiaoqiang

2015-04-01

The natural limbs of animals and insects integrate muscles, skins and neurons, providing both the actuating and sensing functions simultaneously. Inspired by the natural structure, we present a novel structure with integrated function of actuating and sensing with dielectric elastomer (DE) laminates. The structure can deform when subjected to high voltage loading and generate corresponding output signal in return. We investigate the basic physical phenomenon of dielectric elastomer experimentally. It is noted that when applying high voltage, the actuating dielectric elastomer membrane deforms and the sensing dielectric elastomer membrane changes the capacitance in return. Based on the concept, finite element method (FEM) simulation has been conducted to further investigate the electromechanical behavior of the structure.

Physical Theory of Voltage Fade in Lithium- and Manganese-Rich Transition Metal Oxides

DOE PAGES

Rinaldo, Steven G.; Gallagher, Kevin G.; Long, Brandon R.; ...

2015-03-04

Lithium- and manganese-rich (LMR) transition metal oxide cathodes are of interest for lithium-ion battery applications due to their increased energy density and decreased cost. However, the advantages in energy density and cost are offset, in part, due to the phenomena of voltage fade. Specifically, the voltage profiles (voltage as a function of capacity) of LMR cathodes transform from a high energy configuration to a lower energy configuration as they are repeatedly charged (Li removed) and discharged (Li inserted). Here, we propose a physical model of voltage fade that accounts for the emergence of a low voltage Li phase due tomore » the introduction of transition metal ion defects within a parent Li phase. The phenomenological model was re-cast in a general form and experimental LMR charge profiles were de-convoluted to extract the evolutionary behavior of various components of LMR capacitance profiles. Evolution of the voltage fade component was found to follow a universal growth curve with a maximal voltage fade capacity of ≈ 20% of the initial total capacity.« less

Performance improvement of organic thin film transistors by using active layer with sandwich structure

NASA Astrophysics Data System (ADS)

Ni, Yao; Zhou, Jianlin; Kuang, Peng; Lin, Hui; Gan, Ping; Hu, Shengdong; Lin, Zhi

2017-08-01

We report organic thin film transistors (OTFTs) with pentacene/fluorinated copper phthalo-cyanine (F16CuPc)/pentacene (PFP) sandwich configuration as active layers. The sandwich devices not only show hole mobility enhancement but also present a well control about threshold voltage and off-state current. By investigating various characteristics, including current-voltage hysteresis, organic film morphology, capacitance-voltage curve and resistance variation of active layers carefully, it has been found the performance improvement is mainly attributed to the low carrier traps and the higher conductivity of the sandwich active layer due to the additional induced carriers in F16CuPc/pentacene. Therefore, using proper multiple active layer is an effective way to gain high performance OTFTs.

Study and Experiment on Non-Contact Voltage Sensor Suitable for Three-Phase Transmission Line

PubMed Central

Zhou, Qiang; He, Wei; Xiao, Dongping; Li, Songnong; Zhou, Kongjun

2015-01-01

A voltage transformer, as voltage signal detection equipment, plays an important role in a power system. Presently, more and more electric power systems are adopting potential transformer and capacitance voltage transformers. Transformers are often large in volume and heavyweight, their insulation design is difficult, and an iron core or multi-grade capacitance voltage division structure is generally adopted. As a result, the detection accuracy of transformer is reduced, a huge phase difference exists between detection signal and voltage signal to be measured, and the detection signal cannot accurately and timely reflect the change of conductor voltage signal to be measured. By aiming at the current problems of electric transformation, based on electrostatic induction principle, this paper designed a non-contact voltage sensor and gained detection signal of the sensor through electrostatic coupling for the electric field generated by electric charges of the conductor to be measured. The insulation structure design of the sensor is simple and its volume is small; phase difference of sensor measurement is effectively reduced through optimization design of the electrode; and voltage division ratio and measurement accuracy are increased. The voltage sensor was tested on the experimental platform of simulating three-phase transmission line. According to the result, the designed non-contact voltage sensor can realize accurate and real-time measurement for the conductor voltage. It can be applied to online monitoring for the voltage of three-phase transmission line or three-phase distribution network line, which is in accordance with the development direction of the smart grid. PMID:26729119

Study and Experiment on Non-Contact Voltage Sensor Suitable for Three-Phase Transmission Line.

PubMed

Zhou, Qiang; He, Wei; Xiao, Dongping; Li, Songnong; Zhou, Kongjun

2015-12-30

A voltage transformer, as voltage signal detection equipment, plays an important role in a power system. Presently, more and more electric power systems are adopting potential transformer and capacitance voltage transformers. Transformers are often large in volume and heavyweight, their insulation design is difficult, and an iron core or multi-grade capacitance voltage division structure is generally adopted. As a result, the detection accuracy of transformer is reduced, a huge phase difference exists between detection signal and voltage signal to be measured, and the detection signal cannot accurately and timely reflect the change of conductor voltage signal to be measured. By aiming at the current problems of electric transformation, based on electrostatic induction principle, this paper designed a non-contact voltage sensor and gained detection signal of the sensor through electrostatic coupling for the electric field generated by electric charges of the conductor to be measured. The insulation structure design of the sensor is simple and its volume is small; phase difference of sensor measurement is effectively reduced through optimization design of the electrode; and voltage division ratio and measurement accuracy are increased. The voltage sensor was tested on the experimental platform of simulating three-phase transmission line. According to the result, the designed non-contact voltage sensor can realize accurate and real-time measurement for the conductor voltage. It can be applied to online monitoring for the voltage of three-phase transmission line or three-phase distribution network line, which is in accordance with the development direction of the smart grid.

Extraction of sub-gap density of states via capacitance-voltage measurement for the erasing process in a TFT charge-trapping memory

NASA Astrophysics Data System (ADS)

Chiang, Yen-Chang; Hsiao, Yang-Hsuan; Li, Jeng-Ting; Chen, Jen-Sue

2018-02-01

Charge-trapping memories (CTMs) based on zinc tin oxide (ZTO) semiconductor thin-film transistors (TFTs) can be programmed by a positive gate voltage and erased by a negative gate voltage in conjunction with light illumination. To understand the mechanism involved, the sub-gap density of states associated with ionized oxygen vacancies in the ZTO active layer is extracted from optical response capacitance-voltage (C-V) measurements. The corresponding energy states of ionized oxygen vacancies are observed below the conduction band minimum at approximately 0.5-1.0 eV. From a comparison of the fitted oxygen vacancy concentration in the CTM-TFT after the light-bias erasing operation, it is found that the pristine-erased device contains more oxygen vacancies than the program-erased device because the trapped electrons in the programmed device are pulled into the active layer and neutralized by the oxygen vacancies that are present there.

Impact of magnetite nanoparticle incorporation on optical and electrical properties of nanocomposite LbL assemblies.

PubMed

Yashchenok, Alexey M; Gorin, Dmitry A; Badylevich, Mikhail; Serdobintsev, Alexey A; Bedard, Matthieu; Fedorenko, Yanina G; Khomutov, Gennady B; Grigoriev, Dmitri O; Möhwald, Helmuth

2010-09-21

Optical and electrical properties of polyelectrolyte/iron oxide nanocomposite planar films on silicon substrates were investigated for different amount of iron oxide nanoparticles incorporated in the films. The nanocomposite assemblies prepared by the layer-by-layer assembly technique were characterized by ellipsometry, atomic force microscopy, and secondary ion mass-spectrometry. Absorption spectra of the films reveal a shift of the optical absorption edge to higher energy when the number of deposited layers decreases. Capacitance-voltage and current-voltage measurements were applied to study the electrical properties of metal-oxide-semiconductor structures prepared by thermal evaporation of gold electrodes on nanocomposite films. The capacitance-voltage measurements show that the dielectric constant of the film increases with the number of deposited layers and the fixed charge and the trapped charge densities have a negative sign.

A novel flexible capacitive touch pad based on graphene oxide film.

PubMed

Tian, He; Yang, Yi; Xie, Dan; Ren, Tian-Ling; Shu, Yi; Zhou, Chang-Jian; Sun, Hui; Liu, Xuan; Zhang, Cang-Hai

2013-02-07

Recently, graphene oxide (GO) supercapacitors with ultra-high energy densities have received significant attention. In addition to energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as vibration and sound energy harvesting. Here, we experimentally create a macroscopic flexible capacitive touch pad based on GO film. An obvious touch "ON" to "OFF" voltage ratio up to ∼60 has been observed. Moreover, we tested the capacitor structure on both flat and curved surfaces and it showed high response sensitivity under fast touch rates. Collectively, our results raise the exciting prospect that the realization of macroscopic flexible keyboards with large-area graphene based materials is technologically feasible, which may open up important applications in control and interface design for solar cells, speakers, supercapacitors, batteries and MEMS systems.

A novel flexible capacitive touch pad based on graphene oxide film

NASA Astrophysics Data System (ADS)

Tian, He; Yang, Yi; Xie, Dan; Ren, Tian-Ling; Shu, Yi; Zhou, Chang-Jian; Sun, Hui; Liu, Xuan; Zhang, Cang-Hai

2013-01-01

Recently, graphene oxide (GO) supercapacitors with ultra-high energy densities have received significant attention. In addition to energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as vibration and sound energy harvesting. Here, we experimentally create a macroscopic flexible capacitive touch pad based on GO film. An obvious touch ``ON'' to ``OFF'' voltage ratio up to ~60 has been observed. Moreover, we tested the capacitor structure on both flat and curved surfaces and it showed high response sensitivity under fast touch rates. Collectively, our results raise the exciting prospect that the realization of macroscopic flexible keyboards with large-area graphene based materials is technologically feasible, which may open up important applications in control and interface design for solar cells, speakers, supercapacitors, batteries and MEMS systems.

A Novel Slicing Method for Thin Supercapacitors.

PubMed

Sun, Hao; Fu, Xuemei; Xie, Songlin; Jiang, Yishu; Guan, Guozhen; Wang, Bingjie; Li, Houpu; Peng, Huisheng

2016-08-01

Thin and flexible supercapacitors with low cost and individual variation are fabricated by a new and efficient slicing method. Tunable output voltage and energy can be realized with a high specific capacitance of 248.8 F g(-1) or 150.8 F cm(-3) , which is well maintained before and after bending. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Resonant snubber inverter

DOEpatents

Lai, Jih-Sheng; Young, Sr., Robert W.; Chen, Daoshen; Scudiere, Matthew B.; Ott, Jr., George W.; White, Clifford P.; McKeever, John W.

1997-01-01

A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter.

Resonant snubber inverter

DOEpatents

Lai, J.S.; Young, R.W. Sr.; Chen, D.; Scudiere, M.B.; Ott, G.W. Jr.; White, C.P.; McKeever, J.W.

1997-06-24

A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter. 14 figs.

Critical factors to achieve low voltage- and capacitance-based organic field-effect transistors.

PubMed

Jang, Mi; Park, Ji Hoon; Im, Seongil; Kim, Se Hyun; Yang, Hoichang

2014-01-15

Hydrophobic organo-compatible but low-capacitance dielectrics (10.5 nFcm(-2) ), polystyrene-grafted SiO2 could induce surface-mediated large crystal grains of face-to-face stacked triethylsilylethynyl anthradithiophene (TES-ADT), producing more efficient charge-carrier transport, in comparison to μm-sized pentacene crystals containing a face-to-edge packing. Low-voltage operating TES-ADT OFETs showed good device performance (μFET ≈ 1.3 cm(2) V(-1) s(-1) , Vth ≈ 0.5 V, SS ≈ 0.2 V), as well as excellent device reliability. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

a New Approach for Accuracy Improvement of Pulsed LIDAR Remote Sensing Data

NASA Astrophysics Data System (ADS)

Zhou, G.; Huang, W.; Zhou, X.; He, C.; Li, X.; Huang, Y.; Zhang, L.

2018-05-01

In remote sensing applications, the accuracy of time interval measurement is one of the most important parameters that affect the quality of pulsed lidar data. The traditional time interval measurement technique has the disadvantages of low measurement accuracy, complicated circuit structure and large error. A high-precision time interval data cannot be obtained in these traditional methods. In order to obtain higher quality of remote sensing cloud images based on the time interval measurement, a higher accuracy time interval measurement method is proposed. The method is based on charging the capacitance and sampling the change of capacitor voltage at the same time. Firstly, the approximate model of the capacitance voltage curve in the time of flight of pulse is fitted based on the sampled data. Then, the whole charging time is obtained with the fitting function. In this method, only a high-speed A/D sampler and capacitor are required in a single receiving channel, and the collected data is processed directly in the main control unit. The experimental results show that the proposed method can get error less than 3 ps. Compared with other methods, the proposed method improves the time interval accuracy by at least 20 %.

Alternate charging and discharging of capacitor to enhance the electron production of bioelectrochemical systems.

PubMed

Liang, Peng; Wu, Wenlong; Wei, Jincheng; Yuan, Lulu; Xia, Xue; Huang, Xia

2011-08-01

A bioelectrochemical system (BES) can be operated in both "microbial fuel cell" (MFC) and "microbial electrolysis cell" (MEC) modes, in which power is delivered and invested respectively. To enhance the electric current production, a BES was operated in MFC mode first and a capacitor was used to collect power from the system. Then the charged capacitor discharged electrons to the system itself, switching into MEC mode. This alternate charging and discharging (ACD) mode helped the system produce 22-32% higher average current compared to an intermittent charging (IC) mode, in which the capacitor was first charged from an MFC and then discharged to a resistor, at 21.6 Ω external resistance, 3.3 F capacitance and 300 mV charging voltage. The effects of external resistance, capacitance and charging voltage on average current were studied. The average current reduced as the external resistance and charging voltage increased and was slightly affected by the capacitance. Acquisition of higher average current in the ACD mode was attributed to the shorter discharging time compared to the charging time, as well as a higher anode potential caused by discharging the capacitor. Results from circuit analysis and quantitatively calculation were consistent with the experimental observations.

Oxidation of ammonium sulfite by a multi-needle-to-plate gas phase pulsed corona discharge reactor

NASA Astrophysics Data System (ADS)

Ren, Hua; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

2013-03-01

The oxidation of ammonium sulfite in the ammonia-based flue gas desulfurization (FGD) process was investigated in a multi-needle-to-plate gas phase pulsed corona discharge reactor in this paper. The effect of several parameters, including capacitance and peak pulse voltage of discharge system, electrode gap and bubbling gas flow rate on the oxidation rate of ammonium sulfite was reviewed. The oxidation rate of ammonium sulfite could reach 47.2% at the capacitance, the peak pulse voltage, electrode gap and bubbling gas flow rate equal to 2 nF, -24.6 k V, 35 mm and 4 L min-1 within treatment time of 40 min The experimental results indicate that the gas phase pulsed discharge system with a multi-needle-to-plate electrode can oxide the ammonium sulfite. The oxidation rate increased with the applied capacitance and peak pulse voltage and decreased with the electrode gap. As the bubbling gas flow rate increased, the oxidation rate increased first and then tended to reach a stationary value. These results would be important for the process optimization of the (NH4)2SO3 to (NH4)2SO4 oxidation.

CoNi2 S4 Nanoparticle/Carbon Nanotube Sponge Cathode with Ultrahigh Capacitance for Highly Compressible Asymmetric Supercapacitor.

PubMed

Cao, Xin; He, Jin; Li, Huan; Kang, Liping; He, Xuexia; Sun, Jie; Jiang, Ruibing; Xu, Hua; Lei, Zhibin; Liu, Zong-Huai

2018-05-30

Compared with other flexible energy-storage devices, the design and construction of the compressible energy-storage devices face more difficulty because they must accommodate large strain and shape deformations. In the present work, CoNi 2 S 4 nanoparticles/3D porous carbon nanotube (CNT) sponge cathode with highly compressible property and excellent capacitance is prepared by electrodepositing CoNi 2 S 4 on CNT sponge, in which CoNi 2 S 4 nanoparticles with size among 10-15 nm are uniformly anchored on CNT, causing the cathode to show a high compression property and gives high specific capacitance of 1530 F g -1 . Meanwhile, Fe 2 O 3 /CNT sponge anode with specific capacitance of 460 F g -1 in a prolonged voltage window is also prepared by electrodepositing Fe 2 O 3 nanosheets on CNT sponge. An asymmetric supercapacitor (CoNi 2 S 4 /CNT//Fe 2 O 3 /CNT) is assembled by using CoNi 2 S 4 /CNT sponge as positive electrode and Fe 2 O 3 /CNT sponge as negative electrode in 2 m KOH solution. It exhibits excellent energy density of up to 50 Wh kg -1 at a power density of 847 W kg -1 and excellent cycling stability at high compression. Even at a strain of 85%, about 75% of the initial capacitance is retained after 10 000 consecutive cycles. The CoNi 2 S 4 /CNT//Fe 2 O 3 /CNT device is a promising candidate for flexible energy devices due to its excellent compressibility and high energy density. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental Investigation of a Direct-drive Hall Thruster and Solar Array System at Power Levels up to 10 kW

NASA Technical Reports Server (NTRS)

Snyder, John S.; Brophy, John R.; Hofer, Richard R.; Goebel, Dan M.; Katz, Ira

2012-01-01

As NASA considers future exploration missions, high-power solar-electric propulsion (SEP) plays a prominent role in achieving many mission goals. Studies of high-power SEP systems (i.e. tens to hundreds of kilowatts) suggest that significant mass savings may be realized by implementing a direct-drive power system, so NASA recently established the National Direct-Drive Testbed to examine technical issues identified by previous investigations. The testbed includes a 12-kW solar array and power control station designed to power single and multiple Hall thrusters over a wide range of voltages and currents. In this paper, single Hall thruster operation directly from solar array output at discharge voltages of 200 to 450 V and discharge powers of 1 to 10 kW is reported. Hall thruster control and operation is shown to be simple and no different than for operation on conventional power supplies. Thruster and power system electrical oscillations were investigated over a large range of operating conditions and with different filter capacitances. Thruster oscillations were the same as for conventional power supplies, did not adversely affect solar array operation, and were independent of filter capacitance from 8 to 80 ?F. Solar array current and voltage oscillations were very small compared to their mean values and showed a modest dependence on capacitor size. No instabilities or anomalous behavior were observed in the thruster or power system at any operating condition investigated, including near and at the array peak power point. Thruster startup using the anode propellant flow as the power 'switch' was shown to be simple and reliable with system transients mitigated by the proper selection of filter capacitance size. Shutdown via cutoff of propellant flow was also demonstrated. A simple electrical circuit model was developed and is shown to have good agreement with the experimental data.

Benzocyclobutene-based electric micromachines supported on microball bearings: Design, fabrication, and characterization

NASA Astrophysics Data System (ADS)

Modafe, Alireza

This dissertation summarizes the research activities that led to the development of the first microball-bearing-supported linear electrostatic micromotor with benzocyclobutene (BCB) low-k polymer insulating layers. The primary application of this device is long-range, high-speed linear micropositioning. The future generations of this device include rotary electrostatic micromotors and microgenerators. The development of the first generation of microball-bearing-supported micromachines, including device theory, design, and modeling, material characterization, process development, device fabrication, and device test and characterization is presented. The first generation of these devices is based on a 6-phase, bottom-drive, linear, variable-capacitance micromotor (B-LVCM). The design of the electrical and mechanical components of the micromotor, lumped-circuit modeling of the device and electromechanical characteristics, including variable capacitance, force, power, and speed are presented. Electrical characterization of BCB polymers, characterization of BCB chemical mechanical planarization (CMP), development of embedded BCB in silicon (EBiS) process, and integration of device components using microfabrication techniques are also presented. The micromotor consists of a silicon stator, a silicon slider, and four stainless-steel microballs. The aligning force profile of the micromotor was extracted from simulated and measured capacitances of all phases. An average total aligning force of 0.27 mN with a maximum of 0.41 mN, assuming a 100 V peak-to-peak square-wave voltage, was measured. The operation of the micromotor was verified by applying square-wave voltages and characterizing the slider motion. An average slider speed of 7.32 mm/s when excited by a 40 Hz, 120 V square-wave voltage was reached without losing the synchronization. This research has a pivotal impact in the field of power microelectromechanical systems (MEMS). It establishes the foundation for the development of more reliable, efficient electrostatic micromachines with variety of applications such as micropropulsion, high-speed micropumping, microfluid delivery, and microsystem power generation.

Activated carbon derived from melaleuca barks for outstanding high-rate supercapacitors

NASA Astrophysics Data System (ADS)

Luo, Qiu-Ping; Huang, Liang; Gao, Xiang; Cheng, Yongliang; Yao, Bin; Hu, Zhimi; Wan, Jun; Xiao, Xu; Zhou, Jun

2015-07-01

Activated carbon (AC) was prepared via carbonizing melaleuca bark in an argon atmosphere at 600 °C followed with KOH activation for high-rate supercapacitors. This AC electrode has a high capacitance of 233 F g-1 at a scan rate of 2 mV s-1 and an excellent rate capability of ˜80% when increasing the sweep rate from 2 to 500 mV s-1. The symmetric supercapacitor assembled by the above electrode can deliver a high energy density of 4.2 Wh kg-1 with a power density of 1500 W kg-1 when operated in the voltage range of 0-1 V in 1 M H2SO4 aqueous electrolyte while maintaining great cycling stability (less than 5% capacitance loss after 10 000 cycles at sweep rate of 100 mV s-1). All the outstanding electrochemical performances make this AC electrode a promising candidate for potential energy storage application.

Parametric analysis of hollow conductor parallel and coaxial transmission lines for high frequency space power distribution

NASA Technical Reports Server (NTRS)

Jeffries, K. S.; Renz, D. D.

1984-01-01

A parametric analysis was performed of transmission cables for transmitting electrical power at high voltage (up to 1000 V) and high frequency (10 to 30 kHz) for high power (100 kW or more) space missions. Large diameter (5 to 30 mm) hollow conductors were considered in closely spaced coaxial configurations and in parallel lines. Formulas were derived to calculate inductance and resistance for these conductors. Curves of cable conductance, mass, inductance, capacitance, resistance, power loss, and temperature were plotted for various conductor diameters, conductor thickness, and alternating current frequencies. An example 5 mm diameter coaxial cable with 0.5 mm conductor thickness was calculated to transmit 100 kW at 1000 Vac, 50 m with a power loss of 1900 W, an inductance of 1.45 micron and a capacitance of 0.07 micron-F. The computer programs written for this analysis are listed in the appendix.

Voltage Drop in a Ferroelectric Single Layer Capacitor by Retarded Domain Nucleation.

PubMed

Kim, Yu Jin; Park, Hyeon Woo; Hyun, Seung Dam; Kim, Han Joon; Kim, Keum Do; Lee, Young Hwan; Moon, Taehwan; Lee, Yong Bin; Park, Min Hyuk; Hwang, Cheol Seong

2017-12-13

Ferroelectric (FE) capacitor is a critical electric component in microelectronic devices. Among many of its intriguing properties, the recent finding of voltage drop (V-drop) across the FE capacitor while the positive charges flow in is especially eye-catching. This finding was claimed to be direct evidence that the FE capacitor is in negative capacitance (NC) state, which must be useful for (infinitely) high capacitance and ultralow voltage operation of field-effect transistors. Nonetheless, the NC state corresponds to the maximum energy state of the FE material, so it has been widely accepted in the community that the material alleviates that state by forming ferroelectric domains. This work reports a similar V-drop effect from the 150 nm thick epitaxial BaTiO 3 ferroelectric thin film, but the interpretation was completely disparate; the V-drop can be precisely simulated by the reverse domain nucleation and propagation of which charge effect cannot be fully compensated for by the supplied charge from the external charge source. The disappearance of the V-drop effect was also observed by repeated FE switching only up to 10 cycles, which can hardly be explained by the involvement of the NC effect. The retained reverse domain nuclei even after the subsequent poling can explain such behavior.

Pulse switching for high energy lasers

NASA Technical Reports Server (NTRS)

Laudenslager, J. B.; Pacala, T. J. (Inventor)

1981-01-01

A saturable inductor switch for compressing the width and sharpening the rise time of high voltage pulses from a relatively slow rise time, high voltage generator to an electric discharge gas laser (EDGL) also provides a capability for efficient energy transfer from a high impedance primary source to an intermediate low impedance laser discharge network. The switch is positioned with respect to a capacitive storage device, such as a coaxial cable, so that when a charge build-up in the storage device reaches a predetermined level, saturation of the switch inductor releases or switches energy stored in the capactive storage device to the EDGL. Cascaded saturable inductor switches for providing output pulses having rise times of less than ten nanoseconds and a technique for magnetically biasing the saturable inductor switch are disclosed.

Solid State Clipper Diodes for High Power Modulators.

DTIC Science & Technology

1978-11-01

modeled at low powers and later confirmed in actua l P W pulsar operation. 0~ \\ ~~~~~~~~~ . ~~~~~ .. . .— - - I. ~~~~~ 3 J~ItV~ . \\ W \\_ UNC l ASSIFIE...and CG is the di ide api-i tance to 1avg — Ip ~ j- ground . In our design the worst case diode leakage (I 2( lO ~C) was 15 milliamperes (mA) at I kV...without it. I2rms 1p 2 ~~ ( 4) the diode junction capacitance and stray l’nns — 5 x lO ~ A 2 capacitance affect the voltage division whenever the

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babadi, A. S., E-mail: aein.shiri-babadi@eit.lth.se; Lind, E.; Wernersson, L. E.

A qualitative analysis on capacitance-voltage and conductance data for high-κ/InAs capacitors is presented. Our measured data were evaluated with a full equivalent circuit model, including both majority and minority carriers, as well as interface and border traps, formulated for narrow band gap metal-oxide-semiconductor capacitors. By careful determination of interface trap densities, distribution of border traps across the oxide thickness, and taking into account the bulk semiconductor response, it is shown that the trap response has a strong effect on the measured capacitances. Due to the narrow bandgap of InAs, there can be a large surface concentration of electrons and holesmore » even in depletion, so a full charge treatment is necessary.« less

Using the intrinsic properties of silicon micro-ring modulators for characterization of RF termination

NASA Astrophysics Data System (ADS)

Wang, Zhao; Knights, Andrew P.

2017-02-01

We describe a direct experimental method to determine the effective driving voltage (Vpp) applied to a silicon photonic modulator possessing an impedance mismatch between the unterminated capacitive load and input source. This method thus permits subsequent estimation of the power consumption of an imperfectly terminated device as well as a deduction of load impedance for optimization of termination design. The capacitive load in this paper is a silicon micro-ring modulator with an integrated p-n junction acting as a phase shifter. The RF reflection under high-speed drive is directly determined from observation of the eye-diagram following measurement of the power transfer function for various junction bias.

Characterisation of capacitively coupled HV/HR-CMOS sensor chips for the CLIC vertex detector

NASA Astrophysics Data System (ADS)

Kremastiotis, I.

2017-12-01

The capacitive coupling between an active sensor and a readout ASIC has been considered in the framework of the CLIC vertex detector study. The CLICpix Capacitively Coupled Pixel Detector (C3PD) is a High-Voltage CMOS sensor chip produced in a commercial 180 nm HV-CMOS process for this purpose. The sensor was designed to be connected to the CLICpix2 readout chip. It therefore matches the dimensions of the readout chip, featuring a matrix of 128×128 square pixels with 25μm pitch. The sensor chip has been produced with the standard value for the substrate resistivity (~20 Ωcm) and it has been characterised in standalone testing mode, before receiving and testing capacitively coupled assemblies. The standalone measurement results show a rise time of ~20 ns for a power consumption of 5μW/pixel. Production of the C3PD HV-CMOS sensor chip with higher substrate resistivity wafers (~20, 80, 200 and 1000 Ωcm) is foreseen. The expected benefits of the higher substrate resistivity will be studied using future assemblies with the readout chip.

A Contactless Capacitance Detection System for Microchip Capillary Electrophoresis

NASA Astrophysics Data System (ADS)

Wu, Peter

2008-05-01

The design, construction and operation of a simple, inexpensive and compact high voltage power supply for use in conjunction with a simple cross, capillary electrophoresis microchip is presented. The detection system utilizes a single high voltage power supply (15 kV), a voltage divider network for obtaining the required voltages for enabling a gated injection valve, and two high voltage relays for switching between the open and closed gate sequences of the injection. The system is used to determine sodium monofluoroacetate (MFA) concentration in diluted fruit juices and tap water. A separation buffer consisting of 20 mM citric acid and histidine at pH 3.5 enabled the detection of the anion in diluted apple juice, cranberry juice, and orange juice without lengthy sample pretreatments. Limit of detection in diluted juices and tap water were determined to be 125, 167, 138, and 173 mg/L for tap water, apple juice, cranberry juice, and orange juice, respectively, based upon an S/N of 3:1. The total analysis time for detecting the MFA anion in fruit juices was less than 5 min, which represents a considerable reduction in analysis time compared to other analytical methods currently used in food analysis.

Development of all-solid-state mediator-enhanced supercapacitors with polyvinylidene fluoride/lithium trifluoromethanesulfonate separators

NASA Astrophysics Data System (ADS)

Zhou, Juanjuan; Cai, Jinshu; Cai, Sirui; Zhou, Xiangyang; Mansour, Azzam N.

All-solid-state supercapacitors (SCs) were fabricated using a polyvinylidene fluoride (PVDF)/lithium trifluoromethanesulfonate (LiTFS) membrane as the separator and poly(ethylene oxide) (PEO)/lithium perchlorate (LiClO 4) as the polymer electrolyte in the porous carbon electrodes. Two types of mediators, NaI/I 2 and K 3Fe(CN) 6/K 4Fe(CN) 6, were added into the PEO/LiClO 4 polymer electrolyte that was used to fabricate the electrodes. The voltage window in which the SCs operated was 2.5-3 V. The results of electrochemical measurements, including cyclic voltammetry and galvanostatic charge/discharge, indicated that NaI/I 2-containing and K 3Fe(CN) 6/K 4Fe(CN) 6-containing SCs yielded high specific capacitances of 209.0 and 138.8 F g -1, respectively. In addition to high specific capacitances for the two mediator-containing SCs, both SCs delivered high specific energies (49.1 Wh kg -1 at 1.6 kW kg -1 for the NaI/I 2-containing SC and 33.6 Wh kg -1 at 1.3 kW kg -1 for the K 3Fe(CN) 6/K 4Fe(CN) 6-containing SC) due to the wide voltage window and fast redox reactions between mediators.

Control system of mobile radiographic complex to study equations of state of substances

NASA Astrophysics Data System (ADS)

Belov, O. V.; Valekzhanin, R. V.; Kustov, D. V.; Shamro, O. A.; Sharov, T. V.

2017-05-01

A source of x-ray radiation is one of the tools to study equations of state of substances in dynamics. The mobile radiographic bench based on BIM-1500 [1] was developed in RFNC-VNIIEF to increase output parameters of the x-ray radiation source. From automated control system side, BIM-1500 is a set of six high-voltage generators based on the capacitive energy storage, technological equipment, and elements of a blocking system. This paper considers automated control system of the mobile radiographic bench MCA BIM 1500. It consists of six high-voltage generator control circuits, synchronization subsystem, and block subsystem. The object of control has some peculiarities: high level of electromagnetic noise, remoteness of the control panel from the object of control. In connection with this, the coupling devices are arranged closer to the object of control and performed in the form of a set of galvanically insulated control units, which are combined into a net. The operator runs MCA BIM using the operator’s screens on PC or by means of manual control on the equipment in the mode of debugging. The control software provides performance of the experiment in automatic regime in accordance with preset settings. The operator can stop the experiment at the stage of charging the capacitive storage.

High-κ TiO{sub 2} thin film prepared by sol-gel spin-coating method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara, E-mail: ksrkrao@physics.iisc.ernet.in

2015-06-24

High-k TiO{sub 2} thin film on p-type silicon substrate was fabricated by a combined sol-gel and spin coating method. Thus deposited titania film had anatase phase with a small grain size of 16 nm and surface roughness of ≅ 0.6 nm. The oxide capacitance (C{sub ox}), flat band capacitance (C{sub FB}), flat band voltage (V{sub FB}), oxide trapped charge (Q{sub ot}), calculated from the high frequency (1 MHz) C-V curve were 0.47 nF, 0.16 nF, − 0.91 V, 4.7x10{sup −12} C, respectively. As compared to the previous reports, a high dielectric constant of 94 at 1 MHz frequency was observedmore » in the devices investigated here and an equivalent oxide thickness (EOT) was 4.1 nm. Dispersion in accumulation capacitance shows a linear relationship with AC frequencies. Leakage current density was found in acceptable limits (2.1e-5 A/cm{sup 2} for −1 V and 5.7e-7 A/cm{sup 2} for +1 V) for CMOS applications.« less

Aviation Maintenance Technology. General. G105 Aviation Electricity and Electronics. Instructor Material.

ERIC Educational Resources Information Center

Oklahoma State Board of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

These instructor materials for an aviation maintenance technology course contain five instructional modules. The modules cover the following topics: determining the relationship of voltage, current, resistance, and power in electrical circuits; computing and measuring capacitance and inductance; measuring voltage, current, resistance, and…

A system for measuring thermal activation energy levels in silicon by thermally stimulated capacitance

NASA Technical Reports Server (NTRS)

Cockrum, R. H.

1982-01-01

One method being used to determine energy level(s) and electrical activity of impurities in silicon is described. The method is called capacitance transient spectroscopy (CTS). It can be classified into three basic categories: the thermally stimulated capacitance method, the voltage-stimulated capacitance method, and the light-stimulated capacitance method; the first two categories are discussed. From the total change in capacitance and the time constant of the capacitance response, emission rates, energy levels, and trap concentrations can be determined. A major advantage of using CTS is its ability to detect the presence of electrically active impurities that are invisible to other techniques, such as Zeeman effect atomic absorption, and the ability to detect more than one electrically active impurity in a sample. Examples of detection of majority and minority carrier traps from gold donor and acceptor centers in silicon using the capacitance transient spectrometer are given to illustrate the method and its sensitivity.

High breakdown voltage and high driving current in a novel silicon-on-insulator MESFET with high- and low-resistance boxes in the drift region

NASA Astrophysics Data System (ADS)

Naderi, Ali; Mohammadi, Hamed

2018-06-01

In this paper a novel silicon-on-insulator metal oxide field effect transistor (SOI-MESFET) with high- and low-resistance boxes (HLRB) is proposed. This structure increases the current and breakdown voltage, simultaneously. The semiconductor at the source side of the channel is doped with higher impurity than the other parts to reduce its resistance and increase the driving current as low-resistance box. An oxide box is implemented at the upper part of the channel from the drain region toward the middle of the channel as the high-resistance box. Inserting a high-resistance box increases the breakdown voltage and improves the RF performance of the device because of its higher tolerable electric field and modification in gate-drain capacitance, respectively. The high-resistance region reduces the current density of the device which is completely compensated by low-resistance box. A 92% increase in breakdown voltage and an 11% improvement in the device current have been obtained. Also, maximum oscillation frequency, unilateral power gain, maximum available gain, maximum stable gain, and maximum output power density are improved by 7%, 35%, 23%, 26%, and 150%, respectively. These results show that the HLRB-SOI-MESFET can be considered as a candidate to replace Conventional SOI-MESFET (C-SOI-MESFET) for high-voltage and high-frequency applications.

Characterization of the inhomogeneous barrier distribution in a Pt/(100)β-Ga2O3 Schottky diode via its temperature-dependent electrical properties

NASA Astrophysics Data System (ADS)

Jian, Guangzhong; He, Qiming; Mu, Wenxiang; Fu, Bo; Dong, Hang; Qin, Yuan; Zhang, Ying; Xue, Huiwen; Long, Shibing; Jia, Zhitai; Lv, Hangbing; Liu, Qi; Tao, Xutang; Liu, Ming

2018-01-01

β-Ga2O3 is an ultra-wide bandgap semiconductor with applications in power electronic devices. Revealing the transport characteristics of β-Ga2O3 devices at various temperatures is important for improving device performance and reliability. In this study, we fabricated a Pt/β-Ga2O3 Schottky barrier diode with good performance characteristics, such as a low ON-resistance, high forward current, and a large rectification ratio. Its temperature-dependent current-voltage and capacitance-voltage characteristics were measured at various temperatures. The characteristic diode parameters were derived using thermionic emission theory. The ideality factor n was found to decrease from 2.57 to 1.16 while the zero-bias barrier height Φb0 increased from 0.47 V to 1.00 V when the temperature was increased from 125 K to 350 K. This was explained by the Gaussian distribution of barrier height inhomogeneity. The mean barrier height Φ ¯ b0 = 1.27 V and zero-bias standard deviation σ0 = 0.13 V were obtained. A modified Richardson plot gave a Richardson constant A* of 36.02 A.cm-2.K-2, which is close to the theoretical value of 41.11 A.cm-2.K-2. The differences between the barrier heights determined using the capacitance-voltage and current-voltage curves were also in line with the Gaussian distribution of barrier height inhomogeneity.

Miniaturized two-stack Blumlein pulser with a variable repetition-rate for non-thermal irreversible-electroporation experiments

NASA Astrophysics Data System (ADS)

Min, Sun-Hong; Kwon, Ohjoon; Sattorov, Matlabjon; Baek, In-Keun; Kim, Seontae; Jeong, Jin-Young; Hong, Dongpyo; Park, Seunghyuk; Park, Gun-Sik

2017-01-01

Non-thermal irreversible electroporation (NTIRE) to avoid thermal damage to cells during intense DC ns pulsed electric fields (nsPEFs) is a recent modality for medical applications. This mechanism, related to bioelectrical dynamics of the cell, is linked to the effect of a DC electric field and a threshold effect with an electrically stimulated membrane for the charge distribution in the cell. To create the NTIRE condition, the pulse width of the nsPEF should be shorter than the charging time constant of the membrane related to the cell radius, membrane capacitance, cytoplasm resistivity, and medium resistivity. It is necessary to design and fabricate a very intense nanosecond DC electric field pulser that is capable of producing voltages up to the level of 100 kV/cm with an artificial pulse width (˜ns) with controllable repetition rates. Many devices to generate intense DC nsPEF using various pulse-forming line technologies have been introduced thus far. However, the previous Blumlein pulse-generating devices are clearly inefficient due to the energy loss between the input voltage and the output voltage. An improved two-stage stacked Blumlein pulse-forming line can overcome this limitation and decrease the energy loss from a DC power supply. A metal oxide silicon field-effect transistor switch with a fast rise and fall time would enable a high repetition rate (max. 100 kHz) and good endurance against very high voltages (DC ˜ 30 kV). The load is designed to match the sample for exposure to cell suspensions consisting of a 200 Ω resistor matched with a Blumlein circuit and two electrodes without the characteristic RC time effect of the circuit (capacitance =0.174 pF).

Tunable dielectric properties of TiO2 thin film based MOS systems for application in microelectronics

NASA Astrophysics Data System (ADS)

Gyanan; Mondal, Sandip; Kumar, Arvind

2016-12-01

Post-deposition annealing (PDA) is an inherent part of a sol-gel fabrication process to achieve the optimum device performance, especially in CMOS applications. Annealing removes the oxygen vacancies and improves the structural order of the dielectric films. The process also reduces the interface related defects and improves the interfacial properties. Here, we applied a sol-gel spin-coating technique to prepare high-k TiO2 films on the p-Si substrate. These films were fired at 400 °C for the duration of 20, 40, 60 and 80 min to know the effects of annealing time on the device characteristics. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of annealed TiO2 films were examined in Al/TiO2/p-Si device configuration at room temperature. The 60 min annealed film gives the optimum performance and contained 69.5% anatase and 39.5% rutile phase with refractive index 2.40 at 550 nm. The C-V and I-V characteristic showed a significant dependence on annealing time such as variation in dielectric constant and leakage current. This allows us to tune the various electrical properties of MOS systems. The accumulation capacitance (Cox), dielectric constant (κ) and the equivalent oxide thickness (EOT) of the film fired for 60 min were found to be 458 pF, 33, and 4.25 nm, respectively with a low leakage current density (3.13 × 10-7 A/cm2) fired for 80 min at -1 V. The current conduction mechanisms at high bias voltage were dominated by trap-charge limited current (TCLC), while at small voltages, space charge limited current (SCLC) was more prominent.

A Comparative Analysis of CMUT Receiving Architectures for the Design Optimization of Integrated Transceiver Front Ends.

PubMed

Sautto, Marco; Savoia, Alessandro Stuart; Quaglia, Fabio; Caliano, Giosue; Mazzanti, Andrea

2017-05-01

A formal comparison between fundamental RX amplifier configurations for capacitive micromachined ultrasonic transducers (CMUTs) is proposed in this paper. The impact on both RX and the pulse-echo frequency response and on the output SNR is thoroughly analyzed and discussed. It is shown that the resistive-feedback amplifier yields a bandpass RX frequency response, while both open-loop voltage and capacitive-feedback amplifiers exhibit a low-pass frequency response. For a given power dissipation, it is formally proved that a capacitive-feedback amplifier provides a remarkable SNR improvement against the commonly adopted resistive feedback stage, achieved at the expense of a reduced pulse-echo center frequency, making its use convenient in low-frequency and midfrequency ultrasound imaging applications. The advantage mostly comes from a much lower noise contributed by the active devices, especially with low- Q , broadband transducers. The results of the analysis are applied to the design of a CMUT front end in BIPOLAR-CMOS-DMOS Silicon-on-Insulator technology operating at 10-MHz center frequency. It comprises a low-power RX amplifier, a high-voltage Transmission/Reception switch, and a 100-V TX driver. Extensive electrical characterization, pulse-echo measurements, and imaging results are shown. Compared with previously reported CMUT front ends, this transceiver demonstrates the highest dynamic range and state-of-the-art noise performance with an RX amplifier power dissipation of 1 mW.

Multifunctional Hybrid Multilayer Gate Dielectrics with Tunable Surface Energy for Ultralow-Power Organic and Amorphous Oxide Thin-Film Transistors.

PubMed

Byun, Hye-Ran; You, Eun-Ah; Ha, Young-Geun

2017-03-01

For large-area, printable, and flexible electronic applications using advanced semiconductors, novel dielectric materials with excellent capacitance, insulating property, thermal stability, and mechanical flexibility need to be developed to achieve high-performance, ultralow-voltage operation of thin-film transistors (TFTs). In this work, we first report on the facile fabrication of multifunctional hybrid multilayer gate dielectrics with tunable surface energy via a low-temperature solution-process to produce ultralow-voltage organic and amorphous oxide TFTs. The hybrid multilayer dielectric materials are constructed by iteratively stacking bifunctional phosphonic acid-based self-assembled monolayers combined with ultrathin high-k oxide layers. The nanoscopic thickness-controllable hybrid dielectrics exhibit the superior capacitance (up to 970 nF/cm 2 ), insulating property (leakage current densities <10 -7 A/cm 2 ), and thermal stability (up to 300 °C) as well as smooth surfaces (root-mean-square roughness <0.35 nm). In addition, the surface energy of the hybrid multilayer dielectrics are easily changed by switching between mono- and bifunctional phosphonic acid-based self-assembled monolayers for compatible fabrication with both organic and amorphous oxide semiconductors. Consequently, the hybrid multilayer dielectrics integrated into TFTs reveal their excellent dielectric functions to achieve high-performance, ultralow-voltage operation (< ± 2 V) for both organic and amorphous oxide TFTs. Because of the easily tunable surface energy, the multifunctional hybrid multilayer dielectrics can also be adapted for various organic and inorganic semiconductors, and metal gates in other device configurations, thus allowing diverse advanced electronic applications including ultralow-power and large-area electronic devices.

Low-voltage operation of Si-based ferroelectric field effect transistors using organic ferroelectrics, poly(vinylidene fluoride-trifluoroethylene), as a gate dielectric

NASA Astrophysics Data System (ADS)

Miyata, Yusuke; Yoshimura, Takeshi; Ashida, Atsushi; Fujimura, Norifumi

2016-04-01

Si-based metal-ferroelectric-semiconductor (MFS) capacitors have been fabricated using poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] as a ferroelectric gate. The pinhole-free P(VDF-TrFE) thin films with high resistivity were able to be prepared by spin-coating directly onto hydrogen-terminated Si. The capacitance-voltage (C-V) characteristics of the ferroelectric gate field effect transistor (FeFET) using this MFS structure clearly show butterfly-shaped hysteresis originating from the ferroelectricity, indicating carrier modulation on the Si surface at gate voltages below 2 V. The drain current-gate voltage (I D-V G) characteristics also show counterclockwise hysteresis at gate voltages below 5 V. This is the first report on the low-voltage operation of a Si-based FeFET using P(VDF-TrFE) as a gate dielectric. This organic gate FeFET without any insulator layer at the ferroelectric/Si interface should be one of the promising devices for overcoming the critical issues of the FeFET, such as depolarization field and a decrease in the gate voltage.

Experiments with a Varicap

ERIC Educational Resources Information Center

Kraftmakher, Yaakov

2011-01-01

The capacitance versus voltage relationship (the "C-V" characteristic) of a varicap is determined, and the device is used for tuning an "LC" circuit and for building a voltage-controlled oscillator. With a data-acquisition system, the "C-V" characteristic can be demonstrated in a short time. The necessary equipment includes a function generator,…

ELECTRICAL CIRCUITS USING COLD-CATHODE TRIODE VALVES

DOEpatents

Goulding, F.S.

1957-11-26

An electrical circuit which may be utilized as a pulse generator or voltage stabilizer is presented. The circuit employs a cold-cathode triode valve arranged to oscillate between its on and off stages by the use of selected resistance-capacitance time constant components in the plate and trigger grid circuits. The magnitude of the d-c voltage applied to the trigger grid circuit effectively controls the repetition rate of the output pulses. In the voltage stabilizer arrangement the d-c control voltage is a portion of the supply voltage and the rectified output voltage is substantially constant.

Ferroelectric thin-film capacitors and piezoelectric switches for mobile communication applications.

PubMed

Klee, Mareike; van Esch, Harry; Keur, Wilco; Kumar, Biju; van Leuken-Peters, Linda; Liu, Jin; Mauczok, Rüdiger; Neumann, Kai; Reimann, Klaus; Renders, Christel; Roest, Aarnoud L; Tiggelman, Mark P J; de Wild, Marco; Wunnicke, Olaf; Zhao, Jing

2009-08-01

Thin-film ferroelectric capacitors have been integrated with resistors and active functions such as ESD protection into small, miniaturized modules, which enable a board space saving of up to 80%. With the optimum materials and processes, integrated capacitors with capacitance densities of up to 100 nF/mm2 for stacked capacitors combined with breakdown voltages of 90 V have been achieved. The integration of these high-density capacitors with extremely high breakdown voltage is a major accomplishment in the world of passive components and has not yet been reported for any other passive integration technology. Furthermore, thin-film tunable capacitors based on barium strontium titanate with high tuning range and high quality factor at 1 GHz have been demonstrated. Finally, piezoelectric thin films for piezoelectric switches with high switching speed have been realized.

Space station power semiconductor package

NASA Technical Reports Server (NTRS)

Balodis, Vilnis; Berman, Albert; Devance, Darrell; Ludlow, Gerry; Wagner, Lee

1987-01-01

A package of high-power switching semiconductors for the space station have been designed and fabricated. The package includes a high-voltage (600 volts) high current (50 amps) NPN Fast Switching Power Transistor and a high-voltage (1200 volts), high-current (50 amps) Fast Recovery Diode. The package features an isolated collector for the transistors and an isolated anode for the diode. Beryllia is used as the isolation material resulting in a thermal resistance for both devices of .2 degrees per watt. Additional features include a hermetical seal for long life -- greater than 10 years in a space environment. Also, the package design resulted in a low electrical energy loss with the reduction of eddy currents, stray inductances, circuit inductance, and capacitance. The required package design and device parameters have been achieved. Test results for the transistor and diode utilizing the space station package is given.

Electrical hysteresis in p-GaN metal-oxide-semiconductor capacitor with atomic-layer-deposited Al2O3 as gate dielectric

NASA Astrophysics Data System (ADS)

Zhang, Kexiong; Liao, Meiyong; Imura, Masataka; Nabatame, Toshihide; Ohi, Akihiko; Sumiya, Masatomo; Koide, Yasuo; Sang, Liwen

2016-12-01

The electrical hysteresis in current-voltage (I-V) and capacitance-voltage characteristics was observed in an atomic-layer-deposited Al2O3/p-GaN metal-oxide-semiconductor capacitor (PMOSCAP). The absolute minimum leakage currents of the PMOSCAP for forward and backward I-V scans occurred not at 0 V but at -4.4 and +4.4 V, respectively. A negative flat-band voltage shift of 5.5 V was acquired with a capacitance step from +4.4 to +6.1 V during the forward scan. Mg surface accumulation on p-GaN was demonstrated to induce an Mg-Ga-Al-O oxidized layer with a trap density on the order of 1013 cm-2. The electrical hysteresis is attributed to the hole trapping and detrapping process in the traps of the Mg-Ga-Al-O layer via the Poole-Frenkel mechanism.

Construction of high-capacitance 3D CoO@polypyrrole nanowire array electrode for aqueous asymmetric supercapacitor.

PubMed

Zhou, Cheng; Zhang, Yangwei; Li, Yuanyuan; Liu, Jinping

2013-05-08

We have developed a supercapacitor electrode composed of well-aligned CoO nanowire array grown on 3D nickel foam with polypyrrole (PPy) uniformly immobilized onto or firmly anchored to each nanowire surface to boost the pseudocapacitive performance. The electrode architecture takes advantage of the high electrochemical activity from both the CoO and PPy, the high electronic conductivity of PPy, and the short ion diffusion pathway in ordered mesoporous nanowires. These merits together with the elegant synergy between CoO and PPy lead to a high specific capacitance of 2223 F g(-1) approaching the theoretical value, good rate capability, and cycling stability (99.8% capacitance retention after 2000 cycles). An aqueous asymmetric supercapacitor device with a maximum voltage of 1.8 V fabricated by using our hybrid array as the positive electrode and activated carbon film as the negative electrode has demonstrated high energy density (~43.5 Wh kg(-1)), high power density (~5500 W kg(-1) at 11.8 Wh kg(-1)) and outstanding cycleability (~20,000 times). After charging for only ~10 s, two such 4 cm(2) asymmetric supercapacitors connected in series can efficiently power 5 mm diameter red, yellow, and green round LED indicators (lasting for 1 h for red LED) and drive a mini 130 rotation-motor robustly.

High energy density asymmetric supercapacitors with a nickel oxide nanoflake cathode and a 3D reduced graphene oxide anode

NASA Astrophysics Data System (ADS)

Luan, Feng; Wang, Gongming; Ling, Yichuan; Lu, Xihong; Wang, Hanyu; Tong, Yexiang; Liu, Xiao-Xia; Li, Yat

2013-08-01

Here we demonstrate a high energy density asymmetric supercapacitor with nickel oxide nanoflake arrays as the cathode and reduced graphene oxide as the anode. Nickel oxide nanoflake arrays were synthesized on a flexible carbon cloth substrate using a seed-mediated hydrothermal method. The reduced graphene oxide sheets were deposited on three-dimensional (3D) nickel foam by hydrothermal treatment of nickel foam in graphene oxide solution. The nanostructured electrodes provide a large effective surface area. The asymmetric supercapacitor device operates with a voltage of 1.7 V and achieved a remarkable areal capacitance of 248 mF cm-2 (specific capacitance of 50 F g-1) at a charge/discharge current density of 1 mA cm-2 and a maximum energy density of 39.9 W h kg-1 (based on the total mass of active materials of 5.0 mg). Furthermore, the device showed an excellent charge/discharge cycling performance in 1.0 M KOH electrolyte at a current density of 5 mA cm-2, with a capacitance retention of 95% after 3000 cycles.

Capacitance and conductance-frequency characteristics of In-pSi Schottky barrier diode

NASA Astrophysics Data System (ADS)

Dhimmar, J. M.; Desai, H. N.; Modi, B. P.

2015-06-01

The Schottky barrier height (SBH) values have been calculated by using the reverse bias capacitance-voltage (C-V) characteristics at temperature range of 120-360K. The forward bias capacitance-frequency (C-f) and conductance- frequency (G-f) measurement of In-pSi SBD have been carried out from 0-1.0 V with a step up 0.05 V whereby the energy distribution of the interface state has been determined from the forward bias I-V data taking the bias dependence of the effective barrier height and series resistance (RS) into account. The high value of ideality factor (n=2.12) was attributing to high density of interface states and interfacial oxide layer at metal semiconductor interface. The interface state density (NSS) shows a decrease with bias from bottom of conduction band toward the mid gap. In order to examine frequency dependence NSS, RS, C-V and G(ω)/ω-f measurement of the diode were performed at room temperature in the frequency range of 100Hz-100KHz. Experimental result confirmed that there is an influence in the electrical characteristic of Schottky diode.

High energy density asymmetric supercapacitors with a nickel oxide nanoflake cathode and a 3D reduced graphene oxide anode.

PubMed

Luan, Feng; Wang, Gongming; Ling, Yichuan; Lu, Xihong; Wang, Hanyu; Tong, Yexiang; Liu, Xiao-Xia; Li, Yat

2013-09-07

Here we demonstrate a high energy density asymmetric supercapacitor with nickel oxide nanoflake arrays as the cathode and reduced graphene oxide as the anode. Nickel oxide nanoflake arrays were synthesized on a flexible carbon cloth substrate using a seed-mediated hydrothermal method. The reduced graphene oxide sheets were deposited on three-dimensional (3D) nickel foam by hydrothermal treatment of nickel foam in graphene oxide solution. The nanostructured electrodes provide a large effective surface area. The asymmetric supercapacitor device operates with a voltage of 1.7 V and achieved a remarkable areal capacitance of 248 mF cm(-2) (specific capacitance of 50 F g(-1)) at a charge/discharge current density of 1 mA cm(-2) and a maximum energy density of 39.9 W h kg(-1) (based on the total mass of active materials of 5.0 mg). Furthermore, the device showed an excellent charge/discharge cycling performance in 1.0 M KOH electrolyte at a current density of 5 mA cm(-2), with a capacitance retention of 95% after 3000 cycles.

Study of surface properties of ATLAS12 strip sensors and their radiation resistance

NASA Astrophysics Data System (ADS)

Mikestikova, M.; Allport, P. P.; Baca, M.; Broughton, J.; Chisholm, A.; Nikolopoulos, K.; Pyatt, S.; Thomas, J. P.; Wilson, J. A.; Kierstead, J.; Kuczewski, P.; Lynn, D.; Hommels, L. B. A.; Ullan, M.; Bloch, I.; Gregor, I. M.; Tackmann, K.; Hauser, M.; Jakobs, K.; Kuehn, S.; Mahboubi, K.; Mori, R.; Parzefall, U.; Clark, A.; Ferrere, D.; Sevilla, S. Gonzalez; Ashby, J.; Blue, A.; Bates, R.; Buttar, C.; Doherty, F.; McMullen, T.; McEwan, F.; O'Shea, V.; Kamada, S.; Yamamura, K.; Ikegami, Y.; Nakamura, K.; Takubo, Y.; Unno, Y.; Takashima, R.; Chilingarov, A.; Fox, H.; Affolder, A. A.; Casse, G.; Dervan, P.; Forshaw, D.; Greenall, A.; Wonsak, S.; Wormald, M.; Cindro, V.; Kramberger, G.; Mandić, I.; Mikuž, M.; Gorelov, I.; Hoeferkamp, M.; Palni, P.; Seidel, S.; Taylor, A.; Toms, K.; Wang, R.; Hessey, N. P.; Valencic, N.; Hanagaki, K.; Dolezal, Z.; Kodys, P.; Bohm, J.; Stastny, J.; Bevan, A.; Beck, G.; Milke, C.; Domingo, M.; Fadeyev, V.; Galloway, Z.; Hibbard-Lubow, D.; Liang, Z.; Sadrozinski, H. F.-W.; Seiden, A.; To, K.; French, R.; Hodgson, P.; Marin-Reyes, H.; Parker, K.; Jinnouchi, O.; Hara, K.; Sato, K.; Hagihara, M.; Iwabuchi, S.; Bernabeu, J.; Civera, J. V.; Garcia, C.; Lacasta, C.; Marti i Garcia, S.; Rodriguez, D.; Santoyo, D.; Solaz, C.; Soldevila, U.

2016-09-01

A radiation hard n+-in-p micro-strip sensor for the use in the Upgrade of the strip tracker of the ATLAS experiment at the High Luminosity Large Hadron Collider (HL-LHC) has been developed by the "ATLAS ITk Strip Sensor collaboration" and produced by Hamamatsu Photonics. Surface properties of different types of end-cap and barrel miniature sensors of the latest sensor design ATLAS12 have been studied before and after irradiation. The tested barrel sensors vary in "punch-through protection" (PTP) structure, and the end-cap sensors, whose stereo-strips differ in fan geometry, in strip pitch and in edge strip ganging options. Sensors have been irradiated with proton fluences of up to 1×1016 neq/cm2, by reactor neutron fluence of 1×1015 neq/cm2 and by gamma rays from 60Co up to dose of 1 MGy. The main goal of the present study is to characterize the leakage current for micro-discharge breakdown voltage estimation, the inter-strip resistance and capacitance, the bias resistance and the effectiveness of PTP structures as a function of bias voltage and fluence. It has been verified that the ATLAS12 sensors have high breakdown voltage well above the operational voltage which implies that different geometries of sensors do not influence their stability. The inter-strip isolation is a strong function of irradiation fluence, however the sensor performance is acceptable in the expected range for HL-LHC. New gated PTP structure exhibits low PTP onset voltage and sharp cut-off of effective resistance even at the highest tested radiation fluence. The inter-strip capacitance complies with the technical specification required before irradiation and no radiation-induced degradation was observed. A summary of ATLAS12 sensors tests is presented including a comparison of results from different irradiation sites. The measured characteristics are compared with the previous prototype of the sensor design, ATLAS07.

A rugged 650 V SOI-based high-voltage half-bridge IGBT gate driver IC for motor drive applications

NASA Astrophysics Data System (ADS)

Hua, Qing; Li, Zehong; Zhang, Bo; Chen, Weizhong; Huang, Xiangjun; Feng, Yuxiang

2015-05-01

This paper proposes a rugged high-voltage N-channel insulated gate bipolar transistor (IGBT) gate driver integrated circuit. The device integrates a high-side and a low-side output stages on a single chip, which is designed specifically for motor drive applications. High-voltage level shift technology enables the high-side stage of this device to operate up to 650 V. The logic inputs are complementary metal oxide semiconductor (CMOS)/transistor transistor logic compatible down to 3.3 V. Undervoltage protection functionality with hysteresis characteristic has also been integrated to enhance the device reliability. The device is fabricated in a 1.0 μm, 650 V high-voltage bipolar CMOS double-diffused metal oxide semiconductor (BCD) on silicon-on-insulator (SOI) process. Deep trench dielectric isolation technology is employed to provide complete electrical isolation with advantages such as reduced parasitic effects, excellent noise immunity and low leakage current. Experimental results show that the isolation voltage of this device can be up to approximately 779 V at 25°C, and the leakage current is only 5 nA at 650 V, which is 15% higher and 67% lower than the conventional ones. In addition, it delivers an excellent thermal stability and needs very low quiescent current and offers a high gate driver capability which is needed to adequately drive IGBTs that have large input capacitances.

Characterization of Tantalum Polymer Capacitors

NASA Technical Reports Server (NTRS)

Spence, Penelope

2012-01-01

Overview Reviewed data Caution must be taken when accelerating test conditions Data not useful to establish an acceleration model Introduction of new failure mechanism skewing results Evidence of Anti-Wear-Out De-doping of polymer Decreased capacitance Increased ESR Not dielectric breakdown Needs further investigation Further investigation into tantalum polymer capacitor technology Promising acceleration model for Manufacturer A Possibility for use in high-reliability space applications with suitable voltage derating.

Enhanced Passive RF-DC Converter Circuit Efficiency for Low RF Energy Harvesting

PubMed Central

Chaour, Issam; Fakhfakh, Ahmed; Kanoun, Olfa

2017-01-01

For radio frequency energy transmission, the conversion efficiency of the receiver is decisive not only for reducing sending power, but also for enabling energy transmission over long and variable distances. In this contribution, we present a passive RF-DC converter for energy harvesting at ultra-low input power at 868 MHz. The novel converter consists of a reactive matching circuit and a combined voltage multiplier and rectifier. The stored energy in the input inductor and capacitance, during the negative wave, is conveyed to the output capacitance during the positive one. Although Dickson and Villard topologies have principally comparable efficiency for multi-stage voltage multipliers, the Dickson topology reaches a better efficiency within the novel ultra-low input power converter concept. At the output stage, a low-pass filter is introduced to reduce ripple at high frequencies in order to realize a stable DC signal. The proposed rectifier enables harvesting energy at even a low input power from −40 dBm for a resistive load of 50 kΩ. It realizes a significant improvement in comparison with state of the art solutions. PMID:28282910

A wide-range 22-GHz LC-based CMOS voltage-controlled oscillator

NASA Astrophysics Data System (ADS)

Gharbieh, Karam; Ranneh, Mohammed; Abugharbieh, Khaldoon

2018-06-01

This work presents a novel voltage-controlled oscillator (VCO) design and simulations that combine a varactor bank with a transformer in the LC tank to achieve a high-frequency range. While the varactor bank is responsible for changing the capacitance in the LC tank, the transformer acts as a means to change the value of the inductance, hence allowing tune-ability in the two main components of the VCO. A control mechanism utilises a mixed-mode circuit consisting of comparators and a state machine. It allows efficient tuning of the VCO by controlling the capacitance and transformer in the LC tank. The VCO has a 10.75-22.43 GHz frequency range and the VCO gain, KVCO, is kept at a low value ranging from 98.6 to 175.7 MHz/V. The simulated phase noise is -111 dBc/Hz at 1 MHz offset from the 10.75 GHz oscillation frequency. The circuit is designed and simulated in 28 nm CMOS technology and uses a 1 V supply drawing a typical power of 14.74 mW.

Atomic-layer-deposited Al2O3-HfO2-Al2O3 dielectrics for metal-insulator-metal capacitor applications

NASA Astrophysics Data System (ADS)

Ding, Shi-Jin; Zhu, Chunxiang; Li, Ming-Fu; Zhang, David Wei

2005-08-01

Atomic-layer-deposited Al2O3-HfO2-Al2O3 dielectrics have been investigated to replace conventional silicon oxide and nitride for radio frequency and analog metal-insulator-metal capacitors applications. In the case of 1-nm-Al2O3, sufficiently good electrical performances are achieved, including a high dielectric constant of ˜17, a small dissipation factor of 0.018 at 100kHz, an extremely low leakage current of 7.8×10-9A/cm2 at 1MV/cm and 125°C, perfect voltage coefficients of capacitance (74ppm/V2 and 10ppm/V). The quadratic voltage coefficient of capacitance decreases with the applied frequency due to the change of relaxation time with different carrier mobility in insulator, and correlates with the dielectric composition and thickness, which is of intrinsic property owing to electric field polarization. Furthermore, the conduction mechanism of the AHA dielectrics is also discussed, indicating the Schottky emission dominated at room temperature.

Enhanced Passive RF-DC Converter Circuit Efficiency for Low RF Energy Harvesting.

PubMed

Chaour, Issam; Fakhfakh, Ahmed; Kanoun, Olfa

2017-03-09

For radio frequency energy transmission, the conversion efficiency of the receiver is decisive not only for reducing sending power, but also for enabling energy transmission over long and variable distances. In this contribution, we present a passive RF-DC converter for energy harvesting at ultra-low input power at 868 MHz. The novel converter consists of a reactive matching circuit and a combined voltage multiplier and rectifier. The stored energy in the input inductor and capacitance, during the negative wave, is conveyed to the output capacitance during the positive one. Although Dickson and Villard topologies have principally comparable efficiency for multi-stage voltage multipliers, the Dickson topology reaches a better efficiency within the novel ultra-low input power converter concept. At the output stage, a low-pass filter is introduced to reduce ripple at high frequencies in order to realize a stable DC signal. The proposed rectifier enables harvesting energy at even a low input power from -40 dBm for a resistive load of 50 kΩ. It realizes a significant improvement in comparison with state of the art solutions.

Photoluminescence and capacitance voltage characterization of GaAs surface passivated by an ultrathin GaN interface control layer

NASA Astrophysics Data System (ADS)

Anantathanasarn, Sanguan; Hasegawa, Hideki

2002-05-01

A novel surface passivation technique for GaAs using an ultrathin GaN interface control layer (GaN ICL) formed by surface nitridation was characterized by ultrahigh vacuum (UHV) photoluminescence (PL) and capacitance-voltage ( C- V) measurements. The PL quantum efficiency was dramatically enhanced after being passivated by the GaN ICL structure, reaching as high as 30 times of the initial clean GaAs surface. Further analysis of PL data was done by the PL surface state spectroscopy (PLS 3) simulation technique. PL and C- V results are in good agreement indicating that ultrathin GaN ICL reduces the gap states and unpins the Fermi level, realizing a wide movement of Fermi level within the midgap region and reduction of the effective surface recombination velocity by a factor of 1/60. GaN layer also introduced a large negative surface fixed charge of about 10 12 cm -2. A further improvement took place by depositing a Si 3N 4 layer on GaN ICL/GaAs structure.

Slope and amplitude asymmetry effects on low frequency capacitively coupled carbon tetrafluoride plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruneau, B., E-mail: bastien.bruneau@polytechnique.edu; Johnson, E.; Korolov, I.

2016-04-28

We report investigations of capacitively coupled carbon tetrafluoride (CF{sub 4}) plasmas excited with tailored voltage waveforms containing up to five harmonics of a base frequency of 5.5 MHz. The impact of both the slope asymmetry, and the amplitude asymmetry, of these waveforms on the discharge is examined by combining experiments with particle-in-cell simulations. For all conditions studied herein, the discharge is shown to operate in the drift-ambipolar mode, where a comparatively large electric field in the plasma bulk (outside the sheaths) is the main mechanism for electron power absorption leading to ionization. We show that both types of waveform asymmetries stronglymore » influence the ion energy at the electrodes, with the particularity of having the highest ion flux on the electrode where the lowest ion energy is observed. Even at the comparatively high pressure (600 mTorr) and low fundamental frequency of 5.5 MHz used here, tailoring the voltage waveforms is shown to efficiently create an asymmetry of both the ion energy and the ion flux in geometrically symmetric reactors.« less

Effect of gas properties on the dynamics of the electrical slope asymmetry effect in capacitive plasmas: comparison of Ar, H 2 and CF 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruneau, Bastien; Lafleur, T.; Gans, T.

2015-12-01

Tailored voltage excitation waveforms provide an efficient control of the ion energy (through the electrical asymmetry effect) in capacitive plasmas by varying the 'amplitude' asymmetry of the waveform. In this work, the effect of a 'slope' asymmetry of the waveform is investigated by using sawtooth-like waveforms, through which the sheath dynamic can be manipulated. A remarkably different discharge dynamic is found for Ar, H 2, and CF 4 gases, which is explained by the different dominant electron heating mechanisms and plasma chemistries. In comparison to Argon we find that the electrical asymmetry can even be reversed by using an electronegativemore » gas such as CF 4. Phase resolved optical emission spectroscopy measurements, probing the spatiotemporal distribution of the excitation rate show excellent agreement with the results of particle-in-cell simulations, confirming the high degree of correlation between the excitation rates with the dominant heating mechanisms in the various gases. It is shown that, depending on the gas used, sawtooth-like voltage waveforms may cause a strong asymmetry.« less

An evaluation method of the profile of plasma-induced defects based on capacitance-voltage measurement

NASA Astrophysics Data System (ADS)

Okada, Yukimasa; Ono, Kouichi; Eriguchi, Koji

2017-06-01

Aggressive shrinkage and geometrical transition to three-dimensional structures in metal-oxide-semiconductor field-effect transistors (MOSFETs) lead to potentially serious problems regarding plasma processing such as plasma-induced physical damage (PPD). For the precise control of material processing and future device designs, it is extremely important to clarify the depth and energy profiles of PPD. Conventional methods to estimate the PPD profile (e.g., wet etching) are time-consuming. In this study, we propose an advanced method using a simple capacitance-voltage (C-V) measurement. The method first assumes the depth and energy profiles of defects in Si substrates, and then optimizes the C-V curves. We applied this methodology to evaluate the defect generation in (100), (111), and (110) Si substrates. No orientation dependence was found regarding the surface-oxide layers, whereas a large number of defects was assigned in the case of (110). The damaged layer thickness and areal density were estimated. This method provides the highly sensitive PPD prediction indispensable for designing future low-damage plasma processes.

High-voltage pulsed generator for dynamic fragmentation of rocks

NASA Astrophysics Data System (ADS)

Kovalchuk, B. M.; Kharlov, A. V.; Vizir, V. A.; Kumpyak, V. V.; Zorin, V. B.; Kiselev, V. N.

2010-10-01

A portable high-voltage (HV) pulsed generator has been designed for rock fragmentation experiments. The generator can be used also for other technological applications. The installation consists of low voltage block, HV block, coaxial transmission line, fragmentation chamber, and control system block. Low voltage block of the generator, consisting of a primary capacitor bank (300 μF) and a thyristor switch, stores pulse energy and transfers it to the HV block. The primary capacitor bank stores energy of 600 J at the maximum charging voltage of 2 kV. HV block includes HV pulsed step up transformer, HV capacitive storage, and two electrode gas switch. The following technical parameters of the generator were achieved: output voltage up to 300 kV, voltage rise time of ˜50 ns, current amplitude of ˜6 kA with the 40 Ω active load, and ˜20 kA in a rock fragmentation regime (with discharge in a rock-water mixture). Typical operation regime is a burst of 1000 pulses with a frequency of 10 Hz. The operation process can be controlled within a wide range of parameters. The entire installation (generator, transmission line, treatment chamber, and measuring probes) is designed like a continuous Faraday's cage (complete shielding) to exclude external electromagnetic perturbations.

High-voltage pulsed generator for dynamic fragmentation of rocks.

PubMed

Kovalchuk, B M; Kharlov, A V; Vizir, V A; Kumpyak, V V; Zorin, V B; Kiselev, V N

2010-10-01

A portable high-voltage (HV) pulsed generator has been designed for rock fragmentation experiments. The generator can be used also for other technological applications. The installation consists of low voltage block, HV block, coaxial transmission line, fragmentation chamber, and control system block. Low voltage block of the generator, consisting of a primary capacitor bank (300 μF) and a thyristor switch, stores pulse energy and transfers it to the HV block. The primary capacitor bank stores energy of 600 J at the maximum charging voltage of 2 kV. HV block includes HV pulsed step up transformer, HV capacitive storage, and two electrode gas switch. The following technical parameters of the generator were achieved: output voltage up to 300 kV, voltage rise time of ∼50 ns, current amplitude of ∼6 kA with the 40 Ω active load, and ∼20 kA in a rock fragmentation regime (with discharge in a rock-water mixture). Typical operation regime is a burst of 1000 pulses with a frequency of 10 Hz. The operation process can be controlled within a wide range of parameters. The entire installation (generator, transmission line, treatment chamber, and measuring probes) is designed like a continuous Faraday's cage (complete shielding) to exclude external electromagnetic perturbations.

Environmentally friendly power generator based on moving liquid dielectric and double layer effect

PubMed Central

Huynh, D. H.; Nguyen, T. C.; Nguyen, P. D.; Abeyrathne, C. D.; Hossain, Md. S.; Evans, R.; Skafidas, E.

2016-01-01

An electrostatic power generator converts mechanical energy to electrical energy by utilising the principle of variable capacitance. This change in capacitance is usually achieved by varying the gap or overlap between two parallel metallic plates. This paper proposes a novel electrostatic micro power generator where the change in capacitance is achieved by the movement of an aqueous solution of NaCl. A significant change in capacitance is achieved due to the higher than air dielectric constant of water and the Helmholtz double layer capacitor formed by ion separation at the electrode interfaces. The proposed device has significant advantages over traditional electrostatic devices which include low bias voltage and low mechanical frequency of operation. This is critical if the proposed device is to have utility in harvesting power from the environment. A figure of merit exceeding 10000(108μW)/(mm2HzV2) which is two orders of magnitude greater than previous devices, is demonstrated for a prototype operating at a bias voltage of 1.2 V and a droplet frequency of 6 Hz. Concepts are presented for large scale power harvesting. PMID:27255577

Thiocyanates as attractive redox-active electrolytes for high-energy and environmentally-friendly electrochemical capacitors.

PubMed

Gorska, Barbara; Bujewska, Paulina; Fic, Krzysztof

2017-03-15

This manuscript reports on the novel insight into the development of high voltage carbon/carbon electrochemical capacitors operating in aqueous solutions of alkali metals and ammonium thiocyanates (KSCN, NaSCN, LiSCN, and NH 4 SCN). The effect of salt concentration, electrode porosity and current collectors on the capacitance value, system stability, and power performance has been investigated. Therefore, thiocyanate-based electrolytes were recognized as cheap and highly conductive electrolytic solutions (up to 401 mS cm -1 for NH 4 SCN at RT) allowing a cell voltage of 1.6 V in a symmetric carbon/carbon system to be achieved. At the same time, they display an attractive redox activity, enhancing the energy of the device with a good performance during cycling.

Redox-Active Hydrogel Polymer Electrolytes with Different pH Values for Enhancing the Energy Density of the Hybrid Solid-State Supercapacitor.

PubMed

Tang, Xiaohui; Lui, Yu Hui; Merhi, Abdul Rahman; Chen, Bolin; Ding, Shaowei; Zhang, Bowei; Hu, Shan

2017-12-27

To enhance the energy density of solid-state supercapacitors, a novel solid-state cell, made of redox-active poly(vinyl alcohol) (PVA) hydrogel electrolytes and functionalized carbon nanotube-coated cellulose paper electrodes, was investigated in this work. Briefly, acidic PVA-[BMIM]Cl-lactic acid-LiBr and neutral PVA-[BMIM]Cl-sodium acetate-LiBr hydrogel polymer electrolytes are used as catholyte and anolyte, respectively. The acidic condition of the catholyte contributes to suppression of the undesired irreversible reaction of Br - and extension of the oxygen evolution reaction potential to a higher value than that of the redox potential of Br - /Br 3 - reaction. The observed Br - /Br 3 - redox activity at the cathode contributes to enhance the cathode capacitance. The neutral condition of the anolyte helps extend the operating voltage window of the supercapacitor by introducing hydrogen evolution reaction overpotential to the anode. The electrosorption of nascent H on the negative electrode also increases the anode capacitance. As a result, the prepared solid-state hybrid supercapacitor shows a broad voltage window of 1.6 V, with a high Coulombic efficiency of 97.6% and the highest energy density of 16.3 Wh/kg with power density of 932.6 W/kg at 2 A/g obtained. After 10 000 cycles of galvanostatic charge and discharge tests at the current density of 10 A/g, it exhibits great cyclic stability with 93.4% retention of the initial capacitance. In addition, a robust capacitive performance can also be observed from the solid-state supercapacitor at different bending angles, indicating its great potential as a flexible energy storage device.

Method and apparatus for detection of charge on ions and particles

DOEpatents

Fuerstenau, Stephen Douglas; Soli, George Arthur

2002-01-01

The present invention provides a tessellated array detector with charge collecting plate (or cup) electrode pixels and amplifying circuitry integrated into each pixel making it sensitive to external electrostatic charge; a micro collector/amplifier pixel design possessing a small capacitance to ensure a high charge to voltage signal conversion for low noise/high sensitivity operation; a micro-fabricated array of such pixels to create a useful macroscopic target area for ion and charged particle collection.

Engineering three-dimensional hybrid supercapacitors and microsupercapacitors for high-performance integrated energy storage

PubMed Central

El-Kady, Maher F.; Ihns, Melanie; Li, Mengping; Hwang, Jee Youn; Mousavi, Mir F.; Chaney, Lindsay; Lech, Andrew T.; Kaner, Richard B.

2015-01-01

Supercapacitors now play an important role in the progress of hybrid and electric vehicles, consumer electronics, and military and space applications. There is a growing demand in developing hybrid supercapacitor systems to overcome the energy density limitations of the current generation of carbon-based supercapacitors. Here, we demonstrate 3D high-performance hybrid supercapacitors and microsupercapacitors based on graphene and MnO2 by rationally designing the electrode microstructure and combining active materials with electrolytes that operate at high voltages. This results in hybrid electrodes with ultrahigh volumetric capacitance of over 1,100 F/cm3. This corresponds to a specific capacitance of the constituent MnO2 of 1,145 F/g, which is close to the theoretical value of 1,380 F/g. The energy density of the full device varies between 22 and 42 Wh/l depending on the device configuration, which is superior to those of commercially available double-layer supercapacitors, pseudocapacitors, lithium-ion capacitors, and hybrid supercapacitors tested under the same conditions and is comparable to that of lead acid batteries. These hybrid supercapacitors use aqueous electrolytes and are assembled in air without the need for expensive “dry rooms” required for building today’s supercapacitors. Furthermore, we demonstrate a simple technique for the fabrication of supercapacitor arrays for high-voltage applications. These arrays can be integrated with solar cells for efficient energy harvesting and storage systems. PMID:25831542

Engineering three-dimensional hybrid supercapacitors and microsupercapacitors for high-performance integrated energy storage.

PubMed

El-Kady, Maher F; Ihns, Melanie; Li, Mengping; Hwang, Jee Youn; Mousavi, Mir F; Chaney, Lindsay; Lech, Andrew T; Kaner, Richard B

2015-04-07

Supercapacitors now play an important role in the progress of hybrid and electric vehicles, consumer electronics, and military and space applications. There is a growing demand in developing hybrid supercapacitor systems to overcome the energy density limitations of the current generation of carbon-based supercapacitors. Here, we demonstrate 3D high-performance hybrid supercapacitors and microsupercapacitors based on graphene and MnO2 by rationally designing the electrode microstructure and combining active materials with electrolytes that operate at high voltages. This results in hybrid electrodes with ultrahigh volumetric capacitance of over 1,100 F/cm(3). This corresponds to a specific capacitance of the constituent MnO2 of 1,145 F/g, which is close to the theoretical value of 1,380 F/g. The energy density of the full device varies between 22 and 42 Wh/l depending on the device configuration, which is superior to those of commercially available double-layer supercapacitors, pseudocapacitors, lithium-ion capacitors, and hybrid supercapacitors tested under the same conditions and is comparable to that of lead acid batteries. These hybrid supercapacitors use aqueous electrolytes and are assembled in air without the need for expensive "dry rooms" required for building today's supercapacitors. Furthermore, we demonstrate a simple technique for the fabrication of supercapacitor arrays for high-voltage applications. These arrays can be integrated with solar cells for efficient energy harvesting and storage systems.

Electrical characteristics of TMAH-surface treated Ni/Au/Al2O3/GaN MIS Schottky structures

NASA Astrophysics Data System (ADS)

Reddy, M. Siva Pratap; Lee, Jung-Hee; Jang, Ja-Soon

2014-03-01

The electrical characteristics and reverse leakage mechanisms of tetramethylammonium hydroxide (TMAH) surface-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes were investigated by using the current-voltage ( I-V) and capacitance-voltage ( C-V) characteristics. The MIS diode was formed on n-GaN after etching the AlGaN in the AlGaN/GaN heterostructures. The TMAH-treated MIS diode showed better Schottky characteristics with a lower ideality factor, higher barrier height and lower reverse leakage current compared to the TMAH-free MIS diode. In addition, the TMAH-free MIS diodes exhibited a transition from Poole-Frenkel emission at low voltages to Schottky emission at high voltages, whereas the TMAH-treated MIS diodes showed Schottky emission over the entire voltage range. Reasonable mechanisms for the improved device-performance characteristics in the TMAH-treated MIS diode are discussed in terms of the decreased interface state density or traps associated with an oxide material and the reduced tunneling probability.

A multi-channel capacitive probe for electrostatic fluctuation measurement in the Madison Symmetric Torus reversed field pinch.

PubMed

Tan, Mingsheng; Stone, Douglas R; Triana, Joseph C; Almagri, Abdulgader F; Fiksel, Gennady; Ding, Weixing; Sarff, John S; McCollam, Karsten J; Li, Hong; Liu, Wandong

2017-02-01

A 40-channel capacitive probe has been developed to measure the electrostatic fluctuations associated with the tearing modes deep into Madison Symmetric Torus (MST) reversed field pinch plasma. The capacitive probe measures the ac component of the plasma potential via the voltage induced on stainless steel electrodes capacitively coupled with the plasma through a thin annular layer of boron nitride (BN) dielectric (also serves as the particle shield). When bombarded by the plasma electrons, BN provides a sufficiently large secondary electron emission for the induced voltage to be very close to the plasma potential. The probe consists of four stalks each with ten cylindrical capacitors that are radially separated by 1.5 cm. The four stalks are arranged on a 1.3 cm square grid so that at each radial position, there are four electrodes forming a square grid. Every two adjacent radial sets of four electrodes form a cube. The fluctuating electric field can be calculated by the gradient of the plasma potential fluctuations at the eight corners of the cube. The probe can be inserted up to 15 cm (r/a = 0.7) into the plasma. The capacitive probe has a frequency bandwidth from 13 Hz to 100 kHz, amplifier-circuit limit, sufficient for studying the tearing modes (5-30 kHz) in the MST reversed-field pinch.

Solution Processed PEDOT Analogues in Electrochemical Supercapacitors.

PubMed

Österholm, Anna M; Ponder, James F; Kerszulis, Justin A; Reynolds, John R

2016-06-01

We have designed fully soluble ProDOTx-EDOTy copolymers that are electrochemically equivalent to electropolymerized PEDOT without using any surfactants or dispersants. We show that these copolymers can be incorporated as active layers in solution processed thin film supercapacitors to demonstrate capacitance, stability, and voltage similar to the values of those that use electrodeposited PEDOT as the active material with the added advantage of the possibility for large scale, high-throughput processing. These Type I supercapacitors provide exceptional cell voltages (up to 1.6 V), highly symmetrical charge/discharge behavior, promising long-term stability exceeding 50 000 charge/discharge cycles, as well as energy (4-18 Wh/kg) and power densities (0.8-3.3 kW/kg) that are comparable to those of electrochemically synthesized analogues.

Energy dissipation on ion-accelerator grids during high-voltage breakdown

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menon, M.M.; Ponte, N.S.

1981-01-01

The effects of stored energy in the system capacitance across the accelerator grids during high voltage vacuum breakdown are examined. Measurements were made of the current flow and the energy deposition on the grids during breakdown. It is shown that only a portion (less than or equal to 40 J) of the total stored energy (congruent to 100 J) is actually dissipated on the grids. Most of the energy is released during the formation phase of the vacuum arc and is deposited primarily on the most positive grid. Certain abnormal situations led to energy depositions of about 200 J onmore » the grid, but the ion accelerator endured them without exhibiting any deterioration in performance.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lutzer, B.; Simsek, S.; Zimmermann, C.

In order to improve the electrical behaviour of metal-insulator-metal capacitors with ZrO{sub 2} insulator grown by Atomic Layer Deposition, the influence of the insertion of interfacial Cr layers between Pt electrodes and the zirconia is investigated. An improvement of the α-voltage coefficient of capacitance as low as 567 ppm/V{sup 2} is achieved for a single layer of Cr while maintaining a high capacitance density of 10.7 fF/μm{sup 2} and a leakage current of less than 1.2 × 10{sup −8} A/cm{sup 2} at +1 V. The role of the interface is discussed by means of X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy showing themore » formation of Zr stabilized chromia oxide phase with a dielectric constant of 16.« less

Frequency domain analysis of droplet-based electrostatic transducers

NASA Astrophysics Data System (ADS)

Allegretto, Graham; Dobashi, Yuta; Dixon, Katelyn; Wyss, Justin; Yao, Dickson; Madden, John D. W.

2018-07-01

Squeezing a water droplet between two electrodes can generate a potential difference by converting some of the mechanical energy in vibrations into electrical energy. By utilizing the high capacitance inherent to electric double layers, and the surface charging at a polymer/water interface, we demonstrate a sensor that generates up to 892 mV peak-to-peak between 1 and 100 Hz, in response to a 250 μm deformation. This frequency response is described and explained using a linearized model in which the interfacial charge acts as the priming voltage, removing the need for external charging normally required in capacitive generators. The model suggests how to design the cell for maximum power output and provides an intuitive understanding of the high pass nature of the sensor. It successfully predicts the point of maximum power transfer.

High Isolation Single-Pole Four-Throw RF MEMS Switch Based on Series-Shunt Configuration

PubMed Central

Khaira, Navjot

2014-01-01

This paper presents a novel design of single-pole four-throw (SP4T) RF-MEMS switch employing both capacitive and ohmic switches. It is designed on high-resistivity silicon substrate and has a compact area of 1.06 mm2. The series or ohmic switches have been designed to provide low insertion loss with good ohmic contact. The pull-in voltage for ohmic switches is calculated to be 7.19 V. Shunt or capacitive switches have been used in each port to improve the isolation for higher frequencies. The proposed SP4T switch provides excellent RF performances with isolation better than 70.64 dB and insertion loss less than 0.72 dB for X-band between the input port and each output port. PMID:24711730

Solar Array Hysteresis and its Interaction with the MPPT System

NASA Astrophysics Data System (ADS)

Fernandez, A.; Baur, C.; Gomez-Carpintero, F.

2014-08-01

It is well known that solar cells have a capacitance in parallel which value changes with the voltage. Depending on the section arrangement on the Solar Array, the power conversion unit connected to it will see a smaller or larger capacitance value and will have to cope with its adverse effects. In the case of converters with an MPPT, this capacitance gives place to an hysteresis effect that might shift the tracking point, reducing the power extracted from the Solar Array. This paper explores the different sides of this issue, from capacitance modelling to the effects on the MPPT. Additionally, this paper analyses a similar interaction between MPPTs and commercial SAS.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kovchavtsev, A. P., E-mail: kap@isp.nsc.ru; Tsarenko, A. V.; Guzev, A. A.

The influence of electron energy quantization in a space-charge region on the accumulation capacitance of the InAs-based metal-oxide-semiconductor capacitors (MOSCAPs) has been investigated by modeling and comparison with the experimental data from Au/anodic layer(4-20 nm)/n-InAs(111)A MOSCAPs. The accumulation capacitance for MOSCAPs has been calculated by the solution of Poisson equation with different assumptions and the self-consistent solution of Schrödinger and Poisson equations with quantization taken into account. It was shown that the quantization during the MOSCAPs accumulation capacitance calculations should be taken into consideration for the correct interface states density determination by Terman method and the evaluation of gate dielectric thicknessmore » from capacitance-voltage measurements.« less

Highly Stretchable Waterproof Fiber Asymmetric Supercapacitors in an Integrated Structure.

PubMed

Guo, Kai; Wang, Xianfu; Hu, Lintong; Zhai, Tianyou; Li, Huiqiao; Yu, Neng

2018-06-01

Fiber supercapacitors have attracted tremendous attention as promising power source candidates for the next generation of wearable electronics, which are flexible, stretchable, and washable. Although asymmetric fiber supercapacitors with a high energy density have been achieved, their stretchability is no more than 200%, and they still face mechanical instability and an unreliable waterproof structure. This work develops a highly integrated structure for a waterproof, highly stretchable, and asymmetric fiber-shaped supercapacitor, which is assembled by integrating a helix-shaped asymmetric fiber supercapacitor into a bifunctional polymer. The asymmetric fiber supercapacitor demonstrates a working voltage of 1.6 V, a high energy density of 2.86 mW h/cm 3 , has unchanged capacitance after being immersed in water for 50 h, and retains 95% of its initial capacitance after 3000 cycles of stretching-releasing at a maximum strain of 400%. The extraordinary waterproof capability, the large stretching strain, and excellent stretching stability are attributed to the highly integrated structure design, which can also simplify the assembly process of stretchable, waterproof fiber supercapacitors.

Discharge processes and an electrical model of atmospheric pressure plasma jets in argon

NASA Astrophysics Data System (ADS)

Fang, Zhi; Shao, Tao; Yang, Jing; Zhang, Cheng

2016-01-01

In this paper, an atmospheric pressure plasma discharge in argon was generated using a needle-to-ring electrode configuration driven by a sinusoidal excitation voltage. The electric discharge processes and discharge characteristics were investigated by inspecting the voltage-current waveforms, Lissajous curves and lighting emission images. The change in discharge mode with applied voltage amplitude was studied and characterised, and three modes of corona discharge, dielectric barrier discharge (DBD) and jet discharge were identified, which appeared in turn with increasing applied voltage and can be distinguished clearly from the measured voltage-current waveforms, light-emission images and the changing gradient of discharge power with applied voltage. Based on the experimental results and discharge mechanism analysis, an equivalent electrical model and the corresponding equivalent circuit for characterising the whole discharge processes accurately was proposed, and the three discharge stages were characterised separately. A voltage-controlled current source (VCCS) associated with a resistance and a capacitance were used to represent the DBD stage, and the plasma plume and corona discharge were modelled by a variable capacitor in series with a variable resistor. Other factors that can influence the discharge, such as lead and stray capacitance values of the circuit, were also considered in the proposed model. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.

Morphology controlled synthesis of monodisperse cobalt hydroxide for supercapacitor with high performance and long cycle life

NASA Astrophysics Data System (ADS)

Tang, Yongfu; Liu, Yanyan; Yu, Shengxue; Mu, Shichun; Xiao, Shaohua; Zhao, Yufeng; Gao, Faming

2014-06-01

A facile hydrothermal process with hexadecyltrimethyl ammonium bromide (CTAB) as the soft template is proposed to tune the morphology and size of cobalt hydroxide (Co(OH)2). Monodisperse β-phase Co(OH)2 nanowires with uniform size are obtained by controlling the CTAB content and the reaction time. Due to the uniform well-defined morphology and stable structure, the Co(OH)2 nanowires material exhibits high capacitive performance and long cycle life. The specific capacitance of the Co(OH)2 nanowires electrode is 358 F g-1 at 0.5 A g-1, and even 325 F g-1 at 10 A g-1. The specific capacitance retention is 86.3% after 5000 charge-discharge cycles at 2 A g-1. Moreover, the asymmetric supercapacitor is assembled with Co(OH)2 nanowires and nitrite acid treated activated carbon (NTAC), which shows an energy density of 13.6 Wh kg-1 at the power density of 153 W kg-1 under a high voltage of 1.6 V, and 13.1 Wh kg-1 even at the power density of 1.88 kW kg-1.

Development of longitudinally excited CO2 laser

NASA Astrophysics Data System (ADS)

Masroon, N. S.; Tanaka, M.; Tei, M.; Uno, K.; Tsuyama, M.; Nakano, H.

2018-05-01

Simple, compact, and affordable discharged-pumped CO2 laser controlled by a fast high voltage solid state switch has been developed. In this study, longitudinal excitation scheme has been adapted for simple configuration. In the longitudinal excitation scheme, the discharge is produced along the direction of the laser axis, and the electrodes are well separated with a small discharge cross-section. Triggered spark gap switch is usually used to switch out the high voltage because of simple and low cost. However, the triggered spark gap operates in the arc mode and suffer from recovery problem causing a short life time and low efficiency for high repetition rate operation. As a result, there is now considerable interest in replacing triggered spark gap switch with solid state switches. Solid state switches have significant advantages compared to triggered spark gap switch which include longer service lifetime, low cost and stable high trigger pulse. We have developed simple and low cost fast high voltage solid state switch that consists of series connected-MOSFETs. It has been installed to the longitudinally excited CO2 laser to realize the gap switch less operation. Characteristics of laser oscillation by varying the discharge length, charging voltage, capacitance and gas pressure have been evaluated. Longer discharge length produce high power of laser oscillation. Optimum charging voltage and gas pressure were existed for longitudinally excited CO2 laser.

Fabrication and Characterization of CMOS-MEMS Magnetic Microsensors

PubMed Central

Hsieh, Chen-Hsuan; Dai, Ching-Liang; Yang, Ming-Zhi

2013-01-01

This study investigates the design and fabrication of magnetic microsensors using the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process. The magnetic sensor is composed of springs and interdigitated electrodes, and it is actuated by the Lorentz force. The finite element method (FEM) software CoventorWare is adopted to simulate the displacement and capacitance of the magnetic sensor. A post-CMOS process is utilized to release the suspended structure. The post-process uses an anisotropic dry etching to etch the silicon dioxide layer and an isotropic dry etching to remove the silicon substrate. When a magnetic field is applied to the magnetic sensor, it generates a change in capacitance. A sensing circuit is employed to convert the capacitance variation of the sensor into the output voltage. The experimental results show that the output voltage of the magnetic microsensor varies from 0.05 to 1.94 V in the magnetic field range of 5–200 mT. PMID:24172287

Power converter using near-load output capacitance, direct inductor contact, and/or remote current sense

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coteus, Paul W.; Ferencz, Andrew; Hall, Shawn A.

An apparatus includes a first circuit board including first components including a load, and a second circuit board including second components including switching power devices and an output inductor. Ground and output voltage contacts between the circuit boards are made through soldered or connectorized interfaces. Certain components on the first circuit board and certain components, including the output inductor, on the second circuit board act as a DC-DC voltage converter for the load. An output capacitance for the conversion is on the first circuit board with no board-to-board interface between the output capacitance and the load. The inductance of themore » board-to-board interface functions as part of the output inductor's inductance and not as a parasitic inductance. Sense components for sensing current through the output inductor are located on the first circuit board. Parasitic inductance of the board-to-board interface has less effect on a sense signal provided to a controller.« less

Origin of flatband voltage shift and unusual minority carrier generation in thermally grown GeO2/Ge metal-oxide-semiconductor devices

NASA Astrophysics Data System (ADS)

Hosoi, Takuji; Kutsuki, Katsuhiro; Okamoto, Gaku; Saito, Marina; Shimura, Takayoshi; Watanabe, Heiji

2009-05-01

Improvement in electrical properties of thermally grown GeO2/Ge metal-oxide-semiconductor (MOS) capacitors, such as significantly reduced flatband voltage (VFB) shift, small hysteresis, and minimized minority carrier response in capacitance-voltage (C-V) characteristics, has been demonstrated by in situ low temperature vacuum annealing prior to gate electrode deposition. Thermal desorption analysis has revealed that not only water but also hydrocarbons are easily infiltrated into GeO2 layers during air exposure and desorbed at around 300 °C, indicating that organic molecules within GeO2/Ge MOS structures are possible origins of electrical defects. The inversion capacitance, indicative of minority carrier generation, increases with air exposure time for Au/GeO2/Ge MOS capacitors, while maintaining an interface state density (Dit) of about a few 1011 cm-2 eV-1. Unusual increase in inversion capacitance was found to be suppressed by Al2O3 capping (Au/Al2O3/GeO2/Ge structures). This suggests that electrical defects induced outside the Au electrode by infiltrated molecules may enhance the minority carrier generation, and thus acting as a minority carrier source just like MOS field-effect transistors.

Performance, stability and operation voltage optimization of screen-printed aqueous supercapacitors

PubMed Central

Lehtimäki, Suvi; Railanmaa, Anna; Keskinen, Jari; Kujala, Manu; Tuukkanen, Sampo; Lupo, Donald

2017-01-01

Harvesting micropower energy from the ambient environment requires an intermediate energy storage, for which printed aqueous supercapacitors are well suited due to their low cost and environmental friendliness. In this work, a systematic study of a large set of devices is used to investigate the effect of process variability and operating voltage on the performance and stability of screen printed aqueous supercapacitors. The current collectors and active layers are printed with graphite and activated carbon inks, respectively, and aqueous NaCl used as the electrolyte. The devices are characterized through galvanostatic discharge measurements for quantitative determination of capacitance and equivalent series resistance (ESR), as well as impedance spectroscopy for a detailed study of the factors contributing to ESR. The capacitances are 200–360 mF and the ESRs 7.9–12.7 Ω, depending on the layer thicknesses. The ESR is found to be dominated by the resistance of the graphite current collectors and is compatible with applications in low-power distributed electronics. The effects of different operating voltages on the capacitance, leakage and aging rate of the supercapacitors are tested, and 1.0 V found to be the optimal choice for using the devices in energy harvesting applications. PMID:28382962

Investigation of voltage source design's for Electrical Impedance Mammography (EIM) Systems.

PubMed

Qureshi, Tabassum R; Chatwin, Chris R; Zhou, Zhou; Li, Nan; Wang, W

2012-01-01

According to Jossient, interesting characteristics of breast tissues mostly lie above 1MHz; therefore a wideband excitation source covering higher frequencies (i.e. above 1MHz) is required. The main objective of this research is to establish a feasible bandwidth envelope that can be used to design a constant EIM voltage source over a wide bandwidth with low output impedance for practical implementation. An excitation source is one of the major components in bio-impedance measurement systems. In any bio-impedance measurement system the excitation source can be achieved either by injecting current and measuring the resulting voltages, or by applying voltages and measuring the current developed. This paper describes three voltage source architectures and based on their bandwidth comparison; a differential voltage controlled voltage source (VCVS) is proposed, which can be used over a wide bandwidth (>15MHz). This paper describes the performance of the designed EIM voltage source for different load conditions and load capacitances reporting signal-to-noise ratio of approx 90dB at 10MHz frequency, signal phase and maximum of 4.75kΩ source output impedance at 10MHz. Optimum data obtained using Pspice® is used to demonstrate the high-bandwidth performance of the source.

Low power, highly linear output buffer. [for infrared focal plane arrays

NASA Technical Reports Server (NTRS)

Foley, D.; Butler, N.; Stobie, J.

1992-01-01

A class AB CMOS output buffer has been designed for use on an IR focal plane array. Given the requirements for power dissipation and load capacitance a class A output, such as a source follower, would be unsuitable. The approach taken uses a class AB amplifier configured as a charge integrator. Thus it converts a charge packet in the focal plane multiplexer to a voltage which is then the output of the focal plane. With a quiescent current of 18 micro-a and a load capacitance of 100 pf, the amplifier has an open loop unity gain bandwidth of 900 khz. Integral nonlinearity is better than .03 percent over 5.5 volts when run with VDD-VSS = 6v.

HYGROMETER

DOEpatents

Stover, C.M.

1963-01-29

This pntent relates to a hygrometer having a rapid and essentially straight line response to changes in relntive humidity and a high degree of sensitivity to moisture in the low relative humiaity range. In particular, the hygrometer comprises a metal plate coated with a hygrometric oxide coating, and electrical leads coupled to the metal plate and the oxide coating, respectively. When a change in relative humidity occurs, a change in the resistance and capacitance between the leads takes place owing to the hygrometric action of the oxide coating. Thus, with a voltage being applied to the leads, a change in capacitance and resistance between them causes a proportional change in the current between the leads. This may be read upon a suitable indicator for determining the relative humidity at any given instant. (AEC)

Ultrahigh Responsivity-Bandwidth Product in a Compact InP Nanopillar Phototransistor Directly Grown on Silicon

NASA Astrophysics Data System (ADS)

Ko, Wai Son; Bhattacharya, Indrasen; Tran, Thai-Truong D.; Ng, Kar Wei; Adair Gerke, Stephen; Chang-Hasnain, Connie

2016-09-01

Highly sensitive and fast photodetectors can enable low power, high bandwidth on-chip optical interconnects for silicon integrated electronics. III-V compound semiconductor direct-bandgap materials with high absorption coefficients are particularly promising for photodetection in energy-efficient optical links because of the potential to scale down the absorber size, and the resulting capacitance and dark current, while maintaining high quantum efficiency. We demonstrate a compact bipolar junction phototransistor with a high current gain (53.6), bandwidth (7 GHz) and responsivity (9.5 A/W) using a single crystalline indium phosphide nanopillar directly grown on a silicon substrate. Transistor gain is obtained at sub-picowatt optical power and collector bias close to the CMOS line voltage. The quantum efficiency-bandwidth product of 105 GHz is the highest for photodetectors on silicon. The bipolar junction phototransistor combines the receiver front end circuit and absorber into a monolithic integrated device, eliminating the wire capacitance between the detector and first amplifier stage.

Local epitaxial growth of ZrO2 on Ge (100) substrates by atomic layer epitaxy

NASA Astrophysics Data System (ADS)

Kim, Hyoungsub; Chui, Chi On; Saraswat, Krishna C.; McIntyre, Paul C.

2003-09-01

High-k dielectric deposition processes for gate dielectric preparation on Si surfaces usually result in the unavoidable and uncontrolled formation of a thin interfacial oxide layer. Atomic layer deposition of ˜55-Å ZrO2 film on a Ge (100) substrate using ZrCl4 and H2O at 300 °C was found to produce local epitaxial growth [(001) Ge//(001) ZrO2 and [100] Ge//[100] ZrO2] without a distinct interfacial layer, unlike the situation observed when ZrO2 is deposited using the same method on Si. Relatively large lattice mismatch (˜10%) between ZrO2 and Ge produced a high areal density of interfacial misfit dislocations. Large hysteresis (>200 mV) and high frequency dispersion were observed in capacitance-voltage measurements due to the high density of interface states. However, a low leakage current density, comparable to values obtained on Si substrates, was observed with the same capacitance density regardless of the high defect density.

Ultrahigh Responsivity-Bandwidth Product in a Compact InP Nanopillar Phototransistor Directly Grown on Silicon

PubMed Central

Ko, Wai Son; Bhattacharya, Indrasen; Tran, Thai-Truong D.; Ng, Kar Wei; Adair Gerke, Stephen; Chang-Hasnain, Connie

2016-01-01

Highly sensitive and fast photodetectors can enable low power, high bandwidth on-chip optical interconnects for silicon integrated electronics. III-V compound semiconductor direct-bandgap materials with high absorption coefficients are particularly promising for photodetection in energy-efficient optical links because of the potential to scale down the absorber size, and the resulting capacitance and dark current, while maintaining high quantum efficiency. We demonstrate a compact bipolar junction phototransistor with a high current gain (53.6), bandwidth (7 GHz) and responsivity (9.5 A/W) using a single crystalline indium phosphide nanopillar directly grown on a silicon substrate. Transistor gain is obtained at sub-picowatt optical power and collector bias close to the CMOS line voltage. The quantum efficiency-bandwidth product of 105 GHz is the highest for photodetectors on silicon. The bipolar junction phototransistor combines the receiver front end circuit and absorber into a monolithic integrated device, eliminating the wire capacitance between the detector and first amplifier stage. PMID:27659796

The voltage control for self-excited induction generator based on STATCOM

NASA Astrophysics Data System (ADS)

Yan, Dandan; Wang, Feifeng; Pan, Juntao; Long, Weijie

2018-05-01

The small independent induction generator can build up voltage under its remanent magnetizing and excitation capacitance, but it is prone to voltage sag and harmonic increment when running with load. Therefore, the controller for constant voltage is designed based on the natural coordinate system to adjust the static synchronous compensator (STATCOM), which provides two-way dynamic reactive power compensation for power generation system to achieve voltage stability and harmonic suppression. The control strategy is verified on Matlab/Sinmulik, and the results show that the STATCOM under the controller can effectively improve the load capacity and reliability of asynchronous generator.

High-conductance low-voltage organic thin film transistor with locally rearranged poly(3-hexylthiophene) domain by current annealing on plastic substrate

NASA Astrophysics Data System (ADS)

Pei, Zingway; Tsai, Hsing-Wang; Lai, Hsin-Cheng

2016-02-01

The organic material based thin film transistors (TFTs) are attractive for flexible optoelectronics applications due to the ability of lager area fabrication by solution and low temperature process on plastic substrate. Recently, the research of organic TFT focus on low operation voltage and high output current to achieve a low power organic logic circuit for optoelectronic device,such as e-paper or OLED displayer. To obtain low voltage and high output current, high gate capacitance and high channel mobility are key factors. The well-arranged polymer chain by a high temperature postannealing, leading enhancement conductivity of polymer film was a general method. However, the thermal annealing applying heat for all device on the substrate and may not applicable to plastic substrate. Therefore, in this work, the low operation voltage and high output current of polymer TFTs was demonstrated by locally electrical bias annealing. The poly(styrene-comethyl methacrylate) (PS-r-PMMA) with ultra-thin thickness is used as gate dielectric that the thickness is controlled by thermal treatment after spin coated on organic electrode. In electrical bias-annealing process, the PS-r- PMMA is acted a heating layer. After electrical bias-annealing, the polymer TFTs obtain high channel mobility at low voltage that lead high output current by a locally annealing of P3HT film. In the future, the locally electrical biasannealing method could be applied on plastic substrate for flexible optoelectronic application.

High sensitivity capacitive MEMS microphone with spring supported diaphragm

NASA Astrophysics Data System (ADS)

Mohamad, Norizan; Iovenitti, Pio; Vinay, Thurai

2007-12-01

Capacitive microphones (condenser microphones) work on a principle of variable capacitance and voltage by the movement of its electrically charged diaphragm and back plate in response to sound pressure. There has been considerable research carried out to increase the sensing performance of microphones while reducing their size to cater for various modern applications such as mobile communication and hearing aid devices. This paper reviews the development and current performance of several condenser MEMS microphone designs, and introduces a microphone with spring supported diaphragm to further improve condenser microphone performance. The numerical analysis using Coventor FEM software shows that this new microphone design has a higher mechanical sensitivity compared to the existing edge clamped flat diaphragm condenser MEMS microphone. The spring supported diaphragm is shown to have a flat frequency response up to 7 kHz and more stable under the variations of the diaphragm residual stress. The microphone is designed to be easily fabricated using the existing silicon fabrication technology and the stability against the residual stress increases its reproducibility.

Capattery double layer capacitor life performance

NASA Astrophysics Data System (ADS)

Evans, David A.; Clark, Nancy H.; Baca, W. E.; Miller, John R.; Barker, Thomas B.

Double layer capacitors (DLCs) have received increased use in computer memory backup applications for consumer products during the past ten years. Their extraordinarily high capacitance density along with their maintenance-free operation makes them particularly suited for these products. These same features also make DLCs very attractive in military type applications. Unfortunately, lifetime performance data has not been reported in the literature for any DLC component. Our objective in this study was to investigate the effects that voltage and temperature have on the properties and performance of single and series-connected DLCs as a function of time. Evans model RE110474, 0.47-farad, 11.0-volt Capatteries were evaluated. These components have a tantalum package, use welded construction, and contain a glass-to-metal seal, all incorporated to circumvent the typical DLC failure modes of electrolyte loss and container corrosion. A five-level, two-factor Central Composite Design was used in the study. Single and series-connected Capatteries rated at 85 C, 11.0-volts operation were subjected to test temperatures between 25 and 95 C, and voltages between 0 and 12.9 volts (9 test conditions). Measured responses included capacitance, equivalent series resistance, and discharge time. Data were analyzed using a regression analysis to obtain response functions relating DLC properties to their voltage, temperature, and test time history. These results are described and should aid system and component engineers in using DLCs in critical applications.

All-Solid-State High-Energy Asymmetric Supercapacitors Enabled by Three-Dimensional Mixed-Valent MnOx Nanospike and Graphene Electrodes.

PubMed

Yang, Jie; Li, Guizhu; Pan, Zhenghui; Liu, Meinan; Hou, Yuan; Xu, Yijun; Deng, Hong; Sheng, Leimei; Zhao, Xinluo; Qiu, Yongcai; Zhang, Yuegang

2015-10-14

Three-dimensional (3D) nanostructures enable high-energy storage devices. Here we report a 3D manganese oxide nanospike (NSP) array electrode fabricated by anodization and subsequent electrodeposition. All-solid-state asymmetric supercapacitors were assembled with the 3D Al@Ni@MnOx NSP as the positive electrode, chemically converted graphene (CCG) as the negative electrode, and Na2SO4/poly(vinyl alcohol) (PVA) as the polymer gel electrolyte. Taking advantage of the different potential windows of Al@Ni@MnOx NSP and CCG electrodes, the asymmetric supercapacitor showed an ideal capacitive behavior with a cell voltage up to 1.8 V, capable of lighting up a red LED indicator (nominal voltage of 1.8 V). The device could deliver an energy density of 23.02 W h kg(-1) at a current density of 1 A g(-1). It could also preserve 96.3% of its initial capacitance at a current density of 2 A g(-1) after 10000 charging/discharging cycles. The remarkable performance is attributed to the unique 3D NSP array structure that could play an important role in increasing the effective electrode surface area, facilitating electrolyte permeation, and shortening the electron pathway in the active materials.

Study of HV Dielectrics for High Frequency Operation in Linear and Nonlinear Transmission Lines (NLTLs) and Simulation and Development of Hybrid Nonlinear Lines for RF Generation

DTIC Science & Technology

2016-01-27

presented. Besides, Spice simulation provides an excellent way of studying the NLTL principle operation by comparing them with the experimental...high voltage nonlinear capacitive line (NLCL) using commercial BT and PZT ceramic capacitors. Corresponding NLCL Spice simulation is provided for...which causes a long tail on the output pulse. In special for PZT, Spice simulation of a line with respective linear capacitors illustrates its weak

Flexible, High-Speed CdSe Nanocrystal Integrated Circuits.

PubMed

Stinner, F Scott; Lai, Yuming; Straus, Daniel B; Diroll, Benjamin T; Kim, David K; Murray, Christopher B; Kagan, Cherie R

2015-10-14

We report large-area, flexible, high-speed analog and digital colloidal CdSe nanocrystal integrated circuits operating at low voltages. Using photolithography and a newly developed process to fabricate vertical interconnect access holes, we scale down device dimensions, reducing parasitic capacitances and increasing the frequency of circuit operation, and scale up device fabrication over 4 in. flexible substrates. We demonstrate amplifiers with ∼7 kHz bandwidth, ring oscillators with <10 μs stage delays, and NAND and NOR logic gates.

Electrical characterization of ALD HfO2 high-k dielectrics on ( 2 ¯ 01) β-Ga2O3

NASA Astrophysics Data System (ADS)

Shahin, David I.; Tadjer, Marko J.; Wheeler, Virginia D.; Koehler, Andrew D.; Anderson, Travis J.; Eddy, Charles R.; Christou, Aris

2018-01-01

The electrical quality of HfO2 dielectrics grown by thermal atomic layer deposition at 175 °C on n-type ( 2 ¯ 01) β-Ga2O3 has been studied through capacitance- and current-voltage measurements on metal-oxide-semiconductor capacitors. These capacitors exhibited excellent electrical characteristics, including dual-sweep capacitance-voltage curves with low hysteresis and stretch-out and a frequency-stable dielectric constant of k˜14 when measured between 10 kHz and 1 MHz. The C-V curves exhibited a uniform and repeatable +1.05 V shift relative to the ideal case when swept from 3.5 to -5 V, yielding positively measured flatband (+2.15 V) and threshold (+1.05 V) voltages that may be useful for normally off n-channel Ga2O3 devices. Using the Terman method, an average interface trap density of 1.3 × 1011 cm-2.eV-1 was obtained between 0.2 and 0.6 eV below the conduction band edge. The forward bias current-voltage characteristic was successfully fitted to the Fowler-Nordheim tunneling model at a field strength of 5 MV/cm, allowing an extraction of a 1.3 eV conduction band offset between HfO2 and Ga2O3, which matches the value previously determined from x-ray photoelectron spectroscopy. However, a temperature dependence in the leakage current was observed. These results suggest that HfO2 is an appealing dielectric for Ga2O3 device applications.

Top-gate organic depletion and inversion transistors with doped channel and injection contact

NASA Astrophysics Data System (ADS)

Liu, Xuhai; Kasemann, Daniel; Leo, Karl

2015-03-01

Organic field-effect transistors constitute a vibrant research field and open application perspectives in flexible electronics. For a commercial breakthrough, however, significant performance improvements are still needed, e.g., stable and high charge carrier mobility and on-off ratio, tunable threshold voltage, as well as integrability criteria such as n- and p-channel operation and top-gate architecture. Here, we show pentacene-based top-gate organic transistors operated in depletion and inversion regimes, realized by doping source and drain contacts as well as a thin layer of the transistor channel. By varying the doping concentration and the thickness of the doped channel, we control the position of the threshold voltage without degrading on-off ratio or mobility. Capacitance-voltage measurements show that an inversion channel can indeed be formed, e.g., an n-doped channel can be inverted to a p-type inversion channel with highly p-doped contacts. The Cytop polymer dielectric minimizes hysteresis, and the transistors can be biased for prolonged cycles without a shift of threshold voltage, indicating excellent operation stability.

Improved linearity in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with nonlinear polarization dielectric

NASA Astrophysics Data System (ADS)

Gao, Tao; Xu, Ruimin; Kong, Yuechan; Zhou, Jianjun; Kong, Cen; Dong, Xun; Chen, Tangsheng

2015-06-01

We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr0.52Ti0.48)-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (gm-Vg) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectric constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric.

Instability of phosphorous doped SiO2 in 4H-SiC MOS capacitors at high temperatures

NASA Astrophysics Data System (ADS)

Idris, M. I.; Weng, M. H.; Chan, H.-K.; Murphy, A. E.; Clark, D. T.; Young, R. A. R.; Ramsay, E. P.; Wright, N. G.; Horsfall, A. B.

2016-12-01

In this paper, the effect of inclusion of phosphorous (at a concentration below 1%) on the high temperature characteristics (up to 300 °C) of the SiO2/SiC interface is investigated. Capacitance-voltage measurements taken for a range of frequencies have been utilized to extract parameters including flatband voltage, threshold voltage, effective oxide charge, and interface state density. The variation of these parameters with temperature has been investigated for bias sweeps in opposing directions and a comparison made between phosphorous doped and as-grown oxides. At room temperature, the effective oxide charge for SiO2 may be reduced by the phosphorous termination of dangling bonds at the interface. However, at high temperatures, the effective charge in the phosphorous doped oxide remains unstable and effects such as flatband voltage shift and threshold voltage shift dominate the characteristics. The instability in these characteristics was found to result from the trapped charges in the oxide (±1012 cm-3) or near interface traps at the interface of the gate oxide and the semiconductor (1012-1013 cm-2 eV-1). Hence, the performance enhancements observed for phosphorous doped oxides are not realised in devices operated at elevated temperatures.

Bacterial cellulose-based sheet-like carbon aerogels for the in situ growth of nickel sulfide as high performance electrode materials for asymmetric supercapacitors.

PubMed

Zuo, Lizeng; Fan, Wei; Zhang, Youfang; Huang, Yunpeng; Gao, Wei; Liu, Tianxi

2017-03-30

Electroactive materials, such as nickel sulfide (NiS), with high theoretical capacities have attracted broad interest to fabricate highly efficient supercapacitors. Preventing aggregation and increasing the conductivity of NiS particles are key challenging tasks to fully achieve excellent electrochemical properties of NiS. One effective approach to solve these problems is to combine NiS with highly porous and conductive carbon materials such as carbon aerogels. In this study, a green and facile method for the in situ growth of NiS particles on bacterial cellulose (BC)-derived sheet-like carbon aerogels (CAs) has been reported. CA prepared by the dissolution-gelation-carbonization process was used as a framework to construct NiS/CA composite aerogels with NiS uniformly decorated on the pore walls of CA. It was found that the NiS/CA composite aerogel electrodes exhibit excellent capacitive performance with high specific capacitance (1606 F g -1 ), good rate capacitance retention (69% at 10 A g -1 ), and enhanced cycling stability (91.2% retention after 10 000 continuous cyclic voltammetry cycles at 100 mV s -1 ). Furthermore, asymmetric supercapacitors (ASCs) were constructed utilizing NiS/CA composite and CA as the positive and negative electrode materials, respectively. Through the synergistic effect of three-dimensional porous structures and conductive networks derived from CA and the high capacitive performance offered by NiS, the ASC device exhibited an energy density of ∼21.5 Wh kg -1 and a power density of 700 W kg -1 at the working voltage of 1.4 V in 2 M KOH aqueous solution. The ASC device also showed excellent long-term cycle stability with ∼87.1% specific capacitance retention after 10 000 cycles of cyclic voltammetry scans. Therefore, the NiS/CA composite shows great potential as a promising alternative to high-performance electrode materials for supercapacitors.

Electrodeposition and Capacitive Behavior of Films for Electrodes of Electrochemical Supercapacitors

NASA Astrophysics Data System (ADS)

Shi, C.; Zhitomirsky, I.

2010-03-01

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0-3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g-1 was observed for the sample with a specific mass of 89 μg cm-2 at a scan rate of 2 mV s-1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES).

Electrodeposition and capacitive behavior of films for electrodes of electrochemical supercapacitors.

PubMed

Shi, C; Zhitomirsky, I

2010-01-08

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0-3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g-1 was observed for the sample with a specific mass of 89 μg cm-2 at a scan rate of 2 mV s-1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES).

Electrodeposition and Capacitive Behavior of Films for Electrodes of Electrochemical Supercapacitors

PubMed Central

2010-01-01

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0–3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g−1 was observed for the sample with a specific mass of 89 μg cm−2 at a scan rate of 2 mV s−1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES). PMID:20672082

Adaptive piezoelectric sensoriactuator

NASA Technical Reports Server (NTRS)

Clark, Jr., Robert L. (Inventor); Vipperman, Jeffrey S. (Inventor); Cole, Daniel G. (Inventor)

1996-01-01

An adaptive algorithm implemented in digital or analog form is used in conjunction with a voltage controlled amplifier to compensate for the feedthrough capacitance of piezoelectric sensoriactuator. The mechanical response of the piezoelectric sensoriactuator is resolved from the electrical response by adaptively altering the gain imposed on the electrical circuit used for compensation. For wideband, stochastic input disturbances, the feedthrough capacitance of the sensoriactuator can be identified on-line, providing a means of implementing direct-rate-feedback control in analog hardware. The device is capable of on-line system health monitoring since a quasi-stable dynamic capacitance is indicative of sustained health of the piezoelectric element.

Note: Wide band amplifier for quartz tuning fork sensors with digitally controlled stray capacitance compensation.

PubMed

Peng, Ping; Hao, Lifeng; Ding, Ning; Jiao, Weicheng; Wang, Qi; Zhang, Jian; Wang, Rongguo

2015-11-01

We presented a preamplifier design for quartz tuning fork (QTF) sensors in which the stray capacitance is digitally compensated. In this design, the manually controlled variable capacitor is replaced by a pair of varicap diodes, whose capacitance could be accurately tuned by a bias voltage. A tuning circuit including a single side low power operational amplifier, a digital-to-analog converter, and a microprocessor is also described, and the tuning process can be conveniently carried out on a personal computer. For the design, the noise level was investigated experimentally.

Defect states and their energetic position and distribution in organic molecular semiconductors

NASA Astrophysics Data System (ADS)

Sharma, Akanksha; Yadav, Sarita; Kumar, Pramod; Ray Chaudhuri, Sumita; Ghosh, Subhasis

2013-04-01

Energetic position and distribution of defect states due to structural disorder in pentacene and copper phthalocyanine have been obtained by capacitance based spectroscopic techniques. It has been shown that capacitance-frequency and capacitance-voltage characteristics exhibit Gaussian distribution of traps with an energetic position at around 0.5 eV above the highest occupied molecular orbital level of the pentacene and CuPc. These traps have been created by varying growth conditions and almost identical trap parameters in pentacene and copper phthalocyanine indicate that similar structural disorder is responsible for these traps.

Hierarchical Ni-Co layered double hydroxide nanosheets on functionalized 3D-RGO films for high energy density asymmetric supercapacitor

NASA Astrophysics Data System (ADS)

Jiang, Liyang; Sui, Yanwei; Qi, Jiqiu; Chang, Yuan; He, Yezeng; Meng, Qingkun; Wei, Fuxiang; Sun, Zhi; Jin, Yunxue

2017-12-01

In this paper, ultrathin reduced graphene oxide films on nickel foam were fabricated via a facile dip-coating method combined with thermal reduction. Hierarchical Ni-Co layered double hydroxide nanosheets with network structure were electrodeposited on the ultrathin reduced graphene oxide films in a simple three-electrode system. The thickness of Ni-Co layered double hydroxide nanosheets can be controlled through adjusting the deposition temperature. The as-prepared electrode exhibited excellent electrochemical performance with specific capacitance of 1454.2 F g-1 at a current density of 1 A g-1. An asymmetric supercapacitor device was designed with the as-prepared composites as positive electrode material and Nitrogen-doped reduced graphene oxide as negative electrode material. This device could be operated in a working voltage range of 0-1.8 V in 1 M KOH aqueous electrolyte, delivering a high energy density of 56.4 W h kg-1 at a power density of 882.5 W kg-1. One supercapacitor can power two LEDs with rated voltage of 1.8-2.0 V. After 10,000 consecutive charge-discharge tests at 10 A g-1, this asymmetric supercapacitor revealed an excellent cycle life with 98.3% specific capacitance retention. These excellent electrochemical performances make it become one of most promising candidates for high energy supercapacitor device.

Molten salt synthesis of nitrogen and oxygen enriched hierarchically porous carbons derived from biomass via rapid microwave carbonization for high voltage supercapacitors

NASA Astrophysics Data System (ADS)

Cheng, Yinfeng; Li, Baoqiang; Huang, Yanjuan; Wang, Yaming; Chen, Junchen; Wei, Daqing; Feng, Yujie; Jia, Dechang; Zhou, Yu

2018-05-01

Nitrogen and oxygen enriched hierarchically porous carbons (NOHPCs) derived from biomass have been successfully prepared by rapid microwave carbonization coupled with molten salt synthesis method in only 4 min. ZnCl2 plays important roles as microwave absorber, chemical activation agent and porogen in this process. NOHPC-1:10 sample possesses the maximum specific surface area of 1899 m2 g-1 with a pore volume of 1.16 cm3 g-1 and mesopore ratio of 70%, as well as nitrogen content of 5.30 wt% and oxygen content of 14.12 wt%. When evaluated as an electrode in a three-electrode system with 6 M KOH electrolyte, the material exhibits a high specific capacitance of 276 F g-1 at 0.2 A g-1, with a good rate capability of 90.9% retention at 10 A g-1. More importantly, the symmetric supercapacitor based on NOHPC-1:10 in 1 M Na2SO4 electrolyte exhibits a high energy density of 13.9 Wh kg-1 at a power density of 120 W kg-1 in a wide voltage window of 0-1.6 V, an excellent cycling stability with 95% of capacitance retention after 10,000 cycles. Our strategy provides a facile and rapid way for the preparation of advanced carbon materials derived from biomass towards energy storage applications.

Neuron Morphology Influences Axon Initial Segment Plasticity.

PubMed

Gulledge, Allan T; Bravo, Jaime J

2016-01-01

In most vertebrate neurons, action potentials are initiated in the axon initial segment (AIS), a specialized region of the axon containing a high density of voltage-gated sodium and potassium channels. It has recently been proposed that neurons use plasticity of AIS length and/or location to regulate their intrinsic excitability. Here we quantify the impact of neuron morphology on AIS plasticity using computational models of simplified and realistic somatodendritic morphologies. In small neurons (e.g., dentate granule neurons), excitability was highest when the AIS was of intermediate length and located adjacent to the soma. Conversely, neurons having larger dendritic trees (e.g., pyramidal neurons) were most excitable when the AIS was longer and/or located away from the soma. For any given somatodendritic morphology, increasing dendritic membrane capacitance and/or conductance favored a longer and more distally located AIS. Overall, changes to AIS length, with corresponding changes in total sodium conductance, were far more effective in regulating neuron excitability than were changes in AIS location, while dendritic capacitance had a larger impact on AIS performance than did dendritic conductance. The somatodendritic influence on AIS performance reflects modest soma-to-AIS voltage attenuation combined with neuron size-dependent changes in AIS input resistance, effective membrane time constant, and isolation from somatodendritic capacitance. We conclude that the impact of AIS plasticity on neuron excitability will depend largely on somatodendritic morphology, and that, in some neurons, a shorter or more distally located AIS may promote, rather than limit, action potential generation.

Enhancement of two dimensional electron gas concentrations due to Si{sub 3}N{sub 4} passivation on Al{sub 0.3}Ga{sub 0.7}N/GaN heterostructure: strain and interface capacitance analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dinara, Syed Mukulika, E-mail: smdinara.iit@gmail.com; Jana, Sanjay Kr.; Ghosh, Saptarsi

2015-04-15

Enhancement of two dimensional electron gas (2DEG) concentrations at Al{sub 0.3}Ga{sub 0.7}N/GaN hetero interface after a-Si{sub 3}N{sub 4} (SiN) passivation has been investigated from non-destructive High Resolution X-ray Diffraction (HRXRD) analysis, depletion depth and capacitance-voltage (C-V) profile measurement. The crystalline quality and strained in-plane lattice parameters of Al{sub 0.3}Ga{sub 0.7}N and GaN were evaluated from double axis (002) symmetric (ω-2θ) diffraction scan and double axis (105) asymmetric reciprocal space mapping (DA RSM) which revealed that the tensile strain of the Al{sub 0.3}Ga{sub 0.7}N layer increased by 15.6% after SiN passivation. In accordance with the predictions from theoretical solution of Schrödinger-Poisson’smore » equations, both electrochemical capacitance voltage (ECV) depletion depth profile and C-V characteristics analyses were performed which implied effective 9.5% increase in 2DEG carrier density after passivation. The enhancement of polarization charges results from increased tensile strain in the Al{sub 0.3}Ga{sub 0.7}N layer and also due to the decreased surface states at the interface of SiN/Al{sub 0.3}Ga{sub 0.7}N layer, effectively improving the carrier confinement at the interface.« less

Neuron Morphology Influences Axon Initial Segment Plasticity123

PubMed Central

2016-01-01

In most vertebrate neurons, action potentials are initiated in the axon initial segment (AIS), a specialized region of the axon containing a high density of voltage-gated sodium and potassium channels. It has recently been proposed that neurons use plasticity of AIS length and/or location to regulate their intrinsic excitability. Here we quantify the impact of neuron morphology on AIS plasticity using computational models of simplified and realistic somatodendritic morphologies. In small neurons (e.g., dentate granule neurons), excitability was highest when the AIS was of intermediate length and located adjacent to the soma. Conversely, neurons having larger dendritic trees (e.g., pyramidal neurons) were most excitable when the AIS was longer and/or located away from the soma. For any given somatodendritic morphology, increasing dendritic membrane capacitance and/or conductance favored a longer and more distally located AIS. Overall, changes to AIS length, with corresponding changes in total sodium conductance, were far more effective in regulating neuron excitability than were changes in AIS location, while dendritic capacitance had a larger impact on AIS performance than did dendritic conductance. The somatodendritic influence on AIS performance reflects modest soma-to-AIS voltage attenuation combined with neuron size-dependent changes in AIS input resistance, effective membrane time constant, and isolation from somatodendritic capacitance. We conclude that the impact of AIS plasticity on neuron excitability will depend largely on somatodendritic morphology, and that, in some neurons, a shorter or more distally located AIS may promote, rather than limit, action potential generation. PMID:27022619

The low threshold voltage n-type silicon transistors based on a polymer/silica nanocomposite gate dielectric: The effect of annealing temperatures on their operation

NASA Astrophysics Data System (ADS)

Hashemi, Adeleh; Bahari, Ali; Ghasemi, Shahram

2017-09-01

In this work, povidone/silica nanocomposite dielectric layers were deposited on the n-type Si (100) substrates for application in n-type silicon field-effect transistors (FET). Thermogravimetric analysis (TGA) indicated that strong chemical interactions between polymer and silica nanoparticles were created. In order to examine the effect of annealing temperatures on chemical interactions and nanostructure properties, annealing process was done at 423-513 K. Atomic force microscopy (AFM) images show the very smooth surfaces with very low surface roughness (0.038-0.088 nm). The Si2p and C1s core level photoemission spectra were deconvoluted to the chemical environments of Si and C atoms respectively. The obtained results of deconvoluted X-ray photoelectron spectroscopy (XPS) spectra revealed a high percentage of silanol hydrogen bonds in the sample which was not annealed. These bonds were inversed to stronger covalence bonds (siloxan bonds) at annealing temperature of 423 K. By further addition of temperature, siloxan bonds were shifted to lower binding energy of about 1 eV and their intensity were abated at annealing temperature of 513 K. The electrical characteristics were extracted from current-Voltage (I-V) and capacitance-voltage (C-V) measurements in metal-insulator-semiconductor (MIS) structure. The all n-type Si transistors showed very low threshold voltages (-0.24 to 1 V). The formation of the strongest cross-linking at nanostructure of dielectric film annealed at 423 K caused resulted in an un-trapped path for the transport of charge carriers yielding the lowest threshold voltage (0.08 V) and the highest electron mobility (45.01 cm2/V s) for its FET. By increasing the annealing temperature (473 and 513 K) on the nanocomposite dielectric films, the values of the average surface roughness, the capacitance and the FET threshold voltage increased and the value of FET electron field-effect mobility decreased.

Growth and interface properties of Au Schottky contact on ZnO grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Asghar, M.; Mahmood, K.; Malik, Faisal; Hasan, M. A.

2013-06-01

In this paper, we have discussed the growth of ZnO by molecular beam epitaxy (MBE) and interface properties of Au Schottky contacts on grown sample. After the verification of structure and surface properties by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM), respectively, Au metal contact was fabricated by e-beam evaporation to study contact properties. The high value of ideality factor (2.15) and barrier height (0.61 eV) at room temperature obtained by current-voltage (I-V) characteristics suggested the presence of interface states between metal and semiconductor. To confirm this observation we carried out frequency dependent capacitance-voltage (C-V) and conductance-voltage (G-V) demonstrated that the capacitance of diode decreased with increasing frequency. The reason of this behavior is related with density of interface states, series resistance and image force lowering. The C-2-V plot drawn to calculate the carrier concentration and barrier height with values 1.4×1016 cm-3 and 0.92 eV respectively. Again, high value of barrier height obtained from C-V as compared to the value obtained from I-V measurements revealed the presence of interface states. The density of these interface states (Dit) was calculated by well known Hill-Coleman method. The calculated value of Dit at 1 MHz frequency was 2×1012 eV-1 cm-2. The plot between interface states and frequency was also drawn which demonstrated that density of interface states had inverse proportion with measuring frequency.

Bimodal wireless sensing with dual-channel wide bandgap heterostructure varactors

NASA Astrophysics Data System (ADS)

Deen, David A.; Osinsky, Andrei; Miller, Ross

2014-03-01

A capacitive wireless sensing scheme is developed that utilizes an AlN/GaN-based dual-channel varactor. The dual-channel heterostructure affords two capacitance plateaus within the capacitance-voltage (CV) characteristic, owing to the two parallel two-dimensional electron gases (2DEGs) located at respective AlN/GaN interfaces. The capacitance plateaus are leveraged for the definition of two resonant states of the sensor when implemented in an inductively-coupled resonant LRC network for wireless readout. The physics-based CV model is compared with published experimental results, which serve as a basis for the sensor embodiment. The bimodal resonant sensor is befitting for a broad application space ranging from gas, electrostatic, and piezoelectric sensors to biological and chemical detection.

Performance improvements of the vertical, double-diffused power metal-oxide-silicon field-effect transistor

NASA Astrophysics Data System (ADS)

Zhu, Ronghua

An n-channel power vertical double-diffused metal-oxide-silicon field-effect transistor (VDMOSFET) with a new atomic-lattice-layout (ALL) has been designed and fabricated. The performance of the VDMOSFET with the ALL has been studied experimentally and comprehensively for the first time. The experimental results with the ALL are compared with the square (SQ), hexagonal (HEX) and stripe (STR) layouts for different applications. For high-frequency applications of VDMOSFET, the ALL is superior to the HEX and inferior to the STR. The optimum specific on-resistance and input capacitance product (Rsb{ON,SP} × Csb{iss,SP}) and optimum specific on-resistance and output capacitance product (Rsb{ON,SP} × Csb{oss,SP}) for the ALL are 44% and 36% lower than the HEX, and 10% and 13% higher than the STR, respectively. The ALL offers superior performance compared to the SQ for applications involving smart power feedback control using integrated current sensor. For a typical sense resistance of 100 Omega, the sense current drops 44% of its value at 0 Omega for the SQ, but only 11% for the ALL. For high-voltage and high-current applications, such as voltage-controlled current source, one observes that the ALL enters into quasi-saturation region at lower gate voltage (Vsb{G}). Typically, quasi-saturation occurs at Vsb{G} of 3V above the threshold voltage (Vsb{T}) for ALL, whereas this voltage is 5 and 6V for the STR and HEX, respectively. Minority carrier lifetime control by proton implantation has been successfully employed to improve the VDMOSFET built-in diode switching performance for the first time. A sevenfold reduction in reverse recovery charge has been achieved with a proton energy of 2.5 MeV and dose of 3 × 10sp{11}/cmsp2. The impact of proton implantation on diode forward voltage and the VDMOSFET characteristics, such as Vsb{T}, leakage current and on-resistance, has been found negligible. Proton implantation has also been found to significantly improve the device ruggedness. The peak reverse current of the built-in diode is reduced to 17.6 A for a proton energy of 1.5 MeV compared to 29.1 A for an un-implanted device at di/dt = 450 A/mus. The optimum location of the proton has been found at approximately middle of the epi-layer.

A compact high-voltage pulse generator based on pulse transformer with closed magnetic core.

PubMed

Zhang, Yu; Liu, Jinliang; Cheng, Xinbing; Bai, Guoqiang; Zhang, Hongbo; Feng, Jiahuai; Liang, Bo

2010-03-01

A compact high-voltage nanosecond pulse generator, based on a pulse transformer with a closed magnetic core, is presented in this paper. The pulse generator consists of a miniaturized pulse transformer, a curled parallel strip pulse forming line (PFL), a spark gap, and a matched load. The innovative design is characterized by the compact structure of the transformer and the curled strip PFL. A new structure of transformer windings was designed to keep good insulation and decrease distributed capacitance between turns of windings. A three-copper-strip structure was adopted to avoid asymmetric coupling of the curled strip PFL. When the 31 microF primary capacitor is charged to 2 kV, the pulse transformer can charge the PFL to 165 kV, and the 3.5 ohm matched load can deliver a high-voltage pulse with a duration of 9 ns, amplitude of 84 kV, and rise time of 5.1 ns. When the load is changed to 50 ohms, the output peak voltage of the generator can be 165 kV, the full width at half maximum is 68 ns, and the rise time is 6.5 ns.

Supercapacitors based on pillared graphene nanostructures.

PubMed

Lin, Jian; Zhong, Jiebin; Bao, Duoduo; Reiber-Kyle, Jennifer; Wang, Wei; Vullev, Valentine; Ozkan, Mihrimah; Ozkan, Cengiz S

2012-03-01

We describe the fabrication of highly conductive and large-area three dimensional pillared graphene nanostructure (PGN) films from assembly of vertically aligned CNT pillars on flexible copper foils for applications in electric double layer capacitors (EDLC). The PGN films synthesized via a one-step chemical vapor deposition process on flexible copper foils exhibit high conductivity with sheet resistance as low as 1.6 ohms per square and possessing high mechanical flexibility. Raman spectroscopy indicates the presence of multi walled carbon nanotubes (MWCNT) and their morphology can be controlled by the growth conditions. It was discovered that nitric acid treatment can significantly increase the specific capacitance of the devices. EDLC devices based on PGN electrodes (surface area of 565 m2/g) demonstrate enhanced performance with specific capacitance value as high as 330 F/g extracted from the current density-voltage (CV) measurements and energy density value of 45.8 Wh/kg. The hybrid graphene-CNT nanostructures are attractive for applications including supercapacitors, fuel cells and batteries.

Flute type micropores activated carbon from cotton stalk for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Tian, Xun; Ma, Hongru; Li, Zhe; Yan, Shaocun; Ma, Lei; Yu, Feng; Wang, Gang; Guo, Xuhong; Ma, Yanqing; Wong, Chingping

2017-08-01

Flute type micropores activated carbon (FTMAC) has been successfully obtained from cotton stalk via KOH-chemical activation method. The synthesized carbon material exhibits an ordered pore structure with high specific surface area of 1964.46 m2 g-1 and pore volume of 1.03 m3 g-1. The assembled FTMAC-based electrode delivers a high specific capacitance of 254 F g-1 at a current density of 0.2 A g-1 in 1 M H2SO4 aqueous electrolyte. It still can maintain 221 F g-1at a current density of 10 A g-1, demonstrating a good rate capacity (87% retention), as well as long cyclic stability of 96% capacitance retention after 10000 charging and discharging cycles at current density of 1 A g-1. Moreover, the symmetric supercapacitor can deliver a high energy density of 18.14 W h kg-1 and a power density of 450.37 W kg-1 which is operated in the voltage range of 0-1.8 V.

Relevance of GaAs(001) surface electronic structure for high frequency dispersion on n-type accumulation capacitance

NASA Astrophysics Data System (ADS)

Pi, T. W.; Chen, W. S.; Lin, Y. H.; Cheng, Y. T.; Wei, G. J.; Lin, K. Y.; Cheng, C.-P.; Kwo, J.; Hong, M.

2017-01-01

This study investigates the origin of long-puzzled high frequency dispersion on the accumulation region of capacitance-voltage characteristics in an n-type GaAs-based metal-oxide-semiconductor. Probed adatoms with a high Pauling electronegativity, Ag and Au, unexpectedly donate charge to the contacted As/Ga atoms of as-grown α2 GaAs(001)-2 × 4 surfaces. The GaAs surface atoms behave as charge acceptors, and if not properly passivated, they would trap those electrons accumulated at the oxide and semiconductor interface under a positive bias. The exemplified core-level spectra of the Al2O3/n-GaAs(001)-2 × 4 and the Al2O3/n-GaAs(001)-4 × 6 interfaces exhibit remnant of pristine surface As emission, thereby causing high frequency dispersion in the accumulation region. For the p-type GaAs, electrons under a negatively biased condition are expelled from the interface, thereby avoiding becoming trapped.

Voltage-dependent K+ channels improve the energy efficiency of signalling in blowfly photoreceptors

PubMed Central

2017-01-01

Voltage-dependent conductances in many spiking neurons are tuned to reduce action potential energy consumption, so improving the energy efficiency of spike coding. However, the contribution of voltage-dependent conductances to the energy efficiency of analogue coding, by graded potentials in dendrites and non-spiking neurons, remains unclear. We investigate the contribution of voltage-dependent conductances to the energy efficiency of analogue coding by modelling blowfly R1-6 photoreceptor membrane. Two voltage-dependent delayed rectifier K+ conductances (DRs) shape the membrane's voltage response and contribute to light adaptation. They make two types of energy saving. By reducing membrane resistance upon depolarization they convert the cheap, low bandwidth membrane needed in dim light to the expensive high bandwidth membrane needed in bright light. This investment of energy in bandwidth according to functional requirements can halve daily energy consumption. Second, DRs produce negative feedback that reduces membrane impedance and increases bandwidth. This negative feedback allows an active membrane with DRs to consume at least 30% less energy than a passive membrane with the same capacitance and bandwidth. Voltage-dependent conductances in other non-spiking neurons, and in dendrites, might be organized to make similar savings. PMID:28381642

Voltage-dependent K+ channels improve the energy efficiency of signalling in blowfly photoreceptors.

PubMed

Heras, Francisco J H; Anderson, John; Laughlin, Simon B; Niven, Jeremy E

2017-04-01

Voltage-dependent conductances in many spiking neurons are tuned to reduce action potential energy consumption, so improving the energy efficiency of spike coding. However, the contribution of voltage-dependent conductances to the energy efficiency of analogue coding, by graded potentials in dendrites and non-spiking neurons, remains unclear. We investigate the contribution of voltage-dependent conductances to the energy efficiency of analogue coding by modelling blowfly R1-6 photoreceptor membrane. Two voltage-dependent delayed rectifier K + conductances (DRs) shape the membrane's voltage response and contribute to light adaptation. They make two types of energy saving. By reducing membrane resistance upon depolarization they convert the cheap, low bandwidth membrane needed in dim light to the expensive high bandwidth membrane needed in bright light. This investment of energy in bandwidth according to functional requirements can halve daily energy consumption. Second, DRs produce negative feedback that reduces membrane impedance and increases bandwidth. This negative feedback allows an active membrane with DRs to consume at least 30% less energy than a passive membrane with the same capacitance and bandwidth. Voltage-dependent conductances in other non-spiking neurons, and in dendrites, might be organized to make similar savings. © 2017 The Author(s).

Cryogenic lifetime tests on a commercial epoxy resin high voltage bushing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwenterly, S W; Pleva, Ed; Ha, Tam T

2012-06-12

High-temperature superconducting (HTS) power devices operating in liquid nitrogen frequently require high-voltage bushings to carry the current leads from the superconducting windings to the room temperature grid connections. Oak Ridge National Laboratory is collaborating with Waukesha Electric Systems, SuperPower, and Southern California Edison to develop and demonstrate an HTS utility power transformer. Previous dielectric high voltage tests in support of this program have been carried out in test cryostats with commercial epoxy resin bushings from Electro Composites Inc. (ECI). Though the bushings performed well in these short-term tests, their long-term operation at high voltage in liquid nitrogen needs to bemore » verified for use on the utility grid. Long-term tests are being carried out on a sample 28-kV-class ECI bushing. The bushing has a monolithic cast, cycloaliphatic resin body and is fire- and shatter-resistant. The test cryostat is located in an interlocked cage and is energized at 25 kVac around the clock. Liquid nitrogen (LN) is automatically refilled every 9.5 hours. Partial discharge, capacitance, and leakage resistance tests are periodically performed to check for deviations from factory values. At present, over 2400 hours have been accumulated with no changes in these parameters. The tests are scheduled to run for four to six months.« less

Cryogenic lifetime tests on a commercial epoxy resin high voltage bushing

NASA Astrophysics Data System (ADS)

Schwenterly, S. W.; Pleva, E. F.; Ha, T. T.

2012-06-01

High-temperature superconducting (HTS) power devices operating in liquid nitrogen frequently require high-voltage bushings to carry the current leads from the superconducting windings to the room temperature grid connections. Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES), SuperPower (SP), and Southern California Edison (SCE) to develop and demonstrate an HTS utility power transformer. Previous dielectric high voltage tests in support of this program have been carried out in test cryostats with commercial epoxy resin bushings from Electro Composites Inc. (ECI). Though the bushings performed well in these short-term tests, their long-term operation at high voltage in liquid nitrogen (LN) needs to be verified for use on the utility grid. Long-term tests are being carried out on a sample 28-kV-rms-class ECI bushing. The bushing has a monolithic cast, cycloaliphatic resin body and is fire- and shatter-resistant. The test cryostat is located in an interlocked cage and is continuously energized at 25 kVac rms. LN is automatically refilled every 9.5 hours. Partial discharge, capacitance, and leakage resistance tests are periodically performed to check for deviations from factory values. At present, over 2400 hours have been accumulated with no changes in these parameters. The tests are scheduled to run for four to six months.

Mitigating voltage lead errors of an AC Josephson voltage standard by impedance matching

NASA Astrophysics Data System (ADS)

Zhao, Dongsheng; van den Brom, Helko E.; Houtzager, Ernest

2017-09-01

A pulse-driven AC Josephson voltage standard (ACJVS) generates calculable AC voltage signals at low temperatures, whereas measurements are performed with a device under test (DUT) at room temperature. The voltage leads cause the output voltage to show deviations that scale with the frequency squared. Error correction mechanisms investigated so far allow the ACJVS to be operational for frequencies up to 100 kHz. In this paper, calculations are presented to deal with these errors in terms of reflected waves. Impedance matching at the source side of the system, which is loaded with a high-impedance DUT, is proposed as an accurate method to mitigate these errors for frequencies up to 1 MHz. Simulations show that the influence of non-ideal component characteristics, such as the tolerance of the matching resistor, the capacitance of the load input impedance, losses in the voltage leads, non-homogeneity in the voltage leads, a non-ideal on-chip connection and inductors between the Josephson junction array and the voltage leads, can be corrected for using the proposed procedures. The results show that an expanded uncertainty of 12 parts in 106 (k  =  2) at 1 MHz and 0.5 part in 106 (k  =  2) at 100 kHz is within reach.

A rationally designed self-standing V2O5 electrode for high voltage non-aqueous all-solid-state symmetric (2.0 V) and asymmetric (2.8 V) supercapacitors.

PubMed

Ghosh, Meena; Vijayakumar, Vidyanand; Soni, Roby; Kurungot, Sreekumar

2018-05-10

The maximum capacitive potential window of certain pseudocapacitive materials cannot be accessed in aqueous electrolytes owing to the low dissociation potential of 1.2 V possessed by water molecules. However, the inferior pseudocapacitance exhibited by the commonly used electrode materials when integrated with non-aqueous electrolytes still remains a challenge in the development of supercapacitors (SC). Proper selection of materials for the electrode and a rational design process are indeed important to overcome these practical intricacies so that such systems can perform well with non-aqueous electrolytes. We address this challenge by fabricating a prototype all-solid-state device designed with high-capacitive V2O5 as the electrode material along with a Li-ion conducting organic electrolyte. V2O5 is synthesized on a pre-treated carbon-fibre paper by adopting an electrochemical deposition technique that effects an improved contact resistance. A judicious electrode preparation strategy makes it possible to overcome the constraints of the low ionic and electrical conductivities imposed by the electrolyte and electrode material, respectively. The device, assembled in a symmetrical fashion, achieves a high specific capacitance of 406 F g-1 (at 1 A g-1). The profitable aspect of using an organic electrolyte is also demonstrated with an asymmetric configuration by using activated carbon as the positive and V2O5 as the negative electrode materials, respectively. The asymmetric device displays a wide working-voltage window of 2.8 V and delivers a high energy density of 102.68 W h kg-1 at a power density of 1.49 kW kg-1. Moreover, the low equivalent series resistance of 9.9 Ω and negligible charge transfer resistance are observed in the impedance spectra, which is a key factor that accounts for such an exemplary performance.

Constructing Ultrahigh-Capacity Zinc-Nickel-Cobalt Oxide@Ni(OH)2 Core-Shell Nanowire Arrays for High-Performance Coaxial Fiber-Shaped Asymmetric Supercapacitors.

PubMed

Zhang, Qichong; Xu, Weiwei; Sun, Juan; Pan, Zhenghui; Zhao, Jingxin; Wang, Xiaona; Zhang, Jun; Man, Ping; Guo, Jiabin; Zhou, Zhenyu; He, Bing; Zhang, Zengxing; Li, Qingwen; Zhang, Yuegang; Xu, Lai; Yao, Yagang

2017-12-13

Increased efforts have recently been devoted to developing high-energy-density flexible supercapacitors for their practical applications in portable and wearable electronics. Although high operating voltages have been achieved in fiber-shaped asymmetric supercapacitors (FASCs), low specific capacitance still restricts the further enhancement of their energy density. This article specifies a facile and cost-effective method to directly grow three-dimensionally well-aligned zinc-nickel-cobalt oxide (ZNCO)@Ni(OH) 2 nanowire arrays (NWAs) on a carbon nanotube fiber (CNTF) with an ultrahigh specific capacitance of 2847.5 F/cm 3 (10.678 F/cm 2 ) at a current density of 1 mA/cm 2 , These levels are approximately five times higher than those of ZNCO NWAs/CNTF electrodes (2.10 F/cm 2 ) and four times higher than Ni(OH) 2 /CNTF electrodes (2.55 F/cm 2 ). Benefiting from their unique features, we successfully fabricated a prototype coaxial FASC (CFASC) with a maximum operating voltage of 1.6 V, which was assembled by adopting ZNCO@Ni(OH) 2 NWAs/CNTF as the core electrode and a thin layer of carbon coated vanadium nitride (VN@C) NWAs on a carbon nanotube strip (CNTS) as the outer electrode with KOH poly(vinyl alcohol) (PVA) as the gel electrolyte. A high specific capacitance of 94.67 F/cm 3 (573.75 mF/cm 2 ) and an exceptional energy density of 33.66 mWh/cm 3 (204.02 μWh/cm 2 ) were achieved for our CFASC device, which represent the highest levels of fiber-shaped supercapacitors to date. More importantly, the fiber-shaped ZnO-based photodetector is powered by the integrated CFASC, and it demonstrates excellent sensitivity in detecting UV light. Thus, this work paves the way to the construction of ultrahigh-capacity electrode materials for next-generation wearable energy-storage devices.

The rod-driven a-wave of the dark-adapted mammalian electroretinogram.

PubMed

Robson, John G; Frishman, Laura J

2014-03-01

The a-wave of the electroretinogram (ERG) reflects the response of photoreceptors to light, but what determines the exact waveform of the recorded voltage is not entirely understood. We have now simulated the trans-retinal voltage generated by the photocurrent of dark-adapted mammalian rods, using an electrical model based on the in vitro measurements of Hagins et al. (1970) and Arden (1976) in rat retinas. Our simulations indicate that in addition to the voltage produced by extracellular flow of photocurrent from rod outer to inner segments, a substantial fraction of the recorded a-wave is generated by current that flows in the outer nuclear layer (ONL) to hyperpolarize the rod axon and synaptic terminal. This current includes a transient capacitive component that contributes an initial negative "nose" to the trans-retinal voltage when the stimulus is strong. Recordings in various species of the a-wave, including the peak and initial recovery towards the baseline, are consistent with simulations showing an initial transient primarily related to capacitive currents in the ONL. Existence of these capacitive currents can explain why there is always a substantial residual transient a-wave when post-receptoral responses are pharmacologically inactivated in rodents and nonhuman primates, or severely genetically compromised in humans (e.g. complete congenital stationary night blindness) and nob mice. Our simulations and analysis of ERGs indicate that the timing of the leading edge and peak of dark-adapted a-waves evoked by strong stimuli could be used in a simple way to estimate rod sensitivity. Copyright © 2013 Elsevier Ltd. All rights reserved.

Determination of charge transfer resistance and capacitance of microbial fuel cell through a transient response analysis of cell voltage.

PubMed

Ha, Phuc Thi; Moon, Hyunsoo; Kim, Byung Hong; Ng, How Yong; Chang, In Seop

2010-03-15

An alternative method for determining the charge transfer resistance and double-layer capacitance of microbial fuel cells (MFCs), easily implemented without a potentiostat, was developed. A dynamic model with two parameters, the charge transfer resistance and double-layer capacitance of electrodes, was derived from a linear differential equation to depict the current generation with respect to activation overvoltage. This model was then used to fit the transient cell voltage response to the current step change during the continuous operation of a flat-plate type MFC fed with acetate. Variations of the charge transfer resistance and the capacitance value with respect to the MFC design conditions (biocatalyst existence and electrode area) and operating parameters (acetate concentration and buffer strength in the catholyte) were then determined to elucidate the validity of the proposed method. This model was able to describe the dynamic behavior of the MFC during current change in the activation loss region; having an R(2) value of over 0.99 in most tests. Variations of the charge transfer resistance value (thousands of Omega) according to the change of the design factors and operational factors were well-correlated with the corresponding MFC performances. However, though the capacitance values (approximately 0.02 F) reflected the expected trend according to the electrode area change and catalyst property, they did not show significant variation with changes in either the acetate concentration or buffer strength. (c) 2009 Elsevier B.V. All rights reserved.

Hexagonal VS2 Anchored MWCNTs: First Approach to Design Flexible Solid-State Symmetric Supercapacitor Device.

PubMed

Pandit, Bidhan; Karade, Swapnil S; Sankapal, Babasaheb R

2017-12-27

Transition metal chalcogenides (TMCs) embedded with a carbon network are gaining much attention because of their high power capability, which can be easily integrated to portable electronic devices. Facile chemical route has been explored to synthesize hexagonal structured VS 2 nanoparticles onto multiwalled carbon nanotubes (MWCNTs) matrix. Such surface-modified VS 2 /MWCNTs electrode has boosted the electrochemical performance to reach high capacitance to 830 F/g and excellent stability to 95.9% over 10 000 cycles. Designed flexible solid-state symmetric supercapacitor device (FSSD) with a wide voltage window of 1.6 V exhibited maximum gain in specific capacitance value of 182 F/g at scan rate of 2 mV/s along with specific energy of 42 Wh/kg and a superb stability of 93.2% over 5000 cycles. As a practical approach, FSSD has lightened up "VNIT" panel consisting of 21 red LEDs.

Three-dimensional ordered macroporous MnO2/carbon nanocomposites as high-performance electrodes for asymmetric supercapacitors.

PubMed

Yang, Chunzhen; Zhou, Ming; Xu, Qian

2013-12-07

MnO2/carbon composites with ultrathin MnO2 nanofibers (diameter of 5-10 nm) uniformly deposited on three dimensional ordered macroporous (3DOM) carbon frameworks were fabricated via a self-limiting redox process. The MnO2 nanofibers provide a large surface area for charge storage, whereas the 3DOM carbon serves as a desirable supporting material providing rapid ion and electron transport through the composite electrodes. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) were used to characterize the capacitive performance of these composites. Optimization of the composition results in a composite with 57 wt% MnO2 content, which gives both a high specific capacitance (234 F g(-1) at a discharge current of 0.1 A g(-1)) and good rate capability (52% retention of the capacitance at 5 A g(-1)). An asymmetric supercapacitor was fabricated by assembling the optimized MnO2/carbon composite as the positive electrode and 3DOM carbon as the negative electrode. The asymmetric supercapacitor exhibits superior electrochemical performances, which can be reversibly charged and discharged at a maximum cell voltage of 2.0 V in 1.0 M Na2SO4 aqueous electrolyte, delivering both high energy density (30.2 W h kg(-1)) and power density (14.5 kW kg(-1)). Additionally, the asymmetric supercapacitor exhibits an excellent cycle life, with 95% capacitance retained after 1000 cycles.