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.

Impact of time-dependent annealing on TiO2 films for CMOS application

NASA Astrophysics Data System (ADS)

Gyanan, Mondal, Sandip; Kumar, Arvind

2017-05-01

Post-deposition annealing (PDA) is the inherent part of sol-gel fabrication process to achieve the optimum device performance, especially in CMOS applications. The annealing removes the oxygen vacancies and improves the structural order of dielectric films. The process also reduces the interface related defects and improves the interfacial properties. In this work, we have integrated the sol-gel spin-coating deposited high-κ TiO2 films in MOS. The films are fired at 400°C for the duration of 20, 40, 60 and 80 min. The thicknesses of the films were found to be of ˜ 30 nm using ellipsometry. The (Al/TiO2/p-Si) devices were examined with current-voltage (I-V) and capacitance-voltage (C-V) at room temperature to understand the influence of firing time. The C-V and I-V characteristic showed a significant dependence on annealing time such as variation in dielectric constant and leakage current. 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 4.25nm, respectively with a low leakage current density (1.09 × 10-6 A/cm2) fired for 80 min at +1 V.

Investigation of low leakage current radiation detectors on n-type 4H-SiC epitaxial layers

NASA Astrophysics Data System (ADS)

Nguyen, Khai V.; Chaudhuri, Sandeep K.; Mandal, Krishna C.

2014-09-01

The surface leakage current of high-resolution 4H-SiC epitaxial layer Schottky barrier detectors has been improved significantly after surface passivations of 4H-SiC epitaxial layers. Thin (nanometer range) layers of silicon dioxide (SiO2) and silicon nitride (Si3N4) were deposited on 4H-SiC epitaxial layers using plasma enhanced chemical vapor deposition (PECVD) on 20 μm thick n-type 4H-SiC epitaxial layers followed by the fabrication of large area (~12 mm2) Schottky barrier radiation detectors. The fabricated detectors have been characterized through current-voltage (I-V), capacitance-voltage (C-V), and alpha pulse height spectroscopy measurements; the results were compared with that of detectors fabricated without surface passivations. Improved energy resolution of ~ 0.4% for 5486 keV alpha particles was observed after passivation, and it was found that the performance of these detectors were limited by the presence of macroscopic and microscopic crystal defects affecting the charge transport properties adversely. Capacitance mode deep level transient studies (DLTS) revealed the presence of a titanium impurity related shallow level defects (Ec-0.19 eV), and two deep level defects identified as Z1/2 and Ci1 located at Ec-0.62 and ~ Ec-1.40 eV respectively.

Switched integration amplifier-based photocurrent meter for accurate spectral responsivity measurement of photometers.

PubMed

Park, Seongchong; Hong, Kee-Suk; Kim, Wan-Seop

2016-03-20

This work introduces a switched integration amplifier (SIA)-based photocurrent meter for femtoampere (fA)-level current measurement, which enables us to measure a 10⁷ dynamic range of spectral responsivity of photometers even with a common lamp-based monochromatic light source. We described design considerations and practices about operational amplifiers (op-amps), switches, readout methods, etc., to compose a stable SIA of low offset current in terms of leakage current and gain peaking in detail. According to the design, we made six SIAs of different integration capacitance and different op-amps and evaluated their offset currents. They showed an offset current of (1.5-85) fA with a slow variation of (0.5-10) fA for an hour under opened input. Applying a detector to the SIA input, the offset current and its variation were increased and the SIA readout became noisier due to finite shunt resistance and nonzero shunt capacitance of the detector. One of the SIAs with 10 pF nominal capacitance was calibrated using a calibrated current source at the current level of 10 nA to 1 fA and at the integration time of 2 to 65,536 ms. As a result, we obtained a calibration formula for integration capacitance as a function of integration time rather than a single capacitance value because the SIA readout showed a distinct dependence on integration time at a given current level. Finally, we applied it to spectral responsivity measurement of a photometer. It is demonstrated that the home-made SIA of 10 pF was capable of measuring a 10⁷ dynamic range of spectral responsivity of a photometer.

The capacitive proximity sensor based on transients in RC-circuits

NASA Astrophysics Data System (ADS)

Yakunin, A. G.

2018-05-01

The principle of operation of the capacitive proximity sensor is described. It can be used in various robotic complexes, automation systems and alarm devices to inform the control device of the approach to the sensor sensitive surface of an object. At the heart of the device is the measurement of the change in the current of the transient accompanying the charge of the reference capacitor because of the parallel connection to it the capacitance formed by the sensitive sensor surface and the external object. At the heart of the device is the measurement of the change in the current of the transient accompanying the charge of the reference capacitor caused by the parallel connection to it the capacitance formed by the sensitive sensor surface and the external object. As shown by theoretical and experimental studies, the value of this capacity, depending on the purpose of the device, can vary within very wide limits. In this case, the sensitive surface can be both a piece of ordinary wire several centimeters long, and a metall plate or grid, the area of which can reach units and even tens of square meters. The main advantage of the proposed solution is a significant reduction in the effect of spurious leakage currents arising at the capacitance of the measuring electrode under the influence of pollution and humidity of the environment.

Effects of Post-Deposition Annealing on ZrO2/n-GaN MOS Capacitors with H2O and O3 as the Oxidizers.

PubMed

Zheng, Meijuan; Zhang, Guozhen; Wang, Xiao; Wan, Jiaxian; Wu, Hao; Liu, Chang

2017-12-01

GaN-based metal-oxide-semiconductor capacitors with ZrO 2 as the dielectric layer have been prepared by atomic layer deposition. The accumulation and depletion regions can be clearly distinguished when the voltage was swept from -4 to 4 V. Post-annealing results suggested that the capacitance in accumulation region went up gradually as the annealing temperature increased from 300 to 500 °C. A minimum leakage current density of 3 × 10 -9  A/cm 2 at 1 V was obtained when O 3 was used for the growth of ZrO 2 . Leakage analysis revealed that Schottky emission and Fowler-Nordheim tunneling were the main leakage mechanisms.

Multichannel detection of ionic currents through two nanopores fabricated on integrated Si3N4 membranes.

PubMed

Yanagi, Itaru; Akahori, Rena; Aoki, Mayu; Harada, Kunio; Takeda, Ken-Ichi

2016-08-16

Integration of solid-state nanopores and multichannel detection of signals from each nanopore are effective measures for realizing high-throughput nanopore sensors. In the present study, we demonstrated fabrication of Si3N4 membrane arrays and the simultaneous measurement of ionic currents through two nanopores formed in two adjacent membranes. Membranes with thicknesses as low as 6.4 nm and small nanopores with diameters of less than 2 nm could be fabricated using the poly-Si sacrificial-layer process and multilevel pulse-voltage injection. Using the fabricated nanopore membranes, we successfully achieved simultaneous detection of clear ionic-current blockades when single-stranded short homopolymers (poly(dA)60) passed through two nanopores. In addition, we investigated the signal crosstalk and leakage current among separated chambers. When two nanopores were isolated on the front surface of the membrane, there was no signal crosstalk or leakage current between the chambers. However, when two nanopores were isolated on the backside of the Si substrate, signal crosstalk and leakage current were observed owing to high-capacitance coupling between the chambers and electrolysis of water on the surface of the Si substrate. The signal crosstalk and leakage current could be suppressed by oxidizing the exposed Si surface in the membrane chip. Finally, the observed ionic-current blockade when poly(dA)60 passed through the nanopore in the oxidized chip was approximately half of that observed in the non-oxidized chip.

FAST TRACK COMMUNICATION: Deposition temperature effect on electrical properties and interface of high-k ZrO2 capacitor

NASA Astrophysics Data System (ADS)

Kim, Joo-Hyung; Ignatova, Velislava A.; Heitmann, Johannes; Oberbeck, Lars

2008-09-01

The electrical characteristics, i.e. leakage current and capacitance, of ZrO2 based metal-insulator-metal structures, grown at 225, 250 and 275 °C by atomic layer deposition, were studied. The lowest leakage current was obtained at 250 °C deposition temperature, while the highest dielectric constant (k ~ 43) was measured for the samples grown at 275 °C, most probably due to the formation of tetragonal/cubic phases in the ZrO2 layer. We have shown that the main leakage current of these ZrO2 capacitors is governed by the Poole-Frenkel conduction mechanism. It was observed by x-ray photoelectron spectroscopy depth profiling that at 275 °C deposition temperature the oxygen content at and beyond the ZrO2/TiN interface is higher than at lower deposition temperatures, most probably due to oxygen inter-diffusion towards the electrode layer, forming a mixed TiN-TiOxNy interface layer. At and above 275 °C the ZrO2 layer changes its structure and becomes crystalline as proven by XRD analysis.

Pinhole mediated electrical transport across LaTiO3/SrTiO3 and LaAlO3/SrTiO3 oxide hetero-structures

NASA Astrophysics Data System (ADS)

Kumar, Pramod; Dogra, Anjana; Toutam, Vijaykumar

2013-11-01

Metal-insulator-metal configuration of LaTiO3/SrTiO3 and LaAlO3/SrTiO3 hetero-structures between two dimensional electron gas formed at the interface and different area top electrodes is employed for Conductive Atomic force microscopy (CAFM) imaging, Current-Voltage (I-V), and Capacitance-Voltage (C-V) spectroscopy. Electrode area dependent I-V characteristics are observed for these oxide hetero-structures. With small area electrodes, rectifying I-V characteristics are observed, compared to, both tunneling and leakage current characteristics for large area electrodes. CAFM mapping confirmed the presence of pinholes on both surfaces. Resultant I-V characteristics have a contribution from both tunneling and leakage due to pinholes.

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

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 Study of Electrical Properties for Multilayer La2O3/Al2O3 Dielectric Stacks and LaAlO3 Dielectric Film Deposited by ALD.

PubMed

Feng, Xing-Yao; Liu, Hong-Xia; Wang, Xing; Zhao, Lu; Fei, Chen-Xi; Liu, He-Lei

2017-12-01

The capacitance and leakage current properties of multilayer La 2 O 3 /Al 2 O 3 dielectric stacks and LaAlO 3 dielectric film are investigated in this paper. A clear promotion of capacitance properties is observed for multilayer La 2 O 3 /Al 2 O 3 stacks after post-deposition annealing (PDA) at 800 °C compared with PDA at 600 °C, which indicated the recombination of defects and dangling bonds performs better at the high-k/Si substrate interface for a higher annealing temperature. For LaAlO 3 dielectric film, compared with multilayer La 2 O 3 /Al 2 O 3 dielectric stacks, a clear promotion of trapped charges density (N ot ) and a degradation of interface trap density (D it ) can be obtained simultaneously. In addition, a significant improvement about leakage current property is observed for LaAlO 3 dielectric film compared with multilayer La 2 O 3 /Al 2 O 3 stacks at the same annealing condition. We also noticed that a better breakdown behavior for multilayer La 2 O 3 /Al 2 O 3 stack is achieved after annealing at a higher temperature for its less defects.

Estimation of Leakage Potential of Selected Sites in Interstate and Tri-State Canals Using Geostatistical Analysis of Selected Capacitively Coupled Resistivity Profiles, Western Nebraska, 2004

USGS Publications Warehouse

Vrabel, Joseph; Teeple, Andrew; Kress, Wade H.

2009-01-01

With increasing demands for reliable water supplies and availability estimates, groundwater flow models often are developed to enhance understanding of surface-water and groundwater systems. Specific hydraulic variables must be known or calibrated for the groundwater-flow model to accurately simulate current or future conditions. Surface geophysical surveys, along with selected test-hole information, can provide an integrated framework for quantifying hydrogeologic conditions within a defined area. In 2004, the U.S. Geological Survey, in cooperation with the North Platte Natural Resources District, performed a surface geophysical survey using a capacitively coupled resistivity technique to map the lithology within the top 8 meters of the near-surface for 110 kilometers of the Interstate and Tri-State Canals in western Nebraska and eastern Wyoming. Assuming that leakage between the surface-water and groundwater systems is affected primarily by the sediment directly underlying the canal bed, leakage potential was estimated from the simple vertical mean of inverse-model resistivity values for depth levels with geometrically increasing layer thickness with depth which resulted in mean-resistivity values biased towards the surface. This method generally produced reliable results, but an improved analysis method was needed to account for situations where confining units, composed of less permeable material, underlie units with greater permeability. In this report, prepared by the U.S. Geological Survey in cooperation with the North Platte Natural Resources District, the authors use geostatistical analysis to develop the minimum-unadjusted method to compute a relative leakage potential based on the minimum resistivity value in a vertical column of the resistivity model. The minimum-unadjusted method considers the effects of homogeneous confining units. The minimum-adjusted method also is developed to incorporate the effect of local lithologic heterogeneity on water transmission. Seven sites with differing geologic contexts were selected following review of the capacitively coupled resistivity data collected in 2004. A reevaluation of these sites using the mean, minimum-unadjusted, and minimum-adjusted methods was performed to compare the different approaches for estimating leakage potential. Five of the seven sites contained underlying confining units, for which the minimum-unadjusted and minimum-adjusted methods accounted for the confining-unit effect. Estimates of overall leakage potential were lower for the minimum-unadjusted and minimum-adjusted methods than those estimated by the mean method. For most sites, the local heterogeneity adjustment procedure of the minimum-adjusted method resulted in slightly larger overall leakage-potential estimates. In contrast to the mean method, the two minimum-based methods allowed the least permeable areas to control the overall vertical permeability of the subsurface. The minimum-adjusted method refined leakage-potential estimation by additionally including local lithologic heterogeneity effects.

Electrical Double Layer Capacitance in a Graphene-embedded Al2O3 Gate Dielectric

PubMed Central

Ki Min, Bok; Kim, Seong K.; Jun Kim, Seong; Ho Kim, Sung; Kang, Min-A; Park, Chong-Yun; Song, Wooseok; Myung, Sung; Lim, Jongsun; An, Ki-Seok

2015-01-01

Graphene heterostructures are of considerable interest as a new class of electronic devices with exceptional performance in a broad range of applications has been realized. Here, we propose a graphene-embedded Al2O3 gate dielectric with a relatively high dielectric constant of 15.5, which is about 2 times that of Al2O3, having a low leakage current with insertion of tri-layer graphene. In this system, the enhanced capacitance of the hybrid structure can be understood by the formation of a space charge layer at the graphene/Al2O3 interface. The electrical properties of the interface can be further explained by the electrical double layer (EDL) model dominated by the diffuse layer. PMID:26530817

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.

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.

Electrical Properties and Interfacial Studies of HfxTi1–xO2 High Permittivity Gate Insulators Deposited on Germanium Substrates

PubMed Central

Lu, Qifeng; Mu, Yifei; Roberts, Joseph W.; Althobaiti, Mohammed; Dhanak, Vinod R.; Wu, Jingjin; Zhao, Chun; Zhao, Ce Zhou; Zhang, Qian; Yang, Li; Mitrovic, Ivona Z.; Taylor, Stephen; Chalker, Paul R.

2015-01-01

In this research, the hafnium titanate oxide thin films, TixHf1–xO2, with titanium contents of x = 0, 0.25, 0.9, and 1 were deposited on germanium substrates by atomic layer deposition (ALD) at 300 °C. The approximate deposition rates of 0.2 Å and 0.17 Å per cycle were obtained for titanium oxide and hafnium oxide, respectively. X-ray Photoelectron Spectroscopy (XPS) indicates the formation of GeOx and germanate at the interface. X-ray diffraction (XRD) indicates that all the thin films remain amorphous for this deposition condition. The surface roughness was analyzed using an atomic force microscope (AFM) for each sample. The electrical characterization shows very low hysteresis between ramp up and ramp down of the Capacitance-Voltage (CV) and the curves are indicative of low trap densities. A relatively large leakage current is observed and the lowest leakage current among the four samples is about 1 mA/cm2 at a bias of 0.5 V for a Ti0.9Hf0.1O2 sample. The large leakage current is partially attributed to the deterioration of the interface between Ge and TixHf1–xO2 caused by the oxidation source from HfO2. Consideration of the energy band diagrams for the different materials systems also provides a possible explanation for the observed leakage current behavior. PMID:28793705

Experimental grid connected PV system power analysis

NASA Astrophysics Data System (ADS)

Semaoui, Smail; Abdeladim, Kamel; Arab, Amar Hadj; Boulahchich, Saliha; Amrouche, Said Ould; Yassaa, Noureddine

2018-05-01

Almost 80 % of Algerian territory is appropriate for the exploitation of solar energy. The Algerian energetic strategy provides a substantial injection of PV electricity to the national grid. Currently, about 344 MWp of PV arrays which corresponds approximately to 2,34 km2 of module surfaces, are connected on electricity grid over the national territory. The Algerian Northern regions are characterized by strong pollution and high humidity. These phenomena affect the energetic productivity of PV generator. The objective of our study is to analyze experimental grid connected PV system power in coastal locations. Hence, experiments have been conducted on three identical PV systems to determine the electrical performances. Transformer-less inverters are the most attractive for the ground-based photovoltaic (PV) system due to their efficiencies, reduced cost and weight. Besides, the absence of the galvanic isolation generates problems of capacitive leakage current on the AC side and the degradation of the insulation resistance on the DC side of the inverter. In this work, experimental study of the behavior of single-phase inverters without transformers is presented. The main objective of this work is to study the degradation of the insulation resistance at the input of the inverter, and the capacitive leakage current at the output of the inverter. This study was achieved at the CDER on a rainy day of 15/03/2017, on the first PV plant connected to the low voltage network in Algeria. This investigation can help forecasting the PV array energetic production by taking into account natural conditions.

Zirconium doped TiO{sub 2} thin films: A promising dielectric layer

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

Kumar, Arvind; Mondal, Sandip, E-mail: sandipmondal@physics.iisc.ernet.in; Rao, K. S. R. Koteswara

2016-05-06

In the present work, we have fabricated the zirconium doped TiO{sub 2} thin (ZTO) films from a facile spin – coating method. The addition of Zirconium in TiO{sub 2} offers conduction band offset to Si and consequently decreased the leakage current density by approximately two orders as compared to pure TiO{sub 2} thin (TO) films. The ZTO thin film shows a high dielectric constant 27 with a very low leakage current density ∼10{sup −8} A/cm{sup 2}. The oxide capacitate, flat band voltage and change in flat band voltage are 172 pF, -1.19 V and 54 mV. The AFM analysis confirmed the compactmore » and pore free flat surface. The RMS surface roughness is found to be 1.5 Å. The ellipsometry analysis also verified the fact with a high refractive index 2.21.« less

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.

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.

Thin-film composite materials as a dielectric layer for flexible metal-insulator-metal capacitors.

PubMed

Tiwari, Jitendra N; Meena, Jagan Singh; Wu, Chung-Shu; Tiwari, Rajanish N; Chu, Min-Ching; Chang, Feng-Chih; Ko, Fu-Hsiang

2010-09-24

A new organic-organic nanoscale composite thin-film (NCTF) dielectric has been synthesized by solution deposition of 1-bromoadamantane and triblock copolymer (Pluronic P123, BASF, EO20-PO70-EO20), in which the precursor solution has been achieved with organic additives. We have used a sol-gel process to make a metal-insulator-metal capacitor (MIM) comprising a nanoscale (10 nm-thick) thin-film on a flexible polyimide (PI) substrate at room temperature. Scanning electron microscope and atomic force microscope revealed that the deposited NCTFs were crack-free, uniform, highly resistant to moisture absorption, and well adhered on the Au-Cr/PI. The electrical properties of 1-bromoadamantane-P123 NCTF were characterized by dielectric constant, capacitance, and leakage current measurements. The 1-bromoadamantane-P123 NCTF on the PI substrate showed a low leakage current density of 5.5 x 10(-11) A cm(-2) and good capacitance of 2.4 fF at 1 MHz. In addition, the calculated dielectric constant of 1-bromoadamantane-P123 NCTF was 1.9, making them suitable candidates for use in future flexible electronic devices as a stable intermetal dielectric. The electrical insulating properties of 1-bromoadamantane-P123 NCTF have been improved due to the optimized dipole moments of the van der Waals interactions.

A physical model for the reverse leakage current in (In,Ga)N/GaN light-emitting diodes based on nanowires

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

Musolino, M.; Treeck, D. van, E-mail: treeck@pdi-berlin.de; Tahraoui, A.

2016-01-28

We investigated the origin of the high reverse leakage current in light emitting diodes (LEDs) based on (In,Ga)N/GaN nanowire (NW) ensembles grown by molecular beam epitaxy on Si substrates. To this end, capacitance deep level transient spectroscopy (DLTS) and temperature-dependent current-voltage (I-V) measurements were performed on a fully processed NW-LED. The DLTS measurements reveal the presence of two distinct electron traps with high concentrations in the depletion region of the p-i-n junction. These band gap states are located at energies of 570 ± 20 and 840 ± 30 meV below the conduction band minimum. The physical origin of these deep level states is discussed. Themore » temperature-dependent I-V characteristics, acquired between 83 and 403 K, show that different conduction mechanisms cause the observed leakage current. On the basis of all these results, we developed a quantitative physical model for charge transport in the reverse bias regime. By taking into account the mutual interaction of variable range hopping and electron emission from Coulombic trap states, with the latter being described by phonon-assisted tunnelling and the Poole-Frenkel effect, we can model the experimental I-V curves in the entire range of temperatures with a consistent set of parameters. Our model should be applicable to planar GaN-based LEDs as well. Furthermore, possible approaches to decrease the leakage current in NW-LEDs are proposed.« less

Thin film integrated capacitors with sputtered-anodized niobium pentoxide dielectric for decoupling applications

NASA Astrophysics Data System (ADS)

Jacob, Susan

Electronics system miniaturization is a major driver for high-k materials. High-k materials in capacitors allow for high capacitance, enabling system miniaturization. Ta2O5 (k˜24) has been the dominant high-k material in the electronic industry for decoupling capacitors, filter capacitors, etc. In order to facilitate further system miniaturization, this project has investigated thin film integrated capacitors with Nb2O5 dielectric. Nb2O 5 has k˜41 and is a potential candidate for replacing Ta2O5. But, the presence of suboxides (NbO2 and NbO) in the dielectric deteriorates the electrical properties (leakage current, thermal instability of capacitance, etc.). Also, the high oxygen solubility of niobium results in oxygen diffusion from the dielectric to niobium metal, if any is present. The major purpose of this project was to check the ability of NbN as a diffusion barrier and fabricate thermally stable niobium capacitors. As a first step to produce niobium capacitors, the material characterizations of reactively sputtered Nb2O5 and NbN were done. Thickness and film composition, and crystal structures of the sputtered films were obtained and the deposition parameters for the desired stoichiometry were found. Also, anodized Nb2O5 was characterized for its stoichiometry and thickness. To study the effect of nitrides on capacitance and thermal stability, Ta2O5 capacitors were initially fabricated with and without TaN. The results showed that the nitride does not affect the capacitance, and that capacitors with TaN are stable up to 150°C. In the next step, niobium capacitors were first fabricated with anodized dielectric and the oxygen diffusion issues associated with capacitor processing were studied. Reactively sputtered Nb2O5 was anodized to form complete Nb2O5 (with few oxygen vacancies) and NbN was used to sandwich the dielectric. The capacitor fabrication was not successful due to the difficulties in anodizing the sputtered dielectric. Another method, anodizing reactively sputtered Nb2O5 and a thin layer of sputtered niobium metal yielded high yield (99%) capacitors. Capacitors were fabricated with and without NbN and the results showed 93% decrease in leakage for a capacitor with ˜2000 A dielectric when NbN was present in the structure. These capacitors could withstand 20 V and showed 2.7 muA leakage current at 5 V. These results were obtained after thermal storage at 100°C and 150°C in air for 168 hours at each temperature. Two set of experiments were performed using Ta2O5 dielectric: one to determine the effect of anodization end point on the thickness (capacitance) and the second to determine the effect of boiling the dielectric on functional yield. The anodization end point experiment showed that the final current of anodization along with the anodizing voltage determines the anodic oxide thickness. The lower the current, the thicker the films produced by anodization. Therefore, it was important to specify the final current along with the anodization voltage for oxide growth rate. The capacitors formed with boiled wafers showed better functional yield 3 out of 5 times compared with the unboiled wafer. Niobium anodization was studied for the Nb--->Nb 2O5 conversion ratio and the effect of anodization bath temperature on the oxide film; a color chart was prepared for thicknesses ranging from 1900 A - 5000 A. The niobium metal to oxide conversion ratio was found to change with temperature.

Electrical transport and capacitance characteristics of metal-insulator-metal structures using hexagonal and cubic boron nitride films as dielectrics

NASA Astrophysics Data System (ADS)

Teii, Kungen; Kawamoto, Shinsuke; Fukui, Shingo; Matsumoto, Seiichiro

2018-04-01

Metal-insulator-metal capacitor structures using thick hexagonal and cubic boron nitride (hBN and cBN) films as dielectrics are produced by plasma jet-enhanced chemical vapor deposition, and their electrical transport and capacitance characteristics are studied in a temperature range of 298 to 473 K. The resistivity of the cBN film is of the order of 107 Ω cm at 298 K, which is lower than that of the hBN film by two orders of magnitude, while it becomes the same order as the hBN film above ˜423 K. The dominant current transport mechanism at high fields (≥1 × 104 V cm-1) is described by the Frenkel-Poole emission and thermionic emission models for the hBN and cBN films, respectively. The capacitance of the hBN film remains stable for a change in alternating-current frequency and temperature, while that of the cBN film has variations of at most 18%. The dissipation factor as a measure of energy loss is satisfactorily low (≤5%) for both films. The origin of leakage current and capacitance variation is attributed to a high defect density in the film and a transition interlayer between the substrate and the film, respectively. This suggests that cBN films with higher crystallinity, stoichiometry, and phase purity are potentially applicable for dielectrics like hBN films.

Transport and charging mechanisms in Ta2O5 thin films for capacitive RF MEMS switches application

NASA Astrophysics Data System (ADS)

Persano, A.; Quaranta, F.; Martucci, M. C.; Cretı, P.; Siciliano, P.; Cola, A.

2010-06-01

The potential of sputtered Ta2O5 thin films to be used as dielectric layers in capacitive radio frequency microelectromechanical system switches is evaluated by investigating two factors of crucial importance for the performance of these devices which are the transport mechanisms and the charging effects in the dielectric layer. We find that Ta2O5 films show good electrical and dielectrical properties for the considered application in terms of a low leakage current density of 4 nA/cm2 for E =1 MV/cm, a high breakdown field of 4 MV/cm and a high dielectric constant of 32. For electric fields lower than 1 MV/cm the conduction mechanism is found to be variable-range hopping in the temperature range 300-400 K, while nearest-neighbor hopping is observed at higher temperatures. For fields in the range 1-4 MV/cm Poole-Frenkel becomes the dominant conduction mechanism. Current and capacitance transients used to investigate the charging effects show a decay which is well described by the stretched-exponential law, thus providing further insights on capture and emission processes.

Transparent nanotubular capacitors based on transplanted anodic aluminum oxide templates.

PubMed

Zhang, Guozhen; Wu, Hao; Chen, Chao; Wang, Ti; Wu, Wenhui; Yue, Jin; Liu, Chang

2015-03-11

Transparent AlZnO/Al2O3/AlZnO nanocapacitor arrays have been fabricated by atomic layer deposition in anodic aluminum oxide templates transplanted on the AlZnO/glass substrates. A high capacitance density of 37 fF/μm(2) is obtained, which is nearly 5.8 times bigger than that of planar capacitors. The capacitance density almost remains the same in a broad frequency range from 1 kHz to 200 kHz. Moreover, a low leakage current density of 1.7 × 10(-7) A/cm(2) at 1 V has been achieved. The nanocapacitors exhibit an average optical transmittance of more than 80% in the visible range, and thus open the door to practical applications in transparent integrated circuits.

Study of Sn and Mg doping effects on TiO2/Ge stack structure by combinatorial synthesis

NASA Astrophysics Data System (ADS)

Nagata, Takahiro; Suzuki, Yoshihisa; Yamashita, Yoshiyuki; Ogura, Atsushi; Chikyow, Toyohiro

2018-04-01

The effects of Sn and Mg doping of a TiO2 film on a Ge substrate were investigated to improve leakage current properties and Ge diffusion into the TiO2 film. For systematic analysis, dopant-composition-spread TiO2 samples with dopant concentrations of up to 20.0 at. % were fabricated by RF sputtering and a combinatorial method. X-ray photoelectron spectroscopy revealed that the instability of Mg doping of TiO2 at dopant concentrations above 10.5 at. %. Both Sn and Mg dopants reduced Ge diffusion into TiO2. Sn doping enhanced the crystallization of the rutile phase, which is a high-dielectric-constant phase, although the Mg-doped TiO2 film indicated an amorphous structure. Sn-doping indicated systematic leakage current reduction with increasing dopant concentration. Doping at Sn concentrations higher than 16.8 at. % improved the leakage properties (˜10-7 A/cm2 at -3.0 V) and capacitance-voltage properties of metal-insulator-semiconductor (MIS) operation. The Sn doping of TiO2 may be useful for interface control and as a dielectric material for Ge-based MIS capacitors.

Lead zirconate titanate (PZT)-based thin film capacitors for embedded passive applications

NASA Astrophysics Data System (ADS)

Kim, Taeyun

Investigations on the key processing parameters and properties relationship for lead zirconate titanate (PZT, 52/48) based thin film capacitors for embedded passive capacitor application were performed using electroless Ni coated Cu foils as substrates. Undoped and Ca-doped PZT (52/48) thin film capacitors were prepared on electroless Ni coated Cu foil by chemical solution deposition. For PZT (52/48) thin film capacitors on electroless Ni coated Cu foil, voltage independent (zero tunability) capacitance behavior was observed. Dielectric constant reduced to more than half of the identical capacitor processed on Pt/SiO2/Si. Dielectric properties of the capacitors were mostly dependent on the crystallization temperature. Capacitance densities of almost 350 nF/cm2 and 0.02˜0.03 of loss tangent were routinely measured for capacitors crystallized at 575˜600°C. Leakage current showed dependence on film thickness and crystallization temperature. From a two-capacitor model, the existence of a low permittivity interface layer (permittivity ˜30) was suggested. For Ca-doped PZT (52/48) thin film capacitors prepared on Pt, typical ferroelectric and dielectric properties were measured up to 5 mol% Ca doping. When Ca-doped PZT (52/48) thin film capacitors were prepared on electroless Ni coated Cu foil, phase stability was influenced by Ca doping and phosphorous content. Dielectric properties showed dependence on the crystallization temperature and phosphorous content. Capacitance density of ˜400 nF/cm2 was achieved, which is an improvement by more than 30% compared to undoped composition. Ca doping also reduced the temperature coefficient of capacitance (TCC) less than 10%, all of them were consistent in satisfying the requirements of embedded passive capacitor. Leakage current density was not affected significantly by doping. To tailor the dielectric and reliability properties, ZrO2 was selected as buffer layer between PZT and electroless Ni. Only RF magnetron sputtering process could yield stable ZrO2 layers on electroless Ni coated Cu foil. Other processes resulted in secondary phase formation, which supports the reaction between PZT capacitor and electroless Ni might be dominated by phosphorous component. (Abstract shortened by UMI.)

Synthesis and Characterization of Cross-Linked Nanocomposite as a Gate Dielectric for p-Type Silicon Field-Effect Transistor

NASA Astrophysics Data System (ADS)

Hashemi, Adeleh; Bahari, Ali; Ghasemi, Shahram

2018-03-01

A good cross-linking between a povidone-silicon oxide nanocomposite has been created using a polar solvent. Furthermore, the effect of annealing temperatures (150°C, 200°C, and 240°C) on the solution-processed povidone-silicon oxide dielectric films has been studied. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy were applied to identify the chemical interactions of the nanocomposite. Morphology of the thin films was examined using atomic force microscopy. Electrical parameters of field effect transistors (FETs) were calculated on the basis of the information obtained from current-voltage (I-V) and capacitance-voltage (C-V) measurements in the metal-insulator-semiconductor structure. Nanocomposite films had very low surface roughness (0.036-0.084 nm). Si-O-Si and Si-O-C covalent bonds as well as Si-OH hydrogen bonds were formed in the nanocomposite structure. High hole mobilities (1.15-3.87 cm2 V-1 s-1) and low leakage current densities were obtained for the p-type Si FETs. The decrease in the Si-OH hydrogen bonds in the dielectric film annealed at 150°C led to a decrease in capacitance and leakage current as well as threshold voltage, and resulted in an increase in mobility and on/off current ratio. By further increasing the annealing temperatures (200°C and 240°C), the binding energies of all the bonds were shifted toward lower values. Therefore, it was concluded that many bonds could have degraded and that defects might have formed in the dielectric film nanostructure leading to a decline in the electrical parameters of the FETs.

Determination of canal leakage potential using continuous resistivity profiling techniques, Interstate and Tri-State Canals, western Nebraska and eastern Wyoming, 2004

USGS Publications Warehouse

Ball, Lyndsay B.; Kress, Wade H.; Steele, Gregory V.; Cannia, James C.; Andersen, Michael J.

2006-01-01

In the North Platte River Basin, a ground-water model is being developed to evaluate the effectiveness of using water leakage from selected irrigation canal systems to enhance ground-water recharge. The U.S. Geological Survey, in cooperation with the North Platte Natural Resources District, used land-based capacitively coupled and water-borne direct-current continuous resistivity profiling techniques to map the lithology of the upper 8 meters and to interpret the relative canal leakage potential of 110 kilometers of the Interstate and Tri-State Canals in western Nebraska and eastern Wyoming. Lithologic descriptions from 25 test holes were used to evaluate the effectiveness of both techniques for indicating relative grain size. An interpretive color scale was developed that symbolizes contrasting resistivity features indicative of different grain-size categories. The color scale was applied to the vertically averaged resistivity and used to classify areas of the canals as having either high, moderate, or low canal leakage potential. When results were compared with the lithologic descriptions, both land-based and water-borne continuous resistivity profiling techniques were determined to be effective at differentiating coarse-grained from fine-grained sediment. Both techniques were useful for producing independent, similar interpretations of canal leakage potential.

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).

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

Variable electronic shutter in CMOS imager with improved anti smearing techniques

NASA Technical Reports Server (NTRS)

Pain, Bedabrata (Inventor)

2005-01-01

A leakage compensated snapshot imager provides a number of different aspects to prevent smear and other problems in a snapshot imager. The area where the imager is formed may be biased in a way that prevents photo carriers including electrons and holes from reaching a storage area. In addition, a number of different aspects may improve the efficiency. The capacitance per unit area of the storage area may be one, two or more orders of magnitude greater than the capacitance per-unit area of the photodiode. In addition, a ratio between photodiode capacitance and storage area capacitance is maintained larger than 0.7.

Vapor phase polymerization deposition of conducting polymer/graphene nanocomposites as high performance electrode materials.

PubMed

Yang, Yajie; Li, Shibin; Zhang, Luning; Xu, Jianhua; Yang, Wenyao; Jiang, Yadong

2013-05-22

In this paper, we report chemical vapor phase polymerization (VPP) deposition of novel poly(3,4-ethylenedioxythiophene) (PEDOT)/graphene nanocomposites as solid tantalum electrolyte capacitor cathode films. The PEDOT/graphene films were successfully prepared on porous tantalum pentoxide surface as cathode films through the VPP procedure. The results indicated that the high conductivity nature of PEDOT/graphene leads to the decrease of cathode films resistance and contact resistance between PEDOT/graphene and carbon paste. This nanocomposite cathode film based capacitor showed ultralow equivalent series resistance (ESR) ca. 12 mΩ and exhibited better capacitance-frequency performance than the PEDOT based capacitor. The leakage current investigation revealed that the device encapsulation process does not influence capacitor leakage current, indicating the excellent mechanical strength of PEDOT-graphene films. The graphene showed a distinct protection effect on the dielectric layer from possible mechanical damage. This high conductivity and mechanical strength graphene based conducting polymer nanocomposites indicated a promising application future for organic electrode materials.

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.

Numerical analysis of the reverse blocking enhancement in High-K passivation AlGaN/GaN Schottky barrier diodes with gated edge termination

NASA Astrophysics Data System (ADS)

Bai, Zhiyuan; Du, Jiangfeng; Xin, Qi; Li, Ruonan; Yu, Qi

2018-02-01

We conducted a numerical analysis on high-K dielectric passivated AlGaN/GaN Schottky barrier diodes (HPG-SBDs) with a gated edge termination (GET). The reverse blocking characteristics were significantly enhanced without the stimulation of any parasitic effect by varying the dielectric thickness dge under the GET, thickness TP, and dielectric constant εr of the high-K passivation layer. The leakage current was reduced by increasing εr and decreasing dge. The breakdown voltage of the device was enhanced by increasing εr and TP. The highest breakdown voltage of 970 V and the lowest leakage current of 0.5 nA/mm were achieved under the conditions of εr = 80, TP = 800 nm, and dge = 10 nm. C-V simulation revealed that the HPG-SBDs induced no parasitic capacitance by comparing the integrated charges of the devices with different high-K dielectrics and different dge.

Charging and breakdown in amorphous dielectrics: Phenomenological modeling approach and applications

NASA Astrophysics Data System (ADS)

Palit, Sambit

Amorphous dielectrics of different thicknesses (nm to mm) are used in various applications. Low temperature processing/deposition of amorphous thin-film dielectrics often result in defect-states or electronic traps. These traps are responsible for increased leakage currents and bulk charge trapping in many associated applications. Additional defects may be generated during regular usage, leading to electrical breakdown. Increased leakage currents, charge trapping and defect generation/breakdown are important and pervasive reliability concerns in amorphous dielectrics. We first explore the issue of charge accumulation and leakage in amorphous dielectrics. Historically, charge transport in amorphous dielectrics has been presumed, depending on the dielectric thickness, to be either bulk dominated (Frenkel-Poole (FP) emission) or contact dominated (Fowler-Nordheim tunneling). We develop a comprehensive dielectric charging modeling framework which solves for the transient and steady state charge accumulation and leakage currents in an amorphous dielectric, and show that for intermediate thickness dielectrics, the conventional assumption of FP dominated current transport is incorrect, and may lead to false extraction of dielectric parameters. We propose an improved dielectric characterization methodology based on an analytical approximation of our model. Coupled with ab-initio computed defect levels, the dielectric charging model explains measured leakage currents more accurately with lesser empiricism. We study RF-MEMS capacitive switches as one of the target applications of intermediate thickness amorphous dielectrics. To achieve faster analysis and design of RF-MEMS switches in particular, and electro-mechanical actuators in general, we propose a set of fundamental scaling relationships which are independent of specific physical dimensions and material properties; the scaling relationships provide an intrinsic classification of all electro-mechanical actuators. However, RF-MEMS capacitive switches are plagued by the reliability issue of temporal shifts of actuation voltages due to dielectric charge accumulation, often resulting in failure due to membrane stiction. Using the dielectric charging model, we show that in spite of unpredictable roughness of deposited dielectrics, there are predictable shifts in actuation voltages due to dielectric charging in RF-MEMS switches. We also propose a novel non-obtrusive, non-contact, fully electronic resonance based technique to characterize charging driven actuation shifts in RF-MEMS switches which overcomes limitations in conventionally used methods. Finally, we look into the issue of defect generation and breakdown in thick polymer dielectrics. Polymer materials often face premature electrical breakdown due to high electric fields and frequencies, and exposure to ambient humidity conditions. Using a field-driven correlated defect generation model, coupled with a model for temperature rise due to dielectric heating at AC stresses, we explain measured trends in time-to-breakdown and breakdown electric fields in polymer materials. Using dielectric heating we are able to explain the observed lifetime and dielectric strength reduction with increasing dielectric thicknesses. Performing lifetime measurements after exposure to controlled humidity conditions, we find that moisture ingress into a polymer material reduces activation barriers for chain breakage and increases dielectric heating. Overall, this thesis develops a comprehensive framework of dielectric charging, leakage and degradation of insulators of different thicknesses that have broad applications in multiple technologies.

Flexible solid-state supercapacitors based on three-dimensional graphene hydrogel films.

PubMed

Xu, Yuxi; Lin, Zhaoyang; Huang, Xiaoqing; Liu, Yuan; Huang, Yu; Duan, Xiangfeng

2013-05-28

Flexible solid-state supercapacitors are of considerable interest as mobile power supply for future flexible electronics. Graphene or carbon nanotubes based thin films have been used to fabricate flexible solid-state supercapacitors with high gravimetric specific capacitances (80-200 F/g), but usually with a rather low overall or areal specific capacitance (3-50 mF/cm(2)) due to the ultrasmall electrode thickness (typically a few micrometers) and ultralow mass loading, which is not desirable for practical applications. Here we report the exploration of a three-dimensional (3D) graphene hydrogel for the fabrication of high-performance solid-state flexible supercapacitors. With a highly interconnected 3D network structure, graphene hydrogel exhibits exceptional electrical conductivity and mechanical robustness to make it an excellent material for flexible energy storage devices. Our studies demonstrate that flexible supercapacitors with a 120 μm thick graphene hydrogel thin film can exhibit excellent capacitive characteristics, including a high gravimetric specific capacitance of 186 F/g (up to 196 F/g for a 42 μm thick electrode), an unprecedented areal specific capacitance of 372 mF/cm(2) (up to 402 mF/cm(2) for a 185 μm thick electrode), low leakage current (10.6 μA), excellent cycling stability, and extraordinary mechanical flexibility. This study demonstrates the exciting potential of 3D graphene macrostructures for high-performance flexible energy storage devices.

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.

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

A 3D CZT high resolution detector for x- and gamma-ray astronomy

NASA Astrophysics Data System (ADS)

Kuvvetli, I.; Budtz-Jørgensen, C.; Zappettini, A.; Zambelli, N.; Benassi, G.; Kalemci, E.; Caroli, E.; Stephen, J. B.; Auricchio, N.

2014-07-01

At DTU Space we have developed a high resolution three dimensional (3D) position sensitive CZT detector for high energy astronomy. The design of the 3D CZT detector is based on the CZT Drift Strip detector principle. The position determination perpendicular to the anode strips is performed using a novel interpolating technique based on the drift strip signals. The position determination in the detector depth direction, is made using the DOI technique based the detector cathode and anode signals. The position determination along the anode strips is made with the help of 10 cathode strips orthogonal to the anode strips. The position resolutions are at low energies dominated by the electronic noise and improve therefore with increased signal to noise ratio as the energy increases. The achievable position resolution at higher energies will however be dominated by the extended spatial distribution of the photon produced ionization charge. The main sources of noise contribution of the drift signals are the leakage current between the strips and the strip capacitance. For the leakage current, we used a metallization process that reduces the leakage current by means of a high resistive thin layer between the drift strip electrodes and CZT detector material. This method was applied to all the proto type detectors and was a very effective method to reduce the surface leakage current between the strips. The proto type detector was recently investigated at the European Synchrotron Radiation Facility, Grenoble which provided a fine 50 × 50 μm2 collimated X-ray beam covering an energy band up to 600 keV. The Beam positions are resolved very well with a ~ 0.2 mm position resolution (FWHM ) at 400 keV in all directions.

Leakage current and charging/discharging processes in barrier-type anodic alumina thin films for use in metal-insulator-metal capacitors

NASA Astrophysics Data System (ADS)

Hourdakis, E.; Koutsoureli, M.; Papaioannou, G.; Nassiopoulou, A. G.

2018-06-01

Barrier-type anodic alumina thin films are interesting for use in high capacitance density metal-insulator-metal capacitors due to their excellent dielectric properties at small thickness. This thickness is easily controlled by the anodization voltage. In previous papers we studied the main parameters of interest of the Al/barrier-type anodic alumina/Al structure for use in RF applications and showed the great potential of barrier-type anodic alumina in this respect. In this paper, we investigated in detail charging/discharging processes and leakage current of the above dielectric material. Two different sets of metal-insulator-metal capacitors were studied, namely, with the top Al electrode being either e-gun deposited or sputtered. The dielectric constant of the barrier-type anodic alumina was found at 9.3. Low leakage current was observed in all samples studied. Furthermore, depending on the film thickness, field emission following the Fowler-Nordheim mechanism was observed above an applied electric field. Charging of the anodic dielectric was observed, occurring in the bulk of the anodic layer. The stored charge was of the order of few μC/cm2 and the calculated trap density ˜2 × 1018 states/cm3, the most probable origin of charge traps being, in our opinion, positive electrolyte ions trapped in the dielectric during anodization. We do not think that oxygen vacancies play an important role, since their existence would have a more important impact on the leakage current characteristics, such as resistive memory effects or significant changes during annealing, which were not observed. Finally, discharging characteristic times as high as 5 × 109 s were measured.

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

NASA Astrophysics Data System (ADS)

Held, Martin; Schießl, Stefan P.; Miehler, Dominik; Gannott, Florentina; Zaumseil, Jana

2015-08-01

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 (HfOx) 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 at 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/cm2) 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 HfOx dielectrics.

Semiconductor radiation detector with internal gain

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

Iwanczyk, Jan; Patt, Bradley E.; Vilkelis, Gintas

An avalanche drift photodetector (ADP) incorporates extremely low capacitance of a silicon drift photodetector (SDP) and internal gain that mitigates the surface leakage current noise of an avalanche photodetector (APD). The ADP can be coupled with scintillators such as CsI(Tl), NaI(Tl), LSO or others to form large volume scintillation type gamma ray detectors for gamma ray spectroscopy, photon counting, gamma ray counting, etc. Arrays of the ADPs can be used to replace the photomultiplier tubes (PMTs) used in conjunction with scintillation crystals in conventional gamma cameras for nuclear medical imaging.

Fast switching thyristor applied in nanosecond-pulse high-voltage generator with closed transformer core.

PubMed

Li, Lee; Bao, Chaobing; Feng, Xibo; Liu, Yunlong; Fochan, Lin

2013-02-01

For a compact and reliable nanosecond-pulse high-voltage generator (NPHVG), the specification parameter selection and potential usage of fast controllable state-solid switches have an important bearing on the optimal design. The NPHVG with closed transformer core and fast switching thyristor (FST) was studied in this paper. According to the analysis of T-type circuit, the expressions for the voltages and currents of the primary and secondary windings on the transformer core of NPHVG were deduced, and the theoretical maximum analysis was performed. For NPHVG, the rise-rate of turn-on current (di/dt) across a FST may exceed its transient rating. Both mean and maximum values of di/dt were determined by the leakage inductances of the transformer, and the difference is 1.57 times. The optimum winding ratio is helpful to getting higher voltage output with lower specification FST, especially when the primary and secondary capacitances have been established. The oscillation period analysis can be effectively used to estimate the equivalent leakage inductance. When the core saturation effect was considered, the maximum di/dt estimated from the oscillating period of the primary current is more accurate than one from the oscillating period of the secondary voltage. Although increasing the leakage inductance of NPHVG can decrease di/dt across FST, it may reduce the output peak voltage of the NPHVG.

Voltage and Current Clamp Transients with Membrane Dielectric Loss

PubMed Central

Fitzhugh, R.; Cole, K. S.

1973-01-01

Transient responses of a space-clamped squid axon membrane to step changes of voltage or current are often approximated by exponential functions of time, corresponding to a series resistance and a membrane capacity of 1.0 μF/cm2. Curtis and Cole (1938, J. Gen. Physiol. 21:757) found, however, that the membrane had a constant phase angle impedance z = z1(jωτ)-α, with a mean α = 0.85. (α = 1.0 for an ideal capacitor; α < 1.0 may represent dielectric loss.) This result is supported by more recently published experimental data. For comparison with experiments, we have computed functions expressing voltage and current transients with constant phase angle capacitance, a parallel leakage conductance, and a series resistance, at nine values of α from 0.5 to 1.0. A series in powers of tα provided a good approximation for short times; one in powers of t-α, for long times; for intermediate times, a rational approximation matching both series for a finite number of terms was used. These computations may help in determining experimental series resistances and parallel leakage conductances from membrane voltage or current clamp data. PMID:4754194

Epitaxial ZnO gate dielectrics deposited by RF sputter for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors

NASA Astrophysics Data System (ADS)

Yoon, Seonno; Lee, Seungmin; Kim, Hyun-Seop; Cha, Ho-Young; Lee, Hi-Deok; Oh, Jungwoo

2018-01-01

Radio frequency (RF)-sputtered ZnO gate dielectrics for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) were investigated with varying O2/Ar ratios. The ZnO deposited with a low oxygen content of 4.5% showed a high dielectric constant and low interface trap density due to the compensation of oxygen vacancies during the sputtering process. The good capacitance-voltage characteristics of ZnO-on-AlGaN/GaN capacitors resulted from the high crystallinity of oxide at the interface, as investigated by x-ray diffraction and high-resolution transmission electron microscopy. The MOS-HEMTs demonstrated comparable output electrical characteristics with conventional Ni/Au HEMTs but a lower gate leakage current. At a gate voltage of -20 V, the typical gate leakage current for a MOS-HEMT with a gate length of 6 μm and width of 100 μm was found to be as low as 8.2 × 10-7 mA mm-1, which was three orders lower than that of the Ni/Au Schottky gate HEMT. The reduction of the gate leakage current improved the on/off current ratio by three orders of magnitude. These results indicate that RF-sputtered ZnO with a low O2/Ar ratio is a good gate dielectric for high-performance AlGaN/GaN MOS-HEMTs.

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.

Highly-wrinkled reduced graphene oxide-conductive polymer fibers for flexible fiber-shaped and interdigital-designed supercapacitors

NASA Astrophysics Data System (ADS)

Li, Bo; Cheng, Jianli; Wang, Zhuanpei; Li, Yinchuan; Ni, Wei; Wang, Bin

2018-02-01

Flexible supercapacitors have attracted great interest due to outstanding flexibility and light weight. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) fibers have the great potential in using as electrodes for flexible supercapacitors due to the good flexibility. However, the reported conductivity and specific capacitance of these PEDOT: PSS fibers are not very high, which limit their electrochemical performances. In this work, composite fibers of reduced graphene oxide(rGO)-PEDOT: PSS with a highly-wrinkled structure on the surface and pores inside are prepared by wet spinning. The fibers with different ratios of graphene to PEDOT:PSS show a distinctly enhanced conductivity up to ca. 590 S·cm-1 and high strength up to ca. 18.4 MPa. Meanwhile, the composite fibers show an improved electrochemical performances, including a high specific areal capacitance of 131 mF cm-2 and high specific areal energy density of 4.55 μWh·cm-2. The flexible supercapacitors including fiber-shaped supercapacitors and interdigital designed supercapacitors not only could work in different bending states without obvious capacitance decay, but also have small leakage current. The interdigital design can further improve the performances of composite fibers with high capacitance and high utilization compared with traditional parallel connected structure.

Pros and cons of symmetrical dual-k spacer technology in hybrid FinFETs

NASA Astrophysics Data System (ADS)

Pradhan, K. P.; Andrade, M. G. C.; Sahu, P. K.

2016-12-01

The symmetrical dual-k spacer technology in hybrid FinFETs has been widely explored for better electrostatic control of the fin-based devices in nanoscale region. Since, high-k tangible spacer materials are broadly became a matter of study due to their better immunity to the short channel effects (SCEs) in nano devices. However, the only cause that restricts the circuit designers from using high-k spacer is the unreasonable increasing fringing capacitances. This work quantitatively analyzed the benefits and drawbacks of considering two different dielectric spacer materials symmetrically in either sides of the channel for the hybrid device. From the demonstrated results, the inclusion of high-k spacer predicts an effective reduction in off-state leakage along with an improvement in drive current. However, these devices have paid the cost in terms of a high total gate-to-gate capacitance (Cgg) that consequently results poor cutoff frequency (fT) and delay.

Solid-State Densification of Spun-Cast Self-Assembled Monolayers for Use in Ultra-Thin Hybrid Dielectrics.

PubMed

Hutchins, Daniel O; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E; Castner, David G; Ma, Hong; Jen, Alex K-Y

2012-11-15

Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlO x (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10 -8 A cm -2 and capacitance density of 0.62 µF cm -2 at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm 2 V -1 s -1 .

Solid-State Densification of Spun-Cast Self-Assembled Monolayers for Use in Ultra-Thin Hybrid Dielectrics

PubMed Central

Hutchins, Daniel O.; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E.; Castner, David G.; Ma, Hong; Jen, Alex K.-Y.

2013-01-01

Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlOx (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10−8 A cm−2 and capacitance density of 0.62 µF cm−2 at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm2 V−1 s−1. PMID:24288423

Highly flexible and all-solid-state paperlike polymer supercapacitors.

PubMed

Meng, Chuizhou; Liu, Changhong; Chen, Luzhuo; Hu, Chunhua; Fan, Shoushan

2010-10-13

In recent years, much effort have been dedicated to achieve thin, lightweight and even flexible energy-storage devices for wearable electronics. Here we demonstrate a novel kind of ultrathin all-solid-state supercapacitor configuration with an extremely simple process using two slightly separated polyaniline-based electrodes well solidified in the H(2)SO(4)-polyvinyl alcohol gel electrolyte. The thickness of the entire device is much comparable to that of a piece of commercial standard A4 print paper. Under its highly flexible (twisting) state, the integrate device shows a high specific capacitance of 350 F/g for the electrode materials, well cycle stability after 1000 cycles and a leakage current of as small as 17.2 μA. Furthermore, due to its polymer-based component structure, it has a specific capacitance of as high as 31.4 F/g for the entire device, which is more than 6 times that of current high-level commercial supercapacitor products. These highly flexible and all-solid-state paperlike polymer supercapacitors may bring new design opportunities of device configuration for energy-storage devices in the future wearable electronic area.

Electro-mechanical characterization of structural supercapacitors

NASA Astrophysics Data System (ADS)

Gallagher, T.; LaMaster, D.; Ciocanel, C.; Browder, C.

2012-04-01

The paper presents electrical and mechanical properties of structural supercapacitors and discusses limitations associated with the approach taken for the electrical properties evaluation. The structural supercapacitors characterized in this work had the electrodes made of carbon fiber weave, separator made of several cellulose based products, and the solid electrolyte made as PEGDGE based polymer blend. The reported electrical properties include capacitance and leakage resistance; the former was measured using cyclic voltammetry. Mechanical properties have been evaluated thorough tensile and three point bending tests performed on structural supercapacitor coupons. The results indicate that the separator material plays an important role on the electrical as well as mechanical properties of the structural capacitor, and that Celgard 3501 used as separator leads to most benefits for both mechanical and electrical properties. Specific capacitance and leakage resistance as high as 1.4kF/m3 and 380kΩ, respectively, were achieved. Two types of solid polymer electrolytes were used in fabrication, with one leading to higher and more consistent leakage resistance values at the expense of a slight decrease in specific capacitance when compared to the other SPE formulation. The ultimate tensile strength and modulus of elasticity of the developed power storage composite were evaluated at 466MPa and 18.9MPa, respectively. These values are 58% and 69% of the tensile strength and modulus of elasticity values measured for a single layer composite material made with the same type of carbon fiber and with a West System 105 epoxy instead of solid polymer electrolyte.

Electrical characterization of MIM capacitor comprises an adamantane film at room temperature

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

Tiwari, Rajanish N., E-mail: rajanisht@gmail.com; Toyota Technological Institute, 2-12-1Hisakata, Tempaku-Ku, Nagoya 468-8511; Yoshimura, Masamichi

2016-06-15

We fabricated a new metal-insulator-metal capacitor at room temperature, comprising a ∼90 nm thin low–k adamantane film on a Si substrate. The surface morphology of deposited organic film was investigated by using scanning electron microscopy and Raman spectroscopy, which is confirmed that the adamantane thin film was uniformly distributed on the Si surface. The adamantane film exhibits a low leakage current density of 7.4 x 10{sup −7} A/cm{sup 2} at 13.5 V, better capacitance density of 2.14 fF/μm{sup 2} at 100 KHz.

Electrical characterization of 4H-SiC metal-oxide-semiconductor structure with Al2O3 stacking layers as dielectric

NASA Astrophysics Data System (ADS)

Chang, P. K.; Hwu, J. G.

2018-02-01

Interface defects and oxide bulk traps conventionally play important roles in the electrical performance of SiC MOS device. Introducing the Al2O3 stack grown by repeated anodization of Al films can notably lower the leakage current in comparison to the SiO2 structure, and enhance the minority carrier response at low frequency when the number of Al2O3 layers increase. In addition, the interface quality is not deteriorated by the stacking of Al2O3 layers because the stacked Al2O3 structure grown by anodization possesses good uniformity. In this work, the capacitance equivalent thickness (CET) of stacking Al2O3 will be up to 19.5 nm and the oxidation process can be carried out at room temperature. For the Al2O3 gate stack with CET 19.5 nm on n-SiC substrate, the leakage current at 2 V is 2.76 × 10-10 A/cm2, the interface trap density at the flatband voltage is 3.01 × 1011 eV-1 cm-2, and the effective breakdown field is 11.8 MV/cm. Frequency dispersion and breakdown characteristics may thus be improved as a result of the reduction in trap density. The Al2O3 stacking layers are capable of maintaining the leakage current as low as possible even after constant voltage stress test, which will further ameliorate reliability characteristics.

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

High Performance All-solid Supercapacitors Based on the Network of Ultralong Manganese dioxide/Polyaniline Coaxial Nanowires

NASA Astrophysics Data System (ADS)

Zhou, Junli; Yu, Lin; Liu, Wei; Zhang, Xiaodan; Mu, Wei; Du, Xu; Zhang, Zhe; Deng, Yulin

2015-12-01

In recent years, thin, lightweight and flexible solid supercapacitors are of considerable interest as energy storage devices. Here we demonstrated all-solid supercapacitors (SSCs) with high electrochemical properties, low self-discharge characteristics based on manganese dioxide/polyaniline (MNW/PANI) coaxial nanowire networks. The synergistic effect of MnO2/PANI plus the unique coaxial nanostructure of the ultralong nanowires with a highly interconnected network effectively enhance the conductivity and capacitive performance of the SSCs device. The MNW/PANI composite with 62.5% MnO2 exhibits an outstanding areal specific capacitance reaching 346 mF/cm2 at 5 mV s-1 which is significant higher than most previously reported solid supercapacitors (15.3 mF/cm2-109 mF/cm2) and is close to the that of the best graphene films solid state supercapacitors (372 mF/cm2). In contrast, only 190 mF/cm2 of areal specific capacitance was obtained for the pure MnO2 NW network. The supercapacitors also exhibited low leakage current as small as 20.1 μA, which demonstrated that the MNW/PANI SSCs have great potential for practical applications.

Densely-packed graphene/conducting polymer nanoparticle papers for high-volumetric-performance flexible all-solid-state supercapacitors

NASA Astrophysics Data System (ADS)

Yang, Chao; Zhang, Liling; Hu, Nantao; Yang, Zhi; Wei, Hao; Xu, Zhichuan J.; Wang, Yanyan; Zhang, Yafei

2016-08-01

Graphene-based all-solid-state supercapacitors (ASSSCs) are one of the most ideal candidates for high-performance flexible power sources. The achievement of high volumetric energy density is highly desired for practical application of this type of ASSSCs. Here, we present a facile method to boost volumetric performances of graphene-based flexible ASSSCs through incorporation of ultrafine polyaniline-poly(4-styrenesulfonate) (PANI-PSS) nanoparticles in reduced graphene oxide (rGO) papers. A compact structure is obtained via intimate contact and π-π interaction between PANI-PSS nanoparticles and rGO sheets. The hybrid paper electrode with the film thickness of 13.5 μm, shows an extremely high volumetric specific capacitance of 272 F/cm3 (0.37 A/cm3 in a three-electrode cell). The assembled ASSSCs show a large volumetric specific capacitance of 217 F/cm3 (0.37 A/cm3 in a two-electrode cell), high volumetric energy and power density, excellent capacitance stability, small leakage current as well as low self-discharge characteristics, revealing the usefulness of this robust hybrid paper for high-performance flexible energy storage devices.

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.

High Performance All-solid Supercapacitors Based on the Network of Ultralong Manganese dioxide/Polyaniline Coaxial Nanowires.

PubMed

Zhou, Junli; Yu, Lin; Liu, Wei; Zhang, Xiaodan; Mu, Wei; Du, Xu; Zhang, Zhe; Deng, Yulin

2015-12-08

In recent years, thin, lightweight and flexible solid supercapacitors are of considerable interest as energy storage devices. Here we demonstrated all-solid supercapacitors (SSCs) with high electrochemical properties, low self-discharge characteristics based on manganese dioxide/polyaniline (MNW/PANI) coaxial nanowire networks. The synergistic effect of MnO2/PANI plus the unique coaxial nanostructure of the ultralong nanowires with a highly interconnected network effectively enhance the conductivity and capacitive performance of the SSCs device. The MNW/PANI composite with 62.5% MnO2 exhibits an outstanding areal specific capacitance reaching 346 mF/cm(2) at 5 mV s(-1) which is significant higher than most previously reported solid supercapacitors (15.3 mF/cm(2)-109 mF/cm(2)) and is close to the that of the best graphene films solid state supercapacitors (372 mF/cm(2)). In contrast, only 190 mF/cm(2) of areal specific capacitance was obtained for the pure MnO2 NW network. The supercapacitors also exhibited low leakage current as small as 20.1 μA, which demonstrated that the MNW/PANI SSCs have great potential for practical applications.

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

Analysis of source/drain engineered 22nm FDSOI using high-k spacers

NASA Astrophysics Data System (ADS)

Malviya, Abhishek Kumar; Chauhan, R. K.

2018-04-01

While looking at the current classical scaling of devices there are lots of short channel effects come into consideration. In this paper, a novel device structure is proposed that is an improved structure of Modified Source(MS) FDSOI in terms of better electrical performance, on current and reduced off state leakage current with a higher Ion/Ioff ratio that helps in fast switching of low power nano electronic devices. Proposed structure has Modified drain and source regions with two different type to doping profile at 22nm gate length. In the upper part of engineered region (MD and MS) the doping concentration is kept high and less in the lower region. The purpose was to achieve low parasitic capacitance in source and drain region by reducing doping concentration [1].

The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

PubMed Central

Mao, Ling-Feng; Ning, Huan-Sheng; Wang, Jin-Yan

2015-01-01

Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc. PMID:26039589

The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

PubMed

Mao, Ling-Feng; Ning, Huan-Sheng; Wang, Jin-Yan

2015-01-01

Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc.

Single-Walled Carbon Nanotube Dominated Micron-Wide Stripe Patterned-Based Ferroelectric Field-Effect Transistors with HfO2 Defect Control Layer

NASA Astrophysics Data System (ADS)

Tan, Qiuhong; Wang, Qianjin; Liu, Yingkai; Yan, Hailong; Cai, Wude; Yang, Zhikun

2018-04-01

Ferroelectric field-effect transistors (FeFETs) with single-walled carbon nanotube (SWCNT) dominated micron-wide stripe patterned as channel, (Bi,Nd)4Ti3O12 films as insulator, and HfO2 films as defect control layer were developed and fabricated. The prepared SWCNT-FeFETs possess excellent properties such as large channel conductance, high on/off current ratio, high channel carrier mobility, great fatigue endurance performance, and data retention. Despite its thin capacitance equivalent thickness, the gate insulator with HfO2 defect control layer shows a low leakage current density of 3.1 × 10-9 A/cm2 at a gate voltage of - 3 V.

Single-Walled Carbon Nanotube Dominated Micron-Wide Stripe Patterned-Based Ferroelectric Field-Effect Transistors with HfO2 Defect Control Layer.

PubMed

Tan, Qiuhong; Wang, Qianjin; Liu, Yingkai; Yan, Hailong; Cai, Wude; Yang, Zhikun

2018-04-27

Ferroelectric field-effect transistors (FeFETs) with single-walled carbon nanotube (SWCNT) dominated micron-wide stripe patterned as channel, (Bi,Nd) 4 Ti 3 O 12 films as insulator, and HfO 2 films as defect control layer were developed and fabricated. The prepared SWCNT-FeFETs possess excellent properties such as large channel conductance, high on/off current ratio, high channel carrier mobility, great fatigue endurance performance, and data retention. Despite its thin capacitance equivalent thickness, the gate insulator with HfO 2 defect control layer shows a low leakage current density of 3.1 × 10 -9  A/cm 2 at a gate voltage of - 3 V.

Device and material characterization and analytic modeling of amorphous silicon thin film transistors

NASA Astrophysics Data System (ADS)

Slade, Holly Claudia

Hydrogenated amorphous silicon thin film transistors (TFTs) are now well-established as switching elements for a variety of applications in the lucrative electronics market, such as active matrix liquid crystal displays, two-dimensional imagers, and position-sensitive radiation detectors. These applications necessitate the development of accurate characterization and simulation tools. The main goal of this work is the development of a semi- empirical, analytical model for the DC and AC operation of an amorphous silicon TFT for use in a manufacturing facility to improve yield and maintain process control. The model is physically-based, in order that the parameters scale with gate length and can be easily related back to the material and device properties. To accomplish this, extensive experimental data and 2D simulations are used to observe and quantify non- crystalline effects in the TFTs. In particular, due to the disorder in the amorphous network, localized energy states exist throughout the band gap and affect all regimes of TFT operation. These localized states trap most of the free charge, causing a gate-bias-dependent field effect mobility above threshold, a power-law dependence of the current on gate bias below threshold, very low leakage currents, and severe frequency dispersion of the TFT gate capacitance. Additional investigations of TFT instabilities reveal the importance of changes in the density of states and/or back channel conduction due to bias and thermal stress. In the above threshold regime, the model is similar to the crystalline MOSFET model, considering the drift component of free charge. This approach uses the field effect mobility to take into account the trap states and must utilize the correct definition of threshold voltage. In the below threshold regime, the density of deep states is taken into account. The leakage current is modeled empirically, and the parameters are temperature dependent to 150oC. The capacitance of the TFT can be modeled using a transmission line model, which is implemented using a small signal circuit with access resistors in series with the source and drain capacitances. This correctly reproduces the frequency dispersion in the TFT. Automatic parameter extraction routines are provided and are used to test the robustness of the model on a variety of devices from different research laboratories. The results demonstrate excellent agreement, showing that the model is suitable for device design, scaling, and implementation in the manufacturing process.

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.

Dopingless ferroelectric tunnel FET architecture for the improvement of performance of dopingless n-channel tunnel FETs

NASA Astrophysics Data System (ADS)

Lahgere, Avinash; Panchore, Meena; Singh, Jawar

2016-08-01

In this paper, we propose a novel tunnel field-effect transistor (TFET) based on charge plasma (CP) and negative capacitance (NC) for enhanced ON-current and steep subthreshold swing (SS). It is shown that the replacement of standard insulator for gate stack with ferroelectric (Fe) insulator yields NC and high electric field at the tunneling junction. Similarly, use of dopingless silicon nanowire with CP has a genuine advantage in process engineering. Therefore, combination of both technology boosters (CP and NC) in the proposed device enable low thermal budget, process variation immunity, and excellent electrical characteristics in contrast with its counterpart dopingless (DL) TFET (DL-TFET). An optimized device accomplishes an impressive 10× improvement in on-current, 100× reduced leakage current, 3× more transconductance (gm), and on-off current ratio of ∼1011 as compared to DL-TFET.

Electrical properties of radio-frequency sputtered HfO2 thin films for advanced CMOS technology

NASA Astrophysics Data System (ADS)

Sarkar, Pranab Kumar; Roy, Asim

2015-08-01

The Hafnium oxide (HfO2) high-k thin films have been deposited by radio frequency (rf) sputtering technique on p-type Si (100) substrate. The thickness, composition and phases of films in relation to annealing temperatures have been investigated by using cross sectional FE-SEM (Field Emission Scanning Electron Microscope) and grazing incidence x-ray diffraction (GI-XRD), respectively. GI-XRD analysis revealed that at annealing temperatures of 350°C, films phases change to crystalline from amorphous. The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the annealed HfO2 film have been studied employing Al/HfO2/p-Si metal-oxide-semiconductor (MOS) structures. The electrical properties such as dielectric constant, interface trap density and leakage current density have been also extracted from C-V and I-V Measurements. The value of dielectric constant, interface trap density and leakage current density of annealed HfO2 film is obtained as 23,7.57×1011eV-1 cm-2 and 2.7×10-5 Acm-2, respectively. In this work we also reported the influence of post deposition annealing onto the trapping properties of hafnium oxide and optimized conditions under which no charge trapping is observed into the dielectric stack.

Noise Reduction Techniques and Scaling Effects towards Photon Counting CMOS Image Sensors

PubMed Central

Boukhayma, Assim; Peizerat, Arnaud; Enz, Christian

2016-01-01

This paper presents an overview of the read noise in CMOS image sensors (CISs) based on four-transistors (4T) pixels, column-level amplification and correlated multiple sampling. Starting from the input-referred noise analytical formula, process level optimizations, device choices and circuit techniques at the pixel and column level of the readout chain are derived and discussed. The noise reduction techniques that can be implemented at the column and pixel level are verified by transient noise simulations, measurement and results from recently-published low noise CIS. We show how recently-reported process refinement, leading to the reduction of the sense node capacitance, can be combined with an optimal in-pixel source follower design to reach a sub-0.3erms- read noise at room temperature. This paper also discusses the impact of technology scaling on the CIS read noise. It shows how designers can take advantage of scaling and how the Metal-Oxide-Semiconductor (MOS) transistor gate leakage tunneling current appears as a challenging limitation. For this purpose, both simulation results of the gate leakage current and 1/f noise data reported from different foundries and technology nodes are used.

Gate oxide thickness dependence of the leakage current mechanism in Ru/Ta2O5/SiON/Si structures

NASA Astrophysics Data System (ADS)

Ťapajna, M.; Paskaleva, A.; Atanassova, E.; Dobročka, E.; Hušeková, K.; Fröhlich, K.

2010-07-01

Leakage conduction mechanisms in Ru/Ta2O5/SiON/Si structures with rf-sputtered Ta2O5 with thicknesses ranging from 13.5 to 1.8 nm were systematically studied. Notable reaction at the Ru/Ta2O5 interface was revealed by capacitance-voltage measurements. Temperature-dependent current-voltage characteristics suggest the bulk-limited conduction mechanism in all metal-oxide-semiconductor structures. Under gate injection, Poole-Frenkel emission was identified as a dominant mechanism for 13.5 nm thick Ta2O5. With an oxide thickness decreasing down to 3.5 nm, the conduction mechanism transforms to thermionic trap-assisted tunnelling through the triangular barrier. Under substrate injection, the dominant mechanism gradually changes with decreasing thickness from thermionic trap-assisted tunnelling to trap-assisted tunnelling through the triangular barrier; Poole-Frenkel emission was not observed at all. A 0.7 eV deep defect level distributed over Ta2O5 is assumed to be responsible for bulk-limited conduction mechanisms and is attributed to H-related defects or oxygen vacancies in Ta2O5.

High Performance All-solid Supercapacitors Based on the Network of Ultralong Manganese dioxide/Polyaniline Coaxial Nanowires

PubMed Central

Zhou, Junli; Yu, Lin; Liu, Wei; Zhang, Xiaodan; Mu, Wei; Du, Xu; Zhang, Zhe; Deng, Yulin

2015-01-01

In recent years, thin, lightweight and flexible solid supercapacitors are of considerable interest as energy storage devices. Here we demonstrated all-solid supercapacitors (SSCs) with high electrochemical properties, low self-discharge characteristics based on manganese dioxide/polyaniline (MNW/PANI) coaxial nanowire networks. The synergistic effect of MnO2/PANI plus the unique coaxial nanostructure of the ultralong nanowires with a highly interconnected network effectively enhance the conductivity and capacitive performance of the SSCs device. The MNW/PANI composite with 62.5% MnO2 exhibits an outstanding areal specific capacitance reaching 346 mF/cm2 at 5 mV s−1 which is significant higher than most previously reported solid supercapacitors (15.3 mF/cm2–109 mF/cm2) and is close to the that of the best graphene films solid state supercapacitors (372 mF/cm2). In contrast, only 190 mF/cm2 of areal specific capacitance was obtained for the pure MnO2 NW network. The supercapacitors also exhibited low leakage current as small as 20.1 μA, which demonstrated that the MNW/PANI SSCs have great potential for practical applications. PMID:26644364

A modified low-temperature wafer bonding method using spot pressing bonding technique and water glass adhesive layer

NASA Astrophysics Data System (ADS)

Xu, Yang; Wang, Shengkai; Wang, Yinghui; Chen, Dapeng

2018-02-01

A modified low-temperature wafer bonding method using a spot pressing bonding technique and a water glass adhesive layer is proposed. The electrical properties of the water glass layer has been studied by capacitance-voltage (C-V) and electric current-voltage (I-V) measurements. It is found that the adhesive layer can be regarded as a good insulator in terms of leakage current density. The bonding mechanism and the motion of bubbles during the thermal treatment are investigated. The dominant factor for the bubble motion in the modified bonding process is the gradient of pressure introduced by the spot pressing force. It is proved that the modified method achieves low-temperature adhesive bonding, minimizes the effect of water desorption, and provides good bonding performance.

A high-performance channel engineered charge-plasma-based MOSFET with high-κ spacer

NASA Astrophysics Data System (ADS)

Shan, Chan; Wang, Ying; Luo, Xin; Bao, Meng-tian; Yu, Cheng-hao; Cao, Fei

2017-12-01

In this paper, the performance of graded channel double-gate MOSFET (GC-DGFET) that utilizes the charge-plasma concept and a high-κ spacer is investigated through 2-D device simulations. The results demonstrate that GC-DGFET with high-κ spacer can effectively improve the ON-state driving current (ION) and reduce the OFF-leakage current (IOFF). We find that reduction of the initial energy barrier between the source and channel is the origin of this ION enhancement. The reason for the IOFF reduction is identified to be the extension of the effective channel length owing to the fringing field via high-κ spacers. Consequently, these devices offer enhanced performance by reducing the total gate-to-gate capacitance (Cgg) and decreasing the intrinsic delay (τ).

The challenges of achieving good electrical and mechanical properties when making structural supercapacitors

NASA Astrophysics Data System (ADS)

Ciocanel, C.; Browder, C.; Simpson, C.; Colburn, R.

2013-04-01

The paper presents results associated with the electro-mechanical characterization of a composite material with power storage capability, identified throughout the paper as a structural supercapacitor. The structural supercapacitor uses electrodes made of carbon fiber weave, a separator made of Celgard 3501, and a solid PEG-based polymer blend electrolyte. To be a viable structural supercapacitor, the material has to have good mechanical and power storage/electrical properties. The literature in this area is inconsistent on which electrical properties are evaluated, and how those properties are assessed. In general, measurements of capacitance or specific capacitance (i.e. capacitance per unit area or per unit volume) are made, without considering other properties such as leakage resistance and equivalent series resistance of the supercapacitor. This paper highlights the significance of these additional electrical properties, discusses the fluctuation of capacitance over time, and proposes methods to improve the stability of the material's electric properties over time.

Characteristics of capacitance-micro-displacement for model of complex interior surface of the 3D Taiji ball and its applications

NASA Astrophysics Data System (ADS)

Zhu, Ruo-Gu; Jiang, Kun; Qing, Zhao-Bo; Liu, Yue-Hui; Yan, Jun

2006-11-01

Taiji image originated from ancient China. It is not only the Taoism emblem but also the ancient graphic presentation sign to everything origin. It either has a too far-reaching impact on traditional culture of China, or is influencing the development of current natural science. On the basis of analyzing the classical philosophic theory of two-dimensional (2-D) Taiji image, we developed it into the model of complex interior surface-three-dimensional (3-D) Taiji ball, and explored its possible applications. Combining modern mathematics and physics knowledge, we have studied on the physical meaning of 3-D Taiji ball, thus the plane change of original Taiji image is developed into space change which is more close to the real world. The change layers are obvious increased notably, and the amount of information included in this model increases correspondingly. We also realized a special paper 3-D Taiji ball whose surface is coved with metal foil by means of laser manufacture. A new experiment set-up for measuring micro displace has been designed and constituted thus the relation between capacitance and micro displacement for the 3-D Taiji ball has performed. Experimental and theoretical analyses are also finished. This models of 3-D Taiji ball for physical characteristics are the first time set up. Experimental data and fitting curves between capacitance and micro displacement for the special paper Taiji ball coved with metal foil are suggested. It is shown that the special Taiji ball has less leakage capacitance or more strengthen electric field than an ordinary half ball capacitance. Finally their potential applied values are explored.

Effects of microstructural defects on the performance of base-metal multilayer ceramic capacitors

NASA Astrophysics Data System (ADS)

Samantaray, Malay M.

Multilayer ceramic capacitors (MLCCs), owing to their processing conditions, can exhibit microstructure defects such as electrode porosity and roughness. The effect of such extrinsic defects on the electrical performance of these devices needs to be understood in order to achieve successful miniaturization into the submicron dielectric layer thickness regime. Specifically, the presence of non-planar and discontinuous electrodes can lead to local field enhancements while the relative morphologies of two adjacent electrodes determine variations in the local dielectric thickness. To study the effects of electrode morphologies, an analytical approach is taken to calculate the electric field enhancement and leakage current with respect to an ideal parallel-plate capacitor. Idealized electrode defects are used to simulate the electric field distribution. It is shown that the electrode roughness causes both the electric field and the leakage current to increase with respect to that of the ideal flat parallel-plate capacitor. Moreover, finite element methods are used to predict electric field enhancements by as high as 100% within capacitor structures containing rough interfaces and porosity. To understand the influence of microstructural defects on field distributions and leakage current, the real three-dimensional microstructure of local regions in MLCCs are reconstructed using a serial-sectioning technique in the focused ion beam. These microstructures are then converted into a finite element model in order to simulate the perturbations in electric field due to the presence of electrode defects. The electric field is three times the average value, and this leads to increase in current density of these devices. It is also shown that increasing sintering rates of MLCCs leads to improved electrode morphology with smoother more continuous electrodes, which in turn leads to a decrease in electric field enhancement and calculated leakage current density. To simulate scaling effects, the dielectric layer thickness is reduced from 2.0mum to 0.5mum in the three-dimensional microstructure keeping the same electrode morphology. It is seen that the effect of microstructure defects is more pronounced as one approaches thinner layers, leading to higher local electric field concentrations and a concomitant drop in insulation resistance. It is also seen that the electric field values are as high as 3.8 times the average field in termination regions due the disintegrated structure of the electrodes. In order to assess the effect of microstructure on MLCC performance, two sets of multilayer capacitors subjected to two vastly different sintering rates of 150ºC/hr and 3000ºC/hr are compared for their electrical properties. Capacitors with higher electrode continuity exhibit proportionally higher capacitance, provided the grain size distributions are similar. From the leakage current measurements, it is found that the Schottky barrier at the electrode-dielectric interface controls the conduction mechanism. This barrier height is calculated to be 1.06 eV for slow-fired MLCCs and was 1.15 for fast-fired MLCCs. This shows that high concentration of electrode defects cause field perturbations and subsequent drop in the net Schottky barrier height. These results are further supported by frequency-dependent impedance measurements. With temperature dependence behavior of current-voltage trends we note that below temperatures of 135°C, the conduction is controlled by interfacial effects, whereas at higher temperatures it is consistent with bulk-controlled space charge limited current for the samples that are highly reoxidized. The final part of this work studies the various aspects of the initial stages of degradation of MLCCs. MLCCs subjected to unipolar and bipolar degradation are studied for changes in microstructure and electrical properties. With bipolar degradation studies new insights into degradation are gained. First, the ionic accumulation with oxygen vacancies at cathodes is only partially reversible. This has implications on the controlling interface with electronic conduction. Also, it is shown that oxygen vacancy accumulation near the cathodes leads to a drop in insulation resistance. The capacitance also increases with progressive steps of degradation due to the effective thinning of dielectric layer. The reduction in interfacial resistance is also confirmed by impedance analysis. Finally, it is observed that on degradation, the dominant leakage current mechanism changes from being controlled by cathodic injection of electrons to being controlled by their anodic extraction. (Abstract shortened by UMI.)

Performance and Reliability of Solid Tantalum Capacitors at Cryogenic Conditions

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2006-01-01

Performance of different types of solid tantalum capacitors was evaluated at room and low temperatures, down to 15 K. The effect of temperature on frequency dependencies of capacitance, effective series resistances (ESR), leakage currents, and breakdown voltages has been investigated and analyzed. To assess thermo-mechanical robustness of the parts, several groups of loose capacitors and those soldered on FR4 boards were subjected to multiple (up to 500) temperature cycles between room temperature and 77 K. Experiments and mathematical modeling have shown that degradation in tantalum capacitors at low temperatures is mostly due to increasing resistance of the manganese cathode layer, resulting in substantial decrease of the roll-off frequency. Absorption currents follow a power law, I approximately t(sup -m), with the exponent m varying from 0.8 to 1.1. These currents do not change significantly at cryogenic conditions and the value of the exponent remains the same down to 15 K. Variations of leakage currents with voltage can be described by Pool-Frenkel and Schottky mechanisms of conductivity, with the Schottky mechanism prevailing at cryogenic conditions. Breakdown voltages of tantalum capacitors increase and the probability of scintillations decreases at cryogenic temperatures. However, breakdown voltages measured during surge current testing decrease at liquid nitrogen (LN) compared to room-temperature conditions. Results of temperature cycling suggest that tantalum capacitors are capable of withstanding multiple exposures to cryogenic conditions, but the probability of failures varies for different part types.

Limitations on energy resolution of segmented silicon detectors

NASA Astrophysics Data System (ADS)

Wiącek, P.; Chudyba, M.; Fiutowski, T.; Dąbrowski, W.

2018-04-01

In the paper experimental study of charge division effects and energy resolution of X-ray silicon pad detectors are presented. The measurements of electrical parameters, capacitances and leakage currents, for six different layouts of pad arrays are reported. The X-ray spectra have been measured using a custom developed dedicated low noise front-end electronics. The spectra measured for six different detector layouts have been analysed in detail with particular emphasis on quantitative evaluation of charge division effects. Main components of the energy resolution due to Fano fluctuations, electronic noise, and charge division, have been estimated for six different sensor layouts. General recommendations regarding optimisation of pad sensor layout for achieving best possible energy resolution have been formulated.

Floating-gate memory based on an organic metal-insulator-semiconductor capacitor

NASA Astrophysics Data System (ADS)

William, S.; Mabrook, M. F.; Taylor, D. M.

2009-08-01

A floating gate memory element is described which incorporates an evaporated gold film embedded in the gate dielectric of a metal-insulator-semiconductor capacitor based on poly(3-hexylthiophene). On exceeding a critical amplitude in the voltage sweep, hysteresis is observed in the capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the device. The anticlockwise hysteresis in C-V is consistent with strong electron trapping during the positive cycle but little hole trapping during the negative cycle. We argue that the clockwise hysteresis observed in the negative cycle of the I-V plot, arises from leakage of trapped holes through the underlying insulator to the control gate.

Transparent capacitors with hybrid ZnO:Al and Ag nanowires as electrodes.

PubMed

Zhang, Guozhen; Wu, Hao; Wang, Xiao; Wang, Ti; Liu, Chang

2016-03-11

Transparent conducting films with a composite structure of AlZnO-Ag nanowires (AgNWs) have been prepared by atomic layer deposition. The sheet resistance was reduced from 120 to 9 Ω when the AgNW networks were involved. Transparent capacitors with Al2O3-TiO2-Al2O3 dielectrics were fabricated on the composite electrodes and demonstrated a capacitance density of 10.1 fF μm(-2), which was significantly higher than that of capacitors with AlZnO electrodes (8.8 fF μm(-1)). The capacitance density remained almost unchanged in a broad frequency range from 3 kHz to 1 MHz. Moreover, a low leakage current density of 2.4 × 10(-7) A cm(-2) at 1 V was achieved. Transparent and flexible capacitors were also fabricated using the composite electrodes, and demonstrated an improved bendability. The transparent capacitors showed an average optical transmittance over 70% in the visible range, and thus open the door to practical applications in transparent integrated circuits.

A novel hetero-material gate-underlap electrically doped TFET for improving DC/RF and ambipolar behaviour

NASA Astrophysics Data System (ADS)

Yadav, Shivendra; Sharma, Dheeraj; Chandan, Bandi Venkata; Aslam, Mohd; Soni, Deepak; Sharma, Neeraj

2018-05-01

In this article, the impact of gate-underlap with hetero material (low band gap) has been investigated in terms of DC and Analog/RF parameters by proposed device named as hetero material gate-underlap electrically doped TFET (HM-GUL-ED-TFET). Gate-underlap resolves the problem of ambipolarity, gate leakage current (Ig) and slightly improves the gate to drain capacitance, but DC performance is almost unaffected. Further, the use of low band gap material (Si0.5 Ge) in proposed device causes a drastic improvement in the DC as well as RF figures of merit. We have investigated the Si0.5 Ge as a suitable candidate among different low band gap materials. In addition, the sensitivity of gate-underlap in terms of gate to drain inversion and parasitic capacitances has been studied for HM-GUL-ED-TFET. Further, relatively it is observed that gate-underlap is a better way than drain-underlap in the proposed structure to improve Analog/RF performances without degrading the DC parameters of device. Additionally, hetero-junction alignment analysis has been done for fabrication feasibility.

Comparison of Multilayer Dielectric Thin Films for Future Metal-Insulator-Metal Capacitors: Al2O3/HfO2/Al2O3 versus SiO2/HfO2/SiO2

NASA Astrophysics Data System (ADS)

Park, Sang-Uk; Kwon, Hyuk-Min; Han, In-Shik; Jung, Yi-Jung; Kwak, Ho-Young; Choi, Woon-Il; Ha, Man-Lyun; Lee, Ju-Il; Kang, Chang-Yong; Lee, Byoung-Hun; Jammy, Raj; Lee, Hi-Deok

2011-10-01

In this paper, two kinds of multilayered metal-insulator-metal (MIM) capacitors using Al2O3/HfO2/Al2O3 (AHA) and SiO2/HfO2/SiO2 (SHS) were fabricated and characterized for radio frequency (RF) and analog mixed signal (AMS) applications. The experimental results indicate that the AHA MIM capacitor (8.0 fF/µm2) is able to provide a higher capacitance density than the SHS MIM capacitor (5.1 fF/µm2), while maintaining a low leakage current of about 50 nA/cm2 at 1 V. The quadratic voltage coefficient of capacitance, α gradually decreases as a function of stress time under constant voltage stress (CVS). The parameter variation of SHS MIM capacitors is smaller than that of AHA MIM capacitors. The effects of CVS on voltage linearity and time-dependent dielectric breakdown (TDDB) characteristics were also investigated.

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.

Atomic layer deposition of ZrO2 on W for metal-insulator-metal capacitor application

NASA Astrophysics Data System (ADS)

Lee, Sang-Yun; Kim, Hyoungsub; McIntyre, Paul C.; Saraswat, Krishna C.; Byun, Jeong-Soo

2003-04-01

A metal-insulator-metal (MIM) capacitor using ZrO2 on tungsten (W) metal bottom electrode was demonstrated and characterized in this letter. Both ZrO2 and W metal were synthesized by an atomic layer deposition (ALD) method. High-quality 110˜115 Å ZrO2 films were grown uniformly on ALD W using ZrCl4 and H2O precursors at 300 °C, and polycrystalline ZrO2 in the ALD regime could be obtained. A 13˜14-Å-thick interfacial layer between ZrO2 and W was observed after fabrication, and it was identified as WOx through angle-resolved x-ray photoelectron spectroscopy analysis with wet chemical etching. The apparent equivalent oxide thickness was 20˜21 Å. An effective dielectric constant of 22˜25 including an interfacial WOx layer was obtained by measuring capacitance and thickness of MIM capacitors with Pt top electrodes. High capacitance per area (16˜17 fF/μm2) and low leakage current (10-7 A/cm2 at ±1 V) were achieved.

Development of a high-yield via-last through silicon via process using notchless silicon etching and wet cleaning of the first metal layer

NASA Astrophysics Data System (ADS)

Watanabe, Naoya; Kikuchi, Hidekazu; Yanagisawa, Azusa; Shimamoto, Haruo; Kikuchi, Katsuya; Aoyagi, Masahiro; Nakamura, Akio

2017-07-01

A high-yield via-last through silicon via (TSV) process has been developed using notchless Si etching and wet cleaning of the first metal layer. In this process, the notching was suppressed by optimizing the deep Si etching conditions and wet cleaning was performed using an organic alkaline solution to remove reaction products generated by the etchback step on the first metal layer. By this process, a number of small TSVs (TSV diameter: 6 µm TSV depth: 22 µm number of TSVs: 20,000/chip) could be formed uniformly on an 8-in. wafer. The electrical characteristics of small TSVs formed by this via-last TSV process were investigated. The TSV resistance determined by four-terminal measurements was approximately 24 mΩ. The leakage current between the TSV and the Si substrate was 2.5 pA at 5 V. The TSV capacitance determined using an inductance-capacitance-resistance (LCR) meter was 54 fF, while the TSV yield determined from TSV chain measurements was high (83%) over an 8-in. wafer.

Characterization of Piezoelectric Stacks for Space Applications

NASA Technical Reports Server (NTRS)

Sherrit, Stewart; Jones, Christopher; Aldrich, Jack; Blodget, Chad; Bao, Xiaoqi; Badescu, Mircea; Bar-Cohen, Yoseph

2008-01-01

Future NASA missions are increasingly seeking to actuate mechanisms to precision levels in the nanometer range and below. Co-fired multilayer piezoelectric stacks offer the required actuation precision that is needed for such mechanisms. To obtain performance statistics and determine reliability for extended use, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and high temperatures and voltages. In order to study the lifetime performance of these stacks, five actuators were driven sinusoidally for up to ten billion cycles. An automated data acquisition system was developed and implemented to monitor each stack's electrical current and voltage waveforms over the life of the test. As part of the monitoring tests, the displacement, impedance, capacitance and leakage current were measured to assess the operation degradation. This paper presents some of the results of this effort.

Understanding Artifacts in Impedance Spectroscopy

DOE PAGES

Veal, B. W.; Baldo, P. M.; Paulikas, A. P.; ...

2014-11-22

Four-terminal measurements of impedance spectra have long been troubled by the presence of high frequency artifacts that typically indicate unphysically large inductive behavior. In this paper, we follow up on the observation of Fleig et al., that voltage and current are necessarily measured in different locations of the potentiostat circuit, and that, typically, the electrometer input is a virtual ground. In this case, the capacitance of coaxial cables that connect sample electrodes to the potentiostat provides a high frequency conduction path to ground, so that some of the current that passes through the sample bypasses the electrometer. In four-electrode measurements,more » this mechanism produces the observed inductive artifacts. We examine a variety of simulated samples, with calculations compared to measurements of relevant circuits, to quantitatively investigate the nature of the artifacts. Model results agree with measurements when the leakage capacitances are properly included in the circuit analyses. With understanding of the origin of the inductive artifacts, the four-electrode method can be effectively utilized, enabling a combination of two-, three- and four-electrode measurements to be used to best advantage. Finally, using this combination of electrode configurations, temperature dependent measurements of SrTiO 3, Y 2O 3-stabilized ZrO 2, and In 2O 3 films deposited on YSZ substrates are presented.« less

Trielectrode capacitive pressure transducer

NASA Technical Reports Server (NTRS)

Coon, G. W. (Inventor)

1976-01-01

A capacitive transducer and circuit especially suited for making measurements in a high-temperature environment are described. The transducer includes two capacitive electrodes and a shield electrode. As the temperature of the transducer rises, the resistance of the insulation between the capacitive electrode decreases and a resistive current attempts to interfere with the capacitive current between the capacitive electrodes. The shield electrode and the circuit coupled there reduce the resistive current in the transducer. A bridge-type circuit coupled to the transducer ignores the resistive current and measures only the capacitive current flowing between the capacitive electrodes.

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.

Low temperature solution processed high-κ ZrO2 gate dielectrics for nanoelectonics

NASA Astrophysics Data System (ADS)

Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara

2016-05-01

The high-κ gate dielectrics, specifically amorphous films offer salient features such as exceptional mechanical flexibility, smooth surfaces and better uniformity associated with low leakage current density. In this work, ∼35 nm thick amorphous ZrO2 films were deposited on silicon substrate at low temperature (300 °C, 1 h) from facile spin-coating method and characterized by various analytical techniques. The X-ray diffraction and X-ray photoelectron spectroscopy reveal the formation of amorphous phase ZrO2, while ellipsometry analysis together with the Atomic Force Microscope suggest the formation of dense film with surface roughness of 1.5 Å, respectively. The fabricated films were integrated in metal-oxide-semiconductor (MOS) structures to check the electrical capabilities. The oxide capacitance (Cox), flat band capacitance (CFB), flat band voltage (VFB), dielectric constant (κ) and oxide trapped charges (Qot) extracted from high frequency (1 MHz) C-V curve are 186 pF, 104 pF, 0.37 V, 15 and 2 × 10-11 C, respectively. The small flat band voltage 0.37 V, narrow hysteresis and very little frequency dispersion between 10 kHz-1 MHz suggest an excellent a-ZrO2/Si interface with very less trapped charges in the oxide. The films exhibit a low leakage current density 4.7 × 10-9 A/cm2 at 1 V. In addition, the charge transport mechanism across the MOSC is analyzed and found to have a strong bias dependence. The space charge limited conduction mechanism is dominant in the high electric field region (1.3-5 V) due to the presence of traps, while the trap-supported tunneling is prevailed in the intermediate region (0.35-1.3 V). Low temperature solution processed ZrO2 thin films obtained are of high quality and find their importance as a potential dielectric layer on Si and polymer based flexible electronics.

Charge plasma based source/drain engineered Schottky Barrier MOSFET: Ambipolar suppression and improvement of the RF performance

NASA Astrophysics Data System (ADS)

Kale, Sumit; Kondekar, Pravin N.

2018-01-01

This paper reports a novel device structure for charge plasma based Schottky Barrier (SB) MOSFET on ultrathin SOI to suppress the ambipolar leakage current and improvement of the radio frequency (RF) performance. In the proposed device, we employ dual material for the source and drain formation. Therefore, source/drain is divided into two parts as main source/drain and source/drain extension. Erbium silicide (ErSi1.7) is used as main source/drain material and Hafnium metal is used as source/drain extension material. The source extension induces the electron plasma in the ultrathin SOI body resulting reduction of SB width at the source side. Similarly, drain extension also induces the electron plasma at the drain side. This significantly increases the SB width due to increased depletion at the drain end. As a result, the ambipolar leakage current can be suppressed. In addition, drain extension also reduces the parasitic capacitances of the proposed device to improve the RF performance. The optimization of length and work function of metal used in the drain extension is performed to achieve improvement in device performance. Moreover, the proposed device makes fabrication simpler, requires low thermal budget and free from random dopant fluctuations.

Properties of zirconium silicate and zirconium-silicon oxynitride high-k dielectric alloys for advanced microelectronic applications: Chemical and electrical characterizations

NASA Astrophysics Data System (ADS)

Ju, Byongsun

2005-11-01

As the microelectronic devices are aggressively scaled down to the 1999 International Technology Roadmap, the advanced complementary metal oxide semiconductor (CMOS) is required to increase packing density of ultra-large scale integrated circuits (ULSI). High-k alternative dielectrics can provide the required levels of EOT for device scaling at larger physical thickness, thereby providing a materials pathway for reducing the tunneling current. Zr silicates and its end members (SiO2 and ZrO2) and Zr-Si oxynitride films, (ZrO2)x(Si3N 4)y(SiO2)z, have been deposited using a remote plasma-enhanced chemical vapor deposition (RPECVD) system. After deposition of Zr silicate, the films were exposed to He/N2 plasma to incorporate nitrogen atoms into the surface of films. The amount of incorporated nitrogen atoms was measured by on-line Auger electron spectrometry (AES) as a function of silicate composition and showed its local minimum around the 30% silicate. The effect of nitrogen atoms on capacitance-voltage (C-V) and leakage-voltage (J-V) were also investigated by fabricating metal-oxide-semiconductor (MOS) capacitors. Results suggested that incorporating nitrogen into silicate decreased the leakage current in SiO2-rich silicate, whereas the leakage increased in the middle range of silicate. Zr-Si oxynitride was a pseudo-ternary alloy and no phase separation was detected by x-ray photoelectron spectroscopy (XPS) analysis up to 1100°C annealing. The leakage current of Zr-Si oxynitride films showed two different temperature dependent activation energies, 0.02 eV for low temperature and 0.3 eV for high temperature. Poole-Frenkel emission was the dominant leakage mechanism. Zr silicate alloys with no Si3N4 phase were chemically separated into the SiO2 and ZrO2 phase as annealed above 900°C. While chemical phase separation in Zr silicate films with Si 3N4 phase (Zr-Si oxynitride) were suppressed as increasing the amount of Si3N4 phase due to the narrow bonding network m Si3N4 phase. (3.4 bonds/atom for Si3 N4 network, 2.67 bonds/atom for SiO2 network).

Testing the Ge Detectors for the MAJORANA DEMONSTRATOR

NASA Astrophysics Data System (ADS)

Xu, W.; Abgrall, N.; Aguayo, E.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Boswell, M.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y.-D.; Christofferson, C. D.; Combs, D. C.; Cuesta, C.; Detwiler, J. A.; Doe, P. J.; Efremenko, Yu.; Egorov, V.; Ejiri, H.; Elliott, S. R.; Fast, J. E.; Finnerty, P.; Fraenkle, F. M.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, V. E.; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Leviner, L. E.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Meijer, S.; Mertens, S.; Nomachi, M.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Phillips, D. G.; Poon, A. W. P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, A. G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, K. J.; Snyder, N.; Suriano, A. M.; Thompson, J.; Timkin, V.; Tornow, W.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Yakushev, E.; Young, A. R.; Yu, C.-H.; Yumatov, V.

High purity germanium (HPGe) crystals will be used for the MAJORANA DEMONSTRATOR, where they serve as both the source and the detector for neutrinoless double beta decay. It is crucial for the experiment to understand the performance of the HPGe crystals. A variety of crystal properties are being investigated, including basic properties such as energy resolution, efficiency, uniformity, capacitance, leakage current and crystal axis orientation, as well as more sophisticated properties, e.g. pulse shapes and dead layer and transition layer distributions. In this talk, we will present our measurements that characterize the HPGe crystals. We will also discuss the our simulation package for the detector characterization setup, and show that additional information can be extracted from data-simulation comparisons.

Testing the Ge detectors for the MAJORANA DEMONSTRATOR

DOE PAGES

Xu, W.; Abgrall, N.; Aguayo, E.; ...

2015-03-24

High purity germanium (HPGe) crystals will be used for the Majorana Demonstrator, where they serve as both the source and the detector for neutrinoless double beta decay. It is crucial for the experiment to understand the performances of the HPGe crystals. A variety of crystal properties are being investigated, including both basic properties such as energy resolution, efficiency, uniformity, capacitance, leakage current and crystal axis orientation, as well as more sophisticated properties, e.g. pulse shapes and dead layer and transition layer distribution. In this talk, we will present our measurements that characterize the HPGe crystals. In addition, we will discussmore » the experiment’s simulation package for the detector characterization setup, where additional information is learned from data simulation comparisons.« less

Performance of a hydrogen uranyl phosphate-carbon double-layer solid capacitor

NASA Astrophysics Data System (ADS)

Pham-Thi, M.; Adet, Ph.; Velasco, G.; Colomban, Ph.

1986-05-01

A mixture of commercially available carbon black (C) powders and hydrogen uranyl phosphate (HUP) precipitate can be used as the electrode material for miniaturized double-layer capacitors. A solid cell of C-HUP/HUP/C-HUP has a capacitance of 1 F which, given the device area and thickness of 0.8 sq cm and 0.2 cm respectively, corresponds to an energy density of more than 5 J/cu cm. The charge x voltage factor is higher than 5 x 10 to the -6th s and the working voltage is over 1.6 V. The leakage current is lower than 3 microamps at room temperature. The electrolyte can be operated up to about 120 C if the device is hermetically sealed.

Direct DC 10 V comparison between two programmable Josephson voltage standards made of niobium nitride (NbN)-based and niobium (Nb)-based Josephson junctions

NASA Astrophysics Data System (ADS)

Solve, S.; Chayramy, R.; Maruyama, M.; Urano, C.; Kaneko, N.-H.; Rüfenacht, A.

2018-04-01

BIPM’s new transportable programmable Josephson voltage standard (PJVS) has been used for an on-site comparison at the National Metrology Institute of Japan (NMIJ) and the National Institute of Advanced Industrial Science and Technology (AIST) (NMIJ/AIST, hereafter called just NMIJ unless otherwise noted). This is the first time that an array of niobium-based Josephson junctions with amorphous niobium silicon Nb x Si1-x barriers, developed by the National Institute of Standards and Technology4 (NIST), has been directly compared to an array of niobium nitride (NbN)-based junctions (developed by the NMIJ in collaboration with the Nanoelectronics Research Institute (NeRI), AIST). Nominally identical voltages produced by both systems agreed within 5 parts in 1012 (0.05 nV at 10 V) with a combined relative uncertainty of 7.9  ×  10-11 (0.79 nV). The low side of the NMIJ apparatus is, by design, referred to the ground potential. An analysis of the systematic errors due to the leakage current to ground was conducted for this ground configuration. The influence of a multi-stage low-pass filter installed at the output measurement leads of the NMIJ primary standard was also investigated. The number of capacitances in parallel in the filter and their insulation resistance have a direct impact on the amplitude of the systematic voltage error introduced by the leakage current, even if the current does not necessarily return to ground. The filtering of the output of the PJVS voltage leads has the positive consequence of protecting the array from external sources of noise. Current noise, when coupled to the array, reduces the width or current range of the quantized voltage steps. The voltage error induced by the leakage current in the filter is an order of magnitude larger than the voltage error in the absence of all filtering, even though the current range of steps is significantly decreased without filtering.

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.

High efficiency and enhanced ESD properties of UV LEDs by inserting p-GaN/p-AlGaN superlattice

NASA Astrophysics Data System (ADS)

Huang, Yong; Li, PeiXian; Yang, Zhuo; Hao, Yue; Wang, XiaoBo

2014-05-01

Significantly improved electrostatic discharge (ESD) properties of InGaN/GaN-based UV light-emitting diode (LED) with inserting p-GaN/p-AlGaN superlattice (p-SLs) layers (instead of p-AlGaN single layer) between multiple quantum wells and Mg-doped GaN layer are reported. The pass yield of the LEDs increased from 73.53% to 93.81% under negative 2000 V ESD pulses. In addition, the light output power (LOP) and efficiency droop at high injection current were also improved. The mechanism of the enhanced ESD properties was then investigated. After excluding the effect of capacitance modulation, high-resolution X-ray diffraction (XRD) and atomic force microscope (AFM) measurements demonstrated that the dominant mechanism of the enhanced ESD properties is the material quality improved by p-SLs, which indicated less leakage paths, rather than the current spreading improved by p-SLs.

Structural and electrical properties of single crystalline SrZrO3 epitaxially grown on Ge (001)

NASA Astrophysics Data System (ADS)

Lim, Z. H.; Ahmadi-Majlan, K.; Grimley, E. D.; Du, Y.; Bowden, M.; Moghadam, R.; LeBeau, J. M.; Chambers, S. A.; Ngai, J. H.

2017-08-01

We present structural and electrical characterization of SrZrO3 that has been epitaxially grown on Ge(001) by oxide molecular beam epitaxy. Single crystalline SrZrO3 can be nucleated on Ge via deposition at low temperatures followed by annealing at 550 °C in ultra-high vacuum. Photoemission spectroscopy measurements reveal that SrZrO3 exhibits a type-I band arrangement with respect to Ge, with conduction and valence band offsets of 1.4 eV and 3.66 eV, respectively. Capacitance-voltage and current-voltage measurements on 4 nm thick films reveal low leakage current densities and an unpinned Fermi level at the interface that allows modulation of the surface potential of Ge. Ultra-thin films of epitaxial SrZrO3 can thus be explored as a potential gate dielectric for Ge.

Novel Dry-Type Glucose Sensor Based on a Metal-Oxide-Semiconductor Capacitor Structure with Horseradish Peroxidase + Glucose Oxidase Catalyzing Layer

NASA Astrophysics Data System (ADS)

Lin, Jing-Jenn; Wu, You-Lin; Hsu, Po-Yen

2007-10-01

In this paper, we present a novel dry-type glucose sensor based on a metal-oxide-semiconductor capacitor (MOSC) structure using SiO2 as a gate dielectric in conjunction with a horseradish peroxidase (HRP) + glucose oxidase (GOD) catalyzing layer. The tested glucose solution was dropped directly onto the window opened on the SiO2 layer, with a coating of HRP + GOD catalyzing layer on top of the gate dielectric. From the capacitance-voltage (C-V) characteristics of the sensor, we found that the glucose solution can induce an inversion layer on the silicon surface causing a gate leakage current flowing along the SiO2 surface. The gate current changes Δ I before and after the drop of glucose solution exhibits a near-linear relationship with increasing glucose concentration. The Δ I sensitivity is about 1.76 nA cm-2 M-1, and the current is quite stable 20 min after the drop of the glucose solution is tested.

Organic field effect transistors - Study of performance parameters for different dielectric layer thickness

NASA Astrophysics Data System (ADS)

Assis, Anu; Shahul Hameed T., A.; Predeep, P.

2017-06-01

Mobility and current handling capabilities of Organic Field Effect Transistor (OFET) are vitally important parameters in the electrical performance where the material parameters and thickness of different layers play significant role. In this paper, we report the simulation of an OFET using multi physics tool, where the active layer is pentacene and Poly Methyl Methacrylate (PMMA) forms the dielectric. Electrical characterizations of the OFET on varying the thickness of the dielectric layer from 600nm to 400nm are simulated and drain current, transconductance and mobility are analyzed. In the study it is found that even though capacitance increases with reduction in dielectric layer thickness, the transconductance effect is reflected many more times in the mobility which in turn could be attributed to the variations in transverse electric field. The layer thickness below 300nm may result in gate leakage current points to the requirement of optimizing the thickness of different layers for better performance.

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

Tanaka, T.J.; Antonescu, C.

A program to assess the impact of smoke on digital instrumentation and control (I and C) safety systems began in 1994, funded by the US Nuclear Regulatory Commission Office of Research. Digital I and C safety systems are likely replacements for today`s analog systems. The nuclear industry has little experience in qualifying digital electronics for critical systems, part of which is understanding system performance during plant fires. The results of tests evaluating the performance of digital circuits and chip technologies exposed to the various smoke and humidity conditions representative of cable fires are discussed. Tests results show that low tomore » moderate smoke densities can cause intermittent failures of digital systems. Smoke increases leakage currents between biased contacts, leading to shorts. Chips with faster switching times, and thus higher output drive currents, are less sensitive to leakage currents and thus to smoke. Contact corrosion from acidic gases in smoke and inductance of stray capacitance are less important contributors to system upset. Transmission line coupling was increased because the smoke acted as a conductive layer between the lines. Permanent circuit damage was not obvious in the 24 hr of circuit monitoring. Test results also show that polyurethane, parylene, and acrylic conformal coatings are more effective in protecting against smoke than epoxy or silicone. Common-sense mitigation measures are discussed. Unfortunately the authors are a long way from standard tests for smoke exposure that capture the variations in smoke exposure possible in an actual fire.« less

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.

High-performance flexible all-solid-state supercapacitors based on densely-packed graphene/polypyrrole nanoparticle papers

NASA Astrophysics Data System (ADS)

Yang, Chao; Zhang, Liling; Hu, Nantao; Yang, Zhi; Wei, Hao; Wang, Yanyan; Zhang, Yafei

2016-11-01

Graphene-based all-solid-state supercapacitors (ASSSCs) have received increasing attention. It's a great challenge to fabricate high-performance flexible solid-state supercapacitors with high areal and volumetric energy storage capability, superior electron and ion conductivity, robust mechanical flexibility, as well as long term stability. Herein, we report a facile method to fabricate flexible ASSSCs based on densely-packed reduced graphene oxide (rGO)/polypyrrole nanoparticle (PPy NP) hybrid papers with a sandwich framework, which consists of well-separated and continuously-aligned rGO sheets. The incorporation of PPy NPs not only provides pseudocapacitance but also facilitates the infiltration of gel electrolyte. The assembled ASSSCs possess maximum areal and volumetric specific capacitances of 477 mF/cm2 and 94.9 F/cm3 at 0.5 mA/cm2. They also exhibit little capacitance deviation under different bending states, excellent cycling stability, small leakage current and low self-discharge characteristics. Additionally, the maximum areal and volumetric energy densities of 132.5 μWh/cm2 and 26.4 mWh/cm3 are achieved, which indicate that this hybrid paper is a promising candidate for high-performance flexible energy storage devices.

Ultrathin ZnO interfacial passivation layer for atomic layer deposited ZrO2 dielectric on the p-In0.2Ga0.8As substrate

NASA Astrophysics Data System (ADS)

Liu, Chen; Lü, Hongliang; Yang, Tong; Zhang, Yuming; Zhang, Yimen; Liu, Dong; Ma, Zhenqiang; Yu, Weijian; Guo, Lixin

2018-06-01

Interfacial and electrical properties were investigated on metal-oxidesemiconductor capacitors (MOSCAPs) fabricated with bilayer ZnO/ZrO2 films by atomic layer deposition (ALD) on p-In0.2Ga0.8As substrates. The ZnO passivated In0.2Ga0.8As MOSCAPs have exhibited significantly improved capacitance-voltage (C-V) characteristics with the suppressed "stretched out" effect, increased accumulation capacitance and reduced accumulation frequency dispersion as well as the lower gate leakage current. In addition, the interface trap density (Dit) estimated by the Terman method was decreased dramatically for ZnO passivated p-In0.2Ga0.8As. The inherent mechanism is attributed to the fact that an ultrathin ZnO IPL employed by ALD prior to ZrO2 dielectric deposition can effectively suppress the formation of defect-related low-k oxides and As-As dimers at the interface, thus effectively improving the interface quality by largely removing the border traps aligned near the valence band edge of the p-In0.2Ga0.8As substrate.

Self-Adhesive and Capacitive Carbon Nanotube-Based Electrode to Record Electroencephalograph Signals From the Hairy Scalp.

PubMed

Lee, Seung Min; Kim, Jeong Hun; Park, Cheolsoo; Hwang, Ji-Young; Hong, Joung Sook; Lee, Kwang Ho; Lee, Sang Hoon

2016-01-01

We fabricated a carbon nanotube (CNT)/adhesive polydimethylsiloxane (aPDMS) composite-based dry electroencephalograph (EEG) electrode for capacitive measuring of EEG signals. As research related to brain-computer interface applications has advanced, the presence of hairs on a patient's scalp has continued to present an obstacle to recorder EEG signals using dry electrodes. The CNT/aPDMS electrode developed here is elastic, highly conductive, self-adhesive, and capable of making conformal contact with and attaching to a hairy scalp. Onto the conductive disk, hundreds of conductive pillars coated with Parylene C insulation layer were fabricated. A CNT/aPDMS layer was attached on the disk to transmit biosignals to the pillar. The top of disk was designed to be solderable, which enables the electrode to connect with a variety of commercial EEG acquisition systems. The mechanical and electrical characteristics of the electrode were tested, and the performances of the electrodes were evaluated by recording EEGs, including alpha rhythms, auditory-evoked potentials, and steady-state visually-evoked potentials. The results revealed that the electrode provided a high signal-to-noise ratio with good tolerance for motion. Almost no leakage current was observed. Although preamplifiers with ultrahigh input impedance have been essential for previous capacitive electrodes, the EEGs were recorded here by directly connecting a commercially available EEG acquisition system to the electrode to yield high-quality signals comparable to those obtained using conventional wet electrodes.

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

An elevated source/drain-on-insulator structure to maximize the intrinsic performance of extremely scaled MOSFETs

NASA Astrophysics Data System (ADS)

Zhang, Zhikuan; Zhang, Shengdong; Feng, Chuguang; Chan, Mansun

2003-10-01

In this paper, a source/drain structure separated from the silicon substrate by oxide isolation is fabricated and studied. The source/drain diffusion regions are connected to the shallow source/drain extension through a smaller opening defined by a double spacer process. Experimental results indicate that the source/drain on insulator significantly reduces the parasitic capacitance. Further optimization by simulation indicates a reduction of series resistance and band-to-band drain leakage at off-state can be achieved in extremely scaled devices. Compared with the conventional planner source/drain structure, the reduction of parasitic capacitance and series resistance can be as much as 80% and 30% respectively.

Effects of substrate heating and post-deposition annealing on characteristics of thin MOCVD HfO2 films

NASA Astrophysics Data System (ADS)

Gopalan, Sundararaman; Ramesh, Sivaramakrishnan; Dutta, Shibesh; Virajit Garbhapu, Venkata

2018-02-01

It is well known that Hf-based dielectrics have replaced the traditional SiO2 and SiON as gate dielectric materials for conventional CMOS devices. By using thicker high-k materials such as HfO2 rather than ultra-thin SiO2, we can bring down leakage current densities in MOS devices to acceptable levels. HfO2 is also one of the potential candidates as a blocking dielectric for Flash memory applications for the same reason. In this study, effects of substrate heating and oxygen flow rate while depositing HfO2 thin films using CVD and effects of post deposition annealing on the physical and electrical characteristics of HfO2 thin films are presented. It was observed that substrate heating during deposition helps improve the density and electrical characteristics of the films. At higher substrate temperature, Vfb moved closer to zero and also resulted in significant reduction in hysteresis. Higher O2 flow rates may improve capacitance, but also results in slightly higher leakage. The effect of PDA depended on film thickness and O2 PDA improved characteristics only for thick films. For thinner films forming gas anneal resulted in better electrical characteristics.

Transparent and flexible capacitors based on nanolaminate Al2O3/TiO2/Al2O3.

PubMed

Zhang, Guozhen; Wu, Hao; Chen, Chao; Wang, Ti; Yue, Jin; Liu, Chang

2015-01-01

Transparent and flexible capacitors based on nanolaminate Al2O3/TiO2/Al2O3 dielectrics have been fabricated on indium tin oxide-coated polyethylene naphthalate substrates by atomic layer deposition. A capacitance density of 7.8 fF/μm(2) at 10 KHz was obtained, corresponding to a dielectric constant of 26.3. Moreover, a low leakage current density of 3.9 × 10(-8) A/cm(2) at 1 V has been realized. Bending test shows that the capacitors have better performances in concave conditions than in convex conditions. The capacitors exhibit an average optical transmittance of about 70% in visible range and thus open the door for applications in transparent and flexible integrated circuits.

A Low noise, Non-contact Capacitive Cardiac Sensor*

PubMed Central

Peng, GuoChen; Bocko, Mark F.

2014-01-01

The development of sensitive, non-contact electric field sensors to measure weak bioelectric signals will be useful for the development of a number of unobtrusive health sensors. In this paper we summarize our recent work on a number of specific challenges in the development of non-contact ECG sensors. First, we considered the design of a low noise sensor preamplifier. We have adapted circuit designs that incorporate a double feedback loop to cancel the input transistor leakage current while providing stable operation, fast settling time and good low frequency response without the need for ultrahigh value resistors. The measured input referred noise of the preamplifier in the frequency band 0.05–100 Hz is 0.76 μVrms, which is several times lower than existing ECG preamplifiers. PMID:23367049

Thermally tunable VO2-SiO2 nanocomposite thin-film capacitors

NASA Astrophysics Data System (ADS)

Sun, Yifei; Narayanachari, K. V. L. V.; Wan, Chenghao; Sun, Xing; Wang, Haiyan; Cooley, Kayla A.; Mohney, Suzanne E.; White, Doug; Duwel, Amy; Kats, Mikhail A.; Ramanathan, Shriram

2018-03-01

We present a study of co-sputtered VO2-SiO2 nanocomposite dielectric thin-film media possessing continuous temperature tunability of the dielectric constant. The smooth thermal tunability is a result of the insulator-metal transition in the VO2 inclusions dispersed within an insulating matrix. We present a detailed comparison of the dielectric characteristics of this nanocomposite with those of a VO2 control layer and of VO2/SiO2 laminate multilayers of comparable overall thickness. We demonstrated a nanocomposite capacitor that has a thermal capacitance tunability of ˜60% between 25 °C and 100 °C at 1 MHz, with low leakage current. Such thermally tunable capacitors could find potential use in applications such as sensing, thermal cloaks, and phase-change energy storage devices.

A low noise, non-contact capacitive cardiac sensor.

PubMed

Peng, GuoChen; Bocko, Mark F

2012-01-01

The development of sensitive, non-contact electric field sensors to measure weak bioelectric signals will be useful for the development of a number of unobtrusive health sensors. In this paper we summarize our recent work on a number of specific challenges in the development of non-contact ECG sensors. First, we considered the design of a low noise sensor preamplifier. We have adapted circuit designs that incorporate a double feedback loop to cancel the input transistor leakage current while providing stable operation, fast settling time and good low frequency response without the need for ultrahigh value resistors. The measured input referred noise of the preamplifier in the frequency band 0.05-100 Hz is 0.76 µV(rms), which is several times lower than existing ECG preamplifiers.

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.

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.

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

Kumar, S.; Dhar, A., E-mail: adhar@phy.iitkgp.ernet.in

Highlights: • Alternative to chemically crosslinking of PMMA to achieve low leakage in provided. • Effect of LiF in reducing gate leakage through the OFET device is studied. • Effect of gate leakage on transistor performance has been investigated. • Low voltage operable and low temperature processed n-channel OFETs were fabricated. - Abstract: We report low temperature processed, low voltage operable n-channel organic field effect transistors (OFETs) using N,N′-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C{sub 8}) organic semiconductor and poly(methylmethacrylate) (PMMA)/lithium fluoride (LiF) bilayer gate dielectric. We have studied the role of LiF buffer dielectric in effectively reducing the gate leakage through the device andmore » thus obtaining superior performance in contrast to the single layer PMMA dielectric devices. The bilayer OFET devices had a low threshold voltage (V{sub t}) of the order of 5.3 V. The typical values of saturation electron mobility (μ{sub s}), on/off ratio and inverse sub-threshold slope (S) for the range of devices made were estimated to be 2.8 × 10{sup −3} cm{sup 2}/V s, 385, and 3.8 V/decade respectively. Our work thus provides a potential substitution for much complicated process of chemically crosslinking PMMA to achieve low leakage, high capacitance, and thus low operating voltage OFETs.« less

Channel doping concentration and cell program state dependence on random telegraph noise spatial and statistical distribution in 30 nm NAND flash memory

NASA Astrophysics Data System (ADS)

Tomita, Toshihiro; Miyaji, Kousuke

2015-04-01

The dependence of spatial and statistical distribution of random telegraph noise (RTN) in a 30 nm NAND flash memory on channel doping concentration NA and cell program state Vth is comprehensively investigated using three-dimensional Monte Carlo device simulation considering random dopant fluctuation (RDF). It is found that single trap RTN amplitude ΔVth is larger at the center of the channel region in the NAND flash memory, which is closer to the jellium (uniform) doping results since NA is relatively low to suppress junction leakage current. In addition, ΔVth peak at the center of the channel decreases in the higher Vth state due to the current concentration at the shallow trench isolation (STI) edges induced by the high vertical electrical field through the fringing capacitance between the channel and control gate. In such cases, ΔVth distribution slope λ cannot be determined by only considering RDF and single trap.

HIGH-k GATE DIELECTRIC: AMORPHOUS Ta/La2O3 FILMS GROWN ON Si AT LOW PRESSURE

NASA Astrophysics Data System (ADS)

Bahari, Ali; Khorshidi, Zahra

2014-09-01

In the present study, Ta/La2O3 films (La2O3 doped with Ta2O5) as a gate dielectric were prepared using a sol-gel method at low pressure. Ta/La2O3 film has some hopeful properties as a gate dielectric of logic device. The structure and morphology of Ta/La2O3 films were studied using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Electrical properties of films were performed using capacitance-voltage (C-V) and current density-voltage (J-V) measurements. The optical bandgap of samples was studied by UV-visible optical absorbance measurement. The optical bandgap, Eopt, is determined from the absorbance spectra. The obtained results show that Ta/La2O3 film as a good gate dielectric has amorphous structure, good thermal stability, high dielectric constant (≈ 25), low leakage current and wide bandgap (≈ 4.7 eV).

Fabrication of Ta2O5/GeNx gate insulator stack for Ge metal-insulator-semiconductor structures by electron-cyclotron-resonance plasma nitridation and sputtering deposition techniques

NASA Astrophysics Data System (ADS)

Otani, Yohei; Itayama, Yasuhiro; Tanaka, Takuo; Fukuda, Yukio; Toyota, Hiroshi; Ono, Toshiro; Mitsui, Minoru; Nakagawa, Kiyokazu

2007-04-01

The authors have fabricated germanium (Ge) metal-insulator-semiconductor (MIS) structures with a 7-nm-thick tantalum pentaoxide (Ta2O5)/2-nm-thick germanium nitride (GeNx) gate insulator stack by electron-cyclotron-resonance plasma nitridation and sputtering deposition. They found that pure GeNx ultrathin layers can be formed by the direct plasma nitridation of the Ge surface without substrate heating. X-ray photoelectron spectroscopy revealed no oxidation of the GeNx layer after the Ta2O5 sputtering deposition. The fabricated MIS capacitor with a capacitance equivalent thickness of 4.3nm showed excellent leakage current characteristics. The interface trap density obtained by the modified conductance method was 4×1011cm-2eV-1 at the midgap.

Electrical characterization of glass, teflon, and tantalum capacitors at high temperatures

NASA Technical Reports Server (NTRS)

Hammoud, A. N.; Baumann, E. D.; Myers, I. T.; Overton, E.

1991-01-01

Dielectric materials and electrical components and devices employed in radiation fields and the space environment are often exposed to elevated temperatures among other things. Therefore, these systems must withstand the high temperature exposure while still providing good electrical and other functional properties. Experiments were carried out to evaluate glass, teflon, and tantalum capacitors for potential use in high temperature applications. The capacitors were characterized in terms of their capacitance and dielectric loss as a function of temperature up to 200 C. At a given temperature, these properties were obtained in a frequency range of 50 Hz to 100 kHz. The DC leakage current measurements were also performed in a temperature range from 20 to 200 C. The obtained results are discussed and conclusions are made concerning the suitability of the capacitors investigated for high temperature applications.

Evaluation of Capacitors at Cryogenic Temperatures for Space Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad; Gerber, Scott S.

1998-01-01

Advanced electronic systems designed for use in planetary exploration missions must operate efficiently and reliably under the extreme cold temperatures of deep space environment. In addition, spacecraft power electronics capable of cold temperature operation will greatly simplify the thermal management system by eliminating the need for heating units and associated equipment and thereby reduce the size and weight of the overall power system. In this study, film, mica, solid tantalum and electric double layer capacitors were evaluated as a function of temperature from room to liquid nitrogen in terms of their dielectric properties. These properties included capacitance stability and dielectric loss in the frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also performed on the capacitors. The results obtained are discussed and conclusions are made concerning the suitability of the capacitors investigated for low temperature applications.

Low Temperature Characterization of Ceramic and Film Power Capacitors

NASA Technical Reports Server (NTRS)

Hammoud, Ahmad; Overton, Eric

1996-01-01

Among the key requirements for advanced electronic systems is the ability to withstand harsh environments while maintaining reliable and efficient operation. Exposures to low temperature as well as high temperature constitute such stresses. Applications where low temperatures are encountered include deep space missions, medical imaging equipment, and cryogenic instrumentation. Efforts were taken to design and develop power capacitors capable of wide temperature operation. In this work, ceramic and film power capacitors were developed and characterized as a function of temperature from 20 C to -185 C in terms of their dielectric properties. These properties included capacitance stability and dielectric loss in the frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also performed on the capacitors. The manuscript presents the results that indicate good operational characteristic behavior and stability of the components tested at low temperatures.

Improving fatigue resistance of Pb(Zr,Ti)O3 thin films by using PbZrO3 buffer layers

NASA Astrophysics Data System (ADS)

Mensur Alkoy, Ebru; Uchiyama, Kiyoshi; Shiosaki, Tadashi; Alkoy, Sedat

2006-05-01

Ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin films with PbZrO3 (PZ) buffer layers were prepared on Pt(111)/Ti/SiO2/Si(100) substrates using a hybrid rf magnetron sputtering and sol-gel process. Texture of PZT films was found to depend on Pb content of PZ buffer layers. Buffered PZT films displayed comparable ferroelectric properties (2Pr=38-53 μC/cm2,2Ec=136-170 kV/cm) with unbuffered PZT. Asymmetric leakage current and fatigue behavior with superior fatigue resistance was observed in PZ buffered PZT compared to unbuffered films. PZ buffer layers were found to affect crystallization and texture of PZT, and act as a capacitive interface layer possibly blocking charge injection from electrodes.

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

Scaling Trends and Tradeoffs between Short Channel Effect and Channel Boosting Characteristics in Sub-20 nm Bulk/Silicon-on-Insulator NAND Flash Memory

NASA Astrophysics Data System (ADS)

Miyaji, Kousuke; Hung, Chinglin; Takeuchi, Ken

2012-04-01

The scaling trends and limitation in sub-20 nm a bulk and silicon-on-insulator (SOI) NAND flash memory is studied by the three-dimensional (3D) device simulation focusing on short channel effects (SCE), channel boost leakage and channel voltage boosting characteristics during the program-inhibit operation. Although increasing punch-through stopper doping concentration is effective for suppressing SCE in bulk NAND cells, the generation of junction leakage becomes serious. On the other hand, SCE can be suppressed by thinning the buried oxide (BOX) in SOI NAND cells. However, the boosted channel voltage decreases by the higher BOX capacitance. It is concluded that the scaling limitation is dominated by the junction leakage and channel boosting capability for bulk and SOI NAND flash cells, respectively, and the scaling limit is decreased to 9 nm using SOI NAND flash memory cells from 13 nm in bulk NAND flash memory cells.

Electrical characterization of thin nanoscale SiOx layers grown on plasma hydrogenated silicon

NASA Astrophysics Data System (ADS)

Halova, E.; Kojuharova, N.; Alexandrova, S.; Szekeres, A.

2018-03-01

We analyzed the electrical characteristics of MOS structures with a SiOx layer grown on Si treated in plasma without heating. The hysteresis effect observed indicates the presence of traps spatially distributed into the oxide near the interface. The shift and the shape of the curves reveal a small oxide charge and low leakage currents, i.e. a high-quality dielectric layer. The generalized C-V curve was generated by applying the two-frequency methods on the C-V and G-V characteristics at frequencies in the range from 1 kHz to 300 kHz and by accounting for the series resistance and the leakage through the oxide layer. The energy spectra of the interface traps were calculated by comparing the experimental and the ideal theoretical C-V curves. The spectra showed the presence of interface traps with localized energy levels in the Si bandgap. These conclusions correlate well with the results on this oxide’s mechanical stress level, composition and Si-O ring structure, as well as on the interfacial region composition, obtained by our previous detailed multi-angle spectral ellipsometric studies. The ellipsometric data and the capacitance in strong accumulation of the C-V curves were used to calculate the thickness and the dielectric constants of the oxide layers.

Reverse leakage current characteristics of InGaN/GaN multiple quantum well ultraviolet/blue/green light-emitting diodes

NASA Astrophysics Data System (ADS)

Zhou, Shengjun; Lv, Jiajiang; Wu, Yini; Zhang, Yuan; Zheng, Chenju; Liu, Sheng

2018-05-01

We investigated the reverse leakage current characteristics of InGaN/GaN multiple quantum well (MQW) near-ultraviolet (NUV)/blue/green light-emitting diodes (LEDs). Experimental results showed that the NUV LED has the smallest reverse leakage current whereas the green LED has the largest. The reason is that the number of defects increases with increasing nominal indium content in InGaN/GaN MQWs. The mechanism of the reverse leakage current was analyzed by temperature-dependent current–voltage measurement and capacitance–voltage measurement. The reverse leakage currents of NUV/blue/green LEDs show similar conduction mechanisms: at low temperatures, the reverse leakage current of these LEDs is attributed to variable-range hopping (VRH) conduction; at high temperatures, the reverse leakage current of these LEDs is attributed to nearest-neighbor hopping (NNH) conduction, which is enhanced by the Poole–Frenkel effect.

Effect of Post-HALT Annealing on Leakage Currents in Solid Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2010-01-01

Degradation of leakage currents is often observed during life testing of tantalum capacitors and is sometimes attributed to the field-induced crystallization in amorphous anodic tantalum pentoxide dielectrics. However, degradation of leakage currents and the possibility of annealing of degraded capacitors have not been investigated yet. In this work the effect of annealing after highly accelerated life testing (HALT) on leakage currents in various types of solid tantalum capacitors was analyzed. Variations of leakage currents with time during annealing at temperatures from 125 oC to 180 oC, thermally stimulated depolarization (TSD) currents, and I-V characteristics were measured to understand the conduction mechanism and the reason for current degradation. Annealing resulted in a gradual decrease of leakage currents and restored their initial values. Repeat HALT after annealing resulted in reproducible degradation of leakage currents. The observed results are explained based on ionic charge instability (drift/diffusion of oxygen vacancies) in the tantalum pentoxide dielectrics using a modified Schottky conduction mechanism.

Capacitively coupled and direct-current resistivity surveys of selected reaches of Cozad, Thirty-Mile, Orchard-Alfalfa, Kearney, and Outlet Canals in Nebraska, 2012-13

USGS Publications Warehouse

Hobza, Christopher M.; Burton, Bethany L.; Lucius, Jeffrey E.; Tompkins, Ryan E.

2014-01-01

Understanding the spatial characteristics of leakage from canals is critical to effectively managing and utilizing water resources for irrigation and hydroelectric purposes. Canal leakage in some parts of Nebraska is the primary source of water for groundwater recharge and helps maintain the base flow of streams. Because surface-water supplies depend on the streamflow of the Platte River and the available water stored in upstream reservoirs, water managers seek to minimize conveyance losses, which can include canal leakage. The U.S. Geological Survey, in cooperation with the Central Platte Natural Resources District and Nebraska Public Power District, used capacitively coupled (CC) and direct-current (DC) resistivity techniques for continuous resistivity profiling to map near-surface lithologies near and underlying the Cozad, Thirty-Mile, Orchard-Alfalfa, Kearney, and Outlet Canals. Approximately 84 kilometers (km) of CC-resistivity data were collected along the five canals. The CC-resistivity data were compared with results from continuous sediment cores and electrical conductivity logs. Generally, the highest resistivities were recorded at the upstream reaches of the Cozad, Thirty-Mile, and Orchard-Alfalfa canals where flood-plain deposits of silt and clay mantle coarser channel deposits of sand and gravel. The finer grained deposits gradually thicken with increasing distance away from the Platte River. Consequently, for many surveyed reaches the thickness of fine-grained deposits exceeded the 8-meter depth of investigation. A detailed geophysical investigation along a 5-km reach of the Outlet Canal southwest of North Platte, Nebraska, used CC and DC resistivity to examine the condition of a compacted-core bank structure and characterized other potential controls on areas of focused seepage. CC-resistivity data, collected along the 5-km study reach, were compared with continuous sediment cores and DC-resistivity data collected near a selected seep near Outlet Canal mile post 15.55 along 5 separate profiles. DC-resistivity results were compared to a schematic cross section of the Outlet Canal north embankment that include the original surfaces and modifications to the compacted-core bank structure. Along the canal road south line, there is a transition from high resistivity at land surface to much lower resistivity near the estimated depth of the northern slope of the original compacted-core bank; however, the surveyed elevation of the water surface in the canal also is at this elevation. Along the canal road north line, there is a transition from high resistivity near land surface to lower resistivity at depth. Although the transition is rapid near the estimated depth of the first-modified bank slope, it also is coincident with the groundwater level measured in piezometer PZ-4. Currently (2013), it is unknown if the indicated changes in resistivity at these elevations was the effect of saturation of the underlying sediments or caused by the compacted-core bank.

Leakage current conduction in metal gate junctionless nanowire transistors

NASA Astrophysics Data System (ADS)

Oproglidis, T. A.; Karatsori, T. A.; Barraud, S.; Ghibaudo, G.; Dimitriadis, C. A.

2017-05-01

In this paper, the experimental off-state drain leakage current behavior is systematically explored in n- and p-channel junctionless nanowire transistors with HfSiON/TiN/p+-polysilicon gate stack. The analysis of the drain leakage current is based on experimental data of the gate leakage current. It has been shown that the off-state drain leakage current in n-channel devices is negligible, whereas in p-channel devices it is significant and dramatically increases with drain voltage. The overall results indicate that the off-state drain leakage current in p-channel devices is mainly due to trap-assisted Fowler-Nordheim tunneling of electrons through the gate oxide of electrons from the metal gate to the silicon layer near the drain region.

Low-voltage organic thin film transistors (OTFTs) using crosslinked polyvinyl alcohol (PVA)/neodymium oxide (Nd2O3) bilayer gate dielectrics

NASA Astrophysics Data System (ADS)

Khound, Sagarika; Sarma, Ranjit

2018-01-01

We have reported here on the design, processing and dielectric properties of pentacene-based organic thin film transitors (OTFTs) with a bilayer gate dilectrics of crosslinked PVA/Nd2O3 which enables low-voltage organic thin film operations. The dielectric characteristics of PVA/Nd2O3 bilayer films are studied by capacitance-voltage ( C- V) and current-voltage ( I- V) curves in the metal-insulator-metal (MIM) structure. We have analysed the output electrical responses and transfer characteristics of the OTFT devices to determine their performance of OTFT parameters. The mobility of 0.94 cm2/Vs, the threshold voltage of - 2.8 V, the current on-off ratio of 6.2 × 105, the subthreshold slope of 0.61 V/decade are evaluated. Low leakage current of the device is observed from current density-electric field ( J- E) curve. The structure and the morphology of the device are studied using X-ray diffraction (XRD) and atomic force microscope (AFM), respectively. The study demonstrates an effective way to realize low-voltage, high-performance OTFTs at low cost.

On electrical and interfacial properties of iron and platinum Schottky barrier diodes on (111) n-type Si0.65Ge0.35

NASA Astrophysics Data System (ADS)

Hamri, D.; Teffahi, A.; Djeghlouf, A.; Chalabi, D.; Saidane, A.

2018-04-01

Current-voltage (I-V), capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G/ω-V-f) characteristics of Molecular Beam Epitaxy (MBE)-deposited Fe/n-Si0.65Ge0.35 (FM1) and Pt/n-Si0.65Ge0.35(PM2) (111) orientated Schottky barrier diodes (SBDs) have been investigated at room-temperature. Barrier height (ΦB0), ideality factor (n) and series resistance (RS) were extracted. Dominant current conduction mechanisms were determined. They revealed that Poole-Frenkel-type conduction mechanism dominated reverse current. Differences in shunt resistance confirmed the difference found in leakage current. Under forward bias, quasi-ohmic conduction is found at low voltage regions and space charge-limited conduction (SCLC) at higher voltage regions for both SBDs. Density of interface states (NSS) indicated a difference in interface reactivity. Distribution profiles of series resistance (RS) with bias gives a peak in depletion region at low-frequencies that disappears with increasing frequencies. These results show that interface states density and series resistance of Schottky diodes are important parameters that strongly influence electrical properties of FM1 and PM2 structures.

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.

Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2014-01-01

Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2016-01-01

Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

Bivariate quadratic method in quantifying the differential capacitance and energy capacity of supercapacitors under high current operation

NASA Astrophysics Data System (ADS)

Goh, Chin-Teng; Cruden, Andrew

2014-11-01

Capacitance and resistance are the fundamental electrical parameters used to evaluate the electrical characteristics of a supercapacitor, namely the dynamic voltage response, energy capacity, state of charge and health condition. In the British Standards EN62391 and EN62576, the constant capacitance method can be further improved with a differential capacitance that more accurately describes the dynamic voltage response of supercapacitors. This paper presents a novel bivariate quadratic based method to model the dynamic voltage response of supercapacitors under high current charge-discharge cycling, and to enable the derivation of the differential capacitance and energy capacity directly from terminal measurements, i.e. voltage and current, rather than from multiple pulsed-current or excitation signal tests across different bias levels. The estimation results the author achieves are in close agreement with experimental measurements, within a relative error of 0.2%, at various high current levels (25-200 A), more accurate than the constant capacitance method (4-7%). The archival value of this paper is the introduction of an improved quantification method for the electrical characteristics of supercapacitors, and the disclosure of the distinct properties of supercapacitors: the nonlinear capacitance-voltage characteristic, capacitance variation between charging and discharging, and distribution of energy capacity across the operating voltage window.

Growth of Pb(Ti,Zr)O 3 thin films by metal-organic molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Avrutin, V.; Liu, H. Y.; Izyumskaya, N.; Xiao, B.; Özgür, Ü.; Morkoç, H.

2009-02-01

Single-crystal Pb(Zr xTi 1-x)O 3 thin films have been grown on (0 0 1) SrTiO 3 and SrTiO 3:Nb substrates by molecular beam epitaxy using metal-organic source of Zr and two different sources of reactive oxygen—RF plasma and hydrogen-peroxide sources. The same growth modes and comparable structural properties were observed for the films grown with both oxygen sources, while the plasma source allowed higher growth rates. The films with x up to 0.4 were single phase, while attempts to increase x beyond gave rise to the ZrO 2 second phase. The effects of growth conditions on growth modes, Zr incorporation, and phase composition of the Pb(Zr xTi 1-x)O 3 films are discussed. Electrical and ferroelectric properties of the Pb(Zr xTi 1-x)O 3 films of ~100 nm in thickness grown on SrTiO 3:Nb were studied using current-voltage, capacitance-voltage, and polarization-field measurements. The single-phase films show low leakage currents and large breakdown fields, while the values of remanent polarization are low (around 5 μC/cm 2). It was found that, at high sweep fields, the contribution of the leakage current to the apparent values of remanent polarization can be large, even for the films with large electrical resistivity (˜10 8-10 9 Ω cm at an electric filed of 1 MV/cm). The measured dielectric constant ranges from 410 to 260 for Pb(Zr 0.33Ti 0.67)O 3 and from 313 to 213 for Pb(Zr 0.2Ti 0.8)O 3 in the frequency range from 100 to 1 MHz.

Nanoscale imaging of the photoresponse in PN junctions of InGaAs infrared detector

PubMed Central

Xia, Hui; Li, Tian-Xin; Tang, Heng-Jing; Zhu, Liang; Li, Xue; Gong, Hai-Mei; Lu, Wei

2016-01-01

Electronic layout, such as distributions of charge carriers and electric field, in PN junction is determinant for the photovoltaic devices to realize their functionality. Considerable efforts have been dedicated to the carrier profiling of this specific region with Scanning Probe Microscope, yet reliable analysis was impeded by the difficulty in resolving carriers with high mobility and the unclear surface effect, particularly on compound semiconductors. Here we realize nanometer Scanning Capacitance Microscopic study on the cross-section of InGaAs/InP photodetctors with the featured dC/dV layout of PN junction unveiled for the first time. It enables us to probe the photo-excited minority carriers in junction region and diagnose the performance deficiency of the diode devices. This work provides an illuminating insight into the PN junction for assessing its basic capability of harvesting photo-carriers as well as blocking leakage current in nanoscopic scale. PMID:26892069

Radiation damage effects by electrons, protons, and neutrons in Si/Li/ detectors.

NASA Technical Reports Server (NTRS)

Liu, Y. M.; Coleman, J. A.

1972-01-01

The degradation in performance of lithium-compensated silicon nuclear particle detectors induced by irradiation at room temperature with 0.6-MeV and 1.5-MeV electrons, 1.9-MeV protons, and fast neutrons from a plutonium-beryllium source has been investigated. With increasing fluence, the irradiations produced an increase of detector leakage current, noise, capacitance, and a degradation in the performance of the detector as a charged-particle energy spectrometer. Following the irradiations, annealing effects were observed when the detectors were reverse-biased at their recommended operating voltages. Upon removal of bias, a continuous degradation of detector performance characteristics occurred. Detectors which had been damaged by electrons and protons exhibited a stabilization in their characteristics within two weeks after irradiation, whereas detectors damaged by neutrons had a continuous degradation of performance over a period of several months.

Improved interfacial and electrical properties of atomic layer deposition HfO2 films on Ge with La2O3 passivation

NASA Astrophysics Data System (ADS)

Li, Xue-Fei; Liu, Xiao-Jie; Cao, Yan-Qiang; Li, Ai-Dong; Li, Hui; Wu, Di

2013-01-01

We report the characteristics of HfO2 films deposited on Ge substrates with and without La2O3 passivation at 250 °C by atomic layer deposition (ALD) using La[N(SiMe3)2]3 and Hf[N(CH3)(C2H5)]4 as the precursors. The HfO2 is observed to form defective HfGeOx at its interface during 500 °C postdeposition annealing. The insertion of an ultrathin La2O3 interfacial passivation layer effectively prevents the Ge outdiffusion and improves interfacial and electrical properties. Capacitance equivalent thickness (CET) of 1.35 nm with leakage current density JA of 8.3 × 10-4 A/cm2 at Vg = 1 V is achieved for the HfO2/La2O3 gate stacks on Ge substrates.

Electron-beam irradiation-induced gate oxide degradation

NASA Astrophysics Data System (ADS)

Cho, Byung Jin; Chong, Pei Fen; Chor, Eng Fong; Joo, Moon Sig; Yeo, In Seok

2000-12-01

Gate oxide degradation induced by electron-beam irradiation has been studied. A large increase in the low-field excess leakage current was observed on irradiated oxides and this was very similar to electrical stress-induced leakage currents. Unlike conventional electrical stress-induced leakage currents, however, electron-beam induced leakage currents exhibit a power law relationship with fluency without any signs of saturation. It has also been found that the electron-beam neither accelerates nor initiates quasibreakdown of the ultrathin gate oxide. Therefore, the traps generated by electron-beam irradiation do not contribute to quasibreakdown, only to the leakage current.

Enhanced ground bounce noise reduction in a low-leakage CMOS multiplier

NASA Astrophysics Data System (ADS)

Verma, Bipin Kumar; Akashe, Shyam; Sharma, Sanjay

2015-09-01

In this paper, various parameters are used to reduce leakage power, leakage current and noise margin of circuits to enhance their performance. A multiplier is proposed with low-leakage current and low ground bounce noise for the microprocessor, digital signal processors (DSP) and graphics engines. The ground bounce noise problem appears when a conventional power-gating circuit transits from sleep-to-active mode. This paper discusses a reduction in leakage current in the stacking power-gating technique by three modes - sleep, active and sleep-to-active. The simulation results are performed on a 4 × 4 carry-save multiplier for leakage current, active power, leakage power and ground bounce noise, and comparison made for different nanoscales. Ground bounce noise is limited to 90%. The leakage current of the circuit is decimated up to 80% and the active power is reduced to 31%. We performed simulations using cadence virtuoso 180 and 45 nm at room temperature at various supply voltages.

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…

Electrokinetically driven active micro-mixers utilizing zeta potential variation induced by field effect

NASA Astrophysics Data System (ADS)

Lee, Chia-Yen; Lee, Gwo-Bin; Fu, Lung-Ming; Lee, Kuo-Hoong; Yang, Ruey-Jen

2004-10-01

This paper presents a new electrokinetically driven active micro-mixer which uses localized capacitance effects to induce zeta potential variations along the surface of silica-based microchannels. The mixer is fabricated by etching bulk flow and shielding electrode channels into glass substrates and then depositing Au/Cr thin films within the latter to form capacitor electrodes, which establish localized zeta potential variations near the electrical double layer (EDL) region of the electroosmotic flow (EOF) within the microchannels. The potential variations induce flow velocity changes within a homogeneous fluid and a rapid mixing effect if an alternating electric field is provided. The current experimental data confirm that the fluid velocity can be actively controlled by using the capacitance effect of the buried shielding electrodes to vary the zeta potential along the channel walls. While compared with commonly used planar electrodes across the microchannels, the buried shielding electrodes prevent current leakage caused by bad bonding and allow direct optical observation during operation. It also shows that the buried shielding electrodes can significantly induce the field effect, resulting in higher variations of zeta potential. Computational fluid dynamic simulations are also used to study the fluid characteristics of the developed active mixers. The numerical and experimental results demonstrate that the developed microfluidic device permits a high degree of control over the fluid flow and an efficient mixing effect. Moreover, the developed device could be used as a pumping device as well. The development of the active electrokinetically driven micro-mixer could be crucial for micro-total-analysis-systems.

Characterization of gallium arsenide X-ray mesa p-i-n photodiodes at room temperature

NASA Astrophysics Data System (ADS)

Lioliou, G.; Meng, X.; Ng, J. S.; Barnett, A. M.

2016-03-01

Two GaAs mesa p+-i-n+ photodiodes intended for photon counting X-ray spectroscopy, having an i layer thickness of 7 μm and diameter of 200 μm, have been characterized electrically, for their responsivity at the wavelength range 580 nm to 980 nm and one of them for its performance at detection of soft X-rays, at room temperature. Dark current and capacitance measurements as a function of applied forward and reverse bias are presented. The results show low leakage current densities, in the range of nA/cm2 at the maximum internal electric field (22 kV/cm). The unintentional doping concentration of the i layer, calculated from capacitance measurements, was found to be <1014 cm-3. Photocurrent measurements were performed under visible and near infrared light illumination for both diodes. The analysis of these measurements suggests the presence of a non-active (dead) layer (0.16 μm thickness) at the p+ side top contact interface, where the photogenerated carriers do not contribute to the photocurrent, possibly due to recombination. One of the diodes, D1, was also characterized as detector for room temperature photon counting X-ray spectroscopy; the best energy resolution achieved (FWHM) at 5.9 keV was 745 eV. The noise analysis of the system, based on spectra obtained at different shaping times and applied reverse biases, showed that the dominant source of noise is the dielectric noise. It was also calculated that there was at least (165±24) eV charge trapping noise at 0 V.

49 CFR 236.735 - Current, leakage.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Current, leakage. A stray electric current of relatively small value which flows through or across the...

49 CFR 236.735 - Current, leakage.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Current, leakage. A stray electric current of relatively small value which flows through or across the... 49 Transportation 4 2011-10-01 2011-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION...

49 CFR 236.735 - Current, leakage.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Current, leakage. A stray electric current of relatively small value which flows through or across the... 49 Transportation 4 2014-10-01 2014-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION...

49 CFR 236.735 - Current, leakage.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Current, leakage. A stray electric current of relatively small value which flows through or across the... 49 Transportation 4 2013-10-01 2013-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION...

49 CFR 236.735 - Current, leakage.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Current, leakage. A stray electric current of relatively small value which flows through or across the... 49 Transportation 4 2012-10-01 2012-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION...

Suppression of TFT leakage current effect on active matrix displays by employing a new circular switch

NASA Astrophysics Data System (ADS)

Lee, Jae-Hoon; Park, Hyun-Sang; Jeon, Jae-Hong; Han, Min-Koo

2008-03-01

We have proposed a new poly-Si TFT pixel, which can suppress TFT leakage current effect on active matrix organic diode (AMOLED) displays, by employing a new circular switching TFT and additional signal line for compensating the leakage current. When the leakage current of switching TFT is increased, the VGS of the current driving TFT in the proposed pixel is not altered by the variable data voltages due to the circular switching TFT. Our simulation results show that OLED current variation of the proposed pixel can be suppressed less than 3%, while that of conventional pixel exceeds 30%. The proposed pixel may be suitable to suppress the leakage current effect on AMOLED display.

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

Zhu, Bao; Liu, Wen-Jun; Wei, Lei

Excellent voltage linearity of metal-insulator-metal (MIM) capacitors is highly required for next generation radio frequency integration circuits. In this work, employing atomic layer deposition technique, we demonstrated how the voltage linearity of MIM capacitors was modulated by adding different thickness of SiO{sub 2} layer to the nano-stack of Al{sub 2}O{sub 3}/ZrO{sub 2}. It was found that the quadratic voltage coefficient of capacitance (α) can be effectively reduced from 1279 to −75 ppm/V{sup 2} with increasing the thickness of SiO{sub 2} from zero to 4 nm, which is more powerful than increasing the thickness of ZrO{sub 2} in the Al{sub 2}O{sub 3}/ZrO{sub 2}more » stack. This is attributed to counteraction between the positive α for Al{sub 2}O{sub 3}/ZrO{sub 2} and the negative one for SiO{sub 2} in the MIM capacitors with Al{sub 2}O{sub 3}/ZrO{sub 2}/SiO{sub 2} stacks. Interestingly, voltage-polarity dependent conduction behaviors in the MIM capacitors were observed. For electron bottom-injection, the addition of SiO{sub 2} obviously suppressed the leakage current; however, it abnormally increased the leakage current for electron top-injection. These are ascribed to the co-existence of shallow and deep traps in ZrO{sub 2}, and the former is in favor of the field-assisted tunnelling conduction and the latter contributes to the trap-assisted tunnelling process. The above findings will be beneficial to device design and process optimization for high performance MIM capacitors.« less

Impact of process parameters on the structural and electrical properties of metal/PZT/Al2O3/silicon gate stack for non-volatile memory applications

NASA Astrophysics Data System (ADS)

Singh, Prashant; Jha, Rajesh Kumar; Singh, Rajat Kumar; Singh, B. R.

2018-02-01

In this paper, we present the structural and electrical properties of the Al2O3 buffer layer on non-volatile memory behavior using Metal/PZT/Al2O3/Silicon structures. Metal/PZT/Silicon and Metal/Al2O3/Silicon structures were also fabricated and characterized to obtain capacitance and leakage current parameters. Lead zirconate titanate (PZT::35:65) and Al2O3 films were deposited by sputtering on the silicon substrate. Memory window, PUND, endurance, breakdown voltage, effective charges, flat-band voltage and leakage current density parameters were measured and the effects of process parameters on the structural and electrical characteristics were investigated. X-ray data show dominant (110) tetragonal phase of the PZT film, which crystallizes at 500 °C. The sputtered Al2O3 film annealed at different temperatures show dominant (312) orientation and amorphous nature at 425 °C. Multiple angle laser ellipsometric analysis reveals the temperature dependence of PZT film refractive index and extinction coefficient. Electrical characterization shows the maximum memory window of 3.9 V and breakdown voltage of 25 V for the Metal/Ferroelectric/Silicon (MFeS) structures annealed at 500 °C. With 10 nm Al2O3 layer in the Metal/Ferroelectric/Insulator/Silicon (MFeIS) structure, the memory window and breakdown voltage was improved to 7.21 and 35 V, respectively. Such structures show high endurance with no significant reduction polarization charge for upto 2.2 × 109 iteration cycles.

Ionic currents in the guinea-pig taenia coli.

PubMed Central

Inomata, H; Kao, C Y

1976-01-01

Short segments of portions of taenia coli of the guinea-pig averaging 54 mum X 219 mum X ca. 200 mum have been studied by a double sucrose-gap voltage-clamp technique. 2. The average total capacitance was 0-4 muF, corresponding to approximately 10(4) cells, if a specific membrane capacitance of 3 muF/cm2 were assumed. 3. A significant resistance, averaging 11-4omega, was in series with the membrane, and seriously limited the accuracy of the voltage control possible. 4. On depolarization, an early transient inward current was followed by a late maintained outwary current. 5. The late current was carried mainly by K+, because its direction could be reversed if the preparation were first depolarized in isotonic K2SO4 and held back to the original resting potential. 6. After appropriate corrections for residual capacitative and leakage currents, a reversal potential for the late current (Eb) was determined to be 15-20 mV more negative than the natural resting potential. It was not affected by the amplitude or the duration of the activating voltage step, but could be changed by prolonged applications of holding current. 7. At rest, the ratio of PNa:PK was 0-16:1; for Eb it was 0-05:1. 8. The reversal potential for the transient early inward current (Ea) averaged 22 mV in Krebs-bicarbonate solution, but was shifted to about 35 mV when the late current was first suppressed with tetraethylammonium ion. The shift suggested that there was some overlap of the early and late currents. 9. Reduction of [Na+]o to 50% of normal, or replacement of all Na+ with dimethyldiethanol ammonium ion and choline ion, failed to cause any significant shifts in the reversal potential of the early current or reduce the magnitude of the early current. 10. Reduction of [Ca2+]o to 0-25 or 0-1 of the normal caused shifts of the Ea toward the negative and reductions in the early current. These changes can occur without changes in the maximum chord conductance of the early current, such as might happen in ordinary Krebs-bicarbonate solution, or in preparations which had been depolarized by prior treatment with isotonic K2SO4 and then held back to the original membrane voltage. 11. Increase of [Ca2+]o to 5 times normal increased the early inward current, and the maximum chord conductances of the early and late currents, but did not shift the Ea. 12. In preparations pretreated with TEA, increasing [Ca2+]o to 5 times normal shifted Ea toward 45 mV. 13. The various observations are interpreted to mean that the early current in the taenia coli is carried principally by influx of Ca2+, and not by Na+. PMID:1255524

Leakage current evaluation for pn junctions formed in DC and RF MeV ion implanted wells

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

Yanagisawa, Yasunobu; Honda, Mitsuharu; Ogasawara, Makota

1996-12-31

The leakage current of pn junctions formed in DC and RF MeV implanted wells have been evaluated. There is no substantial difference in the leakage current levels between the continuous and pulsive beam implantations. However, the leakage current, so called diffusion current, for RF implanted wells is slightly higher than that for DC implanted wells on some condition. This suggests a possibility that relatively higher density of residual defects remains in the case of RIF implant.

Fabrication and characterization of Al{sub 2}O{sub 3} /Si composite nanodome structures for high efficiency crystalline Si thin film solar cells

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

Zhang, Ruiying, E-mail: ryzhang2008@sinano.ac.cn; State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 China; Zhu, Jian

2015-12-15

We report on our fabrication and characterization of Al{sub 2}O{sub 3}/Si composite nanodome (CND) structures, which is composed of Si nanodome structures with a conformal cladding Al{sub 2}O{sub 3} layer to evaluate its optical and electrical performance when it is applied to thin film solar cells. It has been observed that by application of Al{sub 2}O{sub 3}thin film coating using atomic layer deposition (ALD) to the Si nanodome structures, both optical and electrical performances are greatly improved. The reflectivity of less than 3% over the wavelength range of from 200 nm to 2000 nm at an incident angle from 0°more » to 45° is achieved when the Al{sub 2}O{sub 3} film is 90 nm thick. The ultimate efficiency of around 27% is obtained on the CND textured 2 μm-thick Si solar cells, which is compared to the efficiency of around 25.75% and 15% for the 2 μm-thick Si nanodome surface-decorated and planar samples respectively. Electrical characterization was made by using CND-decorated MOS devices to measure device’s leakage current and capacitance dispersion. It is found the electrical performance is sensitive to the thickness of the Al{sub 2}O{sub 3} film, and the performance is remarkably improved when the dielectric layer thickness is 90 nm thick. The leakage current, which is less than 4x10{sup −9} A/cm{sup 2} over voltage range of from -3 V to 3 V, is reduced by several orders of magnitude. C-V measurements also shows as small as 0.3% of variation in the capacitance over the frequency range from 10 kHz to 500 kHz, which is a strong indication of surface states being fully passivated. TEM examination of CND-decorated samples also reveals the occurrence of SiO{sub x} layer formed between the interface of Si and the Al{sub 2}O{sub 3} film, which is thin enough that ensures the presence of field-effect passivation, From our theoretical and experimental study, we believe Al{sub 2}O{sub 3} coated CND structures is a truly viable approach to achieving higher device efficiency.« less

Ionizing radiation effects on electrical and reliability characteristics of sputtered Ta2O5/Si interface

NASA Astrophysics Data System (ADS)

Rao, Ashwath; Verma, Ankita; Singh, B. R.

2015-06-01

This paper describes the effect of ionizing radiation on the interface properties of Al/Ta2O5/Si metal oxide semiconductor (MOS) capacitors using capacitance-voltage (C-V) and current-voltage (I-V) characteristics. The devices were irradiated with X-rays at different doses ranging from 100 rad to 1 Mrad. The leakage behavior, which is an important parameter for memory applications of Al/Ta2O5/Si MOS capacitors, along with interface properties such as effective oxide charges and interface trap density with and without irradiation has been investigated. Lower accumulation capacitance and shift in flat band voltage toward negative value were observed in annealed devices after exposure to radiation. The increase in interfacial oxide layer thickness after irradiation was confirmed by Rutherford Back Scattering measurement. The effect of post-deposition annealing on the electrical behavior of Ta2O5 MOS capacitors was also investigated. Improved electrical and interface properties were obtained for samples deposited in N2 ambient. The density of interface trap states (Dit) at Ta2O5/Si interface sputtered in pure argon ambient was higher compared to samples reactively sputtered in nitrogen-containing plasma. Our results show that reactive sputtering in nitrogen-containing plasma is a promising approach to improve the radiation hardness of Ta2O5/Si MOS devices.

Direct current performance and current collapse in AlGaN/GaN insulated gate high-electron mobility transistors on Si (1 1 1) substrate with very thin SiO2 gate dielectric

NASA Astrophysics Data System (ADS)

Lachab, M.; Sultana, M.; Fatima, H.; Adivarahan, V.; Fareed, Q.; Khan, M. A.

2012-12-01

This work reports on the dc performance of AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) grown on Si (1 1 1) substrate and the study of current dispersion in these devices using various widely adopted methods. The MOSHEMTs were fabricated using a very thin (4.2 nm) SiO2 film as the gate insulator and were subsequently passivated with about 30 nm thick Si3N4 layer. For devices with 2.5 µm long gates and a 4 µm drain-to-source spacing, the maximum saturation drain current density was 822 mA mm-1 at + 4 V gate bias and the peak external transconductance was ˜100 mS mm-1. Furthermore, the oxide layer successfully suppressed the drain and gate leakage currents with the subthreshold current and the gate diode current levels exceeding by more than three orders of magnitude the levels found in their Schottky gate counterparts. Capacitance-voltage and dynamic current-voltage measurements were carried out to assess the oxide quality as well as the devices’ surface properties after passivation. The efficacy of each of these characterization techniques to probe the presence of interface traps and oxide charge in the nitride-based transistors is also discussed.

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.

Capacitance-level/density monitor for fluidized-bed combustor

DOEpatents

Fasching, George E.; Utt, Carroll E.

1982-01-01

A multiple segment three-terminal type capacitance probe with segment selection, capacitance detection and compensation circuitry and read-out control for level/density measurements in a fluidized-bed vessel is provided. The probe is driven at a high excitation frequency of up to 50 kHz to sense quadrature (capacitive) current related to probe/vessel capacitance while being relatively insensitive to the resistance current component. Compensation circuitry is provided for generating a negative current of equal magnitude to cancel out only the resistive component current. Clock-operated control circuitry separately selects the probe segments in a predetermined order for detecting and storing this capacitance measurement. The selected segment acts as a guarded electrode and is connected to the read-out circuitry while all unselected segments are connected to the probe body, which together form the probe guard electrode. The selected probe segment capacitance component signal is directed to a corresponding segment channel sample and hold circuit dedicated to that segment to store the signal derived from that segment. This provides parallel outputs for display, computer input, etc., for the detected capacitance values. The rate of segment sampling may be varied to either monitor the dynamic density profile of the bed (high sampling rate) or monitor average bed characteristics (slower sampling rate).

Analysis of Schottky Barrier Parameters and Current Transport Properties of V/p-Type GaN Schottky Junction at Low Temperatures

NASA Astrophysics Data System (ADS)

Asha, B.; Harsha, Cirandur Sri; Padma, R.; Rajagopal Reddy, V.

2018-05-01

The electrical characteristics of a V/p-GaN Schottky junction have been investigated by current-voltage (I-V) and capacitance-voltage (C-V) characteristics under the assumption of the thermionic emission (TE) theory in the temperature range of 120-280 K with steps of 40 K. The zero-bias barrier height (ΦB0), ideality factor (n), flat-band barrier height (ΦBF) and series resistance (R S) values were evaluated and were found to be strongly temperature dependent. The results revealed that the ΦB0 values increase, whereas n, ΦFB and R S values decrease, with increasing temperature. Using the conventional Richardson plot, the mean barrier height (0.39 eV) and Richardson constant (8.10 × 10-10 Acm-2 K-2) were attained. The barrier height inhomogeneities were demonstrated by assuming a Gaussian distribution function. The interface state density (N SS) values were found to decrease with increasing temperature. The reverse leakage current mechanism of the V/p-GaN Schottky junction was found to be governed by Poole-Frenkel emission at all temperatures.

A mechanism of charge transport in electroluminescent structures consisting of porous silicon and single-crystal silicon

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

Evtukh, A. A., E-mail: dept_5@isp.kiev.ua; Kaganovich, E. B.; Manoilov, E. G.

2006-02-15

Electroluminescent structures that emit in the visible region of the spectrum and are based on porous silicon (por-Si) formed on the p-Si substrate electrolytically using an internal current source are fabricated. The photoluminescent and electroluminescent properties, as well as the current-and capacitance-voltage characteristics of the structures are studied. Electroluminescence is observed only if the forward bias voltage is applied to the structure; the electroluminescence mechanism is based on the injection and is related to the radiative recombination of electrons and holes in quantum-dimensional Si nanocrystals. The injection of holes is controlled by the condition of their accumulation in the space-chargemore » region of p-Si and by a comparatively low concentration of electronic states at the por-Si/p-Si interface. The charge transport in por-Si is caused by the direct tunneling of charge carriers between the quantum-mechanical levels, which is ensured by an appreciable number of quantum-dimensional Si nanocrystals. The leakage currents are low as a result of a small variance in the sizes of Si nanocrystals and the absence of comparatively large nanocrystals.« less

Leakage current reduction of vertical GaN junction barrier Schottky diodes using dual-anode process

NASA Astrophysics Data System (ADS)

Hayashida, Tetsuro; Nanjo, Takuma; Furukawa, Akihiko; Watahiki, Tatsuro; Yamamuka, Mikio

2018-04-01

The origin of the leakage current of a trench-type vertical GaN diode was discussed. We found that the edge of p-GaN is the main leakage spot. To reduce the reverse leakage current at the edge of p-GaN, a dual-anode process was proposed. As a result, the reverse blocking voltage defined at the leakage current density of 1 mA/cm2 of a vertical GaN junction barrier Schottky (JBS) diode was improved from 780 to 1,190 V, which is the highest value ever reported for vertical GaN Schottky barrier diodes (SBDs).

Current concepts of molecular events during bovine and porcine spermatozoa capacitation.

PubMed

Vadnais, Melissa L; Galantino-Homer, Hannah L; Althouse, Gary C

2007-01-01

Spermatozoa are required to undergo the processes of capacitation before they obtain fertilizing ability. The molecular changes of capacitation are still not fully understood. However, it is accepted that capacitation is a sequential process involving numerous physiological changes including destabilization of the plasma membrane, alterations of intracellular ion concentrations and membrane potential, and protein phosphorylation. There are no known morphological changes that occur to the spermatozoon during capacitation. The purpose of this review is to summarize current evidence on the molecular aspects of capacitation both in vivo and in vitro in bovine and porcine spermatozoa. For the purpose of this review, the process of sperm capacitation will encompass maturational events that occur following ejaculation up to binding to the zona pellucida, that triggers acrosomal exocytosis and initiates fertilization.

cGMP and cyclic nucleotide-gated channels participate in mouse sperm capacitation.

PubMed

Cisneros-Mejorado, Abraham; Sánchez Herrera, Daniel P

2012-01-20

During capacitation of mammalian sperm intracellular [Ca(2+)] and cyclic nucleotides increase, suggesting that CNG channels play a role in the physiology of sperm. Here we study the effect of capacitation, 8Br-cAMP (8-bromoadenosine 3',5'-cyclic monophosphate) and 8Br-cGMP (8-bromoguanosine 3',5'-cyclic monophosphate) on the macroscopic ionic currents of mouse sperm, finding the existence of different populations of sperm, in terms of the recorded current and its response to cyclic nucleotides. Our results show that capacitation and cyclic nucleotides increase the ionic current, having a differential sensitivity to cGMP (cyclic guanosine monophosphate) and cAMP (cyclic adenosine monophosphate). Using a specific inhibitor we determine the contribution of CNG channels to macroscopic current and capacitation. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Electrical and structural characterizations of crystallized Al{sub 2}O{sub 3}/GaN interfaces formed by in situ metalorganic chemical vapor deposition

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

Liu, X., E-mail: xliu@ece.ucsb.edu; Yeluri, R.; Kim, J.

2016-01-07

Al{sub 2}O{sub 3} films were grown in situ by metalorganic chemical vapor deposition at 900 °C on GaN of both Ga- and N-face polarities. High-resolution transmission electron microscopy revealed that the Al{sub 2}O{sub 3} films were crystalline and primarily γ-phase. The Al{sub 2}O{sub 3}/Ga-GaN and Al{sub 2}O{sub 3}/N-GaN interfaces were both atomically sharp, and the latter further exhibited a biatomic step feature. The corresponding current-voltage (J-V) characteristics were measured on a metal-Al{sub 2}O{sub 3}-semiconductor capacitor (MOSCAP) structure. The leakage current was very high when the Al{sub 2}O{sub 3} thickness was comparable with the size of the crystalline defects, but was suppressedmore » to the order of 1 × 10{sup −8} A/cm{sup 2} with larger Al{sub 2}O{sub 3} thicknesses. The interface states densities (D{sub it}) were measured on the same MOSCAPs by using combined ultraviolet (UV)-assisted capacitance-voltage (C-V), constant capacitance deep level transient spectroscopy (CC-DLTS), and constant capacitance deep level optical spectroscopy (CC-DLOS) techniques. The average D{sub it} measured by CC-DLTS and CC-DLOS were 6.6 × 10{sup 12} and 8.8 × 10{sup 12} cm{sup −2} eV{sup −1} for Al{sub 2}O{sub 3}/Ga-GaN and 8.6 × 10{sup 12} and 8.6 × 10{sup 12 }cm{sup −2} eV{sup −1} for Al{sub 2}O{sub 3}/N-GaN, respectively. The possible origins of the positive (negative) polarization compensation charges in Al{sub 2}O{sub 3}/Ga-GaN (Al{sub 2}O{sub 3}/N-GaN), including the filling of interface states and the existence of structure defects and impurities in the Al{sub 2}O{sub 3} layer, were discussed in accordance with the experimental results and relevant studies in the literature.« less

Preparation of etched tantalum semimicro capacitor stimulation electrodes.

PubMed

Robblee, L S; Kelliher, E M; Langmuir, M E; Vartanian, H; McHardy, J

1983-03-01

The ideal electrode for stimulation of the nervous system is one that will inject charge by purely capacitive processes. One approach is to exploit the type of metal-oxide combination used in electrolytic capacitors, e.g., Ta/Ta2O5. For this purpose, fine tantalum wire (0.25 mm diam) was etched electrolytically at constant current in a methanol solution of NH4Br containing 1.5 wt % H2O. Electrolytic etching produced a conical tip with a length of ca. 0.5 mm and shaft diameters ranging from 0.10 to 0.16 mm. The etched electrodes were anodized to 10 V (vs. SCE) in 0.1 vol % H3PO4. The capacitance values normalized to geometric area of etched electrodes ranged from 0.13 to 0.33 micro F mm-2. Comparison of these values to the capacitance of "smooth" tantalum anodized to 10 V (0.011 micro F mm-2) indicated that the degree of surface enhancement, or etch ratio, was 12-30. The surface roughness was confirmed by scanning electron microscopy studies which revealed an intricate array of irregularly shaped surface projections about 1-2 micrometers wide. The etched electrodes were capable of delivering 0.06-0.1 micro C of charge with 0.1 ms pulses at a pulse repetition rate of 400 Hz when operated at 50% of the anodization voltage. This quantity of charge corresponded to volumetric charge densities of 20-30 micro C mm-3 and area charge densities of 0.55-0.88 micro C mm-2. Charge storage was proportionately higher at higher fractional values of the formation voltage. Leakage currents at 5 V were ca. 2 nA. Neither long-term passive storage (1500 h) nor extended pulsing time (18 h) had a deleterious effect on electrode performance. The trend in electrical stimulation work is toward smaller electrodes. The procedures developed in this study should be particularly well-suited to the fabrication of even smaller electrodes because of the favorable electrical and geometric characteristics of the etched surface.

Analysis of reverse gate leakage mechanism of AlGaN/GaN HEMTs with N2 plasma surface treatment

NASA Astrophysics Data System (ADS)

Liu, Hui; Zhang, Zongjing; Luo, Weijun

2018-06-01

The mechanism of reverse gate leakage current of AlGaN/GaN HEMTs with two different surface treatment methods are studied by using C-V, temperature dependent I-V and theoretical analysis. At the lower reverse bias region (VR >- 3.5 V), the dominant leakage current mechanism of the device with N2 plasma surface treatment is the Poole-Frenkel emission current (PF), and Trap-Assisted Tunneling current (TAT) is the principal leakage current of the device which treated by HCl:H2O solution. At the higher reverse bias region (VR <- 3.5 V), both of the two samples show good agreement with the surface leakage mechanism. The leakage current of the device with N2 plasma surface treatment is one order of magnitude smaller than the device which treated by HCl:H2O solution. This is due to the recovery of Ga-N bond in N2 plasma surface treatment together with the reduction of the shallow traps in post-gate annealing (PGA) process. The measured results agree well with the theoretical calculations and demonstrate N2 plasma surface treatment can reduce the reverse leakage current of the AlGaN/GaN HEMTs.

Influence of thermal aging on AC leakage current in XLPE insulation

NASA Astrophysics Data System (ADS)

Geng, Pulong; Song, Jiancheng; Tian, Muqin; Lei, Zhipeng; Du, Yakun

2018-02-01

Cross-linked polyethylene (XLPE) has been widely used as cable insulation material because of its excellent dielectric properties, thermal stability and solvent resistance. To understand the influence of thermal aging on AC leakage current in XLPE insulation, all XLPE specimens were aged in oven in temperature range from 120 °C to 150 °C, and a series of tests were conducted on these XLPE specimens in different aging stages to measure the characteristic parameters, such as complex permittivity, leakage current and complex dielectric modulus. In the experiments, the effects of thermal aging, temperature and frequency on the AC leakage current in XLPE insulation were studied by analyzing complex dielectric constant and dielectric relaxation modulus spectrum, the change of relaxation peak and activation energy. It has been found that the active part of leakage current increases sharply with the increase of aging degree, and the test temperature and frequency have an influence on AC leakage current but the influence of test temperature is mainly reflected in the low frequency region. In addition, it has been shown by the experiments that the reactive part of leakage current exhibits a strong frequency dependent characteristic in the testing frequency range from 10-2 Hz to 105 Hz, but the influence of test temperature and thermal aging on it is relatively small.

NiCo2S4 nanosheet-decorated 3D, porous Ni film@Ni wire electrode materials for all solid-state asymmetric supercapacitor applications.

PubMed

Saravanakumar, Balasubramaniam; Jayaseelan, Santhana Sivabalan; Seo, Min-Kang; Kim, Hak-Yong; Kim, Byoung-Suhk

2017-12-07

Wire type supercapacitors with high energy and power densities have generated considerable interest in wearable applications. Herein, we report a novel NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire electrode for high performance supercapacitor application. In this work, a facile method is introduced to fabricate a 3D, porous Ni film deposited on a Ni wire as a flexible electrode, followed by decoration with NiCo 2 S 4 as an electroactive material. The fabricated NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire electrode displays a superior performance with an areal and volumetric capacitance of 1.228 F cm -2 and 199.74 F cm -3 , respectively, at a current density of 0.2 mA cm -1 with a maximum volumetric energy and power density (E V : 6.935 mW h cm -3 ; P V : 1.019 W cm -3 ). Finally, the solid state asymmetric wire type supercapacitor is fabricated using the fabricated NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire as a positive electrode and N-doped reduced graphene oxide (N-rGO) as a negative electrode and this exhibits good areal and volumetric capacitances of C A : 0.12 F cm -2 and C V : 19.57 F cm -2 with a higher rate capability (92%). This asymmetric wire type supercapacitor demonstrates a low leakage current and self-discharge with a maximum volumetric energy (E V : 5.33 mW h cm -3 ) and power (P V : 855.69 mW cm -3 ) density.

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.

High energy overcurrent protective device

DOEpatents

Praeg, Walter F.

1982-01-01

Electrical loads connected to capacitance elements in high voltage direct current systems are protected from damage by capacitance discharge overcurrents by connecting between the capacitance element and the load, a longitudinal inductor comprising a bifilar winding wound about a magnetic core, which forms an incomplete magnetic circuit. A diode is connected across a portion of the bifilar winding which conducts a unidirectional current only. Energy discharged from the capacitance element is stored in the inductor and then dissipated in an L-R circuit including the diode and the coil winding. Multiple high voltage circuits having capacitance elements may be connected to loads through bifilar windings all wound about the aforementioned magnetic core.

Leakage current-induced effects in the silicon microstrip and gas electron multiplier readout chain and their compensation method

NASA Astrophysics Data System (ADS)

Zubrzycka, W.; Kasinski, K.

2018-04-01

Leakage current flowing into the charge sensitive amplifier (CSA) is a common issue in many radiation detection systems as it can increase overall system noise, shift a DC baseline or even lead a recording channel to instability. The commonly known leakage current contributor is a detector, however other system components like wires or an input protection circuit may become a serious problem. Compensation of the leakage current resulting from the electrostatic discharge (ESD) protection circuit by properly sizing its components is possible only for a narrow temperature range. Moreover, the leakage current from external sources can be significantly larger. Many applications, especially High Energy Physics (HEP) experiments, require a fast baseline restoration for high input hit rates by applying either a low-value feedback resistor or a high feedback resistance combined with a pulsed reset circuit. Leakage current flowing in the feedback in conjunction with a large feedback resistance supplied with a pulsed reset results in a significant voltage offset between the CSA input and output which can cause problems (e.g. fake hits or instability). This paper shows an issue referred to the leakage current of the ESD protection circuit flowing into the input amplifier. The following analysis and proposed solution is a result of the time and energy readout ASIC project realization for the Compressed Baryonic Matter (CBM) experiment at FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. This chip is purposed to work with microstrip and gaseous detectors, with high average input pulses frequencies (250 kHit/s per channel) and the possibility to process input charge of both polarities. We present measurements of the test structure fabricated in UMC 180 nm technology and propose a solution addressing leakage current related issues. This work combines the leakage current compensation capabilities at the CSA level with high, controllable value of the amplifier feedback resistor independent of the leakage current level and polarity. The simulation results of the double, switchable, Krummenacher circuit-based feedback application in the CSA with a pulsed reset functionality are presented.

Atomic layer deposition TiO 2-Al 2O 3 stack: An improved gate dielectric on Ga-polar GaN metal oxide semiconductor capacitors

DOE PAGES

Wei, Daming; Edgar, James H.; Briggs, Dayrl P.; ...

2014-10-15

This research focuses on the benefits and properties of TiO 2-Al 2O 3 nano-stack thin films deposited on Ga 2O 3/GaN by plasma-assisted atomic layer deposition (PA-ALD) for gate dielectric development. This combination of materials achieved a high dielectric constant, a low leakage current, and a low interface trap density. Correlations were sought between the films’ structure, composition, and electrical properties. The gate dielectrics were approximately 15 nm thick and contained 5.1 nm TiO 2, 7.1 nm Al 2O 3 and 2 nm Ga 2O 3 as determined by spectroscopic ellipsometry. The interface carbon concentration, as measured by x-ray photoelectronmore » spectroscopy (XPS) depth profile, was negligible for GaN pretreated by thermal oxidation in O 2 for 30 minutes at 850°C. The RMS roughness slightly increased after thermal oxidation and remained the same after ALD of the nano-stack, as determined by atomic force microscopy. The dielectric constant of TiO 2-Al 2O 3 on Ga2O3/GaN was increased to 12.5 compared to that of pure Al 2O 3 (8~9) on GaN. In addition, the nano-stack's capacitance-voltage (C-V) hysteresis was small, with a total trap density of 8.74 × 10 11 cm -2. The gate leakage current density (J=2.81× 10 -8 A/cm 2) was low at +1 V gate bias. These results demonstrate the promising potential of plasma ALD deposited TiO 2/Al 2O 3 for serving as the gate oxide on Ga 2O 3/GaN based MOS devices.« less

Atomic layer deposition TiO 2-Al 2O 3 stack: An improved gate dielectric on Ga-polar GaN metal oxide semiconductor capacitors

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

Wei, Daming; Edgar, James H.; Briggs, Dayrl P.

This research focuses on the benefits and properties of TiO 2-Al 2O 3 nano-stack thin films deposited on Ga 2O 3/GaN by plasma-assisted atomic layer deposition (PA-ALD) for gate dielectric development. This combination of materials achieved a high dielectric constant, a low leakage current, and a low interface trap density. Correlations were sought between the films’ structure, composition, and electrical properties. The gate dielectrics were approximately 15 nm thick and contained 5.1 nm TiO 2, 7.1 nm Al 2O 3 and 2 nm Ga 2O 3 as determined by spectroscopic ellipsometry. The interface carbon concentration, as measured by x-ray photoelectronmore » spectroscopy (XPS) depth profile, was negligible for GaN pretreated by thermal oxidation in O 2 for 30 minutes at 850°C. The RMS roughness slightly increased after thermal oxidation and remained the same after ALD of the nano-stack, as determined by atomic force microscopy. The dielectric constant of TiO 2-Al 2O 3 on Ga2O3/GaN was increased to 12.5 compared to that of pure Al 2O 3 (8~9) on GaN. In addition, the nano-stack's capacitance-voltage (C-V) hysteresis was small, with a total trap density of 8.74 × 10 11 cm -2. The gate leakage current density (J=2.81× 10 -8 A/cm 2) was low at +1 V gate bias. These results demonstrate the promising potential of plasma ALD deposited TiO 2/Al 2O 3 for serving as the gate oxide on Ga 2O 3/GaN based MOS devices.« less

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.

Enhanced Capacitance of Hybrid Layered Graphene/Nickel Nanocomposite for Supercapacitors

NASA Astrophysics Data System (ADS)

Mohd Zaid, Norsaadatul Akmal; Idris, Nurul Hayati

2016-08-01

In this work, Ni nanoparticles were directly decorated on graphene (G) nanosheets via mechanical ball milling. Based on transmission electron microscopy observations, the Ni nanoparticles were well dispersed and attached to the G nanosheet without any agglomerations. Electrochemical results showed that the capacitance of a G/Ni nanocomposite was 275 F g-1 at a current density of 2 A g-1, which is higher than the capacitance of bare G (145 F g-1) and bare Ni (3 F g-1). The G/Ni electrode also showed superior performance at a high current density, exhibiting a capacitance of 190 F g-1 at a current density of 5 A g-1 and a capacitance of 144 F g-1 at a current density of 10 A g-1. The equivalent series resistance for G/Ni nanocomposites also decreased. The enhanced performance of this hybrid supercapacitor is best described by the synergistic effect, i.e. dual charge-storage mechanism, which is demonstrated by electrical double layer and pseudocapacitance materials. Moreover, a high specific surface area and electrical conductivity of the materials enhanced the capacitance. These results indicate that the G/Ni nanocomposite is a potential supercapacitor.

Enhanced Capacitance of Hybrid Layered Graphene/Nickel Nanocomposite for Supercapacitors.

PubMed

Mohd Zaid, Norsaadatul Akmal; Idris, Nurul Hayati

2016-08-24

In this work, Ni nanoparticles were directly decorated on graphene (G) nanosheets via mechanical ball milling. Based on transmission electron microscopy observations, the Ni nanoparticles were well dispersed and attached to the G nanosheet without any agglomerations. Electrochemical results showed that the capacitance of a G/Ni nanocomposite was 275 F g(-1) at a current density of 2 A g(-1), which is higher than the capacitance of bare G (145 F g(-1)) and bare Ni (3 F g(-1)). The G/Ni electrode also showed superior performance at a high current density, exhibiting a capacitance of 190 F g(-1) at a current density of 5 A g(-1) and a capacitance of 144 F g(-1) at a current density of 10 A g(-1). The equivalent series resistance for G/Ni nanocomposites also decreased. The enhanced performance of this hybrid supercapacitor is best described by the synergistic effect, i.e. dual charge-storage mechanism, which is demonstrated by electrical double layer and pseudocapacitance materials. Moreover, a high specific surface area and electrical conductivity of the materials enhanced the capacitance. These results indicate that the G/Ni nanocomposite is a potential supercapacitor.

Transparent and Flexible Capacitors with an Ultrathin Structure by Using Graphene as Bottom Electrodes.

PubMed

Guo, Tao; Zhang, Guozhen; Su, Xi; Zhang, Heng; Wan, Jiaxian; Chen, Xue; Wu, Hao; Liu, Chang

2017-11-28

Ultrathin, transparent and flexible capacitors using graphene as the bottom electrodes were directly fabricated on polyethylene naphthalate (PEN) substrates. ZrO₂ dielectric films were deposited on the treated surface of graphene by atomic layer deposition (ALD). The deposition process did not introduce any detectible defects in the graphene, as indicated by Raman measurements, guaranteeing the electrical performances of the graphene electrodes. The Aluminum-doped zinc oxide (AZO) films were prepared as the top electrodes using the ALD technique. The capacitors presented a high capacitance density (10.3 fF/μm² at 10 kHz) and a relatively low leakage current (5.3 × 10 -6 A/cm² at 1 V). Bending tests revealed that the capacitors were able to work normally at an outward bending radius of 10 mm without any deterioration of electrical properties. The capacitors exhibited an average optical transmittance of close to 70% at visible wavelengths. Thus, it opens the door to practical applications in transparent integrated circuits.

Transparent and Flexible Capacitors with an Ultrathin Structure by Using Graphene as Bottom Electrodes

PubMed Central

Guo, Tao; Zhang, Guozhen; Su, Xi; Zhang, Heng; Wan, Jiaxian; Chen, Xue; Wu, Hao; Liu, Chang

2017-01-01

Ultrathin, transparent and flexible capacitors using graphene as the bottom electrodes were directly fabricated on polyethylene naphthalate (PEN) substrates. ZrO2 dielectric films were deposited on the treated surface of graphene by atomic layer deposition (ALD). The deposition process did not introduce any detectible defects in the graphene, as indicated by Raman measurements, guaranteeing the electrical performances of the graphene electrodes. The Aluminum-doped zinc oxide (AZO) films were prepared as the top electrodes using the ALD technique. The capacitors presented a high capacitance density (10.3 fF/μm2 at 10 kHz) and a relatively low leakage current (5.3 × 10−6 A/cm2 at 1 V). Bending tests revealed that the capacitors were able to work normally at an outward bending radius of 10 mm without any deterioration of electrical properties. The capacitors exhibited an average optical transmittance of close to 70% at visible wavelengths. Thus, it opens the door to practical applications in transparent integrated circuits. PMID:29182551

Study of monolithic integrated solar blind GaN-based photodetectors

NASA Astrophysics Data System (ADS)

Wang, Ling; Zhang, Yan; Li, Xiaojuan; Xie, Jing; Wang, Jiqiang; Li, Xiangyang

2018-02-01

Monolithic integrated solar blind devices on the GaN-based epilayer, which can directly readout voltage signal, were fabricated and studied. Unlike conventional GaN-based photodiodes, the integrated devices can finish those steps: generation, accumulation of carriers and conversion of carriers to voltage. In the test process, the resetting voltage was square wave with the frequency of 15 and 110 Hz, its maximal voltage of ˜2.5 V. Under LEDs illumination, the maximum of voltage swing is about 2.5 V, and the rise time of voltage swing from 0 to 2.5 V is only about 1.6 ms. However, in dark condition, the node voltage between detector and capacitance nearly decline to zero with time when the resetting voltage was equal to zero. It is found that the leakage current in the circuit gives rise to discharge of the integrated charge. Storage mode operation can offer gain, which is advantage to detection of weak photo signal.

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.

Effect of annealing temperature on microstructural evolution and electrical properties of sol-gel processed ZrO2/Si films

NASA Astrophysics Data System (ADS)

Hwang, Soo Min; Lee, Seung Muk; Park, Kyung; Lee, Myung Soo; Joo, Jinho; Lim, Jun Hyung; Kim, Hyoungsub; Yoon, Jae Jin; Kim, Young Dong

2011-01-01

High-permittivity (k) ZrO2/Si(100) films were fabricated by a sol-gel technique and the microstructural evolution with the annealing temperature (Ta) was correlated with the variation of their electrical performance. With increasing Ta, the ZrO2 films crystallized into a tetragonal (t) phase which was maintained until 700 °C at nanoscale thicknesses. Although the formation of the t-ZrO2 phase obviously enhanced the k value of the ZrO2 dielectric layer, the maximum capacitance in accumulation was decreased by the growth of a low-k interfacial layer (IL) between ZrO2 and Si with increasing Ta. On the other hand, the gate leakage current was remarkably depressed with increasing Ta probably due to the combined effects of the increased IL thickness, optical band gap of ZrO2, and density of ZrO2 and decreased remnant organic components.

Improved interfacial and electrical properties of GaAs metal-oxide-semiconductor capacitors with HfTiON as gate dielectric and TaON as passivation interlayer

NASA Astrophysics Data System (ADS)

Wang, L. S.; Xu, J. P.; Zhu, S. Y.; Huang, Y.; Lai, P. T.

2013-08-01

The interfacial and electrical properties of sputtered HfTiON on sulfur-passivated GaAs with or without TaON as interfacial passivation layer (IPL) are investigated. Experimental results show that the GaAs metal-oxide-semiconductor capacitor with HfTiON/TaON stacked gate dielectric annealed at 600 °C exhibits low interface-state density (1.0 × 1012 cm-2 eV-1), small gate leakage current (7.3 × 10-5 A cm-2 at Vg = Vfb + 1 V), small capacitance equivalent thickness (1.65 nm), and large equivalent dielectric constant (26.2). The involved mechanisms lie in the fact that the TaON IPL can effectively block the diffusions of Hf, Ti, and O towards GaAs surface and suppress the formation of interfacial As-As bonds, Ga-/As-oxides, thus unpinning the Femi level at the TaON/GaAs interface and improving the interface quality and electrical properties of the device.

Ultraflexible and tailorable all-solid-state supercapacitors using polyacrylamide-based hydrogel electrolyte with high ionic conductivity.

PubMed

Li, Huili; Lv, Tian; Li, Ning; Yao, Yao; Liu, Kai; Chen, Tao

2017-11-30

Hydrogels with high ionic conductivity consisting of a cross-linked polymer network swollen in water are very promising to be used as an electrolyte for all-solid-state supercapacitors. However, there are rather few flexible supercapacitors using ionic conducting hydrogel electrolytes reported to date. In this work, highly flexible and ionic conducting polyacrylamide hydrogels were synthesized through a simple approach. On using the ionic hydrogels as the electrolyte, the resulting supercapacitors not only exhibited a high specific capacitance but also showed a long self-discharge time (over 10 hours to the half of original open-circuit voltage) and a low leakage current. These newly-developed all-solid-state supercapacitors can be bent, knot, and kneaded for 5000 cycles without performance decay, suggesting excellent flexibility and mechanical stability. These all-solid-state supercapacitors can also be easily tailored into strip-like supercapacitors without a short circuit, which provides an efficient approach to fabricate wearable energy storage devices.

Passivation of oxide traps and interface states in GaAs metal-oxide-semiconductor capacitor by LaTaON passivation layer and fluorine incorporation

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

Liu, L. N.; Choi, H. W.; Lai, P. T., E-mail: laip@eee.hku.hk

2015-11-23

GaAs metal-oxide-semiconductor capacitor with TaYON/LaTaON gate-oxide stack and fluorine-plasma treatment is fabricated and compared with its counterparts without the LaTaON passivation interlayer or the fluorine treatment. Experimental results show that the sample exhibits better characteristics: low interface-state density (8 × 10{sup 11 }cm{sup −2}/eV), small flatband voltage (0.69 V), good capacitance-voltage behavior, small frequency dispersion, and small gate leakage current (6.35 × 10{sup −6} A/cm{sup 2} at V{sub fb} + 1 V). These should be attributed to the suppressed growth of unstable Ga and As oxides on the GaAs surface during gate-oxide annealing by the LaTaON interlayer and fluorine incorporation, and the passivating effects of fluorine atoms on the acceptor-likemore » interface and near-interface traps.« less

Inkjet printing of metal-oxide-based transparent thin-film capacitors

NASA Astrophysics Data System (ADS)

Matavž, A.; Malič, B.; Bobnar, V.

2017-12-01

We report on the inkjet printing of transparent, thin-film capacitors (TTFCs) composed of indium-zinc-oxide electrodes and a tantalum-oxide-based dielectric on glass substrates. The printing parameters were adapted for the sequential deposition of functional layers, resulting in approximately 100-nm-thick transparent capacitors with a uniform thickness. The relatively high electrical resistivity of the electrodes is reflected in the frequency dispersive dielectric behaviour, which is explained in terms of an equivalent circuit. The resistivity of the electrode strongly decreases with the number of printing passes; consequently, any misalignment of the printed layers is detected in the measured response. At low frequency, the TTFCs show a stable intrinsic dielectric response and a high capacitance density of ˜280 nF/cm2. The good dielectric performance as well as the low leakage-current density (8 × 10-7 A/cm2 at 1 MV cm-1) of our capacitors indicates that inkjet printing can be used to produce all-printed, high-quality electrical devices.

Improving the electrical properties of lanthanum silicate films on ge metal oxide semiconductor capacitors by adopting interfacial barrier and capping layers.

PubMed

Choi, Yu Jin; Lim, Hajin; Lee, Suhyeong; Suh, Sungin; Kim, Joon Rae; Jung, Hyung-Suk; Park, Sanghyun; Lee, Jong Ho; Kim, Seong Gyeong; Hwang, Cheol Seong; Kim, HyeongJoon

2014-05-28

The electrical properties of La-silicate films grown by atomic layer deposition (ALD) on Ge substrates with different film configurations, such as various Si concentrations, Al2O3 interfacial passivation layers, and SiO2 capping layers, were examined. La-silicate thin films were deposited using alternating injections of the La[N{Si(CH3)3}2]3 precursor with O3 as the La and O precursors, respectively, at a substrate temperature of 310 °C. The Si concentration in the La-silicate films was further controlled by adding ALD cycles of SiO2. For comparison, La2O3 films were also grown using [La((i)PrCp)3] and O3 as the La precursor and oxygen source, respectively, at the identical substrate temperature. The capacitance-voltage (C-V) hysteresis decreased with an increasing Si concentration in the La-silicate films, although the films showed a slight increase in the capacitance equivalent oxide thickness. The adoption of Al2O3 at the interface as a passivation layer resulted in lower C-V hysteresis and a low leakage current density. The C-V hysteresis voltages of the La-silicate films with Al2O3 passivation and SiO2 capping layers was significantly decreased to ∼0.1 V, whereas the single layer La-silicate film showed a hysteresis voltage as large as ∼1.0 V.

Modeling and analysis of sub-surface leakage current in nano-MOSFET under cutoff regime

NASA Astrophysics Data System (ADS)

Swami, Yashu; Rai, Sanjeev

2017-02-01

The high leakage current in nano-meter regimes is becoming a significant portion of power dissipation in nano-MOSFET circuits as threshold voltage, channel length, and gate oxide thickness are scaled down to nano-meter range. Precise leakage current valuation and meticulous modeling of the same at nano-meter technology scale is an increasingly a critical work in designing the low power nano-MOSFET circuits. We present a specific compact model for sub-threshold regime leakage current in bulk driven nano-MOSFETs. The proposed logical model is instigated and executed into the latest updated PTM bulk nano-MOSFET model and is found to be in decent accord with technology-CAD simulation data. This paper also reviews various transistor intrinsic leakage mechanisms for nano-MOSFET exclusively in weak inversion, like drain-induced barricade lowering (DIBL), gate-induced drain leakage (GIDL), gate oxide tunneling (GOT) leakage etc. The root cause of the sub-surface leakage current is mainly due to the nano-scale short channel length causing source-drain coupling even in sub-threshold domain. Consequences leading to carriers triumphing the barricade between the source and drain. The enhanced model effectively considers the following parameter dependence in the account for better-quality value-added results like drain-to-source bias (VDS), gate-to-source bias (VGS), channel length (LG), source/drain junction depth (Xj), bulk doping concentration (NBULK), and operating temperature (Top).

Simulation of leakage current measurement on medical devices using helmholtz coil configuration with different current flow

NASA Astrophysics Data System (ADS)

Sutanto, E.; Chandra, F.; Dinata, R.

2017-05-01

Leakage current measurement which can follow IEC standard for medical device is one of many challenges to be answered. The IEC 60601-1 has defined that the limit for a leakage current for Medical Device can be as low as 10 µA and as high as 500 µA, depending on which type of contact (applied part) connected to the patient. Most people are using ELCB (Earth-leakage circuit breaker) for safety purpose as this is the most common and available safety device in market. One type of ELCB devices is RCD (Residual Current Device) and this RCD type can measure the leakage current directly. This work will show the possibility on how Helmholtz Coil Configuration can be made to be like the RCD. The possibility is explored by comparing the magnetic field formula from each device, then it proceeds with a simulation using software EJS (Easy Java Simulation). The simulation will make sure the concept of magnetic field current cancellation follows the RCD concept. Finally, the possibility of increasing the measurement’s sensitivity is also analyzed. The sensitivity is needed to see the possibility on reaching the minimum leakage current limit defined by IEC, 0.01mA.

Low leakage current gate dielectrics prepared by ion beam assisted deposition for organic thin film transistors

NASA Astrophysics Data System (ADS)

Kim, Chang Su; Jo, Sung Jin; Kim, Jong Bok; Ryu, Seung Yoon; Noh, Joo Hyon; Baik, Hong Koo; Lee, Se Jong; Kim, Youn Sang

2007-12-01

This communication reports on the fabrication of low operating voltage pentacene thin-film transistors with high-k gate dielectrics by ion beam assisted deposition (IBAD). These densely packed dielectric layers by IBAD show a much lower level of leakage current than those created by e-beam evaporation. These results, from the fact that those thin films deposited with low adatom mobility, have an open structure, consisting of spherical grains with pores in between, that acts as a significant path for leakage current. By contrast, our results demonstrate the potential to limit this leakage. The field effect mobility, on/off current ratio, and subthreshold slope obtained from pentacene thin-film transistors (TFTs) were 1.14 cm2/V s, 105, and 0.41 V/dec, respectively. Thus, the high-k gate dielectrics obtained by IBAD show promise in realizing low leakage current, low voltage, and high mobility pentacene TFTs.

Finite Element Analysis of Film Stack Architecture for Complementary Metal-Oxide-Semiconductor Image Sensors.

PubMed

Wu, Kuo-Tsai; Hwang, Sheng-Jye; Lee, Huei-Huang

2017-05-02

Image sensors are the core components of computer, communication, and consumer electronic products. Complementary metal oxide semiconductor (CMOS) image sensors have become the mainstay of image-sensing developments, but are prone to leakage current. In this study, we simulate the CMOS image sensor (CIS) film stacking process by finite element analysis. To elucidate the relationship between the leakage current and stack architecture, we compare the simulated and measured leakage currents in the elements. Based on the analysis results, we further improve the performance by optimizing the architecture of the film stacks or changing the thin-film material. The material parameters are then corrected to improve the accuracy of the simulation results. The simulated and experimental results confirm a positive correlation between measured leakage current and stress. This trend is attributed to the structural defects induced by high stress, which generate leakage. Using this relationship, we can change the structure of the thin-film stack to reduce the leakage current and thereby improve the component life and reliability of the CIS components.

Finite Element Analysis of Film Stack Architecture for Complementary Metal-Oxide–Semiconductor Image Sensors

PubMed Central

Wu, Kuo-Tsai; Hwang, Sheng-Jye; Lee, Huei-Huang

2017-01-01

Image sensors are the core components of computer, communication, and consumer electronic products. Complementary metal oxide semiconductor (CMOS) image sensors have become the mainstay of image-sensing developments, but are prone to leakage current. In this study, we simulate the CMOS image sensor (CIS) film stacking process by finite element analysis. To elucidate the relationship between the leakage current and stack architecture, we compare the simulated and measured leakage currents in the elements. Based on the analysis results, we further improve the performance by optimizing the architecture of the film stacks or changing the thin-film material. The material parameters are then corrected to improve the accuracy of the simulation results. The simulated and experimental results confirm a positive correlation between measured leakage current and stress. This trend is attributed to the structural defects induced by high stress, which generate leakage. Using this relationship, we can change the structure of the thin-film stack to reduce the leakage current and thereby improve the component life and reliability of the CIS components. PMID:28468324

A Passive EMI Filter with Access to the Ungrounded Motor Neutral Line-Its Effect on Eliminating Leakage Current from the Inverter Heat Sink-

NASA Astrophysics Data System (ADS)

Doumoto, Takafumi; Akagi, Hirofumi

This paper deals with a leakage current flowing out of the heat sink of a voltage-source PWM inverter. The heat-sink leakage current is caused by a steep change in the common-mode voltage produced by the inverter. It flows through parasitic capacitors between the heat sink and power semiconductor devices when no EMI filter is connected. Experimental results reveal that the heat-sink leakage current flows not into the supply side, but into the motor side. These understandings succeed in describing an equivalent common-mode circuit taking the parasitic capacitors into account. The authors have proposed a passive EMI filter that is unique in access to the ungrounded motor neutral line. It is discussed from this equivalent circuit that the passive EMI filter is effective in preventing the leakage current from flowing. Moreover, installation of another small-sized common-mode inductor at the ac side of the diode rectifier prevents the leakage current from flowing into the supply side. Experimental results obtained from a 200-V, 3.7-kW laboratory system confirm the effectiveness and viability of the EMI filter.

Modification of electrical properties of Au/n-type InP Schottky diode with a high-k Ba0.6Sr0.4TiO3 interlayer

NASA Astrophysics Data System (ADS)

Thapaswini, P. Prabhu; Padma, R.; Balaram, N.; Bindu, B.; Rajagopal Reddy, V.

2016-05-01

Au/Ba0.6Sr0.4TiO3 (BST)/n-InP metal/insulator/semiconductor (MIS) Schottky diodes have been analyzed by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The surface morphology of the BST films on InP is fairly smooth. The Au/BST/n-InP MIS Schottky diode shows better rectification ratio and low leakage current compared to the conventional Au/n-InP metal-semiconductor (MS) Schottky diode. Higher barrier height is achieved for the MIS Schottky diode compared to the MS Schottky diode. The Norde and Cheung's methods are employed to determine the barrier height, ideality factor and series resistance. The interface state density (NSS) is determined from the forward bias I-V data for both the MS and MIS Schottky diodes. Results reveal that the NSS of the MIS Schottky diode is lower than that of the MS Schottky diode. The Poole-Frenkel emission is found dominating the reverse current in both Au/n-InP MS and Au/BST/n-InP MIS Schottky diodes, indicating the presence of structural defects and trap levels in the dielectric film.

Characterization of the GaN-MgO Transistor Interface: More Power and Efficiency

NASA Astrophysics Data System (ADS)

Sanchez, Jose; Kumah, Divine; Walker, Fred

2012-02-01

In this age of high-energy consumption, the development of more efficient and more reliable devices is indispensable. Gallium nitride (GaN)-based devices are an option in achieving this goal. GaN's wide bandgap of 3.4 eV allows the device to handle large amount of current before leakage makes its energy consumption inefficient. The characteristics of GaN, in conjunction with those of Magnesium oxide (MgO), would allow for improvement of different electronic applications such as mobile phone communication technology. In this work, the fabrication of the GaN/MgO device was done by Molecular Beam Epitaxy. This device was grown under a variety of parameters where the growth temperature, growth chamber pressure, and the rate of material deposition were changed. To determine the optimal growth parameters, current-voltage and capacitance-voltage measurements were conducted on to evaluate the effects of these growth conditions. Atomic Force Microscopy was also used in characterizing the crystallinity and morphology of the samples. A conclusion of the research is that by improving the roughness of the substrate, the breakdown voltage of the MgO layer and the overall performance of the device can be improve, yielding a device with very low energy loss in the current transmission process.

Correlation between dislocations and leakage current of p-n diodes on a free-standing GaN substrate

NASA Astrophysics Data System (ADS)

Usami, Shigeyoshi; Ando, Yuto; Tanaka, Atsushi; Nagamatsu, Kentaro; Deki, Manato; Kushimoto, Maki; Nitta, Shugo; Honda, Yoshio; Amano, Hiroshi; Sugawara, Yoshihiro; Yao, Yong-Zhao; Ishikawa, Yukari

2018-04-01

Dislocations that cause a reverse leakage current in vertical p-n diodes on a GaN free-standing substrate were investigated. Under a high reverse bias, dot-like leakage spots were observed using an emission microscope. Subsequent cathodoluminescence (CL) observations revealed that the leakage spots coincided with part of the CL dark spots, indicating that some types of dislocation cause reverse leakage. When etch pits were formed on the dislocations by KOH etching, three sizes of etch pits were obtained (large, medium, and small). Among these etch pits, only the medium pits coincided with leakage spots. Additionally, transmission electron microscopy observations revealed that pure screw dislocations are present under the leakage spots. The results revealed that 1c pure screw dislocations are related to the reverse leakage in vertical p-n diodes.

Initial leakage current paths in the vertical-type GaN-on-GaN Schottky barrier diodes

NASA Astrophysics Data System (ADS)

Sang, Liwen; Ren, Bing; Sumiya, Masatomo; Liao, Meiyong; Koide, Yasuo; Tanaka, Atsushi; Cho, Yujin; Harada, Yoshitomo; Nabatame, Toshihide; Sekiguchi, Takashi; Usami, Shigeyoshi; Honda, Yoshio; Amano, Hiroshi

2017-09-01

Electrical characteristics of leakage current paths in vertical-type n-GaN Schottky barrier diodes (SBDs) on free-standing GaN substrates are investigated by using photon emission microscopy (PEM). The PEM mapping shows that the initial failure of the SBD devices at low voltages is due to the leakage current paths from polygonal pits in the GaN epilayers. It is observed that these polygonal pits originate from carbon impurity accumulation to the dislocations with a screw-type component by microstructure analysis. For the SBD without polygonal pits, no initial failure is observed and the first leakage appeals at the edge of electrodes as a result of electric field concentration. The mechanism of leakage at pits is explained in terms of trap assisted tunneling through fitting current-voltage characteristics.

Integration of lead-free ferroelectric on HfO2/Si (100) for high performance non-volatile memory applications

PubMed Central

Kundu, Souvik; Maurya, Deepam; Clavel, Michael; Zhou, Yuan; Halder, Nripendra N.; Hudait, Mantu K.; Banerji, Pallab; Priya, Shashank

2015-01-01

We introduce a novel lead-free ferroelectric thin film (1-x)BaTiO3-xBa(Cu1/3Nb2/3)O3 (x = 0.025) (BT-BCN) integrated on to HfO2 buffered Si for non-volatile memory (NVM) applications. Piezoelectric force microscopy (PFM), x-ray diffraction, and high resolution transmission electron microscopy were employed to establish the ferroelectricity in BT-BCN thin films. PFM study reveals that the domains reversal occurs with 180° phase change by applying external voltage, demonstrating its effectiveness for NVM device applications. X-ray photoelectron microscopy was used to investigate the band alignments between atomic layer deposited HfO2 and pulsed laser deposited BT-BCN films. Programming and erasing operations were explained on the basis of band-alignments. The structure offers large memory window, low leakage current, and high and low capacitance values that were easily distinguishable even after ~106 s, indicating strong charge storage potential. This study explains a new approach towards the realization of ferroelectric based memory devices integrated on Si platform and also opens up a new possibility to embed the system within current complementary metal-oxide-semiconductor processing technology. PMID:25683062

Relationship between plasma parameters and film microstructure in radio frequency magnetron sputter deposition of barium strontium titanate

NASA Astrophysics Data System (ADS)

Panda, B.; Dhar, A.; Nigam, G. D.; Bhattacharya, D.; Ray, S. K.

1998-01-01

Radio frequency magnetron sputtered Ba0.8Sr0.2TiO3 thin films have been deposited on silicon and Si/SiO2/SiN/Pt substrates. The analysis of plasma discharge has been carried out using the Langmuir probe technique. Both the pressure and power have been found to influence the ion density and self-bias of the target. Introduction of oxygen into the discharge effectively decreases the ion density. The structural and electrical properties have been investigated using x-ray diffraction, atomic force microscopy of deposited films and capacitance-voltage, conductance-voltage, and current density-electric field characteristics of fabricated capacitors. The growth and orientation of the films have been found to depend upon the type of substrates and deposition temperatures. The <100> texture in the film is promoted at a pressure 0.25 Torr with a moderately high value of ion density and low ion bombardment energy. Films deposited on Si/SiO2/SiN/Pt substrate have shown higher dielectric constant (191) and lower leakage current density (2.8×10-6 A/cm2 at 100 kV/cm) compared to that on silicon.

Interfacial characteristics and leakage current transfer mechanisms in organometal trihalide perovskite gate-controlled devices via doping of PCBM

NASA Astrophysics Data System (ADS)

Wang, Yucheng; Zhang, Yuming; Liu, Yintao; Pang, Tiqiang; Hu, Ziyang; Zhu, Yuejin; Luan, Suzhen; Jia, Renxu

2017-11-01

Two types of perovskite (with and without doping of PCBM) based metal-oxide-semiconductor (MOS) gate-controlled devices were fabricated and characterized. The study of the interfacial characteristics and charge transfer mechanisms by doping of PCBM were analyzed by material and electrical measurements. Doping of PCBM does not affect the size and crystallinity of perovskite films, but has an impact on carrier extraction in perovskite MOS devices. The electrical hysteresis observed in capacitance-voltage and current-voltage measurements can be alleviated by doping of PCBM. Experimental results demonstrate that extremely low trap densities are found for the perovskite device without doping, while the doped sample leads to higher density of interface state. Three mechanisms including Ohm’s law, trap-filled-limit (TFL) emission, and child’s law were used to analyze possible charge transfer mechanisms. Ohm’s law mechanism is well suitable for charge transfer of both the perovskite MOS devices under light condition at large voltage, while TFL emission well addresses the behavior of charge transfer under dark at small voltage. This change of charge transfer mechanism is attributed to the impact of the ion drift within perovskites.

Silicon on ferroelectic insulator field effect transistor (SOF-FET) a new device for the next generation ultra low power circuits

NASA Astrophysics Data System (ADS)

Es-Sakhi, Azzedin D.

Field effect transistors (FETs) are the foundation for all electronic circuits and processors. These devices have progressed massively to touch its final steps in sub-nanometer level. Left and right proposals are coming to rescue this progress. Emerging nano-electronic devices (resonant tunneling devices, single-atom transistors, spin devices, Heterojunction Transistors rapid flux quantum devices, carbon nanotubes, and nanowire devices) took a vast share of current scientific research. Non-Si electronic materials like III-V heterostructure, ferroelectric, carbon nanotubes (CNTs), and other nanowire based designs are in developing stage to become the core technology of non-classical CMOS structures. FinFET present the current feasible commercial nanotechnology. The scalability and low power dissipation of this device allowed for an extension of silicon based devices. High short channel effect (SCE) immunity presents its major advantage. Multi-gate structure comes to light to improve the gate electrostatic over the channel. The new structure shows a higher performance that made it the first candidate to substitute the conventional MOSFET. The device also shows a future scalability to continue Moor's Law. Furthermore, the device is compatible with silicon fabrication process. Moreover, the ultra-low-power (ULP) design required a subthreshold slope lower than the thermionic-emission limit of 60mV/ decade (KT/q). This value was unbreakable by the new structure (SOI-FinFET). On the other hand most of the previews proposals show the ability to go beyond this limit. However, those pre-mentioned schemes have publicized a very complicated physics, design difficulties, and process non-compatibility. The objective of this research is to discuss various emerging nano-devices proposed for ultra-low-power designs and their possibilities to replace the silicon devices as the core technology in the future integrated circuit. This thesis proposes a novel design that exploits the concept of negative capacitance. The new field effect transistor (FET) based on ferroelectric insulator named Silicon-On-Ferroelectric Insulator Field Effect Transistor (SOF-FET). This proposal is a promising methodology for future ultra-low-power applications, because it demonstrates the ability to replace the silicon-bulk based MOSFET, and offers subthreshold swing significantly lower than 60mV/decade and reduced threshold voltage to form a conducting channel. The SOF-FET can also solve the issue of junction leakage (due to the presence of unipolar junction between the top plate of the negative capacitance and the diffused areas that form the transistor source and drain). In this device the charge hungry ferroelectric film already limits the leakage.

Performance Comparison of Finemet and Metglas Tape Cores Under Non-Sinusoidal Waveforms with DC Bias (POSTPRINT)

DTIC Science & Technology

2017-06-01

dc converter-based test system was built to intentionally introduce inductor current harmonics by varying the filter capacitance and parasitic...the inclusion of distorted waveforms obtained by varying filter capacitance. At higher frequencies, the Metglas cores were found to exhibit greater...was built to intentionally introduce inductor current harmonics by varying the filter capacitance and parasitic inductance of the test system. Both

Current Progress of Capacitive Deionization for Removal of Pollutant Ions

NASA Astrophysics Data System (ADS)

Gaikwad, Mahendra S.; Balomajumder, Chandrajit

2016-08-01

A mini review of a recently developing water purification technology capacitive deionization (CDI) applied for removal of pollutant ions is provided. The current progress of CDI for removal of different pollutant ions such as arsenic, fluoride, boron, phosphate, lithium, copper, cadmium, ferric, and nitrate ions is presented. This paper aims at motivating new research opportunities in capacitive deionization technology for removal of pollutant ions from polluted water.

Enhanced Capacitance of Hybrid Layered Graphene/Nickel Nanocomposite for Supercapacitors

PubMed Central

Mohd Zaid, Norsaadatul Akmal; Idris, Nurul Hayati

2016-01-01

In this work, Ni nanoparticles were directly decorated on graphene (G) nanosheets via mechanical ball milling. Based on transmission electron microscopy observations, the Ni nanoparticles were well dispersed and attached to the G nanosheet without any agglomerations. Electrochemical results showed that the capacitance of a G/Ni nanocomposite was 275 F g−1 at a current density of 2 A g−1, which is higher than the capacitance of bare G (145 F g−1) and bare Ni (3 F g−1). The G/Ni electrode also showed superior performance at a high current density, exhibiting a capacitance of 190 F g−1 at a current density of 5 A g−1 and a capacitance of 144 F g−1 at a current density of 10 A g−1. The equivalent series resistance for G/Ni nanocomposites also decreased. The enhanced performance of this hybrid supercapacitor is best described by the synergistic effect, i.e. dual charge-storage mechanism, which is demonstrated by electrical double layer and pseudocapacitance materials. Moreover, a high specific surface area and electrical conductivity of the materials enhanced the capacitance. These results indicate that the G/Ni nanocomposite is a potential supercapacitor. PMID:27553290

Transport mechanism of reverse surface leakage current in AlGaN/GaN high-electron mobility transistor with SiN passivation

NASA Astrophysics Data System (ADS)

Zheng, Xue-Feng; Fan, Shuang; Chen, Yong-He; Kang, Di; Zhang, Jian-Kun; Wang, Chong; Mo, Jiang-Hui; Li, Liang; Ma, Xiao-Hua; Zhang, Jin-Cheng; Hao, Yue

2015-02-01

The transport mechanism of reverse surface leakage current in the AlGaN/GaN high-electron mobility transistor (HEMT) becomes one of the most important reliability issues with the downscaling of feature size. In this paper, the research results show that the reverse surface leakage current in AlGaN/GaN HEMT with SiN passivation increases with the enhancement of temperature in the range from 298 K to 423 K. Three possible transport mechanisms are proposed and examined to explain the generation of reverse surface leakage current. By comparing the experimental data with the numerical transport models, it is found that neither Fowler-Nordheim tunneling nor Frenkel-Poole emission can describe the transport of reverse surface leakage current. However, good agreement is found between the experimental data and the two-dimensional variable range hopping (2D-VRH) model. Therefore, it is concluded that the reverse surface leakage current is dominated by the electron hopping through the surface states at the barrier layer. Moreover, the activation energy of surface leakage current is extracted, which is around 0.083 eV. Finally, the SiN passivated HEMT with a high Al composition and a thin AlGaN barrier layer is also studied. It is observed that 2D-VRH still dominates the reverse surface leakage current and the activation energy is around 0.10 eV, which demonstrates that the alteration of the AlGaN barrier layer does not affect the transport mechanism of reverse surface leakage current in this paper. Project supported by the National Natural Science Foundation of China (Grant Nos. 61334002, 61106106, and 61474091), the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory, China (Grant No. ZHD201206), the New Experiment Development Funds for Xidian University, China (Grant No. SY1213), the 111 Project, China (Grant No. B12026), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, China, and the Fundamental Research Funds for the Central Universities, China (Grant No. K5051325002).

Fabrication and Benchmarking of a Stratix V FPGA with Monolithic Integrated Microfluidic Cooling

DTIC Science & Technology

2017-03-01

run. The output from all cores were monitored through the Altera Signaltap tool in order to detect glitches which occurred in the output...dependence on temperature, and static/ leakage power, which comes from several components, such as subthreshold leakage , gate leakage , and reverse bias 220...junction current. Subthreshold leakage current tends to be the most significant temperature dependent component of the power [6,7] and is given by

Conversion efficiency of an energy harvester based on resonant tunneling through quantum dots with heat leakage.

PubMed

Kano, Shinya; Fujii, Minoru

2017-03-03

We study the conversion efficiency of an energy harvester based on resonant tunneling through quantum dots with heat leakage. Heat leakage current from a hot electrode to a cold electrode is taken into account in the analysis of the harvester operation. Modeling of electrical output indicates that a maximum heat leakage current is not negligible because it is larger than that of the heat current harvested into electrical power. A reduction of heat leakage is required in this energy harvester in order to obtain efficient heat-to-electrical conversion. Multiple energy levels of a quantum dot can increase the output power of the harvester. Heavily doped colloidal semiconductor quantum dots are a possible candidate for a quantum-dot monolayer in the energy harvester to reduce heat leakage, scaling down device size, and increasing electrical output via multiple discrete energy levels.

Electrical and dielectric properties of (barium, strontium) titanium trioxide thin film capacitors for ultra-high density dynamic random access memories

NASA Astrophysics Data System (ADS)

Basceri, Cem

The electrical and dielectric properties of fiber-textured, MOCVD (Basb{0.7}Srsb{0.3})TiOsb3 (BST) thin film capacitors appropriate for ultra-large scale integration (ULSI) dynamic random access memory (DRAM) applications have been analyzed. Dielectric relaxation, leakage, resistance degradation, and dielectric response phenomena, within a comprehensive matrix of external and material parameters, have been investigated. The phenomenology of the dielectric response of our BST films has been shown to be well-described by Curie-von Schweidler behavior, although the microscopic origin of this behavior has not been presently agreed upon. The time-dependent polarization behavior has been linked to the dispersion in permittivity with respect to frequency. The leakage current through our BST films has been found to be primarily limited by interfacial Schottky barriers whose properties depend on the electrode material, interface microstructure, and deposition conditions. Its temperature and voltage dependence have been interpreted via a thermionic emission model. Analysis in terms of Schottky-barrier limited current flow gave acceptable values for the cathode barrier height. The results have indicated that our BST films, appropriate for DRAM applications, do not possess depletion layers at the film-electrode interfaces. Instead, they must be considered as depleted of charge carriers across their entire thickness. Resistance degradation has been found to be thermally activated and voltage/field dependent. The results have indicated that there is a film thickness effect, which manifests itself as a decrease in the activation energy with respect to temperature for thicker films. A significant stoichiometry effect on the measured resistance degradation lifetimes has been observed. The analyses of the leakage and capacitance-voltage behaviors for the degraded samples have indicated that a demixing of oxygen vacancies occurs during resistance degradation, which causes the Schottky barrier height to decrease, in agreement with the observed relative shift of the peak capacitance as a function of voltage. For all the film thicknesses and compositions studied, extrapolated resistance degradation lifetimes of our BST films, which were obtained by using an appropriate form, are well above the current benchmark of 10 years at the DRAM operating conditions of 1.6 V and 85sp°C. Above the bulk Curie point (˜300 K), the phenomenological approach, i.e., Landau-Ginzburg-Devonshire (LGD) theory, has been demonstrated to account very well for the observed C-V behavior in our BST films. Furthermore, temperature dependent measurements gave evidence that, as expected, the form of the dielectric behavior changes near the bulk Curie point, but that the phase transition appears for some reason to be frustrated. Film thickness has been established to impact primarily the zero-bias permittivity through a thickness dependence of the first order coefficient of the LGD power series. Our analysis does indicate that if it results from a series-connected interfacial layer, that layer must be a nonlinear dielectric, as must the bulk of the film. The dielectric constant has been found to be composition dependent, reaching its highest values for compositions near the stoichiometric values. Furthermore, film stoichiometry has been established to strongly effect both the first order and third order coefficients of the LGD power series.

FELERION: a new approach for leakage power reduction

NASA Astrophysics Data System (ADS)

R, Anjana; Somkuwar, Ajay

2014-12-01

The circuit proposed in this paper simultaneously reduces the sub threshold leakage power and saves the state of art aspect of the logic circuits. Sleep transistors and PMOS-only logic are used to further reduce the leakage power. Sleep transistors are used as the keepers to reduce the sub threshold leakage current providing the low resistance path to the output. PMOS-only logic is used between the pull up and pull down devices to mitigate the leakage power further. Our proposed fast efficient leakage reduction circuit not only reduces the leakage current but also reduces the power dissipation. Power and delay are analyzed at the 32 nm BSIM4 model for a chain of four inverters, NAND, NOR and ISCAS-85 c17 benchmark circuits using DSCH3 and the Microwind tool. The simulation results reveal that our proposed approach mitigates leakage power by 90%-94% as compared to the conventional approach.

The ``Leakage Current Sentinel'': A novel plug-in socket device for online biomedical equipment electrical safety surveillance

NASA Astrophysics Data System (ADS)

Cappa, Paolo; Marinozzi, Franco; Sciuto, Salvatore Andrea

2000-07-01

The Leakage Current Sentinel (LCS) has been designed and implemented for the detection of hazardous situations caused by dangerous earth leakage current values in intensive care units and operating theaters. The device, designed and manufactured with full compliance of the high risk environment requirements, is able to monitor online the earth leakage current and detect ground wire faults. Operation utilizes a microammeter with an overall sensitivity of 2.5×104 V/A. In order to assure the reliability of the device in providing alarm signals, the simultaneous presence of absorbed power current is monitored by means of another ammeter with decreased sensitivity (3.0 V/A). The measured root mean square current values are compared with reference values in order to send signals to NAND and OR complementary metal-oxide-semiconductor gates to enable audible and visible alarms according to the possible hazardous cases examined in the article. The final LCS packaging was shaped as a wall socket adapter for common electromedical device power cord plugs, with particular attention to minimizing its dimensions and to provide analog voltage outputs for both measured leakage and power currents, in order to allow automatic data acquisition and computerized hazardous situation management. Finally, a personal computer based automatic measuring system has been configured to simultaneously monitor several LCSs installed in the same intensive care unit room and, as a consequence, to distinguish different hazardous scenarios and provide an adequate alert to the clinical personnel whose final decision is still required. The test results confirm the effectiveness and reliability of the LCS in giving an alert in case of leakage current anomalous values, either in case of a ground fault or in case of a dangerous leakage current.

Investigation of mercury thruster isolators. [service life

NASA Technical Reports Server (NTRS)

Mantenieks, M. A.

1973-01-01

Mercury ion thruster isolator lifetime tests were performed using different isolator materials and geometries. Tests were performed with and without the flow of mercury through the isolators in an oil diffusion pumped vacuum facility and cryogenically pumped bell jar. The onset of leakage current in isolators tested occurred in time intervals ranging from a few hours to many hundreds of hours. In all cases, surface contamination was responsible for the onset of leakage current and subsequent isolator failure. Rate of increase of leakage current and the leakage current level increased approximately exponentially with isolator temperature. Careful attention to shielding techniques and the elimination of sources of metal oxides appear to have eliminated isolator failures as a thruster life limiting mechanism.

Non-contact ultrasonic gas flow metering using air-coupled leaky Lamb waves.

PubMed

Fan, Zichuan; Jiang, Wentao; Wright, William M D

2018-04-23

This paper describes a completely non-contact ultrasonic method of gas flow metering using air-coupled leaky Lamb waves. To show proof of principle, a simplified representation of gas flow in a duct, comprising two separated thin isotropic plates with a gas flowing between them, has been modelled and investigated experimentally. An airborne compression wave emitted from an air-coupled capacitive ultrasonic transducer excited a leaky Lamb wave in the first plate in a non-contact manner. The leakage of this Lamb wave crossed the gas flow at an angle between the two plates as a compression wave, and excited a leaky Lamb wave in the second plate. An air-coupled capacitive ultrasonic transducer on the opposite side of this second plate then detected the airborne compression wave leakage from the second Lamb wave. As the gas flow shifted the wave field between the two plates, the point of Lamb wave excitation in the second plate was displaced in proportion to the gas flow rate. Two such measurements, in opposite directions, formed a completely non-contact contra-propagating Lamb wave flow meter, allowing measurement of the flow velocity between the plates. A COMSOL Multiphysics® model was used to visualize the wave fields, and accurately predicted the time differences that were then measured experimentally. Experiments using different Lamb wave frequencies and plate materials were also similarly verified. This entirely non-contact airborne approach to Lamb wave flow metering could be applied in place of clamp-on techniques in thin-walled ducts or pipes. Copyright © 2018 Elsevier B.V. All rights reserved.

Preparation and electrochemical capacitance performances of super-hydrophilic conducting polyaniline

NASA Astrophysics Data System (ADS)

Li, Xingwei; Li, Xiaohan; Dai, Na; Wang, Gengchao; Wang, Zhun

Super-hydrophilic conducting polyaniline was prepared by surface modification of polyaniline using tetraethyl orthosilicate in water/ethanol solution, whereas its conductivity was 4.16 S cm -1 at 25 °C. And its electrochemical capacitance performances as an electrode material were evaluated by the cyclic voltammetry and galvanostatic charge/discharge test in 0.1 M H 2SO 4 aqueous solution. Its initial specific capacitance was 500 F g -1 at a constant current density of 1.5 A g -1, and the capacitance still reached about 400 F g -1 after 5000 consecutive cycles. Moreover, its capacitance retention ratio was circa 70% with the growth of current densities from 1.5 to 20 A g -1, indicating excellent rate capability. It would be a promising electrode material for aqueous redox supercapacitors.

Modification of FN tunneling provoking gate-leakage current in ZTO (zinc-tin oxide) TFT by regulating the ZTO/SiO2 area ratio

NASA Astrophysics Data System (ADS)

Li, Jeng-Ting; Tsai, Ho-Lin; Lai, Wei-Yao; Hwang, Weng-Sing; Chen, In-Gann; Chen, Jen-Sue

2018-04-01

This study addresses the variation in gate-leakage current due to the Fowler-Nordheim (FN) tunneling of electrons through a SiO2 dielectric layer in zinc-tin oxide (ZTO) thin film transistors. It is shown that the gate-leakage current is not related to the absolute area of the ZTO active layer, but it is reduced by reducing the ZTO/SiO2 area ratio. The ZTO/SiO2 area ratio modulates the ZTO-SiO2 interface dipole strength as well as the ZTO-SiO2 conduction band offset and subsequently affects the FN tunneling current through the SiO2 layer, which provides a route that modifies the gate-leakage current.

SENSITIVITY OF THE HOUSE PRESSURE TEST FOR DUCT LEAKAGE TO VARIATIONS IN THE DISTRIBUTION OF AIR LEAKAGE IN THE HOUSE ENVELOPE

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

ANDREWS,J.W.

1998-12-01

The house pressure test for air leakage in ducts calculates the signed difference between the supply and return leakage from the response of the air pressure in the house to operation of the system fan. The currently accepted version of this calculation was based on particular assumptions about how the house envelope leakage is distributed between the walls, ceiling, and floor. This report generalizes the equation to account for an arbitrary distribution of envelope leakage. It concludes that the currently accepted equation is usually accurate to within {+-}5%, but in a small proportion of cases the results may diverge bymore » 50% or more.« less

Featuring of transient tunneling current by voltage pulse and application to an electrochemical biosensor

NASA Astrophysics Data System (ADS)

Yun, Jun Yeon; Lee, Won Cheol; Choi, Seong Wook; Park, Young June

2018-03-01

We suggest a voltage pulse method for detecting the transient tunneling current component (faradaic current component) in a metal/redox-active monolayer/electrolyte system. After applying the pulse to the metal electrode, the capacitive current prevails; therefore, it is difficult to extract the tunneling current, which carries information on the biochemical reactions occurring between the biomarkers in the electrolyte and the self-assembled monolayer (SAM) as the probe peptide system. Instead of waiting until the capacitive current diminishes, and thereby, the tunneling current also decreases, we try to extract the tunneling current in an early stage of the pulse. The method is based on the observation that the capacitive current becomes symmetrized in the positive and negative pulses after introducing the SAM on the metal electrode. When the energy level of the redox molecule is higher than the Fermi level of the metal under zero-bias condition, the tunneling current in the negative pulse can be extracted by subtracting the capacitive current obtained from the positive pulse, where the tunneling current is neglected. The experiment conducted for detecting trypsin as a biomarker shows that the method enhances the sensitivity and the specific-to-nonspecific ratio of the sensor device in the case of the nonspecific protein-abundant electrolyte solution, as evinced by cyclic voltammetry measurements in comparison.

Effect of hysteretic and non-hysteretic negative capacitance on tunnel FETs DC performance

NASA Astrophysics Data System (ADS)

Saeidi, Ali; Jazaeri, Farzan; Stolichnov, Igor; Luong, Gia V.; Zhao, Qing-Tai; Mantl, Siegfried; Ionescu, Adrian M.

2018-03-01

This work experimentally demonstrates that the negative capacitance effect can be used to significantly improve the key figures of merit of tunnel field effect transistor (FET) switches. In the proposed approach, a matching condition is fulfilled between a trained-polycrystalline PZT capacitor and the tunnel FET (TFET) gate capacitance fabricated on a strained silicon-nanowire technology. We report a non-hysteretic switch configuration by combining a homojunction TFET and a negative capacitance effect booster, suitable for logic applications, for which the on-current is increased by a factor of 100, the transconductance by 2 orders of magnitude, and the low swing region is extended. The operation of a hysteretic negative capacitance TFET, when the matching condition for the negative capacitance is fulfilled only in a limited region of operation, is also reported and discussed. In this late case, a limited improvement in the device performance is observed. Overall, the paper demonstrates the main beneficial effects of negative capacitance on TFETs are the overdrive and transconductance amplification, which exactly address the most limiting performances of current TFETs.

Transformer modeling for low- and mid-frequency electromagnetic transients simulation

NASA Astrophysics Data System (ADS)

Lambert, Mathieu

In this work, new models are developed for single-phase and three-phase shell-type transformers for the simulation of low-frequency transients, with the use of the coupled leakage model. This approach has the advantage that it avoids the use of fictitious windings to connect the leakage model to a topological core model, while giving the same response in short-circuit as the indefinite admittance matrix (BCTRAN) model. To further increase the model sophistication, it is proposed to divide windings into coils in the new models. However, short-circuit measurements between coils are never available. Therefore, a novel analytical method is elaborated for this purpose, which allows the calculation in 2-D of short-circuit inductances between coils of rectangular cross-section. The results of this new method are in agreement with the results obtained from the finite element method in 2-D. Furthermore, the assumption that the leakage field is approximately 2-D in shell-type transformers is validated with a 3-D simulation. The outcome of this method is used to calculate the self and mutual inductances between the coils of the coupled leakage model and the results are showing good correspondence with terminal short-circuit measurements. Typically, leakage inductances in transformers are calculated from short-circuit measurements and the magnetizing branch is calculated from no-load measurements, assuming that leakages are unimportant for the unloaded transformer and that magnetizing current is negligible during a short-circuit. While the core is assumed to have an infinite permeability to calculate short-circuit inductances, and it is a reasonable assumption since the core's magnetomotive force is negligible during a short-circuit, the same reasoning does not necessarily hold true for leakage fluxes in no-load conditions. This is because the core starts to saturate when the transformer is unloaded. To take this into account, a new analytical method is developed in this dissertation, which removes the contributions of leakage fluxes to properly calculate the magnetizing branches of the new models. However, in the new analytical method for calculating short-circuit inductances (as with other analytical methods), eddy-current losses are neglected. Similarly, winding losses are omitted in the coupled leakage model and in the new analytical method to remove leakage fluxes to calculate core parameters from no-load tests. These losses will be taken into account in future work. Both transformer models presented in this dissertation are based on the classical hypothesis that flux can be discretized into flux tubes, which is also the assumption used in a category of models called topological models. Even though these models are physically-based, there exist many topological models for a given transformer geometry. It is shown in this work that these differences can be explained in part through the concepts of divided and integral fluxes, and it is explained that divided approach is the result of mathematical manipulations, while the integral approach is more "physically-accurate". Furthermore, it is demonstrated, for the special case of a two-winding single-phase transformer, that the divided leakage inductances have to be nonlinear for both approaches to be equivalent. Even between models of the divided or integral approach models, there are differences, which arise from the particular choice of so-called flux paths" (tubes). This arbitrariness comes from the fact that with the classical hypothesis that magnetic flux can be confined into predefined flux tubes (leading to classical magnetic circuit theory), it is assumed that flux cannot leak from the sides of flux tubes. Therefore, depending on the transformer's operation conditions (degree of saturation, short-circuit, etc.), this can lead to different choices of flux tubes and different models. In this work, a new theoretical framework is developed to allow flux to leak from the sides of the tube, and generalized to include resistances and capacitances in what is called electromagnetic circuit theory. Also, it is explained that this theory is actually equivalent to what is called finite formulations (such as the finite element method), which bridges the gap between circuit theory and discrete electromagnetism. Therefore, this enables not only to develop topologically-correct transformer models, where electric and magnetic circuits are defined on dual meshes, but also rotating machine and transmission lines models (wave propagation can be taken into account).

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.

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

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.

Note: Expanding the bandwidth of the ultra-low current amplifier using an artificial negative capacitor.

PubMed

Xie, Kai; Liu, Yan; Li, XiaoPing; Guo, Lixin; Zhang, Hanlu

2016-04-01

The bandwidth and low noise characteristics are often contradictory in ultra-low current amplifier, because an inevitable parasitic capacitance is paralleled with the high value feedback resistor. In order to expand the amplifier's bandwidth, a novel approach was proposed by introducing an artificial negative capacitor to cancel the parasitic capacitance. The theory of the negative capacitance and the performance of the improved amplifier circuit with the negative capacitor are presented in this manuscript. The test was conducted by modifying an ultra-low current amplifier with a trans-impedance gain of 50 GΩ. The results show that the maximum bandwidth was expanded from 18.7 Hz to 3.3 kHz with more than 150 times of increase when the parasitic capacitance (∼0.17 pF) was cancelled. Meanwhile, the rise time decreased from 18.7 ms to 0.26 ms with no overshot. Any desired bandwidth or rise time within these ranges can be obtained by adjusting the ratio of cancellation of the parasitic and negative capacitance. This approach is especially suitable for the demand of rapid response to weak current, such as transient ion-beam detector, mass spectrometry analysis, and fast scanning microscope.

Degradation of Leakage Currents in Solid Tantalum Capacitors Under Steady-State Bias Conditions

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2010-01-01

Degradation of leakage currents in various types of solid tantalum capacitors under steady-state bias conditions was investigated at temperatures from 105 oC to 170 oC and voltages up to two times the rated voltage. Variations of leakage currents with time under highly accelerated life testing (HALT) and annealing, thermally stimulated depolarization currents, and I-V characteristics were measured to understand the conduction mechanism and the reason for current degradation. During HALT the currents increase gradually up to three orders of magnitude in some cases, and then stabilize with time. This degradation is reversible and annealing can restore the initial levels of leakage currents. The results are attributed to migration of positively charged oxygen vacancies in tantalum pentoxide films that diminish the Schottky barrier at the MnO2/Ta2O5 interface and increase electron injection. A simple model allows for estimation of concentration and mobility of oxygen vacancies based on the level of current degradation.

Leakage characterization of top select transistor for program disturbance optimization in 3D NAND flash

NASA Astrophysics Data System (ADS)

Zhang, Yu; Jin, Lei; Jiang, Dandan; Zou, Xingqi; Zhao, Zhiguo; Gao, Jing; Zeng, Ming; Zhou, Wenbin; Tang, Zhaoyun; Huo, Zongliang

2018-03-01

In order to optimize program disturbance characteristics effectively, a characterization approach that measures top select transistor (TSG) leakage from bit-line is proposed to quantify TSG leakage under program inhibit condition in 3D NAND flash memory. Based on this approach, the effect of Vth modulation of two-cell TSG on leakage is evaluated. By checking the dependence of leakage and corresponding program disturbance on upper and lower TSG Vth, this approach is validated. The optimal Vth pattern with high upper TSG Vth and low lower TSG Vth has been suggested for low leakage current and high boosted channel potential. It is found that upper TSG plays dominant role in preventing drain induced barrier lowering (DIBL) leakage from boosted channel to bit-line, while lower TSG assists to further suppress TSG leakage by providing smooth potential drop from dummy WL to edge of TSG, consequently suppressing trap assisted band-to-band tunneling current (BTBT) between dummy WL and TSG.

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.

A concise way to estimate the average density of interface states in an ITO-SiOx/n-Si heterojunction solar cell

NASA Astrophysics Data System (ADS)

Li, Y.; Han, B. C.; Gao, M.; Wan, Y. Z.; Yang, J.; Du, H. W.; Ma, Z. Q.

2017-09-01

On the basis of a photon-assisted high frequency capacitance-voltage (C-V) method (1 MHz C-V), an effective approach is developed to evaluate the average interface state density (Dit) of an ITO-SiOx/n-Si heterojunction structure. Tin-doped indium oxide (ITO) films with different thicknesses were directly deposited on (100) n-type crystalline silicon by magnetron sputtering to fabricate semiconductor-insulator-semiconductor (SIS) hetero-interface regions where an ultra-thin SiOx passivation layer was naturally created. The morphology of the SiOx layer was confirmed by X-ray photoelectron spectroscopy depth profiling and transmission electron microscope analysis. The thinness of this SiOx layer was the main reason for the SIS interface state density being more difficult to detect than that of a typical metal-oxide-semiconductor structure. A light was used for photon injection while measuring the C-V of the device, thus enabling the photon-assisted C-V measurement of the Dit. By quantifying decreases of the light-induced-voltage as a variation of the capacitance caused by parasitic charge at interface states the passivation quality within the interface of ITO-SiOx/n-Si could be reasonably evaluated. The average interface state density of these SIS devices was measured as 1.2-1.7 × 1011 eV-1 cm-2 and declined as the passivation layer was made thicker. The lifetime of the minority carriers, dark leakage current, and the other photovoltaic parameters of the devices were also used to determine the passivation.

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.

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.

Low dislocation density InAlN/AlN/GaN heterostructures grown on GaN substrates and the effects on gate leakage characteristics

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

Kotani, Junji, E-mail: kotani.junji-01@jp.fujitsu.com; Yamada, Atsushi; Ishiguro, Tetsuro

2016-04-11

This paper reports on the electrical characterization of Ni/Au Schottky diodes fabricated on InAlN high-electron-mobility transistor (HEMT) structures grown on low dislocation density free-standing GaN substrates. InAlN HEMT structures were grown on sapphire and GaN substrates by metal-organic vapor phase epitaxy, and the effects of threading dislocation density on the leakage characteristics of Ni/Au Schottky diodes were investigated. Threading dislocation densities were determined to be 1.8 × 10{sup 4 }cm{sup −2} and 1.2 × 10{sup 9 }cm{sup −2} by the cathodoluminescence measurement for the HEMT structures grown on GaN and sapphire substrates, respectively. Leakage characteristics of Ni/Au Schottky diodes were compared between the two samples, andmore » a reduction of the leakage current of about three to four orders of magnitude was observed in the forward bias region. For the high reverse bias region, however, no significant improvement was confirmed. We believe that the leakage current in the low bias region is governed by a dislocation-related Frenkel–Poole emission, and the leakage current in the high reverse bias region originates from field emission due to the large internal electric field in the InAlN barrier layer. Our results demonstrated that the reduction of dislocation density is effective in reducing leakage current in the low bias region. At the same time, it was also revealed that another approach will be needed, for instance, band modulation by impurity doping and insertion of insulating layers beneath the gate electrodes for a substantial reduction of the gate leakage current.« less

Reduction of gate leakage current on AlGaN/GaN high electron mobility transistors by electron-beam irradiation.

PubMed

Oh, S K; Song, C G; Jang, T; Kim, Kwang-Choong; Jo, Y J; Kwak, J S

2013-03-01

This study examined the effect of electron-beam (E-beam) irradiation on the AIGaN/GaN HEMTs for the reduction of gate leakage. After E-beam irradiation, the gate leakage current significantly decreased from 2.68 x 10(-8) A to 4.69 x 10(-9) A at a drain voltage of 10 V. The maximum drain current density of the AIGaN/GaN HEMTs with E-beam irradiation increased 14%, and the threshold voltage exhibited a negative shift, when compared to that of the AIGaN/GaN HEMTs before E-beam irradiation. These results strongly suggest that the reduction of gate leakage current resulted from neutralization nitrogen vacancies and removing of oxygen impurities.

Design optimization of high frequency transformer with controlled leakage inductance for current fed dual active bridge converter

NASA Astrophysics Data System (ADS)

Jung, Tae-Uk; Kim, Myung-Hwan; Yoo, Jin-Hyung

2018-05-01

Current fed dual active bridge converters for photovoltaic generation may typically require a given leakage or extra inductance in order to provide proper control of the currents. Therefore, the many researches have been focused on the leakage inductance control of high frequency transformer to integrate an extra inductor. In this paper, an asymmetric winding arrangement to get the controlled leakage inductance for the high frequency transformer is proposed to improve the efficiency of the current fed dual active bridge converter. In order to accurate analysis, a coupled electromagnetic analysis model of transformer connected with high frequency switching circuit is used. A design optimization procedure for high efficiency is also presented using design analysis model, and it is verified by the experimental result.

Effect of incorporation of nitrogen atoms in Al2O3 gate dielectric of wide-bandgap-semiconductor MOSFET on gate leakage current and negative fixed charge

NASA Astrophysics Data System (ADS)

Kojima, Eiji; Chokawa, Kenta; Shirakawa, Hiroki; Araidai, Masaaki; Hosoi, Takuji; Watanabe, Heiji; Shiraishi, Kenji

2018-06-01

We performed first-principle calculations to investigate the effect of incorporation of N atoms into Al2O3 gate dielectrics. Our calculations show that the defect levels generated by VO in Al2O3 are the origin of the stress-induced gate leakage current and that VOVAl complexes in Al2O3 cause negative fixed charge. We revealed that the incorporation of N atoms into Al2O3 eliminates the VO defect levels, reducing the stress-induced gate leakage current. Moreover, this suppresses the formation of negatively charged VOVAl complexes. Therefore, AlON can reduce both stress-induced gate leakage current and negative fixed charge in wide-bandgap-semiconductor MOSFETs.

Hot-Electron-Induced Device Degradation during Gate-Induced Drain Leakage Stress

NASA Astrophysics Data System (ADS)

Kim, Kwang-Soo; Han, Chang-Hoon; Lee, Jun-Ki; Kim, Dong-Soo; Kim, Hyong-Joon; Shin, Joong-Shik; Lee, Hea-Beoum; Choi, Byoung-Deog

2012-11-01

We studied the interface state generation and electron trapping by hot electrons under gate-induced drain leakage (GIDL) stress in p-type metal oxide semiconductor field-effect transistors (P-MOSFETs), which are used as the high-voltage core circuit of flash memory devices. When negative voltage was applied to a drain in the off-state, a GIDL current was generated, but when high voltage was applied to the drain, electrons had a high energy. The hot electrons produced the interface state and electron trapping. As a result, the threshold voltage shifted and the off-state leakage current (trap-assisted drain junction leakage current) increased. On the other hand, electron trapping mitigated the energy band bending near the drain and thus suppressed the GIDL current generation.

InP electroluminescence as a tool to directly monitor carrier leakage in InGaAsP/InP buried heterostructure lasers

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

Stern, M.B.; Brody, E.; Sowell, B.

1987-12-15

Direct measurements of homojunction and heterojunction carrier leakage currents in InGaAsP/InP buried heterostructure lasers have been made by monitoring the electroluminescence (EL) at 0.96 ..mu..m in the InP confinement layers. These EL measurements show directly, for the first time, a correlation between homojunction leakage currents and the sublinearity in the 1.3-..mu..m light output-current characteristic. The observed decrease in the 0.96-..mu..m intensity with increasing p-dopant concentration is a direct confirmation that heterojunction leakage is reduced when the doping level in the p-InP confinement layer is increased.

Manganese oxide micro-supercapacitors with ultra-high areal capacitance

NASA Astrophysics Data System (ADS)

Wang, Xu; Myers, Benjamin D.; Yan, Jian; Shekhawat, Gajendra; Dravid, Vinayak; Lee, Pooi See

2013-05-01

A symmetric micro-supercapacitor is constructed by electrochemically depositing manganese oxide onto micro-patterned current collectors. High surface-to-volume ratio of manganese oxide and short diffusion distance between electrodes give an ultra-high areal capacitance of 56.3 mF cm-2 at a current density of 27.2 μA cm-2.A symmetric micro-supercapacitor is constructed by electrochemically depositing manganese oxide onto micro-patterned current collectors. High surface-to-volume ratio of manganese oxide and short diffusion distance between electrodes give an ultra-high areal capacitance of 56.3 mF cm-2 at a current density of 27.2 μA cm-2. Electronic supplementary information (ESI) available: Experimental procedures; optical images of micro-supercapacitors; areal capacitances of samples M-0.3C, M-0.6C and M-0.9C; illustration of interdigital finger electrodes; Nyquist plot of Co(OH)2 deposited on micro-electrodes. See DOI: 10.1039/c3nr00210a

Current source enhancements in Electrical Impedance Spectroscopy (EIS) to cancel unwanted capacitive effects

NASA Astrophysics Data System (ADS)

Zarafshani, Ali; Bach, Thomas; Chatwin, Chris; Xiang, Liangzhong; Zheng, Bin

2017-03-01

Electrical Impedance Spectroscopy (EIS) has emerged as a non-invasive imaging modality to detect and quantify functional or electrical properties related to the suspicious tumors in cancer screening, diagnosis and prognosis assessment. A constraint on EIS systems is that the current excitation system suffers from the effects of stray capacitance having a major impact on the hardware subsystem as the EIS is an ill-posed inverse problem which depends on the noise level in EIS measured data and regularization parameter in the reconstruction algorithm. There is high complexity in the design of stable current sources, with stray capacitance reducing the output impedance and bandwidth of the system. To confront this, we have designed an EIS current source which eliminates the effect of stray capacitance and other impacts of the capacitance via a variable inductance. In this paper, we present a combination of operational CCII based on a generalized impedance converter (OCCII-GIC) with a current source. The aim of this study is to use the EIS system as a biomedical imaging technique, which is effective in the early detection of breast cancer. This article begins with the theoretical description of the EIS structure, current source topologies and proposes a current conveyor in application of a Gyrator to eliminate the current source limitations and its development followed by simulation and experimental results. We demonstrated that the new design could achieve a high output impedance over a 3MHz frequency bandwidth when compared to other types of GIC circuits combined with an improved Howland topology.

Determination of the Steady State Leakage Current in Structures with Ferroelectric Ceramic Films

NASA Astrophysics Data System (ADS)

Podgornyi, Yu. V.; Vorotilov, K. A.; Sigov, A. S.

2018-03-01

Steady state leakage currents have been investigated in capacitor structures with ferroelectric solgel films of lead zirconate titanate (PZT) formed on silicon substrates with a lower Pt electrode. It is established that Pt/PZT/Hg structures, regardless of the PZT film thickness, are characterized by the presence of a rectifying contact similar to p-n junction. The steady state leakage current in the forward direction increases with a decrease in the film thickness and is determined by the ferroelectric bulk conductivity.

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.

Improving off-state leakage characteristics for high voltage AlGaN/GaN-HFETs on Si substrates

NASA Astrophysics Data System (ADS)

Moon, Sung-Woon; Twynam, John; Lee, Jongsub; Seo, Deokwon; Jung, Sungdal; Choi, Hong Goo; Shim, Heejae; Yim, Jeong Soon; Roh, Sungwon D.

2014-06-01

We present a reliable process and design technique for realizing high voltage AlGaN/GaN hetero-junction field effect transistors (HFETs) on Si substrates with very low and stable off-state leakage current characteristics. In this work, we have investigated the effects of the surface passivation layer, prepared by low pressure chemical vapor deposition (LPCVD) of silicon nitride (SiNx), and gate bus isolation design on the off-state leakage characteristics of metal-oxide-semiconductor (MOS) gate structure-based GaN HFETs. The surface passivated devices with gate bus isolation fully surrounding the source and drain regions showed extremely low off-state leakage currents of less than 20 nA/mm at 600 V, with very small variation. These techniques were successfully applied to high-current devices with 80-mm gate width, yielding excellent off-state leakage characteristics within a drain voltage range 0-700 V.

Facile fabrication of cobalt oxalate nanostructures with superior specific capacitance and super-long cycling stability

NASA Astrophysics Data System (ADS)

Cheng, Guanhua; Si, Conghui; Zhang, Jie; Wang, Ying; Yang, Wanfeng; Dong, Chaoqun; Zhang, Zhonghua

2016-04-01

Transition metal oxalate materials have shown huge competitive advantages for applications in supercapacitors. Herein, nanostructured cobalt oxalate supported on cobalt foils has been facilely fabricated by anodization, and could directly serve as additive/binder-free electrodes for supercapacitors. The as-prepared cobalt oxalate electrodes present superior specific capacitance of 1269 F g-1 at the current density of 6 A g-1 in the galvanostatic charge/discharge test. Moreover, the retained capacitance is as high as 87.2% as the current density increases from 6 A g-1 to 30 A g-1. More importantly, the specific capacitance of cobalt oxalate retains 91.9% even after super-long cycling of 100,000 cycles. In addition, an asymmetric supercapacitor assembled with cobalt oxalate (positive electrode) and activated carbon (negative electrode) demonstrates excellent capacitive performance with high energy density and power density.

21 CFR 870.2640 - Portable leakage current alarm.

Code of Federal Regulations, 2014 CFR

2014-04-01

... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2640 Portable... the electrical leakage current between any two points of an electrical system and to sound an alarm if...

21 CFR 870.2640 - Portable leakage current alarm.

Code of Federal Regulations, 2013 CFR

2013-04-01

... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2640 Portable... the electrical leakage current between any two points of an electrical system and to sound an alarm if...

21 CFR 870.2640 - Portable leakage current alarm.

Code of Federal Regulations, 2012 CFR

2012-04-01

... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2640 Portable... the electrical leakage current between any two points of an electrical system and to sound an alarm if...

Highly microporous carbons derived from a complex of glutamic acid and zinc chloride for use in supercapacitors

NASA Astrophysics Data System (ADS)

Dong, Xiao-Ling; Lu, An-Hui; He, Bin; Li, Wen-Cui

2016-09-01

The selection of carbon precursor is an important factor when designing carbon materials. In this study, a complex derived from L-glutamic acid and zinc chloride was used to prepare highly microporous carbons via facile pyrolysis. L-glutamic acid, a new carbon precursor with nitrogen functionality, coordinated with zinc chloride resulted in a homogeneous distribution of Zn2+ on the molecular level. During pyrolysis, the evaporation of the in situ formed zinc species creates an abundance of micropores together with the inert gases. The obtained carbons exhibit high specific surface area (SBET: 1203 m2 g-1) and a rich nitrogen content (4.52 wt%). In excess of 89% of the pore volume consists of micropores with pore size ranging from 0.5 to 1.2 nm. These carbons have been shown to be suitable for use as supercapacitor electrodes, and have been tested in 6 M KOH where a capacitance of 217 F g-1 was achieved at a current density of 0.5 A g-1. A long cycling life of 30 000 cycles was achieved at a current density of 1 A g-1, with only a 9% loss in capacity. The leakage current through a two-electrode device was measured as 2.3 μA per mg of electrode and the self-discharge characteristics were minimal.

Chemical vapor deposited monolayer MoS2 top-gate MOSFET with atomic-layer-deposited ZrO2 as gate dielectric

NASA Astrophysics Data System (ADS)

Hu, Yaoqiao; Jiang, Huaxing; Lau, Kei May; Li, Qiang

2018-04-01

For the first time, ZrO2 dielectric deposition on pristine monolayer MoS2 by atomic layer deposition (ALD) is demonstrated and ZrO2/MoS2 top-gate MOSFETs have been fabricated. ALD ZrO2 overcoat, like other high-k oxides such as HfO2 and Al2O3, was shown to enhance the MoS2 channel mobility. As a result, an on/off current ratio of over 107, a subthreshold slope of 276 mV dec-1, and a field-effect electron mobility of 12.1 cm2 V-1 s-1 have been achieved. The maximum drain current of the MOSFET with a top-gate length of 4 μm and a source/drain spacing of 9 μm is measured to be 1.4 μA μm-1 at V DS = 5 V. The gate leakage current is below 10-2 A cm-2 under a gate bias of 10 V. A high dielectric breakdown field of 4.9 MV cm-1 is obtained. Gate hysteresis and frequency-dependent capacitance-voltage measurements were also performed to characterize the ZrO2/MoS2 interface quality, which yielded an interface state density of ˜3 × 1012 cm-2 eV-1.

Effect of aqueous electrolytes on the electrochemical behaviors of supercapacitors based on hierarchically porous carbons

NASA Astrophysics Data System (ADS)

Zhang, Xiaoyan; Wang, Xianyou; Jiang, Lanlan; Wu, Hao; Wu, Chun; Su, Jingcang

2012-10-01

Hierarchically porous carbons (HPCs) have been prepared by sol-gel self-assembly technology with nickel oxide and surfactant as the dual template. The porous carbons are further activated by nitric acid. The electrochemical behaviors of supercapacitors using HPCs as electrode material in different aqueous electrolytes, e.g., (NH4)2SO4, Na2SO4, H2SO4 and KOH are studied by cyclic voltametry, galvanostatic charge/discharge, cyclic life, leakage current, self-discharge and electrochemical impedance spectroscopy. The results demonstrate that the supercapacitors in various electrolytes perform definitely capacitive behaviors; especially in 6 M KOH electrolyte the supercapacitor represents the best electrochemical performance, the shortest relaxation time, and nearly ideal polarisability. The energy density of 8.42 Wh kg-1 and power density of 17.22 kW kg-1 are obtained at the operated voltage window of 1.0 V. Especially, the energy density of 11.54 Wh kg-1 and power density of 10.58 kW kg-1 can be achieved when the voltage is up to 1.2 V.

Optimization of PEDOT films in ionic liquid supercapacitors: demonstration as a power source for polymer electrochromic devices.

PubMed

Österholm, Anna M; Shen, D Eric; Dyer, Aubrey L; Reynolds, John R

2013-12-26

We report on the optimization of the capacitive behavior of poly(3,4-ethylenedioxythiophene) (PEDOT) films as polymeric electrodes in flexible, Type I electrochemical supercapacitors (ESCs) utilizing ionic liquid (IL) and organic gel electrolytes. The device performance was assessed based on figures of merit that are critical to evaluating the practical utility of electroactive polymer ESCs. PEDOT/IL devices were found to be highly stable over hundreds of thousands of cycles and could be reversibly charged/discharged at scan rates between 500 mV/s and 2 V/s depending on the polymer loading. Furthermore, these devices exhibit leakage currents and self-discharge rates that are comparable to state of the art electrochemical double-layer ESCs. Using an IL as device electrolyte allowed an extension of the voltage window of Type I ESCs by 60%, resulting in a 2.5-fold increase in the energy density obtained. The efficacies of tjese PEDOT ESCs were assessed by using them as a power source for a high-contrast and fast-switching electrochromic device, demonstrating their applicability in small organic electronic-based devices.

Improved sensing characteristics of dual-gate transistor sensor using silicon nanowire arrays defined by nanoimprint lithography.

PubMed

Lim, Cheol-Min; Lee, In-Kyu; Lee, Ki Joong; Oh, Young Kyoung; Shin, Yong-Beom; Cho, Won-Ju

2017-01-01

This work describes the construction of a sensitive, stable, and label-free sensor based on a dual-gate field-effect transistor (DG FET), in which uniformly distributed and size-controlled silicon nanowire (SiNW) arrays by nanoimprint lithography act as conductor channels. Compared to previous DG FETs with a planar-type silicon channel layer, the constructed SiNW DG FETs exhibited superior electrical properties including a higher capacitive-coupling ratio of 18.0 and a lower off-state leakage current under high-temperature stress. In addition, while the conventional planar single-gate (SG) FET- and planar DG FET-based pH sensors showed the sensitivities of 56.7 mV/pH and 439.3 mV/pH, respectively, the SiNW DG FET-based pH sensors showed not only a higher sensitivity of 984.1 mV/pH, but also a lower drift rate of 0.8% for pH-sensitivity. This demonstrates that the SiNW DG FETs simultaneously achieve high sensitivity and stability, with significant potential for future biosensing applications.

Study of the H2O/Al2O3 Interface and the Acting Mechanism of Water in the Working Electrolyte

NASA Astrophysics Data System (ADS)

Jia, Ming; Li, Qiang; Li, Lixiang; Cao, Liang; Yang, Juan; Zhou, Xiangyang; Ai, Liang

2018-04-01

Using a working electrolyte containing mixed solvents of ethylene glycol and N,N-dimethylformamide, this paper presents a study of the reactions on the H2O/Al2O3 interface with sum frequency vibrational spectroscopy and the effects of different water content on the performance of the working electrolyte and an aluminum electrolytic capacitor and summarizes the rules of the variations in the performance parameters of the working electrolyte and aluminum electrolytic capacitor with respect to the water content. The results demonstrate that, when the water content is increased from 2.5 to 15%, the conductivity of the working electrolyte increased by 930 μS/cm, and the sparking voltage decreased by 27 V. Also, the increased water content causes lower oxidation efficiency and lower thermal stability. The leakage current of the aluminum electrolytic capacitor after high-temperature storage increases with an increase in the water content, and the attenuation rate of capacitor's the low-temperature capacitance decreases with an increase in the water content.

Chemical shift and surface characteristics of Al-doped ZnO thin film on SiOC dielectrics.

PubMed

Oh, Teresa; Lee, Sang Yeol

2013-10-01

Aluminum doped zinc oxide (AZO) films were fabricated on SiOC/p-Si wafer and SiOC film was prepared on a p-type Si substrate with the SiC target at oxygen ambient with the gas flow rate of 5-30 sccm by a RF magnetron sputter. C-V curve of SiOC/Si wafer was measured to observe the relationship between the polarity of SiOC dielectrics and the change of capacitance depending on oxygen gas flow rate. The SiOC film could be controlled to be polar or nonpolar, and their surface energy was changed depending on the polarity. Smooth surface is essential to improve the TFT performance. AZO-TFTs used smooth SiOC film with low polarity as a gate insulator was observed to show low leakage current (IL) and low subthreshold voltage swing. It is proposed that SiOC film with high degree amorphous structure as a gate insulator between AZO and Si wafer could solve problems of the mismatched interfaces, which was originated from the electron scattering due to the grain boundary.

Improved sensing characteristics of dual-gate transistor sensor using silicon nanowire arrays defined by nanoimprint lithography

NASA Astrophysics Data System (ADS)

Lim, Cheol-Min; Lee, In-Kyu; Lee, Ki Joong; Oh, Young Kyoung; Shin, Yong-Beom; Cho, Won-Ju

2017-12-01

This work describes the construction of a sensitive, stable, and label-free sensor based on a dual-gate field-effect transistor (DG FET), in which uniformly distributed and size-controlled silicon nanowire (SiNW) arrays by nanoimprint lithography act as conductor channels. Compared to previous DG FETs with a planar-type silicon channel layer, the constructed SiNW DG FETs exhibited superior electrical properties including a higher capacitive-coupling ratio of 18.0 and a lower off-state leakage current under high-temperature stress. In addition, while the conventional planar single-gate (SG) FET- and planar DG FET-based pH sensors showed the sensitivities of 56.7 mV/pH and 439.3 mV/pH, respectively, the SiNW DG FET-based pH sensors showed not only a higher sensitivity of 984.1 mV/pH, but also a lower drift rate of 0.8% for pH-sensitivity. This demonstrates that the SiNW DG FETs simultaneously achieve high sensitivity and stability, with significant potential for future biosensing applications.

Characteristics and production of tantalum powders for solid-electrolyte capacitors

NASA Astrophysics Data System (ADS)

Yoon, Jae Sik; Kim, Byung Il

The effects of using K 2TaF 7 as the raw material and sodium as the reducing agent on the characteristics of tantalum powder are investigated. Batch-type metallothermic reduction (BTMR) is used to charge the reactor with the raw material and the reducing agent, and external continuous supply metallothermic reduction (ESMR) is used to supply the raw material and the reducing agent at a constant rate at the temperature of the reduction reaction. In the case of ESMR, the yield increases by several tens of percent because of the uniform reaction between the raw material and the reducing agent. It is possible to obtain a powder of over 99.5% purity. The powder particles obtained with BTMR are relatively large (4-6 μm) and have a coarse lamellar shape, while those prepared via ESMR are of uniform 1-2 μm size with a coral-like shape. Measurements of the electric properties show that the leakage current and the dielectric dissipation are low with higher reliability in ESMR than in BTMR, and the capacitance is 26,000 and 8400 CV for ESMR and in BTMR, respectively.

Reduction of surface leakage current by surface passivation of CdZn Te and other materials using hyperthermal oxygen atoms

DOEpatents

Hoffbauer, Mark A.; Prettyman, Thomas H.

2001-01-01

Reduction of surface leakage current by surface passivation of Cd.sub.1-x Zn.sub.x Te and other materials using hyperthermal oxygen atoms. Surface effects are important in the performance of CdZnTe room-temperature radiation detectors used as spectrometers since the dark current is often dominated by surface leakage. A process using high-kinetic-energy, neutral oxygen atoms (.about.3 eV) to treat the surface of CdZnTe detectors at or near ambient temperatures is described. Improvements in detector performance include significantly reduced leakage current which results in lower detector noise and greater energy resolution for radiation measurements of gamma- and X-rays, thereby increasing the accuracy and sensitivity of measurements of radionuclides having complex gamma-ray spectra, including special nuclear materials.

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

Bean, Bruce Palmer

The effects of ether and halothane on membrane currents in the voltage clamped crayfish giant axon membrane were investigated. Concentrations of ether up to 300 mM and of halothane up to 32 mM had no effect on resting potential or leakage conductance. Ether and halothane reduced the size of sodium currents without changing the voltage dependence of the peak currents or their reversal potential. Ether and halothane also produced a reversible, dose-dependent speeding of sodium current decay at all membrane potentials. Ether reduced the time constants for inactivation, and also shifted the midpoint of the steady-state inactivation curve in themore » hyperpolarizing direction. Potassium currents were smaller with ether present, with no change in the voltage dependence of steady-state currents. The activation of potassium channels was faster with ether present. There was no apparent change in the capacitance of the crayfish giant axon membrane with ether concentrations of up to 100 mM. Experiments on sodium channel inactivation kinetics were performed using 4-aminopyridine to block potassium currents. Sodium currents decayed with a time course generally fit well by a single exponential. The time constant of decay was a steep function of voltage, especially in the negative resistance region of the peak current vs voltage relation.The time course of inactivation was very similar to that of the decay of the current at the same potential. The measurement of steady-state inactivation curves with different test pulses showed no shifts along the voltage asix. The voltage-dependence of the integral of sodium conductance was measured to test models of sodium channel inactivation in which channels must open before inactivating; the results appear inconsistent with some of the simplest cases of such models.« less

Synthesis and Characterization of Self-Standing and Highly Flexible δ-MnO2@CNTs/CNTs Composite Films for Direct Use of Supercapacitor Electrodes.

PubMed

Wu, Peng; Cheng, Shuang; Yang, Lufeng; Lin, Zhiqiang; Gui, Xuchun; Ou, Xing; Zhou, Jun; Yao, Minghai; Wang, Mengkun; Zhu, Yuanyuan; Liu, Meilin

2016-09-14

Self-standing and flexible films worked as pseudocapacitor electrodes have been fabricated via a simple vacuum-filtration procedure to stack δ-MnO2@carbon nanotubes (CNTs) composite layer and pure CNT layer one by one with CNT layers ended. The lightweight CNTs layers served as both current collector and supporter, while the MnO2@CNTs composite layers with birnessite-type MnO2 worked as active layer and made the main contribution to the capacitance. At a low discharge current of 0.2 A g(-1), the layered films displayed a high areal capacitance of 0.293 F cm(-2) with a mass of 1.97 mg cm(-2) (specific capacitance of 149 F g(-1)) and thickness of only 16.5 μm, and hence an volumetric capacitance of about 177.5 F cm(-3). Moreover, the films also exhibited a good rate capability (only about 15% fading for the capacitance when the discharge current increased to 5 A g(-1) from 0.2 A g(-1)), outstanding cycling stability (about 90% of the initial capacitance was remained after 5,000 cycles) and high flexibility (almost no performance change when bended to different angles). In addition, the capacitance of the films increased proportionally with the stacked layers and the geometry area. E.g., when the stacked layers were three times many with a mass of 6.18 mg cm(-2), the areal capacitance of the films was increased to 0.764 F cm(-2) at 0.5 A g(-1), indicating a high electronic conductivity. It is not overstated to say that the flexible and lightweight layered films emerged high potential for future practical applications as supercapacitor electrodes.

Note: Expanding the bandwidth of the ultra-low current amplifier using an artificial negative capacitor

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

Xie, Kai, E-mail: kaixie@mail.xidian.edu.cn; Liu, Yan; Li, XiaoPing

2016-04-15

The bandwidth and low noise characteristics are often contradictory in ultra-low current amplifier, because an inevitable parasitic capacitance is paralleled with the high value feedback resistor. In order to expand the amplifier’s bandwidth, a novel approach was proposed by introducing an artificial negative capacitor to cancel the parasitic capacitance. The theory of the negative capacitance and the performance of the improved amplifier circuit with the negative capacitor are presented in this manuscript. The test was conducted by modifying an ultra-low current amplifier with a trans-impedance gain of 50 GΩ. The results show that the maximum bandwidth was expanded from 18.7more » Hz to 3.3 kHz with more than 150 times of increase when the parasitic capacitance (∼0.17 pF) was cancelled. Meanwhile, the rise time decreased from 18.7 ms to 0.26 ms with no overshot. Any desired bandwidth or rise time within these ranges can be obtained by adjusting the ratio of cancellation of the parasitic and negative capacitance. This approach is especially suitable for the demand of rapid response to weak current, such as transient ion-beam detector, mass spectrometry analysis, and fast scanning microscope.« less

Band to Band Tunneling (BBT) Induced Leakage Current Enhancement in Irradiated Fully Depleted SOI Devices

NASA Technical Reports Server (NTRS)

Adell, Phillipe C.; Barnaby, H. J.; Schrimpf, R. D.; Vermeire, B.

2007-01-01

We propose a model, validated with simulations, describing how band-to-band tunneling (BBT) affects the leakage current degradation in some irradiated fully-depleted SOI devices. The dependence of drain current on gate voltage, including the apparent transition to a high current regime is explained.

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

Capacitively-coupled inductive sensors for measurements of pulsed currents and pulsed magnetic fields

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

Ekdahl, C.A.

In experiments involving pulsed high magnetic fields the appearance of the full induced voltage at the output terminals of large-area inductive sensors such as diamagnetic loops and Rogowski belts imposes severe requirements on the insulation near the output. Capacitive detection of the inductive-sensor output voltage provides an ideal geometry for high-voltage insulation, and also accomplishes the necessary voltage division. An inductive-shunt current monitor was designed to utilize the capacitive-detection principle. The contruction of this device and its performance are described in this paper.

Extended Life PZT Stack Test Fixture

NASA Technical Reports Server (NTRS)

Badescu, Mircea; Sherrit, S.; Bao, X.; Aldrich, J.; Bar-Cohen, Y.; Jones, C.

2009-01-01

Piezoelectric stacks are being sought to be used as actuators for precision positioning and deployment of mechanisms in future planetary missions. Beside the requirement for very high operation reliability, these actuators are required for operation at space environments that are considered harsh compared to normal terrestrial conditions.These environmental conditions include low and high temperatures and vacuum or high pressure. Additionally, the stacks are subjected to high stress and in some applications need to operate with a very long lifetime durability.Many of these requirements are beyond the current industry design margins for nominal terrestrial applications. In order to investigate some of the properties that will indicate the durability of such actuators and their limitations we have developed a new type of test fixture that can be easily integrated in various test chambers for simulating environmental conditions, can provide access for multiple measurements while being exposed to adjustable stress levels. We designed and built two test fixtures and these fixtures were made to be adjustable for testing stacks with different dimensions and can be easily used in small or large numbers. The properties that were measured using these fixtures include impedance, capacitance, dielectric loss factor, leakage current, displacement, breakdown voltage, and lifetime performance. The fixtures characteristics and the test capabilities are presented in this paper.

Electrical properties of GaN-based metal-insulator-semiconductor structures with Al2O3 deposited by atomic layer deposition using water and ozone as the oxygen precursors

NASA Astrophysics Data System (ADS)

Kubo, Toshiharu; Freedsman, Joseph J.; Iwata, Yasuhiro; Egawa, Takashi

2014-04-01

Al2O3 deposited by atomic layer deposition (ALD) was used as an insulator in metal-insulator-semiconductor (MIS) structures for GaN-based MIS-devices. As the oxygen precursors for the ALD process, water (H2O), ozone (O3), and both H2O and O3 were used. The chemical characteristics of the ALD-Al2O3 surfaces were investigated by x-ray photoelectron spectroscopy. After fabrication of MIS-diodes and MIS-high-electron-mobility transistors (MIS-HEMTs) with the ALD-Al2O3, their electrical properties were evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The threshold voltage of the C-V curves for MIS-diodes indicated that the fixed charge in the Al2O3 layer is decreased when using both H2O and O3 as the oxygen precursors. Furthermore, MIS-HEMTs with the H2O + O3-based Al2O3 showed good dc I-V characteristics without post-deposition annealing of the ALD-Al2O3, and the drain leakage current in the off-state region was suppressed by seven orders of magnitude.

Characterization of high-{kappa} LaLuO{sub 3} thin film grown on AlGaN/GaN heterostructure by molecular beam deposition

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

Yang Shu; Huang Sen; Chen Hongwei

2011-10-31

We report the study of high-dielectric-constant (high-{kappa}) dielectric LaLuO{sub 3} (LLO) thin film that is grown on AlGaN/GaN heterostructure by molecular beam deposition (MBD). The physical properties of LLO on AlGaN/GaN heterostrucure have been investigated with atomic force microscopy, x-ray photoelectron spectroscopy, and TEM. It is revealed that the MBD-grown 16 nm-thick LLO film is polycrystalline with a thin ({approx}2 nm) amorphous transition layer at the LLO/GaN interface. The bandgap of LLO is derived as 5.3 {+-} 0.04 eV from O1s energy loss spectrum. Capacitance-voltage (C-V) characteristics of a Ni-Au/LLO/III-nitride metal-insulator-semiconductor diode exhibit small frequency dispersion (<2%) and reveal amore » high effective dielectric constant of {approx}28 for the LLO film. The LLO layer is shown to be effective in suppressing the reverse and forward leakage current in the MIS diode. In particular, the MIS diode forward current is reduced by 7 orders of magnitude at a forward bias of 1 V compared to a conventional Ni-Au/III-nitride Schottky diode.« less

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.

Leakage Currents and Gas Generation in Advanced Wet Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2015-01-01

Currently, military grade, established reliability wet tantalum capacitors are among the most reliable parts used for space applications. This has been achieved over the years by extensive testing and improvements in design and materials. However, a rapid insertion of new types of advanced, high volumetric efficiency capacitors in space systems without proper testing and analysis of degradation mechanisms might increase risks of failures. The specifics of leakage currents in wet electrolytic capacitors is that the conduction process is associated with electrolysis of electrolyte and gas generation resulting in building up of internal gas pressure in the parts. The risk associated with excessive leakage currents and increased pressure is greater for high value advanced wet tantalum capacitors, but it has not been properly evaluated yet. In this work, in Part I, leakages currents in various types of tantalum capacitors have been analyzed in a wide range of voltages, temperatures, and time under bias. Gas generation and the level of internal pressure have been calculated in Part II for different case sizes and different hermeticity leak rates to assess maximal allowable leakage currents. Effects related to electrolyte penetration to the glass seal area have been studied and the possibility of failures analyzed in Part III. Recommendations for screening and qualification to reduce risks of failures have been suggested.

Fabrication and Analysis of a Selectively Contacted Dual Channel High Electron Mobility Field-Effect Transistor

NASA Astrophysics Data System (ADS)

Khanna, Ravi

1992-01-01

A selectively contacted dual-channel high electron mobility transistor (SCD-CHEMT) has been designed, fabricated, and electrically characterized, in order to better understand the properties of two layers of two-dimensional electron gases (2DEGs) confined within a quantum well. The 2DEGs are placed under a Schottky barrier control gate which modulates their sheet charge densities, and by use of auxiliary Schottky barrier gates and two levels of ohmic contacts, electrical contacts to the individual channels in which each 2DEG resides is achieved. The design of the dual channel FET structure, and its practical realization by recourse to process development and fabrication are described, as are the techniques, results, and interpretations of electrical characterizations used to analyze the completed device. Critical fabrication procedures involving photolithography, etching, deposition, shallow and deep ohmic contact formation, and gate formation are developed, and a simple technique to reduce gate leakage by photo-oxidation is demonstrated. Analysis of the completed device is performed using one-dimensional band diagram simulations, magnetotransport and electrical measurements. Magnetotransport studies establish the existence of two 2DEGs within the quantum well at 4K. Drain current vs. drain voltage, and transconductance vs. gate voltage characteristics at room temperature confirm the presence of two 2DEGs and show that current flow between them occurs easily at room temperature. Carrier electron mobility profiles are taken of the 2DEGs and show that the lower 2DEG has a mobility comparable to that of a 2DEG formed at a normal interface, indicating that the "inverted interface problem" has been overcome. Capacitance vs. gate voltage measurements are taken, which are consistent with a simple device model consisting of gate depletion and interelectrode parasitic capacitances. It is concluded from the analysis that the dual channel system resides in three basic states: (1) Both channels are occupied by 2DEGs or (2) The upper channel is depleted, or (3) Both channels depleted. Finally, increase in isolation between the two 2DEGs is dramatically demonstrated at 77K by the drain current vs. drain voltage, and transconductance vs. gate voltage characteristics.

Circuital characterisation of space-charge motion with a time-varying applied bias

PubMed Central

Kim, Chul; Moon, Eun-Yi; Hwang, Jungho; Hong, Hiki

2015-01-01

Understanding the behaviour of space-charge between two electrodes is important for a number of applications. The Shockley-Ramo theorem and equivalent circuit models are useful for this; however, fundamental questions of the microscopic nature of the space-charge remain, including the meaning of capacitance and its evolution into a bulk property. Here we show that the microscopic details of the space-charge in terms of resistance and capacitance evolve in a parallel topology to give the macroscopic behaviour via a charge-based circuit or electric-field-based circuit. We describe two approaches to this problem, both of which are based on energy conservation: the energy-to-current transformation rule, and an energy-equivalence-based definition of capacitance. We identify a significant capacitive current due to the rate of change of the capacitance. Further analysis shows that Shockley-Ramo theorem does not apply with a time-varying applied bias, and an additional electric-field-based current is identified to describe the resulting motion of the space-charge. Our results and approach provide a facile platform for a comprehensive understanding of the behaviour of space-charge between electrodes. PMID:26133999

Noise characteristics analysis of short wave infrared InGaAs focal plane arrays

NASA Astrophysics Data System (ADS)

Yu, Chunlei; Li, Xue; Yang, Bo; Huang, Songlei; Shao, Xiumei; Zhang, Yaguang; Gong, Haimei

2017-09-01

The increasing application of InGaAs short wave infrared (SWIR) focal plane arrays (FPAs) in low light level imaging requires ultra-low noise FPAs. This paper presents the theoretical analysis of FPA noise, and point out that both dark current and detector capacitance strongly affect the FPA noise. The impact of dark current and detector capacitance on FPA noise is compared in different situations. In order to obtain low noise performance FPAs, the demand for reducing detector capacitance is higher especially when pixel pitch is smaller, integration time is shorter, and integration capacitance is larger. Several InGaAs FPAs were measured and analyzed, the experiments' results could be well fitted to the calculated results. The study found that the major contributor of FPA noise is coupled noise with shorter integration time. The influence of detector capacitance on FPA noise is more significant than that of dark current. To investigate the effect of detector performance on FPA noise, two kinds of photodiodes with different concentration of the absorption layer were fabricated. The detectors' performance and noise characteristics were measured and analyzed, the results are consistent with that of theoretical analysis.

Distribution of leakage currents in the cylindrical and conical sections of the magnetically insulated transmission line of the Angara-5-1 facility in experiments with wire arrays

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

Grabovski, E. V.; Gribov, A. N.; Samokhin, A. A.

2016-08-15

Current leakages in the magnetically insulated transmission lines (MITL) impose restrictions on the transmission of electromagnetic pulses to the load in high-power electrophysical facilities. The multimodule Angara-5-1 facility with an output electric power of up to 6 TW is considered. In this work, the experimental and calculated profiles of leakage currents in two sections of the line are compared when the eight-module facility is loaded by a wire array. The azimuthal distribution of the current in the cylindrical section of the MITL is also considered.

Current transport mechanisms in mercury cadmium telluride diode

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

Gopal, Vishnu, E-mail: vishnu-46@yahoo.com, E-mail: wdhu@mail.sitp.ac.cn; Li, Qing; He, Jiale

This paper reports the results of modelling of the current-voltage characteristics (I-V) of a planar mid-wave Mercury Cadmium Telluride photodiode in a gate controlled diode experiment. It is reported that the diode exhibits nearly ideal I-V characteristics under the optimum surface potential leading to the minimal surface leakage current. Deviations from the optimum surface potential lead to non ideal I–V characteristics, indicating a strong relationship between the ideality factor of the diode with its surface leakage current. Diode's I–V characteristics have been modelled over a range of gate voltages from −9 V to −2 V. This range of gate voltages includes accumulation,more » flat band, and depletion and inversion conditions below the gate structure of the diode. It is shown that the I–V characteristics of the diode can be very well described by (i) thermal diffusion current, (ii) ohmic shunt current, (iii) photo-current due to background illumination, and (iv) excess current that grows by the process of avalanche multiplication in the gate voltage range from −3 V to −5 V that corresponds to the optimum surface potential. Outside the optimum gate voltage range, the origin of the excess current of the diode is associated with its high surface leakage currents. It is reported that the ohmic shunt current model applies to small surface leakage currents. The higher surface leakage currents exhibit a nonlinear shunt behaviour. It is also shown that the observed zero-bias dynamic resistance of the diode over the entire gate voltage range is the sum of ohmic shunt resistance and estimated zero-bias dynamic resistance of the diode from its thermal saturation current.« less

Stray electrical currents in laparoscopic instruments used in da Vinci® robot-assisted surgery: an in vitro study.

PubMed

Mendez-Probst, Carlos E; Vilos, George; Fuller, Andrew; Fernandez, Alfonso; Borg, Paul; Galloway, David; Pautler, Stephen E

2011-09-01

The da Vinci(®) surgical system requires the use of electrosurgical instruments. The re-use of such instruments creates the potential for stray electrical currents from capacitive coupling and/or insulation failure. We used objective measures to report the prevalence and magnitude of such stray currents. Thirty-seven robotic instruments were tested using an electrosurgical unit (ESU) at pure coagulation and cut waveforms at four different settings. Conductive gel-coated instruments were tested at 40W, 80W, and maximum ESU output (coagulation 120W, cut 300W). The magnitude of stray currents was measured by an electrosurgical analyzer. At coagulation waveform in open air, 86% of instruments leaked a mean of 0.4W. In the presence of gel-coated instruments, stray currents were detected in all instruments with means (and standard deviation) of 3.4W (± 2), 4.1W (± 2.3), and 4.1W (± 2.3) at 40W, 80W, and 120W, respectively. At cut waveform in open air, none of the instruments leaked current, while gel-coated instruments leaked a mean of 2.2W (± 1.3), 2.2W (± 1.9) and 3.2W (± 1.9) at 40W, 80W, and 300W, respectively. All tested instruments in our study demonstrated energy leakage. Stray currents were higher during coagulation (high voltage) waveforms, and the magnitude was not always proportionate to the ESU settings. Stray currents have the potential to cause electrical burns. We support the programmed end of life of da Vinci instruments on the basis of safety. Consideration should be given to alternate energy sources or the adoption of active electrode monitoring technology to all monopolar instruments.

Effect of surface fields on the dynamic resistance of planar HgCdTe mid-wavelength infrared photodiodes

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

He, Kai; Wang, Xi; Zhang, Peng

2015-05-28

This work investigates the effect of surface fields on the dynamic resistance of a planar HgCdTe mid-wavelength infrared photodiode from both theoretical and experimental aspects, considering a gated n-on-p diode with the surface potential of its p-region modulated. Theoretical models of the surface leakage current are developed, where the surface tunnelling current in the case of accumulation is expressed by modifying the formulation of bulk tunnelling currents, and the surface channel current for strong inversion is simulated with a transmission line method. Experimental data from the fabricated devices show a flat-band voltage of V{sub FB}=−5.7 V by capacitance-voltage measurement, and thenmore » the physical parameters for bulk properties are determined from the resistance-voltage characteristics of the diode working at a flat-band gate voltage. With proper values of the modeling parameters such as surface trap density and channel electron mobility, the theoretical R{sub 0}A product and corresponding dark current calculated from the proposed model as functions of the gate voltage V{sub g} demonstrate good consistency with the measured values. The R{sub 0}A product remarkably degenerates when V{sub g} is far below or above V{sub FB} because of the surface tunnelling current or channel current, respectively; and it attains the maximum value of 5.7×10{sup 7} Ω · cm{sup 2} around the transition between surface depletion and weak inversion when V{sub g}≈−4 V, which might result from reduced generation-recombination current.« less

Mechanism of leakage of ion-implantation isolated AlGaN/GaN MIS-high electron mobility transistors on Si substrate

NASA Astrophysics Data System (ADS)

Zhang, Zhili; Song, Liang; Li, Weiyi; Fu, Kai; Yu, Guohao; Zhang, Xiaodong; Fan, Yaming; Deng, Xuguang; Li, Shuiming; Sun, Shichuang; Li, Xiajun; Yuan, Jie; Sun, Qian; Dong, Zhihua; Cai, Yong; Zhang, Baoshun

2017-08-01

In this paper, we systematically investigated the leakage mechanism of the ion-implantation isolated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) on Si substrate. By means of combined DC tests at different temperatures and electric field dependence, we demonstrated the following original results: (1) It is proved that gate leakage is the main contribution to OFF-state leakage of ion-implantation isolated AlGaN/GaN MIS-HEMTs, and the gate leakage path is a series connection of the gate dielectric Si3N4 and Si3N4-GaN interface. (2) The dominant mechanisms of the leakage current through LPCVD-Si3N4 gate dielectric and Si3N4-GaN interface are identified to be Frenkel-Poole emission and two-dimensional variable range hopping (2D-VRH), respectively. (3) A certain temperature annealing could reduce the density of the interface state that produced by ion implantation, and consequently suppress the interface leakage transport, which results in a decrease in OFF-state leakage current of ion-implantation isolated AlGaN/GaN MIS-HEMTs.

Significant long-term reduction in n-channel MESFET subthreshold leakage using ammonium-sulfide surface treated gates

NASA Technical Reports Server (NTRS)

Neudeck, P. G.; Carpenter, M. S.; Melloch, Michael R.; Cooper, James A., Jr.

1991-01-01

Ammonium-sulfide (NH4)2S treated gates have been employed in the fabrication of GaAs MESFETs that exhibit a remarkable reduction in subthreshold leakage current. A greater than 100-fold reduction in drain current minimum is observed due to a decrease in Schottky gate leakage. The electrical characteristics have remained stable for over a year during undesiccated storage at room temperature, despite the absence of passivation layers.

Temperature-dependent leakage current behavior of epitaxial Bi0.5Na0.5TiO3-based thin films made by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Hejazi, M. M.; Safari, A.

2011-11-01

This paper discusses the electrical conduction mechanisms in a 0.88 Bi0.5Na0.5TiO3-0.08 Bi0.5K0.5TiO3-0.04 BaTiO3 thin film in the temperature range of 200-350 K. The film was deposited on a SrRuO3/SrTiO3 substrate by pulsed laser deposition technique. At all measurement temperatures, the leakage current behavior of the film matched well with the Lampert's triangle bounded by three straight lines of different slopes. The relative location of the triangle sides varied with temperature due to its effect on the density of charge carriers and un-filled traps. At low electric fields, the ohmic conduction governed the leakage mechanism. The calculated activation energy of the trap is 0.19 eV implying the presence of shallow traps in the film. With increasing the applied field, an abrupt increase in the leakage current was observed. This was attributed to a trap-filling process by the injected carriers. At sufficiently high electric fields, the leakage current obeyed the Child's trap-free square law suggesting the space charge limited current was the dominant mechanism.

Quantifying canal leakage rates using a mass-balance approach and heat-based hydraulic conductivity estimates in selected irrigation canals, western Nebraska, 2007 through 2009

USGS Publications Warehouse

Hobza, Christopher M.; Andersen, Michael J.

2010-01-01

The water supply in areas of the North Platte River Basin in the Nebraska Panhandle has been designated as fully appropriated or overappropriated by the Nebraska Department of Natural Resources (NDNR). Enacted legislation (Legislative Bill 962) requires the North Platte Natural Resources District (NPNRD) and the NDNR to develop an Integrated Management Plan (IMP) to balance groundwater and surface-water supply and demand in the NPNRD. A clear understanding of the groundwater and surface-water systems is critical for the development of a successful IMP. The primary source of groundwater recharge in parts of the NPNRD is from irrigation canal leakage. Because canal leakage constitutes a large part of the hydrologic budget, spatially distributing canal leakage to the groundwater system is important to any management strategy. Surface geophysical data collected along selected reaches of irrigation canals has allowed for the spatial distribution of leakage on a relative basis; however, the actual magnitude of leakage remains poorly defined. To address this need, the U.S. Geological Survey, in cooperation with the NPNRD, established streamflow-gaging stations at upstream and downstream ends from two selected canal reaches to allow a mass-balance approach to be used to calculate daily leakage rates. Water-level and sediment temperature data were collected and simulated at three temperature monitoring sites to allow the use of heat as a tracer to estimate the hydraulic conductivity of canal bed sediment. Canal-leakage rates were estimated by applying Darcy's Law to modeled vertical hydraulic conductivity and either the estimated or measured hydraulic gradient. This approach will improve the understanding of the spatial and temporal variability of canal leakage in varying geologic settings identified in capacitively coupled resistivity surveys. The high-leakage potential study reach of the Tri-State Canal had two streamflow-gaging stations and two temperature monitoring sites along its length. Calculated leakage rates from the mass-balance approach varied from year to year and were generally dependent on local climatic conditions, and the timing and magnitude of the initial seasonal diversion into the Tri-State Canal. Leakage rates ranged from 0.98 meter per day (m/d) on June 22, 2007, to about to 0 m/d during July 2009. Drier conditions generally resulted in higher leakage rates because of reduced flow from Spottedtail Creek, lower groundwater levels near Spottedtail Creek, and no unmeasured flow entering the reach. Of the three years studied (2007-09), 2007 was the driest, and therefore had the highest canal leakage rates. The moderately low leakage potential study reach of Interstate Canal had two streamflow-gaging stations and one temperature monitoring site along its length. Excluding the leakage calculations from early May 2007, leakage rates ranged from 0.08 to 0.7 m/d. Less variability in leakage from year to year indicates that climatic conditions may have less of an effect for Interstate Canal compared to Tri-State Canal. This may be because Interstate Canal was cut into the northern edge of the North Platte alluvial valley and consequently the canal bed is well above the local groundwater table resulting in a constant (1 meter per meter [m/m]) hydraulic gradient. Interstate Canal also does not receive any captured flow that can vary substantially year to year. Two temperature monitoring sites were installed within the high-leakage potential reach of Tri-State Canal. Site TCTEMP1 was established in 2007 where the water table was well below the canal bed surface. The vertical hydraulic conductivity of the poorly sorted sand and gravel beneath site TCTEMP1 was estimated using a calibrated one-dimensional VS2DH model. Using a trial-and-error approach, the best-fit vertical hydraulic conductivity for the site TCTEMP1 model domain was 1.1 m/d. Site TCTEMP2 was established at the mouth of Spottedtail Creek where a shallow

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.

Study on effective MOSFET channel length extracted from gate capacitance

NASA Astrophysics Data System (ADS)

Tsuji, Katsuhiro; Terada, Kazuo; Fujisaka, Hisato

2018-01-01

The effective channel length (L GCM) of metal-oxide-semiconductor field-effect transistors (MOSFETs) is extracted from the gate capacitances of actual-size MOSFETs, which are measured by charge-injection-induced-error-free charge-based capacitance measurement (CIEF CBCM). To accurately evaluate the capacitances between the gate and the channel of test MOSFETs, the parasitic capacitances are removed by using test MOSFETs having various channel sizes and a source/drain reference device. A strong linear relationship between the gate-channel capacitance and the design channel length is obtained, from which L GCM is extracted. It is found that L GCM is slightly less than the effective channel length (L CRM) extracted from the measured MOSFET drain current. The reason for this is discussed, and it is found that the capacitance between the gate electrode and the source and drain regions affects this extraction.

Analysis and modeling of leakage current sensor under pulsating direct current

NASA Astrophysics Data System (ADS)

Li, Kui; Dai, Yihua; Wang, Yao; Niu, Feng; Chen, Zhao; Huang, Shaopo

2017-05-01

In this paper, the transformation characteristics of current sensor under pulsating DC leakage current is investigated. The mathematical model of current sensor is proposed to accurately describe the secondary side current and excitation current. The transformation process of current sensor is illustrated in details and the transformation error is analyzed from multi aspects. A simulation model is built and a sensor prototype is designed to conduct comparative evaluation, and both simulation and experimental results are presented to verify the correctness of theoretical analysis.

Apparatus for detecting leakage of liquid sodium

DOEpatents

Himeno, Yoshiaki

1978-01-01

An apparatus for detecting the leakage of liquid sodium includes a cable-like sensor adapted to be secured to a wall of piping or other equipment having sodium on the opposite side of the wall, and the sensor includes a core wire electrically connected to the wall through a leak current detector and a power source. An accidental leakage of the liquid sodium causes the corrosion of a metallic layer and an insulative layer of the sensor by products resulted from a reaction of sodium with water or oxygen in the atmospheric air so as to decrease the resistance between the core wire and the wall. Thus, the leakage is detected as an increase in the leaking electrical current. The apparatus is especially adapted for use in detecting the leakage of liquid sodium from sodium-conveying pipes or equipment in a fast breeder reactor.

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.

Competition between ionic adsorption and desorption on electrochemical double layer capacitor electrodes in acetonitrile solutions at different currents and temperatures

NASA Astrophysics Data System (ADS)

Park, Sieun; Kang, Seok-Won; Kim, Ketack

2017-12-01

The operation of electrochemical double layer capacitors at high currents and viscosities and at low temperatures is difficult. Under these conditions, ion transport is limited, and some of the electrode area is unavailable for adsorption, which results in a low capacitance. Increasing the temperature helps to increase the ionic movement, leading to enhanced adsorption and increased capacitance. In contrast, ion desorption (self-discharge) surpasses the capacitance improvement when ions gain a high amount of energy with increasing temperature. For example, temperatures as high as 70 °C cause a very high rate of ionic desorption in acetonitrile solutions in which the individual properties of the two electrolytes-tetraethylammonium tetrafluoroborate (TEA BF4) and ethylmethylimidazolium tetrafluoroborate (EMI BF4)-are not distinguishable. The capacitance improvement and self-discharge are balanced, resulting in a capacitance peak at mid-range temperatures, i.e., 35-45 °C, in the more viscous electrolyte, i.e., TEA BF4. The less viscous electrolyte, i.e., EMI BF4 has a wider capacitance peak from 25 to 45 °C and higher capacitance than that of TEA BF4. Because the maximum power is obtained in the mid-temperature range (35-45 °C), it is necessary to control the viscosity and temperature to obtain the maximum power in a given device.

Analysis of Co-Tunneling Current in Fullerene Single-Electron Transistor

NASA Astrophysics Data System (ADS)

KhademHosseini, Vahideh; Dideban, Daryoosh; Ahmadi, MohammadTaghi; Ismail, Razali

2018-05-01

Single-electron transistors (SETs) are nano devices which can be used in low-power electronic systems. They operate based on coulomb blockade effect. This phenomenon controls single-electron tunneling and it switches the current in SET. On the other hand, co-tunneling process increases leakage current, so it reduces main current and reliability of SET. Due to co-tunneling phenomenon, main characteristics of fullerene SET with multiple islands are modelled in this research. Its performance is compared with silicon SET and consequently, research result reports that fullerene SET has lower leakage current and higher reliability than silicon counterpart. Based on the presented model, lower co-tunneling current is achieved by selection of fullerene as SET island material which leads to smaller value of the leakage current. Moreover, island length and the number of islands can affect on co-tunneling and then they tune the current flow in SET.

Comparison of the Standard of Air Leakage in Current Metal Duct Systems in the World

NASA Astrophysics Data System (ADS)

Di, Yuhui; Wang, Jiqian; Feng, Lu; Li, Xingwu; Hu, Chunlin; Shi, Junshe; Xu, Qingsong; Qiao, Leilei

2018-01-01

Based on the requirements of air leakage of metal ducts in Chinese design standards, technical measures and construction standards, this paper compares the development history, the classification of air pressure levels and the air tightness levels of air leakage standards of current Chinese and international metal ducts, sums up the differences, finds shortage by investigating the design and construction status and access to information, and makes recommendations, hoping to help the majority of engineering and technical personnel.

Integration of solid-state nanopores in a 0.5 μm cmos foundry process

PubMed Central

Uddin, A; Yemenicioglu, S; Chen, C-H; Corigliano, E; Milaninia, K; Theogarajan, L

2013-01-01

High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the integration of solid-state nanopore devices in a commercial complementary metal-oxide semiconductor (CMOS) potentiostat chip implemented in On-Semiconductor’s 0.5 μm technology. Nanopore membranes incorporating electrodes are fabricated by post-CMOS micromachining utilizing the N+ polysilicon/SiO2/N+ polysilicon capacitor structure available in the aforementioned process. Nanopores are created in the CMOS process by drilling in a transmission electron microscope and shrinking by atomic layer deposition. We also describe a batch fabrication method to process a large of number of electrode-embedded nanopores with sub-10 nm diameter across CMOS-compatible wafers by electron beam lithography and atomic layer deposition. The CMOS-compatibility of our fabrication process is verified by testing the electrical functionality of on-chip circuitry. We observe high current leakage with the CMOS nanopore devices due to the ionic diffusion through the SiO2 membrane. To prevent this leakage, we coat the membrane with Al2O3 which acts as an efficient diffusion barrier against alkali ions. The resulting nanopore devices also exhibit higher robustness and lower 1/f noise as compared to SiO2 and SiNx. Furthermore, we propose a theoretical model for our low-capacitance CMOS nanopore devices, showing good agreement with the experimental value. In addition, experiments and theoretical models of translocation studies are presented using 48.5 kbp λ-DNA in order to prove the functionality of on-chip pores coated with Al2O3. PMID:23519330

Hydrophobicity and leakage current statistics of polymeric insulators long-term exposed to coastal contamination

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

Soerqvist, T.; Vlastos, A.E.

1996-12-31

The hydrophobicity of polymeric insulators is crucial for their performance. This paper reports the hydrophobicity and the peak leakage current statistics of one porcelain, two ethylene-propylene-diene monomer (EPDM) and four silicone rubber (SIR) commercially available insulators. The insulators have been energized with 130 kV rms phase-to-ground AC voltage under identical outdoor conditions for more than seven years. The results presented show that under wet and polluted conditions the hydrophilic EPDM rubber insulators develop high leakage currents and substantial arcing. During a typical salt-storm the arcing amplitude of the EPDM rubber insulators is at least twice as high as that ofmore » the porcelain insulator. The SIR insulators, on the other hand, preserve a high degree of hydrophobicity after more than seven years in service and maintain very low leakage currents. However, the results show that during heavy salt contaminated conditions a highly stressed SIR insulator can temporarily lose its hydrophobicity and thereby develop considerable surface arcing.« less

Effect of Compressive Stresses on Leakage Currents in Microchip Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2012-01-01

Microchip tantalum capacitors are manufactured using new technologies that allow for production of small size capacitors (down to EIA case size 0402) with volumetric efficiency much greater than for regular chip capacitors. Due to a small size of the parts and leadless design they might be more sensitive to mechanical stresses that develop after soldering onto printed wiring boards (PWB) compared to standard chip capacitors. In this work, the effect of compressive stresses on leakage currents in capacitors has been investigated in the range of stresses up to 200 MPa. Significant, up to three orders of magnitude, variations of currents were observed after the stress exceeds a certain critical level that varied from 10 MPa to 180 MPa for capacitors used in this study. A stress-induced generation of electron traps in tantalum pentoxide dielectric is suggested to explain reversible variations of leakage currents in tantalum capacitors. Thermo-mechanical characteristics of microchip capacitors have been studied to estimate the level of stresses caused by assembly onto PWB and assess the risk of stress-related degradation and failures. Keywords: tantalum capacitors, leakage current, soldering, reliability, mechanical stress.

21 CFR 870.2640 - Portable leakage current alarm.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Portable leakage current alarm. 870.2640 Section 870.2640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2640 Portable...

21 CFR 870.2640 - Portable leakage current alarm.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Portable leakage current alarm. 870.2640 Section 870.2640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2640 Portable...

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).

Impact of underlap spacer region variation on electrostatic and analog performance of symmetrical high-k SOI FinFET at 20 nm channel length

NASA Astrophysics Data System (ADS)

Jain, Neeraj; Raj, Balwinder

2017-12-01

Continued scaling of CMOS technology to achieve high performance and low power consumption of semiconductor devices in the complex integrated circuits faces the degradation in terms of electrostatic integrity, short channel effects (SCEs), leakage currents, device variability and reliability etc. Nowadays, multigate structure has become the promising candidate to overcome these problems. SOI FinFET is one of the best multigate structures that has gained importance in all electronic design automation (EDA) industries due to its improved short channel effects (SCEs), because of its more effective gate-controlling capabilities. In this paper, our aim is to explore the sensitivity of underlap spacer region variation on the performance of SOI FinFET at 20 nm channel length. Electric field modulation is analyzed with spacer length variation and electrostatic performance is evaluated in terms of performance parameter like electron mobility, electric field, electric potential, sub-threshold slope (SS), ON current (I on), OFF current (I off) and I on/I off ratio. The potential benefits of SOI FinFET at drain-to-source voltage, V DS = 0.05 V and V DS = 0.7 V towards analog and RF design is also evaluated in terms of intrinsic gain (A V), output conductance (g d), trans-conductance (g m), gate capacitance (C gg), and cut-off frequency (f T = g m/2πC gg) with spacer region variations.

Printed Circuit Board Surface Finish and Effects of Chloride Contamination, Electric Field, and Humidity on Corrosion Reliability

NASA Astrophysics Data System (ADS)

Conseil-Gudla, Hélène; Jellesen, Morten S.; Ambat, Rajan

2017-02-01

Corrosion reliability is a serious issue today for electronic devices, components, and printed circuit boards (PCBs) due to factors such as miniaturization, globalized manufacturing practices which can lead to process-related residues, and global usage effects such as bias voltage and unpredictable user environments. The investigation reported in this paper focuses on understanding the synergistic effect of such parameters, namely contamination, humidity, PCB surface finish, pitch distance, and potential bias on leakage current under different humidity levels, and electrochemical migration probability under condensing conditions. Leakage currents were measured on interdigitated comb test patterns with three different types of surface finish typically used in the electronics industry, namely gold, copper, and tin. Susceptibility to electrochemical migration was studied under droplet conditions. The level of base leakage current (BLC) was similar for the different surface finishes and NaCl contamination levels up to relative humidity (RH) of 65%. A significant increase in leakage current was found for comb patterns contaminated with NaCl above 70% to 75% RH, close to the deliquescent RH of NaCl. Droplet tests on Cu comb patterns with varying pitch size showed that the initial BLC before dendrite formation increased with increasing NaCl contamination level, whereas electrochemical migration and the frequency of dendrite formation increased with bias voltage. The effect of different surface finishes on leakage current under humid conditions was not very prominent.

The Random Telegraph Signal Behavior of Intermittently Stuck Bits in SDRAMs

NASA Astrophysics Data System (ADS)

Chugg, Andrew Michael; Burnell, Andrew J.; Duncan, Peter H.; Parker, Sarah; Ward, Jonathan J.

2009-12-01

This paper reports behavior analogous to the Random Telegraph Signal (RTS) seen in the leakage currents from radiation induced hot pixels in Charge Coupled Devices (CCDs), but in the context of stuck bits in Synchronous Dynamic Random Access Memories (SDRAMs). Our analysis suggests that pseudo-random sticking and unsticking of the SDRAM bits is due to thermally induced fluctuations in leakage current through displacement damage complexes in depletion regions that were created by high-energy neutron and proton interactions. It is shown that the number of observed stuck bits increases exponentially with temperature, due to the general increase in the leakage currents through the damage centers with temperature. Nevertheless, some stuck bits are seen to pseudo-randomly stick and unstick in the context of a continuously rising trend of temperature, thus demonstrating that their damage centers can exist in multiple widely spaced, discrete levels of leakage current, which is highly consistent with RTS. This implies that these intermittently stuck bits (ISBs) are a displacement damage phenomenon and are unrelated to microdose issues, which is confirmed by the observation that they also occur in unbiased irradiation. Finally, we note that observed variations in the periodicity of the sticking and unsticking behavior on several timescales is most readily explained by multiple leakage current pathways through displacement damage complexes spontaneously and independently opening and closing under the influence of thermal vibrations.

Universality of Non-Ohmic Shunt Leakage in Thin-Film Solar Cells

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

Dongaonkar, S.; Servaites, J.D.; Ford, G.M.

2010-01-01

We compare the dark current-voltage (IV) characteristics of three different thin-film solar cell types: hydrogenated amorphous silicon (a-Si:H) p-i-n cells, organic bulk heterojunction (BHJ) cells, and Cu(In,Ga)Se 2 (CIGS) cells. All three device types exhibit a significant shunt leakage current at low forward bias (V<~0.4) and reverse bias, which cannot be explained by the classical solar cell diode model. This parasitic shunt current exhibits non-Ohmic behavior, as opposed to the traditional constant shunt resistance model for photovoltaics. We show here that this shunt leakage (I sh) , across all three solar cell types considered, is characterized by the following commonmore » phenomenological features: (a) voltage symmetry about V=0 , (b) nonlinear (power law) voltage dependence, and (c) extremely weak temperature dependence. Based on this analysis, we provide a simple method of subtracting this shunt current component from the measured data and discuss its implications on dark IV parameter extraction. We propose a space charge limited (SCL) current model for capturing all these features of the shunt leakage in a consistent framework and discuss possible physical origin of the parasitic paths responsible for this shunt current mechanism.« less

Nano-aggregates of cobalt nickel oxysulfide as a high-performance electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Lifeng

2013-11-01

Nano-aggregates of cobalt nickel oxysulfide (CoNi)OxSy have been synthesized by hydrothermal processing and exhibited specific and areal capacitance as high as 592 F g-1 and 1628 mF cm-2, respectively, at a current density of 0.5 A g-1/1.375 mA cm-2. They also show high capacitance retention upon extended cycling at high rates.Nano-aggregates of cobalt nickel oxysulfide (CoNi)OxSy have been synthesized by hydrothermal processing and exhibited specific and areal capacitance as high as 592 F g-1 and 1628 mF cm-2, respectively, at a current density of 0.5 A g-1/1.375 mA cm-2. They also show high capacitance retention upon extended cycling at high rates. Electronic supplementary information (ESI) available: Experimental details; supplementary tables. See DOI: 10.1039/c3nr03533f

In situ fabrication of nickel aluminum-layered double hydroxide nanosheets/hollow carbon nanofibers composite as a novel electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

He, Fang; Hu, Zhibiao; Liu, Kaiyu; Zhang, Shuirong; Liu, Hongtao; Sang, Shangbin

2014-12-01

This paper introduces a new design route to fabricate nickel aluminum-layered double hydroxide (NiAl-LDH) nanosheets/hollow carbon nanofibers (CNFs) composite through an in situ growth method. The NiAl-LDH thin layers which grow on hollow carbon nanofibers have an average thickness of 13.6 nm. The galvanostatic charge-discharge test of the NiAl-LDH/CNFs composite yields an impressive specific capacitance of 1613 F g-1 at 1 A g-1 in 6 M KOH solution, the composite shows a remarkable specific capacitance of 1110 F g-1 even at a high current density of 10 A g-1. Furthermore, the composite remains a specific capacitance of 1406 F g-1 after 1000 cycles at 2 A g-1, indicating the composite has excellent high-current capacitive behavior and good cycle stability in compared to pristine NiAl-LDH.

Preparation of Shape-Controlled Graphene/Co3O4 Composites for Supercapacitors

NASA Astrophysics Data System (ADS)

Chen, Jun; Chen, Ningna; Feng, Xiaomiao; Hou, Wenhua

2016-09-01

Graphene/Co3O4 nanocomposites with different morphologies were fabricated by hydrothermal method. The morphology of nanocomposites was characterized by scanning electron microscopy. These composites could be used as the electrode materials for supercapacitors. The eletrochemical behavior of the composite was tested by cyclic voltammetry and galvanostatic charge-discharge measurements in 1.0 mol/L KOH solution. The results showed that the graphene/Co3O4 nanopetal composite exhibited excellent electrochemical performance. The specific capacitance value could reach up to 714 F/g at a scan rate of 2 mV/s. Besides, the capacitance of the graphene/Co3O4 nanopetal composite was 841 F/g at a current density of 0.1 A/g. After galvanostatic charge-discharge 1000 laps at the current density of 0.4 A/g, the specific capacitance could keep 96.7% of original capacitive value, demonstrating its good cycling stability.

MnO2 nanowires-decorated carbon fiber cloth as electrodes for aqueous asymmetric supercapacitor

NASA Astrophysics Data System (ADS)

Hong, Congcong; Wang, Xing; Yu, Houlin; Wu, Huaping; Wang, Jianshan; Liu, Aiping

Manganese dioxide nanowires (MnO2 NWs) anchored on carbon fiber cloth (CFC) were fabricated through a simple hydrothermal reaction and used as integrated electrodes for supercapacitor. The morphology-dependent electrochemical performance of MnO2 NWs was confirmed, yielding good capacitance performance with a high specific capacitance of 3.88Fṡcm‑2 at a charge-discharge current density of 5mAṡcm‑2 and excellent stability of 91.5% capacitance retention after 3000 cycles. Moreover, the composite electrodes were used to fabricate supercapacitors, which showed a high specific capacitance of 194mFṡcm‑2 at a charge-discharge current density of 2mAṡcm‑2 and high energy density of 0.108mWhṡcm‑2 at power density of 2mWṡcm‑2, foreboding its potential application for high-performance supercapacitor.

Safety devices for neonatal intensive care.

PubMed

Neuman, M R; Flammer, C M; O'Connor, E

1982-01-01

Three relatively simple devices for improving safety in neonatal intensive care are described. When umbilical artery catheters are used, an inexpensive pressure switch is utilized to detect abnormally low pressures associated with catheter withdrawal or excessive fluid leakage from the catheter system. A capacitive, intravenous-line air bubble detector, consisting of a section of the intravenous line as the dielectric of a capacitor, is used to alert the clinical staff when air bubbles pass between the capacitor plates. An electronic temperature controller maintains the temperature of neonatal breathing gases to avoid temperature variations which occur with presently used techniques. These are relatively simple and inexpensive devices which can be fabricated by most hospital clinical engineering services.

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.

Involvement of a Na+/HCO-3 cotransporter in mouse sperm capacitation.

PubMed

Demarco, Ignacio A; Espinosa, Felipe; Edwards, Jennifer; Sosnik, Julian; De La Vega-Beltran, Jose Luis; Hockensmith, Joel W; Kopf, Gregory S; Darszon, Alberto; Visconti, Pablo E

2003-02-28

Mammalian sperm are incapable of fertilizing eggs immediately after ejaculation; they acquire fertilization capacity after residing in the female tract for a finite period of time. The physiological changes sperm undergo in the female reproductive tract that render sperm able to fertilize constitute the phenomenon of "sperm capacitation." We have demonstrated that capacitation is associated with an increase in the tyrosine phosphorylation of a subset of proteins and that these events are regulated by an HCO(3)(-)/cAMP-dependent pathway involving protein kinase A. Capacitation is also accompanied by hyperpolarization of the sperm plasma membrane. Here we present evidence that, in addition to its role in the regulation of adenylyl cyclase, HCO(3)(-) has a role in the regulation of plasma membrane potential in mouse sperm. Addition of HCO(3)(-) but not Cl(-) induces a hyperpolarizing current in mouse sperm plasma membranes. This HCO(3)(-)-dependent hyperpolarization was not observed when Na(+) was replaced by the non-permeant cation choline(+). Replacement of Na(+) by choline(+) also inhibited the capacitation-associated increase in protein tyrosine phosphorylation as well as the zona pellucida-induced acrosome reaction. The lack of an increase in protein tyrosine phosphorylation was overcome by the presence of cAMP agonists in the incubation medium. The lack of a hyperpolarizing HCO(3)(-) current and the inhibition of the capacitation-dependent increase in protein tyrosine phosphorylation in the absence of Na(+) suggest that a Na(+)/HCO(3)(-) cotransporter is present in mouse sperm and is coupled to events regulating capacitation.

Module Hipot and ground continuity test results

NASA Technical Reports Server (NTRS)

Griffith, J. S.

1984-01-01

Hipot (high voltage potential) and module frame continuity tests of solar energy conversion modules intended for deployment into large arrays are discussed. The purpose of the tests is to reveal potentially hazardous voltage conditions in installed modules, and leakage currents that may result in loss of power or cause ground fault system problems, i.e., current leakage potential and leakage voltage distribution. The tests show a combined failure rate of 36% (69% when environmental testing is included). These failure rates are believed easily corrected by greater care in fabrication.

a High-Level Technique for Estimation and Optimization of Leakage Power for Full Adder

NASA Astrophysics Data System (ADS)

Shrivas, Jayram; Akashe, Shyam; Tiwari, Nitesh

2013-06-01

Optimization of power is a very important issue in low-voltage and low-power application. In this paper, we have proposed power gating technique to reduce leakage current and leakage power of one-bit full adder. In this power gating technique, we use two sleep transistors i.e., PMOS and NMOS. PMOS sleep transistor is inserted between power supply and pull up network. And NMOS sleep transistor is inserted between pull down network and ground terminal. These sleep transistors (PMOS and NMOS) are turned on when the circuit is working in active mode. And sleep transistors (PMOS and NMOS) are turned off when circuit is working in standby mode. We have simulated one-bit full adder and compared with the power gating technique using cadence virtuoso tool in 45 nm technology at 0.7 V at 27°C. By applying this technique, we have reduced leakage current from 2.935 pA to 1.905 pA and leakage power from 25.04μw to 9.233μw. By using this technique, we have reduced leakage power up to 63.12%.

Preparation of magnetron sputtered ZrO2 films on Si for gate dielectric application

NASA Astrophysics Data System (ADS)

Kondaiah, P.; Mohan Rao, G.; Uthanna, S.

2012-11-01

Zirconium oxide (ZrO2) thin films were deposited on to p - Si and quartz substrates by sputtering of zirconium target at an oxygen partial pressure of 4x10-2 Pa and sputter pressure of 0.4 Pa by using DC reactive magnetron sputtering technique. The effect of annealing temperature on structural, optical, electrical and dielectric properties of the ZrO2 films was systematically studied. The as-deposited films were mixed phases of monoclinic and orthorhombic ZrO2. As the annealing temperature increased to 1073 K, the films were transformed in to single phase orthorhombic ZrO2. Fourier transform infrared studies conform the presence of interfacial layer between Si and ZrO2. The optical band gap and refractive index of the as-deposited films were 5.82 eV and 1.81. As the annealing temperature increased to 1073 K the optical band gap and refractive index increased to 5.92 eV and 2.10 respectively. The structural changes were influenced the capacitance-voltage and current-voltage characteristics of Al/ZrO2/p-Si capacitors. The dielectric constant was increased from 11.6 to 24.5 and the leakage current was decreased from 1.65×10-7 to 3.30×10-9 A/ cm2 for the as-deposited and annealed at 1073 K respectively.

Printed indium gallium zinc oxide transistors. Self-assembled nanodielectric effects on low-temperature combustion growth and carrier mobility.

PubMed

Everaerts, Ken; Zeng, Li; Hennek, Jonathan W; Camacho, Diana I; Jariwala, Deep; Bedzyk, Michael J; Hersam, Mark C; Marks, Tobin J

2013-11-27

Solution-processed amorphous oxide semiconductors (AOSs) are emerging as important electronic materials for displays and transparent electronics. We report here on the fabrication, microstructure, and performance characteristics of inkjet-printed, low-temperature combustion-processed, amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) grown on solution-processed hafnia self-assembled nanodielectrics (Hf-SANDs). TFT performance for devices processed below 300 °C includes >4× enhancement in electron mobility (μFE) on Hf-SAND versus SiO2 or ALD-HfO2 gate dielectrics, while other metrics such as subthreshold swing (SS), current on:off ratio (ION:IOFF), threshold voltage (Vth), and gate leakage current (Ig) are unchanged or enhanced. Thus, low voltage IGZO/SAND TFT operation (<2 V) is possible with ION:IOFF = 10(7), SS = 125 mV/dec, near-zero Vth, and large electron mobility, μFE(avg) = 20.6 ± 4.3 cm(2) V(-1) s(-1), μFE(max) = 50 cm(2) V(-1) s(-1). Furthermore, X-ray diffraction analysis indicates that the 300 °C IGZO combustion processing leaves the underlying Hf-SAND microstructure and capacitance intact. This work establishes the compatibility and advantages of all-solution, low-temperature fabrication of inkjet-printed, combustion-derived high-mobility IGZO TFTs integrated with self-assembled hybrid organic-inorganic nanodielectrics.

Thin Films

NASA Astrophysics Data System (ADS)

Khorshidi, Zahra; Bahari, Ali; Gholipur, Reza

2014-11-01

Effect of annealing temperature on the characteristics of sol-gel-driven Ta ax La(1- a) x O y thin film spin-coated on Si substrate as a high- k gate dielectric was studied. Ta ax La(1- a) x O y thin films with different amounts of a were prepared (as-prepared samples). X-ray diffraction measurements of the as-prepared samples indicated that Ta0.3 x La0.7 x Oy film had an amorphous structure. Therefore, Ta0.3 x La0.7 x O y film was chosen to continue the present studies. The morphology of Ta0.3 x La0.7 x O y films was studied using scanning electron microscopy and atomic force microscopy techniques. The obtained results showed that the size of grain boundaries on Ta0.3 x La0.7 x O y film surfaces was increased with increasing annealing temperature. Electrical and optical characterizations of the as-prepared and annealed films were investigated as a function of annealing temperature using capacitance-voltage ( C- V) and current density-voltage ( J- V) measurements and the Tauc method. The obtained results demonstrated that Ta0.3 x La0.7 x O y films had high dielectric constant (≈27), wide band gap (≈4.5 eV), and low leakage current density (≈10-6 A/cm2 at 1 V).

High power density dc-to-dc converters for aerospace applications

NASA Technical Reports Server (NTRS)

Divan, Deepakraj M.

1990-01-01

Three dc-to-dc converter topologies aimed at high-power high-frequency applications are introduced. Major system parasitics, namely, the leakage inductance of the transformer and the device output capacitance are efficiently utilized. Of the three circuits, the single-phase and three-phase versions of the dual active bridge topology demonstrate minimal stresses, better utilization of the transformer, bidirectional, and buck-boost modes of operation. All circuits operate at a constant switching frequency, thus simplifying design of the reactive elements. The power transfer characteristics and soft-switching regions on the Vout-Iout plane are identified. Two coaxial transformers with different cross-sections were built for a rating of 50 kVA. Based on the single-phase dual active bridge topology, a 50 kW, 50 kHz converter operating at an input voltage of 200 Vdc and an output voltage of 1600 Vdc was fabricated. Characteristics of current-fed output make the dual active bridge topologies amenable to paralleling and hence extension to megawatt power levels. Projections to a 1 MW system operating from a 500 Vdc input, at an output voltage of 10 kVdc and a switching frequency of 50 kHz, using MOS-controlled thyristors, coaxially wound transformers operating at three times the present current density with cooling, and multilayer ceramic capacitors, suggests an overall power density of 0.075 to 0.08 kg/kW and an overall efficiency of 96 percent.

Ultralow-power organic complementary circuits.

PubMed

Klauk, Hagen; Zschieschang, Ute; Pflaum, Jens; Halik, Marcus

2007-02-15

The prospect of using low-temperature processable organic semiconductors to implement transistors, circuits, displays and sensors on arbitrary substrates, such as glass or plastics, offers enormous potential for a wide range of electronic products. Of particular interest are portable devices that can be powered by small batteries or by near-field radio-frequency coupling. The main problem with existing approaches is the large power consumption of conventional organic circuits, which makes battery-powered applications problematic, if not impossible. Here we demonstrate an organic circuit with very low power consumption that uses a self-assembled monolayer gate dielectric and two different air-stable molecular semiconductors (pentacene and hexadecafluorocopperphthalocyanine, F16CuPc). The monolayer dielectric is grown on patterned metal gates at room temperature and is optimized to provide a large gate capacitance and low gate leakage currents. By combining low-voltage p-channel and n-channel organic thin-film transistors in a complementary circuit design, the static currents are reduced to below 100 pA per logic gate. We have fabricated complementary inverters, NAND gates, and ring oscillators that operate with supply voltages between 1.5 and 3 V and have a static power consumption of less than 1 nW per logic gate. These organic circuits are thus well suited for battery-powered systems such as portable display devices and large-surface sensor networks as well as for radio-frequency identification tags with extended operating range.

Electrical Characterization of Semiconductor and Dielectric Materials with a Non-Damaging FastGateTM Probe

NASA Astrophysics Data System (ADS)

Robert, Hillard; William, Howland; Bryan, Snyder

2002-03-01

Determination of the electrical properties of semiconductor materials and dielectrics is highly desirable since these correlate best to final device performance. The properties of SiO2 and high k dielectrics such as Equivalent Oxide Thickness(EOT), Interface Trap Density(Dit), Oxide Effective Charge(Neff), Flatband Voltage Hysteresis(Delta Vfb), Threshold Voltage(VT) and, bulk properties such as carrier density profile and channel dose are all important parameters that require monitoring during front end processing. Conventional methods for determining these parameters involve the manufacturing of polysilicon or metal gate MOS capacitors and subsequent measurements of capacitance-voltage(CV) and/or current-voltage(IV). These conventional techniques are time consuming and can introduce changes to the materials being monitored. Also, equivalent circuit effects resulting from excessive leakage current, series resistance and stray inductance can introduce large errors in the measured results. In this paper, a new method is discussed that provides rapid determination of these critical parameters and is robust against equivalent circuit errors. This technique uses a small diameter(30 micron), elastically deformed probe to form a gate for MOSCAP CV and IV and can be used to measure either monitor wafers or test areas within scribe lines on product wafers. It allows for measurements of dielectrics thinner than 10 Angstroms. A detailed description and applications such as high k dielectrics, will be presented.

Structural evolution of nanoporous ultra-low k dielectrics under voltage stress

NASA Astrophysics Data System (ADS)

Raja, Archana; Shaw, Thomas; Grill, Alfred; Laibowitz, Robert; Heinz, Tony

2013-03-01

High speed interconnects in advanced integrated circuits require ultra-low-k dielectrics. Reduction of the dielectric constant is achieved via incorporation of nanopores in structures containing silicon, carbon, oxygen and hydrogen (SiCOH). We study nanoporous SiCOH films of k=2.5 and thicknesses of 40 - 400 nm. Leakage currents develop in the films under long-term voltage stress, eventually leading to breakdown and chip failure. Previous work* has shown the build-up of trap states as dielectric breakdown progresses. Using FTIR spectroscopy we have tracked the reorganization of the bonds in the SiCOH networks induced by voltage stress. Our results indicate that the cleavage of the Si-C and SiC-O bonds contribute toward increase in the density of bulk trapping states as breakdown is approached. AC conductance and capacitance measurements have also been carried out to describe interfacial and bulk traps and mechanisms. Comparison of breakdown properties of films with differing carbon content will also be presented to further delineate the role of carbon. *Atkin, J.M.; Shaw, T.M.; Liniger, E.; Laibowitz, R.B.; Heinz, T.F. Reliability Physics Symposium (IRPS), 2012 IEEE International Supported by the Semiconductor Research Corporation

Shallow doping effect of ZnO treatment using atomic layer deposition process on p-type In0.53Ga0.47As

NASA Astrophysics Data System (ADS)

Lee, Changmin; An, Youngseo; Choi, Sungho; Kim, Hyoungsub

2018-06-01

The number of atomic layer deposition (ALD) cycles for ZnO treatment was changed to study its merits and demerits as a passivation layer prior to the deposition of a HfO2 film on a p-type In0.53Ga0.47As substrate. Even a few cycles of ZnO ALD treatment was effective in improving the capacitance–voltage (C–V) characteristics by suppressing strong Fermi-level pinning, which occurred because of a high interface state density near the lower half of the In0.53Ga0.47As band gap. Increases in the number of ZnO ALD cycles induced an increase in the minimum capacitance and response of minority carriers at higher frequencies in the inversion region of the C–V characteristics. According to various temperature- and frequency-dependent C–V analyses, these changes were explained by the shallow p-type doping effect of Zn atoms in the In0.53Ga0.47As substrate. As a disadvantage, ZnO ALD treatment caused a slight increase in the dielectric leakage current.

Bottom electrodes dependence of microstructures and dielectric properties of compositionally graded (Ba{sub 1-x}Sr{sub x})TiO{sub 3} thin films

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

Zhang Tianjin; Wang Jinzhao; Zhang Baishun

2008-03-04

Compositionally graded (Ba{sub 1-x}Sr{sub x})TiO{sub 3} (BST) thin films, with x decreasing from 0.3 to 0, were deposited on Pt/Ti/SiO{sub 2}/Si and Ru/SiO{sub 2}/Si substrates by radio frequency magnetron sputtering technology. The microstructure and dielectric properties of the graded BST thin films were investigated. It was found that the films on Ru electrode have better crystallization, and that RuO{sub 2} is present between the Ru bottom electrode and the graded BST thin films by X-ray diffraction and SEM analysis. Dielectric measurement reveals that the graded BST thin films deposited on Ru bottom electrode have higher dielectric constant and tunability. Themore » enhanced dielectric behavior is attributed to better crystallization as well as smaller space charge capacitance width and the formation of RuO{sub 2} that is more compatible with the BST films. The graded BST films on Ru electrode show higher leakage current due to lower barrier height and rougher surface of bottom electrode.« less

Low dose radiation damage effects in silicon strip detectors

NASA Astrophysics Data System (ADS)

Wiącek, P.; Dąbrowski, W.

2016-11-01

The radiation damage effects in silicon segmented detectors caused by X-rays have become recently an important research topic driven mainly by development of new detectors for applications at the European X-ray Free Electron Laser (E-XFEL). However, radiation damage in silicon strip is observed not only after extreme doses up to 1 GGy expected at E-XFEL, but also at doses in the range of tens of Gy, to which the detectors in laboratory instruments like X-ray diffractometers or X-ray spectrometers can be exposed. In this paper we report on investigation of radiation damage effects in a custom developed silicon strip detector used in laboratory diffractometers equipped with X-ray tubes. Our results show that significant degradation of detector performance occurs at low doses, well below 200 Gy, which can be reached during normal operation of laboratory instruments. Degradation of the detector energy resolution can be explained by increasing leakage current and increasing interstrip capacitance of the sensor. Another observed effect caused by accumulation of charge trapped in the surface oxide layer is change of charge division between adjacent strips. In addition, we have observed unexpected anomalies in the annealing process.

Ruthenium films by digital chemical vapor deposition: Selectivity, nanostructure, and work function

NASA Astrophysics Data System (ADS)

Dey, Sandwip K.; Goswami, Jaydeb; Gu, Diefeng; de Waard, Henk; Marcus, Steve; Werkhoven, Chris

2004-03-01

Ruthenium electrodes were selectively deposited on photoresist-patterned HfO2 surface [deposited on a SiOx/Si wafer by atomic layer deposition (ALD)] by a manufacturable, digital chemical vapor deposition (DCVD) technique. DCVD of Ru was carried out at 280-320 °C using an alternate delivery of Bis (2,2,6,6-tetramethyl-3,5-heptanedionato)(1,5-cyclooctadiene)Ru (dissolved in tetrahydrofuran) and oxygen. The as-deposited Ru films were polycrystalline, dense, and conducting (resistivity ˜20.6 μΩ cm). However, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, and high-resolution electron microscopy results indicate the presence of an amorphous RuOx at the Ru grain boundaries and at the DCVD-Ru/ALD-HfO2 interface. The estimated work function of DCVD-Ru on ALD-HfO2 was ˜5.1 eV. Moreover, the equivalent oxide thickness, hysteresis in capacitance-voltage, and leakage current density at -2 V of the HfO2/SiOx dielectric, after forming gas (95% N2+5% H2) annealing at 450 °C for 30 min, were 1.4 nm, 20 mV, and 7.4×10-7 A cm-2, respectively.

Simulation design of high reverse blocking high-K/low-K compound passivation AlGaN/GaN Schottky barrier diode with gated edge termination

NASA Astrophysics Data System (ADS)

Bai, Zhiyuan; Du, Jiangfeng; Xin, Qi; Li, Ruonan; Yu, Qi

2017-11-01

In this paper, a novel high-K/low-K compound passivation AlGaN/GaN Schottky Barrier Diode (CPG-SBD) is proposed to improve the off-state characteristics of AlGaN/GaN schottky barrier diode with gated edge termination (GET-SBD) by adding low-K blocks in to the high-K passivation layer. The reverse leakage current of CPG-SBD can be reduced to 1.6 nA/mm by reducing the thickness of high-K dielectric under GET region to 5 nm, while the forward voltage and on-state resistance keep 1 V and 3.8 Ω mm, respectively. Breakdown voltage of CPG-SBDs can be improved by inducing discontinuity of the electric field at the high-K/low-K interface. The breakdown voltage of the optimized CPG-SBD with 4 blocks of low-K can reach 1084 V with anode to cathode distance of 5 μm yielding a high FOM of 5.9 GW/cm2. From the C-V simulation results, CPG-SBDs induce no parasitic capacitance by comparison of the GET-SBDs.

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation.

PubMed

Chen, Jian Z; Darhuber, Anton A; Troian, Sandra M; Wagner, Sigurd

2004-10-01

The design and performance of a miniaturized coplanar capacitive sensor is presented whose electrode arrays can also function as resistive microheaters for thermocapillary actuation of liquid films and droplets. Optimal compromise between large capacitive signal and high spatial resolution is obtained for electrode widths comparable to the liquid film thickness measured, in agreement with supporting numerical simulations which include mutual capacitance effects. An interdigitated, variable width design, allowing for wider central electrodes, increases the capacitive signal for liquid structures with non-uniform height profiles. The capacitive resolution and time response of the current design is approximately 0.03 pF and 10 ms, respectively, which makes possible a number of sensing functions for nanoliter droplets. These include detection of droplet position, size, composition or percentage water uptake for hygroscopic liquids. Its rapid response time allows measurements of the rate of mass loss in evaporating droplets.

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.

Recovery Characteristics of Anomalous Stress-Induced Leakage Current of 5.6 nm Oxide Films

NASA Astrophysics Data System (ADS)

Inatsuka, Takuya; Kumagai, Yuki; Kuroda, Rihito; Teramoto, Akinobu; Sugawa, Shigetoshi; Ohmi, Tadahiro

2012-04-01

Anomalous stress-induced leakage current (SILC), which has a much larger current density than average SILC, causes severe bit error in flash memories. To suppress anomalous SILC, detailed evaluations are strongly required. We evaluate the characteristics of anomalous SILC of 5.6 nm oxide films using a fabricated array test pattern, and recovery characteristics are observed. Some characteristics of typical anomalous cells in the time domain are measured, and the recovery characteristics of average and anomalous SILCs are examined. Some of the anomalous cells have random telegraph signals (RTSs) of gate leakage current, which are characterized as discrete and random switching phenomena. The dependence of RTSs on the applied electric field is investigated, and the recovery tendency of anomalous SILC with and without RTSs are also discussed.

Effect of Mechanical Stresses on Characteristics of Chip Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2007-01-01

The effect of compressive mechanical stresses on chip solid tantalum capacitors is investigated by monitoring characteristics of different part types under axial and hydrostatic stresses. Depending on part types, an exponential increase of leakage currents was observed when stresses exceeded 10 MPa to 40 MPa. For the first time, reversible variations of leakage currents (up to two orders of magnitude) with stress have been demonstrated. Mechanical stresses did not cause significant changes of AC characteristics of the capacitors, whereas breakdown voltages measured during the surge current testing decreased substantially indicating an increased probability of failures of stressed capacitors in low impedance applications. Variations of leakage currents are explained by a combination of two mechanisms: stress-induced scintillations and stress-induced generation of electron traps in the tantalum pentoxide dielectric.

Reduction of leakage current at the gate edge of SDB SOI NMOS transistor

NASA Astrophysics Data System (ADS)

Kang, Sung-Weon; Lyu, Jong-Son; Kang, Jin-Young; Kang, Sang-Won; Lee, Jin-Hyo

1995-06-01

Leakage current through the parasitic channel formed at the sidewall of the SOI active region has been investigated by measuring the subthreshold I-V characteristics. Partially depleted (PD, approximately 2500 Angstrom) and fully depleted (FD, approximately 800 Angstrom) SOI NMOS transistors of enhancement mode have been fabricated using the silicon direct bonding (SDB) technology. Isolation processes for the SOI devices were LOCOS, LOCOS with channel stop ion implantation or fully recessed trench (FRT). The electron concentration of the parasitic channel is calculated by the PISCES Ilb simulation. As a result, leakage current of the FD mode SOI device with FRT isolation at the front and back gate biases of 0 V was reduced to approximately pA and no hump was seen on the drain current curve.

Complex capacitance in the representation of modulus of the lithium niobate crystals

NASA Astrophysics Data System (ADS)

Alim, Mohammad A.; Batra, A. K.; Bhattacharjee, Sudip; Aggarwal, M. D.

2011-03-01

The lithium niobate (LiNbO 3 or LN) single crystal is grown in-house. The ac small-signal electrical characterization is conducted over a temperature range 35 ≤T≤150 °C as a function of measurement frequency (10 ≤f≤10 6 Hz). Meaningful observation is noted only in a narrow temperature range 59 ≤T≤73 °C. These electrical data when analyzed via complex plane formalisms revealed single semicircular relaxation both in the complex capacitance ( C*) and in the modulus ( M*) planes. The physical meaning of this kind of observation is obtained on identifying the relaxation type, and then incorporating respective equivalent circuit model. The simplistic non-blocking nature of the equivalent circuit model obtained via M*-plane is established as the lumped relaxation is identified in the C*-plane. The feature of the eventual equivalent circuit model allows non-blocking aspect for the LN crystal attributing to the presence of the operative dc conduction process. Identification of this leakage dc conduction via C*-plane is portrayed in the M*-plane where the blocking nature is removed. The interacting interpretation between these two complex planes is successfully presented.

The role of localized junction leakage in the temperature-dependent laser-beam-induced current spectra for HgCdTe infrared focal plane array photodiodes

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

Feng, A. L.; Li, G., E-mail: liguang1971@ahu.edu.cn, E-mail: xschen@mail.sitp.ac.cn; He, G.

2013-11-07

We have performed the study on the dependence of laser beam induced current (LBIC) spectra on the temperature for the vacancy-doped molecular beam epitaxy grown Hg{sub 1−x}Cd{sub x}Te (x = 0.31) photodiodes by both experiment and numerical simulations. It is found that the measured LBIC signal has different distributions for different temperature extents. The LBIC profile tends to be more asymmetric with increasing temperature below 170 K. But the LBIC profile becomes more symmetric with increasing temperature above 170 K. Based on a localized leakage model, it is indicated that the localized junction leakage can lead to asymmetric LBIC signal, in good agreement withmore » the experimental data. The reason is that the trap-assisted tunneling current is the dominant leakage current at the cryogenic temperature below 170 K while the diffusion current component becomes dominant above the temperature of 170 K. The results are helpful for us to better clarify the mechanism of the dependence of LBIC spectra on temperature for the applications of HgCdTe infrared photodiodes.« less

Preparation and properties of sol-gel derived PZT thin films for decoupling capacitor applications

NASA Astrophysics Data System (ADS)

Schwartz, R. W.; Dimos, D.; Lockwood, S. J.; Torres, V. M.

The use of ceramic thin films as decoupling capacitors offers the possibility of capacitor integration within the integrated circuit (IC) package and, potentially, directly onto the IC itself. Since these configurations minimize series inductance, higher operational speeds are possible. In the present study, the authors have investigated the dielectric and leakage characteristics of sol-gel PZT films. For compositions near the morphotropic phase boundary, dielectric constants of 1000, and loss tangents of about 0.02, are observed. The current-voltage behavior of the capacitors is characterized by a non-linear response, and significant asymmetry in both the leakage and breakdown characteristics as a function of bias sign is observed. Breakdown fields for PZT 53/47 thin films are typically approximately 800 kV/cm at 25 C. The authors have also studied the effects of La and Nb dopant additions and alternate firing strategies on film leakage characteristics. Donor doping at 2 - 5 mol % lowers leakage currents by a factor of 10(exp 3). For films prepared by a multilayering approach, firing each layer to crystallization results in leakage currents that are a factor of 10(exp 2) lower than films prepared by the standard process.

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

Peng, Yong; Yao, Manwen, E-mail: yaomw@tongji.edu.cn; Chen, Jianwen

The electrical characteristics of SrTiO{sub 3}/Al{sub 2}O{sub 3} (160 nm up/90 nm down) laminated film capacitors using the sol-gel process have been investigated. SrTiO{sub 3} is a promising and extensively studied high-K dielectric material, but its leakage current property is poor. SrTiO{sub 3}/Al{sub 2}O{sub 3} laminated films can effectively suppress the demerits of pure SrTiO{sub 3} films under low electric field, but the leakage current value reaches to 0.1 A/cm{sup 2} at higher electric field (>160 MV/m). In this study, a new approach was applied to reduce the leakage current and improve the dielectric strength of SrTiO{sub 3}/Al{sub 2}O{sub 3} laminated films. Compared tomore » laminated films with Au top electrodes, dielectric strength of laminated films with Al top electrodes improves from 205 MV/m to 322 MV/m, simultaneously the leakage current maintains the same order of magnitude (10{sup −4} A/cm{sup 2}) until the breakdown occurs. The above electrical characteristics are attributed to the anodic oxidation reaction in origin, which can repair the defects of laminated films at higher electric field. The anodic oxidation reactions have been confirmed by the corresponding XPS measurement and the cross sectional HRTEM analysis. This work provides a new approach to fabricate dielectrics with high dielectric strength and low leakage current.« less

The Value of Changing Position in the Detection of CSF Leakage in Spontaneous Intracranial Hypotension Using Tc-99m DTPA Scintigraphy: Two Case Reports.

PubMed

Lu, Yu Yu; Wang, Hsin Yi; Lin, Ying; Lin, Wan Yu

2012-09-01

Radionuclide Cisternography (RNC) is of potential value in pointing out the sites of cerebrospinal fluid (CSF) leakage in patients with spontaneous intracranial hypotension (SIH). In the current report, we present two patients who underwent RNC for suspected CSF leakage. Both patients underwent magnetic resonance imaging (MRI) and RNC for evaluation. We describe a simple method to increase the detection ability of RNC for CSF leakage in patients with SIH.

Using provenance of terrigenous sediment to reconstruct the Agulhas Leakage during the Early and Late Pleistocene

NASA Astrophysics Data System (ADS)

Pearson, B.; Franzese, A. M.

2017-12-01

The Agulhas Current, the strongest western boundary current in the southern hemisphere, is uniquely characterized by its strong retroflection. The current carries water southward from the Indian Ocean toward the cape of South Africa, before turning back on itself. At this point of retroflection, some of the current's flow escapes into the southern Atlantic Ocean. This transfer of water from the Indian Ocean to Atlantic Ocean makes up the Agulhas Leakage. The Leakage occurs in a series of eddies and rings located in the Cape Basin south of the African continent. Scientific literature demonstrates that relatively buoyant leakage water has been a determining factor varying strength of the Atlantic Meridional Ocean Current (AMOC), during glacial-interglacial cycles. It has been demonstrated that radiogenic isotope, major, and trace element concentrations serve as a proxy for terrigenous sediment provenance in the Agulhas region. Current understanding is that terrigenous sediment provenance is older during warmer periods of deposition. This corresponds to more input from southeastern African end members, and thus a stronger Agulhas Current, during warming periods in the paleoclimate record. Conversely, younger terrigenous sediment deposited during colder periods, such as the Last Glacial Maximum, suggests a weaker Agulhas Current, and less Agulhas Leakage. In 2016, on the International Ocean Discovery Program Expedition 361, sediment cores were drilled at 6 sites in the Greater Agulhas region. A major goal of the expedition was to expand knowledge of the relation between changes in the Agulhas System and changes in paleoclimate, southern African climate, and AMOC. We analyzed sediment from Expedition 361 Site U1479 (35°03.53'S; 17°24.06'E; 2615 mbsl) located where the Agulhas Leakage occurs. We measured Argon, strontium isotope ratios, ɛNd, trace and major element concentrations on the <2 micron clay fraction. Preliminary results foretell promising findings. For instance, for the Early Pleistocene ( 1.3 - 1.5 Ma), K-Ar model ages correlate with shipboard measurements of natural gamma radiation, which show approximate 41 kyr periodicity.

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.

Detecting subsurface fluid leaks in real-time using injection and production rates

NASA Astrophysics Data System (ADS)

Singh, Harpreet; Huerta, Nicolas J.

2017-12-01

CO2 injection into geologic formations for either enhanced oil recovery or carbon storage introduces a risk for undesired fluid leakage into overlying groundwater or to the surface. Despite decades of subsurface CO2 production and injection, the technologies and methods for detecting CO2 leaks are still costly and prone to large uncertainties. This is especially true for pressure-based monitoring methods, which require the use of simplified geological and reservoir flow models to simulate the pressure behavior as well as background noise affecting pressure measurements. In this study, we propose a method to detect the time and volume of fluid leakage based on real-time measurements of well injection and production rates. The approach utilizes analogies between fluid flow and capacitance-resistance modeling. Unlike other leak detection methods (e.g. pressure-based), the proposed method does not require geological and reservoir flow models to simulate the behavior that often carry significant sources of uncertainty; therefore, with our approach the leak can be detected with greater certainty. The method can be applied to detect when a leak begins by tracking a departure in fluid production rate from the expected pattern. The method has been tuned to detect the effect of boundary conditions and fluid compressibility on leakage. To highlight the utility of this approach we use our method to detect leaks for two scenarios. The first scenario simulates a fluid leak from the storage formation into an above-zone monitoring interval. The second scenario simulates intra-reservoir migration between two compartments. We illustrate this method to detect fluid leakage in three different reservoirs with varying levels of geological and structural complexity. The proposed leakage detection method has three novelties: i) requires only readily-available data (injection and production rates), ii) accounts for fluid compressibility and boundary effects, and iii) in addition to detecting the time when a leak is activated and the volume of that leakage, this method provides an insight about the leak location, and reservoir connectivity. We are proposing this as a complementary method that can be used with other, more expensive, methods early on in the injection process. This will allow an operator to conduct more expensive surveys less often because the proposed method can show if there are no leaks on a monthly basis that is cheap and fast.

Improving accuracy of electrochemical capacitance and solvation energetics in first-principles calculations

NASA Astrophysics Data System (ADS)

Sundararaman, Ravishankar; Letchworth-Weaver, Kendra; Schwarz, Kathleen A.

2018-04-01

Reliable first-principles calculations of electrochemical processes require accurate prediction of the interfacial capacitance, a challenge for current computationally efficient continuum solvation methodologies. We develop a model for the double layer of a metallic electrode that reproduces the features of the experimental capacitance of Ag(100) in a non-adsorbing, aqueous electrolyte, including a broad hump in the capacitance near the potential of zero charge and a dip in the capacitance under conditions of low ionic strength. Using this model, we identify the necessary characteristics of a solvation model suitable for first-principles electrochemistry of metal surfaces in non-adsorbing, aqueous electrolytes: dielectric and ionic nonlinearity, and a dielectric-only region at the interface. The dielectric nonlinearity, caused by the saturation of dipole rotational response in water, creates the capacitance hump, while ionic nonlinearity, caused by the compactness of the diffuse layer, generates the capacitance dip seen at low ionic strength. We show that none of the previously developed solvation models simultaneously meet all these criteria. We design the nonlinear electrochemical soft-sphere solvation model which both captures the capacitance features observed experimentally and serves as a general-purpose continuum solvation model.

Synthesis of ultrathin polymer insulating layers by initiated chemical vapour deposition for low-power soft electronics.

PubMed

Moon, Hanul; Seong, Hyejeong; Shin, Woo Cheol; Park, Won-Tae; Kim, Mincheol; Lee, Seungwon; Bong, Jae Hoon; Noh, Yong-Young; Cho, Byung Jin; Yoo, Seunghyup; Im, Sung Gap

2015-06-01

Insulating layers based on oxides and nitrides provide high capacitance, low leakage, high breakdown field and resistance to electrical stresses when used in electronic devices based on rigid substrates. However, their typically high process temperatures and brittleness make it difficult to achieve similar performance in flexible or organic electronics. Here, we show that poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3) prepared via a one-step, solvent-free technique called initiated chemical vapour deposition (iCVD) is a versatile polymeric insulating layer that meets a wide range of requirements for next-generation electronic devices. Highly uniform and pure ultrathin films of pV3D3 with excellent insulating properties, a large energy gap (>8 eV), tunnelling-limited leakage characteristics and resistance to a tensile strain of up to 4% are demonstrated. The low process temperature, surface-growth character, and solvent-free nature of the iCVD process enable pV3D3 to be grown conformally on plastic substrates to yield flexible field-effect transistors as well as on a variety of channel layers, including organics, oxides, and graphene.

Synthesis of a highly efficient 3D graphene-CNT-MnO2-PANI nanocomposite as a binder free electrode material for supercapacitors.

PubMed

Asif, Muhammad; Tan, Yi; Pan, Lujun; Rashad, Muhammad; Li, Jiayan; Fu, Xin; Cui, Ruixue

2016-09-29

Graphene based nanocomposites have been investigated intensively, as electrode materials for energy storage applications. In the current work, a graphene-CNT-MnO 2 -PANI (GCM@PANI) nanocomposite has been synthesized on 3D graphene grown on nickel foam, as a highly efficient binder free electrode material for supercapacitors. Interestingly, the specific capacitance of the synthesized electrode increases up to the first 1500 charge-discharge cycles, and is thus referred to as an electrode activation process. The activated GCM@PANI nanocomposite electrode exhibits an extraordinary galvanostatic specific capacitance of 3037 F g -1 at a current density of 8 A g -1 . The synthesized nanocomposite exhibits an excellent cyclic stability with a capacitance retention of 83% over 12 000 charge-discharge cycles, and a high rate capability by retaining a specific capacitance of 84.6% at a current density of 20 A g -1 . The structural and electrochemical analysis of the synthesized nanocomposite suggests that the astonishing electrochemical performance might be attributed to the growth of a novel PANI nanoparticle layer and the synergistic effect of CNT/MnO 2 nanostructures.

Mechanism of a-IGZO TFT device deterioration—illumination light wavelength and substrate temperature effects

NASA Astrophysics Data System (ADS)

Chen, Te-Chih; Kuo, Yue; Chang, Ting-Chang; Chen, Min-Chen; Chen, Hua-Mao

2017-10-01

Device characteristics changes in an a-IGZO thin film transistor under light illumination and at raised temperature have been investigated. Light exposure causes a large leakage current, which is more obvious with an increase in the illumination energy, power and the temperature. The increase in the leakage current is due to the trap assisted photon excitation process that generates electron-hole pairs and the mechanism is enhanced with the additional thermal energy. The leakage current comes from the source side because holes generated in the process drift to the source side and therefore lower the barrier height. The above mechanism has been further verified with experiments of drain bias induced shifts in the threshold voltage and the subthreshold slope.

The effect of guard ring on leakage current and spectroscopic performance of TlBr planar detectors

NASA Astrophysics Data System (ADS)

Kargar, Alireza; Kim, Hadong; Cirignano, Leonard; Shah, Kanai

2014-09-01

Four thallium bromide planar detectors were fabricated from materials grown at RMD Inc. The TlBr samples were prepared to investigate the effect of guard ring on device gamma-ray spectroscopy performance, and to investigate the leakage current through surface and bulk. The devices' active area in planar configuration were 4.4 × 4.4 × 1.0 mm3. In this report, the detector fabrication process is described and the resulting energy spectra are discussed. It is shown that the guard ring improves device spectroscopic performance by shielding the sensing electrode from the surface leakage current, and by making the electric filed more uniform in the active region of the device.

Thermal Transients Excite Neurons through Universal Intramembrane Mechanoelectrical Effects

NASA Astrophysics Data System (ADS)

Plaksin, Michael; Shapira, Einat; Kimmel, Eitan; Shoham, Shy

2018-01-01

Modern advances in neurotechnology rely on effectively harnessing physical tools and insights towards remote neural control, thereby creating major new scientific and therapeutic opportunities. Specifically, rapid temperature pulses were shown to increase membrane capacitance, causing capacitive currents that explain neural excitation, but the underlying biophysics is not well understood. Here, we show that an intramembrane thermal-mechanical effect wherein the phospholipid bilayer undergoes axial narrowing and lateral expansion accurately predicts a potentially universal thermal capacitance increase rate of ˜0.3 % /°C . This capacitance increase and concurrent changes in the surface charge related fields lead to predictable exciting ionic displacement currents. The new MechanoElectrical Thermal Activation theory's predictions provide an excellent agreement with multiple experimental results and indirect estimates of latent biophysical quantities. Our results further highlight the role of electro-mechanics in neural excitation; they may also help illuminate subthreshold and novel physical cellular effects, and could potentially lead to advanced new methods for neural control.

Nano ZnO-activated carbon composite electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Selvakumar, M.; Krishna Bhat, D.; Manish Aggarwal, A.; Prahladh Iyer, S.; Sravani, G.

2010-05-01

A symmetrical (p/p) supercapacitor has been fabricated by making use of nanostructured zinc oxide (ZnO)-activated carbon (AC) composite electrodes for the first time. The composites have been characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction analysis (XRD). Electrochemical properties of the prepared nanocomposite electrodes and the supercapacitor have been studied using cyclic voltammetry (CV) and AC impedance spectroscopy in 0.1 M Na 2SO 4 as electrolyte. The ZnO-AC nanocomposite electrode showed a specific capacitance of 160 F/g for 1:1 composition. The specific capacitance of the electrodes decreased with increase in zinc oxide content. Galvanostatic charge-discharge measurements have been done at various current densities, namely 2, 4, 6 and 7 mA/cm 2. It has been found that the cells have excellent electrochemical reversibility and capacitive characteristics in 0.1 M Na 2SO 4 electrolyte. It has also been observed that the specific capacitance is constant up to 500 cycles at all current densities.

Outstanding supercapacitive properties of Mn-doped TiO2 micro/nanostructure porous film prepared by anodization method

PubMed Central

Ning, Xuewen; Wang, Xixin; Yu, Xiaofei; Zhao, Jianling; Wang, Mingli; Li, Haoran; Yang, Yang

2016-01-01

Mn-doped TiO2 micro/nanostructure porous film was prepared by anodizing a Ti-Mn alloy. The film annealed at 300 °C yields the highest areal capacitance of 1451.3 mF/cm2 at a current density of 3 mA/cm2 when used as a high-performance supercapacitor electrode. Areal capacitance retention is 63.7% when the current density increases from 3 to 20 mA/cm2, and the capacitance retention is 88.1% after 5,000 cycles. The superior areal capacitance of the porous film is derived from the brush-like metal substrate, which could greatly increase the contact area, improve the charge transport ability at the oxide layer/metal substrate interface, and thereby significantly enhance the electrochemical activities toward high performance energy storage. Additionally, the effects of manganese content and specific surface area of the porous film on the supercapacitive performance were also investigated in this work. PMID:26940546

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

Leakage current suppression with a combination of planarized gate and overlap/off-set structure in metal-induced laterally crystallized polycrystalline-silicon thin-film transistors

NASA Astrophysics Data System (ADS)

Chae, Hee Jae; Seok, Ki Hwan; Lee, Sol Kyu; Joo, Seung Ki

2018-04-01

A novel inverted staggered metal-induced laterally crystallized (MILC) polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) with a combination of a planarized gate and an overlap/off-set at the source-gate/drain-gate structure were fabricated and characterized. While the MILC process is advantageous for fabricating inverted staggered poly-Si TFTs, MILC TFTs reveal higher leakage current than TFTs crystallized by other processes due to their high trap density of Ni contamination. Due to this drawback, the planarized gate and overlap/off-set structure were applied to inverted staggered MILC TFTs. The proposed device shows drastic suppression of leakage current and pinning phenomenon by reducing the lateral electric field and the space-charge limited current from the gate to the drain.

Electrochemical and Capacitive Properties of Carbon Dots/Reduced Graphene Oxide Supercapacitors.

PubMed

Dang, Yong-Qiang; Ren, Shao-Zhao; Liu, Guoyang; Cai, Jiangtao; Zhang, Yating; Qiu, Jieshan

2016-11-14

There is much recent interest in graphene-based composite electrode materials because of their excellent mechanical strengths, high electron mobilities, and large specific surface areas. These materials are good candidates for applications in supercapacitors. In this work, a new graphene-based electrode material for supercapacitors was fabricated by anchoring carbon dots (CDs) on reduced graphene oxide (rGO). The capacitive properties of electrodes in aqueous electrolytes were systematically studied by galvanostatic charge-discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy. The capacitance of rGO was improved when an appropriate amount of CDs were added to the material. The CD/rGO electrode exhibited a good reversibility, excellent rate capability, fast charge transfer, and high specific capacitance in 1 M H₂SO₄. Its capacitance was as high as 211.9 F/g at a current density of 0.5 A/g. This capacitance was 74.3% higher than that of a pristine rGO electrode (121.6 F/g), and the capacitance of the CD/rGO electrode retained 92.8% of its original value after 1000 cycles at a CDs-to-rGO ratio of 5:1.

Electrophysiological Evidence for the Presence of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) in Mouse Sperm

PubMed Central

Dulce, Figueiras Fierro; José, Acevedo Juan; Pablo, Martínez; Escoffier, Jessica; Sepúlveda, Francisco V.; Enrique, Balderas; Gerardo, Orta; Pablo, Visconti; Alberto, Darszon

2014-01-01

Mammalian sperm must undergo a maturational process, named capacitation, in the female reproductive tract to fertilize the egg. Sperm capacitation is regulated by a cAMP/PKA pathway and involves increases in intracellular Ca2+, pH, Cl−, protein tyrosine phosphorylation, and in mouse and some other mammals a membrane potential hyperpolarization. The cystic fibrosis transmembrane conductance regulator (CFTR), a Cl− channel modulated by cAMP/PKA and ATP, was detected in mammalian sperm and proposed to modulate capacitation. Our whole-cell patch-clamp recordings from testicular mouse sperm now reveal a Cl− selective component to membrane current that is ATP-dependent, stimulated by cAMP, cGMP and genistein (a CFTR agonist, at low concentrations), and inhibited by DPC and CFTRinh-172, two well-known CFTR antagonists. Furthermore, the Cl− current component activated by cAMP and inhibited by CFTRinh-172 is absent in recordings on testicular sperm from mice possessing the CFTR ΔF508 loss-of-function mutation, indicating that CFTR is responsible for this component. A Cl− selective like current component displaying CFTR characteristics was also found in wild type epididymal sperm bearing the cytoplasmatic droplet. Capacitated sperm treated with CFTRinh-172 undergo a shape change, suggesting that CFTR is involved in cell volume regulation. These findings indicate that functional CFTR channels are present in mouse sperm and their biophysical properties are consistent with their proposed participation in capacitation. PMID:22833409

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.

Vertically porous nickel thin film supported Mn3O4 for enhanced energy storage performance.

PubMed

Li, Xiao-Jun; Song, Zhi-Wei; Zhao, Yong; Wang, Yue; Zhao, Xiu-Chen; Liang, Minghui; Chu, Wei-Guo; Jiang, Peng; Liu, Ying

2016-12-01

Three-dimensionally porous metal materials are often used as the current collectors and support for the active materials of supercapacitors. However, the applications of vertically porous metal materials in supercapacitors are rarely reported, and the effect of vertically porous metal materials on the energy storage performance of supported metal oxides is not explored. To this end, the Mn3O4-vertically porous nickel (VPN) electrodes are fabricated via a template-free method. The Mn3O4-VPN electrode shows much higher volumetric specific capacitances than that of flat nickel film supported Mn3O4 with the same loading under the same measurement conditions. The volumetric specific capacitance of the vertically porous nickel supported Mn3O4 electrode can reach 533Fcm(-3) at the scan rate of 2mVs(-1). The fabricated flexible all-solid microsupercapacitor based on the interdigital Mn3O4-VPN electrode has a volumetric specific capacitance of 110Fcm(-3) at the current density of 20μAcm(-2). The capacitance retention rate of this microsupercapacitor reaches 95% after 5000 cycles under the current density of 20μAcm(-2). The vertical pores in the nickel electrode not only fit the micro/nanofabrication process of the Mn3O4-VPN electrode, but also play an important role in enhancing the capacitive performances of supported Mn3O4 particles. Copyright © 2016 Elsevier Inc. All rights reserved.

Systematic review of methods to predict and detect anastomotic leakage in colorectal surgery.

PubMed

Hirst, N A; Tiernan, J P; Millner, P A; Jayne, D G

2014-02-01

Anastomotic leakage is a serious complication of gastrointestinal surgery resulting in increased morbidity and mortality, poor function and predisposing to cancer recurrence. Earlier diagnosis and intervention can minimize systemic complications but is hindered by current diagnostic methods that are non-specific and often uninformative. The purpose of this paper is to review current developments in the field and to identify strategies for early detection and treatment of anastomotic leakage. A systematic literature search was performed using the MEDLINE, Embase, PubMed and Cochrane Library databases. Search terms included 'anastomosis' and 'leak' and 'diagnosis' or 'detection' and 'gastrointestinal' or 'colorectal'. Papers concentrating on the diagnosis of gastrointestinal anastomotic leak were identified and further searches were performed by cross-referencing. Computerized tomography CT scanning and water-soluble contrast studies are the current preferred techniques for diagnosing anastomotic leakage but suffer from variable sensitivity and specificity, have logistical constraints and may delay timely intervention. Intra-operative endoscopy and imaging may offer certain advantages, but the ability to predict anastomotic leakage is unproven. Newer techniques involve measurement of biomarkers for anastomotic leakage and have the potential advantage of providing cheap real-time monitoring for postoperative complications. Current diagnostic tests often fail to diagnose anastomotic leak at an early stage that enables timely intervention and minimizes serious morbidity and mortality. Emerging technologies, based on detection of local biomarkers, have achieved proof of concept status but require further evaluation to determine whether they translate into improved patient outcomes. Further research is needed to address this important, yet relatively unrecognized, area of unmet clinical need. Colorectal Disease © 2013 The Association of Coloproctology of Great Britain and Ireland.

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)

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.

Potential for EMU Fabric Damage by Electron Beam and Molten Metal During Space Welding for the International Space Welding Experiment

NASA Technical Reports Server (NTRS)

Fragomeni, James M.

1998-01-01

As a consequence of preparations concerning the International Space Welding Experiment (ISWE), studies were performed to better understand the effect of molten metal contact and electron beam impingement with various fabrics for space suit applications. The question arose as to what would occur if the electron beam from the Ukrainian Universal Hand Tool (UHT) designed for welding in space were to impinge upon a piece of Nextel AF-62 ceramic cloth designed to withstand temperatures up to 1427 C. The expectation was that the electron beam would lay down a static charge pattern with no damage to the ceramic fabric. The electron beam is capable of spraying the fabric with enough negative charge to repel further electrons from the fabric before significant heating occurs. The static charge pattern would deflect any further charge accumulation except for a small initial amount of leakage to the grounded surface of the welder. However, when studies were made of the effect of the electron beam on the insulating ceramic fabric it was surprisingly found that the electron beam did indeed burn through the ceramic fabric. It was also found that the shorter electron beam standoff distances had longer burnthrough times than did some greater electron beam standoff distances. A possible explanation for the longer burnthrough times for the small electron beam standoff distance would be outgassing of the fabric which caused the electron beam hand-tool to cycle on and off to provide some protection for the cathodes. The electron beam hand tool was observed to cycle off at the short standoff distance of two inches likely due to vapors being outgassed. During the electron beam welding process there is an electron leakage, or current leakage, flow from the fabric. A static charge pattern is initially laid down by the electron beam current flow. The static charge makes up the current leakage flow which initially slightly heats up the fabric. The initially laid down surface charge leaks a small amount of current. The rate at which the current charge leaks from the fabric controls how fast the fabric heats up. As the ceramic fabric is heated it begins to outgass primarily from contamination/impurities atoms or molecules on and below the fabric surface. The contaminant gases ionize to create extra charge carriers and multiply a current of electrons. The emitted gas which ionized in the electron leakage flow promotes further leakage. Thus, the small leakage of charge from the fabric surface is enhanced by outgassing. When the electron beam current makes up the lost current, the incoming electrons heat the fabric and further enhance the outgassing. The additional leakage promotes additional heating up of the ceramic fabric. The electrons bound to the ceramic fabric surface leak off more and more as the surface gets hotter promoting even greater leakage. The additional electrons that result also gain energy in the field and produce further electrons. Eventually the process becomes unstable and accelerates to the point where a hole is burned through the fabric.

Epitaxial GeSn film formed by solid phase epitaxy and its application to Yb{sub 2}O{sub 3}-gated GeSn metal-oxide-semiconductor capacitors with sub-nm equivalent oxide thickness

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

Lee, Ching-Wei; Wu, Yung-Hsien; Hsieh, Ching-Heng

2014-11-17

Through the technique of solid phase epitaxy (SPE), an epitaxial Ge{sub 0.955}Sn{sub 0.045} film was formed on a Ge substrate by depositing an amorphous GeSn film followed by a rapid thermal annealing at 550 °C. A process that uses a SiO{sub 2} capping layer on the amorphous GeSn film during SPE was proposed and it prevents Sn precipitation from occurring while maintaining a smooth surface due to the reduced surface mobility of Sn atoms. The high-quality epitaxial GeSn film was observed to have single crystal structure, uniform thickness and composition, and tiny surface roughness with root mean square of 0.56 nm. Withmore » a SnO{sub x}-free surface, Yb{sub 2}O{sub 3}-gated GeSn metal-oxide-semiconductor (MOS) capacitors with equivalent oxide thickness (EOT) of 0.55 nm were developed. A small amount of traps inside the Yb{sub 2}O{sub 3} was verified by negligible hysteresis in capacitance measurement. Low leakage current of 0.4 A/cm{sup 2} at gate bias of flatband voltage (V{sub FB})-1 V suggests the high quality of the gate dielectric. In addition, the feasibility of using Yb{sub 2}O{sub 3} to well passivate GeSn surface was also evidenced by the small interface trap density (D{sub it}) of 4.02 × 10{sup 11} eV{sup −1} cm{sup −2}, which can be attributed to smooth GeSn surface and Yb{sub 2}O{sub 3} valency passivation. Both leakage current and D{sub it} performance outperform other passivation techniques at sub-nm EOT regime. The proposed epitaxial GeSn film along with Yb{sub 2}O{sub 3} dielectric paves an alternative way to enable high-performance GeSn MOS devices.« less

Impact of annealing temperature on the mechanical and electrical properties of sputtered aluminum nitride thin films

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

Gillinger, M.; Schneider, M.; Bittner, A.

2015-02-14

Aluminium nitride (AlN) is a promising material for challenging sensor applications such as process monitoring in harsh environments (e.g., turbine exhaust), due to its piezoelectric properties, its high temperature stability and good thermal match to silicon. Basically, the operational temperature of piezoelectric materials is limited by the increase of the leakage current as well as by enhanced diffusion effects in the material at elevated temperatures. This work focuses on the characterization of aluminum nitride thin films after post deposition annealings up to temperatures of 1000 °C in harsh environments. For this purpose, thin film samples were temperature loaded for 2 hmore » in pure nitrogen and oxygen gas atmospheres and characterized with respect to the film stress and the leakage current behaviour. The X-ray diffraction results show that AlN thin films are chemically stable in oxygen atmospheres for 2 h at annealing temperatures of up to 900 °C. At 1000 °C, a 100 nm thick AlN layer oxidizes completely. For nitrogen, the layer is stable up to 1000 °C. The activation energy of the samples was determined from leakage current measurements at different sample temperatures, in the range between 25 and 300 °C. Up to an annealing temperature of 700 °C, the leakage current in the thin film is dominated by Poole-Frenkel behavior, while at higher annealing temperatures, a mixture of different leakage current mechanisms is observed.« less

On Leakage Current Measured at High Cell Voltages in Lithium-Ion Batteries

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

Vadivel, Nicole R.; Ha, Seungbum; He, Meinan

2017-01-01

In this study, parasitic side reactions in lithium-ion batteries were examined experimentally using a potentiostatic hold at high cell voltage. The experimental leakage current measured during the potentiostatic hold was compared to the Tafel expression and showed poor agreement with the expected transfer coefficient values, indicating that a more complicated expression could be needed to accurately capture the physics of this side reaction. Here we show that cross-talk between the electrodes is the primary contribution to the observed leakage current after the relaxation of concentration gradients has ceased. This cross-talk was confirmed with experiments using a lithium-ion conducting glass ceramicmore » (LICGC) separator, which has high conductance only for lithium cations. The cells with LICGC separators showed significantly less leakage current during the potentiostatic hold test compared to cells with standard microporous separators where cross-talk is present. In addition, direct-current pulse power tests show an impedance rise for cells held at high potentials and for cells held at high temperatures, which could be attributed to film formation from the parasitic side reaction. Based on the experimental findings, a phenomenological mechanism is proposed for the parasitic side reaction which accounts for cross-talk and mass transport of the decomposition products across the separator.« less

[Roles of sialic acids in sperm maturation and capacitation and sperm-egg recognition].

PubMed

Feng, Ying; Wang, Lin; Wu, Yi-Lun; Liu, Hong-Hua; Ma, Fang

2016-10-01

Sialic acids are a subset of nine-carbon alpha-keto aldonic acids involved in various biological functions. Sialic acid on the sperm surface is closely related to sperm maturation and capacitation and sperm-egg recognition, which makes sperm negatively charged to avoid accumulation and covers some antigenic determinants there to increase the survival rate of sperm in the female reproductive tract. The loss of sialic acids is an important factor mediating sperm capacitation. Moreover, the sialic acid at the extremity of the protein polymer is involved in signal identification in sperm-egg recognition. Here, we review the current understanding of sialic acids in sperm maturation and capacitation and sperm-egg recognition.

Capacitance Based Moisture Sensing for Microgravity Plant Modules: Sensor Design and Considerations

NASA Technical Reports Server (NTRS)

Schaber, Chad L.; Nurge, Mark; Monje, Oscar

2011-01-01

Life support systems for growing plants in microgravity should strive for providing optimal growing conditions and increased automation. Accurately tracking soil moisture content can forward both of these aims, so an attempt was made to instrument a microgravity growth module currently in development, the VEGGIE rooting pillow, in order to monitor moisture levels. Two electrode systems for a capacitance-based moisture sensor were tested. Trials with both types of electrodes showed a linear correlation between observed capacitance and water content over certain ranges of moisture within the pillows. Overall, both types of the electrodes and the capacitance-based moisture sensor are promising candidates for tracking water levels for microgravity plant growth systems.

Ionic liquids in a poly ethylene oxide cross-linked gel polymer as an electrolyte for electrical double layer capacitor

NASA Astrophysics Data System (ADS)

Chaudoy, V.; Tran Van, F.; Deschamps, M.; Ghamouss, F.

2017-02-01

In the present work, we developed a gel polymer electrolyte via the incorporation of a room temperature ionic liquid into a cross-linked polymer matrix. The cross-linked gel electrolyte was prepared using a free radical polymerization of methacrylate and dimethacrylate oligomers dissolved in 1-propyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide. Combining the advantages of the ionic liquids and of conventional polymers, the cross-linked gel polymer electrolyte was used both as a separator and as an electrolyte for a leakage-free and non-flammable EDLC supercapacitor. The quasi-all solid-state supercapacitors showed rather good capacitance, power and energy densities by comparison to a liquid electrolyte-based EDLC.

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

Chinthavali, Madhu Sudhan; Wang, Zhiqiang

This paper presents a detailed parametric sensitivity analysis for a wireless power transfer (WPT) system in electric vehicle application. Specifically, several key parameters for sensitivity analysis of a series-parallel (SP) WPT system are derived first based on analytical modeling approach, which includes the equivalent input impedance, active / reactive power, and DC voltage gain. Based on the derivation, the impact of primary side compensation capacitance, coupling coefficient, transformer leakage inductance, and different load conditions on the DC voltage gain curve and power curve are studied and analyzed. It is shown that the desired power can be achieved by just changingmore » frequency or voltage depending on the design value of coupling coefficient. However, in some cases both have to be modified in order to achieve the required power transfer.« less

Defect-Enabled Electrical Current Leakage in Ultraviolet Light-Emitting Diodes

DOE PAGES

Moseley, Michael William; Allerman, Andrew A.; Crawford, Mary H.; ...

2015-04-13

The AlGaN materials system offers a tunable, ultra-wide bandgap that is exceptionally useful for high-power electronics and deep ultraviolet optoelectronics. Moseley et al. (pp. 723–726) investigate a structural defect known as an open-core threading dislocation or ''nanopipe'' that is particularly detrimental to devices that employ these materials. Furthermore, an AlGaN thin film was synthesized using metal-organic chemical-vapor deposition. Electrical current leakage is detected at a discrete point using a conductive atomic-force microscope (CAFM). However, no physical feature or abnormality at this location was visible by an optical microscope. The AlGaN thin film was then etched in hot phosphoric acid, andmore » the same location that was previously analyzed was revisited with the CAFM. The point that previously exhibited electrical current leakage had been decorated with a 1.1 μm wide hexagonal pit, which identified the site of electrical current leakage as a nanopipe and allows these defects to be easily observed by optical microscopy. Moreover, with this nanopipe identification and quantification strategy, the authors were able to correlate decreasing ultraviolet light-emitting diode optical output power with increasing nanopipe density.« less

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

Capacitive transducers

NASA Technical Reports Server (NTRS)

Lucifredi, A. L.

1970-01-01

The theory, applications, and possible structural designs of capacitive transducers are presented. Emphasis is placed on the circuits used in connection with the sensors, such as AM, FM, resonant circuits, mode circuits, direct current circuits, and special circuits. Some criteria for selection of a design or the purchase of a commercial device are given.

A fully automated temperature-dependent resistance measurement setup using van der Pauw method

NASA Astrophysics Data System (ADS)

Pandey, Shivendra Kumar; Manivannan, Anbarasu

2018-03-01

The van der Pauw (VDP) method is widely used to identify the resistance of planar homogeneous samples with four contacts placed on its periphery. We have developed a fully automated thin film resistance measurement setup using the VDP method with the capability of precisely measuring a wide range of thin film resistances from few mΩ up to 10 GΩ under controlled temperatures from room-temperature up to 600 °C. The setup utilizes a robust, custom-designed switching network board (SNB) for measuring current-voltage characteristics automatically at four different source-measure configurations based on the VDP method. Moreover, SNB is connected with low noise shielded coaxial cables that reduce the effect of leakage current as well as the capacitance in the circuit thereby enhancing the accuracy of measurement. In order to enable precise and accurate resistance measurement of the sample, wide range of sourcing currents/voltages are pre-determined with the capability of auto-tuning for ˜12 orders of variation in the resistances. Furthermore, the setup has been calibrated with standard samples and also employed to investigate temperature dependent resistance (few Ω-10 GΩ) measurements for various chalcogenide based phase change thin films (Ge2Sb2Te5, Ag5In5Sb60Te30, and In3SbTe2). This setup would be highly helpful for measurement of temperature-dependent resistance of wide range of materials, i.e., metals, semiconductors, and insulators illuminating information about structural change upon temperature as reflected by change in resistances, which are useful for numerous applications.

High-performance SEGISFET pH Sensor using the structure of double-gate a-IGZO TFTs with engineered gate oxides

NASA Astrophysics Data System (ADS)

Pyo, Ju-Young; Cho, Won-Ju

2017-03-01

In this paper, we propose a high-performance separative extended gate ion-sensitive field-effect transistor (SEGISFET) that consists of a tin dioxide (SnO2) SEG sensing part and a double-gate structure amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) with tantalum pentoxide/silicon dioxide (Ta2O5/SiO2)-engineered top-gate oxide. To increase sensitivity, we maximized the capacitive coupling ratio by applying high-k dielectric at the top-gate oxide layer. As an engineered top-gate oxide, a stack of 25 nm-thick Ta2O5 and 10 nm-thick SiO2 layers was found to simultaneously satisfy a small equivalent oxide thickness (˜17.14 nm), a low leakage current, and a stable interfacial property. The threshold-voltage instability, which is a fundamental issue in a-IGZO TFTs, was improved by low-temperature post-deposition annealing (˜87 °C) using microwave irradiation. The double-gate structure a-IGZO TFTs with engineered top-gate oxide exhibited high mobility, small subthreshold swing, high drive current, and larger on/off current ratio. The a-IGZO SEGISFETs with a dual-gate sensing mode showed a pH sensitivity of 649.04 mV pH-1, which is far beyond the Nernst limit. The non-ideal behavior of ISFETs, hysteresis, and drift effect also improved. These results show that the double-gate structure a-IGZO TFTs with engineered top-gate oxide can be a good candidate for cheap and disposable SEGISFET sensors.

LaAlO{sub 3}/Si capacitors: Comparison of different molecular beam deposition conditions and their impact on electrical properties

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

Pelloquin, Sylvain; Baboux, Nicolas; Albertini, David

2013-01-21

A study of the structural and electrical properties of amorphous LaAlO{sub 3} (LAO)/Si thin films fabricated by molecular beam deposition (MBD) is presented. Two substrate preparation procedures have been explored namely a high temperature substrate preparation technique-leading to a step and terraces surface morphology-and a chemical HF-based surface cleaning. The LAO deposition conditions were improved by introducing atomic plasma-prepared oxygen instead of classical molecular O{sub 2} in the chamber. An Au/Ni stack was used as the top electrode for its electrical characteristics. The physico-chemical properties (surface topography, thickness homogeneity, LAO/Si interface quality) and electrical performance (capacitance and current versus voltagemore » and TunA current topography) of the samples were systematically evaluated. Deposition conditions (substrate temperature of 550 Degree-Sign C, oxygen partial pressure settled at 10{sup -6} Torr, and 550 W of power applied to the O{sub 2} plasma) and post-depositions treatments were investigated to optimize the dielectric constant ({kappa}) and leakage currents density (J{sub Gate} at Double-Vertical-Line V{sub Gate} Double-Vertical-Line = Double-Vertical-Line V{sub FB}- 1 Double-Vertical-Line ). In the best reproducible conditions, we obtained a LAO/Si layer with a dielectric constant of 16, an equivalent oxide thickness of 8.7 A, and J{sub Gate} Almost-Equal-To 10{sup -2}A/cm{sup 2}. This confirms the importance of LaAlO{sub 3} as an alternative high-{kappa} for ITRS sub-22 nm technology node.« less

Impedance spectroscopy study of a catechol-modified activated carbon electrode as active material in electrochemical capacitor

NASA Astrophysics Data System (ADS)

Cougnon, C.; Lebègue, E.; Pognon, G.

2015-01-01

Modified activated carbon (Norit S-50) electrodes with electrochemical double layer (EDL) capacitance and redox capacitance contributions to the electric charge storage were tested in 1 M H2SO4 to quantify the benefit and the limitation of the surface redox reactions on the electrochemical performances of the resulting pseudo-capacitive materials. The electrochemical performances of an electrochemically anodized carbon electrode and a catechol-modified carbon electrode, which make use both EDL capacitance of the porous structure of the carbon and redox capacitance, were compared to the performances obtained for the pristine carbon. Nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the BET surface area, pore size distribution, pore volume and average pore diameter. The electrochemical behavior of carbon materials was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The EIS data were discussed by using a complex capacitance model that allows defining the characteristic time constant, the global capacitance and the frequency at which the maximum charge stored is reached. The EIS measurements were achieved at different dc potential values where a redox activity occurs and the evolution of the capacitance and the capacitive relaxation time with the electrode potential are presented. Realistic galvanostatic charge/discharge measurements performed at different current rates corroborate the results obtained by impedance.

Microdose Induced Drain Leakage Effects in Power Trench MOSFETs: Experiment and Modeling

NASA Astrophysics Data System (ADS)

Zebrev, Gennady I.; Vatuev, Alexander S.; Useinov, Rustem G.; Emeliyanov, Vladimir V.; Anashin, Vasily S.; Gorbunov, Maxim S.; Turin, Valentin O.; Yesenkov, Kirill A.

2014-08-01

We study experimentally and theoretically the micro-dose induced drain-source leakage current in the trench power MOSFETs under irradiation with high-LET heavy ions. We found experimentally that cumulative increase of leakage current occurs by means of stochastic spikes corresponding to a strike of single heavy ion into the MOSFET gate oxide. We simulate this effect with the proposed analytic model allowing to describe (including Monte Carlo methods) both the deterministic (cumulative dose) and stochastic (single event) aspects of the problem. Based on this model the survival probability assessment in space heavy ion environment with high LETs was proposed.

A compact model of the reverse gate-leakage current in GaN-based HEMTs

NASA Astrophysics Data System (ADS)

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

2016-12-01

The gate-leakage behavior in GaN-based high electron mobility transistors (HEMTs) is studied as a function of applied bias and temperature. A model to calculate this current is given, which shows that trap-assisted tunneling, trap-assisted Frenkel-Poole (FP) emission, and direct Fowler-Nordheim (FN) tunneling have their main contributions at different electric field regions. In addition, the proposed model clearly illustrates the effect of traps and their assistance to the gate leakage. We have demonstrated the validity of the model by comparisons between model simulation results and measured experimental data of HEMTs, and a good agreement is obtained.

Advanced Wet Tantalum Capacitors: Design, Specifications and Performance

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2016-01-01

Insertion of new types of commercial, high volumetric efficiency wet tantalum capacitors in space systems requires reassessment of the existing quality assurance approaches that have been developed for capacitors manufactured to MIL-PRF-39006 requirements. The specifics of wet electrolytic capacitors is that leakage currents flowing through electrolyte can cause gas generation resulting in building up of internal gas pressure and rupture of the case. The risk associated with excessive leakage currents and increased pressure is greater for high value advanced wet tantalum capacitors, but it has not been properly evaluated yet. This presentation gives a review of specifics of the design, performance, and potential reliability risks associated with advanced wet tantalum capacitors. Problems related to setting adequate requirements for DPA, leakage currents, hermeticity, stability at low and high temperatures, ripple currents for parts operating in vacuum, and random vibration testing are discussed. Recommendations for screening and qualification to reduce risks of failures have been suggested.

Advanced Wet Tantalum Capacitors: Design, Specifications and Performance

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2017-01-01

Insertion of new types of commercial, high volumetric efficiency wet tantalum capacitors in space systems requires reassessment of the existing quality assurance approaches that have been developed for capacitors manufactured to MIL-PRF-39006 requirements. The specifics of wet electrolytic capacitors is that leakage currents flowing through electrolyte can cause gas generation resulting in building up of internal gas pressure and rupture of the case. The risk associated with excessive leakage currents and increased pressure is greater for high value advanced wet tantalum capacitors, but it has not been properly evaluated yet. This presentation gives a review of specifics of the design, performance, and potential reliability risks associated with advanced wet tantalum capacitors. Problems related to setting adequate requirements for DPA, leakage currents, hermeticity, stability at low and high temperatures, ripple currents for parts operating in vacuum, and random vibration testing are discussed. Recommendations for screening and qualification to reduce risks of failures have been suggested.

Detection and modeling of leakage current in AlGaN-based deep ultraviolet light-emitting diodes

DOE PAGES

Moseley, Michael William; Allerman, Andrew A.; Crawford, Mary H.; ...

2015-03-01

Current-voltage (IV) characteristics of two AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) with differing densities of open-core threading dislocations (nanopipes) are analyzed. A three-diode circuit is simulated to emulate the IV characteristics of the DUV-LEDs, but is only able to accurately model the lower leakage current, lower nanopipe density DUV-LED. It was found that current leakage through the nanopipes in these structures is rectifying, despite nanopipes being previously established as inherently n-type. Using defect-sensitive etching, the nanopipes are revealed to terminate within the p-type GaN capping layer of the DUV-LEDs. The circuit model is modified to account for another p-nmore » junction between the n-type nanopipes and the p-type GaN, and an excellent fit to the IV characteristics of the leaky DUV-LED is achieved.« less

Leakage Currents in Low-Voltage PME and BME Ceramic Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2015-01-01

Introduction of BME capacitors to high-reliability electronics as a replacement for PME capacitors requires better understanding of changes in performance and reliability of MLCCs to set justified screening and qualification requirements. In this work, absorption and leakage currents in various lots of commercial and military grade X7R MLCCs rated to 100V and less have been measured to reveal difference in behavior of PME and BME capacitors in a wide range of voltages and temperatures. Degradation of leakage currents and failures in virgin capacitors and capacitors with introduced cracks has been studied at different voltages and temperatures during step stress highly accelerated life testing. Mechanisms of charge absorption, conduction and degradation have been discussed and a failure model in capacitors with defects suggested.

Lanthanide-based oxides and silicates for high-kappa gate dielectric applications

NASA Astrophysics Data System (ADS)

Jur, Jesse Stephen

The ability to improve performance of the high-end metal oxide semiconductor field effect transistor (MOSFET) is highly reliant on the dimensional scaling of such a device. In scaling, a decrease in dielectric thickness results in high current leakage between the electrode and the substrate by way of direct tunneling through the gate dielectric. Observation of a high leakage current when the standard gate dielectric, SiO2, is decreased below a thickness of 1.5 nm requires engineering of a replacement dielectric that is much more scalable. This high-kappa dielectric allows for a physically thicker oxide, reducing leakage current. Integration of select lanthanide-based oxides and silicates, in particular lanthanum oxide and silicate, into MOS gate stack devices is examined. The quality of the high-kappa dielectrics is monitored electrically to determine properties such as equivalent oxide thickness, leakage current density and defect densities. In addition, analytical characterization of the dielectric and the gate stack is provided to examine the materialistic significance to the change of the electrical properties of the devices. In this work, lanthanum oxide films have been deposited by thermal evaporation on to a pre-grown chemical oxide layer on silicon. It is observed that the SiO2 interfacial layer can be consumed by a low-temperature reaction with lanthanum oxide to produce a high-quality silicate. This is opposed to depositing lanthanum oxide directly on silicon, which can possibly favor silicide formation. The importance of oxygen regulation in the surrounding environment of the La2O3-SiO2 reaction-anneal is observed. By controlling the oxygen available during the reaction, SiO2 growth can be limited to achieve high stoichiometric ratios of La2O 3 to SiO2. As a result, MOS devices with an equivalent oxide thickness (EOT) of 5 A and a leakage current density of 5.0 A/cm 2 are attained. This data equals the best value achieved in this field and is a substantial improvement over SiO(N) dielectrics, allowing for increased device scaling. High-temperature processing, consistent with the source/drain activation anneal in MOSFET processing, is performed on lanthanum-silicate based MOS devices with Ta or TaN gate electrodes and a W metal capping layer. The thermal limit of Ta is observed to be less than 800°C, resulting in a phase transformation that can result in uncontrolled shifting of the MOS device flat-band voltage. TaN is observed to be more thermally stable (up to 1000°C) and results in an increase in the capacitance density suggesting that it impedes oxygen reaction with silicon to produce SiO2. It is later observed that a W metal capping layer can serve as a high-oxygen source, which results in an increased interfacial SiO2 formation. By limiting the oxygen content in the W capping layer and by utilizing a thermally stable TaN gate electrode, control over the electrical properties of the MOS device is acquired. To determine the stability of amorphous lanthanum-silicate in contact with investigated by means of back-side secondary ion mass spectroscopy profiling. The results are the first reported data showing that the lanthanum incorporated in the silica matrix doe not diffuse into the silicon substrate after high temperature processing. The decrease in the device effective work function (φM,eff ) observed in these samples is examined in detail. First, as a La 2O3 capping layer on HfSiO(N), the shift yields ideal-φ M,eff values for nMOSFET deices (4.0 eV) that were previously inaccessible. Other lanthanide oxides (Dy, Ho and Yb) used as capping layers show similar effects. It is also shown that tuning of φM,eff can be realized by controlling the extent of lanthanide-silicate formation. This research, conducted in conjunction with SEMATECH and the SRC, represents a significant technological advancement in realizing 45 and sub-45 nm MOSFET device nodes.

Nitrogen/Sulfur-Codoped Carbon Materials from Chitosan for Supercapacitors

NASA Astrophysics Data System (ADS)

Li, Mei; Han, Xianlong; Chang, Xiaoqing; Yin, Wenchao; Ma, Jingyun

2016-08-01

d-Methionine and chitosan have been used for fabrication of nitrogen/sulfur-codoped carbon materials by a hydrothermal process followed by carbonization at 750°C for 3 h. The as-prepared carbon materials showed enhanced electrochemical performance, combining electrical double-layer capacitance with pseudocapacitance owing to the doping with sulfur and nitrogen. The specific capacitance of the obtained carbon material reached 135 F g-1 at current density of 1 A g-1, which is much higher than undoped chitosan (67 F g-1). The capacitance retention of the carbon material was almost 97.2% after 5000 cycles at current density of 1 A g-1. With such improved electrochemical performance, the nitrogen/sulfur-codoped carbon material may have promising potential for use in energy-storage electrodes of supercapacitors.

Fabrication of 3-D nanodimensioned electric double layer capacitor structures using block copolymer templates.

PubMed

Rasappa, Sozaraj; Borah, Dipu; Senthamaraikannan, Ramsankar; Faulkner, Colm C; Holmes, Justin D; Morris, Michael A

2014-07-01

The need for materials for high energy storage has led to very significant research in supercapacitor systems. These can exhibit electrical double layer phenomena and capacitances up to hundreds of F/g. Here, we demonstrate a new supercapacitor fabrication methodology based around the microphase separation of PS-b-PMMA which has been used to prepare copper nanoelectrodes of dimension -13 nm. These structures provide excellent capacitive performance with a maximum specific capacitance of -836 F/g for a current density of 8.06 A/g at a discharge current as high as 75 mA. The excellent performance is due to a high surface area: volume ratio. We suggest that this highly novel, easily fabricated structure might have a number of important applications.

Capacitively Coupled Resistivity Survey of Selected Irrigation Canals Within the North Platte River Valley, Western Nebraska and Eastern Wyoming, 2004 and 2007-2009

USGS Publications Warehouse

Burton, Bethany L.; Johnson, Michaela R.; Vrabel, Joseph; Imig, Brian H.; Payne, Jason; Tompkins, Ryan E.

2009-01-01

Due to water resources of portions of the North Platte River basin being designated as over-appropriated by the State of Nebraska Department of Natural Resources (DNR), the North Platte Natural Resources District (NPNRD), in cooperation with the DNR, is developing an Integrated Management Plan (IMP) for groundwater and surface water in the NPNRD. As part of the IMP, a three-dimensional numerical finite difference groundwater-flow model is being developed to evaluate the effectiveness of using leakage of water from selected irrigation canal systems to manage groundwater recharge. To determine the relative leakage potential of the upper 8 m of the selected irrigation canals within the North Platte River valley in western Nebraska and eastern Wyoming, the U.S. Geological Survey performed a land-based capacitively coupled (CC) resistivity survey along nearly 630 km of 13 canals and 2 laterals in 2004 and from 2007 to 2009. These 13 canals were selected from the 27 irrigation canals in the North Platte valley due to their location, size, irrigated area, and relation to the active North Platte valley flood plain and related paleochannels and terrace deposits where most of the saturated thickness in the alluvium exists. The resistivity data were then compared to continuous cores at 62 test holes down to a maximum depth of 8 m. Borehole electrical conductivity (EC) measurements at 36 of those test holes were done to correlate resistivity values with grain sizes in order to determine potential vertical leakage along the canals as recharge to the underlying alluvial aquifer. The data acquired in 2004, as well as the 25 test hole cores from 2004, are presented elsewhere. These data were reprocessed using the same updated processing and inversion algorithms used on the 2007 through 2009 datasets, providing a consistent and complete dataset for all collection periods. Thirty-seven test hole cores and borehole electrical conductivity measurements were acquired based on the 2008 data. This report presents comparisons between the CC resistivity data and results from the 37 test holes and includes all binned and inverted CC resistivity datasets from all four years as well as the EC log data for the 37 test holes acquired in 2008 and 2009. The information gained from these data can help State and local water managers and scientists better understand the characteristics of the shallow subsurface underlying the irrigation canals so that the water resources can be managed more effectively.

2017 NEPP Tasks Update for Ceramic and Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2017-01-01

This presentation gives an overview of current NEPP tasks on ceramic and tantalum capacitors and plans for the future. It includes tasks on leakage currents, gas generation and case deformation in wet tantalum capacitors; ESR degradation and acceleration factors in MnO2 and polymer cathode capacitors. Preliminary results on the effect of moisture on degradation of reverse currents in MnO2 tantalum capacitors are discussed. Latest results on mechanical characteristics of MLCCs and modeling of degradation of leakage currents in BME capacitors with defects are also presented.

Carbon nanotube feedback-gate field-effect transistor: suppressing current leakage and increasing on/off ratio.

PubMed

Qiu, Chenguang; Zhang, Zhiyong; Zhong, Donglai; Si, Jia; Yang, Yingjun; Peng, Lian-Mao

2015-01-27

Field-effect transistors (FETs) based on moderate or large diameter carbon nanotubes (CNTs) usually suffer from ambipolar behavior, large off-state current and small current on/off ratio, which are highly undesirable for digital electronics. To overcome these problems, a feedback-gate (FBG) FET structure is designed and tested. This FBG FET differs from normal top-gate FET by an extra feedback-gate, which is connected directly to the drain electrode of the FET. It is demonstrated that a FBG FET based on a semiconducting CNT with a diameter of 1.5 nm may exhibit low off-state current of about 1 × 10(-13) A, high current on/off ratio of larger than 1 × 10(8), negligible drain-induced off-state leakage current, and good subthreshold swing of 75 mV/DEC even at large source-drain bias and room temperature. The FBG structure is promising for CNT FETs to meet the standard for low-static-power logic electronics applications, and could also be utilized for building FETs using other small band gap semiconductors to suppress leakage current.

Direct observation of the leakage current in epitaxial diamond Schottky barrier devices by conductive-probe atomic force microscopy and Raman imaging

NASA Astrophysics Data System (ADS)

Alvarez, J.; Boutchich, M.; Kleider, J. P.; Teraji, T.; Koide, Y.

2014-09-01

The origin of the high leakage current measured in several vertical-type diamond Schottky devices is conjointly investigated by conducting probe atomic force microscopy and confocal micro-Raman/photoluminescence imaging analysis. Local areas characterized by a strong decrease of the local resistance (5-6 orders of magnitude drop) with respect to their close surrounding have been identified in several different regions of the sample surface. The same local areas, also referenced as electrical hot-spots, reveal a slightly constrained diamond lattice and three dominant Raman bands in the low-wavenumber region (590, 914 and 1040 cm-1). These latter bands are usually assigned to the vibrational modes involving boron impurities and its possible complexes that can electrically act as traps for charge carriers. Local current-voltage measurements performed at the hot-spots point out a trap-filled-limited current as the main conduction mechanism favouring the leakage current in the Schottky devices.

On Using the Volatile Mem-Capacitive Effect of TiO2 Resistive Random Access Memory to Mimic the Synaptic Forgetting Process

NASA Astrophysics Data System (ADS)

Sarkar, Biplab; Mills, Steven; Lee, Bongmook; Pitts, W. Shepherd; Misra, Veena; Franzon, Paul D.

2018-02-01

In this work, we report on mimicking the synaptic forgetting process using the volatile mem-capacitive effect of a resistive random access memory (RRAM). TiO2 dielectric, which is known to show volatile memory operations due to migration of inherent oxygen vacancies, was used to achieve the volatile mem-capacitive effect. By placing the volatile RRAM candidate along with SiO2 at the gate of a MOS capacitor, a volatile capacitance change resembling the forgetting nature of a human brain is demonstrated. Furthermore, the memory operation in the MOS capacitor does not require a current flow through the gate dielectric indicating the feasibility of obtaining low power memory operations. Thus, the mem-capacitive effect of volatile RRAM candidates can be attractive to the future neuromorphic systems for implementing the forgetting process of a human brain.

Ultrahigh volumetric capacitance and cyclic stability of fluorine and nitrogen co-doped carbon microspheres

NASA Astrophysics Data System (ADS)

Zhou, Junshuang; Lian, Jie; Hou, Li; Zhang, Junchuan; Gou, Huiyang; Xia, Meirong; Zhao, Yufeng; Strobel, Timothy A.; Tao, Lu; Gao, Faming

2015-09-01

Highly porous nanostructures with large surface areas are typically employed for electrical double-layer capacitors to improve gravimetric energy storage capacity; however, high surface area carbon-based electrodes result in poor volumetric capacitance because of the low packing density of porous materials. Here, we demonstrate ultrahigh volumetric capacitance of 521 F cm-3 in aqueous electrolytes for non-porous carbon microsphere electrodes co-doped with fluorine and nitrogen synthesized by low-temperature solvothermal route, rivaling expensive RuO2 or MnO2 pseudo-capacitors. The new electrodes also exhibit excellent cyclic stability without capacitance loss after 10,000 cycles in both acidic and basic electrolytes at a high charge current of 5 A g-1. This work provides a new approach for designing high-performance electrodes with exceptional volumetric capacitance with high mass loadings and charge rates for long-lived electrochemical energy storage systems.

Quantum decrease of capacitance in a nanometer-sized tunnel junction

NASA Astrophysics Data System (ADS)

Untiedt, C.; Saenz, G.; Olivera, B.; Corso, M.; Sabater, C.; Pascual, J. I.

2013-03-01

We have studied the capacitance of the tunnel junction defined by the tip and sample of a Scanning Tunnelling Microscope through the measurement of the electrostatic forces and impedance of the junction. A decrease of the capacitance when a tunnel current is present has shown to be a more general phenomenon as previously reported in other systems. On another hand, an unexpected reduction of the capacitance is also observed when increasing the applied voltage above the work function energy of the electrodes to the Field Emission (FE) regime, and the decrease of capacitance due to a single FE-Resonance has been characterized. All these effects should be considered when doing measurements of the electronic characteristics of nanometer-sized electronic devices and have been neglected up to date. Spanish government (FIS2010-21883-C02-01, CONSOLIDER CSD2007-0010), Comunidad Valenciana (ACOMP/2012/127 and PROMETEO/2012/011)

Layered Structural Co-Based MOF with Conductive Network Frames as a New Supercapacitor Electrode.

PubMed

Yang, Jie; Ma, Zhihua; Gao, Weixue; Wei, Mingdeng

2017-01-12

Layered structural Co-MOF nanosheets were synthesized and then used as an electrode material for supercapacitors for the first time. This material exhibited a high specific capacitance, a good rate capability, and an excellent cycling stability. A maximum capacitance of 2564 F g -1 can be achieved at a current density of 1 Ag -1 . Moreover, the capacitance retention can be kept at 95.8 % respectively of its initial value after 3000 cycles. To the best of our knowledge, both the specific capacitance and the capacitance retention were the highest values reported for MOF materials as supercapacitor electrodes until now. Such a high supercapacitive performance might be attributed to the intrinsic characteristics of this kind of Co-MOF material, including its layered structure, conductive network frame, and thin nanosheet. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation on VOX/CNTS Nanocomposites Act as Electrode of Supercapacitors

NASA Astrophysics Data System (ADS)

Zhu, Quanyao; Li, Zhaolong; Zhang, Xiaoyan; Huang, Shengnan; Yu, Yue; Chen, Wen; Zakharova, Galina S.

2013-07-01

The VOx/CNTs nanocomposites were synthesized by the hydrothermal method. The structure and morphologies of the nanocomposites were characteristic by XRD, SEM and TEM. The electrochemical properties of the nanocomposites were explored by cyclic voltammetry, constant current charge/discharge testing and electrochemical impedance spectroscopy in 1M KNO3 aqueous solution. The results showed that the nanocomposites perform characteristics of electrical both double-layer capacitance and pseudocapacitance. The specific capacitances were 136.5F/g, when the current density was 0.15A/g.

An assessment of the Space Station Freedom program's leakage current requirement

NASA Technical Reports Server (NTRS)

Nagy, Michael

1991-01-01

The Space Station Freedom Program requires leakage currents to be limited to less than human perception level, which NASA presently defines as 5 mA for dc. The origin of this value is traced, and the literature for other dc perception threshold standards is surveyed. It is shown that while many varying standards exist, very little experimental data is available to support them.

Influence of vanadium doping on the electrochemical performance of nickel oxide in supercapacitors.

PubMed

Park, Hae Woong; Na, Byung-Ki; Cho, Byung Won; Park, Sun-Min; Roh, Kwang Chul

2013-10-28

In this study, V-doped NiO materials were prepared by simple coprecipitation and thermal decomposition, and the effect of the vanadium content on the morphology, structural properties, electrochemical behavior, and cycling stability of NiO upon oxidation and reduction was analyzed for supercapacitor applications. The results show an improvement in the capacitive characteristics of the V-doped NiO, including increases in the specific capacitance after the addition of just 1.0, 2.0, and 4.0 at% V. All VxNi1-xO electrodes (x = 0.01, 0.02, 0.04) exhibited higher specific capacitances of 371.2, 365.7, and 386.2 F g(-1) than that of pure NiO (303.2 F g(-1)) at a current density of 2 A g(-1) after 500 cycles, respectively. The V0.01Ni0.99O electrode showed good capacitance retention of 73.5% at a current density of 2 A g(-1) for more than 500 cycles in a cycling test. Importantly, the rate capability of the V0.01Ni0.99O electrode was maintained at about 84.7% as discharge current density was increased from 0.5 A g(-1) to 4 A g(-1).

An asymmetric supercapacitor with ultrahigh energy density based on nickle cobalt sulfide nanocluster anchoring multi-wall carbon nanotubes hybrid

NASA Astrophysics Data System (ADS)

Wen, Ping; Fan, Mingjin; Yang, Desuo; Wang, Yan; Cheng, Hualei; Wang, Jinqing

2016-07-01

The development of novel electrode materials with high energy density and long cycling life is critical to realize electrochemical capacitive energy storage for practical applications. In this paper, the hybrids of nickle cobalt sulfide/multi-wall carbon nanotubes (NiCo2S4/MWCNTs) with different contents of MWCNTs are prepared using a facile one-pot solvothermal reaction. As novel active materials for supercapacitors, the electrochemistry tests show that the hybrid of NiCo2S4/MWCNTs-5 is able to deliver a high specific capacitance of 2080 F g-1 at the current density of 1 A g-1, even superior rate capability of 61% capacitance retention after a 20-fold increase in current densities, when the content of MWCNTs is up to 5%. More importantly, an asymmetric supercapacitor assembled by NiCo2S4/MWCNTs-5 as positive electrode and reduced graphene oxide (rGO) as negative electrode delivers a high energy density of 51.8 Wh Kg-1 at a power density of 865 W kg-1, and 85.7% of its initial capacitance is retained at the current density of 4 A g-1 after 5000 charge-discharge cycles, exhibiting potential prospect for practical applications.

Conductive polymer foam surface improves the performance of a capacitive EEG electrode.

PubMed

Baek, Hyun Jae; Lee, Hong Ji; Lim, Yong Gyu; Park, Kwang Suk

2012-12-01

In this paper, a new conductive polymer foam-surfaced electrode was proposed for use as a capacitive EEG electrode for nonintrusive EEG measurements in out-of-hospital environments. The current capacitive electrode has a rigid surface that produces an undefined contact area due to its stiffness, which renders it unable to conform to head curvature and locally isolates hairs between the electrode surface and scalp skin, making EEG measurement through hair difficult. In order to overcome this issue, a conductive polymer foam was applied to the capacitive electrode surface to provide a cushioning effect. This enabled EEG measurement through hair without any conductive contact with bare scalp skin. Experimental results showed that the new electrode provided lower electrode-skin impedance and higher voltage gains, signal-to-noise ratios, signal-to-error ratios, and correlation coefficients between EEGs measured by capacitive and conventional resistive methods compared to a conventional capacitive electrode. In addition, the new electrode could measure EEG signals, while the conventional capacitive electrode could not. We expect that the new electrode presented here can be easily installed in a hat or helmet to create a nonintrusive wearable EEG apparatus that does not make users look strange for real-world EEG applications.

Great improvement in pseudocapacitor properties of nickel hydroxide via simple gold deposition

NASA Astrophysics Data System (ADS)

Kim, Sun-I.; Thiyagarajan, Pradheep; Jang, Ji-Hyun

2014-09-01

In this letter, we report a facile approach to improve the capacitor properties of nickel hydroxide (Ni(OH)2) by simply coating gold nanoparticles (Au NPs) on the surface of Ni(OH)2. Au NP-deposited Ni(OH)2 (Au/Ni(OH)2) has been prepared by application of a conventional colloidal coating of Au NPs on the surface of 3D-Ni(OH)2 synthesized via a hydrothermal method. Compared with pristine Ni(OH)2, Au/Ni(OH)2 shows a 41% enhanced capacitance value, excellent rate capacitance behavior at high current density conditions, and greatly improved cycling stability for supercapacitor applications. The specific capacitance of Au/Ni(OH)2 reached 1927 F g-1 at 1 A g-1, which is close to the theoretical capacitance and retained 66% and 80% of the maximum value at a high current density of 20 A g-1 and 5000 cycles while that of pristine Ni(OH)2 was 1363 F g-1 and significantly decreased to 48% and 30%, respectively, under the same conditions. The outstanding performance of Au/Ni(OH)2 as a supercapacitor is attributed to the presence of metal Au NPs on the surface of semiconductor Ni(OH)2; this permits the creation of virtual 3D conducting networks via metal/semiconductor contact, which induces fast electron and ion transport by acting as a bridge between Ni(OH)2 nanostructures, thus eventually leading to significantly improved electrochemical capacitive behaviors, as confirmed by the EIS and I-V characteristic data.In this letter, we report a facile approach to improve the capacitor properties of nickel hydroxide (Ni(OH)2) by simply coating gold nanoparticles (Au NPs) on the surface of Ni(OH)2. Au NP-deposited Ni(OH)2 (Au/Ni(OH)2) has been prepared by application of a conventional colloidal coating of Au NPs on the surface of 3D-Ni(OH)2 synthesized via a hydrothermal method. Compared with pristine Ni(OH)2, Au/Ni(OH)2 shows a 41% enhanced capacitance value, excellent rate capacitance behavior at high current density conditions, and greatly improved cycling stability for supercapacitor applications. The specific capacitance of Au/Ni(OH)2 reached 1927 F g-1 at 1 A g-1, which is close to the theoretical capacitance and retained 66% and 80% of the maximum value at a high current density of 20 A g-1 and 5000 cycles while that of pristine Ni(OH)2 was 1363 F g-1 and significantly decreased to 48% and 30%, respectively, under the same conditions. The outstanding performance of Au/Ni(OH)2 as a supercapacitor is attributed to the presence of metal Au NPs on the surface of semiconductor Ni(OH)2; this permits the creation of virtual 3D conducting networks via metal/semiconductor contact, which induces fast electron and ion transport by acting as a bridge between Ni(OH)2 nanostructures, thus eventually leading to significantly improved electrochemical capacitive behaviors, as confirmed by the EIS and I-V characteristic data. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02204a

Investigation of defect-induced abnormal body current in fin field-effect-transistors

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

Liu, Kuan-Ju; Tsai, Jyun-Yu; Lu, Ying-Hsin

2015-08-24

This letter investigates the mechanism of abnormal body current at the linear region in n-channel high-k/metal gate stack fin field effect transistors. Unlike body current, which is generated by impact ionization at high drain voltages, abnormal body current was found to increase with decreasing drain voltages. Notably, the unusual body leakage only occurs in three-dimensional structure devices. Based on measurements under different operation conditions, the abnormal body current can be attributed to fin surface defect-induced leakage current, and the mechanism is electron tunneling to the fin via the defects, resulting in holes left at the body terminal.

The Electrical Double Layer and Its Structure

NASA Astrophysics Data System (ADS)

Stojek, Zbigniew

At any electrode immersed in an electrolyte solution, a specific interfacial region is formed. This region is called the double layer. The electrical properties of such a layer are important, since they significantly affect the electrochemical measurements. In an electrical circuit used to measure the current that flows at a particular working electrode, the double layer can be viewed as a capacitor. Figure I.1.1 depicts this situation where the electrochemical cell is represented by an electrical circuit and capacitor C d corresponds to the differential capacity of the double layer. To obtain a desired potential at the working electrodes, the double-layer capacitor must be first appropriately charged, which means that a capacitive current, not related to the reduction or oxidation of the substrates, flows in the electrical circuit. While this capacitive current carries some information concerning the double layer and its structure, and in some cases can be used for analytical purposes, in general, it interferes with electrochemical investigations. A variety of methods are used in electrochemistry to depress, isolate, or filter the capacitive current.

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.

Hysteresis free negative total gate capacitance in junctionless transistors

NASA Astrophysics Data System (ADS)

Gupta, Manish; Kranti, Abhinav

2017-09-01

In this work, we report on the hysteresis free impact ionization induced off-to-on transition while preserving sub-60 mV/decade Subthreshold swing (S-swing) using asymmetric mode operation in double gate silicon (Si) and germanium (Ge) junctionless (JL) transistor. It is shown that sub-60 mV/decade steep switching due to impact ionization implies a negative value of the total gate capacitance. The performance of asymmetric gate JL transistor is compared with symmetric gate operation of JL device, and the condition for hysteresis free current transition with a sub-60 mV/decade switching is analyzed through the product of current density (J) and electric field (E). It is shown that asymmetric gate operation limits the degree of impact ionization inherent in the semiconductor film to levels sufficient for negative total gate capacitance but lower than that required for the occurrence of hysteresis. The work highlights new viewpoints related to the suppression of hysteresis associated with steep switching JL transistors while maintaining S-swing within the range 6-15 mV/decade leading to the negative value of total gate capacitance.

Facile and environmentally friendly synthesis of ultrathin nickel hydroxide nanosheets with excellent supercapacitor performances

NASA Astrophysics Data System (ADS)

Hu, Xiaowei; Liu, Sheng; Li, Chenghui; Huang, Jiahao; Luv, Jixing; Xu, Pan; Liu, Jian; You, Xiao-Zeng

2016-06-01

In this article, we report a facile and environmentally friendly glutamic acid-assisted hydrothermal strategy for the preparation of ultrathin two-dimensional (2D) β-Ni(OH)2 nanosheets with a thickness of about 2 nm, which exhibit a maximum specific capacitance of 2537.4 F g-1 at a current density of 1 A g-1, even at 10 A g-1, the specific capacitance is still maintained at 2290.0 F g-1 with 77.6% retention after 3000 cycles.In this article, we report a facile and environmentally friendly glutamic acid-assisted hydrothermal strategy for the preparation of ultrathin two-dimensional (2D) β-Ni(OH)2 nanosheets with a thickness of about 2 nm, which exhibit a maximum specific capacitance of 2537.4 F g-1 at a current density of 1 A g-1, even at 10 A g-1, the specific capacitance is still maintained at 2290.0 F g-1 with 77.6% retention after 3000 cycles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02912d

Three-Dimensional Honeycomb-Like Porous Carbon with Both Interconnected Hierarchical Porosity and Nitrogen Self-Doping from Cotton Seed Husk for Supercapacitor Electrode.

PubMed

Chen, Hui; Wang, Gang; Chen, Long; Dai, Bin; Yu, Feng

2018-06-08

Hierarchical porous structures with surface nitrogen-doped porous carbon are current research topics of interest for high performance supercapacitor electrode materials. Herein, a three-dimensional (3D) honeycomb-like porous carbon with interconnected hierarchical porosity and nitrogen self-doping was synthesized by simple and cost-efficient one-step KOH activation from waste cottonseed husk (a-CSHs). The obtained a-CSHs possessed hierarchical micro-, meso-, and macro-pores, a high specific surface area of 1694.1 m²/g, 3D architecture, and abundant self N-doping. Owing to these distinct features, a-CSHs delivered high specific capacitances of 238 F/g and 200 F/g at current densities of 0.5 A/g and 20 A/g, respectively, in a 6 mol/L KOH electrolyte, demonstrating good capacitance retention of 84%. The assembled a-CSHs-based symmetric supercapacitor also displayed high specific capacitance of 52 F/g at 0.5 A/g, with an energy density of 10.4 Wh/Kg at 300 W/Kg, and 91% capacitance retention after 5000 cycles at 10 A/g.

Hierarchical MoS2 nanowires/NiCo2O4 nanosheets supported on Ni foam for high-performance asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wen, Shiyang; Liu, Yu; Zhu, Fangfang; Shao, Rong; Xu, Wei

2018-01-01

The hierarchical MoS2 nanowires/NiCo2O4 nanosheets (MS/NCO) supercapacitor electrode materials supported on Ni foam were synthesized by a two-step hydrothermal method. The capacitance was investigated by using various electrochemical methods including cyclic voltammetry, constant-current galvanostatic charge/discharge curves and electrochemical impedance spectroscopy. The MS/NCO networks show 7 times more capacitance (7.1 F cm-2) than pure NiCo2O4 nanosheets by CV at a scan rate of 2 mV s-1. The specific capacitance of the assembled MS/NCO//active carbon (AC) asymmetric supercapacitor could reach up to 51.7 F g-1 at a current density of 1.5 A g-1. Also, the maximum energy density of 18.4 W h kg-1 at a power density of 1200.2 W kg-1 was achieved, with 98.2% specific capacitance retention after 8000 cycles. These exciting results exhibit potential application in developing energy storage devices with high energy density and high power density.

Nonstoichiometric Solution-Processed BaTiO₃ Film for Gate Insulator Applications.

PubMed

Lau, Joyce; Kim, Sangsub; Kim, Hyunki; Koo, Kwangjun; Lee, Jaeseob; Kim, Sangsoo; Choi, Byoungdeog

2018-09-01

Solution processed barium titanate (BTO) was used to fabricate an Al/BaTiO3/p-Si metal-insulator-semiconductor (MIS) structure, which was used as a gate insulator. Changes in the electrical characteristics of the film were investigated as a function of the film thickness and post deposition annealing conditions. Our results showed that a thickness of 5 layers and an annealing temperature of 650 °C produced the highest electrical performance. BaxTi1-xO3 was altered at x = 0.10, 0.30, 0.50, 0.70, 0.90, and 1.0 to investigate changes in the electrical properties as a function of composition. The highest dielectric constant of 87 was obtained for x = 0.10, while the leakage current density was suppressed as Ba content increased. The lowest leakage current density was 1.34×10-10 A/cm2, which was observed at x = 0.90. The leakage current was related to the resistivity of the film, the interface states, and grain densification. Space charge limited current (SCLC) was the dominant leakage mechanism in BTO films based on leakage current analysis. Although a Ba content of x = 0.90 had the highest trap density, the traps were mainly composed of Ti-vacancies, which acted as strong electron traps and affected the film resistivity. A secondary phase, Ba2TiO4, which was observed in cases of excess Ba, acted as a grain refiner and provided faster densification of the film during the thermal process. The absence of a secondary phase in BaO (x = 1.0) led to the formation of many interface states and degradation in the electrical properties. Overall, the insulator properties of BTO were improved when the composition ratio was x = 0.90.

Structural, electrical, and optical characterization of coalescent p-n GaN nanowires grown by molecular beam epitaxy

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

Kolkovsky, Vl.; Zytkiewicz, Z. R.; Sobanska, M.

2015-12-14

The electrical, structural, and optical properties of coalescent p-n GaN nanowires (NWs) grown by molecular beam epitaxy on Si (111) substrate are investigated. From photoluminescence measurements the full width at half maximum of bound exciton peaks AX and DA is found as 1.3 and 1.2 meV, respectively. These values are lower than those reported previously in the literature. The current-voltage characteristics show the rectification ratio of about 10{sup 2} and the leakage current of about 10{sup −4} A/cm{sup 2} at room temperature. We demonstrate that the thermionic mechanism is not dominant in these samples and spatial inhomogeneties and tunneling processes through amore » ∼2 nm thick SiN{sub x} layer between GaN and Si could be responsible for deviation from the ideal diode behavior. The free carrier concentration in GaN NWs determined by capacitance-voltage measurements is about 4 × 10{sup 15 }cm{sup −3}. Two deep levels (H190 and E250) are found in the structures. We attribute H190 to an extended defect located at the interface between the substrate and the SiN{sub x} interlayer or near the sidewalls at the bottom of the NWs, whereas E250 is tentatively assigned to a gallium-vacancy- or nitrogen interstitials-related defect.« less

Investigation and statistical modeling of InAs-based double gate tunnel FETs for RF performance enhancement

NASA Astrophysics Data System (ADS)

Poorvasha, S.; Lakshmi, B.

2018-05-01

In this paper, RF performance analysis of InAs-based double gate (DG) tunnel field effect transistors (TFETs) is investigated in both qualitative and quantitative fashion. This investigation is carried out by varying the geometrical and doping parameters of TFETs to extract various RF parameters, unity gain cut-off frequency (f t), maximum oscillation frequency (f max), intrinsic gain and admittance (Y) parameters. An asymmetric gate oxide is introduced in the gate-drain overlap and compared with that of DG TFETs. Higher ON-current (I ON) of about 0.2 mA and less leakage current (I OFF) of 29 fA is achieved for DG TFET with gate-drain overlap. Due to increase in transconductance (g m), higher f t and intrinsic gain is attained for DG TFET with gate-drain overlap. Higher f max of 985 GHz is obtained for drain doping of 5 × 1017 cm‑3 because of the reduced gate-drain capacitance (C gd) with DG TFET with gate-drain overlap. In terms of Y-parameters, gate oxide thickness variation offers better performance due to the reduced values of C gd. A second order numerical polynomial model is generated for all the RF responses as a function of geometrical and doping parameters. The simulation results are compared with this numerical model where the predicted values match with the simulated values. Project supported by the Department of Science and Technology, Government of India under SERB Scheme (No. SERB/F/2660).

Active shunt capacitance cancelling oscillator circuit

DOEpatents

Wessendorf, Kurt O.

2003-09-23

An oscillator circuit is disclosed which can be used to produce oscillation using a piezoelectric crystal, with a frequency of oscillation being largely independent of any shunt capacitance associated with the crystal (i.e. due to electrodes on the surfaces of the crystal and due to packaging and wiring for the crystal). The oscillator circuit is based on a tuned gain stage which operates the crystal at a frequency, f, near a series resonance frequency, f.sub.S. The oscillator circuit further includes a compensation circuit that supplies all the ac current flow through the shunt resistance associated with the crystal so that this ac current need not be supplied by the tuned gain stage. The compensation circuit uses a current mirror to provide the ac current flow based on the current flow through a reference capacitor that is equivalent to the shunt capacitance associated with the crystal. The oscillator circuit has applications for driving piezoelectric crystals for sensing of viscous, fluid or solid media by detecting a change in the frequency of oscillation of the crystal and a resonator loss which occur from contact of an exposed surface of the crystal by the viscous, fluid or solid media.

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.

A porous carbon material from pyrolysis of fructus cannabis’s shells for supercapacitor electrode application

NASA Astrophysics Data System (ADS)

Li, Kai; Zhang, Wei-Bin; Zhao, Zhi-Yun; Zhao, Yue; Chen, Xi-Wen; Kong, Ling-Bin

2018-02-01

The porous carbon material is obtained via pyrolysis and activation of fructus cannabis’s shells, an easy-to-get biomass source, and is used as an active electrode material for supercapacitors. The obtained carbon exhibit a high specific surface area of 2389 m2 g-1. And the result of x-ray photoelectron spectroscopy (XPS) shows that the obtained porous carbon possess numerous oxygen groups, which can facilitate the wettability of the electrode. The prepared porous carbon also exhibit remarkable electrochemical properties, such as high specific capacitance of 357 F g-1 at a current density of 0.5 A g-1 in 6 mol L-1 aqueous KOH electrolyte, good rate capability of 77% capacitance retention as the current density increase from 0.5 A g-1 to 10 A g-1. In addition, it also presents a superior cycling stability of 100% capacitance retention after 10 000 cycles at the current density of 1 A g-1.

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.

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.

Microstructural, electrical and frequency-dependent properties of Au/p-Cu2ZnSnS4/n-GaN heterojunction.

PubMed

Rajagopal Reddy, V; Janardhanam, V; Won, Jonghan; Choi, Chel-Jong

2017-08-01

An Au/Cu 2 ZnSnS 4 (CZTS)/n-GaN heterojunction (HJ) is fabricated with a CZTS interlayer and probed its chemical states, structural, electrical and frequency-dependent characteristics by XPS, TEM, I-V and C-V measurements. XPS and TEM results confirmed that the CZTS films are formed on the n-GaN surface. The band gap of deposited CZTS film is found to be 1.55eV. The electrical properties of HJ correlated with the Au/n-GaN Schottky junction (SJ). The Au/CZTS/n-GaN HJ reveals a good rectification nature with high barrier height (0.82eV) compared to the Au/n-GaN SJ (0.69eV), which suggests the barrier height is influenced by the CZTS interlayer. The barrier height values assessed by I-V, Cheung's and Norde functions are closely matched with one other, thus the methods used here are reliable and valid. The extracted interface state density (N SS ) of Au/CZTS/n-GaN HJ is lower compared to the Au/n-GaN SJ that suggests the CZTS interlayer plays an important role in the reduction of N SS . Moreover, the capacitance-frequency (C-f) and conductance-frequency (G-f) characteristics of SJ and HJ are measured in the range of 1kHz-1MHz, and found that the capacitance and conductance strappingly dependent on frequency. It is found that the N SS estimated from C-f and G-f characteristics is lower compared to those estimated from I-V characteristics. Analysis confirmed that Poole-Frenkel emission dominates the reverse leakage current in both SJ and HJ, probably related to the structural defects and trap levels in the CZTS interlayer. Copyright © 2017 Elsevier Inc. All rights reserved.

Noise in CdZnTe detectors

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

Luke, P. N.; Amman, M.; Lee J. S.

2000-10-10

Noise in CdZnTe devices with different electrode configurations was investigated. Measurements on devices with guard-ring electrode structures showed that surface leakage current does not produce any significant noise. The parallel white noise component of the devices appeared to be generated by the bulk current alone, even though the surface current was substantially higher. This implies that reducing the surface leakage current of a CdZnTe detector may not necessarily result in a significant improvement in noise performance. The noise generated by the bulk current is also observed to be below full shot noise. This partial suppression of shot noise may bemore » the result of Coulomb interaction between carriers or carrier trapping. Devices with coplanar strip electrodes were observed to produce a 1/f noise term at the preamplifier output. Higher levels of this 1/f noise were observed with decreasing gap widths between electrodes. The level of this 1/f noise appeared to be independent of bias voltage and leakage current but was substantially reduced after certain surface treatments.« less

Conduction mechanism of leakage current due to the traps in ZrO2 thin film

NASA Astrophysics Data System (ADS)

Seo, Yohan; Lee, Sangyouk; An, Ilsin; Song, Chulgi; Jeong, Heejun

2009-11-01

In this work, a metal-oxide-semiconductor capacitor with zirconium oxide (ZrO2) gate dielectric was fabricated by an atomic layer deposition (ALD) technique and the leakage current characteristics under negative bias were studied. From the result of current-voltage curves there are two possible conduction mechanisms to explain the leakage current in the ZrO2 thin film. The dominant mechanism is the space charge limited conduction in the high-electric field region (1.5-5.0 MV cm-1) while the trap-assisted tunneling due to the existence of traps is prevailed in the low-electric field region (0.8-1.5 MV cm-1). Conduction caused by the trap-assisted tunneling is found from the experimental results of a weak temperature dependence of current, and the trap barrier height is obtained. The space charge limited conduction is evidenced, for different temperatures, by Child's law dependence of current density versus voltage. Child's law dependence can be explained by considering a single discrete trapping level and we can obtain the activation energy of 0.22 eV.

Porous NiCo2O4 nanosheets/reduced graphene oxide composite: facile synthesis and excellent capacitive performance for supercapacitors.

PubMed

Ma, Lianbo; Shen, Xiaoping; Ji, Zhenyuan; Cai, Xiaoqing; Zhu, Guoxing; Chen, Kangmin

2015-02-15

A composite with porous NiCo2O4 nanosheets attached on reduced graphene oxide (RGO) sheets is synthesized through a facile solution-based method combined with a simple thermal annealing process. The capacitive performances of the as-prepared NiCo2O4/RGO (NCG) composites as electrode materials are investigated. It is found that the NCG composites exhibit a high specific capacitance up to 1186.3 F g(-1) at the current density of 0.5 A g(-1), and superior cycling stability with about 97% of the initial capacitance after 100 cycles. The greatly enhanced capacitive performance of the NCG electrode can be attributed to the existence of RGO support, which serves as both conductive channels and active interface. The approach used in the synthesis provides a facile route for preparing graphene-binary metal oxide electrode materials. The remarkable capacitive performance of NCG composites will undoubtedly make them be attractive for high performance energy storage applications. Copyright © 2014 Elsevier Inc. All rights reserved.

Surface leakage current in 12.5  μm long-wavelength HgCdTe infrared photodiode arrays.

PubMed

Qiu, Weicheng; Hu, Weida; Lin, Chun; Chen, Xiaoshuang; Lu, Wei

2016-02-15

Long-wavelength (especially >12  μm) focal plane array (FPA) infrared detection is the cutting edge technique for third-generation infrared remote sensing. However, dark currents, which are very sensitive to the growth of small Cd composition HgCdTe, strongly limits the performance of long wavelength HgCdTe photodiode arrays in FPAs. In this Letter, 12.5 μm long-wavelength Hg_1-xCd_xTe (x≈0.219) infrared photodiode arrays are reported. The variable-area and variable-temperature electrical characteristics of the long-wavelength infrared photodiodes are measured. The characteristics of the extracted zero-bias resistance-area product (l/R₀A) varying with the perimeter-to-area (P/A) ratio clearly show that surface leakage current mechanisms severely limit the overall device performance. A sophisticated model has been developed for investigating the leakage current mechanism in the photodiodes. Modeling of temperature-dependent I-V characteristic indicates that the trap-assisted tunneling effect dominates the dark current at 50 K resulting in nonuniformities in the arrays. The extracted trap density, approximately 10¹³-10¹⁴  cm^-3, with an ionized energy of 30 meV is determined by simulation. The work described in this Letter provides the basic mechanisms for a better understanding of the leakage current mechanism for long-wavelength (>12  μm) HgCdTe infrared photodiode arrays.

Ultimate scaling of TiN/ZrO2/TiN capacitors: Leakage currents and limitations due to electrode roughness

NASA Astrophysics Data System (ADS)

Jegert, Gunther; Kersch, Alfred; Weinreich, Wenke; Lugli, Paolo

2011-01-01

In this paper, we investigate the influence of electrode roughness on the leakage current in TiN/high-κ ZrO2/TiN (TZT) thin-film capacitors which are used in dynamic random access memory cells. Based on a microscopic transport model, which is expanded to incorporate electrode roughness, we assess the ultimate scaling potential of TZT capacitors in terms of equivalent oxide thickness, film smoothness, thickness fluctuations, defect density and distribution, and conduction band offset (CBO). The model is based on three-dimensional, fully self-consistent, kinetic Monte Carlo transport simulations. Tunneling transport in the bandgap of the dielectric is treated, which includes defect-assisted transport mechanisms. Electrode roughness is described in the framework of fractal geometry. While the short-range roughness of the electrodes is found not to influence significantly the leakage current, thickness fluctuations of the dielectric have a major impact. For thinner dielectric films they cause a transformation of the dominant transport mechanism from Poole-Frenkel conduction to trap-assisted tunneling. Consequently, the sensitivity of the leakage current on electrode roughness drastically increases on downscaling. Based on the simulations, optimization of the CBO is suggested as the most viable strategy to extend the scalability of TZT capacitors over the next chip generations.

Effects of Combined Stressing on the Electrical Properties of Film and Ceramic Capacitors

NASA Technical Reports Server (NTRS)

Overton, Eric; Hammoud, Ahmad N.; Baumann, Eric D.; Myers, Ira T.

1994-01-01

Advanced power systems which generate, control, and distribute electrical power to many large loads are a requirement for future space exploration missions. The development of high temperature insulating materials and power components constitute a key element in systems which are lightweight, efficient, and are capable of surviving the hostile space environment. In previous work, experiments were carried out to evaluate film and ceramic capacitors for potential use in high temperature applications. The effects of thermal stressing, in air and without electrical bias, on the electrical properties of the capacitors as a function of thermal aging up to 12 weeks were determined. In this work, the combined effects of thermal aging and electrical stresses on the properties of teflon film and ceramic power capacitors were examined. The ceramic capacitors were thermally aged for 35 weeks and the teflon capacitors for 15 weeks at 200 C under full electrical bias and were characterized, on a weekly basis, in terms of their capacitance stability and electrical loss in the frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also obtained. The results obtained represent the influence that short-term thermal aging and electrical bias have on the electrical properties of the power capacitors characterized.

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

Electrical characteristics and thermal stability of n+ polycrystalline- Si/ZrO2/SiO2/Si metal-oxide-semiconductor capacitors

NASA Astrophysics Data System (ADS)

Lim, Kwan-Yong; Park, Dae-Gyu; Cho, Heung-Jae; Kim, Joong-Jung; Yang, Jun-Mo; Ii, Choi-Sang; Yeo, In-Seok; Park, Jin Won

2002-01-01

We have investigated the thermal stability of n+ polycrystalline-Si(poly-Si)/ZrO2(50-140 Å)/SiO2(7 Å)/p-Si metal-oxide-semiconductor (MOS) capacitors via electrical and material characterization. The ZrO2 gate dielectric was prepared by atomic layer chemical vapor deposition using ZrCl4 and H2O vapor. Capacitance-voltage hysteresis as small as ˜12 mV with the flatband voltage of -0.5 V and the interface trap density of ˜5×1010cm-2 eV-1 were attained with activation anneal at 750 °C. A high level of gate leakage current was observed at the activation temperatures over 750 °C and attributed to the interfacial reaction of poly-Si and ZrO2 during the poly-Si deposition and the following high temperature anneal. Because of this, the ZrO2 gate dielectric is incompatible with the conventional poly-Si gate process. In the MOS capacitors having a smaller active area (<50×50 μm2), fortunately, the electrical degradation by further severe silicidation does not occur up to an 800 °C anneal in N2 for 30 min.

Temperature-Dependent Electrical Properties and Carrier Transport Mechanisms of TMAH-Treated Ni/Au/Al2O3/GaN MIS Diode

NASA Astrophysics Data System (ADS)

Reddy, M. Siva Pratap; Puneetha, Peddathimula; Reddy, V. Rajagopal; Lee, Jung-Hee; Jeong, Seong-Hoon; Park, Chinho

2016-11-01

The temperature-dependent electrical properties and carrier transport mechanisms of tetramethylammonium hydroxide (TMAH)-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes have been investigated by current-voltage ( I- V) and capacitance-voltage ( C- V) measurements. The experimental results reveal that the barrier height ( I- V) increases whereas the ideality factor decreases with increasing temperature. The TMAH-treated Ni/Au/Al2O3/GaN MIS diode showed nonideal behaviors which indicate the presence of a nonuniform distribution of interface states ( N SS) and effect of series resistance ( R S). The obtained R S and N SS were found to decrease with increasing temperature. Furthermore, it was found that different transport mechanisms dominated in the TMAH-treated Ni/Au/Al2O3/GaN MIS diode. At 150 K to 250 K, Poole-Frenkel emission (PFE) was found to be responsible for the reverse leakage, while Schottky emission (SE) was the dominant mechanism at high electric fields in the temperature range from 300 K to 400 K. Feasible energy band diagrams and possible carrier transport mechanisms for the TMAH-treated Ni/Au/Al2O3/GaN MIS diode are discussed based on PFE and SE.

Device considerations and characterizations of pre and post fabricated GaAs based pHEMTs using multilayer 3D MMIC technology

NASA Astrophysics Data System (ADS)

Alim, Mohammad A.; Ali, Mayahsa M.; Haris, Norshakila; Kyabaggu, Peter B. K.; Rezazadeh, Ali A.

2017-05-01

This study focuses on the characterization of two 0.5 μm gate-length double heterojunction AlGaAs/InGaAs/GaAs pHEMTs using pre and post fabricated vertical oriented multilayer 3D monolithic microwave integrated (MMIC) circuit technology. The effects of the presence of 3D components above the active layer were accomplished by means of capacitance-voltage measurement, on-wafer DC and S-parameter measurements and two-tone intermodulation distortion measurement. The barrier height, donor concentration in the barrier layer, existing two-dimensional electron gas, output current, off and on state leakage, transconductance, cut-off frequency, small signal model parameters, gain, minimum noise figures and nonlinear distortion behavior reveals no significant performance degradation. Furthermore the fundamental device properties such as the depletion depth d, the sheet charge densities of the 2-DEG, n s, filed dependent mobility, μ, and the effective carrier velocity, v eff is not much affected due to multilayer processing. Less than 5% changes in magnitude of the device parameters are realized between the pre and post fabricated multilayer 3D MMIC technology. These effective comparisons of the both device are useful for future designs and optimizations of multilayer vertical stacked 3D MMICs.

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.

Design of a Multi-Channel Front-End Readout ASIC With Low Noise and Large Dynamic Input Range for APD-Based PET Imaging

NASA Astrophysics Data System (ADS)

Fang, X. C.; Hu-Guo, Ch.; Ollivier-Henry, N.; Brasse, D.; Hu, Y.

2010-06-01

This paper represents the design of a low-noise, wide band multi-channel readout integrated circuit (IC) used as front end readout electronics of avalanche photo diodes (APD) dedicated to a small animal positron emission tomography (PET) system. The first ten-channel prototype chip (APD-Chip) of the analog parts has been designed and fabricated in a 0.35 μm CMOS process. Every channel of the APD_Chip includes a charge-sensitive preamplifier (CSA), a CR-(RC)2 shaper, and an analog buffer. In a channel, the CSA reads charge signals (10 bits dynamic range) from an APD array having 10 pF of capacitance per pixel. A linearized degenerated differential pair which ensures high linearity in all dynamical range is used as the high feedback resistor for preventing pile up of signals. The designed CSA has the capability of compensating automatically up to 200 nA leakage current from the detector. The CR-(RC)2 shaper filters and shapes the output signal of the CSA. An equivalent input noise charge obtained from test is 275 e -+ 10 e-/pF. In this paper the prototype is presented for both its theoretical analysis and its test results.

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.

Dielectric relaxation of barium strontium titanate and application to thin films for DRAM capacitors

NASA Astrophysics Data System (ADS)

Baniecki, John David

This thesis examines the issues associated with incorporating the high dielectric constant material Barium Strontium Titanate (BSTO) in to the storage capacitor of a dynamic random access memory (DRAM). The research is focused on two areas: characterizing and understanding the factors that control charge retention in BSTO thin films and modifying the electrical properties using ion implantation. The dielectric relaxation of BSTO thin films deposited by metal-organic chemical vapor deposition (MOCVD) is investigated in the time and frequency domains. It is shown that the frequency dispersion of the complex capacitance of BSTO thin films can be understood in terms of a power-law frequency dependence from 1mHz to 20GHz. From the correspondence between the time and frequency domain measurements, it is concluded that the power-law relaxation currents extend back to the nano second regime of DRAM operation. The temperature, field, and annealing dependence of the dielectric relaxation currents are also investigated and mechanisms for the observed power law relaxation are explored. An equivalent circuit model of a high dielectric constant thin film capacitor is developed based on the electrical measurements and implemented in PSPICE. Excellent agreement is found between the experimental and simulated electrical characteristics showing the utility of the equivalent circuit model in simulating the electrical properties of high dielectric constant thin films. Using the equivalent circuit model, it is shown that the greatest charge loss due to dielectric relaxation occurs during the first read after a refresh time following a write to the opposite logic state for a capacitor that has been written to the same logic state for a long time (opposite state write charge loss). A theoretical closed form expression that is a function of three material parameters is developed which estimates the opposite state write charge loss due to dielectric relaxation. Using the closed form expression, and BSTO thin film electrical characteristics, the charge loss due to dielectric relaxation is estimated to be 6--12% of the initial charge stored on the capacitor plates for MOCVD BSTO thin films with Pt electrodes after a post top electrode anneal in oxygen. In contrast, it is shown that the charge loss due to steady state leakage is only 0.0125--0.125% of the initial charge stored on the capacitor plates. Charge retention is shown to depend strongly on the annealing conditions. Annealing MOCVD BSTO thin films with Pt electrodes in forming gas (95% Ar 5% H2) increases charge loss due to dielectric relaxation to as much as 60%. Ion implantation is used to dope BSTO thin films with Mn. X-ray diffraction and transmission electron microscopy (TEM) shows ion implantation significantly damages the film leaving only short-range order, but post-implant annealing heals the damage. Capacitance recovery after post-implant annealing is as high as 94% for 15 nm BSTO films. At low implant doses, the Mn doped films have substantially lower leakage (up to a factor of ten lower) and only slightly higher relaxation currents and dielectric loss indicating that ion implantation may be a potentially viable way of introducing dopants into high dielectric constant thin films for future DRAM applications.

Integration of solid-state nanopores in a 0.5 μm CMOS foundry process.

PubMed

Uddin, A; Yemenicioglu, S; Chen, C-H; Corigliano, E; Milaninia, K; Theogarajan, L

2013-04-19

High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA-base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the integration of solid-state nanopore devices in a commercial complementary metal-oxide-semiconductor (CMOS) potentiostat chip implemented in On-Semiconductor's 0.5 μm technology. Nanopore membranes incorporating electrodes are fabricated by post-CMOS micromachining utilizing the n+ polysilicon/SiO2/n+ polysilicon capacitor structure available in the aforementioned process. Nanopores are created in the CMOS process by drilling in a transmission electron microscope and shrinking by atomic layer deposition. We also describe a batch fabrication method to process a large of number of electrode-embedded nanopores with sub-10 nm diameter across CMOS-compatible wafers by electron beam lithography and atomic layer deposition. The CMOS-compatibility of our fabrication process is verified by testing the electrical functionality of on-chip circuitry. We observe high current leakage with the CMOS nanopore devices due to the ionic diffusion through the SiO2 membrane. To prevent this leakage, we coat the membrane with Al2O3, which acts as an efficient diffusion barrier against alkali ions. The resulting nanopore devices also exhibit higher robustness and lower 1/f noise as compared to SiO2 and SiNx. Furthermore, we propose a theoretical model for our low-capacitance CMOS nanopore devices, showing good agreement with the experimental value. In addition, experiments and theoretical models of translocation studies are presented using 48.5 kbp λ-DNA in order to prove the functionality of on-chip pores coated with Al2O3.

Suppression of gate leakage current in in-situ grown AlN/InAlN/AlN/GaN heterostructures based on the control of internal polarization fields

NASA Astrophysics Data System (ADS)

Kotani, Junji; Yamada, Atsushi; Ishiguro, Tetsuro; Yamaguchi, Hideshi; Nakamura, Norikazu

2017-03-01

This paper investigates the gate leakage characteristics of in-situ AlN capped InAlN/AlN/GaN heterostructures grown by metal-organic vapor phase epitaxy. It was revealed that the leakage characteristics of AlN capped InAlN/AlN/GaN heterostructures are strongly dependent on the growth temperature of the AlN cap. For an AlN capped structure with an AlN growth temperature of 740 °C, the leakage current even increased although there exists a large bandgap material on InAlN/AlN/GaN heterostructures. On the other hand, a large reduction of the gate leakage current by 4-5 orders of magnitudes was achieved with a very low AlN growth temperature of 430 °C. X-ray diffraction analysis of the AlN cap grown at 740 °C indicated that the AlN layer is tensile-strained. In contrast to this result, the amorphous structure was confirmed for the AlN cap grown at 430 °C by transmission electron microscopy. Furthermore, theoretical analysis based on one-dimensional band simulation was carried out, and the large increase in two-dimensional electron gas (2DEG) observed in Hall measurements was well reproduced by taking into account the spontaneous and piezo-electric polarization in the AlN layer grown at 740 °C. For the AlN capped structure grown at 430 °C, it is believed that the reduced polarization field in the AlN cap suppressed the penetration of 2DEG into the InAlN barrier layer, resulting in a small impact on 2DEG mobility and density. We believe that an in-situ grown AlN cap with a very low growth temperature of 430 °C is a promising candidate for high-frequency/high-power GaN-based devices with low gate leakage current.

The timing of cortical granule fusion, content dispersal, and endocytosis during fertilization of the hamster egg: an electrophysiological and histochemical study.

PubMed

Kline, D; Stewart-Savage, J

1994-03-01

To determine the temporal relationship between cortical granule exocytosis and the repetitive calcium transients, which are characteristic of mammalian fertilization, we monitored membrane addition from exocytosis during fertilization of hamster eggs. Continuous measurement of membrane capacitance by applying a 3.1-nA alternating current at 375 Hz showed addition of cortical granule membrane. Simultaneous measurement of membrane potential revealed each calcium transient by the appearance of transient hyperpolarizing responses due to calcium-activated potassium channels in the egg. The initial membrane capacitance of the eggs averaged 736 +/- 44 pF (mean +/- SD; n = 7) and an increase in capacitance of 61 +/- 19 pF occurred within 4 sec of the start of the first hyperpolarizing response (HR) after fertilization. Immediately after the first increase in capacitance there was a gradual decline in membrane capacitance in all eggs and in five/seven eggs the capacitance returned to the unfertilized level in 7.8 +/- 4.4 min. The gradual decline in capacitance after the first increase indicated endocytosis, which was confirmed by the internalization of fluorescently labeled dextran. Superimposed on the gradual decline in membrane capacitance were smaller increases in capacitance that occurred with the second and later HRs. The total increase in capacitance from the first three events averaged 72 +/- 19 pF, representing an average increase in capacitance of about 10% of the capacitance of the unfertilized egg. By labeling eggs before and after permeabilization with two different fluorochromes attached to Lens culinaris agglutinin, we demonstrate that the dispersal of the cortical granules contents does not occur immediately after exocytosis. Our results demonstrate that cortical granule exocytosis in hamster eggs is closely coupled to the periodic increases in calcium, that the contents of the cortical granules are slow to disperse, and that after exocytosis, the surface area of the egg returns to the unfertilized level because of a period of endocytosis.

Optimal Dynamic Sub-Threshold Technique for Extreme Low Power Consumption for VLSI

NASA Technical Reports Server (NTRS)

Duong, Tuan A.

2012-01-01

For miniaturization of electronics systems, power consumption plays a key role in the realm of constraints. Considering the very large scale integration (VLSI) design aspect, as transistor feature size is decreased to 50 nm and below, there is sizable increase in the number of transistors as more functional building blocks are embedded in the same chip. However, the consequent increase in power consumption (dynamic and leakage) will serve as a key constraint to inhibit the advantages of transistor feature size reduction. Power consumption can be reduced by minimizing the voltage supply (for dynamic power consumption) and/or increasing threshold voltage (V(sub th), for reducing leakage power). When the feature size of the transistor is reduced, supply voltage (V(sub dd)) and threshold voltage (V(sub th)) are also reduced accordingly; then, the leakage current becomes a bigger factor of the total power consumption. To maintain low power consumption, operation of electronics at sub-threshold levels can be a potentially strong contender; however, there are two obstacles to be faced: more leakage current per transistor will cause more leakage power consumption, and slow response time when the transistor is operated in weak inversion region. To enable low power consumption and yet obtain high performance, the CMOS (complementary metal oxide semiconductor) transistor as a basic element is viewed and controlled as a four-terminal device: source, drain, gate, and body, as differentiated from the traditional approach with three terminals: i.e., source and body, drain, and gate. This technique features multiple voltage sources to supply the dynamic control, and uses dynamic control to enable low-threshold voltage when the channel (N or P) is active, for speed response enhancement and high threshold voltage, and when the transistor channel (N or P) is inactive, to reduce the leakage current for low-leakage power consumption.

Suppression of Lateral Diffusion and Surface Leakage Currents in nBn Photodetectors Using an Inverted Design

NASA Astrophysics Data System (ADS)

Du, X.; Savich, G. R.; Marozas, B. T.; Wicks, G. W.

2018-02-01

Surface leakage and lateral diffusion currents in InAs-based nBn photodetectors have been investigated. Devices fabricated using a shallow etch processing scheme that etches through the top contact and stops at the barrier exhibited large lateral diffusion current but undetectably low surface leakage. Such large lateral diffusion current significantly increased the dark current, especially in small devices, and causes pixel-to-pixel crosstalk in detector arrays. To eliminate the lateral diffusion current, two different approaches were examined. The conventional solution utilized a deep etch process, which etches through the top contact, barrier, and absorber. This deep etch processing scheme eliminated lateral diffusion, but introduced high surface current along the device mesa sidewalls, increasing the dark current. High device failure rate was also observed in deep-etched nBn structures. An alternative approach to limit lateral diffusion used an inverted nBn structure that has its absorber grown above the barrier. Like the shallow etch process on conventional nBn structures, the inverted nBn devices were fabricated with a processing scheme that only etches the top layer (the absorber, in this case) but avoids etching through the barrier. The results show that inverted nBn devices have the advantage of eliminating the lateral diffusion current without introducing elevated surface current.

Fabrication of nickel hydroxide electrodes with open-ended hexagonal nanotube arrays for high capacitance supercapacitors.

PubMed

Wu, Mao-Sung; Huang, Kuo-Chih

2011-11-28

A nickel hydroxide electrode with open-ended hexagonal nanotube arrays, prepared by hydrolysis of nickel chloride in the presence of hexagonal ZnO nanorods, shows a very high capacitance of 1328 F g(-1) at a discharge current density of 1 A g(-1) due to the significantly improved ion transport.

In-Situ Synthesis of NiMoO4 on Ni Foam as a Binder-Free Electrode for Supercapacitor

NASA Astrophysics Data System (ADS)

Chiu, Ta-Wei

Transition metal oxides have attracted much attention for electrode materials of supercapacitors due to their outstanding capacitive behavior. One of them is NiMoO4 with the high electrochemical activity of Ni. Constricted by its intrinsically poor electrical conductivity and limited electroactive sites of aggregated NiMoO4, the capacitive performance of NiMoO 4 are far below expectation. Directly growth of NiMoO4 on nickel foam to fabricate binder-free electrodes is proposed to solve the issues. In this thesis, we successfully constructed interconnected NiMoO4 nanosheets on the Ni foam by a designed reaction between H2MoO 4 aqueous solution and Ni foam. The effects of H2MoO 4 concentration and reaction time were systematically investigated. The best electrochemical performance of NiMoO4 electrodes can be obtained with 0.005 M H2MoO4 for 80 hours. The maximum areal capacitance can reach 0.724 F/cm2 followed with outstanding rate capability (70.1% capacitance retention when current density increase from 1 mA/cm2 to 10 mA/cm2). The excellent areal capacitance and rate capability may be attributed to its interconnected NiMoO 4 nanosheets and good adhesion between electroactive materials and current collector.

Implementation and initial test result of a prototype solid state modulator for pulsed magnetron

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

Dake, Vishal; Mangalvedekar, H.A., E-mail: vishaldake90@gmail.com; Tillu, Abhijit

2014-07-01

A solid-state modulator rated for 50 kV, 120A, 4μs and 250 Hz has been designed. The discharging circuit of the modulator is being tested at ∼ 33 kV, 40-80A, at a maximum pulse repetition rate of 30 pps. The paper discusses development and testing of prototype discharging circuit on resistive load and magnetron. The technique used for measurement of pulse transformer leakage inductance, distributed capacitance and stray primary circuit series inductance will also be discussed in detail. It is necessary to have Energy Storage Capacitors with low ESL for these applications (ESL < 40 nH). The method used for evaluatingmore » the ESL of locally available metalized polypropylene capacitors will also be presented. (author)« less

Sensitivity Challenge of Steep Transistors

NASA Astrophysics Data System (ADS)

Ilatikhameneh, Hesameddin; Ameen, Tarek A.; Chen, ChinYi; Klimeck, Gerhard; Rahman, Rajib

2018-04-01

Steep transistors are crucial in lowering power consumption of the integrated circuits. However, the difficulties in achieving steepness beyond the Boltzmann limit experimentally have hindered the fundamental challenges in application of these devices in integrated circuits. From a sensitivity perspective, an ideal switch should have a high sensitivity to the gate voltage and lower sensitivity to the device design parameters like oxide and body thicknesses. In this work, conventional tunnel-FET (TFET) and negative capacitance FET are shown to suffer from high sensitivity to device design parameters using full-band atomistic quantum transport simulations and analytical analysis. Although Dielectric Engineered (DE-) TFETs based on 2D materials show smaller sensitivity compared with the conventional TFETs, they have leakage issue. To mitigate this challenge, a novel DE-TFET design has been proposed and studied.

In situ fabrication of nickel based oxide on nitrogen-doped graphene for high electrochemical performance supercapacitors

NASA Astrophysics Data System (ADS)

Pan, Denghui; Zhang, Mingmei; Wang, Ying; Yan, Zaoxue; Jing, Junjie; Xie, Jimin

2017-10-01

In this article, we synthesize Ni(OH)2 homogeneous grown on nitrogen-doped graphene (Ni(OH)2/NG), subsequently, small and uniform nickel oxide nanoparticle (NiO/NG) is also successfully obtained through tube furnace calcination method. The high specific capacitance of the NiO/NG electrode can reach to 1314.1 F/g at a charge and discharge current density of 2 A/g, meanwhile the specific capacitance of Ni(OH)2/NG electrode is also 1350 F/g. The capacitance of NiO/NG can remain 93.7% of the maximum value after 1000 cycles, while the Ni(OH)2/NG electrode losses 16.9% of the initial capacitance after 1000 cycles. It can be attributed to nickel hydroxide instability during charge-discharge cycles.

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.

Fabrication and high temperature characteristics of ion-implanted GaAs bipolar transistors and ring-oscillators

NASA Technical Reports Server (NTRS)

Doerbeck, F. H.; Yuan, H. T.; Mclevige, W. V.

1981-01-01

Ion implantation techniques that permit the reproducible fabrication of bipolar GaAs integrated circuits are studied. A 15 stage ring oscillator and discrete transistor were characterized between 25 and 400 C. The current gain of the transistor was found to increase slightly with temperature. The diode leakage currents increase with an activation energy of approximately 1 eV and dominate the transistor leakage current 1 sub CEO above 200 C. Present devices fail catastrophically at about 400 C because of Au-metallization.

Rapid detection of microbial cell abundance in aquatic systems

DOE PAGES

Rocha, Andrea M.; Yuan, Quan; Close, Dan M.; ...

2016-06-01

The detection and quantification of naturally occurring microbial cellular densities is an essential component of environmental systems monitoring. While there are a number of commonly utilized approaches for monitoring microbial abundance, capacitance-based biosensors represent a promising approach because of their low-cost and label-free detection of microbial cells, but are not as well characterized as more traditional methods. Here, we investigate the applicability of enhanced alternating current electrokinetics (ACEK) capacitive sensing as a new application for rapidly detecting and quantifying microbial cellular densities in cultured and environmentally sourced aquatic samples. ACEK capacitive sensor performance was evaluated using two distinct and dynamicmore » systems the Great Australian Bight and groundwater from the Oak Ridge Reservation in Oak Ridge, TN. Results demonstrate that ACEK capacitance-based sensing can accurately determine microbial cell counts throughout cellular concentrations typically encountered in naturally occurring microbial communities (10 3 – 10 6 cells/mL). A linear relationship was observed between cellular density and capacitance change correlations, allowing a simple linear curve fitting equation to be used for determining microbial abundances in unknown samples. As a result, this work provides a foundation for understanding the limits of capacitance-based sensing in natural environmental samples and supports future efforts focusing on evaluating the robustness ACEK capacitance-based within aquatic environments.« less

Facile preparation of polypyrrole/graphene oxide nanocomposites with large areal capacitance using electrochemical codeposition for supercapacitors

NASA Astrophysics Data System (ADS)

Zhou, Haihan; Han, Gaoyi; Xiao, Yaoming; Chang, Yunzhen; Zhai, Hua-Jin

2014-10-01

A simple and low-cost electrochemical codeposition method has been introduced to fabricate polypyrrole/graphene oxide (PPy/GO) nanocomposites and the areal capacitance of conducting polymer/GO composites is reported for the first time. Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) are implemented to determine the PPy/GO nanocomposites are successfully prepared and the interaction between PPy and GO. The as-prepared PPy/GO nanocomposites show the curly sheet-like morphology, superior capacitive behaviors and cyclic stability. Furthermore, the varying deposition time is implemented to investigate the impact of the loading amount on electrochemical behavior of the composites, and a high areal capacitance of 152 mF cm-2 is achieved at 10 mV s-1 CV scan. However, the thicker films caused by the long deposition time would result in larger diffusion resistance of electrolyte ions, consequently exhibit the relatively lower capacitance value at the high current density. The GCD tests indicate moderate deposition time is more suitable for the fast charge/discharge. Considering the very simple and effective synthetic process, the PPy/GO nanocomposites with relatively high areal capacitance are competitive candidate for supercapacitor application, and its capacitive performances can be easily tuned by varying the deposition time.

Rapid detection of microbial cell abundance in aquatic systems

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

Rocha, Andrea M.; Yuan, Quan; Close, Dan M.

The detection and quantification of naturally occurring microbial cellular densities is an essential component of environmental systems monitoring. While there are a number of commonly utilized approaches for monitoring microbial abundance, capacitance-based biosensors represent a promising approach because of their low-cost and label-free detection of microbial cells, but are not as well characterized as more traditional methods. Here, we investigate the applicability of enhanced alternating current electrokinetics (ACEK) capacitive sensing as a new application for rapidly detecting and quantifying microbial cellular densities in cultured and environmentally sourced aquatic samples. ACEK capacitive sensor performance was evaluated using two distinct and dynamicmore » systems the Great Australian Bight and groundwater from the Oak Ridge Reservation in Oak Ridge, TN. Results demonstrate that ACEK capacitance-based sensing can accurately determine microbial cell counts throughout cellular concentrations typically encountered in naturally occurring microbial communities (10 3 – 10 6 cells/mL). A linear relationship was observed between cellular density and capacitance change correlations, allowing a simple linear curve fitting equation to be used for determining microbial abundances in unknown samples. As a result, this work provides a foundation for understanding the limits of capacitance-based sensing in natural environmental samples and supports future efforts focusing on evaluating the robustness ACEK capacitance-based within aquatic environments.« less

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.

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.

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

Simulation of real I-V characteristics of metal/GaN/AlGaN heterostructure based on the 12-EXT model of trap-assisted tunnelling

NASA Astrophysics Data System (ADS)

Racko, Juraj; Benko, Peter; Mikolášek, Miroslav; Granzner, Ralf; Kittler, Mario; Schwierz, Frank; Harmatha, Ladislav; Breza, Juraj

2017-02-01

The contribution employs electrical simulation to assess the effect of the distribution of aluminium in the metal/GaN/AlGaN heterostructure on the leakage current. The heterostructure is characterized by a high density of traps causing an increase of the leakage current consisting of the thermionic emission component and of a non-negligible contribution of trap-assisted tunnelling. The leakage current is highly sensitive to the bending of the potential barrier Ec in the subsurface region of the GaN/AlGaN structure. The band bending is strongly affected by the sheet bound charge at the first GaN/AlGaN/GaN interface due to spontaneous and piezoelectric polarization. The overall charge depends on the concentration of Al, the distribution of Al at the first heterointerface having a strong effect on the formation of the potential barrier.

TID Simulation of Advanced CMOS Devices for Space Applications

NASA Astrophysics Data System (ADS)

Sajid, Muhammad

2016-07-01

This paper focuses on Total Ionizing Dose (TID) effects caused by accumulation of charges at silicon dioxide, substrate/silicon dioxide interface, Shallow Trench Isolation (STI) for scaled CMOS bulk devices as well as at Buried Oxide (BOX) layer in devices based on Silicon-On-Insulator (SOI) technology to be operated in space radiation environment. The radiation induced leakage current and corresponding density/concentration electrons in leakage current path was presented/depicted for 180nm, 130nm and 65nm NMOS, PMOS transistors based on CMOS bulk as well as SOI process technologies on-board LEO and GEO satellites. On the basis of simulation results, the TID robustness analysis for advanced deep sub-micron technologies was accomplished up to 500 Krad. The correlation between the impact of technology scaling and magnitude of leakage current with corresponding total dose was established utilizing Visual TCAD Genius program.

Capacitance-based damage detection sensing for aerospace structural composites

NASA Astrophysics Data System (ADS)

Bahrami, P.; Yamamoto, N.; Chen, Y.; Manohara, H.

2014-04-01

Damage detection technology needs improvement for aerospace engineering application because detection within complex composite structures is difficult yet critical to avoid catastrophic failure. Damage detection is challenging in aerospace structures because not all the damage detection technology can cover the various defect types (delamination, fiber fracture, matrix crack etc.), or conditions (visibility, crack length size, etc.). These defect states are expected to become even more complex with future introduction of novel composites including nano-/microparticle reinforcement. Currently, non-destructive evaluation (NDE) methods with X-ray, ultrasound, or eddy current have good resolutions (< 0.1 mm), but their detection capabilities is limited by defect locations and orientations and require massive inspection devices. System health monitoring (SHM) methods are often paired with NDE technologies to signal out sensed damage, but their data collection and analysis currently requires excessive wiring and complex signal analysis. Here, we present a capacitance sensor-based, structural defect detection technology with improved sensing capability. Thin dielectric polymer layer is integrated as part of the structure; the defect in the structure directly alters the sensing layer's capacitance, allowing full-coverage sensing capability independent of defect size, orientation or location. In this work, capacitance-based sensing capability was experimentally demonstrated with a 2D sensing layer consisting of a dielectric layer sandwiched by electrodes. These sensing layers were applied on substrate surfaces. Surface indentation damage (~1mm diameter) and its location were detected through measured capacitance changes: 1 to 250 % depending on the substrates. The damage detection sensors are light weight, and they can be conformably coated and can be part of the composite structure. Therefore it is suitable for aerospace structures such as cryogenic tanks and rocket fairings for example. The sensors can also be operating in space and harsh environment such as high temperature and vacuum.

A facile approach to fabricate flexible all-solid-state supercapacitors based on MnFe2O4/graphene hybrids

NASA Astrophysics Data System (ADS)

Cai, Weihua; Lai, Ting; Dai, Wanlin; Ye, Jianshan

2014-06-01

A critical challenge for the construction of flexible electrochemical capacitors is the preparation of flexible electrodes with large specific capacitance and robust mechanical strength. Here, we demonstrate a facile approach to make high performance and flexible electrodes by dropping MnFe2O4/graphene hybrid inks onto flexible graphite sheets (as current collectors and substrates) and drying under an infrared lamp. MnFe2O4/graphene hybrid inks are synthesized by immobilizing the MnFe2O4 microspheres on the graphene nanosheets via a simple solvothermal route. Electrochemical studies show that MnFe2O4/graphene exhibits a high capacitance of 300 F g-1 at a current density of 0.3 A g-1. In addition, the excellent electrochemical performance of a supercapacitor consisting of a sandwich structure of two pieces of MnFe2O4/graphene hybrids modified electrodes separated by polyvinyl alcohol (PVA)-H2SO4 gel electrolyte is further explored. Our studies reveal that the flexible supercapacitor device with 227 μm thickness can achieve a maximum specific capacitance of 120 F g-1 at a current density of 0.1 A g-1 and excellent cycle performance retaining 105% capacitance after 5000 cycles. This research may offer a method for the fabrication of lightweight, stable, flexible and high performance energy storage devices.

One-step electroplating porous graphene oxide electrodes of supercapacitors for ultrahigh capacitance and energy density.

PubMed

Wang, Yongjie; Zhu, Jiaqi

2015-02-06

An electroplating method was used for the first time to synthesize 3D porous graphene oxide (PGO) architectures, exhibiting ultrahigh capacitance and energy density as electrodes of supercapacitors. Scanning electron microscopy illustrated the porous structures which promoted the stability and alleviated the stacking of the graphene oxide layers. As investigated in a three-electrode supercapacitor cell, PGO electrodes exhibited the maximum capacitance and energy of 973 F · g(-1) and 98.4 Wh · Kg(-1), which are better than current reports and comparable to batteries. At 4 A · g(-1) for high-power applications, PGO electrodes reached a capacitance, energy, and power density of 493 F · g(-1), 49.9 Wh · Kg(-1), and 1700 W · Kg(-1), and they retained ∼97.83% of capacitance after 10 000 charge/discharge processes. Furthermore, when the PGO was bent exaggeratedly, it still displayed identical properties, which is of important significance for supporting wearable devices.

Integrated circuit electrometer and sweep circuitry for an atmospheric probe

NASA Technical Reports Server (NTRS)

Zimmerman, L. E.

1971-01-01

The design of electrometer circuitry using an integrated circuit operational amplifier with a MOSFET input is described. Input protection against static voltages is provided by a dual ultra low leakage diode or a neon lamp. Factors affecting frequency response leakage resistance, and current stability are discussed, and methods are suggested for increasing response speed and for eliminating leakage resistance and current instabilities. Based on the above, two practical circuits, one having a linear response and the other a logarithmic response, were designed and evaluated experimentally. The design of a sweep circuit to implement mobility measurements using atmospheric probes is presented. A triangular voltage waveform is generated and shaped to contain a step in voltage from zero volts in both positive and negative directions.

Study of the dose rate effect of 180 nm nMOSFETs

NASA Astrophysics Data System (ADS)

He, Bao-Ping; Yao, Zhi-Bin; Sheng, Jiang-Kun; Wang, Zu-Jun; Huang, Shao-Yan; Liu, Min-Bo; Xiao, Zhi-Gang

2015-01-01

Radiation induced offstate leakage in the shallow trench isolation regions of SIMC 0.18 μm nMOSFETs is studied as a function of dose rate. A “true” dose rate effect (TDRE) is observed. Increased damage is observed at low dose rate (LDR) than at high dose rate (HDR) when annealing is taken into account. A new method of simulating radiation induced degradation in shallow trench isolation (STI) is presented. A comparison of radiation induced offstate leakage current in test nMOSFETs between total dose irradiation experiments and simulation results exhibits excellent agreement. The investigation results imply that the enhancement of the leakage current may be worse for the dose rate encountered in the environment of space.

The Implementation Of Solid State Switches In A Parallel Configuration To Gain Output Current Capacity In A High Current Capacitive Discharge Unit (CDU).

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

Chaves, Mario Paul

2017-07-01

For my project I have selected to research and design a high current pulse system, which will be externally triggered from a 5V pulse. The research will be conducted in the region of paralleling the solid state switches for a higher current output, as well as to see if there will be any other advantages in doing so. The end use of the paralleled solid state switches will be used on a Capacitive Discharge Unit (CDU). For the first part of my project, I have set my focus on the design of the circuit, selection of components, and simulation ofmore » the circuit.« less

Preparation and the Electrochemical Performance of MnO2/PANI@CNT Composite for Supercapacitors.

PubMed

Wang, Hongjuan; Wang, Xiaohui; Peng, Cheng; Peng, Feng; Yu, Hao

2015-01-01

Polyaniline (PANI) was settled on the surface of CNTs in advance and then used as self-sacrifice reducing agent that would react with KMnO4 to prepare MnO2/PANI@CNT supercapacitor material. With PANI substituting for CNTs to participant the redox reaction, CNTs was protected from being destroyed and could maintain its original morphology and conductivity. The results of cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) show that the optimal capacitive performance can be reached at the MnO2 loading of 64.4 wt% and the pH of 1 during the deposition of MnO2. With the protective PANI, MnO2/PANI@CNT composite exhibits the superior specific capacitance of 215.8 F/g at a current density of 200 mA/g and remains 86.5% of its maximal specific capacitance at a current density of 1000 mA/g.

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.

Three-dimensional sulphur/nitrogen co-doped reduced graphene oxide as high-performance supercapacitor binder-free electrodes

NASA Astrophysics Data System (ADS)

Huo, Jinghao; Zheng, Peng; Wang, Xiaofei; Guo, Shouwu

2018-06-01

Sulphur/nitrogen co-doped reduced graphene oxide (SNG) aerogels were prepared by a simple solvothermal method with l-cysteine-assisted in ethylene glycol. The morphology and composition tests showed that the S/N heteroatoms were evenly distributed on SNG microsheets, and these microsheets were further composed of SNG aerogels with three-dimensional (3D) porous structure. The cyclic voltammetry and galvanostatic charge/discharge tests illustrated the SNG bind-free electrode possessed electric double-layer capacitance and pseudocapacitance, and had a capacitance of 254 F g-1 at a current density of 1 A g-1. After the 5000 cycles tests, the capacitance retained 83.54% at a current density of 2 A g-1. Meanwhile, the electrochemical impedance spectroscopy data shown the electrode materials had excellent capacity and good conductivity. Hence, the SNG aerogel prepared by l-cysteine-assisted solvothermal method is a great material for high-performance supercapacitors.

[Reflection on the present study of anastomotic leakage after colorectal surgery].

PubMed

Wu, Zhouqiao; Shi, Jinyao; Li, Ziyu; Ji, Jiafu

Anastomotic leakage is one of the most serious complications of colorectal surgery. Despite progress in available surgical techniques, the morbidity associated with anastomotic leakage remains high. In this review, we summarize the current clinical status of this complication, the problems it causes, and relevant research achievements. To date, a lack of consensus regarding the diagnosis of anastomotic leakage has resulted in varying rates of diagnosis across countries and regions worldwide. Accurately predicting the occurrence of anastomotic leakage using the established risk factors and preoperative scoring systems remains difficult. Many of the described preventive measures, including defunctioning stoma creation, positive air leak testing, and use of effective tissue adhesives, remain controversial; more evidence-based medical information is urgently needed. Delayed diagnoses of anastomotic leakage also remain common in clinical practice. To prevent catastrophic outcomes, such as reoperations or deaths, early diagnosis is critically important. Parameters local to the area of the anastomosis may facilitate early detection of leakage, but their effectiveness is subject to clinical validation. Lastly, the pathological etiology of anastomotic leakage remains to be determined, and its elucidation may inspire innovative interventions that solve this critical surgical complication.

Current transient spectroscopy for trapping analysis on Au-free AlGaN/GaN Schottky barrier diode

NASA Astrophysics Data System (ADS)

Hu, J.; Stoffels, S.; Lenci, S.; Bakeroot, B.; Venegas, R.; Groeseneken, G.; Decoutere, S.

2015-02-01

This paper presents a combined technique of high voltage off-state stress and current transient measurements to investigate the trapping/de-trapping characteristics of Au-free AlGaN/GaN Schottky barrier diodes. The device features a symmetric three-terminal structure with a central anode contact surrounded by two separate cathodes. Under the diode off-state stress conditions, the two separate cathodes were electrically shorted. The de-trapping dynamics was studied by monitoring the recovery of the two-dimensional electron gas (2DEG) current at different temperatures by applying 0.5 V at cathode 2 while grounding cathode 1. During the recovery, the anode contact acts as a sensor of changes in diode leakage current. This leakage variation was found to be mainly due to the barrier height variation. With this method, the energy level and capture cross section of different traps in the AlGaN/GaN Schottky barrier diode can be extracted. Furthermore, the physical location of different trapping phenomena is indicated by studying the variation of the diode leakage current during the recovery. We have identified two distinct trapping mechanisms: (i) electron trapping at the AlGaN surface in the vicinity of the Schottky contact which results in the leakage reduction (barrier height ϕB increase) together with RON degradation; (ii) the electron trapping in the GaN channel layer which partially depletes the 2DEG. The physical origin of the two different traps is discussed in the text.

First principles calculations of La2O3/GaAs interface properties under biaxial strain and hydrostatic pressure

NASA Astrophysics Data System (ADS)

Shi, Li-Bin; Li, Ming-Biao; Xiu, Xiao-Ming; Liu, Xu-Yang; Zhang, Kai-Cheng; Li, Chun-Ran; Dong, Hai-Kuan

2017-04-01

La2O3 is a potential dielectric material with high permittivity (high-κ) for metal-oxide-semiconductor (MOS) devices. However, band offsets and oxide defects should still be concerned. Smaller band offsets and carrier traps increase leakage current, and degenerate performance of the devices. In this paper, the interface behaviors of La2O3/GaAs under biaxial strain and hydrostatic pressure are investigated, which is performed by first principles calculations based on density functional theory (DFT). Strain engineering is attempted to improve performance of the metal/La2O3/GaAs devices. First of all, we creatively realize band alignment of La2O3/GaAs interface under biaxial strain and hydrostatic pressure. The proper biaxial tensile strain can effectively increase valence band offsets (VBO) and conduction band offsets (CBO), which can be used to suppress leakage current. However, the VBO will decrease with the increase of hydrostatic pressure, indicating that performance of the devices is degenerated. Then, a direct tunneling leakage current model is used to investigate current and voltage characteristics of the metal/La2O3/GaAs. The impact of biaxial strain and hydrostatic pressure on leakage current is discussed. At last, formation energies and transition levels of oxygen interstitial (Oi) and oxygen vacancy (VO) in La2O3 are assessed. We investigate how they will affect performance of the devices.

Shape-controlled synthesis of NiCo2S4 and their charge storage characteristics in supercapacitors.

PubMed

Zhang, Yufei; Ma, Mingze; Yang, Jun; Sun, Chencheng; Su, Haiquan; Huang, Wei; Dong, Xiaochen

2014-08-21

In this work, a facile hydrothermal approach for the shape-controlled synthesis of NiCo2S4 architectures is reported. Four different morphologies, urchin-, tube-, flower-, and cubic-like NiCo2S4 microstructures, have been successfully synthesized by employing various solvents. The obtained precursors and products have been characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. It is revealed that the supersaturation of nucleation and crystal growth is determined by the solvent polarity and solubility, which can precisely control the morphology of NiCo2S4 microstructures. The detailed electrochemical performances of the various NiCo2S4 microstructures are investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The results indicate that the tube-like NiCo2S4 exhibits promising capacitive properties with high capacitance and excellent retention. Its specific capacitance can reach 1048 F g(-1) at the current density of 3.0 A g(-1) and 75.9% of its initial capacitance is maintained at the current density of 10.0 A g(-1) after 5000 charge-discharge cycles.

Shape-controlled synthesis of NiCo2S4 and their charge storage characteristics in supercapacitors

NASA Astrophysics Data System (ADS)

Zhang, Yufei; Ma, Mingze; Yang, Jun; Sun, Chencheng; Su, Haiquan; Huang, Wei; Dong, Xiaochen

2014-07-01

In this work, a facile hydrothermal approach for the shape-controlled synthesis of NiCo2S4 architectures is reported. Four different morphologies, urchin-, tube-, flower-, and cubic-like NiCo2S4 microstructures, have been successfully synthesized by employing various solvents. The obtained precursors and products have been characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. It is revealed that the supersaturation of nucleation and crystal growth is determined by the solvent polarity and solubility, which can precisely control the morphology of NiCo2S4 microstructures. The detailed electrochemical performances of the various NiCo2S4 microstructures are investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The results indicate that the tube-like NiCo2S4 exhibits promising capacitive properties with high capacitance and excellent retention. Its specific capacitance can reach 1048 F g-1 at the current density of 3.0 A g-1 and 75.9% of its initial capacitance is maintained at the current density of 10.0 A g-1 after 5000 charge-discharge cycles.

Efficiently dense hierarchical graphene based aerogel electrode for supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Xin; Lu, Chengxing; Peng, Huifen; Zhang, Xin; Wang, Zhenkun; Wang, Gongkai

2016-08-01

Boosting gravimetric and volumetric capacitances simultaneously at a high rate is still a discrepancy in development of graphene based supercapacitors. We report the preparation of dense hierarchical graphene/activated carbon composite aerogels via a reduction induced self-assembly process coupled with a drying post treatment. The compact and porous structures of composite aerogels could be maintained. The drying post treatment has significant effects on increasing the packing density of aerogels. The introduced activated carbons play the key roles of spacers and bridges, mitigating the restacking of adjacent graphene nanosheets and connecting lateral and vertical graphene nanosheets, respectively. The optimized aerogel with a packing density of 0.67 g cm-3 could deliver maximum gravimetric and volumetric capacitances of 128.2 F g-1 and 85.9 F cm-3, respectively, at a current density of 1 A g-1 in aqueous electrolyte, showing no apparent degradation to the specific capacitance at a current density of 10 A g-1 after 20000 cycles. The corresponding gravimetric and volumetric capacitances of 116.6 F g-1 and 78.1 cm-3 with an acceptable cyclic stability are also achieved in ionic liquid electrolyte. The results show a feasible strategy of designing dense hierarchical graphene based aerogels for supercapacitors.

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).

Hierarchically structured Ni(3)S(2)/carbon nanotube composites as high performance cathode materials for asymmetric supercapacitors.

PubMed

Dai, Chao-Shuan; Chien, Pei-Yi; Lin, Jeng-Yu; Chou, Shu-Wei; Wu, Wen-Kai; Li, Ping-Hsuan; Wu, Kuan-Yi; Lin, Tsung-Wu

2013-11-27

The Ni3S2 nanoparticles with the diameters ranging from 10 to 80 nm are grown on the backbone of conductive multiwalled carbon nanotubes (MWCNTs) using a glucose-assisted hydrothermal method. It is found that the Ni3S2 nanoparticles deposited on MWCNTs disassemble into smaller components after the composite electrode is activated by the consecutive cyclic voltammetry scan in a 2 M KOH solution. Therefore, the active surface area of the Ni3S2 nanoparticles is increased, which further enhances the capacitive performance of the composite electrode. Because the synergistic effect of the Ni3S2 nanoparticles and MWCNTs on the capacitive performance of the composite electrode is pronounced, the composite electrode shows a high specific capacitance of 800 F/g and great cycling stability at a current density of 3.2 A/g. To examine the capacitive performance of the composite electrode in a full-cell configuration, an asymmetric supercapacitor device was fabricated by using the composite of Ni3S2 and MWCNTs as the cathode and activated carbon as the anode. The fabricated device can be operated reversibly between 0 and 1.6 V, and obtain a high specific capacitance of 55.8 F/g at 1 A/g, which delivers a maximum energy density of 19.8 Wh/kg at a power density of 798 W/kg. Furthermore, the asymmetric supercapacitor shows great stability based on the fact that the device retains 90% of its initial capacitance after a consecutive 5000 cycles of galvanostatic charge-discharge performed at a current density of 4 A/g.

Memory in a fractional-order cardiomyocyte model alters properties of alternans and spontaneous activity

NASA Astrophysics Data System (ADS)

Comlekoglu, T.; Weinberg, S. H.

2017-09-01

Cardiac memory is the dependence of electrical activity on the prior history of one or more system state variables, including transmembrane potential (Vm), ionic current gating, and ion concentrations. While prior work has represented memory either phenomenologically or with biophysical detail, in this study, we consider an intermediate approach of a minimal three-variable cardiomyocyte model, modified with fractional-order dynamics, i.e., a differential equation of order between 0 and 1, to account for history-dependence. Memory is represented via both capacitive memory, due to fractional-order Vm dynamics, that arises due to non-ideal behavior of membrane capacitance; and ionic current gating memory, due to fractional-order gating variable dynamics, that arises due to gating history-dependence. We perform simulations for varying Vm and gating variable fractional-orders and pacing cycle length and measure action potential duration (APD) and incidence of alternans, loss of capture, and spontaneous activity. In the absence of ionic current gating memory, we find that capacitive memory, i.e., decreased Vm fractional-order, typically shortens APD, suppresses alternans, and decreases the minimum cycle length (MCL) for loss of capture. However, in the presence of ionic current gating memory, capacitive memory can prolong APD, promote alternans, and increase MCL. Further, we find that reduced Vm fractional order (typically less than 0.75) can drive phase 4 depolarizations that promote spontaneous activity. Collectively, our results demonstrate that memory reproduced by a fractional-order model can play a role in alternans formation and pacemaking, and in general, can greatly increase the range of electrophysiological characteristics exhibited by a minimal model.

Fabrication of hierarchical porous nickel based metal-organic framework (Ni-MOF) constructed with nanosheets as novel pseudo-capacitive material for asymmetric supercapacitor.

PubMed

Du, Pengcheng; Dong, Yuman; Liu, Chang; Wei, Wenli; Liu, Dong; Liu, Peng

2018-05-15

Hierarchical porous nickel based metal-organic framework (Ni-MOF) constructed with nanosheets is fabricated by a facile hydrothermal process with the existence of trimesic acid and nickel ions. Various structures of Ni-MOFs can be obtained through adjusting the molar ratio of trimesic acid and nickel ion, the obtained hierarchical porous Ni-MOF exhibits optimal porous structure, which also possesses largest specific surface area. The hierarchical porous structure constructed with nanosheets can supply more active sites for electrochemical reactions to realize the excellent electrochemical properties, thus the hierarchical porous Ni-MOF reveals an outstanding specific capacitance of 1057 F/g at current density of 1 A/g, and delivers high specific capacitance of 649 F/g at current density of 30 A/g, indicating that it exhibits good rate capability of 63.4% even up to 30 A/g. The hierarchical porous Ni-MOF keeps 70% of its original value up to 2 500 charge-discharge cycles at the current density of 10 A/g. Furthermore, asymmetric supercapacitors (ASCs) were assembled based on hierarchical porous Ni-MOF and activated carbon (AC), the ASCs reveal specific capacitance of 87 F/g at current density of 0.5 A/g, and exhibit high energy density of 21.05 Wh/kg and power density of 6.03 kW/kg. Additionally, the tandem ASCs can light up a red LED. The hierarchical porous Ni-MOF exhibits promising applications in high performance supercapacitors. Copyright © 2018 Elsevier Inc. All rights reserved.

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.

Interface-state density estimation of n-type nanocrystalline FeSi2/p-type Si heterojunctions fabricated by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Nopparuchikun, Adison; Promros, Nathaporn; Sittimart, Phongsaphak; Onsee, Peeradon; Duangrawa, Asanlaya; Teakchaicum, Sakmongkon; Nogami, Tomohiro; Yoshitake, Tsuyoshi

2017-09-01

By utilizing pulsed laser deposition (PLD), heterojunctions comprised of n-type nanocrystalline (NC) FeSi2 thin films and p-type Si substrates were fabricated at room temperature in this study. Both dark and illuminated current density-voltage (J-V) curves for the heterojunctions were measured and analyzed at room temperature. The heterojunctions demonstrated a large reverse leakage current as well as a weak near-infrared light response. Based on the analysis of the dark forward J-V curves, at the V value  ⩽  0.2 V, we show that a carrier recombination process was governed at the heterojunction interface. When the V value was  >  0.2 V, the probable mechanism of carrier transportation was a space-charge limited-current process. Both the measurement and analysis for capacitance-voltage-frequency (C-V-f ) and conductance-voltage-frequency (G-V-f ) curves were performed in the applied frequency (f ) range of 50 kHz-2 MHz at room temperature. From the C-V-f and G-V-f curves, the density of interface states (N ss) for the heterojunctions was computed by using the Hill-Coleman method. The N ss values were 9.19  ×  1012 eV-1 cm-2 at 2 MHz and 3.15  ×  1014 eV-1 cm-2 at 50 kHz, which proved the existence of interface states at the heterojunction interface. These interface states are the probable cause of the degraded electrical performance in the heterojunctions. Invited talk at 5th Thailand International Nanotechnology Conference (Nano Thailand-2016), 27-29 November 2016, Nakhon Ratchasima, Thailand.

Superior supercapacitors based on nitrogen and sulfur co-doped hierarchical porous carbon: Excellent rate capability and cycle stability

NASA Astrophysics Data System (ADS)

Zhang, Deyi; Han, Mei; Wang, Bing; Li, Yubing; Lei, Longyan; Wang, Kunjie; Wang, Yi; Zhang, Liang; Feng, Huixia

2017-08-01

Vastly improving the charge storage capability of supercapacitors without sacrificing their high power density and cycle performance would bring bright application prospect. Herein, we report a nitrogen and sulfur co-doped hierarchical porous carbon (NSHPC) with very superior capacitance performance fabricated by KOH activation of nitrogen and sulfur co-doped ordered mesoporous carbon (NSOMC). A high electrochemical double-layer (EDL) capacitance of 351 F g-1 was observed for the reported NSHPC electrodes, and the capacitance remains at 288 F g-1 even under a large current density of 20 A g-1. Besides the high specific capacitance and outstanding rate capability, symmetrical supercapacitor cell based on the NSHPC electrodes also exhibits an excellent cycling performance with 95.61% capacitance retention after 5000 times charge/discharge cycles. The large surface area caused by KOH activation (2056 m2 g-1) and high utilized surface area owing to the ideal micro/mesopores ratio (2.88), large micropores diameter (1.38 nm) and short opened micropores structure as well as the enhanced surface wettability induced by N and S heteroatoms doping and improved conductivity induced by KOH activation was found to be responsible for the very superior capacitance performance.

Suppression of Leakage Current of Metal-Insulator-Semiconductor Ta2O5 Capacitors with Al2O3/SiON Buffer Layer

NASA Astrophysics Data System (ADS)

Tonomura, Osamu; Miki, Hiroshi; Takeda, Ken-ichi

2011-10-01

An Al2O3/SiO buffer layer was incorporated in a metal-insulator-semiconductor (MIS) Ta2O5 capacitor for dynamic random access memory (DRAM) application. Al2O3 was chosen for the buffer layer owing to its high band offset against silicon and oxidation resistance against increase in effective oxide thickness (EOT). It was clarified that post-deposition annealing in nitrogen at 800 °C for 600 s increased the band offset between Al2O3 and the lower electrode and decreased leakage current by two orders of magnitude at 1 V. Furthermore, we predicted and experimentally confirmed that there was an optimized value of y in (Si3N4)y(SiO2)(1-y), which is 0.58, for minimizing the leakage current and EOT of SiON. To clarify the oxidation resistance and appropriate thickness of Al2O3, a TiN/Ta2O5/Al2O3/SiON/polycrystalline-silicon capacitor was fabricated. It was confirmed that the lower electrode was not oxidized during the crystallization annealing of Ta2O5. By setting the Al2O3 thickness to 3.4 nm, the leakage current is lowered below the required value with an EOT of 3.6 nm.

Effects of doping on ferroelectric properties and leakage current behavior of KNN-LT-LS thin films on SrTiO3 substrate

NASA Astrophysics Data System (ADS)

Abazari, M.; Safari, A.

2009-05-01

We report the effects of Ba, Ti, and Mn dopants on ferroelectric polarization and leakage current of (K0.44Na0.52Li0.04)(Nb0.84Ta0.1Sb0.06)O3 (KNN-LT-LS) thin films deposited by pulsed laser deposition. It is shown that donor dopants such as Ba2+, which increased the resistivity in bulk KNN-LT-LS, had an opposite effect in the thin film. Ti4+ as an acceptor B-site dopant reduces the leakage current by an order of magnitude, while the polarization values showed a slight degradation. Mn4+, however, was found to effectively suppress the leakage current by over two orders of magnitude while enhancing the polarization, with 15 and 23 μC/cm2 remanent and saturated polarization, whose values are ˜70% and 82% of the reported values for bulk composition. This phenomenon has been associated with the dual effect of Mn4+ in KNN-LT-LS thin film, by substituting both A- and B-site cations. A detailed description on how each dopant affects the concentrations of vacancies in the lattice is presented. Mn-doped KNN-LT-LS thin films are shown to be a promising candidate for lead-free thin films and applications.

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.

Performance comparison between p–i–n and p–n junction tunneling field-effect transistors

NASA Astrophysics Data System (ADS)

Yoon, Young Jun; Seo, Jae Hwa; Kang, In Man

2018-06-01

In this study, we investigated the direct-current (DC) and radio-frequency (RF) performances of p–i–n and p–n junction tunneling field-effect transistors (TFETs). Compared to the p–i–n junction TFET, the p–n junction TFET exhibited higher on-state current (I on) because the channel formation mechanism of the p–n junction TFET resulted in a narrower tunneling barrier and an expanded tunneling area. Further, the reduction of I on of the p–n junction TFET by the interface trap was smaller. Moreover, the p–n junction TFET exhibited lower gate-to-drain capacitance (C gd) because a depletion capacitance (C gd,dep) was formed by the depletion region under gate dielectric. Consequently, the p–n junction TFET achieved an improvement of cut-off frequency (f T) and intrinsic delay time (τ), which are related to the current performance and total gate capacitance (C gg). We confirmed the enhancement of device performances in terms of I on, f T, and τ by the conduction mechanism of the p–n junction TFET.

Novel ultrathin Bi2O3 nanowires for supercapacitor electrode materials with high performance

NASA Astrophysics Data System (ADS)

Qiu, Yongfu; Fan, Hongbo; Chang, Xueyi; Dang, Haifeng; Luo, Qun; Cheng, Zhiyu

2018-03-01

In this paper, the ultrathin Bi2O3 nanowires are synthesized by an oxidative metal vapor transport deposition technique. Their diameters and length are about 10 nm and several tens of micrometers, the growth direction is along [101] and the specific surface area is about 7.34 m2 g-1. The galvanostatic charge-discharge measurement results show that the specific capacitances of the Bi2O3 nanowires-based electrodes increase with the decrease of the current densities. The maximum capacitance is 691.3 F g-1 at the current density of 2.0 A g-1. The Ragone plot shows that the Bi2O3 nanowires has excellent supercapacitive performance. Moreover, the cyclic stability is measured by the galvanostatic charge/discharge technique at a constant current density of 10.0 A g-1 in 6.0 M KOH electrolyte. The results show the excellent capacitance retention of 75.5% over 3000 cycles. In a word, the Bi2O3 nanowires should be the ideal potential electrode materials for low-costing and effective electrochemical supercapacitors.

Leakage current phenomena in Mn-doped Bi(Na,K)TiO{sub 3}-based ferroelectric thin films

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

Walenza-Slabe, J.; Gibbons, B. J., E-mail: brady.gibbons@oregonstate.edu

2016-08-28

Mn-doped 80(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}-20(Bi{sub 0.5}K{sub 0.5})TiO{sub 3} thin films were fabricated by chemical solution deposition on Pt/TiO{sub 2}/SiO{sub 2}/Si substrates. Steady state and time-dependent leakage current were investigated from room temperature to 180 °C. Undoped and low-doped films showed space-charge-limited current (SCLC) at high temperatures. The electric field marking the transition from Ohmic to trap-filling-limited current increased monotonically with Mn-doping. With 2 mol. % Mn, the current was Ohmic up to 430 kV/cm, even at 180 °C. Modeling of the SCLC showed that all films exhibited shallow trap levels and high trap concentrations. In the regime of steady state leakage, theremore » were also observations of negative differential resistivity and positive temperature coefficient of resistivity near room temperature. Both of these phenomena were confined to relatively low temperatures (below ∼60 °C). Transient currents were observed in the time-dependent leakage data, which was measured out to several hundred seconds. In the undoped films, these were found to be a consequence of oxygen vacancy migration modulating the electronic conductivity. The mobility and thermal activation energy for oxygen vacancies was extracted as μ{sub ion} ≈ 1.7 × 10{sup −12} cm{sup 2} V{sup −1} s{sup −1} and E{sub A,ion} ≈ 0.92 eV, respectively. The transient current displayed different characteristics in the 1 mol. % Mn-doped films which were not readily explained by oxygen vacancy migration.« less

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.

Bendable solid-state supercapacitors with Au nanoparticle-embedded graphene hydrogel films

PubMed Central

Yang, Kyungwhan; Cho, Kyoungah; Yoon, Dae Sung; Kim, Sangsig

2017-01-01

In this study, we fabricate bendable solid-state supercapacitors with Au nanoparticle (NP)-embedded graphene hydrogel (GH) electrodes and investigate the influence of the Au NP embedment on the internal resistance and capacitive performance. Embedding the Au NPs into the GH electrodes results in a decrease of the internal resistance from 35 to 21 Ω, and a threefold reduction of the IR drop at a current density of 5 A/g when compared with GH electrodes without Au NPs. The Au NP-embedded GH supercapacitors (NP-GH SCs) exhibit excellent capacitive performances, with large specific capacitance (135 F/g) and high energy density (15.2 W·h/kg). Moreover, the NP-GH SCs exhibit comparable areal capacitance (168 mF/cm2) and operate under tensile/compressive bending. PMID:28074865

Freestanding polyaniline nanorods grown on graphene for highly capacitive energy storage

NASA Astrophysics Data System (ADS)

Li, Zijiong; Qin, Zhen; Yang, Baocheng; Guo, Jian; Wang, Haiyan; Zhang, Weiyang; Lv, Xiaowei; Stack, Alison

2015-02-01

Freestanding polyaniline (PANI) nanorods grown in situ on microwave-expanded graphene oxide (MEGO) sheets were prepared through a facile solution method. The morphological characterization indicates that large quantity of free-standing PANI nanorods with average diameter of 50 nm were uniformly deposited onto the double sides of the MEGO nanosheets to form a sandwich structure. The hybrid of PANI/MEGO (GPANI) exhibit high specific surface area and high electrical conductivity, compared with pristine PANI nanorods. When evaluated as electrodes for supercapacitors, the GPANI demonstrate high specific capacitance of 628 F g-1 at a current density of 1.1 A g-1, high-rate performance, and excellent cycle stability compared to individual component. Such excellent electrochemical performance should be attributed to the combined double-layer capacitance and pseudo -capacitance mechanisms from the MEGO sheets and PANI nanorods.

On Machine Capacitance Dimensional and Surface Profile Measurement System

NASA Technical Reports Server (NTRS)

Resnick, Ralph

1993-01-01

A program was awarded under the Air Force Machine Tool Sensor Improvements Program Research and Development Announcement to develop and demonstrate the use of a Capacitance Sensor System including Capacitive Non-Contact Analog Probe and a Capacitive Array Dimensional Measurement System to check the dimensions of complex shapes and contours on a machine tool or in an automated inspection cell. The manufacturing of complex shapes and contours and the subsequent verification of those manufactured shapes is fundamental and widespread throughout industry. The critical profile of a gear tooth; the overall shape of a graphite EDM electrode; the contour of a turbine blade in a jet engine; and countless other components in varied applications possess complex shapes that require detailed and complex inspection procedures. Current inspection methods for complex shapes and contours are expensive, time-consuming, and labor intensive.

Energy relaxation mechanisms in capacitively shunted flux qubits

NASA Astrophysics Data System (ADS)

Corcoles, Antonio; Rozen, Jim; Rothwell, Mary Beth; Keefe, George; di Vincenzo, David; Ketchen, Mark; Chow, Jerry; Rigetti, Chad; Rohrs, Jack; Borstelmann, Mark; Steffen, Matthias; IBM Quantum Computing Group Team

2011-03-01

Energy losses in superconducting qubits remain a major object of study in the road towards scalable, highly coherent qubit devices. The current understanding of the loss mechanisms in these devices is far from being complete and it is sometimes difficult to experimentally separate the different contributions to decoherence. Here we compare a traditional three Josephson-junction flux qubit to the recently implemented capacitively shunted flux qubit, whose energy decay is thought to be limited by dielectric losses arising from native oxides in the shunting capacitor. Keeping all parameters identical except for the shunting capacitance, we obtain energy relaxation times that are comparable for both types of qubit. This suggests that the energy relaxation time is not limited by junction losses in capacitively shunted flux qubits. We discuss some other possible loss mechanisms present in these devices.

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.

Three-dimensional cross-linked carbon network wrapped with ordered polyaniline nanowires for high-performance pseudo-supercapacitors

NASA Astrophysics Data System (ADS)

Hu, Huan; Liu, Shuwu; Hanif, Muddasir; Chen, Shuiliang; Hou, Haoqing

2014-12-01

The polyaniline (PANI)-based pseudo-supercapacitor has been extensively studied due to its good conductivity, ease of synthesis, low-cost monomer, tunable properties and remarkable specific capacitance. In this work, a three-dimensional cross-linked carbon network (3D-CCN) was used as a contact-resistance-free substrate for PANI-based pseudo-supercapacitors. The ordered PANI nanowires (PaNWs) were grown on the 3D-CCN to form PaNWs/3D-CCN composites by in-situ polymerization. The PaNWs/3D-CCN composites exhibited a specific capacitance (Cs) of 1191.8 F g-1 at a current density of 0.5 A g-1 and a superior rate capability with 66.4% capacitance retention at 100.0 A g-1. The high specific capacitance is attributed to the thin PaNW coating and the spaced PANI nanowire array, which ensure a higher utilization of PANI due to the ease of diffusion of protons through/on the PANI nanowires. In addition, the unique 3D-CCN was used as a high-conductivity platform (or skeleton) with no contact resistance for fast electron transfer and facile charge transport within the composites. Therefore, the binder-free composites can process rapid gains or losses of electrons and ions, even at a high current density. As a result, the specific capacitance and rate capability of our composites are remarkably higher than those of other PANI composites.

Three-Dimensional Hierarchical NixCo1-xO/NiyCo2-yP@C Hybrids on Nickel Foam for Excellent Supercapacitors.

PubMed

Shao, Yubo; Zhao, Yongqing; Li, Hua; Xu, Cailing

2016-12-28

Active materials and special structures of the electrode have decisive influence on the electrochemical properties of supercapacitors. Herein, three-dimensional (3D) hierarchical Ni x Co 1-x O/Ni y Co 2-y P@C (denoted as NiCoOP@C) hybrids have been successfully prepared by a phosphorization treatment of hierarchical Ni x Co 1-x O@C grown on nickel foam. The resulting NiCoOP@C hybrids exhibit an outstanding specific capacitance and cycle performance because they couple the merits of the superior cycling stability of Ni x Co 1-x O, the high specific capacitance of Ni y Co 2-y P, the mechanical stability of carbon layer, and the 3D hierarchical structure. The specific capacitance of 2638 F g -1 can be obtained at the current density of 1 A g -1 , and even at the current density of 20 A g -1 , the NiCoOP@C electrode still possesses a specific capacitance of 1144 F g -1 . After 3000 cycles at 10 A g -1 , 84% of the initial specific capacitance is still remained. In addition, an asymmetric ultracapacitor (ASC) is assembled through using NiCoOP@C hybrids as anode and activated carbon as cathode. The as-prepared ASC obtains a maximum energy density of 39.4 Wh kg -1 at a power density of 394 W kg -1 and still holds 21 Wh kg -1 at 7500 W kg -1 .

MOF-Derived Hollow Cage Nix Co3-x O4 and Their Synergy with Graphene for Outstanding Supercapacitors.

PubMed

Jayakumar, Anjali; Antony, Rajini P; Wang, Ronghua; Lee, Jong-Min

2017-03-01

Highly optimized nickel cobalt mixed oxide has been derived from zeolite imidazole frameworks. While the pure cobalt oxide gives only 178.7 F g -1 as the specific capacitance at a current density of 1 A g -1 , the optimized Ni:Co 1:1 has given an extremely high and unprecedented specific capacitance of 1931 F g -1 at a current density of 1 A g -1 , with a capacitance retention of 69.5% after 5000 cycles in a three electrode test. This optimized Ni:Co 1:1 mixed oxide is further used to make a composite of nickel cobalt mixed oxide/graphene 3D hydrogel for enhancing the electrochemical performance by virtue of a continuous and porous graphene conductive network. The electrode made from GNi:Co 1:1 successfully achieves an even higher specific capacitance of 2870.8 F g -1 at 1 A g -1 and also shows a significant improvement in the cyclic stability with 81% capacitance retention after 5000 cycles. An asymmetric supercapacitor is also assembled using a pure graphene 3D hydrogel as the negative electrode and the GNi:Co 1:1 as the positive electrode. With a potential window of 1.5 V and binder free electrodes, the capacitor gives a high specific energy density of 50.2 Wh kg -1 at a high power density of 750 W kg -1 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile Co-Electrodeposition Method for High-Performance Supercapacitor Based on Reduced Graphene Oxide/Polypyrrole Composite Film.

PubMed

Chen, Junchen; Wang, Yaming; Cao, Jianyun; Liu, Yan; Zhou, Yu; Ouyang, Jia-Hu; Jia, Dechang

2017-06-14

A facile co-electrodeposition method has been developed to fabricate reduced graphene oxide/polypyrrole (rGO/PPy) composite films, with sodium dodecyl benzene sulfonate as both a surfactant and supporting electrolyte in the precursor solution. The introduction of rGO into the PPy films forms porous structure and enhances the conductivity across the film, leading to superior electrochemical performance. By controlling the deposition time and rGO concentration, the highest area capacitance can reach 411 mF/cm 2 (0.2 mA/cm 2 ) for rGO/PPy films, whereas optimized specific capacitance is as high as 361 F/g (0.2 mA/cm 2 ). All of the composite films exhibit excellent rate capability (at least 175 F/g at the current density of 12 mA/cm 2 ) compared with pure PPy film (only 12 F/g at the current density of 12 mA/cm 2 ). The rGO/PPy composite exhibits excellent cycling stability that maintains 104% of its initial capacitance after cycling for 2000 cycles and 80% for 5000 cycles. The two-electrode solid-state supercapacitor (SC) based on rGO/PPy composite electrodes demonstrates good rate performance, excellent cycling stability, as well as a high area capacitance of 222 mF/cm 2 . The solid-state planar SC based on the rGO/PPy composite exhibits an area capacitance of 9.4 mF/cm 2 , demonstrating great potential for fabrication of microsupercapacitors.

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.

Static charge outside chamber induces dielectric breakdown of solid-state nanopore membranes

NASA Astrophysics Data System (ADS)

Matsui, Kazuma; Goto, Yusuke; Yanagi, Itaru; Yanagawa, Yoshimitsu; Ishige, Yu; Takeda, Ken-ichi

2018-04-01

Reducing device capacitance is effective for decreasing current noise observed in a solid-state nanopore-based DNA sequencer. On the other hand, we have recently found that voltage stress causes pinhole-like defects in such low-capacitance devices. The origin of voltage stress, however, has not been determined. In this research, we identified that a dominant origin is static charge on the outer surface of a flow cell. Even though the outer surface was not in direct contact with electrolytes in the flow cell, the charge induces high voltage stress on a membrane according to the capacitance coupling ratio of the flow cell to the membrane.