Stable Open Circuit Research Articles

Indium–Gallium–Zinc Oxide Thin-Film Transistor-Based Scan Driver Circuit Using Separate Driving Structure for Multiple Output Signals

This article proposes a scan driver circuit based on indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs) for multiple output signals. The proposed circuit could generate two overlapped output signals using a separate driving structure. The separate driving structure enabled the control nodes of each output signal to have a sufficiently high voltage during the output period. Consequently, the proposed circuit stably operated with the threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}_{\text{TH}}\text{)}$</tex-math> </inline-formula> varying from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 3 to 4 V in the circuit simulation. The proposed scan driver circuit could reduce the circuit area because a single stage could output two output signals for two adjacent scan lines. Furthermore, the fabricated scan driver circuit exhibited a stable operation with multiple overlapped signals. Consequently, the proposed IGZO TFT-based scan driver circuit showed a stable circuit operation with multiple output signals through the separate driving structure.

Improving stability in two-dimensional transistors with amorphous gate oxides by Fermi-level tuning

Electronic devices based on two-dimensional semiconductors suffer from limited electrical stability because charge carriers originating from the semiconductors interact with defects in the surrounding insulators. In field-effect transistors, the resulting trapped charges can lead to large hysteresis and device drifts, particularly when common amorphous gate oxides (such as silicon or hafnium dioxide) are used, hindering stable circuit operation. Here, we show that device stability in graphene-based field-effect transistors with amorphous gate oxides can be improved by Fermi-level tuning. We deliberately tune the Fermi level of the channel to maximize the energy distance between the charge carriers in the channel and the defect bands in the amorphous aluminium gate oxide. Charge trapping is highly sensitive to the energetic alignment of the Fermi level of the channel with the defect band in the insulator, and thus, our approach minimizes the amount of electrically active border traps without the need to reduce the total number of traps in the insulator.

Applications of Electrochromic Copolymers Based on Tris(4-carbazoyl-9-ylphenyl)amine and Bithiophene Derivatives in Electrochromic Devices.

Four copolymers (P(tCz (tris(4-carbazoyl-9-ylphenyl)amine)-co-bTP (2,2′-bithiophene)), P(tCz-co-CPDT (4H-cyclopenta[2,1-b:3,4-b’]dithiophene)), P(tCz-co-DTC (3,6-di(2-thienyl)carbazole)), and P(tCz-co-CPDTK (cyclopentadithiophene ketone))) are deposited on indium tin oxide (ITO) surfaces using electrochemical polymerization. Spectroelectrochemical properties of copolymer electrodes reveal that the colors of P(tCz-co-bTP) film are pinkish-orange, light olive green, light grayish blue, and dark blue at 0.0, 0.8, 1.2, and 1.6 V, respectively, whereas the color variations of P(tCz-co-CPDTK) film are light yellow, yellow, and blue at 0.0 V, 0.8 V, and 1.5 V, respectively. The ΔT of P(tCz-co-bTP), P(tCz-co-CPDT), P(tCz-co-DTC), and P(tCz-co-CPDTK) films are estimated to be 43.0% at 967 nm, 28.7% at 864 nm, 43.6% at 870 nm, and 24.5% at 984 nm, respectively. Five electrochromic devices (ECDs) are assembled using the tCz-based homopolymer and copolymers as coloring electrodes, and poly(2,2-dimethyl-3,4-propylenedioxythiophene) (PProDOT-Me2) as the complementary electrode. P(tCz-co-DTC)/PProDOT-Me2 ECD reveals high transmittance change (45.9% at 624 nm), P(tCz-co-CPDTK)/PProDOT-Me2 ECD shows high η (513.0 cm2 C−1 at 582 nm), and P(tCz-co-bTP)/PProDOT-Me2 ECD presents short switching time (less than 0.4 s) at 628 nm. Moreover, these ECDs show satisfactory redox stability and open circuit stability.

VHF 및 UHF 대역 소형 안테나 매칭성능 개선을 위한 비 포스터 정합회로 설계

Herein, a non-Foster matching circuit is designed to improve the impedance matching characteristics of small antennas in the VHF and UHF bands. The proposed non-Foster circuit is designed to operate with negative capacitance in a wide frequency band from 50 MHz to 1,000 MHz for use in various communication bands. To ensure the stability of the non-Foster circuit with conditional stability, the open-circuit stability condition of Linvill was satisfied, and the circuit was fabricated using the FR-4 substrate. The fabricated non-Foster circuit was combined with a small antenna to verify its performance by measuring the return loss and received power in the FM, DMB, and GSM bands. The measured return loss was improved from −6 dB to −30 dB, and the measured received power was improved from 0.5 dBm to 5.2 dBm.

Three-Phase PV CHB Inverter for a Distributed Power Generation System

This work deals with the design of a three-phase grid-tied photovoltaic (PV) cascade H-bridge inverter for distributed power conversion. The power balancing among the phases must be properly addressed. In fact, an intra-phase power imbalance—arising from uneven irradiance and temperature conditions—generates a per-phase power imbalance. This latter can be compensated by the injection of a proper zero-sequence voltage, while the intra-phase balance is ensured by means of a hybrid modulation method which is able to guarantee the handling of unequal DC (Direct Current) sources, stable circuit operation, and maximization of PV power production. The digital controller is developed and tested in Matlab/Simulink environment integrated with XSG (Xilinx System Generator), thus allowing an easy transfer on a field-programmable gate array (FPGA) platform and accurately describing the behavior of a real hardware implementation. Thus, numerical results have been considered to prove the effectiveness of the proposed approach.

Electrical Characterization of a 4H-SiC JFET Wafer: DC Parameter Variations for Extreme Temperature IC Design

This work reports DC electrical characterization of a 76 mm diameter 4H-SiC JFET test wafer fabricated as part of NASA’s on-going efforts to realize medium-scale ICs with prolonged and stable circuit operation at temperatures as high as 500 °C. In particular, these measurements provide quantitative parameter ranges for use in JFET IC design and simulation. Larger than expected parameter variations were observed both as a function of position across the wafer as well as a function of ambient testing temperature from 23 °C to 500 °C.

Verification of Stable Circuit Operation of 180nm Current Controlled MOS Current Mode Logic under Threshold Voltage Fluctuation

We have succeeded in fabricating 180nm Current Controlled MOS Current Mode Logic (CC-MCML) and verified the stable circuit operation of 180nm CC-MCML under threshold voltage fluctuations by measurement. The performance stability of the CC-MCML inverter under the fluctuations of threshold voltage of NMOS and PMOS is evaluated from the viewpoint of diminishing the bias offset voltage ΔVB. The ΔVB, that is defined as (base voltage of output waveform) - (base voltage of input waveform), is a key design parameter for differential circuit. It is shown that when the threshold voltage of NMOS fluctuates in the range of 0.53V to 0.69V, and threshold voltage of PMOS fluctuates in the range of -0.47V to -0.67V, the CC-MCML technique is able to suppress ΔVB within only 30mV, where as the conventional MCML technique caused maximum ΔVB of 1.0V. In this paper, it is verified for the first time that the fabricated CC-MCML is more tolerant against the fluctuations of threshold voltages than the conventional MCML.

Synthesis and electropolymerization of 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7- b]quinoxaline and its electrochromic properties

Synthesis of a new thiophene-based monomer; 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7- b]quinoxaline (DDQ), was realized. The chemical structure of the monomer was characterized by 1H NMR, FTIR and mass spectroscopy techniques. Electrochemical polymerization of DDQ and characterization of the resulting polymer [P(DDQ)] was performed. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. P(DDQ) has a low oxidation potential (0.9 V) and low band gap (1.73 eV) compared to polythiophene. In addition, dual-type polymer electrochromic device (ECD) based on P(DDQ) with poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry, electrochromic switching, stability and open-circuit stability of the device were studied. It was observed that polymer have good switching time, reasonable contrast and optical memory.

Electrochemical synthesis of poly(3-bromo-4-methoxythiophene) and its device application

Abstract A functionalized thiophene containing both an electron withdrawing and an electron donating group, 3-bromo-4-methoxythiophene (BrMeOTh) was succesfully polymerized in acetonitrile containing 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) electrolyte via electrochemical oxidation of the corresponding monomer. BrMeOTh exhibits a lower oxidation potential (1.68 V vs Ag/AgCl) than thiophene (2.05 V vs Ag/AgCl). Spectroelectrochemical properties of poly(3-bromo-4-methoxythiophene) (PBrMeOTh) was investigated in situ recording the electronic absorption spectra of the polymer film coated on indium-tin oxide (ITO) at various potentials. The maximum transmittance difference between the oxidized and reduced states was measured as 39.2% and the time required to attain 90% of the total transmittance difference was found to be 1.2 s. Both cyclic voltammetric and spectroelectrochemical studies showed that the polymer exhibit a lower oxidation potential, a relatively narrow band gap, a stable conducting state and a higher degree of electrochemical reversibility. It is also found that, as synthesized PBrMeOTh films possess a linear structure along the polymer backbone. Moreover, dual type electrochromic device of PBrMeOTh with poly(3,4-diethylenedioxythiohene) (PEDOT) was constructed and its spectroelectrochemical, electrochromic switching and open circuit stability were investigated. Dual electrochromic device showed a good optical contrast and distinctive color changes with the ability of good switching times (1.1 s) under atmospheric pressure.

A soluble and multichromic conducting polythiophene derivative

A new soluble polythiophene derivative was synthesized by both chemical and electrochemical oxidative polymerization of 1-4-nitrophenyl-2,5-di(2-thienyl)-1 H-pyrrole (SNSNO 2). Chemical method produces a polymer which is completely soluble in organic solvents. The structures of both the monomer and the soluble polymer were elucidated by 1H and 13C-NMR and FTIR. The average molecular weight has been determined by GPC to be Mn = 6.3 × 10 3 for the chemically synthesized polymer. P(SNSNO 2) was also synthesized via potentiostatic electrochemical polymerization. Characterizations of the resulting polymer were performed by cyclic voltammetry CV, FTIR and UV–Vis spectroscopy. Four-probe technique was used to measure the conductivities of the samples. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. In addition, dual type polymer electrochromic devices ECDs based on P(SNSNO 2) with poly3,4-ethylenedioxythiophene (PEDOT) were constructed. Spectroelectrochemistry, electrochromic switching and open circuit stability of the devices were studied. They were found to have good switching times, reasonable contrasts and optical memories.

Synthesis and characterization of a new soluble conducting polymer and its electrochromic devices

Abstract A new polythiophene derivative was synthesized by both chemical and electrochemical oxidative polymerization of 1-(perfluorophenyl)-2,5-di(2-thienyl)-1 H -pyrrole (FPTPy). The structures of both the monomer and the soluble polymer were elucidated by nuclear magnetic resonance ( 1 H-NMR) and fourier transform infrared (FTIR). Polymer of FPTPy was also synthesized via potentiostatic electrochemical polymerization in acetonitrile (AN)/NaClO 4 /LiClO 4 (0.1 M:0.1 M) solvent–electrolyte couple. Characterizations of the resulting insoluble polymer were performed by cyclic voltammetry (CV), FTIR, scanning electron microscopy (SEM) and UV–Vis Spectroscopy. Four-probe technique was used to measure the conductivities of the samples. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. In addition, dual type polymer electrochromic devices (ECDs) based on P(FPTPy) with poly(3,4-ethylenedioxythiophene) (PEDOT) were constructed. Spectroelectrochemistry, electrochromic switching and open circuit stability of the devices were studied. They were found to have good switching times, reasonable contrasts and optical memories.

A soluble conducting polymer: 1-Phenyl-2,5-di(2-thienyl)-1H-pyrrole and its electrochromic application

A thiophene-functionalized monomer 1-phenyl-2,5-di(2-thienyl)-1H-pyrrole (PTP) was synthesized. The chemical polymerization of PTP (CPTP) was realized by using FeCl 3 as the oxidant. The structures of both the monomer and the soluble polymer (CPTP) were investigated by Nuclear Magnetic Resonance ( 1H and 13C NMR) and Fourier Transform Infrared (FTIR). The average molecular weight of the chemically synthesized polymer was determined by gel permeation chromatography (GPC) as Mn = 7.2 × 10 3. The electrochemical oxidative polymerization of PTP was carried out via constant-potential electrolysis. Characterizations of the resulting polymer were done by cyclic voltammetry (CV), FTIR, Scanning Electron Microscopy (SEM) and UV–vis Spectroscopy. The conductivity of sample was measured by four-probe technique. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. Spectroelectrochemical analysis of P(PTP) revealed electronic transitions at 413, 577 and 884 nm corresponding to π–π * transition, polaron, and bipolaron band formations, respectively. Kinetic studies evaluated the switching ability of the P(PTP); the percent transmittance T% was found as 27%. The homopolymer of PTP was used to construct dual-type polymer electrochromic devices (ECDs) against poly(3,4-ethylenedioxythiophene) (PEDOT). Spectroelectrochemistry, electrochromic switching and open circuit stability of the devices were investigated.

Open Circuit Stability of Underpotentially Deposited Pb Layer on Cu (111) Face An Experimental and Modeling Study

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A new soluble conducting polymer and its electrochromic devices

AbstractA new polythiophene derivative was synthesized by both chemical and electrochemical oxidative polymerization of 1‐(1‐phenylethyl)‐2,5‐di(2‐thienyl)‐1H‐pyrrole (PETPy). Of which the chemical method produces a polymer that is completely soluble in organic solvents. The structures of both the monomer and the soluble polymer were elucidated by nuclear magnetic resonance (1H and 13C NMR) and Fourier transform infrared (FTIR) spectroscopy. The average molecular weight has been determined by gel permeation chromatography to be Mn = 3.29 × 103 for the chemically synthesized polymer. Polymer of PETPy was synthesized via potentiostatic electrochemical polymerization in acetonitrile (AN)/NaClO4/LiClO4 (0.1 M) solvent–electrolyte couple. Characterizations of the resulting polymer were performed by cyclic voltammetry, FTIR, scanning electron microscopy, and UV–vis spectroscopy. Four‐probe technique was used to measure the conductivities of the samples. Moreover, the spectroelectrochemical and electrochromic properties of the polymer films were investigated. In addition, dual‐type polymer electrochromic devices based on P(PETPy) with poly(3,4‐ethylenedioxythiophene) were constructed. Spectroelectrochemistry, electrochromic switching, and open circuit stability of the devices were studied. They were found to have good switching times, reasonable contrasts, and optical memories. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2215–2225, 2006

Synthesis and electrochromic properties of conducting copolymers of dioxocino- and dithiocino-quinoxalines with bithiophene

Abstract Two new monomers, 2-benzyl-5,12-dihydro-2 H -pyrrolo[3′,4′:2,3][1,4]dioxocino[6,7- b ]quinoxaline (DPOQ) and 5,12-dihydrothieno[3′,4′:2,3][1,4]dithiocino[6,7- b ]quinoxaline (DTTQ), were synthesized. The chemical structures of the monomers were characterized by nuclear magnetic resonance ( 1 H NMR), Fourier transform infrared (FTIR) and mass spectra. Copolymer of DPOQ with bithiophene (BT) was synthesized via potentiostatic electrochemical polymerization in acetonitrile–tetrabutylammonium tetrafluoroborate solvent–electrolyte couple. For DTTQ, copolymerization with bithiophene was achieved via potentiodynamic method in dichloromethane–tetrabutylammonium hexafluorophosphate solvent–electrolyte couple. Characterizations of the resulting copolymers were performed by cyclic voltammetry (CV), FTIR, scanning electron microscopy (SEM) and UV–Vis spectroscopy. Four-probe technique was used to measure the conductivities of the samples. Moreover, the spectroelectrochemical and electrochromic properties of the copolymer films were investigated. In addition, dual type polymer electrochromic devices based on P(DPOQ-co-BT) and P(DTTQ-co-BT) with poly(3,4-ethylenedioxythiophene) were constructed. Spectroelectrochemistry, electrochromic switching and open circuit stability of the devices were studied. They were found to have good switching times, reasonable contrasts and optical memories.

Open circuit stability of underpotentially deposited Pb monolayer on Cu(1 1 1)

The stability of underpotentially deposited (UPD) Pb layer on Cu(1 1 1) is investigated by conventional electrochemical techniques in perchlorate solution at open circuit potential (OCP). In situ scanning tunneling microscopy (STM) is employed to monitor and ascertain structural and morphological changes at characteristic potentials. A corrosion-like mechanism associated with UPD layer stripping powered by reduction processes is found to operate in the system of interest in absence of potential control. OCP transients suggest strong dependence of the Pb layer stability upon the concentration of oxidizing agents, such as oxygen and/or nitrate ions, present in the solution. It is found that the increase of the oxidizing agent concentration results in a proportional decrease of the Pb UPD layer stripping time at OCP. The concentration of the dissolved oxygen is found to affect the UPD layer behavior in the entire range of underpotentials in accordance with the strong affinity of the Pb 2+/Cu(1 1 1) system to the oxygen reduction reaction (ORR). In contrast to oxygen, nitrate ions appear to play active role only in the potential range positive to the UPD peaks where mostly bare Cu surface is in contact with the solution. Specifically adsorbing Cl − ions are examined as a possible inhibitor of the reduction processes operating in the Pb underpotential range. Concentrations of Cl − ions as low as 1 × 10 −4 M are found to stabilize the Pb UPD layer by a factor of 2.5.

SiC JMOSFETs for High-Temperature Stable Circuit Operation

4H-SiC junction-gated and metal-oxide-semiconductor field effect transistors (JMOSFETs) have been fabricated for high temperature stable circuit operation. The JMOSFETs have shown the feasibility for operating with constant on and off current levels from room temperature up to 300 degreesC. Moreover, by accumulating the channel using the MOS gate, over 2.5 times higher current density than normal JFET operation has been achieved. The temperature dependent I-V and the sub-threshold characteristics have been studied by using 2-dimensional simulation.

Combination of JFET and MOSFET devices in 4H-SiC for high-temperature stable circuit operation

A novel combination of junction-gated and metal-oxide-semiconductor field effect transistor (JMOSFET) has been fabricated and characterised in 4H-SiC. The high-temperature stable operation of JMOSFETs has been explored in terms of constant current levels. The JMOSFETs have shown the feasibility for operating with constant on and off current levels from room temperature up to 300/spl deg/C. Another advantage of this device is the improved current density by accumulation of the MOS n-channel.

A 3.2 GHz 26 dB wide-band monolithic matched GaAs MESFET feedback amplifier using cascodes

Feedback around cascode stages is demonstrated to be a useful means of making matched direct coupled amplifiers with higher bandwidths than afforded by conventional common-source topologies. Design techniques are described for an amplifier which is capable of operation to DC and which exhibits a measured gain of 26 dB, a 3.2 GHz bandwidth, and a 2.5:1 VSWR in a 1- mu m GaAs MESFET process. A novel adjustment scheme is introduced whereby the amplifier's frequency response can be modified using a DC bias voltage to ensure stable circuit operation in spite of MESFET modeling inaccuracies and GaAs processing variations. >

Nature of passive films on Fe26Cr alloy

Anodic oxide films formed on Fe26Cr alloy in pH 2.0 H 2SO 4 solution have been investigated using electrochemical techniques, and Auger electron spectroscopy (AES) combined with ion sputtering and subsequent quantitative thin film analysis. Films formed on electropolished (EP) and cathodically reduced (CR) surfaces have been examined in terms of their thickness, composition and open-circuit stability as a function of potential and time of anodization. Passive films on CR surfaces appear to be composed of either a (Fe,Cr) 2O 3 type of oxide, or an inner layer of FeCr 2O 4 and an outer layer of (Fe,Cr) 2O 3 depending on the anodizing potential. The Cr/Fe ratio in the films varied with both potential and time of anodization, but all films were enriched in Cr relative to the underlying alloy. Oxide thicknesses were ≈17 A ̊ (±5−10%) irrespective of the conditions of formation. The somewhat thicker EP prior oxide contained Cl − which was removed by CR. If no CR was performed, subsequent passive films on EP surfaces contained various amounts of incorporated Cl − depending on the anodizing potential. The Cl −-containing films were also Cr rich, and their composition and thickness were potential dependent. Open-circuit decay profiles and surface reactivity measurements demonstrated that the Cl −-containing films break down faster than Cl −-free anodic films with preferential removal of Fe and Cl − occurring from the outer part of the film. The stability of both types of film increased with time of anodization.