Search

In this work, we simulated the smallest fullerene molecule, C20 in a two-probe device model with gold electrodes. The gold electrodes comprised of (011) miller planes were carved to construct the novel geometry based four unique shapes, which were strung to fullerene molecules through mechanically controlled break junction techniques. The organized devices were later scrutinized using non-equilibrium Green's function based on the density functional theory to calculate their molecular orbitals, energy levels, charge transfers, and electrical parameters. After intense scrutiny, we concluded that five-edged and six-edged devices have the lowest and highest current-conductance values, which result from their electrode-dominating and electrode-subsidiary effects, respectively. However, an interesting observation was that the three-edged and four-edged electrodes functioned as semi-metallic in nature, allowing the C20 molecule to demonstrate its performance with the complementary effect of these electrodes in the electron conduction process of a two-probe device. [ABSTRACT FROM AUTHOR]

We report ab initio calculations of electronic transport properties of heterostructure based on MoS2 nanoribbons. The heterostructure consists of edge hydrogen-passivated and non-passivated zigzag MoS2 nanoribbons (ZMoS2NR-H/ZMoS2NR). Our calculations show that the heterostructure has half-metallic behavior which is independent of the nanoribbon width. The opening of spin channels of the heterostructure depends on the matching of particular electronic orbitals in the Mo-dominated edges of ZMoS2NR-H and ZMoS2NR. Perfect spin filter effect appears at small bias voltages, and large negative differential resistance and rectifying effects are also observed in the heterostructure. [ABSTRACT FROM AUTHOR]

A wideband common-gate CMOS low noise amplifier with negative resistance technique is proposed. A novel single-ended negative resistance structure is employed to improve gain and noise of the LNA. The inductor resonating is adopted at the input stage and load stage to meet wideband matching and compensate gain roll-off at higher frequen- cies. Implemented in a 0.18 μm CMOS technology, the proposed LNA demonstrates in simulations a maximal gain of 16.4 dB across the 3 dB bandwidth of 0.2-3 GHz. The in-band noise figure of 3.4-4.7 dB is obtained while the IIP3 of 5.3-6.8 dBm and IIP2 of 12.5-17.2 dBm are post-simulated in the designed frequency band. The LNA core consumes a power dissipation of 3.8 mW under a 1.5 V power supply. [ABSTRACT FROM AUTHOR]

A 90-96 GHz down-conversion mixer for 94 GHz image radar sensors using standard 90 nm CMOS technology is reported. RF negative resistance compensation technique, i.e. NMOS LC-oscillator-based RF transconductance (GM) stage load, is used to increase the output impedance and suppress the feedback capacitance C of RF GM stage. Hence, conversion gain (CG), noise figure (NF) and LO-RF isolation of the mixer can be enhanced. The mixer consumes 15 mW and achieves excellent RF-port input reflection coefficient of −10 to −36.4 dB for frequencies of 85-105 GHz. The corresponding -10 dB input matching bandwidth is 20 GHz. In addition, for frequencies of 90-96 GHz, the mixer achieves CG of 6.3-9 dB (the corresponding 3-dB CG bandwidth is greater than 6 GHz) and LO-RF isolation of 40-45.1 dB, one of the best CG and LO-RF isolation results ever reported for a down-conversion mixer with operation frequency around 94 GHz. Furthermore, the mixer achieves an excellent input third-order intercept point of 1 dBm at 94 GHz. These results demonstrate the proposed down-conversion mixer architecture is very promising for 94 GHz image radar sensors. [ABSTRACT FROM AUTHOR]

In this paper, we show a validation of our compact model for negative capacitance FET (NCFET) presented in Part I. The model is thoroughly validated with the TCAD simulations with respect to ferroelectric thickness scaling and temperature effects. Interestingly, we find that an NCFET with PZT ferroelectric of a large thickness provides a negative output differential resistance in addition to an expected high ON current and a sub-60 mV/decade subthreshold swing. The model is also tested for the Gummel symmetry and its transient capabilities are highlighted through a ring oscillator circuit simulation. [ABSTRACT FROM PUBLISHER]

A fully integrated 24-GHz Gilbert-cell mixer incorporating two on-chip Marchand baluns to convert single-ended signals into differential signals is presented in this paper. One is a passive balun at local oscillator (LO) port to improve isolation between the LO and radio-frequency (RF) ports, and the other is an active balun at RF port to enhance the conversion gain (CG) of the down-conversion mixer. The active balun utilizes complementary cross-coupled pairs (CCPs) to compensate for its resistive losses. Moreover, the gate-to-source capacitances ( $C_{{\text {gs}}} ) of the CCPs are also absorbed into coupled lines and then reduce the chip size. The chip area of the active balun is about one quarter of the passive one. The mixer is designed and implemented in a 0.18- \mu \textm CMOS technology, and its chip size is 0.38 mm2 including all testing pads. With a power consumption of 18.9 mW and an LO power of 0 dBm, the mixer exhibits a measured CG of 12.8 dB, an input P{\mathrm {in,1~dB}} of −14.5 dBm, and LO-RF isolations better than 43 dB. [ABSTRACT FROM PUBLISHER]

An instability suppressor circuit for self-pulsing direct current (DC) driven microplasma discharge is proposed and experimentally tested over a range of pd values for helium feed gas. The external circuit configuration suppresses self-pulsing of the discharge, extending the normal glow regime to lower currents. The negative differential resistance (NDR) region was observed to shift further left in the voltage–current parametric space (i.e., lower current), and the slope of the NDR region was decreased substantially. In addition, the suppressor element decreased the pulsing frequency as well as the static positive resistance of the discharge in the shifted NDR region. Modeling of the discharge configuration indicated that the inductor element of the suppressor circuit increases the time lag of the plasma response, which increases the stable region of operation. A stability map in terms of the external circuit parameters is introduced. [ABSTRACT FROM AUTHOR]

The current work was aimed to prepare and investigate switching phenomena effect in single crystals made from TlBiS2 under static Condition Current. Negative resistance (CCNR) has been controlled in TlBiS2 single crystals and observed for the first time. Both polarities of switching process take place on the crystal possessing symmetrical shapes. The prepared single crystals exhibited a bistable or memory switching with S-type form. A resulted symmetrical shaped current and voltage characteristics, CVC, for sandwiched TlBiS2 single crystal with Ag electrodes exhibited two main regions as high resistance OFF state region and low resistance ON state region featuring negative differential resistance, NDR. Results have shown that the phenomena of switching in the samples show strong sensitivity to the surrounding sample temperature, thickness and light intensity of illumination. The main parameters for switching such as ith,Vth, Pth, Eth, ih,Vh, and ROFF/RON) were calculated under influence of various factors of the nearby conditions. [ABSTRACT FROM AUTHOR]

In this study, we have investigated the impact of various defects and deformations such as rough edge, twist, wrap (tube) and ripple on the NDR (negative differential resistance) behavior of a MoSe armchair (ANR) MOSFET. We have studied the current voltage characteristics of the device under these deformations along with the transmission spectrum of the ANR channel. Change in the NDR region and peak-to-valley ratio has been observed for each deformation, and significant changes were observed in each case. [ABSTRACT FROM AUTHOR]

To demonstrate the extending functionality of the simplest MOS (metal-oxide-semiconductor) capacitor, a structure with a p-Si/nano-SiO heterojunction in which strongly degenerate n-Si is used instead of a metal electrode is considered. As a result, a tunnel diode with negative differential resistance and a quartz resonator is obtained. Its electrical characteristics are superior to those of the corresponding Esaki diode and are controlled not only by the Silicon doping level, but also by the SiO thickness. [ABSTRACT FROM AUTHOR]

Regions with negative differential resistance can arise in the IV curve of Josephson junctions and this phenomenon plays an essential role for applications, in particular for THz radiation emission. For the measurement of high frequency radiation from Josephson junctions, a cavity - either internal or external - is often used. A cavity may also induce a negative differential resistance region at the lower side of the resonance frequency. We investigate the dynamics of Josephson junctions with a negative differential resistance in the quasi particle tunnel current, i.e. in the McCumber curve. We find that very complicated and unexpected interactions take place. This may be useful for the interpretation of experimental measurements of THz radiation from intrinsic Josephson junctions. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the avalanche behavior of field-stop insulated gate bipolar transistors (IGBTs) by means of analytical and theoretical considerations, supported by ad hoc numerical simulations. A physical explanation of the presence of negative differential resistance branches in the avalanche I-V curve of the IGBT is presented and design criteria are derived to reduce and eventually eliminate this effect. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Electrical switching phenomenon was observed in TlGaSe2. [•] S-type negative resistance I–V characteristics was observed. [•] The effects external effects on the switching characteristics were studied. [•] The switching phenomenon is discussed on models for disordered semiconductors. [•] It was shown that TlGaSe2 is chalcogenide glassy semiconductors. [ABSTRACT FROM AUTHOR]

ABSTRACT A 50-67-GHz double-balanced mixer for direct up-conversion using standard 90-nm CMOS technology is reported. The up-conversion mixer comprises an enhanced double-balanced Gilbert cell with current injection for power consumption reduction, and negative resistance compensation for conversion gain (CG) enhancement, a parallel and differential intermediate frequency (IF) transconductance stage for bandwidth and linearity enhancement, a Marchand balun for converting the single local oscillator (LO) input signal to differential signal, and another Marchand balun for converting the differential radio-frequency (RF) output signal to single signal. The mixer consumes 12.1 mW and achieves IF-port input return loss of −12.8 dB at 0.1 GHz, LO-port input return loss of −9.5 to −11.4 dB and RF-port input return loss of −10.7 to −12.5 dB for frequencies 57-64 GHz. At IF of 0.1 GHz, the mixer achieves CG of 3.1-6 dB and LO-RF isolation of 26.4-30.7 dB for RF of 50-67 GHz. The corresponding 3-dB bandwidth of RF is larger than 17 GHz (the measurement range of 50-67 GHz). To the authors' knowledge, the CG and power consumption are the best results ever reported for a 60-GHz CMOS/BiCMOS up-conversion mixer. In addition, the measured IIP3 is −6.4 dBm at RF of 60 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:475-483, 2014 [ABSTRACT FROM AUTHOR]

The donor-acceptor molecule is the only molecule that features a real intrinsic rectification. However, all investigations in the last decades showed that rectification behaviors of such molecules are not promising since their rectification ratio is only on the order of 10. Use of carbon chains C n to serve as spacers is reported, along with attempts to modulate electrical behavior of the donor-acceptor molecule. Calculations using the first-principles method show that electrical behavior is indeed altered substantively, and a particular regularity can be clearly observed, i.e., a dramatic odd-even oscillation for electronic behavior with increasing carbon-chain length n. For models with even- n carbon chains, the rectification ratio is small (30), and no negative differential resistance (NDR) behavior is detected, but the rectifying performance of models with odd- n carbon chains is tremendously improved and rectification ratios on the order of 50 to 400 can be achieved, alongside a large NDR. This study thus suggests that using a suitable spacer might be an effective way to significantly boost electrical characteristics, including rectifying performance, of the donor-acceptor molecule. [ABSTRACT FROM AUTHOR]

We study the transport properties of deeply scaled monolayer MoS2 n-channel metal-oxide-semiconductor field effect transistors (MOSFETs), using full-band ballistic quantum transport simulations, with an atomistic tight-binding Hamiltonian obtained from density functional theory. Our simulations suggest that monolayer MoS2 MOSFETs can provide near-ideal subthreshold slope, suppression of drain-induced barrier lowering, and gate-induced drain leakage. However, these full-band simulations exhibit limited transconductance. These ballistic simulations also exhibit negative differential resistance (NDR) in the output characteristics associated with the narrow width in energy of the lowest conduction band, but this NDR may be substantially reduced or eliminated by scattering in MoS2. [ABSTRACT FROM AUTHOR]

This work is devoted to the investigation of the discharge characteristics of high-frequency alternating current (ac) plasma torch working with air medium using electrical and spectroscopic techniques. A simple structure and compact ac plasma torch associated with a resonance power supply allows the generation of low power discharges (lower than 1 kW) with high voltage and low current. The discharge shows a negative resistance characteristic, and its curve shifts up with gas flow increased. The effects of power on the emission intensity of NO (A2Σ+ → X2Π), OH (A2Σ → X2Π, 0–0), N2(C3Πu → B3Πg), Hα and O and their spatial distributions in plasma jet axial direction were investigated. It has been found that the emission intensities of NO, OH, N2, Hα and O rise with an increase in power dissipation. With increasing axial distances of plasma jet from nozzle exit, the emission intensity of OH increases and then decreases, while the emission intensities of other species decrease sharply. The vibrational temperature is much higher than the gas temperature, which demonstrates the ac-driven arc discharge deviation from thermal equilibrium plasma. [ABSTRACT FROM AUTHOR]

Spatially periodic structures, such as bladed disks, are widely used as components in rotating machines. The recent advent of blade-tip-timing sensing technique has allowed the extraction of vibratory response information of blades during rotation for damage detection purposes. The decision making in damage detection of a periodic structure based on such measurement, however, is difficult primarily because of the clustered natural frequencies and high modal density, which is further complicated by inevitable structural uncertainty/variation. Our underlying idea is to integrate piezoelectric transducers together with circuitry elements onto the periodic structure to alter its dynamic characteristics during the inspection stage to improve the sensitivity and robustness of vibration-based damage detection. In particular, it has been identified that a properly designed piezoelectric inductive circuitry can amplify the response anomaly under external excitation. Such amplification nevertheless diminishes as the mechanical damping in the periodic structure increases. In this research, it is shown that the adverse effect of mechanical damping to anomaly amplification can be effectively reduced, by incorporating negative resistance elements into the piezoelectric circuitry network. The negative resistance elements are synthesized using operational amplifier circuits and can offset the mechanical damping through the dynamic interaction between the piezoelectric circuitry and the host structure. The stability boundary of the negative resistance integration is identified, where the frequency-dependent inherent resistance of the piezoelectric transducer is taken into consideration explicitly. The effectiveness of the enhanced circuitry network for amplifying damage signature in periodic structures under large damping is illustrated with detailed case studies. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Aluminum and indium selenide thin films are used to design MgO tunneling diodes. [•] The Al/MgO/C and C/MgO/InSe/C tunneling diode structures are characterized. [•] The C/MgO/InSe/C device exhibited a peak to valley current ratio of 135. [•] It reflected negative resistance effect in the voltage range of 0.94–2.24. [•] A resonance peak located at 39MHz was observed. [Copyright &y& Elsevier]

The paper discusses on the fundamentals of the injection locked oscillator. Starting from the Adler's approach of the injection locked oscillator to the Razavi's model of the injection locked oscillator is discussed in details. Experimental results are also incorporated in support of the analytical results. [ABSTRACT FROM AUTHOR]

InAs quantum dots are introduced into resonant tunneling diodes to study the electronic transport behavior, and a wide bistability (ΔV ∼ 0.8 V) is observed in the negative differential resistance region. Based on an analytic model, we attribute the observed distinct bistability of a resonant tunneling diodes with quantum dots to the feedback dependence of energy of the electron-storing quantum dots on the tunneling current density. Meanwhile, we find that this wide bistable region can be modulated sensitively by light illumination and becomes narrower with increasing light intensity. Our results suggest that the present devices can be potentially used as sensitive photodetectors in optoelectronic fields. [ABSTRACT FROM AUTHOR]

Negative differential resistance (NDR), for which the current is a decreasing function of the voltage, has been observed in the current–voltage curves of several types of structures. We measured tunnelling current and NDR by illuminating large area heterojunction obtained by growing Multi Wall Carbon Nanotubes on the surface of n-doped Silicon substrate. In the absence of light, the current flow is null until a junction threshold of about 2.4 V is reached, beyond which the dark current flows at room temperature with a very low intensity of few nA. When illuminated, a current of tens nA is observed at a drain voltage of about 1.5 V. At higher voltage the current intensity decreases according to a negative resistance of the order of MΩ. In the following we report details of tunneling photodiode realized and negative resistance characteristics. [ABSTRACT FROM AUTHOR]

Resistive random access memory (RRAM) is one of the most promising emerging nonvolatile technologies for the futuristic memory devices. Resistive switching behavior often shows negative resistance (NR), either voltage controlled or current controlled. In this work, the origin of a current compliance dependent voltage controlled NR effect during the resetting of anion migration based RRAM devices is discussed. The N-type voltage controlled NR is a high field driven phenomena. The current conduction within the range of a certain negative voltage is mostly dominated by space charge limited current. But with the higher negative voltage, a field induced tunneling effect is generated in the NR region. The voltage controlled NR is strongly dependent on the compliance current. The area independent behavior indicates the filamentary switching. The peak to valley ratio (PVR) is > 5. The variation of PVR as a function of the conduction band offset is achieved. Compared to other reported works, based on the PVR, it is possible to distinguish the RRAM types. Generally, due to the higher electric field effect on the metallic bridge during RESET, the electrochemical metallization type RRAM shows much higher PVR than the valance change type RRAM. [ABSTRACT FROM AUTHOR]

Magnetic induction can be regarded as a negative feedback effect, where the motive-force opposes the change of magnetic flux that generates the motive-force. In artificial electromagnetics emerging from spintronics, however, this is not necessarily the case. By studying the current-induced domain wall dynamics in a cylindrical nanowire, we show that the spin motive-force exerting on electrons can either oppose or support the applied current that drives the domain wall. The switching into the anomalous feedback regime occurs when the strength of the dissipative torque β is about twice the value of the Gilbert damping constant α. The anomalous feedback manifests as a negative domain wall resistance, which has an analogy with the water turbine. [ABSTRACT FROM AUTHOR]

The effect of the negative differential conductance of a ferromagnetic barrier on the surface of a topological insulator is theoretically investigated. Due to the changes of the shape and position of the Fermi surfaces in the ferromagnetic barrier, the transport processes can be divided into three kinds: the total, partial, and blockade transmission mechanisms. The bias voltage can give rise to the transition of the transport processes from partial to blockade transmission mechanisms, which results in a considerable effect of negative differential conductance. With appropriate structural parameters, the current-voltage characteristics show that the minimum value of the current can reach to zero in a wide range of the bias voltage, and then a large peak-to-valley current ratio can be obtained. [ABSTRACT FROM AUTHOR]

We describe a circuit model for a flux-driven Superconducting QUantum Interference Device (SQUID). This is useful for developing insight into how these devices perform as active elements in parametric amplifiers. The key concept is that frequency mixing in a flux-pumped SQUID allows for the appearance of an effective negative resistance. In the three-wave, degenerate case treated here, a negative resistance appears only over a certain range of allowed input signal phase. This model readily lends itself to testable predictions of more complicated circuits. [ABSTRACT FROM AUTHOR]