Forward Resistance Research Articles

Interface electronic structure and the Schottky barrier at Al-diamond interface: hybrid density functional theory HSE06 investigation

Diamond is regarded as one of the most promising semiconductor materials used for high power devices because of its superior physical and electrical properties, such as wide bandgap, high breakdown electric field, high mobility, and high thermal conductivity. Highpower diamond devices are now receiving much attention. In particular, Schottky diode based on a metal/diamond junction has promising applications, and high breakdown voltage has been achieved, though unfortunately its forward resistance is high. In this paper, the first principles calculations are performed to study the electronic structure of interface and the Schottky barrier height of Al-diamond interface. The projection of the density of states on the atomic orbitals of the interface atoms reveals that the typical Al-induced gap states are associated with a smooth density of states in the bulk diamond band gap region, and these gap states are found to be localized within three atom layers. At the same time, electronic charge transfer makes the Fermi level upgrade on the side of diamond. Besides, the typical Al-induced gap state model gives a simple picture about what determines Schottky barrier height at Al-diamond interface, by assuming an ideal, defect-free and laterally homogeneous Schottky interface in which the only interaction comes from the decay of the electron wave function from the metal into the semiconductor, which in turn induces electronic charges to be rearranged in the region close to the interface. As for the electronic charge transfer, this potential shift can be extracted by subtracting the superimposed planar or macroscopically averaged electrostatic potentials of the Al and diamond surfaces (at frozen atomic positions), from the planar or macroscopically averaged potential of the relaxed Al-diamond interface. The electronic charge transfer suggests that the formation of an interface should be associated with the formation of new chemical bonds and substantial rearrangements of the electron charge density. Especially, we obtain the Schottky barrier height of 1.03 by the first principle, which is in good agreement with the results from phenomenological model and experiment. The research results in this paper can provide a theoretical basis for the research of the metal diamond Schottky junction diode, and can also give a theoretical reference for the research of the metal-semiconductor highpower device based on diamond material.

Spin Trapping: A Review for the Study of Obesity Related Oxidative Stress and Na+/K+-ATPase.

Reactive oxygen species (ROS) have gained attention with mounting evidence of their importance in cell signaling and various disease states. ROS is produced continuously as a natural by-product of normal oxygen metabolism. However, high levels ROS causes oxidative stress and damage to biomolecules. This results in loss of protein function, DNA cleavage, lipid peroxidation, or ultimately cell injury or death. Obesity has become a worldwide epidemic; studies show fat accumulation is associated with increased ROS and oxidative stress. Evidence exists supporting oxidative stress as a factor driving forward insulin resistance (IR), potentially resulting in diabetes. Na+/K+-ATPase signaling is also a potential source of ROS promoting oxidative stress. The best way to observe radical species in biological systems is electron paramagnetic resonance spectroscopy with spin trapping. EPR spin trapping is an important technique to study the mechanisms driving disease states attributed to ROS.

TJET: Ternary Join-Exit-Tree Based Dynamic Key Management for Vehicle Platooning

Vehicle platooning, which is formed by a group of vehicles traveling in close proximity to one another, nose-to-tail, at highway speeds, has received considerable attention in recent years. However, though it brings many opportunities in self-driving, the security of vehicle platooning is still challenging. In this paper, to secure vehicle platooning, particularly to secure communication and efficient key updating for vehicles in a platoon, we first present the notion of ternary join exit tree. A ternary join exit tree consists of main tree, join tree, and exit tree. The users join in the join tree and leave from exit tree. Then, we propose a new dynamic ternary join-exit tree-based dynamic key management scheme, called TJET, for vehicle platooning, which is characterized by providing efficient key updating for not only vehicle joining and leaving, but also platoon merging and splitting. Specifically, based on the structure of ternary join-exit tree, we devise concrete algorithms for vehicle joining, vehicle exiting, platoon merging, and splitting. Moreover, we also analyze the capacities and activation conditions of join tree and exit tree based on strict mathematical proofs. Detailed security analysis show that our proposed TJET holds desirable security properties including forward security, backward security, and resistance to key control. In addition, performance evaluations via extensive simulations demonstrate the efficiency of TJET.

Simulation Analysis of Flow Characteristics in the Vortex Diode with Double Tangential Tube

The paper analyzed flow characteristics in vortex diode with double tangential tube by numerical simulation. Compared to traditional vortex diode with one tangential tube, the structure of double tangential tube can reduce the forward resistance and improve overall performance. The symmetrical design adopted in vortex diode with double tangential tube; the internal flow field in chamber showed symmetrical distribution in the reverse flow, which can improve the flow stability and accelerate the convergence speed in simulation.

A new concept for design of the shape ship stern

The paper presents an original stern shapes design which obtaining a good distribution of the ship wake able to reduce the drag. The paper begins to present the problems directly and reversely, physical mathematical shaping and the numerical implementation (including the precision of numerical approach). For this purpose, the imagining of a current tube is suggested, with increasing variable cylindrical sections, which starts from the disk in front of the propeller, extends towards the prow, very close to the cylindrical area and which includes the entire stern section of a classic hull having practiced cross corrugated sections). Certainly, the dynamics of a cavity propeller depends on the work environment system. The flow field around a propeller mounted on the ship is very different to the one that a propeller develops when tested in free water or in a section of a cavitation tunnel. A propeller with a very performance in free water may not be right for a stern shape of a hull of the given ship. For this reason, the ship wake distribution in the propeller disk plan represents a key factor for a ship design. The study tries to draw attention and briefly focuses on ships hull’s stern flows in the light of two absolutely strict original ideas (concepts) in ship hydrodynamics, belonging to the author: 1.a new stern hydrodynamic concept (NSHC), with radial crenellated-corrugated sections 2. using of an inverse piezoelectric effect [(electric current→high-frequency power generator→ piezoelectric driver made of certain ceramic material, which induces an elliptical vibratory movement (high frequency over 20 kHz), into the elastic side plates (15 mm thickness) in the streamlines direction (of the external flowing water)], able to reduce the total forward resistance. Resuming, it can be concluded that the new concept of stern shape proposed as well as the reverse mathematical problem presented above for its optimization, based on the Levenberg-Marquardt algorithm seem to be reasonable. Finally, the most important, until now, proved result, is the reducing of propeller cavitation (working in the simulated nominal wake of the hull using the new shape stern.Keywords: vessel wake, propeller cavitation, drag, stern shape, cavitation tunnel, ultrasonic vibrator.

A new measurement protocol of direct current resistivity data

We have developed a new protocol for measuring direct current (DC) resistivity data, in which self-potential (SP) data were measured immediately prior to obtaining the resistivity data. Based on this SP measurement, we have defined two different resistances: the forward resistance (i.e., a normalized potential difference caused by forward current injection) and the backward resistance (i.e., a normalized potential difference caused by backward current injection). This has allowed us to quantify distortions in the DC resistivity potential field caused by all unknown mechanisms, including ambient noises. In accordance with the proposed measurement protocol, we further devised a data-weighting method in a resistivity inversion for calculating more reasonable subsurface structures, and the method was based on the forward and backward resistances. Through inversion experiments using field resistivity data acquired by the proposed protocol, we have determined the validity and effectiveness of the proposed method.

Effects of Ultrasonic Vibration on the Welding Process of Friction Stir Welding

Based on the understanding of Friction Stir Welding (FSW) and the effect of ultrasound, the purpose of the paper is trying to find the effective access to reduce the welding resistance and improve the quality of weld during FSW. The best vibration point was first determined through the vibration test system. Then, the thermal cycling, three-force and torque were tested by using paperless recorder and mechanical sensor in heat-power test bench for 4mm thick AZ31 magnesium alloy. The results showed that the periodic vibration took place at the weld under the excitation of ultrasonic vibration, and the frequency of this vibration was as same as the frequency of ultrasonic vibration. The best tracking distance of ultrasonic vibration was 40 mm, and its optimal incident angle was 45°. By applying ultrasonic vibration to FSW, the forward resistance, the axial force and the torque of the tool can be significantly reduced. In addition, the distribution of temperature field was basically consistent with the two conditions, presenting “asymmetrical, non-linear” distribution characteristic. The heating effect of ultrasonic vibration was not obvious, but it was able to make the temperature field of the welding seam become more uniform.

In situ electrical modulation and monitoring of nanoporous gold morphology.

The ability to fine-tune feature size in nanostructured thin films is critical, as many desirable properties of these materials are dictated by their nanostructure. Accordingly, there is a need for techniques that allow for modifying nanostructure while monitoring the morphological changes in situ. Here, we demonstrate a closed-loop electro-annealing system which enables in situ monitoring of morphology evolution in sub-micron nanoporous gold (np-Au) thin films. Np-Au is produced by a microfabrication-compatible self-assembly process that produces a network of interconnected ligaments with tunable diameter (10 s to 100 s of nanometers), making it a desirable material for numerous applications and fundamental studies alike. We specifically investigate the relationship between np-Au morphology (i.e., ligament diameter) and electrical resistance of the thin film. A strong correlation emerges between ligament size and electrical resistance, which puts forward resistance as an effective parameter for monitoring morphology evolution. Surprisingly, np-Au films with thicker ligaments lead to an increase in electrical resistance, which is unexpected since the extent of charge carrier scattering at the ligament surface should decrease with increasing ligament size. Further examination of np-Au morphology with high-resolution electron microscopy revealed grain growth on the ligaments in highly-annealed np-Au thin films. This suggests that grains act as scattering centers for charge carriers and this becomes the dominant mechanism in dictating electrical resistance in a percolated network of thin conductive ligaments.

Characterization of vertical GaN p–n diodes and junction field-effect transistors on bulk GaN down to cryogenic temperatures

There is great interest in wide-bandgap semiconductor devices and most recently in vertical GaN structures for power electronic applications such as power supplies, solar inverters and motor drives. In this paper the temperature-dependent electrical behavior of vertical GaN p–n diodes and vertical junction field-effect transistors fabricated on bulk GaN substrates of low defect density (104 to 106 cm−2) is described. Homoepitaxial MOCVD growth of GaN on its native substrate and the ability to control the doping in the drift layers in GaN have allowed the realization of vertical device architectures with drift layer thicknesses of 6 to 40 μm and net carrier electron concentrations as low as 1 × 1015 cm−3. This parameter range is suitable for applications requiring breakdown voltages of 1.2 kV to 5 kV. Mg, which is used as a p-type dopant in GaN, is a relatively deep acceptor (EA ≈ 0.18 eV) and susceptible to freeze-out at temperatures below 200 K. The loss of holes in p-GaN has a deleterious effect on p–n junction behavior, p-GaN contacts and channel control in junction field-effect transistors at temperatures below 200 K. Impact ionization-based avalanche breakdown (BV > 1200 V) in GaN p–n junctions is characterized between 77 K and 423 K for the first time. At higher temperatures the p–n junction breakdown voltage improves due to increased phonon scattering. A positive temperature coefficient in the breakdown voltage is demonstrated down to 77 K; however, the device breakdown characteristics are not as abrupt at temperatures below 200 K. On the other hand, contact resistance to p-GaN is reduced dramatically above room temperature, improving the overall device performance in GaN p–n diodes in all cases except where the n-type drift region resistance dominates the total forward resistance. In this case, the electron mobility can be deconvolved and is found to decrease with T−3/2, consistent with a phonon scattering model. Also, normally-on vertical junction field-effect transistors with BV = 1000 V and drain currents of 4 A are fabricated and characterized over the same temperature range. It is demonstrated that vertical GaN devices (diodes and transistors) utilizing p–n junctions are suitable for most practical applications including automotive ones (210 K < T < 423 K). While devices are functional at cryogenic temperatures (77 K) there may be some limitations to their performance due the freeze-out of Mg acceptors.

A Wideband 20 mW UHF Rectifier in CMOS

This letter presents the first CMOSFET RF-to-DC Rectifier IC which delivers more than 10 mW dc power at GHz frequency. This IC utilizes the single-ended In-phase Gate-boosting Rectifier (IGR) architecture, and its In-Phase Voltage Multiplier (IPVM) is derived from a $\lambda/2$ transmission line to boost in-phase $V_{GS}$ from the driving $V_{DS}$ . This simultaneously reduces the effective threshold voltage, forward resistance, and reverse leakage current of the rectifying transistors. To improve an IGR's performance, both RF source-pull and dc load-pull are carried out to find the optimal performance. The UHF IGR is implemented using thick-gate-oxide I/O transistors with 0.28 $\mu{\rm m}$ minimum gate length in TSMC 65 nm CMOS process. The implemented IC achieves a 20 mW output dc power with 31.8% peak efficiency at 900 MHz with 200 MHz 1 dB bandwidth.

A strongly secure identity-based authenticated key agreement protocol without pairings under the GDH assumption

Among the existing identity-based authenticated key agreement ID-AKA protocols, there are only a few of them that can resist to leakage of ephemeral secret keys, which is about the protection of the session secret key after the ephemeral secret keys of users are compromised. However, all these ID-AKA protocols with leakage of ephemeral secret keys resistance require expensive bilinear pairing operations. In this paper, we present a pairing-free ID-AKA protocol with ephemeral secrets leakage resistance. We also provide a full proof of its security in the extended Canetti-Krawczyk model, which not only can capture resistance to leakage of ephemeral secret keys but also can capture other basic security properties such as master key forward security and key compromise impersonation resistance. Compared with the existing ID-AKA protocols, our scheme is a good trade-off between security and efficiency. Copyright © 2015 John Wiley & Sons, Ltd.

A method for determining the ambipolar diffusion length and carrier lifetime in GaAs p-i-n diodes

It was determined that the forward loss resistance as a function of the radius of the active region of typical microwave p-i-n diodes depends on the ratio of the square of the ambipolar-diffusion length to the square of the radius of the diode active region. Based on this regularity, a method was developed that provides simple determination of the ambipolar-diffusion length and the carrier lifetime.

Collective Cell Motility Promotes Chemotactic Prowess and Resistance to Chemorepulsion

Collective cell migration is a widespread biological phenomenon, whereby groups of highly coordinated, adherent cells move in a polarized fashion. This migration mode is a hallmark of tissue morphogenesis during development and repair and of solid tumor dissemination. In addition to circulating as solitary cells, lymphoid malignancies can assemble into tissues as multicellular aggregates. Whether malignant lymphocytes are capable of coordinating their motility in the context of chemokine gradients is, however, unknown. Here, we show that, upon exposure to CCL19 or CXCL12 gradients, malignant B and T lymphocytes assemble into clusters that migrate directionally and display a wider chemotactic sensitivity than individual cells. Physical modeling recapitulates cluster motility statistics and shows that intracluster cell cohesion results in noise reduction and enhanced directionality. Quantitative image analysis reveals that cluster migration runs are periodically interrupted by transitory rotation and random phases that favor leader cell turnover. Additionally, internalization of CCR7 in leader cells is accompanied by protrusion retraction, loss of polarity, and the ensuing replacement by new leader cells. These mechanisms ensure sustained forward migration and resistance to chemorepulsion, a behavior of individual cells exposed to steep CCL19 gradients that depends on CCR7 endocytosis. Thus, coordinated cluster dynamics confer distinct chemotactic properties, highlighting unexpected features of lymphoid cell migration.

A Millimeter-Wave In-Phase Gate-Boosting Rectifier

This paper introduces a new class of RF-to-dc rectifiers called the in-phase gate-boosting rectifier (IGR). An IGR utilizes an in-phase passive voltage multiplier (IPVM) to boost in-phase VGS swing from the driving VDS swing. This design simultaneously reduces the effective threshold voltage, forward resistance, and the reverse leakage current of the rectifying transistor. As a consequence, the sensitivity and the efficiency of a high-frequency rectifier can be improved. Furthermore, a CG-loaded IPVM presents low input conductance and is shunted with the drains/sources of the rectifying transistors. This makes the realization of the input matching network between the IGR core and the antenna easier, and achieves a higher voltage swing at the input terminals of the IGR core. The criteria, properties, and relating proofs of the IPVM are also discussed. A differential seven-stage millimeter-wave IGR is implemented in a 65-nm RF CMOS process. In this design, an interleaving internal threshold cancellation bias scheme is also introduced to further suppress the power consumption due to biasing circuitry without increasing the layout area. The implemented integrated circuit achieves a state-of-the-art -7-dBm sensitivity with 20% peak efficiency at 53 GHz and a bandwidth of 10 GHz from 46 to 56 GHz.

InGaN/GaN tunnel junctions for hole injection in GaN light emitting diodes

InGaN/GaN tunnel junction contacts were grown using plasma assisted molecular beam epitaxy (MBE) on top of a metal-organic chemical vapor deposition (MOCVD)-grown InGaN/GaN blue (450 nm) light emitting diode. A voltage drop of 5.3 V at 100 mA, forward resistance of 2 × 10−2 Ω cm2, and a higher light output power compared to the reference light emitting diodes (LED) with semi-transparent p-contacts were measured in the tunnel junction LED (TJLED). A forward resistance of 5 × 10−4 Ω cm2 was measured in a GaN PN junction with the identical tunnel junction contact as the TJLED, grown completely by MBE. The depletion region due to the impurities at the regrowth interface between the MBE tunnel junction and the MOCVD-grown LED was hence found to limit the forward resistance measured in the TJLED.

Design of UPS Battery Remote Monitoring System

UPS battery remote monitoring system based on MSP430 single chip microcomputer design, using modular thinking as the core to build the overall structure, to realize the battery voltage, current and temperature of the online real-time monitoring through the acquisition module in the aspect of hardware, and putting forward resistance measurement method that based on ac injection method and phase lock amplifying method; Using software to implement the UPS battery fault information alarm function through the overall process design.

Pin diodes and their impact on reconfigurable compact microstrip antennas with high frequency‐ratio

ABSTRACTThis work presents a study of the impact of PIN diodes on the performance of reconfigurable compact microstrip antennas with high frequency‐ratio. To this purpose, two frequency reconfigurable microstrip antennas with a frequency‐ratio of 3 (868 MHz and 2.45 GHz ISM bands) and a different degree of compactness have been designed and measured for various PIN‐diode configurations. The results show the derivative effects of using PIN diodes in the conditions mentioned, namely current cancelation, power dissipation, and frequency shift, and how to reduce their impact. The most significant repercussion is in the radiation efficiency, which can be enhanced from 46 to 74% using a less compact design, and by reducing the forward resistance of the PIN diode, what increases the radiation efficiency by a factor of 4. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2676–2681, 2014

High-Speed and High-Light Output Power of InGaAs/GaAs HBLETs With an InMoO&lt;sub&gt;x&lt;/sub&gt; Contact

A high-speed and high-light-output-power InGaAs/GaAs heterojunction bipolar light-emitting transistors (HBLETs) at 968-nm wavelength employing indium molybdenum oxide (IMO) contact are demonstrated in this letter. The IMO contact exhibits a low electrical resistivity of \(3.5 \times 10^{\mathrm {\mathbf {-4}}}~\Omega \) -cm accompanied with an extremely high optical transmittance of 99% at 968 nm, which can be ascribed to larger valence difference between In 3+ matrix and Mo 6+ dopants. As compared to HBLET with conventional AuGe contact, HBLET with IMO contact shows a higher forward voltage and higher series resistance. However, at the corresponding injection current level, HBLET with IMO contact produces a light output power with a rate of \(5.7~\mu \) W/mA, which is twice of \(2.7~\mu \) W/mA for HBLET with AuGe contact. In addition, HBLET with IMO contact exhibits a 3-dB optical bandwidth of 649 MHz, which is correlated to a carrier recombination lifetime of 245 ps. The successful incorporation of an IMO contact into an HBLET can improve the optical output extraction significantly without the expense of losing modulation speed.

A current–voltage–temperature method for fast extraction of schottky diode static parameters

We propose a simple graphical method to extract the static parameters of an arbitrary schottky diode. The method is an extension of the current–voltage method by the inclusion of a temperature aspect, and hence may be referred to as a current–voltage–temperature (I–V–T) method. The voltage–temperature characteristics are first obtained at two constant currents. Then, by considering the points on the characteristics with common attributes of either voltage or temperature under specified current density, a specific parameter is calculated. This abstraction is shown mathematically to greatly simplify the calculation of ideality factor, barrier height and diode resistance. The diode is first considered to be ideal with zero current modulation by a base resistance. The effect of non-zero base resistance is then subsequently quantified. Finally, the analysis of simulations on the commercial BAT54 schottky diode and published data for fabricated Au/n-Ge, Au/n-Si and Au/n-GaAs schottky diodes are presented. Application of the I–V–T method to different regions of the characteristics produces much lower variances in calculated barrier height, ideality factor and forward resistance in contrast to those based on the source publications. This suggests that the I–V–T method is a feasible alternative to characterize these diodes. The underlying reason being that control is exerted on the current density by the experimenter.

Authenticated key exchange with entities from different settings and varied groups

AbstractAuthenticated key exchange (AKE) is a very important primitive in cryptography. In the last decades, many AKE protocols appeared either in the certificate‐based (cert‐based) setting or in the identity‐based (id‐based) setting. In real applications, entities from different settings may also have the requirement to communicate with each other. Several papers have concentrated on supporting either multiple certification authorities or multiple key generation centers, but very few have considered the interoperability between the two settings. Furthermore, existing approaches are still inadequate in supporting parameters from different algebraic groups.In this paper, we consider AKE protocols integrating cert‐based and id‐based settings with varied groups. Based on two extract algorithms for id‐based entities, we present two AKE protocols where one entity is cert‐based and the other is id‐based, and the parameters of both entities come from different groups. An extended AKE security model of Chatterjee et al. and Ustaoǧlu [1, 2] is proposed to support multiple certification authorities and multiple key generation centers in which the proposed protocols are proved to be secure. Other variant protocols are also presented. Then, extensions to support forward secrecy and resistance to leakage of both ephemeral keys are provided. Finally, we present a more efficient integrating protocol than existing constructions for users who use the same group. Copyright © 2013 John Wiley &amp; Sons, Ltd.