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The substitution effect of a Ferro-magnet (FM) electrode by a half-metallic FM material La0.7Sr0.3MnO3 (LSMO) on charge current and spin-transfer torque (STT) components is studied in MgO-based double barrier magnetic tunnel junctions (DBMTJs) with a middle non-magnetic metal (NM) layer. Using non-equilibrium Green’s function (NEGF) formalism, it is observed that the current and STT components show oscillatory behavior due to quantum well states in the middle NM layer and resonant tunneling effect. We also study effect of difference in the thickness of the MgO insulators. Bias dependence demonstrate the magnitude enhancement of the current and in-plane STT in new asymmetric DBMTJs (A-DBMTJs) compared with symmetric DBMTJs (S-DBMTJs), however, perpendicular STT decreases in the A-DBMTJs. Results also show different behavior compared with conventional asymmetric MTJs and spin valves (SVs). Therefore, one can design new memory devices by means of suitable insulator and FM electrodes with proper thicknesses.

The first phase of steam flood development has been successfully implemented in a Petroleum Development Oman (PDO). The oil producer wells are completed with a single mechanical barrier as they are classified as low risk (not having a potential to self-flow to surface as the target formation is under pressured). However, in the later stages of development, steam break through into the producer occurs and must be managed to maximize production and increase recovery rates. To avoid gas-lock of the production pump, a fluid level is maintained in the wellbore by producing the steam up the production annulus, a production strategy referred to as casing venting. Implementing this strategy causes the producer wells to be capable of self flowing if steam injection is maintained. A well capable of self flowing to surface is classified as medium risk and requires two barriers. For phase 2 of the project, expansion of the field to the North and South, the producer wellheads will have a Hydraulic Surface Annulus Safety Valve (H-SAS) system installed in the VR profile on either side of the A-anulus (right & left) as the primary barrier. The SOV's (Side Outlet Valve) will be the second barrier. The H-SAS system was developed to assure and enhance annulus integrity. As part of the capabilities, the utilization of this safety device allows pressure management and operational venting within the annulus while providing a barrier in the event of an incident. The new wellhead design will meet the well compliance requirements and also allow for casing venting during operation.

Directional excitation of surface plasmon polaritons (SPPs) by electrical means is important for the integration of plasmonics with molecular electronics or steering signals toward other components. We report electrically driven SPP sources based on quantum mechanical tunneling across molecular double-barrier junctions, where the tunneling pathway is defined by the molecules' chemical structure as well as by their tilt angle with respect to the surface normal. Self-assembled monolayers of S(CH

The hot carrier cell (HCSCs) is a promising advanced photovoltaic concept. It aims to minimize major losses in p-n junction solar cells and is predicted to have energy conversion efficiency over 65% at one sun. Energy selective contacts (ESCs) is a critical component of the HCSC. In this paper, potential of ESCs based on quantum dot and quantum well double barrier resonant tunneling structures is presented. Results of I-V measurements these show negative differential resistance (NDR) characteristics both at low temperature and room temperature, thus indicating that these structures can be suitable for ESC application.

We study the resistance states and spin dynamics in a Ag/Fe(8)/MgO(3)/Fe(8)/MgO(5)/Fe/Ag junction based on a first-principles scattering theory. Spin dynamics simulations show that up to four resistance states with noticeable difference can be achieved via manipulating the voltage bias scheme and the position of the reference magnetization. The study indicates possible multiple-valued logic applications in an asymmetric MgO-based double-barrier magnetic tunnel junction.

This paper explores performance and technology-scalability of STT-MRAMs exploiting double-barrier MTJs (DMTJs) as comparatively evaluated with respect to conventional solution based on single-barrier MTJs (SMTJs). The comparative study was carried out at different design abstraction levels: (i) a bitcell-Ievel analysis relying on the use of Verilog-A compact models, and (ii) an architecture-level analysis for various memory sizes. Overall, our simulation results point out that, thanks to the reduced switching currents, DMTJ-based STT-MRAMs allow reducing write latency of about 60% than their SMTJ-based counterparts. This is achieved while assuring lower energy consumption under both write (-40%) and read (-27%) accesses, at the cost of reduced sensing margins.

This paper describes the physical simulation of Al0.3Ga0.7N/GaN-based double barrier resonant tunnelling diode (RTD) with cubic-GaN structure using Silvaco ATLAS. Cubic-GaN is interesting for vertical transport devices due to the absence of internal polarization. Proper selection of material parameters is vital in order to optimize the device performance. The relationship between current-voltage (I-V) characteristic, particularly the negative differential resistance (NDR) with respect to variation in barrier composition, well width and barrier thickness are studied in detail. RTDs with clear NDR are demonstrated with peak-to-valley-current ratio (PVCR) of 7.19 and peak current density of 3.77 mA/cm2 at room temperature. The optimum barrier thickness for a given composition is determined by using the ratio of current magnitude at resonant peak to the width of the resonance, and also used as figure of merit for the device. Finally, optimum parameters for the promising cubic Al0.3Ga0.7N/GaN RTD are proposed.

We test a theoretical description of the void size distribution function against direct estimates from halo catalogues of the DEMNUni suite of large cosmological simulations. Besides standard $\Lambda$CDM, we consider deviations of the dark energy equation of state from $w=-1$, corresponding to four combinations in the popular Chevallier-Polarski-Linder parametrisation: $w_0=-0.9;-1.1$, $w_a=-0.3;0.3$. The theoretical void size function model, relying on the Sheth & van de Weygaert double barrier excursion set formalism, provides an accurate description of the simulation measurements for the different dark energy models considered, within the statistical errors. The model remains accurate for any value of the threshold for void formation $\delta_\mathrm{v}$. Its robust consistency with simulations demonstrates that the theoretical void size function can be applied to real data as a sensitive tool to constrain dark energy., Comment: 15 pages, 5 figures and 2 tables

Spin-polarized currents in double-barrier magnetic tunnel junctions (MTJs) as CoFeB/MgO/InP/MgO/CoFeB (MTJs-InP) are investigated by non-equilibrium Green’s function formalism. The asymmetric structures with a half-metal LSMO contact are studied and a spin-diode behavior is found compared to the MTJs-InP. Charge and spin currents as well as spin polarization as a function of bias voltage, angle between magnetizations and quantum-well thickness are also described. A nearly 100% spin polarization is observed at a certain range of bias voltage. Therefore, one can design excellent spin-filter devices based on new MTJs-InP.

We investigate pricing issue of discrete-double barrier options under Levy processes. We first derive an analytical pricing formula, which is no longer applicable when the monitoring frequency becomes large. Therefore, we present a numerical algorithm based on the idea of using discrete variables to approximate continuous ones initiated by Milev and Tagliani (2010) and utilizing adaptive Gauss–Lobatto quadrature with five points to address the integration problem. The method applies for all types of Levy processes whose probability density function of the increment is available in closed form. Numerical experiments confirm that our algorithm is both effective and efficient.

Glass-ceramics are well known for the excellent combination properties provided by their components, a glassy matrix and crystalline phases, and have promising applications in the immobilization and detoxification of solid waste containing toxic metals. Glass-ceramic products were successfully synthesized in CaO-MgO-SiO2-Al2O3 -Cr2O3 system. Two key measures--partitioning ratio of Cr in the spinel and Cr leaching ratio--were used to investigate the mechanism of Cr immobilization in the glass-ceramic products. The results of powder X-ray diffraction revealed that both spinel and diopside were major crystalline phases in the products. The value of x in the MgCr(x)Al(2-x)O4 spinel was highly related to the amount of Cr2O3 added to the glass-ceramic system. As Cr2O3 content increased, the proportion of spinel phase increased, while that of glass phase decreased. The partitioning ratio of Cr in spinel phase was about 70% for 2 wt.% Cr2O3, and increased to 90% when loaded with 10 wt.% of Cr2O3. According to the results of the prolonged toxicity characteristic leaching procedure, the Cr leaching ratio decreased with the increase of Cr partitioning ratio into the spinel phase. The findings of this study clearly indicate that glass-ceramic formed by spinel structure and residual glass successfully immobilized Cr.

We study the quantum size effects of an MgO-based double barrier magnetic tunnel junction with a nonmagnetic-metal (DBMTJ-NM) (semiconductor (DBMTJ-SC)) spacer on the charge current and the spin-transfer torque (STT) components using non-equilibrium Green's function (NEGF) formalism. The results show oscillatory behavior due to the resonant tunneling effect depending on the structure parameters. We find that the charge current and the STT components in the DBMTJ-SC demonstrate the magnitude enhancement in comparison with the DBMTJ-NM. The bias dependence of the STT components in a DBMTJ-NM shows different behavior in comparison with spin valves and conventional MTJs. Therefore, by choosing a specific SC spacer with suitable thickness in a DBMTJ the charge current and the STT components significantly increase so that one can design a device with high STT and faster magnetization switching.

In this paper, under a sufficient and necessary condition, we prove that the double barrier reflected BSDE has a unique square-integrable adapted solution via penalization method.

Resonant tunneling quantum structures consist of asymmetric wells and barriers have been investigated to find their optimized geometrical parameters and potential profile by the numerical calculations. The results show that the widths and the depths of the asymmetric wells have a significant effect on the transmission coefficient and the dwell time. The properties exhibited in this work may establish guidance to the device applications.

We report large tunnel magnetoresistance (TMR) ratios of up to 219% at 300 K and 366% at 3.7 K obtained for a high-quality fully epitaxial double-barrier magnetic tunnel junction (MTJ) composed of Fe/MgO/Fe/γ-Al2O3/Nb-doped SrTiO3. The obtained TMR ratios are among the highest values reported in Fe/MgO/Fe structures. This result may be attributed to the small in-plane wave vectors of the tunneling electrons injected from the Nb-doped SrTiO3 electrode with a small carrier density, demonstrating good compatibility between the Fe-based MTJ and SrTiO3.

Using the model of rectangular potential and smooth position-dependent electron effective mass, which is a linear function of coordinate in near-interface regions between wells and barriers of open double-barrier resonant tunneling nano-structure, the solutions of Schrodinger equation are obtained and transmitting coefficient of the structure is analytically calculated. The influence of the sizes of inner and outer near-interface regions on transmitting coefficient of the structure is investigated. The comparative analysis of resonance energies and resonance widths of sub-barrier electron quasi-stationary states as functions of these sizes is performed. It is shown that the relative differences of resonance energies and resonance widths of the same state of electron in the model of linearly-dependent effective mass and simplified abrupt one do not exceed 1% and 5%, respectively, in physically correct interval of the sizes of outer and inner near-interface regions.

The Co-Fe-B/MgO system with perpendicular magnetic anisotropy finds extensive application in modern magnetic memories. Critical issues for the practical usage of magnetic tunnel junctions (MTJs) include the limited thermal stability of bit storage, and low switching efficiency. This study elucidates the deterministic influence of Co-Fe-B composition and the MgO interface on an MTJ's fundamental magnetic properties, which affect both thermal stability and switching current. Furthermore, the authors observe an anomalous trend in saturation magnetization, which is attributed to a change in magnetic anisotropy.

This paper details the design of an integrate & fire (I & F) neuron ASIC and its integration with a double barrier memristor device. The memristor has a non-volatile analog memory characteristic which changes with time and voltage. The neuron ASIC is designed to interact with the memristor by integrating its current and firing when a certain threshold is reached. The resulting spikes increase the memristor's conductance and consequently the firing rate of neuron increases. Together, the ASIC and the memristor mimics neuromorphic learning on hardware. The ASIC has been fabricated in AMS 350nm process.

With the shrinking of complementary metal oxide semiconductor (CMOS) technology size, the considerable power consumption on logic and memory circuit system has been becoming an unavoidable bottleneck [1]. Spin transfer torque magnetoresistive memories (STT-MRAMs) are prime candidates for non-volatile memory applications. As the basic storage unit of STT-MRAM, magnetic tunnel junction (MTJ) has been extensively studied [2]–[4]. For instance, double-barrier MTJ (DMTJ), taking advantages of the enhancement of STT effect, significantly reduces the critical switching current $(\mathrm {I}_{C0})$ and switching duration $(\tau)$ [5]. MTJ with two CoFeB free layers (FLs) coupled by Ta layer can effectively improves the thermal stability $\left({ \Delta\mathrm {E}}\right)$ [6]. In this paper, we proposed an electrical modeling of DMTJ with CoFeB/Ta/CoFeB FLs (see Fig. 1 (a)). Compared with conventional MTJ, the propose DMTJ has superiorities in $\mathrm {I}_{C0}$, $\tau $, and $ \Delta\mathrm {E}$. It can replace MTJ to reduce the device size, improve the reliability of memory and lower the writing energy consumption. Furthermore, this model integrates the stochastic STT switching behavior, the temperature influence and the variation of the layers' thicknesses, which can deeply affect the reliability of hybrid CMOS/MTJ circuits. Fig. 1 (b) shows the principle block diagram of the integrated physical models. In the following, we explain some key blocks modeled in the Verilog-A code. For DMTJ, STTs generated by both the transmitted and reflected spin polarized electrons add together. This enhancement strongly decreases the $\mathrm {I}_{C0}$ and $\tau $, which can be expressed as\begin{align*} \mathrm {I}_{C0}= 2 \alpha \gamma \mathrm {e}\times (\mathrm {K}_{EFF} \times Volume)/ \mu _{B} \mathrm {g}_{DMTJ}(1) (1)\\ \tau =\left[{ \mathrm {C}+ In \left({ \pi ^{2} \Delta\mathrm {E}/ 4 }\right) }\right] \times (em/ 4 \mu _{B} \mathrm {g}_{DMT} \mathrm {J}) \times (\mathrm {I}_{write}- \mathrm {I}_{C0})^{-1}(2)\end{align*}

Shot noise reveals spin dependent transport properties in a magnetic tunnel junction. We report measurement of shot noise in CoFeB/MgO/CoFeB/MgO/CoFeB double barrier magnetic tunnel junctions, which shows a strong temperature dependence. The Fano factor used to characterize shot noise increases with decreasing temperature. A sequential tunneling model can be used to account for these results, in which a larger Fano factor results from larger spin relaxation length at lower temperatures.

This paper proves the existence and uniqueness of a solution to doubly reflected backward stochastic differential equations where the coefficient is stochastic Lipschitz, by means of the penalization method., Published at https://doi.org/10.15559/17-VMSTA90 in the Modern Stochastics: Theory and Applications (https://www.i-journals.org/vtxpp/VMSTA) by VTeX (http://www.vtex.lt/)

Although female migrant entrepreneurship has gained some momentum during the last decade, research on it is limited, and empirical findings in the German context remain scarce. The entrepreneurial activities of female migrants have long been ascribed to certain industries. Their businesses often remain small with limited prospects for revenue. However, recent developments indicate some emerging changes in terms of female migrant entrepreneurship. Based on the empirical data of the German microcensus, we analyze structural characteristics of female migrant entrepreneurship and its development in Germany between 2005 and 2016. We further examine how selected determinants (qualification, occupational segregation, family responsibilities) can explain these developments, and how these determinants affect the propensity of female migrants to become self-employed. Our findings cast new light on country-specific aspects of female migrant entrepreneurship and the ongoing debate of whether female migrant entrepreneurs face a double barrier of being both women and migrants.

This paper applies the static hedge portfolio approach (SHP) of Chung et al. (2013) in two new directions. First, the SHP approach is generalized from the constant elasticity of variance (CEV) model of Cox (1975) to the jump to default extended CEV (JDCEV) framework of Carr and Linetsky (2006). For this purpose, the recovery value of the American-style down-and-in put is hedged through the one attached to a European-style plain-vanilla contract whereas for an up-and-in put it is necessary to use the recovery component of the corresponding European-style up-and-in option. Second, the SHP methodology is adapted from single to double barrier American-style knock-in options by matching the value of the hedging portfolio along both lower and upper barriers. Finally, and to benchmark the accuracy of the novel SHP pricing solutions, the optimal stopping approach of Nunes (2009) is also extended to price American-style double knock-in options under the JDCEV framework. Such extension highlights the relevant credit derivative component embedded in American-style knock-in equity puts. info:eu-repo/semantics/submittedVersion

External barrier options are two-asset options where the payoff is defined on one asset and the barrier is defined on another asset. In this paper, we derive the Laplace transforms of the prices and deltas for the external single and double barrier options where the underlying asset prices follow a regime-switching model with finite regimes. The derivation is made possible because we can obtain the joint Laplace transform of the first passage time of one asset value and the value of the other asset. Numerical inversion of the Laplace transforms is used to calculate the prices of external barrier options.

In this paper, we establish the polynomial complexity of a primal-dual path-following interior point algorithm for solving semidefinite optimization (SDO) problems. The proposed algorithm is based on a new kernel function which differs from the existing kernel functions in which it has a double barrier term. With this function we define a new search direction and also a new proximity function for analyzing its complexity. We show that if q1 > q2 > 1, the algorithm has \(O((q_1 + 1)n^{\frac{{q_1 + 1}} {{2(q_1 - q_2 )}}} \log \tfrac{n} {e}) \) and \(O((q_1 + 1)^{\frac{{3q_1 - 2q_2 + 1}} {{2(q_1 - q_2 )}}} \sqrt n \log \tfrac{n} {e}) \) complexity results for large- and small-update methods, respectively.

In this paper we simulated a photodetector based on a double barrier GaAs/InGaAs/InAs quantum dots–quantum well hybrid structure, calculated its I–V and C–V characteristic and studied the electronic states of the self-assembled InAs quantum dots embedded in InGaAs and GaAs quantum wells. By optimizing the device structure, ultrahigh sensitivity was obtained. We attributed this high sensitivity to the double barrier structure that effectively lowered dark current. This simulation method can be used to designing and optimizing devices with similar structure.

In recent years, transmission and reception systems of optical signals are widely used. Receiving the optical signal in such systems is carried by photoreceiving modules based on a photodetector, which defines the quality of the received signal, the range and speed of the entire system. However, hitherto used p–i–n- and avalanche photodiodes do not fully meet the growing demands. The present work is devoted to investigate the photovoltaic characteristics of semiconductor thin base transistor structure based on germanium, which is superior the silicon counterparts by speed and gain. Investigated p+–n–p-structures were obtained by diffusion of antimony onto the substrate of p-type germanium to a depth of 1 micron and alloying of indium to the part of its surface which creates diffusion layer of ?+-type and with thickness of 0,5 microns. Experiments have shown that the reverse biasing of a single p+-n-emitter-base junction leads to a smooth increase in reverse current, at the same time when it is connected in series to forward biased collector p-n-junction there is a sharp increase in the current by voltage, giving properties of voltage surge suppressor. This behavior of the current-voltage characteristics can be explained by the punch-through effect when the space charge regions of the emitter junction and the space charge region of collector junction touch each other and the conditions are realized for double carrier injection into a fully depleted region of the transistor. At the same time giving small fixed voltages 0,1—0,15 V to the collector-base junction the output static characteristics can be received with an operating voltage of 3—3,5 V. A characteristic feature of the investigated transistor is that when the base region under illumination by integrated light intensity (50 and 3000 lux) light current appears, whose magnitude with the increase of operating voltage (up to 1.7 V) increases nonlinearly, resulting in increased current photosensitivity up to 17 µA/lux, which is one and a half orders of magnitude greater than photosensitivity of germanium phototransistor “OOA-5”.

The results of the fabrication and study of a double-barrier resonant tunneling structure grown on the basis of GaN and AlN wide-gap materials on a (0001)-oriented sapphire substrate are given. It is shown that, at voltages of ∼3 V, the current-voltage characteristics of resonant tunneling diode samples exhibit a region of negative differential conductivity that disappears upon multiple cyclic measurements. It is also shown that the reversal of sign of the applied voltage restores the initial shape of the current-voltage characteristics and an increase in the temperature of the structure from room temperature to 200°C yields irreversible degradation of the device and a shift of the region of negative differential conductivity to lower voltages

The application of the new structure to the complex field of THz receivers requires the availability of an analytical model, reliable and able to highlight the dependence on the parameters of the physical structure. We present a model of the rectification capability of the double barrier Terahertz radiation (THz) detector, a CMOS compatible structurer. The model is based on the hydrodynamic semiconductor equations; solved in the small signal approximation. The model highlights the high frequency dynamics of carriers in the structure; and furnishes new insight on the origin of the self-mixing rectification process.

The considerable power consumption on logic and memory circuit system will be an unavoidable bottleneck with the shrinking of complementary metal oxide semiconductor (CMOS) technology size. One promising solution is to build non-volatile spintronic device, e.g. spin transfer torque magnetic random access memory (STT-MRAM). The basic storage unit of STT-MRAM, i.e. magnetic tunnel junction (MTJ), has thus been extensively studied. Double-barrier MTJ (DMTJ), as an optimized structure, enhances the STT effect with a second MgO barrier layer and reduces its critical switching current. In this paper, we present a physics-based compact model of CoFeB/MgO DMTJ with perpendicular magnetic anisotropy (PMA). The modeling results show a great agreement with experimental results. More efficient STT switching and similar magnetoresistance features compared with single-barrier MTJ (SMTJ) can be realized. Mixed circuits simulations have also been carried out to validate its functionality. This SPICE-compatible compact model will be useful for high-performance hybrid DMTJ/CMOS circuit and system designs.

We study the effect of the magnetic field on the spin-dependent hole transport through a diluted magnetic semiconductor double barrier heterostrucutre such as Cd1-x Mn x Te/CdTe. Using the transfer matrix, the barrier transparency, polarization efficiency and tunneling lifetime of a light hole and a heavy hole are calculated. The spin separation is found out and is observed that it is the same for both the light and the heavy hole. The heavy hole takes more time to travel in the heterostrucutre than the light hole. The effect of the magnetic field influences the tunneling lifetime. The results give the basic idea about the spin-dependent transport of light and heavy holes.

Existence results for adapted solutions of infinite horizon doubly reflected backward stochastic differential equations with jumps are established. These results are applied to get the existence of an optimal impulse control strategy for an infinite horizon impulse control problem. The properties of the Snell envelope reduce the problem to the existence of a pair of right continuous left limited processes. Finally, some numerical results are provided.

In this paper we present an implementation of pricing algorithm for single and double barrier options using Mellin transformation with Maximum Entropy Inversion and its suitability for real-world applications. A detailed analysis of the applied algorithm is accompanied by implementation in C++ that is then compared to existing solutions in terms of efficiency and computational power. We then compare the applied method with existing closed-form solutions and well known methods of pricing barrier options that are based on finite differences.