Triple Barrier Research Articles

Resonant Tunneling Properties in The Sawtooth Triple Barrier Structures

The resonance tunneling properties of sawtooth triple barrier double-well structures were investigated using the non-equilibrium Green's functions method. The dependence of resonance energies on barrier height and width and well widths was investigated. The tunneling feature of the structure under the electric field was investigated. It has been observed that the transmission probability, resonance tunneling energy, and resonance peak intensity are sensitively dependent on the applied electric field and structure parameters. By choosing the appropriate structure, devices that provide resonance transition at the desired energy can be designed in the desired energy level ranges. Thus, this study can provide a basis for switching and oscillator source nano-device designs.

Enhanced Genetic-Algorithm-Driven Triple Barrier Labeling Method and Machine Learning Approach for Pair Trading Strategy in Cryptocurrency Markets

In the dynamic world of finance, the application of Artificial Intelligence (AI) in pair trading strategies is gaining significant interest among scholars. Current AI research largely concentrates on regression analyses of prices or spreads between paired assets for formulating trading strategies. However, AI models typically exhibit less precision in regression tasks compared to classification tasks, presenting a challenge in refining the accuracy of pair trading strategies. In pursuit of high-performance labels to elevate the precision of classification models, this study advanced the Triple Barrier Labeling Method for enhanced compatibility with pair trading strategies. This refinement enables the creation of diverse label sets, each tailored to distinct barrier configurations. Focusing on achieving maximal profit or minimizing the Maximum Drawdown (MDD), Genetic Algorithms (GAs) were employed for the optimization of these labels. After optimization, the labels were classified into two distinct types: High Risk and High Profit (HRHP) and Low Risk and Low Profit (LRLP). These labels then serve as the foundation for training machine learning models, which are designed to predict future trading activities in the cryptocurrency market. Our approach, employing cryptocurrency price data from 9 November 2017 to 31 August 2022 for training and 1 September 2022 to 1 December 2023 for testing, demonstrates a substantial improvement over traditional pair trading strategies. In particular, models trained with HRHP signals realized a 51.42% surge in profitability, while those trained with LRLP signals significantly mitigated risk, marked by a 73.24% reduction in the MDD. This innovative method marks a significant advancement in cryptocurrency pair trading strategies, offering traders a powerful and refined tool for optimizing their trading decisions.

Hole-tunneling Si0.82Ge0.18/Si triple-barrier resonant tunneling diodes with high peak current of 297 kA/cm2 fabricated by sputter epitaxy

Hole-tunneling Si0.82Ge0.18/Si asymmetric triple-barrier (TB) resonant tunneling diodes (p-RTDs) were created by sputter epitaxy instead of conventional chemical vapor phase epitaxy. As a result, a peak current density (PCD) of 297 kA/cm2 with a peak-to-valley current ratio of 7.3 was recorded at room temperature. The observed high planarity of the films grown by sputter epitaxy is also considered one of the factors behind the high PCD. From the results of self-consistent theoretical calculations of current–voltage characteristics using box-shaped potentials as a first approximation and considering space charge effects of quantum wells, heavy-hole-to-heavy-hole and light-hole-to-light-hole state transitions under the tunneling conditions of the TB potential structure applied in this study were found to be inherent current paths. Moreover, the light and heavy hole currents contribute almost equally to the overall device current, resulting in a theoretical PCD of 637 kA/cm2, which is close to the experimental result. Further analytical simulations with adjusted series resistance and thickness of the nondoped layer allowed the alignment of the theoretically obtained PCD voltage position with the experimentally obtained one. Thus, the theoretical and analytical calculations explain the operation mechanisms of SiGe/Si p-RTDs, and the proposed fabrication method using our sputter epitaxy method is very useful for the actual production of high-PCD SiGe/Si p-RTDs operating at room temperature.

Magnetic field effect on tunneling through triple barrier in AB bilayer graphene

We investigate electron tunneling in AB bilayer graphene through a triple electrostatic barrier of heights Ui(i=2,3,4) subjected to a perpendicular magnetic field. By way of the transfer matrix method and using the continuity conditions at the different interfaces, the transmission probability is determined. Additional resonances appear for two-band tunneling at normal incidence, and their number is proportional to the value of U4 in in the case of U2<U4. However, when U2>U4, anti-Klein tunneling increases with U2. The transmission probability exhibits an interesting oscillatory behavior when U3>U2=U4 and U3<U2=U4. For fixed energy E=0.39γ1, increasing barrier widths increases the number of oscillations and decreases Klein tunneling. The interlayer bias creates a gap for U2<U3<U4 and U3>U2=U4. In the four-band tunneling case, the transmission decreases in T++, T+− and T−− channels in comparison with the single barrier case. It does, however, increase for T−+ when compared to the single barrier case. Transmission is suppressed in the gap region when an interlayer bias is introduced. This is reflected in the total conductance Gtot in the region of zero conductance. Our results are relevant for electron confinement in AB bilayer graphene and for the development of graphene-based transistors.

Simulation of Gallium Nitride/Aluminum Nitride-Based Triple Barrier Quantum Region for ULTRARAM Application

ULTRARAM is a low-power, high-speed, nonvolatile compound semiconductor memory device that uses triple barrier resonance tunneling (TBRT) to store electrical charge in a floating gate. Using a self-consistent solution of Schrödinger-Poisson equations, we investigated the electrical properties, transmission spectra, and electron dynamics across GaN/AlN TBRT region for the ULTRARAM application. The simulation results show that GaN/AlN exhibits tunable electrical properties by using a TBRT region of variable thickness. Successive optimization and testing of various thicknesses significantly altered the transmission across multiple barriers and localization of electrons in the quantum wells. The program/erase (P/E) operation of GaN/AlN-based ULTRARAM in a triple barrier structure is accomplished at less than 2 V. The device’s excellent nonvolatility is due to the conduction band offset (CBO) of GaN/AlN heterostructure providing a large energy barrier (2.1 eV), which prevents electrons from escaping from the floating gate. Because of the low voltage operation and small capacitance, the switching energy consumption is much lower than that of a standard floating gate Flash.

Defect formation in InGaAs/AlSb/InAs memory devices

ULTRARAMTM is a novel floating-gate nonvolatile memory in which the oxide barrier of flash is replaced by a triple-barrier resonant tunneling structure comprising of multiple InAs/AlSb heterojunctions. The quality of the triple barrier resonant tunneling heterostructure of an ULTRARAMTM device in terms of interface sharpness and the presence of defects was analyzed by cross-sectional scanning tunneling microscopy. We observed two different types of defects: stacking faults originating in the layers below the triple barrier resonant tunneling structure and AlSb accumulations at the interface between the lower AlSb layer of the triple barrier resonant tunneling structure and the InGaAs channel. The InGaAs surface of a second sample was measured by atomic force microscopy in order to investigate whether its unevenness is caused by deposition of the AlSb layer or it is already present before the AlSb deposition process.

Klein Tunneling through Triple Barrier in AB Bilayer Graphene

AbstractThe transport properties of charge carriers in AB bilayer graphene through a triple electrostatic barrier are investigated. The transmission and reflection using the boundary conditions together with the transfer matrix method are calculated. For energy less than the interlayer coupling γ1, it is shown that, at normal incidence, transmission is completely suppressed in the gap for a large barrier width while it appears in the gap for the opposite case. For energy greater than γ1, it is shown that in the absence of an interlayer potential difference, transmission is less than that of a single barrier, but in its presence, transmission in the gap region is suppressed, as opposed to a double barrier. It is found that one, two, or three gaps can be created depending on the number of interlayer potential differences applied. Resonance in the transmission channel is observed that is not seen in the single and double barrier cases. Finally, the conductance is computed and it is shown that the number of peaks is greater than the double and single barrier cases. The results here enable the development of graphene‐based transistors.

Novel triple barrier potential for axial gravitational perturbations of a family of Lorentzian wormholes

We study the behavior of a specific Lorentzian wormhole family under gravitational perturbations. In earlier work (EPJC 80:850, 2020), we have proved the stability of a test scalar field in the background of the wormhole family, where the effective potential was that of a double barrier. Continuing with the stability analysis, here we focus on the more physically relevant scenario, that of axial gravitational perturbations. Interestingly, we find that the effective potential is a triple barrier for lower angular momentum modes. This raises important questions on the ringdown of the corresponding wormhole geometry as well as the gravitational wave echo profile that we try to answer through our work. We study in detail how the geometry of each member wormhole affects the quasinormal modes, the time evolution of the signal as well as echoes which are, in general, very feeble in comparison to the main signal. Different ‘cleaning’ techniques have been used to obtain the echo profile in the time evolution of the signal. Lastly, we dwell on the possibility of our wormhole family as a candidate black hole mimicker, as long as its stability is proven under all kinds of perturbations. We briefly present a comparison of the ringdown characteristics of these wormholes with that of a black hole, in support of this speculation.

Simulation and Comparative Study of Resonant Tunneling Diode

This paper studies and investigates the effect of physical and electrical parameters on double, triple and six barrier resonant tunneling diodes (RTD). The materials used for quantum well and barriers are Gallium arsenide (GaAs) and Aluminium gallium arsenide (AlGaAs), respectively. The parameters that were reasoned and studied include conduction band, current density, transmission coefficient and resonance energy. The above parameters were studied by changing bias voltage, temperature, barrier width and doping concentration. From the simulations performed it is observed that for double barrier RTD the peak current density is observed at 0.2 V and the valley current density is observed at 0.3 V, whereas for a triple barrier RTD the peak current density is observed at 0.015 V and the valley current density is observed at 0.06 V. The value of transmission coefficient for double barrier RTD decreases especially after bias applied is more than resonant bias (0.2 V). The effect of increasing bias leads to a decrease in the resonance level in the conduction band. The width of resonance energy decreases with the increase in barrier width. With increase in number of barrier the number of resonance level increases which leads to an increasing peaks in the transmission coefficient curve. The effect of increasing temperature leads to higher current and more resonance energy. With the thickening of barrier width, less transmission of electrons occurs leading to a reduced current density. When the barriers are increased the negative differential region (NDR) is achieved at low voltages.&#x0D; HIGHLIGHTS&#x0D; &#x0D; This paper studies and investigates the effect of physical and electrical parameters on double, triple and six barrier resonant tunneling diodes (RTD)&#x0D; The parameters include conduction band, current density, transmission coefficient, and resonance energy&#x0D; The parameters were studied by changing bias voltage, temperature, barrier width, and doping concentration&#x0D; It is observed that for double barrier RTD the peak current density is observed at 0.2 V and the valley current density is observed at 0.3 V&#x0D; For a triple barrier RTD the peak current density is observed at 0.015 V and the valley current density is observed at 0.06 V&#x0D; &#x0D; GRAPHICAL ABSTRACT

Interfacial Engineering of Binder-Free Janus Separator with Ultra-Thin Multifunctional Layer for Simultaneous Enhancement of Both Metallic Li Anode and Sulfur Cathode.

Exploring a scalable strategy to fabricate a multifunctional separator is of great significance to overcome the challenges of lithium polysulfides (LiPSs) and dendritic growth in lithium-sulfur batteries (LSBs). Herein, a binder-free Janus separator is constructed by interfacial engineering. At the cathode interface, an ultra-thin covalent triazine piperazine film containing tailorable micropores and adsorption sites is decorated on polyacrylonitrile (PAN) membrane by in situ interfacial polymerization, building a triple barrier for LiPSs. The combination of steric hindrance and chemical adsorption reduces LiPS's migration by 81.85%. Meanwhile, at the anode interface, a fast-ionic conductor Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO) is created on the surface of PANnanofiber by magnetron sputtering to suppress dendrite growth. Even though there is no binder between the ceramic layer and the fibrous separator, sputtering creates an inter-embedded structure that ensures no depowering after cycling. Furthermore, the PAN-based separator displays a high temperature tolerance of 180°C. Consequently, the cell delivers a high capacity of 1287.9 mAh g-1 at 0.5 C and stable cycling performance with an ultra-low capacity decay rate of 0.059% per cycle over 500 cycles. This work provides a scalable strategy for functionalizing separators to tackle the challenges in LSBs, which is binder-free, stripping-free, and essentially thickening-free.

Implications of Philately in Highlighting Geometric Features for the Primary Cycle

The development of mathematical skills, especially those specific to geometry, for the primary cycle is a triple challenge in the current context of education in Romania. The first of the challenges is given by the fact that classical education, but also the online one, has become an activity, still unstructured, concerning movements, decisions, and political pressures, implicitly with the changes that occurred in the ministerial apparatus. The second challenge is given by the methodological changes and of the school curriculum, which comes as a completion of the first challenge, being felt even in the teaching-learning-evaluation specific to geometry. The third challenge is given by the weight that teachers face in making geometry a discipline that appeals to students, attractive. In this sense, the challenge for us is to show that this triple barrier can be overcome. As such, the present study proposes a mixed method of presenting the geometric contents in the classroom for the preparatory group, class I and II, through the prism of the instruments offered by the Romanian thematic philately. The results of the study are presented in the form of worksheets, of which we present only fragments to summarize the possibilities arising from the association of thematic philately with notions of geometry.

Implications of Philately in the Development of Mathematical Skills for the Primary Cycle

The development of mathematical skills for the primary cycle is a triple challenge in the current context of education in Romania. The first of the challenges is given by the fact that education has become an activity still unstructured with political movements and decisions, implicitly with the changes that have taken place in the ministerial apparatus. The second challenge is given by the methodological changes and of the school curriculum, which comes as a completion of the first challenge, and the third challenge is given by the weight of the teachers in making mathematics an attractive discipline. In this sense, the challenge for us is to show that this triple barrier can be overcome. As such, in the present study, a mixed-method of presenting the mathematical contents in the classroom is proposed, especially for the preparatory group, class I and II, through the prism of the instruments offered by the Romanian thematic philately. The results of the study are presented in the form of worksheets, of which we present only excerpts to summarize the possibilities arising from the association of philately with notions of mathematics training for the primary cycle.

Investigation of high threshold voltage E-mode AlGaN/GaN MIS-HEMT with triple barrier layer

A comprehensive study on an E-mode AlGaN/GaN MIS-HEMT with triple barrier layer is conducted by Silvaco TCAD software. The effect of geometric parameters of gate dielectric layer, including the length of both sides and the recessed depth, on the device is studied. The simulation results show that the optimized device can reach a high threshold voltage (from 1.24 V to 2.06 V), a large maximum drain current (from 0.925 A/mm to 1.044 A/mm), and a large gate-source capacitance (from 1837 fF/mm to 3100 fF/mm) on the condition that frequency is 1 MHz. Furthermore, based on the analysis of different combinations of the triple structural parameters, two types suitable for specific conditions are concluded, which is helpful to further improve DC and RF characteristics of E-mode AlGaN/GaN MIS-HEMT.

Transmittance on combinatorial structures of triple potential barriers

Semiconductor materials used as potential barriers in the study are GaAs, GaSb, and AlAs. These materials will be arranged in certain combinations to form triple potential barrier structures and the effect of combinations will be analysed against transmission coefficient values. In this study, the maximum energy of the electron is 1 eV and the matrix propagation method is used where the effect of the combinations structure on transmission coefficient values is numerically analysed using a computational program. The results showed that the structuring potential barrier affects the value of the transmission coefficient. In the uniform barriers arrangements, the value of the transmission coefficient decreases with increasing potential barrier energy. Whereas in the arrangement of different barrier combinations, two opposing combination arrangements have the same transmission coefficient values. Thus, from six combination arrangements, there are three kinds of transmission coefficient values. The maximum transmission coefficient value is 1.000 in the triple potential barrier of GaSb at 0.49 eV. Research on the tunnel effect contributed to the development of electronic and optoelectronic devices such as transistors and lasers.

Effect of position-dependent effective mass on electron tunneling of InAs/GaSb type-II superlattice having triangular and parabolic geometries

In a recent paper, we presented transmission probability of a triple quantum well triple barrier structure having triangular and parabolic geometries in presence of finite thick contact barriers using propagation matrix method for InAs/GaSb type-II superlattice. In this letter, effect of different barriers and wells widths and wells geometry are independently studied on transmission coefficient, and also for a specified structure, material composition of barriers is varied to observe the tunnelling effect. We show that the number of peaks in transmission (-ln(Trans(E))) for 30 nm wells width and 10 nm barriers width is more than10nm wells width and 30 nm barriers width.

The effects of the intense laser field on the resonant tunneling properties of the symmetric triple inverse parabolic barrier double well structure

Transmission properties of an electron in the symmetric triple inverse parabolic barrier double well structure have been investigated under the intense laser field. We have found that the laser field has effects on tunneling states through the structure. By altering the structure parameter and intensity of the laser field, it can accommodate a blue or red shift in the electronic spectra according to the purpose, and these results can be used to tune and control the electronic and optic properties of these systems. We see that under the intense laser field conditions, the well width and width parameters are the effective structural parameters in determining the resonance energy. The transmission amplitude decreases at the first and second resonance energy by increasing well width. The increment of the well width causes the incident electron waves to be localized. Consequently, the transmittance decreases, and resonant peak becomes small or disappear.

Dual-Modified Liposome for Targeted and Enhanced Gene Delivery into Mice Brain.

The development of neuropharmaceutical gene delivery systems requires strategies to obtain efficient and effective brain targeting as well as blood-brain barrier (BBB) permeability. A brain-targeted gene delivery system based on a transferrin (Tf) and cell-penetrating peptide (CPP) dual-functionalized liposome, CPP-Tf-liposome, was designed and investigated for crossing BBB and permeating into the brain. We selected three sequences of CPPs [melittin, Kaposi fibroblast growth factor (kFGF), and penetration accelerating sequence-R8] and compared their ability to internalize into the cells and, subsequently, improve the transfection efficiency. Study of intracellular uptake indicated that liposomal penetration into bEnd.3 cells, primary astrocytes, and primary neurons occurred through multiple endocytosis pathways and surface modification with Tf and CPP enhanced the transfection efficiency of the nanoparticles. A coculture in vitro BBB model reproducing the in vivo anatomophysiological complexity of the biologic barrier was developed to characterize the penetrating properties of these designed liposomes. The dual-functionalized liposomes effectively crossed the in vitro barrier model followed by transfecting primary neurons. Liposome tissue distribution in vivo indicated superior ability of kFGF-Tf-liposomes to overcome BBB and reach brain of the mice after single intravenous administration. These findings demonstrate the feasibility of using strategically designed liposomes by combining Tf receptor targeting with enhanced cell penetration as a potential brain gene delivery vector. SIGNIFICANCE STATEMENT: Rational synthesis of efficient brain-targeted gene carrier included modification of liposomes with a target-specific ligand, transferrin, and with cell-penetrating peptide to enhance cellular internalization. Our study used an in vitro triple coculture blood-brain barrier (BBB) model as a tool to characterize the permeability across BBB and functionality of designed liposomes prior to in vivo biodistribution studies. Our study demonstrated that rational design and characterization of BBB permeability are efficient strategies for development of brain-targeted gene carriers.

Effects of water table on ground-borne vibration screening effectiveness by using open trenches

The seasonal variations in groundwater table would significantly change the dynamic responses of the ground and the screening performances of wave barriers. This paper develops a two-dimensional finite element model based on COMSOL to describe the propagation of waves in a layered ground with open trenches. This layered ground is modelled as a dry layer resting on a saturated half-space. The influence of the moving groundwater table on isolation efficiency of barriers is then investigated, considering the infiltrated water in trenches. The effects of soil hydraulic properties and geometrical parameters of the trench are also analyzed respectively. Results show that a low value of the permeability coefficient of saturated half-space may have a significantly detrimental effect on the screening performance due to the low frequency behaviors of the medium. Placing a trench in vibration-strengthening (weakening) zones results in a better (worse) isolation effect, and with a critical water table (Hw,c), increasing trench depth and width can hardly achieve a satisfactory screening efficiency (75% reduction) due to the occurrence of resonance in the dry layer. In addition, a multiple trench isolation system is simulated in the condition of high water levels and its shielding performance is compared to the single trench barrier. A triple trench barrier is found to be a preferred alternative because it can achieve a much better screening efficiency. Specially for Hw,c, a multiple trench barrier can effectively eliminate the adverse effect of the resonance and achieve more than 75% reduction of ground vibration.

Spin dependent resonant electron tunneling through planar graphene barriers

We study spin-dependent electron transport properties of two dimensional graphene double and triple barrier junctions via first-principles calculations. The double barrier junction consists of two graphene leads, a quantum well of zigzag graphene nanoribbon (ZGNR) in the center, and two vacuum barriers separating the ZGNR from the two leads. Resonant electron tunneling occurs when the energy bands of graphene and ZGNR are well aligned in energy and wavevector. Highly spin-polarized electron transmission arises in such junctions when the two edges of the center ZGNR are in the ferromagnetic configuration. The spin polarization of the electron transmission at the Fermi energy can be tuned by gate voltage. We further investigate the dependence of the electron transmission on the width of the ZGNR, effects on barrier height when replacing vacuum by h-BN, and the consequence of replacing a double barrier by a triple barrier.

Tailored microstructures of gadolinium zirconate/YSZ multi-layered thermal barrier coatings produced by suspension plasma spray: Durability and erosion testing

This work employed an axial suspension plasma spray (SPS) process to deposit two different gadolinium zirconate (GZ) based triple layered thermal barrier coatings (TBCs). The first was a ‘layered’ TBC (GZ dense/GZ/YSZ) where the base layer was YSZ, intermediate layer was a relatively porous GZ and the top layer was a relatively dense GZ. The second triple layered TBC was a ‘composite’ TBC (GZ dense/GZ + YSZ/YSZ) comprising of an YSZ base layer, a GZ + YSZ intermediate layer and a dense GZ top layer. The as sprayed TBCs (layered and composite) were characterized using SEM/EDS and XRD. Two different methods (water intrusion and image analysis) were used to measure the porosity content of the as sprayed TBCs. Fracture toughness measurements were made on the intermediate layers (GZ + YSZ layer of the composite TBC and porous GZ layer of the layered TBC respectively) using micro indentation tests. The GZ + YSZ layer in the composite TBC was shown to have a slightly higher fracture toughness than the relatively porous GZ layer in the layered TBC. Erosion performance of the as sprayed TBCs was evaluated at room temperature where the composite TBC showed higher erosion resistance than the layered TBC. However, in the burner rig test conducted at 1400 °C, the layered TBC showed higher thermal cyclic lifetime than the composite TBC. Failure analysis of the thermally cycled and eroded TBCs was performed using SEM and XRD.