Electric Barrier Research Articles

Electric potential barriers in the magnetic nozzle.

Magnetic nozzles are convergent-divergent applied magnetic fields which are commonly used in electric propulsion, manufacturing, and material processing industries. This paper studies the previously overlooked physics in confining the thermalized ions injected from a near-uniform inlet in the magnetic nozzle. Through fully kinetic planar-3V particle-in-cell (PIC) modeling and simulation, an electric potential barrier is found on the periphery of the nozzle throat, which serves to confine the thermalized ions by the electric force. With the initial thermal energy as driving force and insufficient magnetic confinement, the ions overshoot the most divergent magnetic line, which results in the accumulation of positive space charges around the throat. The accumulated charges would create an ion-confining potential barrier with limited extent. Apart from the finite-electron Larmor radius (FELR) effect, two more factors are put forward to account for the limited extent of the potential barrier: the depletion of ion thermal energy and the short-circuiting effect. The influences of inlet temperature ratio of ions to electrons and magnetic inductive strength B_{0} are quantitively investigated using the PIC code. The results indicate that the potential barrier serves as a medium to transfer the gas dynamic thrust to the magnetic nozzle while providing constrain to the ions, like the solid wall in a de Laval nozzle. In high-B_{0} regime, the finite-ion Larmor radius (FILR) effect becomes dominant rather than the FELR effect in the plasma confinement of magnetic nozzles.

Spin- and valley-related tunneling time of massive Dirac electrons in a ferromagnetic MoS2 quantum structure

Abstract We investigate the tunneling time of massive Dirac electrons through an electric barrier in a ferromagnetic quantum structure consisting of normal/ferromagnetic/ normal MoS 2 parts. The results show that the dwell time is not only spin-separated but also valley-separated due to the spin-valley coupling of valence-band edges together with the exchange field. When the electric barrier broadens, the spin-dependent and valley-dependent dwell times increase with oscillating behavior. These behaviors are different from the massless Dirac electrons in graphene. Moreover, both the spin- and valley-dependent dwell times can be effectively modulated by the angle of incidence, the width, and the height of the electric barrier.

ZnO-CuxO heterostructure photocatalyst for efficient dye degradation

A simple aqueous solution process was used for the synthesis of Cu-loaded ZnO nanorod structures in which highly crystalline and hexagonal wurtzite ZnO, cubic CuO and Cu2O phases coexist. Absorption/emission characteristics identify band gap narrowing, which facilitates visible light absorption, as a consequence of hybridization of O 2p bands with Cu 3 d bands of the ZnO-CuxO heterostructure system. With use of the specific band energy position of the individual components (i.e., ZnO, Cu2O, and CuO), photogenerated electrons and holes could be made to migrate separately and thereby the carrier recombination could be delayed, making them amply available for photocatalytic reactions. The available electrons plausibly produce superoxide radical anion (O2·−), while holes generate hydroxyl radicals (·OH), which are reactive agents for dye degradation. Furthermore, the formation of a depletion region via Cu-induced charge separation within the ZnO-CuxO heterostructure and thermal-energy-mediated abstraction of the electric field barriers and subsequent migration of the positively charged defects from the subsurface region toward the interface lead to efficient photocatalytic performance.

Perfect valley filter controlled by Fermi velocity modulation in graphene

In this work we investigate the effects of a Fermi velocity modulation in a valley filter in graphene created by a combination of a magnetic and electric barrier. With the effective Dirac equation of the system, we use the transfer matrix formalism to obtain the transmittance. We verify that the valley transport in graphene is very sensitive to a Fermi velocity modulation, which is able to choose which valley will be filtered with perfect filtering. Also, it is possible to use a Fermi velocity modulation to filter both valleys or to make the valley filter transparent. It reveals that the Fermi velocity is a powerful tool that can be used to tune a graphene valley filter, since it has a total control in its transport properties.

Effect of the dopamine stabilizer (-)-OSU6162 on potentiated incubation of opioid craving after electric barrier-induced voluntary abstinence.

In the classical incubation of drug craving rat model, drug seeking is assessed after homecage forced abstinence. However, human abstinence is often voluntary because negative consequences of drug seeking outweigh the desire for the drug. Here, we developed a rat model of incubation of opioid craving after electric barrier-induced voluntary abstinence and determined whether the dopamine stabilizer (-)-OSU6162 would decrease this new form of incubation. We trained male and female rats to self-administer oxycodone (0.1 mg/kg/infusion, 6 h/day) for 14 days. We then exposed them to either homecage forced abstinence or voluntary abstinence induced by an electric barrier of increasing intensity near the drug-paired lever. On abstinence days 1, 15, or 30, we tested the rats for oxycodone seeking without shock and drug. We also examined the effect of (-)-OSU6162 (7.5 and 15 mg/kg) on oxycodone seeking on abstinence day 1 or after 15 days of either voluntary or forced abstinence. Independent of sex, the time-dependent increase in oxycodone seeking after cessation of opioid self-administration (incubation of opioid craving) was stronger after voluntary abstinence than after forced abstinence. In males, (-)-OSU6162 decreased incubated (day 15) but not non-incubated (day 1) oxycodone seeking after either voluntary or forced abstinence. In females, (-)-OSU6162 modestly decreased incubated oxycodone seeking after voluntary but not forced abstinence. Results suggest that voluntary abstinence induced by negative consequences of drug seeking can paradoxically potentiate opioid craving and relapse. We propose the dopamine stabilizer (-)-OSU6162 may serve as an adjunct pharmacological treatment to prevent relapse in male opioid users.

Gate-controlled spin-valley-layer locking in bilayer transition-metal dichalcogenides.

The interplay between various internal degrees of freedom of electrons is of fundamental importance for designing high performance electronic devices. A particular instance of this interplay can be observed in bilayer TMDs due to the combined effect of spin-orbit and interlayer couplings. We study the transport of spin, valley and layer pseudospin, generally, through a magnetoelectric barrier in AB-stacked bilayer TMDs and demonstrate an electrically controllable platform for multifunctional and ultra-high-speed logic devices. Perfect spin and valley polarizations as well as good layer localization of electrons occur in a rather large range of Fermi energies for moderate electric and magnetic fields. Any number of these polarizations can be inverted by adjusting the two potential gates on the two layers. Furthermore, the conditions for the excellent polarizations are determined for the spin, valley and layer degrees of freedom, in terms of the adjustable system parameters. We discuss the individual electric and magnetic barriers and show that the single electric barrier acts as a bipolar pseudospin semiconductor with opposite polarizations for the conduction and valence bands. The results of this study pave the way for multifunctional pseudospintronic applications based on 2D materials.

St. Lawrence Seaway: Western Great Lakes Basin

The St. Lawrence Seaway connects Lake Superior, Lake Huron, Lake Michigan, Lake Erie and Lake Ontario to the Atlantic Ocean. The lakes and connecting rivers, St. Mary’s, St. Claire, Detroit, Niagara and St. Lawrence, have been a major artery for transportation, migration and trade. The Menominee River flows into Green Bay and Lake Michigan and connects to the St. Lawrence Seaway. The Great Lakes have been sailed for trading and commercial purposes since at least the 17th century. Approximately 6000 ships have sunk killing more than 30,000 sailors and passengers. Cold Canadian winds over the three Western Great Lakes pick up moisture when the lakes are not yet frozen and create snow belts in the states of Wisconsin, Michigan and in Ontario, Canada. The Western Great Lakes moderate the seasonal temperatures as they absorb heat and cool the air in the summer. The lakes radiate heat in the fall. This temperature buffering creates fruit belts further north of where the fruit is traditionally grown. During the 1950s and 1960s all of the Agent Blue, the arsenic containing herbicide used in Vietnam War, was manufactured on the banks of the Menominee River by the Ansul Company at Marinette, Wisconsin. The groundwater and the river bottom are now heavily contaminated with arsenic compounds that were released from 1957 to 1977 by Ansul as a result of the manufacture of the herbicide. The linkage of Lake Michigan to the Mississippi River has allowed Chicago’s wastewater to be disposed of into the tributaries of the Illinois River and Mississippi River to avoid contaminating Lake Michigan the source of Chicago’s drinking water. An unintended consequence of linking the Western Great Lakes basin with the Mississippi River basin was the creation of the wet pathway (Chicago Sanitary and Ship Canal) through which the flying Asian carp is trying to use to get into the Great Lakes. An electric fish barrier was constructed on the Chicago Sanitary and Ship Canal in an attempt to prevent the carp from migrating into Lake Michigan, the Great Lakes basin and the St. Lawrence Seaway. The Western Great Lakes shorelines are actively eroding partly as a consequence of the high surface water levels. In June of 2020 Lake Michigan, Lake St. Claire and Lake Huron experienced the highest water level ever recorded since the 1800s. The high risk erosion areas are retreating at the average rate of 30 cm per year for the last 15 years. Planned urban development in a high risk area helps to prevent the loss of buildings. Locating structures back from lake bluffs promotes natural shorelines and reduces the need for engineered shore protection. Erosion of the sediment under the Mackinac Bridge and pipeline has occurred. The pipeline which carries 87 million liters of oil per day between Sarnia, Ontario and Superior, Wisconsin is at risk.

Corrosion behavior of diamond-like carbon film induced by Al/Ti co-doping

Diamond-like carbon films with Al and Ti dopants (Al/Ti-DLC) were fabricated by a hybrid ion beam deposition system combined with a special design of splicing targets, in which the Al/Ti ratio was changed from 4.0 to 1.1 by tailoring the Al content. The structural evolution and corrosion behavior of Al/Ti-DLC films in 3.5 wt% NaCl solution were systematically investigated by comparing with the 316L SS and pure DLC film. Results revealed that compared with the pure DLC and 316L SS substrate, the Al/Ti-DLC film exhibited enhanced corrosion resistance by reducing the porosity and increasing the barrier for both the charge transfer and the diffusion of corrosive ions into the substrate. In particular, the anti-corrosion behavior of DLC film highly depended on the Al/Ti ratio, which decreased gradually with the Al/Ti ratio ranged from 4.0 to 1.1. Structural and EIS analysis indicated that this was ascribed to both the increased residual stress and sp2 hybridized fraction, which induced not only the formation and propagation of cracks during the corrosion process but also the high electric conductivity and low diffusion barrier of corrosive ions, accelerating the corrosion processes at the film/substrate interface.

Reconfigurable Local Photoluminescence of Atomically-Thin Semiconductors via Ferroelectric-Assisted Effects

Combining a pair of materials of different structural dimensions and functional properties into a hybrid material system may realize unprecedented multi-functional device applications. Especially, two-dimensional (2D) materials are suitable for being incorporated into the heterostructures due to their colossal area-to-volume ratio, excellent flexibility, and high sensitivity to interfacial and surface interactions. Semiconducting molybdenum disulfide (MoS2), one of the well-studied layered materials, has a direct band gap as one molecular layer and hence, is expected to be one of the promising key materials for next-generation optoelectronics. Here, using lateral 2D/3D heterostructures composed of MoS2 monolayers and nanoscale inorganic ferroelectric thin films, reversibly tunable photoluminescence has been demonstrated at the microscale to be over 200% upon ferroelectric polarization reversal by using nanoscale conductive atomic force microscopy tips. Also, significant ferroelectric-assisted modulation in electrical properties has been achieved from field-effect transistor devices based on the 2D/3D heterostructrues. Moreover, it was also shown that the MoS2 monolayer can be an effective electric field barrier in spite of its sub-nanometer thickness. These results would be of close relevance to exploring novel applications in the fields of optoelectronics and sensor technology.

Electro and photon double-driven non-volatile and non-destructive readout memory in Pt/Bi0.9Eu0.1FeO3/Nb:SrTiO3 heterostructures

Ferroelectric resistive switching has recently attracted considerable attention as a promising candidate for next-generation non-volatile memory. In this work, we report an electro and photon double-driven bipolar resistive switching behavior in Pt /Bi0.9Eu0.1FeO3 (BEFO) /Nb-doped SrTiO3 (NSTO) heterostructures prepared via pulsed laser deposition. In addition to the polarization-based control of the resistive memory, a switchable photovoltaic effect is observed that can be used to detect the polarization direction non-destructively. Significantly, the electric field-modulated interfacial barrier can be further affected by photon-generated carriers. This phenomenon is attributed to the barrier modulation in the Pt /BEFO and BEFO /NSTO interfaces by electric field and photon excitation. These results indicate the feasibility of non-volatile and non-destructive readout from ferroelectric memory.

Efficacy of increasing discharge to reduce tow-mediated fish passage across an electric dispersal barrier system in a confined channel

The Electric Dispersal Barrier System (EDBS) in the Chicago Sanitary and Ship Canal (CSSC) was built to limit the interbasin transfer of aquatic invasive species between the Mississippi River Basin and the Great Lakes Basin. Commercial barge traffic, or tows, moving downstream through the EDBS can facilitate the upstream passage of small fish through the barrier by reducing the voltage gradient of the barrier and causing localized upstream return currents. This study tested whether it is possible to prevent upstream passage of small fish across the barrier by preventing upstream return currents. Measurements of water velocity, voltage gradient, and tow speed, as well as sonar-based observations of resident fish, were made as a tow transited the EDBS moving downstream. The results indicate that upstream return currents can be prevented for typical flow conditions in the CSSC (ambient velocity = 0.15 to 0.23 m/s) when tow speeds are <0.46 m/s. Similarly, increasing the ambient velocity above typical values can prevent upstream return currents for faster tow speeds and larger tows. Additionally, preventing upstream return currents at the EDBS may reduce, but does not prevent, tow-mediated upstream fish passages because tows also cause a temporary reduction in the streamwise voltage gradient at the EDBS. These results have implications for the management of invasive bigheaded carps in the Illinois Waterway.

(Invited) Computational Modeling of Grain Boundary Electrostatic Effect Inpolycrystalline SrTiO3 Thin Film

Understanding the leakage current caused by charge transport and local accumulation in dielectric oxides is critical for predicting and extending the lifetime of dielectric‐based electronic devices. The internal interfaces such as grain boundaries (GBs) inside a dielectric induce local strain and charge segregation and thus further influence the charge transport behavior. In this work, we employ computational modeling based on the Schottky barrier model and nonlinear Nernst-Planck transport equation is used to study the oxygen vacancy transport and leakage current evolution in a SrTiO3 thin film under a DC bias with planar electrodes. It is found that in polycrystalline SrTiO3, the GB‐bounded donors create an electric potential barrier and a local depletion region near the GBs, impeding the oxygen vacancy transport and suppressing the leakage current increase compared to a single crystal SrTiO3 thin film. The effects of temperature, the magnitude of an applied field, the number density of GBs, the GB‐bounded donor concentration, and the depletion layer width on the leakage current evolution are systematically investigated. The simulation results are compared with the analytical solutions, as well as with existing theoretical and experimental reports. This work thus helps shed light to the grain‐structure dependent electrostatic behaviors in dielectric thin films under different intrinsic and extrinsic conditions.

Electrical behaviors of a piezoelectric semiconductor fiber under a local temperature change

We study the effects of a local temperature change on the electrical behaviors of a piezoelectric semiconductor fiber in extensional deformation. A one-dimensional model for thin fibers derived previously from the macroscopic theory of thermopiezoelectric semiconductors is used. Through a combined theoretical and numerical analysis, it is shown that a local temperature change produces a local electric potential barrier and a potential well, which prohibits the flow of currents along the fiber unless the voltage is above a temperature-dependent critical value. The results are useful for thermally manipulating the currents in the fiber and have potential applications in piezotronics.

Anisotropy transport in monolayer black phosphorus under period magnetic modulation

We theoretically investigate the transport through a planar magnetic and electric barrier on the surface of monolayer black phosphorus (BP). In monolayer BP superlattice system, there are two different kinds of mechanics that block the transmission: One comes from the shift of gap in the energy spectrum induced by the magnetic field, the other comes from the enhanced superlattice minigap effect by the resonant coupling. There is strong anisotropic conductances along different directions, which caused by unique band structure. We find that the conductance ratio can be equal to 1 or -1, which can be controlled by tuning the incident energy, the magnetic field and the number of parallel magnetic modulation. This behavior offers us an efficient way to control the anisotropy transport and pave a way to construct monolayer black phosphorus-based electronic devices.

Spin-dependent transport in Normal/Ferromagnetic/Normal monolayer zigzag molybdenum disulfide nanoribbon junction

In this paper, with the three-band tight-binding model, we investigate spin transport in Normal/Ferromagnetic/Normal monolayer zigzag molybdenum disulfide nanoribbon junction with double electric barriers using Green’s function technique. We discuss the influence of the height of the double electric barrier on spin transport. The results demonstrate that spin conductance has relatively large dependence on electric field modulation. We can obtain large spin polarization in low energy region which may be applied as a spin filter. In addition, we study the effect of magnetic field, and we find that we can obtain a larger spin polarization area which may provide a theoretical basis for spin filter application.

Valley switch effect based on monolayer WSe2 modulated by circularly polarized light and valley Zeeman field

The high-quality monolayer (ML) WSe2 leads to the possibility of an efficient manipulation of the spin and valley degrees of freedom. Here considering valley Zeeman field, which refers to the strongly anisotropic lifting of the degeneracy of the valley pseudospin degree of freedom using an external magnetic field, we investigate the spin and valley transport properties in the ML WSe2 quantum structure with circularly polarized light. Without valley Zeeman field, it is obviously found that the valley-dependent transmission can be well modulated by the orientation of circularly polarized light. The valley-dependent transmission can be filtered by the right () circularly polarized light, while the perfect filtering effect of K valley-dependent transmission occurs when the left () circularly polarized light irradiates. In the presence of valley Zeeman field, the valley-dependent transmission presents more interesting phenomena by controlling the orientation of circularly polarized light. When the circularly polarized light is applied, the valley polarization can be turned 100% to −100% with the enhancement of the effective energy about circularly polarized light. However, irradiating the circularly polarized light only 100% valley polarization can be obtained, which is independent of the effective energy of circularly polarized light and the height of electric barrier. Moreover, the results show that the valley polarization can also be from 100% to −100% in this device by adjusting the valley Zeeman field coupled with electrical field. Thus a two-way switch is formed in this quantum structure. These intriguing features indicate that the ML WSe2 structure is a promising candidate for future valleytronics devices, for valley switch, valley filter.

Catalyst-Selective Growth of Single-Orientation Hexagonal Boron Nitride toward High-Performance Atomically Thin Electric Barriers.

The ability to control the crystal orientation of 2D van der Waals (vdW) layered materials grown on large-scale substrates is crucial for tailoring their electrical properties, as well as for integration of functional 2D devices. In general, multiple orientations, i.e., two or four orientations, appear through the crystal rotational symmetry matching between the material and its substrate. Here, it is reported that hexagonal boron nitride (h-BN), an ideal electric barrier in the family of 2D materials, has a single orientation on inclined Cu (1 0 1) surfaces, where the Cu planes are tilted from the (1 0 1) facet around specific in-plane axes. Density functional theory (DFT) calculation indicates that this is a manifestation of only one favored h-BN orientation with the minimum vdW energy on the inclined Cu (1 0 1) surface. Moreover, thanks to the high interfacial strength with the underlying Cu, the single-orientation h-BN is free of thermal wrinkles, and exhibits a spatially homogeneous morphology and tunnel conductance. The findings point to a feasible approach to direct growth of single-orientation, wrinkle-free h-BN thin film for high-performance 2D electrical devices, and will be of benefit for controllable synthesis of other vdW materials.

Effects of a vertical electric barrier on the behaviour of Rainbow Trout

When dealing with invasive fishes, permanent barriers may inhibit spread, but may not be feasible due to costs and logistical constraints. Alternatively, non-permanent barriers using electricity, light, sound, pressure, bubbles, and CO2 are being developed and deployed in efforts to limit and prevent the spread of aquatic invasive species or to achieve fish guidance and conservation. However, the effectiveness of these barriers is quite variable and testing is often lacking for both invasive and native species. We conducted a laboratory experiment to investigate the impact of vertical electric barrier on behaviour of Rainbow Trout, Oncorhynchus mykiss. In response to electric current, Rainbow Trout responded by significantly decreasing passage through the electric barrier zone and spending more time away from the electric barrier when it was turned on during the stimulus period compared to pre-stimulus period. Moreover, when interacting with electric barrier, Rainbow Trout exhibited certain behaviours (e.g. stunned and remained on the same side of the barrier, stunned and crossed the barrier) more than others (e.g. approach and retreat, deflected, and paralyzed). Moreover, it appears that Rainbow Trout remained distant from the electric barrier even after the electric barrier was turned off. Our results indicate that relatively weak electric gradient (i.e. voltage gradient: 0.2 – 0.4 v·cm−1, power density: 3 – 42 µW·cm−3) can inhibit the movement of Rainbow Trout. Our results also highlight the importance of detailed investigation of behavioural responses of target species when evaluating and considering fish-deterrent or guidance technologies.

Photoelectric Properties of GaN Layers Grown by Plasma-Assisted Molecular-Beam Epitaxy on Si(111) Substrates and SiC/Si(111) Epitaxial Layers

The photoelectric properties of GaN/SiC/Si(111) and GaN/Si(111) heterostructures grown by plasma-assisted molecular-beam epitaxy under the same growth conditions on identical silicon substrates, but with different buffer layers, are experimentally investigated. The GaN/SiC/Si(111) structure is formed on a Si substrate with the SiC buffer layer grown by a new atom-substitution technique and the GaN/Si(111) structure, on a Si substrate subjected to pre-epitaxial plasma nitridation. The significant effect of carbon-vacancy clusters contained in the SiC layer on the growth of the GaN layer and its optical and photoelectric properties is found. It is experimentally established that the GaN/SiC/Si(111) heterostructure has a higher photosensitivity than the GaN/Si(111) heterostructure. In the GaN/SiC/Si(111) heterostructure, the coexistence of two oppositely directed p–n junctions is observed. One p–n junction forms at the SiC/Si interface and the other, at the GaN/SiC interface. It is shown that the occurrence of an electric barrier in the GaN/Si(111) heterostructure at the GaN/Si(111) heterointerface is caused by the formation of a thin silicon-nitride transition layer during pre-epitaxial plasma nitridation of the Si(111) substrate.

Computational modeling of grain boundary electrostatic effect in polycrystalline SrTiO3 thin film

AbstractUnderstanding the leakage current caused by charge transport and local accumulation in dielectric oxides is critical for predicting and extending the lifetime of dielectric‐based electronic devices. The internal interfaces such as grain boundaries (GBs) inside a dielectric induce local strain and charge segregation and thus further influence the charge transport behavior. In this work, we employ computational modeling based on the Schottky barrier model and nonlinear Nernst‐Planck transport equation is used to study the oxygen vacancy transport and leakage current evolution in a SrTiO3 thin film under a DC bias with planar electrodes. It is found that in polycrystalline SrTiO3, the GB‐bounded donors create an electric potential barrier and a local depletion region near the GBs, impeding the oxygen vacancy transport and suppressing the leakage current increase compared to a single crystal SrTiO3 thin film. The effects of temperature, the magnitude of an applied field, the number density of GBs, the GB‐bounded donor concentration, and the depletion layer width on the leakage current evolution are systematically investigated. The simulation results are compared with the analytical solutions, as well as with existing theoretical and experimental reports. This work thus helps shed light to the grain‐structure dependent electrostatic behaviors in dielectric thin films under different intrinsic and extrinsic conditions.