Current Switching Effect Research Articles

Robust topological bound states in the continuum in a quantum Hall bar with an anti-dot

Bound states in the continuum (BICs) are quantum states with normalizable wave functions and energies that lie within the continuous spectrum for which extended or dispersive states are also available. These special states, which have shown great applicability in photonic systems for devices such as lasers and sensors, are also predicted to exist in electronic low-dimensional solid-state systems. The non-trivial topology of materials is within the known mechanisms that prevent the bound states to couple with the extended states. In this work we search for topologically protected BICs in a quantum Hall bar with an anti-dot formed by a pore far from the borders of the bar. The bound state energies and wavefunctions are calculated by means of the Recursive S-Matrix method. The resulting bound state energies coexist with extended states and exhibit a pattern complimentary to the Hofstadter butterfly. A symmetry-breaking diagonal disorder was introduced, showing that the BICs with energies far from the Landau levels remain robust. Moreover, the energy difference between consecutive BICs multiplied by the anti-dot perimeter follows the same curve despite disorder. Finally, a BIC-mediated current switching effect was found in a multi-terminal setup for zero and finite temperature, which might permit their experimental detection.

All-Optically Controlled Topological Current Switcher Based on Silicene-Like Nanoribbons

Low-dimensional topological insulator materials, such as silicene-like 2-D materials, have wide applications in electronic, spintronic, and optoelectronic nanodevice, by utilizing their topologically protected edge states. In theoretical studies, Floquet theorem is usually employed in the nanosystems under light irradiation with high-frequency approximation, which may not be accessible in experimental research. In this work, we study the quasienergy spectra and edge-state transport of silicene-like nanoribbons under low-frequency light irradiation (in visible wavelengths), by extracting the zero-photon component from the nonperturbative Floquet bands. These silicene-like nanoribbons undergo topological phase transition from quantum spin Hall (QSH) to quantum anomalous Hall (QAH) insulator under circularly polarized light, accompanied by helical edge modes to chiral ones. The propagation direction of edge-mode current in QAH nanoribbons can be switched by left-/right-circularly polarized (LCP/RCP) light, and such a current-switching effect is then confirmed in heterojunction composed of QSH and QAH nanoribbons. Based on the all-optically controlled current-switching effect, we design a three-terminal current switcher, with one input terminal, two output ones, and central device irradiated by LCP/RCP light. Conductance and real-space local current distribution of the proposed nanosystem reveal that the input current can indeed be switched into specific output terminal by LCP/RCP light. The proposed current switcher changes the electron movement very quickly, and we believe that it would have potential applications in high-speed photoelectric nanodevices.

Current Filamentation and Switching Effect in Chalcogenide Glassy Semiconductors: A Review

A review on current filamentation and switching effect in chalcogenide glassy semiconductors (CGSs), which are promising materials for the development of phase change memory devices, is presented. First, a history of the research on CGSs and their properties is considered. Next, formation of a current filament in CGSs is discussed and the scale of heat release in the material as well as the geometric shape of the filament is analyzed. Finally, various hypotheses developed for the explanation of the switching effect in CGSs are reviewed. It is shown that the most relevant model of the switching effect in CGS is the model of multi-phonon tunneling ionization of the so-called ‘negative-U centers’. This model is based on the assumption that an avalanche-like increase in current at a certain point in time is associated with mass tunneling of electrons located on atoms, occuring due to thermal vibrations of atoms.

Identification of Ferroelectricity in a Capacitor With Ultra-Thin (1.5-nm) Hf0.5Zr0.5O2 Film

The characterization of ferroelectricity in ultra-thin ferroelectric (FE) films is highly challenging due to enlarged leakage current and resistive switching (RS) effect. In this study, we investigated the polarization switching properties of 1.5-nm thick Hf <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (HZO) films via direct hysteresis remnant polarization/voltage (P-V) loop measurement. To reduce the leakage current and eliminate the RS effect, positive-up-negative-down (PUND) measurement was implemented on back-to-back connected complementary cells. Rational hysteresis loops, with remnant polarization of approximately 2 μC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , were successfully obtained by directly measuring the polarization switching currents. In this study, we provide direct evidence of the stable ferroelectric property in 1.5-nm thick HZO films, and thereby show a potential prospect of ultimate scalability of HZO films.

Electrostatic carrier doping of charge-ordered YbFe2O4 thin films using ionic liquids

We report the modulation of electrical properties of charge-ordered YbFe2O4 films using electrostatic carrier doping. By utilizing the current switching effect under a high DC electric field as a probe, we detected the charge-ordered phase in the c-axis-oriented YbFe2O4 films grown by pulsed-laser deposition. A three-terminal electric double-layer device with a thin channel of YbFe2O4 and an ionic liquid (IL) gate dielectric showed reversible modulation of channel conductance under a positive gate voltage. Furthermore, we demonstrated that conductance modulation could be enhanced by customizing the molecular structure of the IL.

Current Rectification, Resistive Switching, and Stable NDR Effect in BaTiO3/CeO2 Heterostructure Devices

AbstractElectronic devices with simultaneous manifestation of multiphysical properties are of great interest due to their possible application in multifunctional devices. In the present study, simultaneous execution of negative differential resistance (NDR) effect, current rectification (≈105), and resistive switching characteristics (≈103) are demonstrated in BaTiO3/CeO2 heterostructure. Although the negative differential effect has gained huge attention, its instability and poor reproducibility at room temperature are the main obstacles to its possible application in electronic devices. However, in this report, the NDR is observed even after hundreds of cycles in BaTiO3/CeO2 heterostructure at 300 K. For a detailed analysis of the NDR effect, AC conductance spectroscopy is performed, which reveals that the presence of NDR is associated with trapping/detrapping of charge carriers at interface states formed at the BaTiO3/CeO2 interface. In addition, the resistive switching and rectification effect are demonstrated due to a barrier at the BaTiO3/CeO2 interface, which can be strongly modulated by thickness (20, 50, and 80 nm) based ferroelectric polarization of BaTiO3. However, the results show that the remarkable performance of these devices makes them a potential candidate for application in multifunctional devices.

Influence of gas pressure on electron beam emission current of pulsed cathodic-arc-based forevacuum plasma electron source

We describe our experimental investigation of the effect of background gas pressure on the emission parameters of a pulsed cathodic-arc-based forevacuum-pressure plasma-cathode electron source. We find that increased gas pressure over the range 4–16 Pa significantly reduces the beam current rise-time and significantly increases the emission current amplitude. For example, at a discharge current of 20 A, increasing the working gas pressure from 4 Pa to 16 Pa increases the emission current from 8 A to 18 A and shortens the beam rise-time from 50 μs to 20 μs. This influence of gas pressure on the electron beam parameters can be explained by the effect of arc discharge current switching from the anode to emission. In our case, the current switching effect is caused by increased working gas pressure. In the forevacuum pressure range, the increase of the electron emission current with the growth of gas pressure is due to a rise in the emission plasma potential which is caused by ion back-streaming from the plasma formed in the electron beam transport region. A model describing the influence of gas pressure on the electron emission from the plasma is presented.

Resistive Switching and the Local Electric Field in Bi0.85-xPr0.15RExFe0.97Mn0.03O3/CuFe2O4 (RE = Sr, Dy) Bilayered Thin Films.

Bilayer Bi0.85-xPr0.15RExFe0.97Mn0.03O3/CuFe2O4 (BPRExFMO/CuFO, RE = Sr, Dy) thin films were prepared on FTO/glass substrates by the chemical solution deposition method. The structure transition does not appear after ion doping, which is confirmed by XRD and its refined results. The samples remain in the trigonal R3c:H structure in the BFO phase and in the tetragonal I41/amd structure in the CuFO phase. The asymmetric character of leakage current density curves and resistive switching effects have been explored. And the ion substitution impacts on the resistive switching effects may be due to the existence of local fields. Under the applied electric field, carries are accumulated and arranged directionally at the interface between the BFO and CuFO layers to form the local electric field. Such local field is affected by ion dopants, and the field compensates or weakens the applied electrical field. The reinforced or weakened resistive behavior is dependent on the direction of the local field and the injection of electrons. The polarization switching currents of the BPFMO/CuFO, BPSFMO/CuFO, and BPDFMO/CuFO samples, whose distribution fields are proportional to the local electrical fields, are 0.0070, 0.0049, and 0.0074 A under the positive applied field, respectively. And the remanent polarization is increased to 74.4, 73.5, and 84.3 μC/cm2 of the doped samples, respectively.

Current-induced forces: a new mechanism to induce negative differential resistance and current-switching effect in molecular junctions

Current-induced forces can excite molecules, polymers and other low-dimensional materials, which in turn leads to an effective gate voltage through Holstein interaction. Here, by taking a short asymmetric DNA junction as an example, and using the Langevin approach, we find that when suppression of charge transport by the effective gate voltage surpasses the current increase from an elevated voltage bias, the current-voltage (I–V) curves display strong negative differential resistance (NDR) and perfect current-switching characteristics. The asymmetric DNA chain differs in mechanical stability under inverse voltages and the I–V curve is asymmetric about inverse biases, which can be used to understand recent transport experiments on DNA chains, and meanwhile provides a new strategy to realize NDR in molecular junctions and other low-dimensional quantum systems.

All-electric-controlled spin current switching in single-molecule magnet-tunnel junctions

A single-molecule magnet (SMM) coupled to two normal metallic electrodes can both switch spin-up and spin-down electronic currents within two different windows of SMM gate voltage. Such spin current switching in the SMM tunnel junction arises from spin-selected single electron resonant tunneling via the lowest unoccupied molecular orbit of the SMM. Since it is not magnetically controlled but all-electrically controlled, the proposed spin current switching effect may have potential applications in future spintronics.

Pseudospin polarized quantum transport in monolayer graphene

Monolayer graphene with an energy gap presents a pseudospin symmetry-broken ferromagnet with a perpendicular pseudomagnetization whose direction is switched by altering the type of doping between $n$ and $p$. We demonstrate an electrical current switching effect in the pseudospin version of a spin valve in which two pseudoferromagnetic regions are contacted through a normal graphene region. The proposed structure exhibits a pseudomagnetoresistance, defined as the relative difference of resistances of parallel and antiparallel alignments of the pseudomagnetizations, which can be tuned to unity. This perfect pseudomagnetic switching is found to show a strong robustness with respect to increasing the contact length, the effect of which we explain in terms of an unusually long-range penetration of an equilibrium pseudospin polarization into the normal region by proximity to a pseudoferromagnet. Our results reveal the potential of gapped graphene for realization of pseudospin-based nanoelectronics.

Non-linear current–voltage characteristics of (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3 single crystals: Possible manifestation of the internal heating of chargecarriers

Temperature evolution of the current–voltage characteristics (CVCs) of a single-crystal lanthanum manganite (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3 is investigated in a wide (up to 1 А) range of instrumental currents. Effects of a transport current and an applied electric field on the resistance of the material are studied in view of possible implementation of the charge ordering break in dielectric regions occurring due to phase separation in manganites. A negative differential resistance portion observed in the CVCs suggests the presence of a current switching effect. Below the temperature of the metal–dielectric transition in (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3, the hysteresis is observed in the CVC. The detailed analysis of the internal sample heating on the basis of experimental data on thermal conductivity showed, however, that these CVC features can be explained within the concept of non-equilibrium heating of electron gas.

Electronic memory effect in a crystalline silicon/polyether heterostructure

AbstractOrganic/inorganic heterojunctions have been fabricated by spin‐coating of an oxadiazole based polyether on top of either n‐type or p‐type crystalline silicon substrates. The prepared heterodiodes showed good rectification. During current‐voltage measurements sharp current switching effects have been observed in the reverse bias characteristics for both types of heterodiodes. In particular a very stable hysteresis in the reverse characteristics of the polyether/n‐type crystalline silicon has been measured at applied voltages below 1V. The application of this heterodiode as electrical memory with an on/off‐ratio of about 2 orders of magnitude has been demonstrated (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Proposal for a correlation induced spin-current polarizer

We propose a spin polarizer device composed of a quantum dot connected to the spin-polarized leads. The spin control of the current flowing through the device is entirely due to the Coulomb interactions present inside the dot. We show that the initial polarization present in the source lead can be reverted or suppressed just by manipulating the gate voltage acting on the dot; the presence of the external magnetic field is not required. The influence of the temperature and finite bias on the efficiency of the current spin switching effect is also discussed.

Dielectric breakdown and current switching effect in the incommensurate layered compound(LaS)1.196VS2

A current switching effect of several orders of magnitude was observed in the incommensurate misfit layered compound ${(\mathrm{La}\mathrm{S})}_{1.196}\mathrm{V}{\mathrm{S}}_{2}$. This effect involves correlated vanadium ${t}_{2g}$ states in a hexagonal $[\mathrm{V}{\mathrm{S}}_{2}]$ layer. Application of moderate electric fields $(\ensuremath{\sim}50\phantom{\rule{0.3em}{0ex}}\mathrm{V}∕\mathrm{cm})$ induces a dielectric breakdown and restores a metallic state. The large pretransitional nonlinearities are consistent with a Poole-Frenkel mechanism which highlights the role of Coulomb interactions. This behavior and the strong modulation of the vanadium atom positions, revealed by single crystal x-ray structure determination, are in favor of a heterogeneous charge distribution. With respect to recent theoretical works, we suggest that the current switching effect observed in ${(\mathrm{La}\mathrm{S})}_{1.196}\mathrm{V}{\mathrm{S}}_{2}$ is related to the breakdown of a remaining Mott insulator state.

Reproducible switching in normal metal–manganite single crystal point contacts with memory effect

The current–voltage characteristics (IVC) and transport properties of point contacts in normal metal–manganite heterojunctions have been investigated on the base of La 1− x Sr x MnO 3, La 1− x Ca x MnO 3, La 1− x Ba x MnO 3 ( x=0.15–0.3) single crystals. At considerable current levels the IVC of point contacts show reproducible switching with memory effect. Negative or positive voltage switch the heterocontact resistance between high- and low-resistive states. It has been assumed that the observed current switching effects are due to phase separation of manganites under the electric current.

Current switching effects induced by electric and magnetic fields in Sr-substitutedPr0.7Ca0.3MnO3films

Measurements of electric- and magnetic-field-induced changes in electrical conduction indicate the coexistence of charge-ordered and ferromagnetically ordered regions in the Sr-substituted ${\mathrm{Pr}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$ epitaxial films. Percolative, metal-like channels open up in this topologically inhomogeneous medium on the application of these fields, and a technologically promising orders-of-magnitude drop in resistance ensues. Measurements of current-voltage characteristics and the temperature dependence of resistivity show hysteretic and history effects, which are intimately linked to the relative stability of the two phases.

A novel high current density switching effect in electrically conductive polymer composite materials

The electrical switching properties of electrically conductive polymer composites are studied at high current densities. It is shown that the switching properties at high current densities are substantially different from those at low current densities which depend on a positive temperature coefficient of resistance effect. Experiments are described that show that this type of switching appears to be a general feature in conductor-filled polymer composite materials and a qualitative model for the switching phenomenon is proposed. These results suggest that conductor-filled polymer composite materials can provide a new nonmechanical way of rapidly limiting high power short-circuit currents. This should have broad applications in the circuit protection industry.

Current fluctuations and switching effects in hydrogenated amorphous silicon/molybdenum multilayer thin films

Abstract Current-voltage characteristics and the temperature-dependent conductivity have been investigated for multilayer samples consisting of nanometre-size Mo clusters arranged in planes, which are separated by hydrogenated amorphous Si sublayers 80 nm thick. The samples show unique electronic properties which are reported for the first time. A typical electric field of 80 Vcm−1 applied to the samples with a coplanar electrode configuration results in a switching from a semiconducting to a metallic state with typical conductivities at room temperature of 10−6 and 1Ω−1 cm−1, respectively. The switching effect, which is reversible by thermal annealing at 450 K, is accompanied by chaotic current fluctuations with a ratio of maximum to minimum current of typically a factor of three and in some cases up to three orders of magnitude. The temperature dependence of the conductivity in. the metallic state is described by σ = σ0exp(-T 0/T)½ with typically σ0 = 3 Ω−1 cm−1 and T 0 = 240 K.

Negative-resistance effect in rubidium tetracyanoquinodimethane (Rb-TCNQ).

Nonlinear-conductivity phenomena, including negative-resistance and current-switching effects, have been observed in the radical-anion salt of rubidium tetracyanoquinodimethane (Rb-TCNQ) known as a spin-Peierls system. From the current and temperature dependences of infrared ${\mathit{a}}_{\mathit{g}}$ CN-stretching-vibration spectra, it is concluded that the observed nonlinear properties are not due to the Joule-heating effect but are attributable to the dynamics of soliton-type defects in the bond-ordered (dimerized) stacks of TCNQ molecules. The possible soliton-mediated transport mechanism in Rb-TCNQ is discussed, in parallel with previous discussions on similar nonlinear transport properties in mixed-stack organic charge-transfer crystals.