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Three-dimensional vertical resistive-switching random access memory (V-RRAM) is the most anticipated candidate for fulfilling the strict requirements of the disruptive storage-class memory technology, including low bit cost, fast access time, low-power nonvolatile storage, and excellent endurance. However, an essential self-selecting resistive-switching cell that satisfies these requirements has yet to be developed. In this study, we developed a TaOx/TiO2 double-layer V-RRAM containing numerous highly desired features, including: (1) a self-rectifying ratio of up to 103 with a sub-μA operating current, (2) little cycle-to-cycle and layer-to-layer variation, (3) a steep vertical sidewall profile for high-density integration, (4) forming-free and self-compliance characteristics for a simple peripheral circuit design, and (5) an extrapolated endurance of over 1015 cycles at 100 °C. Furthermore, the switching and self-rectifying mechanisms were successfully modeled using oxygen ion migration and homogeneous barrier modulation. We also suggest the new possibility of monolithically integrating working and storage memory by exploiting a unique tradeoff between retention time and endurance. [ABSTRACT FROM AUTHOR]

In this work, the resistive switching behaviors of ferroelectrictric BaTiO3/La0.67Sr0.33MnO3 heterostructures deposited by pulsed laser deposition are investigated. The BaTiO3 films show both well-established P—E hysteresis loops, and asymmetric reversible diode-like resistive switching behaviors, involving no forming process. It is found that both the ON/OFF ratio and the stability of resistive switching are substantially dependent on operation voltage (Vmax). At a Vmax of 15 V, a large ON/OFF resistance ratio above 1000 is obtained at a Vmax of 15 V, which is able to maintain stability up to 70-switching cycles. The above resistive switching behaviors can be understood by modulating interface Schottky barriers as demonstrated by I—V curve fitting. [ABSTRACT FROM AUTHOR]

A radio frequency micro-electro-mechanical system (RF-MEMS) phase shifter based on switchable delay line concept with maximum desirable phase shift and good reliability is presented in this paper. The phase shifter is based on the switchable reference and delay line configurations with inline metal contact series switches that employs MEMS systems based on electrostatic actuation and implemented using coplanar waveguide (CPW) configuration. Electromechanical behaviour of the MEMS switch has been extensively investigated using commercially available simulation tools and validated using system level simulation. A detailed design and performance analysis of the phase shifter has been carried out as a function of various structural parameters with reference to the gold-based surface micromachining process on alumina substrate. The mechanical, electrical, transient, intermodulation distortion (IMD) and loss performance of an MEMS switch have been experimentally investigated. The individual primary phase-bits (11.25°/22.5°/45°/90°/180°) that are fundamental building blocks of a complete 5-bit phase shifter have been designed, fabricated and experimentally characterized. Furthermore, two different 5-bit switched-line phase shifters, that lead to 25% size reduction and result in marked improvement in the reliability of the complete 5-bit phase shifter with 30 V actuation voltage, have been developed. The performance comparison between two different CPW-based switched-line phase shifters have been extensively investigated and validated. The complete 5-bit phase shifter demonstrates an average insertion loss of 5.4 dB with a return loss of better than 14 dB at 17.25 GHz. The maximum phase error of 1.3° has been obtained at 17.25 GHz from these 5-bit phase shifters. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations based on the shell model potential for PbTiO3 were carried out to investigate the effect of the cell dimension, temperature and kink structure on the domain switching of 90° ferroelectric domain walls. It was found that the critical shear stress is linearly dependent on the inverse of the cell dimension, which is identified as a manifestation of the artificial electric field caused by the periodic boundary conditions. Ab initio density functional theory calculations were carried out to confirm this effect and a similar result was observed. Finite temperature simulations based on a molecular dynamics approach have shown a reduction in the critical shear stress and maximum shear strain due to the increase in thermal agitation. At a finite temperature, the domain wall structure is characterized by perovskite units cells with a preferential polarization along the (0 1 1)-direction. Simulations of kink structures revealed a long-range strain field caused by local disorder of the crystal lattice in the area surrounding the kink. As a direct consequence, careful size considerations on the separation distances between kinks have to be made prior to performing shear strain simulations. It was found that kink structures significantly facilitate the motion of 90° domain walls in PbTiO3. [ABSTRACT FROM AUTHOR]

This study obtained theoretical and experimental periodic and quasiperiodic pulse trains in a passively Q-switched Nd:YVO4 laser with pump modulation. Phase locking generated period-one, period-two and period-three pulse trains when the ratio between the modulation frequency and the repetition frequency without modulation was approximately 1,1/2 and 2/3, respectively. Outside these regions, quasiperiodic evolution dominated the pulse train dynamics. [ABSTRACT FROM AUTHOR]

In this paper, an ultra-low voltage microelectromechanical system (MEMS) switch is proposed, modeled and demonstrated. Through the introduction of torsional hinges, stiction-recovery actuation was possible, and thus irreversible stiction could be overcome. Owing to this see-saw-like actuation, the switch could be freely designed to have low stiffness resulting in an ultra-low actuation voltage. The proposed switch shows an actuation voltage of around 3 V, which is especially low compared with typical values of several tens of volts in conventional microelectromechanical switches. Variation of the actuation voltage stayed under 12% during 106 cycles. Switching performance was degraded by an increase of contact resistance rather than in-use stiction. Using the proposed switches, low-voltage mechanical logic gates were also proposed and successfully demonstrated, operating at VDD of 3 V. [ABSTRACT FROM AUTHOR]

With the progress of the semiconductor industry, the resistive random-access memory (RAM) has drawn increasing attention. The discovery of the memristor has brought much attention to this study. Research has focused on the resistive switching characteristics of different materials and the analysis of resistive switching mechanisms. We discuss the resistive switching mechanisms of different materials in this paper and analyze the differences of those mechanisms from the view point of circuitry to establish their respective circuit models. Finally, simulations are presented. We give the prospect of using different materials in resistive RAM on account of their resistive switching mechanisms, which are applied to explain their resistive switchings. [ABSTRACT FROM AUTHOR]

We demonstrate the polarization of resistive switching for a Cu/VOχ/Cu memory cell. The switching behaviors of Cu/VOχ/Cu cell are tested by using a semiconductor device analyzer (Agilent B1500A), and the relative micro-analysis of I-V characteristics of VOχ/Cu is characterized by using a conductive atomic force microscope (CAFM). The I-V test results indicate that both the forming and the reversible resistive switching between low resistance state (LRS) and high resistance state (HRS) can be observed under either positive or negative sweep. The CAFM images for LRS and HRS directly exhibit evidence for the formation and rupture of filaments based on positive or negative voltage. The Cu/VOχ/Cu sandwiched structure exhibits reversible resistive switching behavior and shows potential applications in the next generation of nonvolatile memory. [ABSTRACT FROM AUTHOR]

A new approach of generating transient chaos from two-dimensional (2D) continuous autonomous systems within finite time is presented. Based on an absolute-value switching law, the phenomenon of transient chaos takes place by switching between three 2D systems. Basic dynamic behavior of the systems is investigated. Numerical examples illustrate the validity of the results. [ABSTRACT FROM AUTHOR]

We report local and non-local measurements in pin-hole dominated mesoscopic multigraphene spin-valves. Local spin-valve measurements show spurious switching behavior in resistance during magnetic field sweeping similar to the signal observed due to spin injection into multigraphene. The switching behavior has been explained in terms of a local Hall effect due to a thickness irregularity of the tunnel barrier. The local Hall effect appears due to a large local magnetostatic field produced near the roughness in the AlOx tunnel barrier. In our samples the resistance change due to the local Hall effect remains negligibly small above 75 K. A strong local Hall effect might hinder spin injection into multigraphene, resulting in no spin signal in non-local measurements. [ABSTRACT FROM AUTHOR]

Nanoscale switching dynamics in spin-coated ferroelectric copolymer films of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE 75/25) has been investigated via high-resolution real-space imaging of electrically induced domain structure evolution using resonance-enhanced piezoresponse force microscopy. It has been shown that in strongly imprinted films application of switching pulses of opposite polarity results in qualitatively different domain switching dynamics. A distinct feature of domain dynamics is roughening of the domains walls during switching to the preferred polarization state as opposed to smooth domain boundaries during switching to the opposite direction. The observed switching behavior is explained by a combined effect of the spatially uniform built-in electric field and local disorder potential. Application of the external potential changes the balance between the two and creates conditions under which domain growth is dominated either by the average built-in electric field or local random-bond disorder potential. [ABSTRACT FROM AUTHOR]

We theoretically investigate a switchable spin Hall effect of light (SHEL) in reflection for three specific dispersion relations at an air-anisotropic metamaterial interface. The displacements of horizontal and vertical polarization components vary with the incident angle at different dispersion relations. The transverse displacements can be obtained with the relevant metamaterial whose refractive index can be arbitrarily tailed. The results of the SHEL in the metamaterial provide a new way for manipulating the transverse displacements of a specific polarization component. [ABSTRACT FROM AUTHOR]

We consider multi-agent systems with time-varying delays and switching interconnection topologies. By constructing a suitable Lyapunov-Krasovskii functional and using the reciprocally convex approach, new delay-dependent consensus criteria for the systems are established in terms of linear matrix inequalities (LMIs), which can be easily solved by using various effective optimization algorithms. Two numerical examples are given to illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

The resistive switching properties in amorphous Pr0.67Sr0.33MnO³ films deposited by pulsed laser deposition are investigated. Reproducible and bipolar counter-8-shape and 8-shape switching behaviours of Au/Pr0.67Sr0.33MnO³/F:SnO2 junctions are obtained at room temperature. Dramatically, the coexistence of two switching polarities could be reversibly adjusted by an applied voltage range. The results allocated those two switching types to areas of different defect densities beneath the same electrode. The migration of oxygen vacancies and the trapping effect of electrons under an applied electric field play an important role. An interface-effect-related resistance switching is proposed in an amorphous Pr0.67Sr0.33MnO³-based memory cell. [ABSTRACT FROM AUTHOR]

We investigate the coherent manipulation of quantum tunnelling for a single atom held in a driven planar four-well potential with diagonal coupling. In the high-frequency regime, the non-Floquet states with slowly varying populations are constructed by the linear superposition of Floquet solutions. Based on the analytical results, the effect of the selective coherent destruction of tunnelling is exhibited and the two-pathway switching scheme is suggested by adjusting the driving parameters. [ABSTRACT FROM AUTHOR]

This paper introduces an average contraction analysis for nonlinear switched systems and applies it to investigating the synchronization of complex networks of coupled systems with switching topology. For a general nonlinear system with a time-dependent switching law, a basic convergence result is presented according to average contraction analysis, and a special case where trajectories of a distributed switched system converge to a linear subspace is then investigated. Synchronization is viewed as the special case with all trajectories approaching the synchronization manifold, and is thus studied for complex networks of coupled oscillators with switching topology. It is shown that the synchronization of a complex switched network can be evaluated by the dynamics of an isolated node, the coupling strength and the time average of the smallest eigenvalue associated with the Laplacians of switching topology and the coupling fashion. Finally, numerical simulations illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

The ruggedness of a superjunction metal-oxide semiconductor field-effect transistor (MOSFET) under unclamped inductive switching conditions is improved by optimizing the avalanche current path. Inserting a P-island with relatively high doping concentration into the P-column, the avalanche breakdown point is localized. In addition, a trench type P+ contact is designed to shorten the current path. As a consequence, the avalanche current path is located away from the N+ source/P-body junction and the activation of the parasitic transistor can be effectively avoided. To verify the proposed structural mechanism, a two-dimensional (2D) numerical simulation is performed to describe its static and on-state avalanche behaviours, and a method of mixed-mode device and circuit simulation is used to predict its performances under realistic unclamped inductive switching. Simulation shows that the proposed structure can endure a remarkably higher avalanche energy compared with a conventional superjunction MOSFET. [ABSTRACT FROM AUTHOR]

The I-V characteristics of In2O3:SnO2/TiO2/In2O3:SnO2 junctions with different interfacial barriers are investigated by comparing experiments. A two-step resistance switching process is found for samples with two interfacial barriers produced by specific thermal treatment on the interfaces. The nonsynchronous occurrence of conducting filament formation through the oxide bulk and the reduction in the interfacial barrier due to the migration of oxygen vacancies under the electric field is supposed to explain the two-step resistive switching process. The unique switching properties of the device, based on interfacial barrier engineering, could be exploited for novel applications in nonvolatile memory devices. [ABSTRACT FROM AUTHOR]

La0.67Ca0.33MnO3 thin films are fabricated on fluorine-doped tin oxide conducting glass substrates by a pulsed laser deposition technique with SrTiO3 used as a buffer layer. The current-voltage characteristics of the heterojunctions exhibit an asymmetric and resistance switching behaviour. A homogeneous interface-type conduction mechanism is also reported using impedance spectroscopy. The spatial homogeneity of the charge carrier distribution leads to fieldinduced potential-barrier change at the Au-La0.67Ca0.33MnO3 interface and a concomitant resistance switching effect. The ratio of the high resistance state to the low resistance state is found to be as high as 1.3 × 104% by simulating the AC electric field. This colossal resistance switching effect will greatly improve the signal-to-noise ratio in nonvolatile memory applications. [ABSTRACT FROM AUTHOR]

Scanning transmission x-ray microscopy (STXM) and magnetoresistance (MR) measurements are used to investigate the magnetic behavior of a nanoconstriction joining two micrometric electrodes (a pad and a wire). The reversal of the magnetization under variable external static magnetic fields is imaged. By means of a detailed analysis of the STXM images at the nanocontact area, the MR is calculated, based on diffusive anisotropic-MR. This MR agrees well with that obtained from electrical transport measurements, allowing a direct correlation between the MR signal and the magnetic reversal of the system. The magnetization behavior depends on the sample thickness and constriction dimensions. In 40 nm-thick samples, with 20 × 175 nm2 contact areas, the magnetization at the two sides of the constriction forms a net angle of 90°, with a progressive evolution of the magnetization structure between the electrodes during switching. The MR in those cases has a more peaked shape than with 20 nm-thick electrodes and 10 × 80 nm2 contact areas, where the magnetization forms 180 between them, with a wide domain wall pinned at the constriction. As a consequence of this configuration, a plateau in the MR is observed for about 20 Oe. [ABSTRACT FROM AUTHOR]

We fabricated an array-type organic nonvolatile memory device with multilayer graphene (MLG) film embedded in polyimide (PI) layers. The memory devices showed a high ON=OFF ratio (over 106) and a long retention time (over 104 s). The switching of the Al/PI/MLG/PI/Al memory devices was due to the presence of the MLG film inserted into the PI layers. The double-log current-voltage characteristics could be explained by the space-charge-limited current conduction based on a charge-trap model. A conductive atomic force microscopy found that the conduction paths in the low-resistance ON state were distributed in a highly localized area, which was associated with a carbon-rich filamentary switching mechanism. [ABSTRACT FROM AUTHOR]

Wavepackets representing relativistic quantum particles injected into a halfspace, from a source that is switched on at a definite time, are represented by superpositions of plane waves that must include negative frequencies. Propagation is causal: it is a consequence of analyticity that at time t no part of the wave has travelled farther than ct, corresponding to the front of the signal. Nevertheless, interference fringes behind the front travel superluminally. For Klein-Gordon and Diracwavepackets, the spatially integrated density increases because current is injected at the boundary. Even in the simplest causal model, understanding the shape of the wave after long times is an instructive exercise in the asymptotics of integrals, illustrating several techniques at a level suitable for graduate students; different spatial features involve contributions from a pole and from two saddle points, the uniform asymptotics for the pole close to a saddle, and the coalescence of two saddles into the Sommerfeld precursor immediately behind the front. [ABSTRACT FROM AUTHOR]

We present a laboratory experiment for advanced undergraduate or graduate laser-related classes to study the performance of a neodymium laser. In the experiment, the student has to build the neodymium laser using an open cavity. After that, the cavity losses are modulated with an optical chopper located inside, so the Q-switching regime is achieved. Also a nonlinear crystal can be inserted in the cavity in order to have second harmonic generation. Finally, the relation between the transverse modes and the temporal emission in the Q-switching regime can be observed. [ABSTRACT FROM AUTHOR]

A one-dimensional rule-based model for flocking, which combines velocity alignment and long-range centering interactions, is presented and studied. The induced cohesion in the collective motion of the self-propelled agents leads to unique group behavior that contrasts with previous studies. Our results show that the largest cluster of particles, in the condensed states, develops a mean velocity slower than the preferred one in the absence of noise. For strong noise, the system also develops a non-vanishing mean velocity, alternating its direction of motion stochastically. This allows us to address the directional switching phenomenon. The effects of different sources of stochasticity on the system are also discussed. [ABSTRACT FROM AUTHOR]

The insulating state of magnetite (Fe3O4) can be disrupted by a sufficiently large dc electric field. Pulsed measurements are used to examine the kinetics of this transition. Histograms of the switching voltage show a transition width that broadens as the temperature is decreased, consistent with trends seen in other systems involving 'unpinning' in the presence of disorder. The switching distributions are also modified by an external magnetic field on a scale comparable to that required to reorient the magnetization. [ABSTRACT FROM AUTHOR]

This paper introduces the mid-span spectral inversion by four-wave mixing in a commercially available semiconductor optical amplifier (SOA) with a length of about 1.5 mm to optical label switching network based on combined frequency shift keying (FSK)-intensiy modulation (IM)/optical label-packet modulation to overcome the dispersion limitation of fiber. The 155 Mb/s-10 Gb/s combined FSK/IM signal is experimentally transmitted over a 100 km standard single mode fiber. 10[?]10 and 10[?]9 BER (bit error ratio), or even better, is achieved for the FSK label and IM packet, respectively. The -19 dB power conversion efficiency is obtained for -1 nm wavelength detuning. [ABSTRACT FROM AUTHOR]

Nonlinear consensus protocols for dynamic directed networks of multi-agent systems with fixed and switching topologies are investigated separately in this paper. Based on the centre manifold reduction technique, nonlinear consensus protocols are presented. We prove that a group of agents can reach a b-consensus, the value of which is the group decision value varying from the minimum and the maximum values of the initial states of the agents. Moreover, we derive the conditions to guarantee that all the agents reach a b-consensus on a desired group decision value. Finally, a simulation study concerning the vertical alignment manoeuvere of a team of unmanned air vehicles is performed. Simulation results show that the nonlinear consensus protocols proposed are more effective than the linear protocols for the formation control of the agents and they are an improvement over existing protocols. [ABSTRACT FROM AUTHOR]

A comprehensive theoretical study of the optical properties and switching competence of double-shell photonic crystals (DSPC) and double-inverse- opal photonic crystals (DIOPC) is presented. Our analysis reveals that a DIOPC structure with a silicon (Si) background exhibits a complete photonic bandgap (PBG), which can be completely switched on and off by moving the core spheres inside the air pores of the inverse opal. We show that the size of this switchable PBG assumes a value of 3.78% upon judicious structural optimization, while its existence is almost independent of the radii of the interconnecting cylinders, whose sizes are difficult to control during the fabrication process. The Si-based DIOPC may thus offer a novel and practical route to complete PBG switching and optical functionality. [ABSTRACT FROM AUTHOR]

We have made a gain-switched all-solid-state quasi-continuous-wave (QCW) tunable Ti:sapphire laser system, which is pumped by a 532 nm intracavity frequency-doubled Nd:YAG laser. Based on the theory of gain-switching and the study on the influencing factors of the output pulse width, an effective method for obtaining high power and narrow pulse width output is proposed. Through deliberately designing the pump source and the resonator of the Ti:sapphire laser, when the repetition rate is 6 kHz and the length of the cavity is 220 mm, at an incident pump power of 22 W, the tunable Ti:sapphire laser from 700 to 950 nm can be achieved. It has a maximum average output power of 5.6 W at 800 nm and the pulse width of 13.2 ns, giving an optical conversion efficiency of 25.5% from the 532 nm pump laser to the Ti:sapphire laser. [ABSTRACT FROM AUTHOR]

Magnetic fields generated by current lines are the standard way of switching between resistance (R) states in magnetic random access memories. A less common but technologically more interesting alternative to achieve R-switching is to use an electrical current crossing the tunnel barrier. Such current induced magnetization switching (CIMS) or current induced switching (CIS) effects were recently observed in thin magnetic tunnel junctions, and attributed to spin transfer (CIMS) or electromigration of atoms into the insulator (CIS). In this work, electromigration-driven resistance changes (resistive switching) are superimposed with thermally induced pinned layer reversal (magnetic switching), producing a reproducible, three-state memory device. The tunnel junctions under study show a tunnel magnetoresistance of 14% with a RA product of 50 O µm2. The reversible electromigration-driven resistance changes amount to 7-8% of the full resistance change and more than 104 R-switching events can be current induced without significant damage to the tunnel junction. Typical critical current densities are of the order of 2 × 106 A cm[?]2. [ABSTRACT FROM AUTHOR]

In this review, the potential of mode-locked lasers based on advanced quantum-dot (QD) active media to generate short optical pulses is analysed. A comprehensive review of experimental and theoretical work on related aspects is provided, including monolithic-cavity mode-locked QD lasers and external-cavity mode-locked QD lasers, as well as mode-locked solid-state and fibre lasers based on QD semiconductor saturable absorber mirrors. Performance comparisons are made for state-of-the-art experiments. Various methods for improving important characteristics of mode-locked pulses such as pulse duration, repetition rate, pulse power, and timing jitter through optimization of device design parameters or mode-locking methods are addressed. In addition, gain switching and self-pulsation of QD lasers are also briefly reviewed, concluding with the summary and prospects. [ABSTRACT FROM AUTHOR]

A memory device has been fabricated using an AgI film sandwiched between a Pt film and an Ag film with the lateral size of the device scaled down to 300?nm. The AgI film was made by the iodination of the Ag film at room temperature and under ambient pressure. The switching between high- and low-resistance states can be realized by applying voltages of different polarities. The switching can be performed under the application of voltage pulses with a 100?Hz frequency for ?103times. The switching times are in the order of microseconds and the retention time is about a week. The switching effects are explained as the electrochemical growth and dissolution of Ag in AgI. [ABSTRACT FROM AUTHOR]

We propose a Markov model with an ergodic two-component switching mechanism that dynamically generates anomalous diffusion. The first component plays the role of a hidden parameter. The second one is the switching component generating the superdiffusion of a random walker and is itself non-Markovian. The model is studied numerically using the Monte Carlo technique. [ABSTRACT FROM AUTHOR]

A single-transistor CMOS active pixel image sensor (1T CMOS APS) architecture is proposed. By switching the photosensing pinned diode, resetting and selecting can be achieved by diode pull-up and capacitive coupling pull-down of the source follower. Thus, the reset and selected transistors can be removed. In addition, the reset and selected signal lines can be shared to reduce the metal signal line, leading to a very high fill factor. The pixel design and operation principles are discussed in detail. The functionality of the proposed 1T CMOS APS architecture has been experimentally verified using a fabricated chip in a standard 0.35 m CMOS AMIS technology. [ABSTRACT FROM AUTHOR]

We present a new theoretical design for diode lasers which should be capable of generating sub-100-ps pulses with pulse energies of more than 10 nJ per 100-μm-contact width by active Q-switching. We show that the carrier-induced reduction of the refractive index in the active layer, i.e. the vertical anti-index guiding effect, results in a dependence of the optical confinement factor on the carrier density which can be exploited for a further enhancement of the pulse energy and a reduction of the pulse length. [ABSTRACT FROM AUTHOR]

A novel work on several aspects of current conduction mechanism for resistive switching (RS) of a reactive electrode-based memristor (Al/ZnO/Al) against generally used inert electrode–based devices has been illustrated. Compliance current (Icc), i.e. maximum current through device and stop voltage (Vstop), i.e. maximum Vstop upon device, has been used as bias characteristics to evaluate the effect upon conduction behavior. Effect of change in Icc for constant Vstop and vice-versa upon high resistance state (HRS) and low resistance state (LRS) has been evaluated in terms of change in bulk defects, i.e. oxygen vacancy and interface inhomogenity, i.e. AlOx formation/dissolution. The device shows unipolar resistive switching (URS) at lower Icc (< = 0.1 mA) and transits irreversibly into bipolar resistive switching (BRS) at higher Icc (> = 1 mA). The dominant conduction behavior of the device is found to be homogenous resistive switching (HoRS). The conduction in HRS and LRS is found to be space-charge limited current conduction. Conductive atomic force microscopy results of the thin film switching layer support the HoRS mechanism and also illustrate the role of interfacial oxide in attributing BRS behavior in the Al/ZnO/Al resistive switch. Studies can be utilized in future to further understand the RS conduction mechanism in reactive electrode–based RS and can be applied for multi-state memory applications. [ABSTRACT FROM AUTHOR]

In this report, we study factors that dominate the mode transformation of resistive switching (RS) in yttria based memristive devices. It is found that amorphous yttria films are more suitable for RS whereas highly crystalline films are counterproductive for RS. The transformation from unipolar to bipolar resistive switching mode is demonstrated in our devices via moving from a system of single Schottky barrier diode (SBD) to double SBD. The conduction mechanism behind these transformation mechanisms is found to be predominantly interfacial. We also report a forming-free Al/Y2O3/Al based memristor fabricated by the dual ion beam sputtering without any post-processing steps for the first time. It shows stable switching behavior for  >29 000 cycles with good retention (105 s) characteristics. [ABSTRACT FROM AUTHOR]

Switching of the direction of flagella rotations is the key control mechanism governing the chemotactic activity of E. coli and many other bacteria. Power-law distributions of switching times are most peculiar because their emergence cannot be deduced from simple thermodynamic arguments. Recently, it was suggested that by adding finite-time correlations into Gaussian fluctuations regulating the energy height of the barrier between the two rotation states, it is possible to generate switching statistics with an intermediate power-law asymptotics. By using a simple model of a regulatory pathway, we demonstrate that the required amount of correlated ‘noise’ can be produced by finite number fluctuations of reacting protein molecules, a condition common to the intracellular chemistry. The corresponding power-law exponent appears as a tunable characteristic controlled by parameters of the regulatory pathway network such as the equilibrium number of molecules, sensitivities, and the characteristic relaxation time. [ABSTRACT FROM AUTHOR]

We consider the quantum dynamics of a free nonrelativistic particle moving in a cavity and we analyze the effect of a rapid switching between two different boundary conditions. We show that this procedure induces, in the limit of infinitely frequent switchings, a new effective dynamics in the cavity related to a novel boundary condition. We obtain a dynamical composition law for boundary conditions which gives the emerging boundary condition in terms of the two initial ones. [ABSTRACT FROM AUTHOR]

This paper reports the reversible transition processes between the bipolar and complementary resistive switching (CRS) characteristics on the binary metal-oxide resistive memory devices of Pt/HfOx/TiN and Pt/TaOx/TiN by applying the appropriate bias voltages. More interestingly, by controlling the amplitude of the negative bias, the parasitic resistive switching effect exhibiting repeatable switching behavior is uncovered from the CRS behavior. The electrical observation of the parasitic resistive switching effect can be explained by the controlled size of the conductive filament. This work confirms the transformation and interrelationship among the bipolar, parasitic, and CRS effects, and thus provides new insight into the understanding of the physical mechanism of the binary metal-oxide resistive switching memory devices. [ABSTRACT FROM AUTHOR]

In this work, first principle calculations are employed to study the microstructure characteristics of the anatase TiO2 resistive switching material associated with the generation of oxygen vacancy (Vo) based nanofilaments during the switching process. The calculations indicate that both the magnéli phase Ti4O7 and Vo-defect phase of anatase TiO2 may be formed with the generation of oxygen vacancies during the forming and SET processes. Based on the calculations, a new physical insight is proposed to clarify the microstructure evolution characteristics of the anatase TiO2 resistive switching material and the correlation with resistive switching behaviors. During the forming or SET process, the anatase TiO2 is first excited to a transition state with the generation of oxygen vacancies, then fully relaxes to a stable Vo-defect state. This Vo-defect state may either recover to the original state with the recombination of the oxygen vacancies, which causes the reversible resistive switching behavior, or further transform to a much more stable state—the magnéli phase Ti4O7, through a phase transition process with the generation of many more oxygen vacancies. The phase transition from Vo- defective anatase phase to magnéli phase Ti4O7 causes the failure of the resistive switching due to the significantly reduced possibility of the reversible phase transition from the magnéli phase to the anatase phase, compared with the possibility of the recombination from the Vo-defective anatase. [ABSTRACT FROM AUTHOR]

Magnetically actuated swimming of microscopic objects has been attracting attention partly due to its promising applications in the bio-medical field and partly due to interesting physics of swimming in general. While colloidal particles that are free to move in fluid can be an attractive swimming system due it its simplicity and ability to assemble in situ, stability of their dynamics and the possibility of stable swimming behavior in periodically varying magnetic fields has not been considered. Dynamic behavior of two magnetically interacting colloidal particles subjected to rotating magnetic field of switching frequency is analyzed here and is shown to result in stable swimming without any stabilizing feedback. A new mechanism of swimming that relies only on rotations of the particles themselves and of the particle pair axis is found to dominate the swimming dynamics of the colloidal particle pair. Simulation results and analytical arguments demonstrate that this swimming strategy compares favorably to dragging the particles with an external magnetic force when colloidal particle sizes are reduced. [ABSTRACT FROM AUTHOR]

We propose and numerically demonstrate a compact terahertz wave switch which is composed of two graphene waveguides and three graphene ring resonators. Changing the bias voltage of the Fermi level in the center graphene ring, the resonant mode can be tuned when the plasmon waves in the waveguides and rings are coupled. We theoretically explain their mechanisms as being due to bias voltage change induced carrier density of graphene modification and the coupling coefficients of graphene plasmon effect after carrier density change, respectively. The mechanism of such a terahertz wave switch is further theoretically analyzed and numerically investigated with the aid of the finite element method. With an appropriate design, the proposed device offers the opportunity to ‘tune’ the terahertz wave ON–OFF with an ultra-fast, high extinction ratio and compact size. This structure has the potential applications in terahertz wave integrated circuits. [ABSTRACT FROM AUTHOR]

In this paper, the self-compliance bipolar resistive switching characteristic of an HfO2-based memory device with Ag/HfO2/Au structure for multilevel storage is investigated. By applying a positive voltage, the dual-step set processes corresponding to three stable resistance states are observed in the device. The multilevel switching characteristics can still be observed after 48 hours. In addition, the resistance values of all the three states show negligible degradation over 104 s, which may be useful for the applications in nonvolatile multilevel storage. [ABSTRACT FROM AUTHOR]

In this letter, the Ta/HfOx/BN/TiN resistive switching devices are fabricated and they exhibit low power consumption and high uniformity each. The reset current is reduced for the HfOx/BN bilayer device compared with that for the Ta/HfOx/TiN structure. Furthermore, the reset current decreases with increasing BN thickness. The HfOx layer is a dominating switching layer, while the low-permittivity and high-resistivity BN layer acts as a barrier of electrons injection into TiN electrode. The current conduction mechanism of low resistance state in the HfOx/BN bilayer device is space-charge-limited current (SCLC), while it is Ohmic conduction in the HfOx device. [ABSTRACT FROM AUTHOR]

A proposal of an electrically controlled spin transistor in a helical magnetic field is presented. In the proposed device, the transistor action is driven by the Landau–Zener transitions that lead to a backscattering of spin polarized electrons and switching the transistor into the high-resistance state (off state). The on/off state of the transistor can be controlled by the all-electric means using Rashba spin–orbit coupling that can be tuned by the voltages applied to the side electrodes. [ABSTRACT FROM AUTHOR]

Strain mediated magnetization switching of ferromagnetic/substrate/piezoelectric actuator heterostructures has become a hot issue due to the advantage of low-power consumption. In this work, Fe65Co35 thin films were deposited on a flexible polyamides (PI) substrate, which has quite low Young’s module (~4 GPa for PI as compared to ~180 GPa for Si) and benefits from complete transfer of the strain from the piezoelectric actuator to magnetic thin films. A complete 90° transition of the magnetic easy axis was realized in 50 nm thick FeCo films under the voltage of 70 V, while a less than 90° rotation angle of the magnetic easy axis direction was observed in other samples, which was ascribed to the distribution of the anisotropy field and/or the orthogonal misalignment between stress induced anisotropy and original uniaxial anisotropy. A model considering two uniaxial anisotropies with orthogonal arrangement was used to quantitatively understand the observed results and the linear-like voltage dependent anisotropy field, especially for 10 nm FeCo films, in which the switching mechanism along the easy axis direction can be explained by the domain wall depinning model. It indicates that the magnetic domain-wall movement velocity may be controlled by strain through tuning the energy barrier of the pinning in heterostructures. Moreover, voltage-driven 90° magnetization switching with low-power consumption was achieved in this work. [ABSTRACT FROM AUTHOR]

We consider diffusion in a potential well with a boundary that randomly switches between absorbing and reflecting and show how the switching boundary affects the classical escape theory. Using the theory of stochastic hybrid systems, we derive boundary value problems for the mean first passage time and splitting probability and find explicit solutions in terms of the spectral decomposition of the associated differential operator. Further, using a more probabilistic approach, we prove asymptotic formulae for these statistics in the small diffusion limit. In particular, we show that the statistical behavior depends critically on the gradient of the potential near the switching boundary and we derive corrections to Kramers’ reaction rate theory. [ABSTRACT FROM AUTHOR]

A three-terminal device based on electronic phase separated manganites is suggested to produce high performance resistive switching. Our Monte Carlo simulations reveal that the conductive filaments can be formed/annihilated by reshaping the ferromagnetic metal phase domains with two cross-oriented switching voltages. Besides, by controlling the high resistance state (HRS) to a stable state that just after the filament is ruptured, the resistive switching remains stable and reversible, while the switching voltage and the switching time can be greatly reduced. [ABSTRACT FROM AUTHOR]

The effects of Ni/ZrO2/TaN resistive switching memory devices without and with a 400 °C annealing process on switching properties are investigated. The devices exhibit unipolar resistive switching behaviors with low set and reset voltages because of a large amount of Ni diffusion with no reaction with ZrO2 after the annealing process, which is confirmed by ToF-SIMS and XPS analyses. A physical model based on a Ni filament is constructed to explain such phenomena. The device that undergoes the 400 °C annealing process exhibits an excellent endurance of more than 1.5  ×  104 cycles. The improvement can be attributed to the enhancement of oxygen ion migration along grain boundaries, which result in less oxygen ion consumption during the reset process. The device also performs good retention up to 105 s at 150 °C. Therefore, it has great potential for high-density nonvolatile memory applications. [ABSTRACT FROM AUTHOR]