Bistability Effect Research Articles

Electrical bistable devices using composites of zinc sulfide nanoparticles and poly-(N-vinylcarbazole)**Project supported by the National Natural Science Foundation of China (Grant No. 61377028), the Natural Science Funds for Distinguished Young Scholar, China (Grant No. 61125505), and the Fundamental Research Funds for the Central Universities, China (Grant No. 2014JBZ009).

N-dodecanethiol capped zinc sulfide (ZnS) nanocrystals were synthesized by the one-pot approach and blended with poly (N-vinylcarbazole) (PVK) to fabricate electrical bistable devices. The corresponding devices did exhibit electrical bistability and negative differential resistance (NDR) effects. A large ON/OFF current ratio of 104 at negative voltages was obtained by applying different amplitudes of sweeping voltage. The observed conductance switching and the negative differential resistance are attributed to the electric-field-induced charge transfer between the nanocrystals and the polymer, and the charge trapping/detrapping in the nanocrystals.

An organic–inorganic hybrid perovskite logic gate for better computing

An electrically bistable and non-volatile rewritable memory effect on a sandwich architecture, ITO/PEDOT:PSS/organic–inorganic hybrid perovskite/Cu, is shown.

Bandwidth widening in nonlinear electromagnetic vibrational generator by combined effect of bistability and stretching

This work reports the novel concept of frequency response widening of vibrational energy harvesters exploiting the combined effects of bistable and monostable nonlinearities in a single device. The bistability is introduced into the system by repulsive arrangement of magnets, while monostable nonlinear force through the stretching is incorporated by large deformation of two-end-fixed cantilevers. The simulation results show wider bandwidth in the bistability and stretching combined configuration compared to the bistable only or the monostable stretching only configuration.

Manipulating a micro-cantilever between its optomechanical bistable states in a lever-based Fabry-Pérot cavity

In this paper, we demonstrate experimentally switching a cantilever between its optomechanical bistable states in a low finesse optical cavity. Our experiment shows that the deformation of cantilever can be manipulated by tuning the cavity resonance. When the laser power increases across the threshold value of 110 μW, optomechanical bistability is induced by strong static photothermal backaction at room temperature. Numerical calculation revealed that the bistable effect originates from the multi-well potential created via the optomechanical interaction. Switching of the cantilever between the bistable states was achieved by tuning the cavity to the corresponding boundaries of the bistable region, where the barrier between the bistable states vanishes.

Chemical linkage functions of poly(ether imide)s on the resistive switching memory effects

A series of aromatic poly(ether imide)s, AZTA-PEIs containing triphenylamine and 1,2,4-triazole moieties are prepared and characterized. All the polymers with inherent viscosity from 0.58 to 1.1dL/g show glass transition temperatures in the range of 250–278°C. Resistive switching memory devices are constructed based on the processable poly(ether imide) (AZTA-PEIa). The device can be switched from the initial OFF state to the ON state under either positive or negative electrical sweep at about ±3.2V. The ON state is nonvolatile and can maintain the high conducting state even turning off the electrical power and applying a reverse bias. The device fulfills the requirements of a write-once read-many times memory (WORM) with a high ON/OFF current ratio up to 105 and a long retention time in both ON and OFF states. The bistable switching effects of the polymer result from the conformation-coupled charge transfer from electron donors (triazole-substituted triphenylamine moieties) to electron acceptors (phthalimide moieties). By comparing with the memory behaviors of analogue polymers, the functions of ether and imide in the chemical polymer structure on the memory behaviors are discussed.

Effect of the doping level on temperature bistability in a silicon wafer

The influence of the doping level on the effect of the temperature bistability in a silicon wafer upon radiative heat transfer between the wafer and the elements of the heating system is studied. Theoretical transfer characteristics are constructed for a silicon wafer doped with donor and acceptor impurities. These characteristics are compared with the transfer characteristics obtained during heating and cooling of wafers with the hole conduction (with dopant concentrations of 1015, 2 × 1016, and 3 × 1017 cm−3) and electron conduction (with impurity concentrations of 1015 and 8 × 1018 cm−3) in a thermal reactor of the rapid thermal annealing setup. It is found that the width and height of the hysteresis loop decrease with increasing dopant concentration and are almost independent of the type of conduction of the silicon wafer. The critical value of the impurity concentration of both types is 1.4 × 1017 cm−3. For this concentration, the loop width vanishes, and the height corresponds to the minimal value of the temperature jump (∼200 K). The mechanism of temperature bistability in the silicon wafer upon radiative heat transfer is discussed.

Nonlinear phenomena of left-handed nonlinear split-ring resonators

We theoretically analyze a two-dimensional periodic structure consisting of period nonlinear split-ring resonators (SRRs) with varactor diode. The diode is loaded into the slit of the SRRs. Then, we demonstrate nonlinear phenomena of left-handed nonlinear SRRs. This paper introduces nonlinear SRRs based on left-handed (LH) media and simulates self-tuning mechanisms, bistable effects in the microwave frequency range. In addition, with the increase of input power, the nonlinear response of the SRRs becomes multi-valued, paving a way for creating bistable tunable metamaterials.

Nonreciprocal millimeter wave latching phase shifter utilizing magnetodielectric phase-frequency bistability effect

The effect of phase-frequency bistability in magneto-dielectric hexaferrite resonator has been investigated in 35–40 GHz frequency range. It is shown that switching between saturated and multidomain states results in switching of mode frequency and corresponding modification of insertion losses and phase shift in the region between initial and final resonant frequencies. A theory based on equivalent circuit model is found to adequately predict both losses and phase shift. A prototype of millimeter-wave latching discrete phase shifter on the basis of the bistability effect is suggested, and its parameters are compared with characteristic for discrete phase shifters. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1759–1764, 2014

Negative differential resistance and carrier transport of electrically bistable devices based on poly(N-vinylcarbazole)-silver sulfide composites

An electrically bistable device has been fabricated based on poly(N-vinylcarbazole) (PVK)-silver sulfide (Ag2S) composite films using a simple spin-coating method. Current–voltage (I-V) characteristics of the as-fabricated devices exhibit a typical electrical bistability and negative differential resistance (NDR) effect. The NDR effect can be tuned by varying the positive charging voltage and the charging time. The maximum current ratio between the high-conducting state (ON state) and low-conducting state (OFF state) can reach up to 104. The carrier transport mechanisms in the OFF and ON states are described by using different models on the basis of the experimental result.

The forces between magnetizable particles embedded in an elastomer

The magnetostatic forces between two spherical particles made of an isotropic linearly polarizable magnetic substance and subjected to a uniform external field are studied. Under these conditions, the magnetization distribution within a given particle depends on the position and magnetization of the neighboring one. The solution for the magnetic energyof the pair has the form of power series with respect to the ratio of the particle radius to the particle center-to-center distance. The coefficients of this series are found numerically taking in about hundred terms. Evaluation of the interparticle forces, which requires differentiation of the energy over coordinates, is facilitated by proposing an approximate formula for, which enables one to avoid the laborious numeric procedure. In such a way, the distribution of interparticle forces is obtained and compared to that provided by the point magnetic moment model. It is shown that at close neighboring of the particles, the magnetic force differs substantially from that predicted by the dipole model. When analyzing the sign of the force, it is found that the angular interval between the field and the particle center-to-center vector, which corresponds to repulsion, is much more narrow than that for point dipoles. This means that in a system of magnetizable particles attraction is the dominating type of interaction. The problem is extended to magnetomechanics by considering the same pair of particles in an elastic matrix. There, the state of the system, when magnetized, is determined by interplay of magnetic and elastic forces. It is shown that in the field applied along the center-to-center direction, the configuration of the pair essentially depends on the field strength. In a low field the equilibrium interparticle gap changes but slightly since weak magnetic attraction induces weak restoring elastic forces. However, in stronger fields the system becomes bistable: besides the energy minimum located close to the initial interparticle gap, another minimum emerges, which corresponds to a close approach (clusterizing) of the particles. In the latter state both the magnetic and elastic forces are strong. This bistability effect has important implications in mechanics of soft magnetic elastomers.

Bistable effect of organic enrichment on sea spray radiative properties

AbstractPrimary‐produced sea spray aerosol, typically comprising sea‐salt, but also enriched with organic matter (OM) in biologically active oceanic regions, impacts the global radiative budget through contributions to aerosol optical depth. We show that sea spray light‐scattering enhancement, f(RH), as a function of relative humidity (RH) is suppressed when enriched with OM. A new hygroscopic growth factor parameterization reveals a dual hygroscopicity state, flipping from high hygroscopicity and high f(RH) to low hygroscopicity and low f(RH) as the OM mixing volume percentage exceeds ~ 55% in sea spray. Under elevated wind speeds, this affects the Top‐of‐atmosphere direct radiative forcing (ΔF) by reducing the cooling contribution of sea spray by ~ 5.5 times compared to pure sea‐salt spray. These results suggest a positive feedback coupling between the marine biosphere, sea spray aerosol, and the direct radiative budget.

Structural effect on controllable resistive memory switching in donor–acceptor polymer systems

Controllable bistable electrical conductivity switching behavior and resistive memory effects have been demonstrated in Al/polymer/indium-tin oxide (ITO) sandwich structure devices, constructed from non-conjugated vinyl copolymers of PTPAnOXDm with pendant donor–acceptor chromophores. The observed electrical bistability can be attributed to the field-induced intra- and intermolecular charge transfer interaction between triphenylamine electron donor (D) and oxadiazole electron acceptor (A) entities, and is highly dependent on the chemical structure of the copolymers. The vinyl copolymers showed different memory behaviors, which depended on the loading of D/A ratios. The polymers containing only donor or acceptor moieties showed as insulators, the polymers containing both donor and acceptor moieties showed as WORM, flash and DRAM as D/A ratio increased. The structural effect on the physicochemical and electronic properties of the PTPAnOXDm copolymers, viz surface morphology, thermal stability, optical absorbance and photoluminescence, and molecular orbital energy levels, were investigated systematically to study the factors that influence the memory characteristics of the devices.

Controlled optical bistability switching in a diode-pumped Tm,Ho:LLF laser

We report on the experimental demonstration of stable all-optical switching between two steady state values of optical bistability from a laser diode end-pumped quasi-three-level Tm,Ho:LLF laser in the 2 μm spectral region. The width of the hysteresis cycle and jump power values can be efficiently controlled by changing the length of the cavity, which is very important to adjust and optimize the optical switching process. The all-optical bistable switching effect is realized by only adding short positive and negative trigger pulses to the pump light. This is, to our knowledge, the first observation of all-optical bistable switching in a rare earth doped solid state laser.

Memory maintenance in calcium-based plastic synapses in the presence of background activity

How are synaptic modifications, elicited by specific patterns of activity, stable in the face of ongoing background activity? We investigate this question using a calcium-based synaptic plasticity model that is able to fit a wide range of data on various spike-timing dependent plasticity (STDP) protocols, in various in-vitro preparations (Graupner and Brunel, 2012). One of the advantages of this model is that it is possible to compute analytically how average synaptic strengths evolve in time, in the presence of random pre- and post-synaptic Poisson firing. We analyse the synapse behaviour using two parameter sets: an 'in-vitro' set, with parameters that best fit cortical slice STDP experiments (Sjostrom et al, 2001), obtained with an extracellular calcium concentration of 2.5 mM; an 'in-vivo' set, adjusting parameters of the model to in-vivo level extracellular calcium concentrations (1.5 mM, Silver and Erecinska, 1990). We start by analysing a model with no bistability at resting intracellular calcium concentrations. We find that the memory of the initial state decays exponentially, with a time constant that is inversely proportional to the background firing rate, according to a power law with an integer exponent that depends on the relative sizes of the calcium transients triggered by pre- and post-synaptic spikes with respect to the depression threshold. Importantly, the predicted memory timescales for the 'in-vivo' parameter set is several orders of magnitude longer than that for the 'in-vitro' set (hours vs minutes, for a 1/s background rate). We extend the analysis to examine the effect of synaptic bistability for memory retention. We find that under low frequency background firing (<1 Hz), bistable synapses in-vivo retain their memories for long periods (~months). Results are found to be qualitatively similar in simulations of an isolated pair of Poisson neurons, and in large-scale simulations of a network of excitatory and inhibitory neurons, operating at low rates. Our results demonstrate the role of synaptic bistability for memory retention in cortical circuits in the presence of realistic background activity.

The Spontaneous Radiation of Verticalcavity Semiconductor Optical Amplifiers in Bistable Effect

A bistable model is established including the effect of spontaneous emission in a vertical cavity semiconductor optical amplifier (VCSOA). The sensitivities to the amplified spontaneous emission (ASE) of the bistable characteristics in a VCSOA and a traditional edge emitting SOA are compared by numerical analysis. The control of the bistable characteristics and the degeneration of the bistability hysteresis are also analyzed by utilizing the modified model.

Influence of surface null potential on nonvolatile bistable resistive switching memory behavior of dilutely aluminum doped ZnO thin film

We report a correlation between surface null potential and bistable resistive switching effect in dilutely Al-doped ZnO nearly transparent thin film. The nearly symmetrical bistable resistive switching was observed at low operating potential (±1 V) with good repeatability and stability, driven by surface null potential. We report that above null potential, oxygen vacancies in the proximity of aluminum provide systematic development of conducting paths. While, the switching effect was also observed to be dopant driven in the proximity to ±1 V. The phenomenon was explained using migration of Al3+ in ZnO matrix, which dominates over oxygen vacancies.

Experimental study of the bistability in the wake behind three cylinders in triangular arrangement

By means of hot wire anemometry technique and flow visualizations, the presence of the phenomenon of the bistability around three cylinders in two triangular arrangements is investigated in an aerodynamic channel and in a water channel. Bistability occurs in flows over sets of bluff bodies forming a flip-flopping wake characterized by a biased flow switching at irregular intervals, which can represent an additional source of dynamic instabilities. Results of flow around three cylinders in triangular arrangement are presented for two configurations: one cylinder upstream and two downstream, and vice versa. The experimental data are analyzed by means of statistical, spectral and wavelet tools. The joint analysis in time and frequency domains through wavelets allows the detection of non-permanent flow structures. The results show the presence of bistable flow in the configuration with one cylinder upstream and two downstream, but no bistable effect was detected in the second configuration, where the flow shows a distinct shedding frequency.

In Situ Synthesis and Nonvolatile Rewritable‐Memory Effect of Polyaniline‐Functionalized Graphene Oxide

A new polyaniline (PANI)-functionalized graphene oxide (GO-PANI) was prepared by using an in situ oxidative graft polymerization of aniline on the surface of GO. Its highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), ionization potential (IP), and electron affinity (EA) values experimentally estimated by the onset of the redox potentials were -5.33, -3.57, 5.59, and 3.83 eV, respectively. A bistable electrical-switching effect was observed in electronic device with the GO-PANI film sandwiched between the indium tin oxide (ITO) and Al electrodes. This device exhibited two accessible conductivity states, that is, the low-conductivity (OFF) state and the high-conductivity (ON) state, and can be switched to the ON state under a negative electrical sweep, and can also be reset to the initial OFF state by a reverse (positive) electrical sweep. The ON state is nonvolatile and can withstand a constant voltage stress of -1 V for 3 h and 10(8) read cycles at -1 V under ambient conditions. The nonvolatile nature of the ON state and the ability to write, read, and erase the electrical states, fulfill the functionality of a rewritable memory. An ON/OFF current ratio of more than 10(4) at -1 V achieved in this memory device is high enough to promise a low misreading rate through the precise control of the ON and OFF states. The mechanism associated with the memory effects was elucidated from molecular simulation results.

Novel piezoelectric bistable oscillator architecture for wideband vibration energy harvesting

Bistable vibration energy harvesters are attracting more and more interest because of their capability to scavenge energy over a large frequency band. The bistable effect is usually based on magnetic interaction or buckled beams. This paper presents a novel architecture based on amplified piezoelectric structures. This buckled spring–mass architecture allows the energy of the dynamic mass to be converted into electrical energy in the piezoelectric materials as efficiently as possible. Modeling and design are performed and a normalized expression of the harvester behavior is given. Chirp and band-limited noise excitations are used to evaluate the proposed harvester’s performances. Simulation and experimental results are in good agreement. A method of using a spectrum plot for investigating the interwell motion is presented. The effect of the electric load impedance matching strategy is also studied. Results and comparisons with the literature show that the proposed device combines a large bandwidth and a high power density.

All-optical diode in mid-infrared waveband based on self-phase modulation effect in silicon ring resonator

Nonreciprocal transmission device is one of the fundamental elements in integrated optics, and mid-infrared is a widely used waveband in many areas, such as remote sensing or spectrum analysis. An all-optical diode based on self-phase modulation (SPM) effect is numerically demonstrated in mid-infrared waveband. The diode consists of a linear waveguide and double silicon ring resonators. The nonreciprocal transmission ratio can be more than 20 dB in a power range between 0.5 mW and 20 mW, while the transmission loss in forward direction is less than 10 dB. Moreover, the influences of linear absorption coefficient of ring resonators and the bi-stability effect on the performance of the diode are discussed.