Electrical Bistability Research Articles

A Superior Ionic Conducting Plastic Crystal Near Room Temperature with Electrical Bistability and Magnetic Transition.

Multifunctional ionic plastic crystals (IPCs) are a class of unique materials that exhibit a wide range of advanced applications. In this work, we proposed a strategy for the design of multifunctional, superior ion-conducting IPCs with bistability in both magnetic and electric properties, moreover, we successfully prepared and thoroughly characterized such an IPC, [PMPyr][Ni(mnt)2] (1; PMPyr+=N-propyl-N-methylpyrrolidinium, and mnt2-=maleonitriledithiolate). Plastic crystal 1 exhibits superior ion conduction near room temperature, and its ion conductivity reaches the order of 10-2 S cm-1 at 373 K. Remarkably, the crystal-to-plastic crystal transformation results in 1 simultaneously exhibiting electrical bistability and magnetic transition. Our study paves the way for the development of new IPCs with desirable functional properties.

Thiol-acrylate based polymer wall-stabilized cholesteric liquid crystal enables flexible bistable states light shutter

Bistable-states mode light shutter boost the applications in smart windows or transparent displays due to the significant energy efficiency. In this study, polymer wall-stabilized cholesteric liquid crystals (PWSCLC) with regular microstructures and outstanding electric field frequency-controlled bistability were prepared using non-liquid crystalline thiol-acrylate monomers system and polymerization under a photomask. The addition and proportion of the thiol monomer played an essential role in the morphology structures of the polymer network. Thanks to the effectively modulation of polymerization speed, periodic regular polymer wall morphology was obtained, which improved the transmittance and the long-term stability. Under a suitable voltage, repeatedly reversible switch between transparent and scattering states was successfully realized via frequency regulation, and both states remained stable for more than 10 days after removing electric field. Remarkably, the mechanical strength of the PSWCLC film was significantly improved due to the relatively high polymer concentration, proving feasibility for the flexible applications and large-scale preparation.

Peredacha spinovogo momenta i nelineynyy kvantovyy elektronnyy transport v kiral'nykh gelimagnetikakh

We construct a nonlinear theory of electric resistance of chiral helimagnets, in which the shape changes and the magnetization spiral starts rotating during the passage of electric current due to the spin transfer torque effect. It is shown that the rotation of the spin spiral under the action of the passing current, the electric resistance of the helimagnet is always lower than the resistance of a helimagnet in which the spin spiral is stationary. It is found that the current–voltage characteristic of the helimagnet in the presence of the spin transfer torque from the conduction electron system to the system of localized electrons can be essentially nonlinear. The possibility of the spin electric bistability effect in helimagnets is predicted for the situation when the spin contribution to electric resistance of a helimagnet can take two different values for the same value of the current passing through it. The possibility of realization of states with a negative differential resistance in helimagnets is demonstrated.

Magnetic and electrical bistability in hybrid composites of conducting organic polymers with [Fe(NH2-trz)3]n[SO4]n

Spin crossover (SCO) materials are potential building blocks for multifunctional hybrids. Mechanochemical processing appears as a promising tool to achieve bistable conducting composites with synergic magnetic and electrical bistability.

Host-guest synergy of CH3NH3PbBr3@Ln-MOFs enabling tunable green luminescence and switchable memory

Metal organic frameworks (MOFs) contain ordered pores capable of encapsulating varied types of guests and provide a platform to expand the flexibility and versatility of the host-guest composites. Herein, by encapsulating CH3NH3PbBr3 NPS into Ln-MOFs (Ln = La, Nd, Pr, Sm), four CH3NH3PbBr3@Ln-MOFs host-guest composites were fabricated and served as a bifunctional platform. The temperature-dependent luminescence properties of the CH3NH3PbBr3@Ln-MOFs were explored and the results revealed their tuneable green luminescence performance. In particular, the CH3NH3PbBr3@Sm-MOF exhibits a variety of colours from green to blue to purple and an excellent quantum yield of 0.98. The photocurrent responses and theoretical calculations reveal the enhancement mechanism of CH3NH3PbBr3 on charge-hole separation owing to its unique host-guest synergy. Moreover, the CH3NH3PbBr3@Sm-MOF exhibits the excellent electrical bi-stability with a high ON/OFF ratio of 104. Hence, the CH3NH3PbBr3@Ln-MOFs host-guest composites are promising candidates for a new generation of photovoltaic, light-emitting, and switching memories devices.

ReWORM Memory Effect in PET-Metal Fiber-Based Electroconductive Yarn

Write-once-read-many (WORM) memory effect is reported in the 19.68 Tex, 80:20 ratio polyethylene terephthalate (PET)-metal fiber spun electroconductive yarn. The yarn sample displayed a typical WORM memory behavior having electrical bistability with an OFF/ ON resistance ratio up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{9}}$ </tex-math></inline-formula> and a long retention period. As the polyester fibers transform from amorphous (resistive state) to semicrystalline (conductive state) upon the application of bias voltage, the charge conduction changes from electronic to ionic, above the glass transition temperature. Furthermore, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}-{V}$ </tex-math></inline-formula> curves were fit to explain the charge carrier transport mechanisms in the WORM behavior. Additionally, upon intentional mechanical perturbation, the sample could reset to its native high-resistive state (the phenomenon is termed as Reset WORM or ReWORM), ready for another WORM storage cycle.

Global dynamics analysis of a Filippov Hindmarsh–Rose neuron model

The electromagnetic induction induced by neuron membrane potential plays an important role in regulating its electrical activities, bistability and hidden dynamics. In this paper, a nonsmooth threshold control strategy is proposed, in which the membrane potential is utilized as the threshold to determine the switching function corresponding to the electromagnetic induction intensity and external stimulus current. Consequently, a four-dimensional Filippov-type HR neuron model is established. First, the existence, stability and global bifurcation behaviors of equilibrium points of two subsystems are discussed by using stability theory and numerical simulation. Then, the bistable behavior and evolution modes of subsystems are investigated based on the two-parameter bifurcation analysis. Further, the existence of various equilibrium points and sliding dynamics of the system are analyzed by Filippov convex method and Utkin’s equivalent control method. Finally, the sliding firing modes and multistable features under the control of the threshold are revealed by the method of fast-slow variable dissection. These results will provide useful theoretical support for understanding the hidden dynamic mechanism of neurons and constructing functional neural networks.

To Be or Not to Be - Review of Electrical Bistability Mechanisms in Polymer Memory Devices.

Organic memory devices are a rapidly evolving field with much improvement in device performance, fabrication, and application. But the reports have been disparate in terms of the material behavior and the switching mechanisms in the devices. And, despite the advantages, the lack of agreement in regards to the switching behavior of the memory devices is the biggest challenge that the field must overcome to mature as a commercial competitor. This lack of consensus has been the motivation of this work wherein various works are compiled together to understand influencing factors in the memory devices. Different works are compared together to discover some clues about the nature of the switching occurring in the devices, along with some missing links that would require further investigation. The charge storage mechanism is critically analyzed alongside the various resistive switching mechanisms such as filamentary conduction, redox-based switching, metal oxide switching, and other proposed mechanisms. The factors that affect the switching process are also analyzed including the effect of nanoparticles, the effect of the choice of polymer, or even the effect of electrodes on the switching behavior and the performance parameters of the memory device.

Electrical bistability based on metal-organic frameworks.

Electrical bistability existing in biochemical networks is critical for the proper functionalization of living systems. The development of artificial materials with electrical bistability begun to attract much interest due to their broad application prospects, especially in the field of memristors. Metal-organic frameworks (MOFs) have advantages in regular pores, crystallinity, structural designability and easy functionalization, which can promote the construction of novel MOF-based memristors and facilitate a better understanding of switching mechanisms. Here, we highlight recent advances in electrically bistable MOFs as memristors, and discuss their switching mechanisms, including interfacial reaction, proton-transfer mechanism, metal ion migration, charge trapping/detrapping and other mechanisms. Challenges and future perspectives are also presented.

Ternary Conductance Switching Realized by a Pillar[5]arene‐Functionalized Two‐Dimensional Imine Polymer Film

Nowadays, most manufacturing memory devices are based on materials with electrical bistability (i. e., "0" and "1") in response to an applied electric field. Memory devices with multilevel states are highly desired so as to produce high-density and efficient memory devices. Herein, we report the first multichannel strategy to realize a ternary-state memristor. We make use of the intrinsic sub-nanometer channel of pillar[5]arene and nanometer channel of a two-dimensional imine polymer to construct an active layer with multilevel channels for ternary memory devices. Low threshold voltage, long retention time, clearly distinguishable resistance states, high ON/OFF ratio (OFF/ON1/ON2=1 : 10 : 103 ), and high ternary yield (75 %) were obtained. In addition, the flexible memory device based on 2DPTPAZ+TAPB can maintain its stable ternary memory performance after being bent 500 times. The device also exhibits excellent thermal stability and can tolerate a temperature as high as 300 °C. It is envisioned that the results of this work will open up possibilities for multistate, flexible resistive memories with good thermal stability and low energy consumption, and broaden the application of pillar[n]arene.

Incorporating a redox active entity to attain electrical bistability in a polymer semiconductor

Owing to the advantages of 3-D printable stack, scalability and low cost solution state production, polymer-based resistive memory devices have been identified as the promising alternative for conventional oxide technology. Resistive memory devices based on the redox switch mechanism is particularly found to yield high precision with respect to the operational voltages. Reversible non-volatile resistive state switching was realized with high device yield (>80%), with a redox-active chemical entity conjugated to the polymeric semiconductor, and the control experiments with the model compound confirmed the imperative role of the redox-active anthraquinone center in the polymeric backbone. Highly uniform nanodomains and the trap free layers excluded the possibilities of other known switching mechanisms. Optical studies and the molecular modelling data assert the presence of strong charge transfer characteristics upon optical excitation due to the insertion of the anthraquinone unit, which was detrimental in exhibiting bistable conductive states in electrical bias as well.

Analog and Digital Bipolar Resistive Switching in Co-Al-Layered Double Hydroxide Memristor.

We demonstrate a nonvolatile memristor based on Co–Al-layered double hydroxide (Co–Al LDH). We also introduce a memristor that has a hexazinone-adsorbing Co–Al LDH composite active layer. Memristor characteristics could be modulated by adsorbing hexazinone with Co–Al LDHs in the active layer. While different, Co–Al LDH-based memory devices show gradual current changes, and the memory device with small molecules of adsorbed hexazinone undergo abrupt changes. Both devices demonstrate programmable memory peculiarities. In particular, both memristors show rewritable resistive switching with electrical bistability (>105 s). This research manifests the promising potential of 2D nanocomposite materials for adsorbing electroactive small molecules and rectifying resistive switching properties for memristors, paving a way for design of promising 2D nanocomposite memristors for advanced device applications.

Swift heavy ion irradiation induced negative differential resistance and transport of charge carriers in conducting polymer-metal oxide hybrids

An intriguing phenomenon of the negative differential resistance (NDR) in conducting polymer-metal oxide hybrids is manifested upon measuring the In-situ current-voltage characteristics. Anomalous evolution of low current state leading to the electrical bistability has also been observed as an induced effect at low ion irradiation doses and explained by invoking ordering of the polymer chains and electric-field induced charge transfer mechanisms. Later, a disorder leading to damage is observed at higher doses by the diffusion of irradiation-induced electrically active free radicals and defect centers within the active region of the device. This leads to the device into a high current state of electrical bistability. Further, the observed NDR is attributed to the tunneling of carriers along with transient charging of molecular chains by trapping of charge carriers at the heterojunction interfaces induced by ion irradiation. It is further confirmed by anomalous response of voltage shifting in the conductance response upon incremented doses of irradiation. Efforts are envisaged to understand the processes of irradiation interactions and their influences on the transport of charge carriers by fitting experimental data using various conduction models such as Ohmic conduction, space-charge-limited conduction (SCLC), and trap-assisted SCLC. Thus, such low-cost and simple design devices have lots of potential applications for radiation harsh environments and could be easily integrated into the existing silicon-based technology.

Photoactive Cu2FeSnS4 thin films: Influence of stabilizers

Quaternary photo-active metal chalcogenide Cu2FeSnS4 (CFTS) were deposited by the sol–gel method. The negative differential resistance (NDR) phenomenon and resistive switching (RS) characteristics at room temperature was observed on ITO/CFTS/Al device. The formation of CFTS was studied in the presence of different stabilizers like lactic acid and monoethanolamine. The use of dissimilar stabilizers has led to the change in the absorption and reflectance properties of the CFTS. The impact of stabilizer on the optical band-gap energy was enumerated from UV–Vis studies. The electrical bistability of these samples was studied amongst which the thin film fabricated with the aid of lactic acid exhibited better performance and can be extensively used for memory applications like random access memory (RAM) applications. Finally, the as-fabricated CFTS thin films were sulfurized and the photo-electrical properties were examined. From these studies, it is inferred that the electrical bistability vanishes after sulfurization. However, the photo-response of the sulfurized sample was improved when compared to its counterpart. These works provide a breakthrough for exploring the memory application of multifunctional material with further multiple physical attributes.

Electrical conductivity and magnetic bistability in metal–organic frameworks and coordination polymers: charge transport and spin crossover at the nanoscale

Electrical conductivity and magnetic bistability in metal–organic frameworks and coordination polymers: charge transport and spin crossover at the nanoscale

Reversible photo/thermal stimuli-responsive electrical bistability performance in supramolecular co-crystals accompanied by crystalline-to-amorphous transformations

A co-crystal-based device exhibits reversibly stimuli-responsive switchable conductivity states, and its photo/thermal responsive electrically bistable switching mechanism was proposed.

Electrical bistability in MoS2 nano-sheets doped polymeric nanocomposite films

Herein, we report the preparation and characterisation of nanocomposite films comprised of poly(ethylene oxide) (PEO) dispersed with exfoliated MoS2 nano-sheets. Few-layer nano-sheets of MoS2 with good stability and yield were prepared using liquid phase exfoliation method. Optical spectroscopic techniques and atomic force microscopy confirm exfoliation of MoS2 into few-layer nano-sheets. The current-voltage characteristics were investigated on two terminal devices by putting composite of PEO and MoS2 nano-sheets as the active material between ITO and aluminium electrodes. Electrical bistability observed with low resistance state (LRS) and high resistance states (HRS) were reversibly achieved by voltage sweeping. LRS (ON) and HRS (OFF) occurred at -3.5 V and 2 V respectively when the compliance was set at 50 µA. The resistance-ratio (Roff/Ron) ∼ 104 is achieved where the switching between resistance states is due to trap assisted space-charge limited current

Electrical conductivity and magnetic bistability in metal-organic frameworks and coordination polymers: charge transport and spin crossover at the nanoscale.

Materials scientists are currently shifting from purely inorganic, organic and silicon-based materials towards hybrid organic-inorganic materials to develop increasingly complex and powerful electronic devices. In this context, it is undeniable that conductive metal-organic frameworks (MOFs) and bistable coordination polymers (CPs) are carving a niche for themselves in the electronics world. The tunability and processability of these materials alongside the combination of electrical conductivity with porosity or spin transition offers unprecedented technological opportunities for their integration into functional devices. This review aims to summarise the chemical strategies that have guided the design of this type of materials and the identified opportunities for further development. We also examine the strategies to process them as thin films and stress the importance of analysing the effects of nanostructuration on their physical properties that might be crucial for device performance. Finally, we showcase relevant examples of functional devices that have received increasing attention from researchers and highlight the opportunities available for more sophisticated applications that could take full advantage of the combination of electrical conductivity and magnetic bistability.

The engineering of stilbazolium/iodocuprate hybrids with optical/electrical performances by modulating inter-molecular charge transfer among H-aggregated chromophores

Good electrical bistability performances in stilbazolium/iodocuprate hybrids stem from the better face-to-face π⋯π stacking interactions induced by the substituents with appropriate lengths and electronic natures.

Simultaneous Spin-Crossover Transition and Conductivity Switching in a Dinuclear Iron(II) Coordination Compound Based on 7,7',8,8'-Tetracyano-p-quinodimethane.

The reaction of Fe(OAc)2 and Hbpypz with neutral TCNQ results in the formation of [Fe2 (bpypz)2 (TCNQ)2 ](TCNQ)2 (1), in which Hbpypz=3,5-bis(2-pyridyl)pyrazole and TCNQ=7,7',8,8'-tetracyano-p-quinodimethane. Crystal packing of 1 with uncoordinated TCNQ and π-π stacking of bpypz- ligands produces an extended two-dimensional supramolecular coordination assembly. Temperature dependence of the dc magnetic susceptibility and heat capacity measurements indicate that 1 undergoes an abrupt spin crossover (SCO) with thermal spin transition temperatures of 339 and 337 K for the heating and cooling modes, respectively, resulting in a thermal hysteresis of 2 K. Remarkably, the temperature dependence of dc electrical transport exhibits a transition that coincides with thermal SCO, demonstrating the thermally induced magnetic and electrical bistability of 1, strongly correlating magnetism with electrical conductivity. This outstanding feature leads to thermally induced simultaneous switching of magnetism and electrical conductivity and a magnetoresistance effect.