Multi-state Switching Research Articles

Electric field-assisted resonance frequency tuning in free standing nanomechanical devices for application in multistate switching using a phase change material.

VO2 possesses a unique property of solid-state phase transition near room temperature wherein it transforms from monoclinic (M1) to tetragonal phase (R) that alters its physical properties, such as resistivity, mechanical modulus, and lattice strain, at an ultrafast time scale known as MIT. Such a phenomenon offers a distinct advantage to use VO2 in switching applications using heat flux as a stimulus. However, such alteration in properties can also be triggered under an electric field (E), which is known as E-MIT. A nanomechanical resonator coated with VO2 recently received traction where the resonance behavior can be modulated by taking advantage of its phase transition. Herein, we demonstrate that by fabricating a microstring of 400 μm (L) × 5 μm (W) × 240 nm (t) of suspended SiNx coated with VO2, the frequency (fr) of the resonator can be modulated by applying an electric field. We show that at room temperature, the fr of the microstring can be either reduced (by 0.5% at 15 V mm-1) or enhanced (by 2.2% at 25 V mm-1) or can be varied in a cycle under E-field. Using theoretical models, we establish the simulated results and explain the processes behind it, which demonstrate excellent mechanical tuning properties of the VO2-based microstring resonator, making it an attractive and alternative option for highly efficient MEMS-based switches and neuromorphic devices.

Multiple control of azoquinoline based molecular photoswitches.

Multi-addressable molecular switches with high sophistication are creating intensive interest, but are challenging to control. Herein, we incorporated ring-chain dynamic covalent sites into azoquinoline scaffolds for the construction of multi-responsive and multi-state switching systems. The manipulation of ring-chain equilibrium by acid/base and dynamic covalent reactions with primary/secondary amines allowed the regulation of E/Z photoisomerization. Moreover, the carboxyl and quinoline motifs provided recognition handles for the chelation of metal ions and turning off photoswitching, with otherwise inaccessible Z-isomer complexes obtained via the change of stimulation sequence. Particularly, the distinct metal binding behaviors of primary amine and secondary amine products offered a facile way for modulating E/Z switching and dynamic covalent reactivity. As a result, multiple control of azoarene photoswitches was accomplished, including light, pH, metal ions, and amine nucleophiles, with interplay between diverse stimuli further enabling addressable multi-state switching within reaction networks. The underlying structural and mechanistic insights were elucidated, paving the way for the creation of complex switching systems, molecular assemblies, and intelligent materials.

Multistate switching of scanning tunnelling microscopy machined polyoxovanadate-dysprosium-phthalocyanine nanopatterns on graphite.

We demonstrate the first formation of stable, multistate switchable monolayers of polyoxometalates (POMs), which can be electronically triggered to higher charged states with increased conductance in the current-voltage profile at room temperature. These responsive two-dimensional monolayers are based on a fully oxidised dodecavanadate cage (POV12) equipped with Dy(III)-doped phthalocyanine (Pc) macrocycles adopting the face-on orientation on highly oriented pyrolytic graphite (HOPG). The layers can be lithographically processed by the tip of a scanning tunnelling microscope (STM) to machine patterns with diameters ranging from 30 to 150 nm2.

Near-Infrared, Organic Chiroptic Switch with High Dissymmetry Factors.

Here we unveil a chiral molecular redox switch derived from PDI-based twistacenes─chPDI[2] that has the remarkable attributes of high-intensity and a broadband chiral response. This material exhibits facile, stable, and reversible multistate chiroptical switching behavior over a broad active wavelength range close to 700 nm, encompassing ultraviolet, visible, and near-infrared regions. Upon reduction, chPDI[2] exhibits a substantial increase in the amplitude of its circular dichroic response, with an outstanding |ΔΔε| > 300 M-1 cm-1 and a high dissymmetry factor of 3 × 10-2 at 960 nm. DFT calculations suggest that the long wavelength CD signal for doubly reduced chPDI[2] originates from excitation of the PDI backbone to the π* orbital of the bridging alkene. Importantly, the dimer's molecular contortion facilitates ionic diffusion, enabling chiral switching in solid state films. The high dissymmetry factors and near-infrared response establish chPDI[2] as a unique chiroptic switch.

Application of Inverse Design Approaches to the Discovery of Nonlinear Optical Switches.

Molecular switches, in which a stimulus induces a large and reversible change in molecular properties, are of significant interest in the domain of photonics. Due to their commutable redox states with distinct nonlinear optical (NLO) properties, hexaphyrins have emerged as a novel platform for multistate switches in nanoelectronics. In this study, we employ an inverse design algorithm to find functionalized 26R→28R redox switches with maximal βHRS contrast. We focus on the role of core modifications, since a synergistic effect with meso-substitutions was recently found for the 30R-based switch. In contrast to these findings, the inverse design optima and subsequent database analysis of 26R-based switches confirm that core modifications are generally not favored when high NLO contrasts are targeted. Moreover, while push-pull combinations enhance the NLO contrast for both redox switches, they prefer a different arrangement in terms of electron-donating and electron-withdrawing functional groups. Finally, we aim at designing a three-state 26R→28R→ 30R switch with a similar NLO response for both ON states. Even though our best-performing three-state switch follows the design rules of the 30R-based component, our chemical compound space plots show that well-performing three-state switches can be found in regions shared by high-responsive 26R and 30R structures.

Field-Free Spin-Orbit Torque-Induced Magnetization Switching in the IrMn/CoTb Bilayers with a Spontaneous In-Plane Exchange Bias.

Spin-orbit torque (SOT)-induced magnetization switching in ferrimagnetic materials is promising for application in a new generation of information storage devices. Here, we demonstrate SOT-induced field-free magnetization switching of the perpendicularly magnetized CoTb ferrimagnet layer in the IrMn/CoTb bilayer, in which the in-plane magnetic inversion symmetry is broken by a spontaneous in-plane exchange bias (IEB) established by isothermal crystallization of the IrMn layer. We obtain a significant SOT effective field acting on the CoTb layer and a large effective spin Hall angle in this system, derived by the second harmonic voltage measurement method. Moreover, the IrMn/CoTb bilayer demonstrates multistate magnetic switching behavior with different amplitudes of current pulses at zero field, which can mimic the synaptic weight updates in the neuromorphic network. These findings make the IrMn/CoTb bilayer with spontaneous IEB a promising candidate for potential applications in multilevel storage and neuromorphic computing.

Ligand Modifications Produce Two-Step Magnetic Switching in a Cobalt(dioxolene) Complex.

Mononuclear monodioxolene valence tautomeric (VT) cobalt complexes typically exist in their low spin (l.s.) CoIII (cat2- ) and high spin (h.s.) CoII (sq⋅- ) forms (cat2- =catecholato, and sq⋅- =seminquinonato forms of 3,5-di-t Bu-1,2-dioxolene), which reversibly interconvert via temperature-dependent intramolecular electron transfer. Typically, the remaining four coordination sites on cobalt are supported by a tetradentate ligand whose properties influence the temperature at which VT occurs. We report that replacing one chelating pyridyl arm of tris(2-pyridylmethyl)amine (tpa) with a weaker field ortho-anisole moiety facilitates access to a third magnetic state, and examine a series of related complexes. Variable temperature crystallographic, magnetic, calorimetric, and spectroscopic studies support that this third state is consistent with l.s. CoII (sq⋅- ). Thus, our ligand modifications not only provide access to the VT transition from l.s. CoIII (cat2- ) to l.s. CoII (sq⋅- ), but at higher temperatures, the complex undergoes spin crossover from l.s. CoII (sq⋅- ) to h.s. CoII (sq⋅- ), representing the first example of two-step magnetic switching in a mononuclear monodioxolene cobalt complex. We hypothesize that ligand dynamicity may facilitate access to the rarely observed l.s. CoII (sq⋅- ) intermediate state, suggesting a new design criterion in the development of stimulus-responsive multi-state molecular switches.

Encoding multistate charge order and chirality in endotaxial heterostructures

High-density phase change memory (PCM) storage is proposed for materials with multiple intermediate resistance states, which have been observed in 1T-TaS2 due to charge density wave (CDW) phase transitions. However, the metastability responsible for this behavior makes the presence of multistate switching unpredictable in TaS2 devices. Here, we demonstrate the fabrication of nanothick verti-lateral H-TaS2/1T-TaS2 heterostructures in which the number of endotaxial metallic H-TaS2 monolayers dictates the number of resistance transitions in 1T-TaS2 lamellae near room temperature. Further, we also observe optically active heterochirality in the CDW superlattice structure, which is modulated in concert with the resistivity steps, and we show how strain engineering can be used to nucleate these polytype conversions. This work positions the principle of endotaxial heterostructures as a promising conceptual framework for reliable, non-volatile, and multi-level switching of structure, chirality, and resistance.

Programmable supramolecular chirality in non-equilibrium systems affording a multistate chiroptical switch

The dynamic regulation of supramolecular chirality in non-equilibrium systems can provide valuable insights into molecular self-assembly in living systems. Herein, we demonstrate the use of chemical fuels for regulating self-assembly pathway, which thereby controls the supramolecular chirality of assembly in non-equilibrium systems. Depending on the nature of different fuel acids, the system shows pathway-dependent non-equilibrium self-assembly, resulting in either dynamic self-assembly with transient supramolecular chirality or kinetically trapped self-assembly with inverse supramolecular chirality. More importantly, successive conducting of chemical-fueled process and thermal annealing process allows for the sequential programmability of the supramolecular chirality between four different chiral hydrogels, affording a new example of a multistate supramolecular chiroptical switch that can be recycled multiple times. The current finding sheds new light on the design of future supramolecular chiral materials, offering access to alternative self-assembly pathways and kinetically controlled non-equilibrium states.

Multi-state polarization switching and multifunction-integrated terahertz metadevice enabled by inverse resonance responses

Dynamical control of terahertz metadevices and integration of versatile functions are highly desired due to increasing practical demands. Here, we propose a multifunctional photosensitive Si hybrid metastructure consisting of twisted split-ring resonator pairs that could empower multi-state polarization switching and object-recognized imaging. The theoretical and simulated results show that inverse complete modulation of cross-polarized components could be realized via tuning the conductivity of the Si-bridge. The calculated ellipticity indicates that our metadevices possess the ability to convert linearly polarized light into left-hand circular-polarized or right-hand circular-polarized waves, as well as left-hand circular-polarized or right-hand circular-polarized into linearly polarized states. Combined with these properties, mono-parameter amplitude imaging and amplitude-phase synergistic encryption imaging are accomplished. Our research provides a new strategy to develop reconfigurable and multifunctional components in the terahertz regime.

PRICING AMERICAN OPTION USING A MODIFIED FRACTIONAL BLACK–SCHOLES MODEL UNDER MULTI-STATE REGIME SWITCHING

The American option pricing problem is examined in this work using a regime switching finite moment log-stable model. The option prices under this model are governed by a coupled system of fractional partial differential equations. Combination of the coupled system and the spatial-fractional derivative makes it extremely difficult to find an analytic solution. We have constructed a numerical algorithm to numerically solve such problems. The developed predictor-corrector type method is highly efficient and reliable in solving coupled system in each regime having different volatility and interest rates. Two-sided Riesz space fractional diffusion term is approximated using fractional finite difference scheme whereas the classical space derivative term is approximated using central difference formula. Splitting technique is utilized to construct a highly efficient scheme which can also be implemented on parallel processors. Stability and error analysis of the scheme is proved analytically and demonstrated through numerical experiments. Effect of the order of the fractional derivative (also called tail index) on the option prices is shown through graphs by performing numerical experiments for different values of the tail index.

Multistate Switching of Some Ruthenium Alkynyl and Vinyl Spiropyran Complexes.

To study the switching properties of photochromes, we undertook the synthesis and characterization of several ruthenium organometallic complexes of the type [Ru(Cp*)(dppe)(C≡C-SP)] or [Ru(CO)(dppe)(PPh3)Cl(CH═CH-SP)], where SP = spiropyran. The spectroscopic and electrochemical properties of the complexes were determined by careful cyclic voltammetric and spectroelectrochemical experiments. Whereas the mononuclear alkynyl ruthenium complexes undergo one-electron oxidations localized over the metal alkynyl moiety, the oxidation of the mononuclear vinyl ruthenium complexes is centered on the indoline moiety of the spiropyran. Through these studies, we demonstrate access to several stable redox states, in addition to switching states attained via acidochromism and/or photoisomerization.

Propagation Delay and Power Dissipation Analysis for a 2-Bit SRAM Using Multi-State SWS Inverter

This paper presents a study on the propagation delay and power dissipation of a 2-bit static random-access memory (SRAM) with two cross-coupled multi-state spatial wave function switching (SWS) CMOS inverters. The proposed SRAM design utilizes the advantages of the CMOS-SWS inverter, such as its small area, low power consumption, and high speed. The 2-bit SRAM circuit simulations were carried out in Cadence to analyze the power dissipation and propagation delay. An Analog Behavioral Model (ABM) and the Berkeley Short-channel IGFET Model (BSIM4.6) in 0.18-μm technology were combined to create this model. The analysis of the propagation delay shows that the multi-state CMOS-SWS SRAM significantly reduces the delay compared to other multi-state 6T SRAM memories. Additionally, the analysis of the power dissipation shows that the multi-state SWS-SRAM is comparable to conventional SRAMs. These results demonstrate the potential of multi-state SWS-SRAM for improving the performance of memory circuits and provide valuable insights for future design optimization.

Nanoscale multistate resistive switching in WO3 through scanning probe induced proton evolution

Multistate resistive switching device emerges as a promising electronic unit for energy-efficient neuromorphic computing. Electric-field induced topotactic phase transition with ionic evolution represents an important pathway for this purpose, which, however, faces significant challenges in device scaling. This work demonstrates a convenient scanning-probe-induced proton evolution within WO3, driving a reversible insulator-to-metal transition (IMT) at nanoscale. Specifically, the Pt-coated scanning probe serves as an efficient hydrogen catalysis probe, leading to a hydrogen spillover across the nano junction between the probe and sample surface. A positively biased voltage drives protons into the sample, while a negative voltage extracts protons out, giving rise to a reversible manipulation on hydrogenation-induced electron doping, accompanied by a dramatic resistive switching. The precise control of the scanning probe offers the opportunity to manipulate the local conductivity at nanoscale, which is further visualized through a printed portrait encoded by local conductivity. Notably, multistate resistive switching is successfully demonstrated via successive set and reset processes. Our work highlights the probe-induced hydrogen evolution as a new direction to engineer memristor at nanoscale.

Reprogrammable magnetization pattern and shape morphing of phase-change magnetic soft composites

Magnetic soft composites with programmable magnetization patterns are highly desirable for diverse applications due to their multimodal magnetic response and locomotion. Despite substantial progress achieved in magnetic programming approaches, reprogrammable magnetization using low magnetic fields is still in development and challenging. Here, we report a one-step multi-direction magnetic reorientation strategy capable of reprogramming magnetization patterns in soft composites consisting of an elastomer matrix and magnetized ferromagnetic microparticles encapsulated by a phase-change polymer. Our approach is first based on the overall heating of these soft composites to achieve polymer phase transition, and then use magnet arrays to locally regulate the magnetic field distribution to achieve magnetic reorientation and programmable magnetization. Importantly, this approach allows us to reconstruct the desired magnetization patterns by reheating and redesigning the applied magnetic field. Using this approach, we numerically and experimentally demonstrate that multimodal magnetization and deformation patterns of millimeter-level strip-shaped and multi-arm phase-change soft composites can be achieved without changing the composite structure and the externally applied magnetic field. Furthermore, we demonstrate its functional applications in developing a multistate circuit switching, as well as a flexible magnetic recording that can present a variety of information such as numbers, letters, and face-based patterns.

Ladder-type conjugated molecules as robust multi-state single-molecule switches

•Synthesis of a methylthio-functionalized, ladder-type oligoaniline derivative •Excellent stability and high molecular conductance in oxidized and protonated states •Robust switching of single-molecule conductance among three different states Ladder-type molecular structures greatly enhance the chemical stability of oligoaniline derivatives and impart well-defined physical properties to multiple molecular charge states. In this work, we characterize the charge transport properties of a ladder-type cyclohexadiene-1,4-diimine derivative at various protonation, lithiation, and oxidation states using single-molecule techniques. Our results show that a ladder-type oligoaniline derivative serves as a robust and reversible molecular switch with over two orders of magnitude changes in molecular conductance when controlled using chemical or electrochemical stimuli. Experimental results are complemented by molecular modeling using density functional theory (DFT) and nonequilibrium Green’s function-DFT (NEGF-DFT) to elucidate charge transport mechanisms at different molecular states. Overall, this work provides new strategies for advancing the stability, programmability, and efficiency of molecular charge transport using ladder-type single-molecule switches. Ladder-type molecular structures greatly enhance the chemical stability of oligoaniline derivatives and impart well-defined physical properties to multiple molecular charge states. In this work, we characterize the charge transport properties of a ladder-type cyclohexadiene-1,4-diimine derivative at various protonation, lithiation, and oxidation states using single-molecule techniques. Our results show that a ladder-type oligoaniline derivative serves as a robust and reversible molecular switch with over two orders of magnitude changes in molecular conductance when controlled using chemical or electrochemical stimuli. Experimental results are complemented by molecular modeling using density functional theory (DFT) and nonequilibrium Green’s function-DFT (NEGF-DFT) to elucidate charge transport mechanisms at different molecular states. Overall, this work provides new strategies for advancing the stability, programmability, and efficiency of molecular charge transport using ladder-type single-molecule switches.

Titelbild: Multistate Structural Switching of [3]Catenanes with Cyclic Porphyrin Dimers by Complexation with Amine Ligands (Angew. Chem. 14/2023)

Structural switching of [3]catenane was induced by fitting the puzzle pieces. In their Research Article (202217002), Jun Terao et al. report a method for ligand-controlled structural switching of [3]catenane, which was realized by the complexation of metal ions on [3]catenane with added complementarily fitted organic ligands, like pieces in a jigsaw puzzle. The high tailorability of organic ligands offers multiple pieces with various sizes and numbers of coordination sites, enabling multistate structural switching of [3]catenane. Structural switching of [3]catenane was induced by fitting the puzzle pieces. In their Research Article (202217002), Jun Terao et al. report a method for ligand-controlled structural switching of [3]catenane, which was realized by the complexation of metal ions on [3]catenane with added complementarily fitted organic ligands, like pieces in a jigsaw puzzle. The high tailorability of organic ligands offers multiple pieces with various sizes and numbers of coordination sites, enabling multistate structural switching of [3]catenane. Organic Electronics Carboranes Batteries Enzyme Catalysis

Cover Picture: Multistate Structural Switching of [3]Catenanes with Cyclic Porphyrin Dimers by Complexation with Amine Ligands (Angew. Chem. Int. Ed. 14/2023)

Structural switching of [3]catenane was induced by fitting the puzzle pieces. In their Research Article (DOI: 10.1002/anie.202217002), Jun Terao et al. report a method for ligand-controlled structural switching of [3]catenane, which was realized by the complexation of metal ions on [3]catenane with added complementarily fitted organic ligands, like pieces in a jigsaw puzzle. The high tailorability of organic ligands offers multiple pieces with various sizes and numbers of coordination sites, enabling multistate structural switching of [3]catenane.

Multistate Structural Switching of [3]Catenanes with Cyclic Porphyrin Dimers by Complexation with Amine Ligands

AbstractCatenanes with multistate switchable properties are promising components for next‐generation molecular machines and supramolecular materials. Herein, we report a ligand‐controlled switching method, a novel method for the multistate switching of catenanes controlled by complexation with added amine ligands. To verify this method, a [3]catenane comprising cyclic porphyrin dimers with a rigid π‐system has been synthesized. Owing to the rigidity, the relative positions among the cyclic components of the [3]catenane can be precisely controlled by complexation with various amine ligands. Moreover, ligand‐controlled multistate switching affects the optical properties of the [3]catenanes: the emission intensity can be tuned by modulating the sizes and coordination numbers of integrated amine ligands. This work shows the utility of using organic ligands for the structural switching of catenanes, and will contribute to the further development of multistate switchable mechanically interlocked molecules.

Multistate Structural Switching of [3]Catenanes with Cyclic Porphyrin Dimers by Complexation with Amine Ligands.

Catenanes with multistate switchable properties are promising components for next-generation molecular machines and supramolecular materials. Herein, we report a ligand-controlled switching method, a novel method for the multistate switching of catenanes controlled by complexation with added amine ligands. To verify this method, a [3]catenane comprising cyclic porphyrin dimers with a rigid π-system has been synthesized. Owing to the rigidity, the relative positions among the cyclic components of the [3]catenane can be precisely controlled by complexation with various amine ligands. Moreover, ligand-controlled multistate switching affects the optical properties of the [3]catenanes: the emission intensity can be tuned by modulating the sizes and coordination numbers of integrated amine ligands. This work shows the utility of using organic ligands for the structural switching of catenanes, and will contribute to the further development of multistate switchable mechanically interlocked molecules.