Nonvolatile Switching Research Articles

Inkjet printed IGZO memristors with volatile and non-volatile switching

Solution-based memristors deposited by inkjet printing technique have a strong technological potential based on their scalability, low cost, environmentally friendlier processing by being an efficient technique with minimal material waste. Indium-gallium-zinc oxide (IGZO), an oxide semiconductor material, shows promising resistive switching properties. In this work, a printed Ag/IGZO/ITO memristor has been fabricated. The IGZO thickness influences both memory window and switching voltage of the devices. The devices show both volatile counter8wise (c8w) and non-volatile 8wise (8w) switching at low operating voltage. The 8w switching has a SET and RESET voltage lower than 2 V and − 5 V, respectively, a retention up to 105 s and a memory window up to 100, whereas the c8w switching shows volatile characteristics with a low threshold voltage (Vth < − 0.65 V) and a characteristic time (τ) of 0.75 ± 0.12 ms when a single pulse of − 0.65 V with width of 0.1 ms is applied. The characteristic time alters depending on the number of pulses. These volatile characteristics allowed them to be tested on different 4-bit pulse sequences, as an initial proof of concept for temporal signal processing applications.

Reversible non-volatile electronic switching in a near-room-temperature van der Waals ferromagnet

Non-volatile phase-change memory devices utilize local heating to toggle between crystalline and amorphous states with distinct electrical properties. Expanding on this kind of switching to two topologically distinct phases requires controlled non-volatile switching between two crystalline phases with distinct symmetries. Here, we report the observation of reversible and non-volatile switching between two stable and closely related crystal structures, with remarkably distinct electronic structures, in the near-room-temperature van der Waals ferromagnet Fe5−δGeTe2. We show that the switching is enabled by the ordering and disordering of Fe site vacancies that results in distinct crystalline symmetries of the two phases, which can be controlled by a thermal annealing and quenching method. The two phases are distinguished by the presence of topological nodal lines due to the preserved global inversion symmetry in the site-disordered phase, flat bands resulting from quantum destructive interference on a bipartite lattice, and broken inversion symmetry in the site-ordered phase.

MoOx Synaptic Memristor with Programmable Multilevel Conductance for Reliable Neuromorphic Hardware.

Memristor holds great potential for enabling next-generation neuromorphic computing hardware. Controlling the interfacial characteristics of the device is critical for seamlessly integrating and replicating the synaptic dynamic behaviors; however, it is commonly overlooked. Herein, we report the straightforward oxidation of a Mo electrode in air to design MoOx memristors that exhibit nonvolatile ultrafast switching (0.6-0.8 mV/decade, <1 mV/decade) with a high on/off ratio (>104), a long durability (>104 s), a low power consumption (17.9 μW), excellent device-to-device uniformity, ingeniously synaptic behavior, and finely programmable multilevel analog switching. The analyzed physical mechanism of the observed resistive switching behavior might be the conductive filaments formed by the oxygen vacancies. Intriguingly, upon organization into memristor-based crossbar arrays, in addition to simulated multipattern memorization, edge detection on random images can be implemented well by parallel processing of pixels using a 3 × 3 × 2 array of Prewitt filter groups. These are vital functions for neural system hardware in efficient in-memory computing neural systems with massive parallelism beyond a von Neumann architecture.

Enhanced Computational Study with Experimental Correlation on I-V Characteristics of Tantalum Oxide (TaOx) Memristor Devices in a 1T1R Configuration.

Memristors, non-volatile switching memory platform, has recently attracted significant interest, offering unique potential to enable the realization of human brain-like neuromorphic computing efficiency. Memristors also demonstrate excellent temperature tolerance, long-term durability, and high tunability with nanosecond pulses, making them highly attractive for neuromorphic computing applications. To better understand the material processing, microstructure, and property relationship of switching mechanisms in memristor devices, computational methodologies, and tools are developed to predict the I-V characteristics of memristor devices based on tantalum oxide (TaOx) resistive random-access memory (ReRAM) integrated with an n-channel metal-oxide-semiconductor (NMOS) transistor. A multiphysics model based on coupled partial differential equations for electrical and thermal transport phenomena is solved for the high- and low-resistance states during the formation, growth, and destruction of a conducting filament through SET and RESET stages. These stages effectively represent the migration of oxygen vacancies within an oxide exchange layer. A series of parametric studies and energy minimization calculations are conducted to determine probable ranges for key material and model parameters accounting for the experimental data. The computational model successfully predicted the measured I-V curves across various gate voltages applied to the NMOS transistor in the one transistor one resistance (1T1R) configuration.

Electrically controlled nonvolatile switching of single-atom magnetism in a Dy@C84 single-molecule transistor

Single-atom magnetism switching is a key technique towards the ultimate data storage density of computer hard disks and has been conceptually realized by leveraging the spin bistability of a magnetic atom under a scanning tunnelling microscope. However, it has rarely been applied to solid-state transistors, an advancement that would be highly desirable for enabling various applications. Here, we demonstrate realization of the electrically controlled Zeeman effect in Dy@C84 single-molecule transistors, thus revealing a transition in the magnetic moment from 3.8 μB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{{{{{{\\rm{B}}}}}}}$$\\end{document} to 5.1 μB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{{{{{{\\rm{B}}}}}}}$$\\end{document} for the ground-state GN at an electric field strength of 3−\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}10 MV/cm. The consequent magnetoresistance significantly increases from 600% to 1100% at the resonant tunneling point. Density functional theory calculations further corroborate our realization of nonvolatile switching of single-atom magnetism, and the switching stability emanates from an energy barrier of 92 meV for atomic relaxation. These results highlight the potential of using endohedral metallofullerenes for high-temperature, high-stability, high-speed, and compact single-atom magnetic data storage.

Observation of nonvolatile magneto-thermal switching in superconductors

Applying a magnetic field to a solid changes its thermal-transport properties. Although such magneto-thermal-transport phenomena are usually small effects, giant magneto-thermal resistance has recently been observed in spintronic materials and superconductors, opening up new possibilities in thermal management technologies. However, the thermal conductivity conventionally changes only when a magnetic field is applied due to the absence of nonvolatility, which limits potential applications of thermal switching devices. Here, we report the observation of nonvolatile thermal switching that changes the electron thermal conductivity when a magnetic field is applied and retains the value even when the field is turned off. This unconventional magneto-thermal switching arises in commercial Sn-Pb solders and is realized by phase-separated superconducting states and resultant nonuniform magnetic flux distributions. This result confirms the versatility of the observed phenomenon and aids the development of active solid-state thermal management devices.

Field-free deterministic switching of all-van der Waals spin-orbit torque system above room temperature.

Two-dimensional van der Waals (vdW) magnetic materials hold promise for the development of high-density, energy-efficient spintronic devices for memory and computation. Recent breakthroughs in material discoveries and spin-orbit torque control of vdW ferromagnets have opened a path for integration of vdW magnets in commercial spintronic devices. However, a solution for field-free electric control of perpendicular magnetic anisotropy (PMA) vdW magnets at room temperatures, essential for building compact and thermally stable spintronic devices, is still missing. Here, we report a solution for the field-free, deterministic, and nonvolatile switching of a PMA vdW ferromagnet, Fe3GaTe2, above room temperature (up to 320 K). We use the unconventional out-of-plane anti-damping torque from an adjacent WTe2 layer to enable such switching with a low current density of 2.23 × 106 A cm-2. This study exemplifies the efficacy of low-symmetry vdW materials for spin-orbit torque control of vdW ferromagnets and provides an all-vdW solution for the next generation of scalable and energy-efficient spintronic devices.

Two-dimensional 1T′ α -VXY (X = S, Se, Te; Y = Cl, Br, I): A multifunctional vanadium chalcohalide family with room-temperature ferromagnetism and sliding ferroelectricity

Two-dimensional (2D) ferromagnetic materials with Curie temperature (Tc) above room temperature have great potential ranging from spintronics to information processing and storage. Here, we computationally design a series of 1T′α-VXY (X = S, Se, Te; Y = Cl, Br, I) monolayers with the X and Y atoms arranged alternately in the 2D plane. VXY monolayers are ferromagnetic semiconductors with Tc much higher than room temperature. Furthermore, the symmetry breaking of VXY bilayers leads to sliding ferroelectricity with large reversible out-of-plane electric polarization and moderate interlayer sliding barriers. We further show that half-metal-to-semiconductor nonvolatile field-effect switching can be achieved in multiferroic van der Waals heterostructures composed of VXY and In2S3 ferroelectric substrates due to the synergistic effect between the polarization field-induced band edge shifting and the selective charge transfer at the interface. These findings reveal a promising role of 2D Janus 1T′α-VXY in spintronics, ferroelectric, and multiferroic device applications.

Reconfigurable optical logic in silicon platform

In this paper, we present a novel, scalable, and reconfigurable optical switch that performs multiple computational logic functions simultaneously. The free-carrier depletion effect is used to perform non-volatile switching operations due to its high speed and low power consumption. We adopt the concept of optical memory using a phase-change material to realize the non-volatile reconfigurability without a constant power supply, in addition to providing a large operating bandwidth required for reconfigurability. The proposed reconfigurable optical logic architecture is realized in a compact microdisk resonator configuration, utilizing both the carrier-depletion-based modulation and phase-change optical memory. This is the first time these two modulation schemes are implemented in the same optical microdisk for the purpose of reconfigurable optical logic.

Highly Efficient Room-Temperature Nonvolatile Magnetic Switching by Current in Fe3GaTe2 Thin Flakes.

Effectively tuning magnetic state by using current is essential for novel spintronic devices. Magnetic van der Waals (vdW) materials have shown superior properties for the applications of magnetic information storage based on the efficient spin torque effect. However, for most of known vdW ferromagnets, the ferromagnetic transition temperatures lower than room temperature strongly impede their applications and the room-temperature vdW spintronic device with low energy consumption is still a long-sought goal. Here, the highly efficient room-temperature nonvolatile magnetic switching is realized by current in a single-material device based on vdW ferromagnet Fe3GaTe2. Moreover, the switching current density and power dissipation are about 300 and 60000 times smaller than conventional spin-orbit-torque devices of magnet/heavy-metal heterostructures. These findings make an important progress on the applications of magnetic vdW materials in the fields of spintronics and magnetic informationstorage.

Non-volatile electrical polarization switching via domain wall release in 3R-MoS2 bilayer

Understanding the nature of sliding ferroelectricity is of fundamental importance for the discovery and application of two-dimensional ferroelectric materials. In this work, we investigate the phenomenon of switchable polarization in a bilayer MoS2 with natural rhombohedral stacking, where the spontaneous polarization is coupled with excitonic effects through asymmetric interlayer coupling. Using optical spectroscopy and imaging techniques, we observe how a released domain wall switches the polarization of a large single domain. Our results highlight the importance of domain walls in the polarization switching of non-twisted rhombohedral transition metal dichalcogenides and open new opportunities for the non-volatile control of their optical response.

Single-shot all-optical switching of magnetization in TbFe

Thermally induced magnetization switching (TIMS) relying solely on a single laser without any applied magnetic field is a key research direction of current spintronics. Most studies on TbFe so far have focused on helicity-dependent all-optical switching (HD-AOS). In this work, we observe the TIMS on TbFe alloys excited by atomic spin dynamics simulations combined with a two-temperature model. The results show that the magnetization switching of TbFe can be found under certain damping conditions. In addition, we further investigated the reasons why energy density leads to the opposite switching time behavior of Tb and Fe, and our research results also found that changes in damping can affect the concentration and energy density range of the switching, as well as the maximum pulse duration. The dynamic behavior indicates that TbFe switching in 2 ps or less. Our findings widen the basis for fast optical switching of magnetization and break new ground for engineered materials that can be used for nonvolatile ultrafast switching using ultrashort pulses of light.

Heterogeneous integrated InP/SiC high-performance multilevel RRAM

With the advent of the Age of Big Data, resistive random-access memory (RRAM) shows considerable potential for next generation nonvolatile storage technologies owing to its simplified structure, high switching speed, and low power consumption. However, mainstream prepared materials, such as oxides and halide perovskite, face critical issues for practical applications such as switching uniformity and long-term environmental stability. In this work, we report that high carrier mobility material indium phosphide (InP) is prepared as an RRAM medium and is directly bonded to the high thermal conductivity substrate silicon carbide (SiC) at 200 °C, overcoming large (14.9%) lattice mismatch. Importantly, the bonding strength reaches 9.3 MPa, and this high-performance stable RRAM exhibits nonvolatile and reliable switching characteristics including stable endurance (200 cycles) and long data retention (2000 s). Moreover, multilevel storage is also available by modulating RESET stop voltages. This work provides broad possibilities for high-performance RRAM with structures based on traditional semiconductors in the field of nonvolatile storage.

Realization of Selector‐Memory Bi‐Functionality with Self‐Current Regulation Utilizing Poly‐Crystalline Based GST Electrolyte for Memristor Hardware Development

AbstractConductive bridge random‐access memory (CBRAM) are two terminal devices that offer excellent switching performance. In addition, CBRAM shows various switching modes, including volatile threshold switching (TS) and nonvolatile threshold switching (N‐TS). These properties expand its applications to memory, selector, biological synapses, and neurons. However, due to the uncontrollable behavior of stochastic switching between TS and N‐TS in CBRAM devices, a novel approach is needed to improve the switching performance of CBRAM. Moreover, conventional devices that have different stacking between TS and N‐TS increase fabrication cost and worsen the device yield. Here, the selector‐memory bi‐functionality with self‐current regulation effect of Ag‐inserted Ge2Sb2Te5 (GST) thin films is demonstrated. Selector‐memory bi‐functionality, having TS behavior with an adjustable on/off current, with confined conductive filaments (CFs) improves the uniformity and reduces the fabrication cost by implementing TS/N‐TS in a single stack. From the material analysis, it becomes evident that confined Ag‐based CFs within GST films are key factors for realizing selector‐memory bi‐functionality. The selector‐memory bi‐functionality is achieved through the reaction of Ag metal cations with non‐bonded Te atoms in GST film depending on field polarity. These results suggest that the Ag‐inserted GST film contributes to the development of large‐scale nonvolatile memory and neuromorphic application.

Nonvolatile Switching of Large Nonreciprocal Optical Absorption at Shortwave Infrared Wavelengths.

We report large nonreciprocal optical absorption at shortwave infrared (SWIR) wavelengths in the magnetoelectric (ME) antiferromagnet (AFM) LiNiPO_{4}. The difference in absorption coefficients for light propagating in opposite directions, divided by the sum, reaches up to ∼40% at 1450nm. Moreover, the nonreciprocity is switched by a magnetic field in a nonvolatile manner. Using symmetry considerations, we reveal that the large nonreciprocal absorption is attributed to Ni^{2+} d-d transitions through the spin-orbit coupling. Furthermore, we propose that an even larger nonreciprocity can be achieved for a Ni-based ME AFM where electric dipoles of every NiO_{6} unit and Ni^{2+} spins are orthogonal and, respectively, form a collinear arrangement. This study provides a pathway toward nonvolatile switchable one-way transparency of SWIR light.

Volatile and Nonvolatile Resistive Switching Coexistence in Conductive Point Hexagonal Boron Nitride Monolayer.

Recently, we demonstrated the nonvolatile resistive switching effects of metal-insulator-metal (MIM) atomristor structures based on two-dimensional (2D) monolayers. However, there are many remaining combinations between 2D monolayers and metal electrodes; hence, there is a need to further explore 2D resistance switching devices from material selections to future perspectives. This study investigated the volatile and nonvolatile switching coexistence of monolayer hexagonal boron nitride (h-BN) atomristors using top and bottom silver (Ag) metal electrodes. Utilizing an h-BN monolayer and Ag electrodes, we found that the transition between volatile and nonvolatile switching is attributed to the thickness/stiffness of chain-like conductive bridges between h-BN and Ag surfaces based on the current compliance and atomristor area. Computations indicate a "weak" bridge is responsible for volatile switching, while a "strong" bridge is formed for nonvolatile switching. The current compliance determines the number of Ag atoms that undergo dissociation at the electrode, while the atomristor area determines the degree of electric field localization that forms more stable conductive bridges. The findings of this study suggest that the h-BN atomristor using Ag electrodes shows promise as a potential solution to integrate both volatile neurons and nonvolatile synapses in a single neuromorphic crossbar array structure through electrical and dimensional designs.

Emerging memory electronics for non-volatile radiofrequency switching technologies

Emerging memory electronics for non-volatile radiofrequency switching technologies

Collective octahedral tilting in ultrathin Ruddlesden–Popper perovskite under terahertz light

Perovskites have been applied in a wide range of fields such as solar cells and nonvolatile memories due to their multiferroic nature and excellent photo-electric conversion capabilities. Recently, two-dimensional perovskites with a few atomic layers have been successfully synthesized, attracting significant attention for potential applications. In this work, we perform first-principles calculations to investigate an ultrathin prototypical Ruddlesden−Popper phase, Bi2FeO4, with its thickness down to one unit cell. We show that this compound could exist in two (meta-)stable octahedral tilting phases, belonging to P21/c and C2/m space groups, respectively. Using the optomechanical theory, we suggest that reversible and nonvolatile phase switching can be triggered using nondestructive terahertz light. In addition, the two phases show distinct optical reflectance spectrum in the visible light range, which can be used as an optical probe for phase transformation. This enables both “write” and “read” in an all-optical route.

Giant tunnel resistance effect in (SrTiO3)2/(BaTiO3)4/(CaTiO3)2 asymmetric superlattice with enhanced polarization.

In this work, we report the effectively enhanced tunneling electroresistance effect in Au/(SrTiO3)2/(BaTiO3)4/(CaTiO3)2/Nb:SrTiO3 superlattice ferroelectric tunnel junction (FTJ). The stable polarization switching and enhanced ferroelectricity were achieved in the nanoscale thickness high-quality epitaxial superlattice. A high ON/OFF current ratio of more than 105 was obtained at room temperature, which is an order of magnitude larger than the BaTiO3 FTJ with the same structure. Nonvolatile resistance switching controlled by nonvolatile polarization switching was observed in the superlattice FTJ. Driven by increased polarization and intrinsic asymmetric ferroelectricity, a highly asymmetric depolarization field is generated compared with the Au/BaTiO3/Nb:SrTiO3 FTJ, resulting in an enhanced tunneling electroresistance effect. These results provide a potential way to construct FTJ memory devices by constructing asymmetric three-component ferroelectric superlattices.

Optical and structural characterizations of NiO-doped PMMA films and fabrication of Ag/NiO-doped PMMA/n-Si/AuSb for analogue-digital switching applications

Herein, the authors report the NiO-doped PMMA nanocomposites fabrication process with different Ni concentrations of 0.001–10 wt% on pre-cleaned glass, ITO, and n-type Si via spin-coating technique. X-ray diffraction (XRD) was used to analyze the crystal structure of NiO in powder form and the NiO-doped PMMA nanocomposite thin films. The Rietveld refinement method was used to analyze the manufactured NiO's powder-form structural characteristics. The analysis data revealed a single phase of NiO nanoparticles with face-centred cubic of Fm-3m space group. The average crystallites' mean size and the microstrain value were determined based on the Williamson-Hall model and were equal to 32.47 ± 1.210 nm and 5 × 10−5, respectively. The FESEM micrographs illustrate dispersed cubic-shaped NiO grains in the PMMA matrix. The estimated energy gaps and the width of the localized energy states (Urbach tails) are plotted against the photon energy. The estimated energy gap, EgOp is increasing from 3.649 ± 0.003 eV to 3.782 ± 0.005 eV with increasing the NiO nanoparticles' doping ratio in the PMMA as a host insulating polymer. The fabricated Ag/NiO-PMMA (S4)/n-Si/AuSb heterojunction device revealed two different (HRS and LRS) resistance-switching behaviours. For second and third electrical (I–V) paths, the extracted magnitudes of the ideality factor are 2.397 ± 0.006 and 2.691 ± 0.003 and the calculated barrier height are 0.727 ± 0.004 and 0.886 ± 0.005, respectively. The interfacial electronics states NSS increasing from 6.58 × 1012 to 3.7 × 1014 cm−2.eV−1 and 3.48 × 1013 to 3.65 × 1014 cm−2 .eV−1 for the 2nd HRS path and 3rd LRS, respectively. The investigated hysteresis loop and the variation in interfacial electronics states reveal that the NiO-PMMA nanocomposite may be promising in non-volatile memory and electrical switching electronic devices.