Future Information Storage Research Articles

DNA Bloom Filter enables anti-contamination and file version control for DNA-based data storage.

DNA storage is one of the most promising ways for future information storage due to its high data storage density, durable storage time and low maintenance cost. However, errors are inevitable during synthesizing, storing and sequencing. Currently, many error correction algorithms have been developed to ensure accurate information retrieval, but they will decrease storage density or increase computing complexity. Here, we apply the Bloom Filter, a space-efficient probabilistic data structure, to DNA storage to achieve the anti-error, or anti-contamination function. This method only needs the original correct DNA sequences (referred to as target sequences) to produce a corresponding data structure, which will filter out almost all the incorrect sequences (referred to as non-target sequences) during sequencing data analysis. Experimental results demonstrate the universal and efficient filtering capabilities of our method. Furthermore, we employ the Counting Bloom Filter to achieve the file version control function, which significantly reduces synthesis costs when modifying DNA-form files. To achieve cost-efficient file version control function, a modified system based on yin-yang codec is developed.

Understanding Antiferromagnetic Coupling in Lead-Free Halide Double Perovskite Semiconductors.

Solution-processable semiconductors with antiferromagnetic (AFM) order are attractive for future spintronics and information storage technology. Halide perovskites containing magnetic ions have emerged as multifunctional materials, demonstrating a cross-link between structural, optical, electrical, and magnetic properties. However, stable optoelectronic halide perovskites that are antiferromagnetic remain sparse, and the critical design rules to optimize magnetic coupling still must be developed. Here, we combine the complementary magnetometry and electron-spin-resonance experiments, together with first-principles calculations to study the antiferromagnetic coupling in stable Cs2(Ag:Na)FeCl6 bulk semiconductor alloys grown by the hydrothermal method. We show the importance of nonmagnetic monovalence ions at the BI site (Na/Ag) in facilitating the superexchange interaction via orbital hybridization, offering the tunability of the Curie-Weiss parameters between -27 and -210 K, with a potential to promote magnetic frustration via alloying the nonmagnetic BI site (Ag:Na ratio). Combining our experimental evidence with first-principles calculations, we draw a cohesive picture of the material design for B-site-ordered antiferromagnetic halide double perovskites.

A Strategy for Enhancing Perpendicular Magnetic Anisotropy in Yttrium Iron Garnet Films.

In future information storage and processing, magnonics is one of the most promising candidates to replace traditional microelectronics. Yttrium iron garnet (YIG) films with perpendicular magnetic anisotropy (PMA) have aroused widespread interest in magnonics. Obtaining strong PMA in a thick YIG film with a small lattice mismatch (η) has been fascinating but challenging. Here, a novel strategy is proposed to reduce the required minimum strain value for producing PMA and increase the maximum thickness for maintaining PMA in YIG films by slight oxygen deficiency. Strong PMA is achieved in the YIG film with an η of only 0.4% and a film thickness up to 60nm, representing the strongest PMA for such a small η reported so far. Combining transmission electron microscopy analyses, magnetic measurements, and a theoretical model, it is demonstrated that the enhancement of PMA physically originates from the reduction of saturation magnetization and the increase of magnetostriction coefficient induced by oxygen deficiency. The Gilbert damping values of the 60-nm-thick YIG films with PMA are on the order of 10-4. This strategy improves the flexibility for the practical applications of YIG-based magnonic devices and provides promising insights for the theoretical understanding and the experimental enhancement of PMA in garnet films.

Single-molecule non-volatile memories: an overview and future perspectives

A single-molecule non-volatile memory is a crucial component of future nanoscale information storage. This article provides an overview of the design, mechanism and prospects of single-molecule non-volatile memories.

Simulation of the resistance switching performance and synaptic behavior of TiO2-based RRAM devices with CoFe2O4 insertion layers.

The electrothermal coupling model of Pt/CoFe2O4/TiO2/TiN devices was established to study their resistive switching characteristics and basic biological synaptic properties in our research. The processes of set and reset are simulated, and the distribution of the temperature, the electric field and the concentration of oxygen vacancies in the dielectric layer are obtained. The switching performance of the TiO2-based device is significantly improved after the CoFe2O4 layer is inserted, with the switching voltage, working current and power consumption being reduced, while the switching ratio is increased. By changing the thermal conductivity of the top electrode, the rupture position of the conductive filament can be controlled. The I-V characteristics of the Pt/CoFe2O4/TiO2/TiN device during the reset and set processes are fitted linearly in logarithmic coordinates, and the ohmic conduction mechanism or the space-limited charge conduction mechanism is mainly satisfied in the high and low resistance states. Finally, the application of dual-layer devices on biological synapses is studied, and the basic biological characteristics of enhancement, inhibition and paired pulse promotion are simulated successfully. In addition, the redox reaction induced by oxygen vacancy migration also promotes the formation and rupture of the conductive filament. Results of the study show this ferrite material as an insertion layer in a resistive random-access memory structure that offers potential for future information storage and bioneuromorphic computation devices.

Spin-phonon coupling in two-dimensional magnetic materials

Recently, two-dimensional magnetic materials (2DMMs) have become a focused research direction in a broad range of two-dimensional materials, due to their underlying significance in fundamental research, as well as in technologically relevant applications for future spintronics, magnonics, quantum information and data storage. The rich toolbox of 2DMMs and their diverse tunability have enabled the unprecedented research concerning the two-dimensional magnetic order down to single atomic layer of materials, much beyond the classical thin film magnetism, showing an extremely promising venue towards electronics, magneto-optics and photonics. Among various degrees of freedoms, the interaction between spin and phonon (i.e., quanta of lattice vibration), hence the so-called spin-phonon coupling, serves as an important tuning knob to explore the two-dimensional magnetism, create new types of quasiparticles and control the magnetic order. This review article overviews the latestdevelopments in spin-phonon coupling investigations in 2DMMs. Various techniquesutilizing spin-phononcoupling to investigate two-dimensional magnetism are discussed.Recent progresses in tuning two-dimensional magnetic order based on spin phonon-coupling are also summarized, with a focus to understand the new functionalities. Furthermore, device developments and concepts based on spin-phonon coupling are briefly discussed. This review will provide our perspectives on the existing challenges and future directions in spin-phonon coupling research in 2DMMs and their functional devices.

Ground-state bistability of cold atoms in a cavity

We experimentally demonstrate an optical bistability between two hyperfine ground states of trapped, cold atoms, using a single mode of an optical resonator in the collective strong coupling regime. Whereas in the familiar case, the bistable region is created through atomic saturation, we report an effect between states of high quantum purity, which is essential for future information storage. The source of nonlinearity is a cavity-assisted pumping between ground states of the atoms and the stability depends on the intensity of two driving lasers. We interpret the phenomenon in terms of the recent paradigm of first-order, driven-dissipative phase transitions, where the transmitted and driving fields are understood as the order and control parameters, respectively. A semiclassical mean-field theory is invoked to describe the nontrivial two-dimensional phase diagram arising from the competition of the two drive. The saturation-induced bistability is recovered for infinite drive in one of the controls. The order of the transition is confirmed experimentally by hysteresis in the order parameter when either of the two control parameters is swept repeatedly across the bistability region.

Rich topological spin textures in single-phase and core-shell magnetic nanodisks

Magnetic skyrmions have potential applications in future high-density information storage devices due to their small size, topologically protected structure, and ultralow energy consumption. Here, we use a variational method to study rich topological spin textures in magnetic nanodisks, including skyrmions and skyrmionlike objects. The existence of skyrmions and $k\ensuremath{\pi}$-skyrmions in a single-phase nanodisk and a disk with a core-shell structure is investigated theoretically, where the phase diagrams of possible spin states are obtained for various Dzyaloshinskii-Moriya interaction (DMI) constants and disk dimeters. Our calculations suggest that skyrmions can be generated spontaneously in a core-shell nanodisk. We also study the transitions of spin textures in the nanodisk induced by spin currents. This paper may provide guidelines for experimental realization of different topological spin textures in nanodisks with certain DMIs. The simple two-dimensional analytical method used in this paper can be used to study the magnetic phase diagrams of thin films with interface-induced DMIs.

Ultrathin high-temperature ferromagnetic rare-earth films: GdScGe and GdScSi monolayers

Two-dimensional (2D) ferromagnetism with robust room-temperature ferromagnetism has sparked intense interest for future miniature information storage devices. However, most 2D ferromagnetic materials have a low Curie temperature. Here, by using density functional theory, two rare-earth monolayers, the GdScSi monolayer and the GdScGe monolayer, were predicted, in which these two monolayers exhibit ferromagnetic orders with large magnetic moments of approximately 7 μB/Gd. Monte Carlo simulations predict Curie temperatures of approximately 470 K and 495 K for the 2D GdScSi monolayer and the GdScGe monolayer, respectively. The spin band calculations show that they are metal. In addition, these two monolayers exhibit dynamical, mechanical, and thermal stabilities. The combination of these novel magnetic properties makes these 2D ferromagnetic crystals promising candidates for high-efficiency spintronic applications.

Two-dimensional Janus monolayers with tunable electronic and magnetic properties

In the post graphene era, the discovery of magnetism in two-dimensional (2D) intrinsic nanomagnets has opened up exciting possibilities for low-dimensional spintronics. In this article, we have reported three new 2D Janus nanomagnets VBrCl2, VBrI2, and VClBrI for the first time. First-principles based density functional theory calculations reveal that these monolayers are intrinsically magnetic with indirect band gap semiconducting properties and further the magnetic and electronic properties of these monolayers are enhanced with the application of biaxial strain and electric field. We observe interesting electronic and magnetic phase transitions, tunable band gap, and supreme enhancement of the Curie temperature (~ 686%). Large magnetic anisotropic energy (MAE) with high magnetic moment and tunable band gap property make these Janus materials useful candidates for future information storage, optoelectronics, and 2D spin circuit development.

Elimination of the skyrmion Hall effect by tuning perpendicular magnetic anisotropy and spin polarization angle

The skyrmion Hall effect has been regarded as a critical issue in skyrmion future applications, which indicates that it causes skyrmions to deviate from the direction of the driving force and leads to the destruction of skyrmion at the sample edge. In the meanwhile, perpendicular magnetic anisotropy is a promising method to manipulate the skyrmion motion by adding a material with high crystalline anisotropy into an existing material. It has been also investigated that spin polarization angles also have an influence on the skyrmion motion directions. Here, we statistically study a bilayer nanostructure, where the skyrmion Hall effect would be eliminated by modifying perpendicular magnetic anisotropy coefficients and spin polarization angles. Our results may provide a useful method for the design of skyrmion based spintronics devices without skyrmion Hall effect, to meet the need for future high-density information storage applications.

Electrically and Magnetically Tunable Valley Polarization in Monolayer MoSe2 Proximitized by a 2D Ferromagnetic Semiconductor

AbstractThe emergence of atomically thin valleytronic semiconductors and 2D ferromagnetic materials is opening up new technological avenues for future information storage and processing. A key fundamental challenge is to identify physical knobs that may effectively manipulate the spin‐valley polarization, preferably in the device context. Here, a novel spin functional device that exhibits both electrical and magnetic tunability is fabricated, by contacting a monolayer MoSe2 with a 2D ferromagnetic semiconductor Cr2Ge2Te6. Remarkably, the valley‐polarization of MoSe2 is found to be controlled by a back‐gate voltage with an appreciably enlarged valley splitting rate. At fixed gate voltages, the valley‐polarization exhibits magnetic‐field and temperature dependence that corroborates well with the intrinsic magnetic properties of Cr2Ge2Te6, pointing to the impact of magnetic exchange interactions. Due to the interfacial arrangement, the charge‐carrying trion photoemission predominates in the devices, which may be exploited to enable drift‐based spin‐optoelectronic devices. These results provide new insights into valley‐polarization manipulation in transition metal dichalcogenides by means of ferromagnetic semiconductor proximitizing and represent an important step forward in devising field‐controlled 2D magneto‐optoelectronic devices.

Electronic synaptic plasticity and analog switching characteristics in Pt/TiOx/AlOx/AlTaON/TaN multilayer RRAM for artificial synapses

In this work, electronic synaptic plasticity and analog bipolar switching behavior by using a Pt/TiOx/AlOx/AlTaON/TaN multilayer resistive random-access memory (RRAM) device were examined. By using high-resolution transmission electron microscopy (HRTEM), the oxidation–reduction reaction occurs between the Ti buffer layer and the high-k Al2O3 layer at the top interface, and the high-k Al2O3 layer and the TaN bottom electrode at the bottom interface, resulting in the formation of the Pt/TiOx/AlOx/AlTaON/TaN multilayer RRAM structure. According to X-ray photoelectron spectroscopy (XPS) studies, different proportions of oxygen vacancies in TiOx/AlOx/AlTaON multilayer film play a key role in increasing RS properties uniformity. This multilayer structure-based RRAM device exhibits a stable RS behavior with a very large on/off resistance window (∼104), excellent durability (500 DC endurance cycles), and 104 s retention period with virtuous uniformity during the cycling operation. Furthermore, the device mean value (μ) set-and reset-voltage is −2.82 V, and +1.5 V, resulting in a low-operating voltage that is beneficial for neuromorphic systems. Besides, by adjusting the reset voltage, the device achieved a progressive transition from the low resistance state (LRS) to the high resistance state (HRS). To develop the artificial neural networks, basic biological properties such as potentiation, depression, and paired-pulse facilitation were efficiently mimicked. Ohmic conduction in the LRS and Schottky emission in the HRS are the two types of current transport conduction mechanisms. The analog bipolar switching behavior is governed by the redox reaction, which promotes the formation and rupture of oxygen vacancy-based conical shape conductive filaments. These findings show that multilayer RRAM devices have the potential to be used for future information storage and neuromorphic computing of artificial synapses.

Monolayer CeI2 : An intrinsic room-temperature ferrovalley semiconductor

Two-dimensional ferrovalley semiconductors with robust room-temperature ferromagnetism and sizable valley polarization hold great prospects for future miniature information storage devices. As a new member of the ferroic family, however, such ferrovalley materials have rarely been reported. By first-principles calculations, we identify that monolayer $\mathrm{Ce}{\mathrm{I}}_{\text{2}}$ is an intrinsic ferromagnetic semiconductor and exhibits excellent ambient stability, strong easy in-plane magnetocrystalline anisotropy, and a high magnetic transition temperature up to 374 K. The ferromagnetism is found to arise from the hybridization of Ce-$4f/5d$ and I-$5p$ orbitals. When monolayer $\mathrm{Ce}{\mathrm{I}}_{\text{2}}$ is magnetized toward the off-plane $z$ direction, a spontaneous valley polarization as large as 208 meV in the top valence band can be achieved due to the simultaneous breaking of both inversion symmetry and time-reversal symmetry, which is further verified by the perturbation theory of spin-orbital coupling. Also, the anomalous valley Hall effect can be observed under an in-plane electrical field due to the robust valley-contrasting Berry curvature. Overall, the combination of intrinsic semiconducting ferromagnetism and spontaneous valley polarization renders monolayer $\mathrm{Ce}{\mathrm{I}}_{\text{2}}$ a compelling room-temperature ferrovalley semiconductor for potential applications in nanoscale spintronics and valleytronics.

Reliable analog resistive switching behaviors achieved using memristive devices in AlO x /HfO x bilayer structure for neuromorphic systems

Human brain synaptic memory simulation based on resistive random access memory (RRAM) has enormous potential to replace the traditional von Neumann digital computer thanks to several advantages, including its simple structure, its high-density integration, and its capabilities regarding information storage and neuromorphic computing. Herein, the reliable resistive switching (RS) behaviors of RRAM are demonstrated by engineering the AlO x /HfO x bilayer structure. This allows for uniform multibit information storage. Further, the analog switching behaviors are capable of imitating several synaptic learning functions, including learning experience behaviors, short-term plasticity, long-term plasticity transition, and spike-timing-dependent plasticity (STDP). In addition, the memristor based on STDP learning rules is implemented in image pattern recognition. These results may show the potential of HfO x -based memristors for future information storage and neuromorphic computing applications.

Enhanced ferroelectric and piezoelectric properties of BCT-BZT at the morphotropic phase boundary driven by the coexistence of phases with different symmetries

The discovery of lead-free piezoelectric materials is crucial for future information and energy storage applications. Enhanced piezoelectric and other physical properties are commonly observed near the morphotropic phase boundary (MPB) composition of ferroelectric solid solutions. The $(1\ensuremath{-}x)\mathrm{Ba}({\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}){\mathrm{O}}_{3}\text{\ensuremath{-}}x({\mathrm{Ba}}_{0.7}{\mathrm{Ca}}_{0.3}){\mathrm{TiO}}_{3}$ $(\mathrm{BZT}\text{\ensuremath{-}}x\mathrm{BCT})$ system exhibits a large electromechanical response around its MPB region at $x=0.5$. We report experimental and theoretical results of $\mathrm{BZT}\text{\ensuremath{-}}x\mathrm{BCT}$ over a wide composition range $(0.3\ensuremath{\le}x\ensuremath{\le}1.0)$. X-ray diffraction and Raman spectroscopy studies indicate a composition-induced structural phase transition from a rhombohedral $(R3m)$ phase at $x\ensuremath{\le}0.4$ to a tetragonal $(P4mm)$ phase at $x\ensuremath{\ge}0.6$ through a multiphase coexistence region at 0.45 \ensuremath{\le} $x\ensuremath{\le}0.55$ involving orthorhombic + tetragonal (Amm2 + $P4mm$) phases. First-principles calculations elucidate the phase competition in the coexistence region. The critical composition $(x=0.5)$ displays enhanced dielectric, ferroelectric, and piezoelectric properties, where notably ${d}_{33}\ensuremath{\sim}320$ pC/N. This paper provides clear evidence of Amm2 + $P4mm$ crystallographic phases in the MPB region, which is responsible for the improved functional properties.

Transcription and logic operations of magnetic skyrmions in bilayer cross structures

Magnetic skyrmions are potential building blocks for future information storage and computing devices. Here, we computationally study the skyrmion dynamics in a cross structure made of two ferromagnetic nanotracks. We show that by controlling the skyrmion motion in the cross structure using spin currents, it is possible to realize the transcription of skyrmion at the intersection of the cross structure at certain conditions. Based on the transcription of skyrmion, we computationally demonstrate the AND, OR and NOT logical gates using the cross structures with modified geometries and appropriate magnetic parameters. Our results may provide guidelines to design future three-dimensional spintronics devices based on magnetic skyrmions.

Multibit non-volatile memory based on WS2 transistor with engineered gate stack

In this work, a prototype of a charge-trapping memory device based on two-dimensional WS2 has been fabricated with an engineered gate stack for multilevel non-volatile memory application. A Si/SiO2/ITO/Al2O3/Ta2O5/Al2O3 stack has been successfully integrated with optimized layer thicknesses for enhanced gate control over the WS2 channel and memory performance. The memory cells exhibited a sufficient memory window, fast programming and erasing speed, and excellent memory retention and endurance. Moreover, stable and discrete memory states have been achieved at small gate voltages. Such excellent memory characteristics originated from the intrinsic properties of the atomically thin WS2 material and the engineered gate stack with clean and robust interfaces. The better thermal stability, higher permittivity, deeper trap level, and relatively smaller bandgap of the Ta2O5 dielectric than other commonly used dielectrics such as SiO2 and Al2O3 also contribute to the memory reliability, which is very attractive for future information and data storage applications.

Enhanced performance and reduction in operating voltage of TiO2 thin film based resistive switching memory under optical stimulus

Resistive switching memory devices are emerging class of non-volatile-memories and have shown outstanding device performance originates from the migration of oxygen vacancies. Research efforts are made to enhance the resistive switching behavior of devices using electrical and thermal stimuli, for example. Here we report optically modulated resistive switching behavior in Pt/TiO2/Al structure at low operating voltages. Highly stable unipolar resistive switching behavior with long retention of the resistance states (in the order of 104 min) and stable endurance (for > 300 cycles) is reported. Interestingly, the operating voltages of structure were observed to shift towards lower voltage side under optical illumination, which indicates that photo generated charge carriers play an important role. The present finding demonstrates the possible utilization of photo-responsive materials in manufacturing non-volatile memory device for future high-performance information storage and computing applications.

Reversible upconversion modulation in new photochromic SrBi2Nb2O9 based ceramics for optical storage and anti-counterfeiting applications

The manipulation of luminescence properties of upconversion (UC) materials from micro to macro aspects is of vital importance for disclosing new physical phenomena and expanding the range of applications. In this work, a novel class of SrBi2Nb2O9 (SBN)-based inorganic photochromic (PC) phosphors was synthesized, which exhibited intense susceptibility to visible light irradiation. Large reversible UC modulation ability upon PC effect was realized. Besides, the regulation of UC luminescence was discovered to strongly rely on the irradiation time and heating processes. The mechanisms connected to the UC luminescence, PC effect, and UC manipulation were illustrated. These results demonstrated that SBN-based samples owing high reversible manipulation ratio, fast response, low heating temperature, and excellent reproducibility can be employed as a type of ideal optical medium for future information storage device. In addition, based on the reversible behavior of photochromism, the application of the SBN-based ceramic as an anti-counterfeiting agent was also depicted.