Memory Storage Devices Research Articles

Origami-based tunable truss structures for non-volatile mechanical memory operation

Origami has recently received significant interest from the scientific community as a method for designing building blocks to construct metamaterials. However, the primary focus has been placed on their kinematic applications by leveraging the compactness and auxeticity of planar origami platforms. Here, we present volumetric origami cells—specifically triangulated cylindrical origami (TCO)—with tunable stability and stiffness, and demonstrate their feasibility as non-volatile mechanical memory storage devices. We show that a pair of TCO cells can develop a double-well potential to store bit information. What makes this origami-based approach more appealing is the realization of two-bit mechanical memory, in which two pairs of TCO cells are interconnected and one pair acts as a control for the other pair. By assembling TCO-based truss structures, we experimentally verify the tunable nature of the TCO units and demonstrate the operation of purely mechanical one- and two-bit memory storage prototypes.

Low‐Power Nonvolatile Charge Storage Memory Based on MoS2 and an Ultrathin Polymer Tunneling Dielectric

AbstractLow‐power, nonvolatile memory is an essential electronic component to store and process the unprecedented data flood arising from the oncoming Internet of Things era. Molybdenum disulfide (MoS2) is a 2D material that is increasingly regarded as a promising semiconductor material in electronic device applications because of its unique physical characteristics. However, dielectric formation of an ultrathin low‐k tunneling on the dangling bond‐free surface of MoS2 is a challenging task. Here, MoS2‐based low‐power nonvolatile charge storage memory devices are reported with a poly(1,3,5‐trimethyl‐1,3,5‐trivinyl cyclotrisiloxane) (pV3D3) tunneling dielectric layer formed via a solvent‐free initiated chemical vapor deposition (iCVD) process. The surface‐growing polymerization and low‐temperature nature of the iCVD process enable the conformal growing of low‐k (≈2.2) pV3D3 insulating films on MoS2. The fabricated memory devices exhibit a tunable memory window with high on/off ratio (≈106), excellent retention times of 105 s with an extrapolated time of possibly years, and an excellent cycling endurance of more than 103 cycles, which are much higher than those reported previously for MoS2‐based memory devices. By leveraging the inherent flexibility of both MoS2 and polymer dielectric films, this research presents an important milestone in the development of low‐power flexible nonvolatile memory devices.

Using persistent photoconductivity to write a low-resistance path in SrTiO3

Materials with persistent photoconductivity (PPC) experience an increase in conductivity upon exposure to light that persists after the light is turned off. Although researchers have shown that this phenomenon could be exploited for novel memory storage devices, low temperatures (below 180 K) were required. In the present work, two-point resistance measurements were performed on annealed strontium titanate (SrTiO3, or STO) single crystals at room temperature. After illumination with sub-gap light, the resistance decreased by three orders of magnitude. This markedly enhanced conductivity persisted for several days in the dark. Results from IR spectroscopy, electrical measurements, and exposure to a 405 nm laser suggest that contact resistance plays an important role. The laser was then used as an “optical pen” to write a low-resistance path between two contacts, demonstrating the feasibility of optically defined, transparent electronics.

Wafer-scale fabrication of metal nanoring and nanocrescent arrays from nanoimprinted nanopillar arrays

An approach was presented to fabricate wafer-scale nanoring structures based on nanopillar array templates fabricated by nanoimprint lithography. This fabrication method combined UV-curing nanolithography technology, metal deposition, and an etching process, which made it possible to tune the geometric properties of nanorings: height, diameter, and linewidth for various materials, such as Au and Ni. Nanoring arrays showed potential applications in many fields, including memory storage, biosensing, and optical devices. The optical measurement of Au nanorings (d=380 nm) showed its strong transmission resonances at the wavelength of 2.1 μm. A modified version of this fabrication method by depositing Ni in a controlled angle as a sacrificial layer was also utilized to create nanocrescent arrays. This modified method could easily tune the width of crescents through the nickel deposition angles and nanopillar template heights. The large-area gold nanocrescent arrays showed strong polarization-dependent transmission bands. Plasmonic crescent structures were expected to apply in infrared metamaterial and chemical sensing.

A computational study of cyclic thermal response of shape memory alloy thin-film island structures

With a view toward contributing to the state of the art in the research on shape memory alloy memory storage devices, the thermal response of a shape memory alloy (SMA) thin film during a complete cycle of heating and cooling is computationally addressed in this communication. The ultimate objective is to provide a better understanding of shape memory alloys within the context of the characteristics of thermally activated phase-transforming materials as candidate materials for memory devices. In this study, the effect of the current density, thickness of the SMA thin film, convection and boundary conditions on the transformation of the SMA thin film are investigated. In particular, we study the effect of pulse heating as that is important for memory devices. A comparison is made between the cyclic response time of a an SMA unit cell and an Ovonic unit memory (OUM) cell. The total cycle time for the SMA cell and the OUM cell is 0.7 and 60 ns, respectively. The total energy consumption per cycle for the SMA cell and the OUM cell is 0.441 and 37.8 pJ, respectively. While the response of the SMA cell is almost two orders of magnitude better than the OUM cell, we want to strike a cautionary note that the results for the SMA cell are computational and those for the OUM cell are experimental in nature. Regardless, we hope that the outcomes for the SMA cell will provide some motivation for research in SMA-based memory devices.

Synthesis of Self Nitrogen/Phosphorus Doped Carbon Derived from Pea Protein As an Efficient Electrode Material for Supercapacitors

Supercapacitors are energy storage devices that have many applications from memory storage devices, vehicle power supplies, micro sensors and so on. Recently, the electrode material of supercapacitors have been manufactured from fossil fuels which have many concern for depletion therefore, there is urgent to find low cost, eco-friendly and advance carbon electrode materials. In this context, the development of nitrogen-doped porous activated carbons from biomass is of significance for electrode materials. Herein, we report a simple route to prepare phosphorons/nitrogen-doped porous carbon derived from pea protein via hydrothermal carbonization (HTC) and the post-annealing treatment. The surface, textural and morphological properties of synthesized materials were investigated by SEM, XPS, Raman, FTIR and surface area analyzer. A series of mesoporous carbon up to 7.6 N and 2.2 wt. % P along with high the BET surface were synthesized successfully. The obtained materials depicts graphitic carbon particles. Electrochemical properties of the prepared materials were analyzed by cyclic voltammetry (CV), charge-discharge (CD), electrochemical impedance spectroscopy (EIS), KOH and H2SO4 electrolyte solution. The PGC-700 shows outstanding capacitive performance (299 F g-1 at 1 A g-1) , good rate capacitive , and excellent cycling stability due to the synergistic effect of N, P-doped species. This work opens up a new way to prepare advance N/P-doped carbon materials with tailored properties.

Study of aluminium-modified Ge2Sb2Te5 thin films for the applicability as phase-change storage device material

ABSTRACTElectrical and optical studies have been carried out on aluminium-modified Ge2Sb2Te5 thin films to check its applicability as an active material in optical and electrical memory storage devices. Five polycrystalline bulk samples were prepared with compositions: Alx(Ge2Sb2Te5)1−x; x = 0, 0.08, 0.14, 0.21, 0.25. Amorphous thin films were deposited from the polycrystalline bulk by thermal evaporation. Temperature-dependent resistance shows the increase in crystallization temperature of Ge–Sb–Te films on aluminium addition. Activation energy for conduction, conductivity, optical band gap, coefficient of refraction and extinction coefficient are studied with respect to Al content in both amorphous and crystalline phases of Ge–Sb–Te alloy films.

Resistance of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 under high voltage microsecond pulse induced breakdown

Ferroelectric ceramics have been widely used in lots of fields, such as mechanical-electric transducer, ferroelectric memory, and energy storage devices. The dielectric breakdown process of ferroelectric ceramic has received much attention for years, due to the fact that this issue is critical in many electrical applications. Though great efforts have been made, the mechanism of dielectric breakdown is still under debate. The reason is that the electrical breakdown is a complex process related to electrical, thermal, and light effects. In the present work, we investigate the breakdown process of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3(PZT95/5) ceramic, which is a kind of typical ferroelectric ceramic working in the high voltage environments. The high voltage pulse generator is used in the breakdown experiments to apply a square pulsed voltage with an amplitude of 10 kV and a width of 7 s. The resistivity change in the breakdown process is recorded by the high-frequency oscillograph in nano-second. The results show that there are two different breakdown types for our sample, i.e. body-breakdown and flashover. To better understand the breakdown mechanism of the PZT95/5 ceramic, the formation of the conductive channel in ceramic in the process is investigated by comparing the resistivity development in body-breakdown and flashover processes. The development of the conductive channel formation can be divided into three steps in body-breakdown. In the first step that lasts for the first 40 ns of breakdown, the conductive channel starts forming, with the equivalent resistance sharply decreasing to about 105 in the mean time. Then, i.e. in the second step, conductive path grows into a stable one with the equivalent resistance decreasing to the magneitude of about 102 . The resistance decreases slowly to about 130 in the third step, which means that the conductive channel is completely formed. The channel formation of flashover can also be divided into three steps. The first step is similar to that of body-breakdown, with the equivalent resistance decreasing to about 105 in about 40 ns. In the second step of flashover, the conductive path keeps growing into a stable one with the equivalent resistance decreasing to 102 , but with a different resistance changing rate from that in body-breakdown, and the resistance decreases slowly to about 20 in the end. Different behavior between the body-breakdown and the surface flashover can be explained by different carrier densities on the conductive paths in the two breakdown processes. In the body-breakdown, the carrier density in the conductive channel is higher than that in the surface flashover, which improves the electron transfer and reduces the resistance. This may explain the reason why the channel formation in body-breakdown is faster than in flashover. This study is helpful for further materials design and applications.

Structural, magnetic and spectral properties of Gd and Dy co-doped dielectrically modified Co-Ni (Ni0.4Co0.6Fe2O4) ferrites

Gadolinium (Gd) and Dysprosium (Dy) co-doped Ni-Co (Ni0.4Co0.6Fe2O4) ferrites were prepared by micro-emulsion route. X-ray diffraction (XRD) analysis indicated the development of cubic spinel structure. The lattice parameter and X-ray density were found to increase from 8.24 to 8.31Å and 5.57 to 5.91(gm/cm3) respectively as the Gd-Dy contents increased in nickel-cobalt ferrites. The crystallite size calculated from the Scherrer's formula exhibited the formation of nanocrystalline ferrites (13–26nm). Two foremost absorption bands observed in FTIR spectra within 400cm−1 (υ2) to 600cm−1 (υ1) which correspond to stretching vibrations of tetrahedral and octahedral complexes respectively. The dielectric constant (ε) and dielectric loss (tanδ) were decreased by the optimization of frequency and abrupt decrease in the low frequency region and higher values in the high frequency region were observed. The dielectric dispersion was due to rapid decrease of dielectric constant in the low frequency region. This variation of dielectric dispersion was explicated in the light of space charge polarization model of Maxwell-Wagner. The dielectric loss occurs in these ferrites due to electron hopping and defects in the dipoles. The electron hopping was possible at low frequency range but at higher frequency the dielectric loss was decreased with the decrease of electron hopping. Magnetic properties were observed by measuring M-H loops. Due to low dielectric loss and dielectric constant these materials were appropriate in the fabrication of switching and memory storage devices.

Modified Becke–Johnson potential inspired electronic and optical properties of memory storage materials PbSb2Te4 and SnSb2Te4

Electronic and optical response of two ternary isostructural phase change materials PbSb2Te4 and SnSb2Te4 are computed using the full potential linearized augmented plane wave scheme. Accuracy of electronic and optical properties was ensured by employing the modified Becke–Johnson (mBJ) exchange potential within the density functional theory. The energy bands and density of states show a band gap of 0.48 and 0.30 eV for PbSb2Te4 and SnSb2Te4, respectively. First-ever optical features, such as dielectric constants, refractive indices, reflection spectra, extinction coefficients of PbSb2Te4 and SnSb2Te4, are calculated and analyzed to explore the applicability of both the compounds in memory storage devices.

Communication between Discrete Nanostructures Triggered by Fine Tuning of an External Stimulus.

The design of molecular architectures able to transfer mass to each other is a field of extreme importance. In the present study it is shown that two especially designed covalently assembled nanostructures can interchange Cu(2+) ions upon an external OH(-) trigger. The obtained solid interfaces are of interest for signaling, communication, memory storage and optical devices.

Proceedings of the 1st International symposium on physics of data storage

Various memory technologies have emerged throughout history. Today, the discovery of new technologies and new materials over the past two decades has helped to manufacture memory devices, less bulky, less expensive, consuming less energy, but always with a larger capacity and higher speed data transfer. The international symposium ISPDS-1 has gathered researchers working on various aspects related with the problem of data storage, as Ferroics and Multiferroics, Memory storage devices, Switching phenomena, Heterojunctions and semiconductors, Energy and environment, and miscellaneous aspects. These proceedings gather abstracts of recent works in the field, presented at the symposium, dealing with chemistry, materials, devices, crystal structure, phase_diagrams, perovskite, Aurivillius, ferroelectric, ferrielectric, nanowire, Multiferroic, Flexoelectric, Magnetoelectric, Piezoresponse, Electrocaloric effect, photoelectrochemical, Resistive Switching, Magnetoelectric, nanoparticle, photovoltaic, Data_Storage, Pulsed_Laser_Deposition, PLD, lead_free_ferroelectric, solar cell, Lead_free_Materials, Nanodots, Memory, Storage, Polar nanoregions, ferroelectric_paraelectric_superlattices, ceramic, thin film, TTB, Dielectric properties, phase transition, Pb(Zn1/3Nb2/3)O3, GaFeO3, BaFe12O19, TbMnO3, PbTiO3, (Na1/2Bi1/2)TiO3, BaTiO3_BaZrO3_superlattices, Bi0.5Na0.5TiO3, Cu2S, paracetamol, ZnO, BiFeO3, ZnO thin film, Graphene, ZnO_Nanorod, mesoporous_TiO2, silicate glass, C60, C70,carbon peapods, Nematic Phase, TbMnO3, BaHfO3, Pb2KNb5O15, LiNbO3, Dielectric_measurement, impedance_spectroscopy, BaGexTi1-xO3_ceramics, SrBaBi2Nb2TiO12, PolySi-oxide, AlN, Magnetron_sputtering, photonic, polyvinylidene_fluoride_ultrathin_film, Phosphate, dechiralization_line, Nb3Al, K3Sr2LnNb10O30 (Ln = La, Gd), NaXF3, DFT, Electronic_structure, Optical properties, CsBeF3, Single-Wall_Boron_nitride_nanotubes, energy_storage, capacitors, Bi2O3

Manipulation of Nanoscale Domain Switching Using an Electron Beam with Omnidirectional Electric Field Distribution

Reversible ferroelectric domain (FD) manipulation with a high spatial resolution is critical for memory storage devices based on thin film ferroelectric materials. FD can be manipulated using techniques that apply heat, mechanical stress, or electric bias. However, these techniques have some drawbacks. Here we propose to use an electron beam with an omnidirectional electric field as a tool for erasable stable ferroelectric nanodomain manipulation. Our results suggest that local accumulation of charges contributes to the local electric field that determines domain configurations.

Nature of the Enhancement in Ferroelectric Properties by Gold Nanoparticles in Vinylidene Fluoride and Trifluoroethylene Copolymer

Ferroelectric polymers are a candidate for versatile and cheap data storage memory devices, with easy processing for a large-scale device. Easy switching and large remanent polarization of preferentially formed β-crystal dipoles in a copolymer of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)) are promising properties for versatile memory devices. At higher frequency switching, however, the remanent polarization is reduced and a high coercive field, an electric field for polarization switching is required. The addition of a small amount of nanoparticles (NPs) significantly improves these ferroelectric properties in fluoropolymers. Here, we show that the addition of NPs of gold (Au), silver (Ag), and silicon oxide (SiO2) enhanced the ferroelectric properties in P(VDF-TrFE). AuNPs significantly affected a 40% increase of the remanent polarization, 14% reduction of the coercive field, and 100% increase of the switching speed of ferroelectric polarization. The nature of these enhancements due to the addition of NPs is verified. A higher shift of the binding energy of Au (4f7/2 and 4f5/2) and an increase of the fluorine ion (F(-)) was observed in AuNP-doped P(VDF-TrFE). Strong interactions between the AuNPs and the ferroelectric backbone gave rise to the formation of the interfacial polarization, which induced the local electric field to enhance the ferroelectric properties of the increment of the remanent polarization, the reduction of the coercive field, and faster switching speed.

Feasibility of crystalline isostructural X2Sb2Te5 (X = Ge, Si) phase change materials in memory storage devices: First principles calculations

We have investigated the electronic and optical response of two isovalent non-volatile memory compounds, Ge2Sb2Te5 and Si2Sb2Te5, by employing the full potential linearized augmented plane wave method. Self consistent first-principles calculations were performed for the first time by using modified exchange potential of Becke and Johnson namely mBJ potential. Topology of energy bands and density of states of both the compounds are discussed. The optical properties such as dielectric constants, refractive indices, reflection spectra, extinction coefficients are also discussed in order to throw more light on the applicability of these compounds in memory storage devices.

System approach to the choice of capacity of a high-speed radio data link for modern Earth remote sensing spacecraft

The main principles of choosing the capacity of a high-speed radio data link for modern Earth remote sensing spacecraft are discussed in the paper. The following points are taken into account: overfilling of the onboard memory storage device; duration of communication sessions between the spacecraft and the downlink point; the required bandwidth and the reliability of the radio data link. Mathematical restrictions for the conditions of the overflow of the on-board memory storage of target information and the amount of information transmitted to the downlink points during a communication session between the spacecraft and the downlink point are specified. An expression is proposed for the estimation of radio data link capacity on the basis of the Shannon formula with account for the energy relations for satellite communication links, the required width of the passband and the probability of data transmission error. The influence of the probability of the information transmission error and the main parameters of the radio signal (the speed of protective coding and the phase deviation) on the value of high-speed radio data link capacity is analyzed. Changes in radio data link capacity in retrospect for the years immediately ahead are analyzed in accordance with the predicted value of the required volume of space information of Earth remote sensing for radio data links of different reliability.

Multistate Switches: Ruthenium Alkynyl-Dihydroazulene/Vinylheptafulvene Conjugates.

Multimode molecular switches incorporating distinct and independently addressable functional components have potential applications as advanced switches and logic gates for molecular electronics and memory storage devices. Herein, we describe the synthesis and characterization of four switches based on the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermoswitch pair functionalized with the ruthenium-based Cp*(dppe)Ru ([Ru*]) metal complex (dppe=1,2-bis(diphenylphosphino)ethane; Cp*=pentamethylcyclopentadienyl). The [Ru*]-DHA conjugates can potentially exist in six different states accessible by alternation between DHA/VHF, Ru(II) /Ru(III) , and alkynyl/vinylidene, which can be individually stimulated by using light/heat, oxidation/reduction, and acid/base. Access to the full range of states was found to be strongly dependent on the electronic communication between the metal center and the organic photoswitch in these [Ru*]-DHA conjugates. Detailed electrochemical, spectroscopic (UV/Vis, IR, NMR), and X-ray crystallographic studies indeed reveal significant electronic interactions between the two moieties. When in direct conjugation, the ruthenium metal center was found to quench the photochemical ring-opening of DHA, which in one case could be restored by protonation or oxidation, allowing conversion to the VHF state.

High-Performance Ferrite Nanoparticles through Nonaqueous Redox Phase Tuning.

From magnetic resonance imaging to cancer hyperthermia and wireless control of cell signaling, ferrite nanoparticles produced by thermal decomposition methods are ubiquitous across biomedical applications. While well-established synthetic protocols allow for precise control over the size and shape of the magnetic nanoparticles, structural defects within seemingly single-crystalline materials contribute to variability in the reported magnetic properties. We found that stabilization of metastable wüstite in commonly used hydrocarbon solvents contributed to significant cation disorder, leading to nanoparticles with poor hyperthermic efficiencies and transverse relaxivities. By introducing aromatic ethers that undergo radical decomposition upon thermolysis, the electrochemical potential of the solvent environment was tuned to favor the ferrimagnetic phase. Structural and magnetic characterization identified hallmark features of nearly defect-free ferrite nanoparticles that could not be demonstrated through postsynthesis oxidation with nearly 500% increase in the specific loss powers and transverse relaxivity times compared to similarly sized nanoparticles containing defects. The improved crystallinity of the nanoparticles enabled rapid wireless control of intracellular calcium. Our work demonstrates that redox tuning during solvent thermolysis can generate potent theranostic agents through selective phase control in ferrites and can be extended to other transition metal oxides relevant to memory and electrochemical storage devices.

Novel Framework for Efficient Data Transfer (EDT)

Memory storage devices are getting cheaper,and are coming with high capacity non-volatile in nature. The significance of high capacity flash is to have more dataand there will be frequent huge data transfer occurring between these devices to computer. It is also demand of time that there should be faster data transfer between these devices, otherwise use of high capacity feature will go in vague. Present paper will undergo the concept of Efficient Data Transfer system using which performance improvement in data transfer can be achieved based on EDT hardware and software logic throughDMA data transfer.

The tetragonal-like to rutile structural phase transition in epitaxial VO2/TiO2 (001) thick films

A controllable metal–insulator transition (MIT) of VO2 has been highly desired due to its huge potential applications in memory storage, smart windows or optical switching devices. Recently, interfacial strain engineering has been recognized as an effective approach to tuning the MIT of epitaxial VO2 films. However, the strain-involved structural evolution during the MIT process is still not clear, which prevents comprehensively understanding and utilizing interfacial strain engineering in VO2 films. In this work, we have systematically studied the epitaxial VO2 thick films grown on TiO2 (001) single crystal substrate and the structural transition at the boundary of MIT region. By using in situ temperature-dependent high-resolution x-ray diffractions, a tetragonal-like (‘T-like’) to ‘rutile’ structural phase transition is identified during the MIT process. The room-temperature crystal phase of epitaxial VO2/TiO2(001) thick film is clarified to be tetragonal-like, neither strained-rutile phase nor monoclinic phase. The calculated atomic structure of this T-like phase VO2 resembles that of the M1 phase VO2, which has been verified by their similar Raman spectra. More, the crystal lattices of the coexisted phases in the MIT region were revealed in detail. The current findings will not only show some clues on the MIT mechanism study from the structural point of view, but also favor the interface engineering assisted VO2-based devices and applications in the future.