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With the advent of the big-data era, conventional memory technologies and devices are facing enormous challenges. Resistive random access memory (RRAM) is an emerging memory technology that has aroused widespread interest for its immense potential. However, there remain some problems in resistive switching devices, such as high switching voltages, random voltages distribution, wide variation in resistance states, and poor endurance. In this work, molybdenum disulfide quantum dots are applied to resistive switching devices. The resulting devices exhibit improved performance. They have ultra-low and centralized switching voltages, uniformly distributed resistance states, good endurance, and extremely large on/off ratios. This performance optimization may derive from the convergence of electric field distribution around molybdenum disulfide quantum dots, which enhances the formation of localized conductive filaments. In this Letter, we propose an approach for improving resistive switching properties, significantly facilitating the development of data storage and related applications.

Exchange bias lies in the core of cutting-edge technologies, for instance, high-density data storage, spin valves, and high-frequency magnetic devices. As the devices with flexibility have become vital in the forefront of technology, the maintenance of exchange bias under high flexion is highly desired. This paper reports the strong exchange bias in flexible freestanding La0.7Sr0.3MnO3/BiFeO3 membranes with decent mechanical durability. The La0.7Sr0.3MnO3 layer is biased strongly by the BiFeO3 layer even in the freestanding state. At the same time, the strain is demonstrated to affect the strength of the exchange bias of the La0.7Sr0.3MnO3/BiFeO3 bilayer. Furthermore, the saturation magnetization and exchange bias field of the freestanding La0.7Sr0.3MnO3/BiFeO3 membranes are preserved well after 1000 bending cycles. Our work on freestanding membranes paves the way for manufacturing advanced flexible spintronic devices.

This work demonstrates that graphene/diamond (carbon sp2-sp3) heterojunctions can be used as multibit optoelectronic memory, where light information is stored as multilevel resistance in a nonvolatile manner. The carbon heterojunctions exhibit a large memory switching ratio of ∼104 and a retention time of >100 min, which allows for multilevel and nonvolatile data storage of optical information. The carbon heterojunctions also exhibit an apparent response to optical pulses, and the output current (conductivity of the junctions) increased linearly in response to the total number of optical pulses. Simple optical arithmetic operations such as accumulation, subtraction, and counting can be performed by using the multiple resistance states of the heterojunctions. The carbon heterojunctions have light sensing, memory, and arithmetic functions in a single device, and they are expected to pave the way for the production of innovative optical computing devices with multifunctional integration of sensing, memory, and calculation functions.

In this work, organic material-based resistive switching mechanisms were studied by using graphene oxide as the switching layer. With the insertion of a charge trapping graphene layer, the device showed good stability and good electrical bipolar switching properties, with an ON/OFF ratio about 102–103. The device gradually shifted toward complementary switching behavior while maintaining an ON/OFF ratio of ∼102 from bipolar switching behavior after a specific number of consecutive DC switching cycles with increases in the SET-RESET voltage. The conduction mechanisms for bipolar (P–F conduction) and the complementary switching were verified based on the electrical characteristics and curve fittings. Rapid increases in the injected electrons due to increased voltage in complementary switching facilitated the formation of an intermediate charge reservoir region that, in turn, enhanced performance. The device showed a retention period as high as 104 s at 85 °C and good DC endurance. The device is also capable of multi-resistance states to obtain multi-bit (4-bit) data storage, leading to high density memory realization.

We demonstrate microelectromechanical system-based flash memory (MEM-FLASH) for multinary bit storage. The MEMS switch integrated with the transistor provides the precise control of the charges on the floating gate. This maneuvering of the charges to 8 different levels provides 3-bit operation even at an elevated temperature of ∼300 °C. The key challenge in the realization of such a memory is the know-how the amount of charge to be transferred to the floating gate to alter the bit state. The charge estimation on the floating gate cannot be performed by direct probing of the device, as this will disturb the original charge values of the floating gate and thus the threshold value. Ergo, an indirect read approach is developed. Furthermore, the cantilever switch is fabricated and tested in a vacuum environment for experimental validation of the approach. The percentage variation from the theoretical to experimental approach is in the adoptable limit of 2%.

Through utilizing individual nanodots, as smallest memory units, to convert stress into readable electronic information, we report force-induced high-density data storage in the periodic nanostructure of ferroelectric polymer fabricated by nanoimprinting lithography. The nanostructure is ideal for the stress concentration and increasing the non-uniformity of strains, thus leading to strain gradients inversely proportional to the feature size. A force as low as 400 nN is applied to generate the internal electric field in response to strain gradients and switch polarization state of each memory unit. It can achieve storage density theoretically up to TB/inch2 with the up-to-date nanofabrication technology to miniaturize the unit size.

It is well known that surface-plasmon enhanced photo-electrochemical effect or photo-thermal effect of metallic particles on a semiconductor substrate or in a suspension may result in color changes. Such character could be potentially applicable to colorimetric sensors, optical filters, and data storage devices. However, usually the response time for color changes is too long to be practically applied. In this letter, we found that the response rate of color changes could be controlled by the annealing condition of the semiconductor substrate, and changes larger than 10% in spectra were observed after only 1-min exposure to light. Furthermore, such fast response was applied to realize wavelength-dependent “write” and “read” applications with high spatial resolution.

The electrical properties of amorphous-crystalline interfaces in phase change materials, which are important for rewritable optical data storage and for random access memory devices, have been investigated by surface scanning potential microscopy. Analysis of GeSb systems indicates that the surface potential of the crystalline phase is similar to 30-60 mV higher than that of the amorphous phase. This potential asymmetry is explained qualitatively by the presence of a Schottky barrier at the amorphous-crystalline interface and supported also by quantitative Schottky model calculations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3691179]

Resistive-switching memory with ultralow-power consumption is very promising technology for next-generation data storage and high-energy-efficiency neurosynaptic chips. Herein, Ta2O5−x-based multilevel memories with ultralow-power consumption and good data retention were achieved by simple Gd-doping. The introduction of a Gd ion, as an oxygen trapper, not only suppresses the generation of oxygen vacancy defects and greatly increases the Ta2O5−x resistance but also increases the oxygen-ion migration barrier. As a result, the memory cells can operate at an ultralow current of 1 μA with the extrapolated retention time of >10 years at 85 °C and the high switching speeds of 10 ns/40 ns for SET/RESET processes. The energy consumption of the device is as low as 60 fJ/bit, which is comparable to emerging ultralow-energy consumption (

We demonstrate the feasibility of ultrahigh-density probe recording in chalcogenide-based phase change media. The multilayer medium has been optimized with respect to electrical, thermal, and tribological requirements. Design of the multilayer takes into account the nonlinear dependence of the electrical properties of the phase change layer with respect to both electrical field and temperature. Memory dots as small as 15nm have been written and read repeatably. Data storage density of greater than Tbit∕in.2 density has been successfully achieved.

Multilevel molecular memory devices were proposed and demonstrated for nonvolatile data storage up to three bits (eight levels) per cell, in contrast to the standard one-bit-per-cell (two levels) technology. In the demonstration, charges were precisely placed at up to eight discrete levels in redox active molecules self-assembled on single-crystal semiconducting nanowire field-effect transistors. Gate voltage pulses and current sensing were used for writing and reading operations, respectively. Charge storage stability was tested up to retention of 600 h, as compared to the longest retention of a few hours previously reported for one-bit-per-cell molecular memories.

We report the demonstration of thermomechanical data storage in a poly(methylmethacrylate) film using a multiwalled carbon nanotube (MWCNT) tip. Indentation densities of >250 Gbits/in2 are achieved. The power efficiency of indent writing with MWCNT tips is found to be higher than that of conventional silicon tips owing to better heat transfer at the tip–polymer interface.

We study the magnetostatic interactions in planar arrays of single domain, magnetic disk nanostructures. We derive equations for the time evolution of magnetization and energy, and use these results to simulate the relaxation of these systems with a Monte-Carlo model. Our model confirms that relaxation of a one-dimensional array into one of its ground states occurs by propagating the inversion site along the line. A two-dimensional honeycomb array enters a metastable state of frustrated spiral domains due to the availability of low-energy configurational states. This model has potential application in the design of magnetic nanostructure systems for data storage and data processing applications.

We have observed a large electrical conductance switching (ON:OFF ratio=105) in single-layer sandwich structures based on organic molecules at room temperature. The switching devices showed an associated memory effect for data-storage applications. We could write or erase a state and read it for many cycles. In switching devices, the active semiconductor retained its high conducting state until a reverse voltage erased it. A high conducting state arose due to restoration of conjugation in the molecule via electroreduction. Such a high ON–OFF ratio in a single layer sandwich structure, as compared to contemporary switching devices, is due to low off-state leakage current. The concept of conjugation restoration has been verified in supramolecular structures by adding donor groups to the molecule, which resulted in increased off-state current and hence lower ON–OFF ratio. Our work set a generalized example of selecting organic molecules to obtain higher ON–OFF ratio in molecular switching devices.

Nanosized inverted domain dots in ferroelectric materials have potential applications in ultrahigh-density rewritable data storage systems. Here, a data storage system based on scanning nonlinear dielectric microscopy and thin films of ferroelectric single-crystal lithium tantalite is presented. Through domain engineering, nanosized inverted domain dots have been successfully formed at a data density of 1.50 Tbit/in.2.

The size of germanium (Ge) nanocrystals in a trilayer metal-insulator-semiconductor memory device was controlled by varying the thickness of the middle (co-sputtered Ge+SiO2) layer. From analyses using transmission electron microscopy and capacitance–voltage measurements, we deduced that both electrons and holes are most likely stored within the nanocrystals in the middle layer of the trilayer structure rather than at the interfaces of the nanocrystals with the oxide matrix.

The induced changes of the flatband voltage by the location of holes in a silicon-rich oxide (SRO) film sandwiched between two thin SiO 2 layers [used as gate dielectric in a metal-oxide-semiconductor (MOS) capacitor] can be used as the two states of a memory cell. The principle of operation is based on holes permanently trapped in the SRO layer and reversibly moved up and down, close to the metal and the semiconductor, in order to obtain the two logic states of the memory. The concept has been verified by suitable experiments on MOS structures. The device exhibits an excellent endurance behavior and, due to the low mobility of the holes at low field in the SRO layer, a much longer refresh time compared to conventional dynamic random access memory cells. © 2002 American Institute of Physics.

Electrical bistability is a phenomenon in which a device exhibits two states of different conductivities, at the same applied voltage. We report an organic electrical bistable device (OBD) comprising of a thin metal layer embedded within the organic material, as the active medium [L. P. Ma, J. Liu, and Y. Yang, US Patent Pending, (2001)]. The performance of this device makes it attractive for memory-cell type of applications. The two states of the OBD differ in their conductivity by several orders in magnitude and show remarkable stability, i.e., once the device reaches either state, it tends to remain in that state for a prolonged period of time. More importantly, the high and low conductivity states of an OBD can be precisely controlled by the application of a positive voltage pulse (to write) or a negative voltage pulse (to erase), respectively. One million writing-erasing cycles for the OBD have been tested in ambient conditions without significant device degradation. These discoveries pave the way for newer applications, such as low-cost, large-area, flexible, high-density, electrically addressable data storage devices.

A micromagnetic study on the magnetization reversal in bit patterned media (BPM) with each bit consisting of an exchange coupled composite (ECC) layer stack is presented. The simulations reveal superior magnetic properties of the combined ECC/BPM scheme, in particular for graded media, using uncorrelated distributions of magnetic anisotropy values in order to lower the switching field while keeping a high thermal stability of the media. In this study, a route for narrowing the switching field distribution of the bit array is provided as well, which is vital for the applicability of the BPM concept in magnetic data storage.

This letter discusses an alternative storage approach to conventional magnetic data storage. The approach uses a 32×32 array of scanning probe microscopes working in parallel to read and write data as small indentations in a polymer storage medium. The results have densities of 100–200 Gbit/in.2. At such densities, it is shown that well over half the array works, and at lower densities more than 80% of levers are working.

A laser light source for high-resolution near-field optics applications with an output power exceeding 1 mW (104 times the power from previous sources) and small (300 nm square to less than 50 nm square) output beam size is demonstrated. The very-small-aperture laser (VSAL) tremendously expands the range of applications possible with near-field optics and increases the signal-to-noise ratios and data rates obtained in existing applications. As an example, 250-nm-diam marks corresponding to 7.5 Gb/in.2 storage density have been recorded and read back in reflection and transmission on a rewritable phase-change disk at 24 Mb/s with a 250-nm-square aperture VSAL. VSALs potentially enable data storage densities of over 500 Gb/in.2 (up to 100 times today’s magnetic or optical storage densities).

In this letter, the resistive switching characteristics of CeO2 based memristor are investigated by utilizing an unusual, non-conventional, and a unique approach of “chronoamperometry.” This methodology provides useful insights into memristive characterization for achieving configurable device functionalities such as categorization of minimum threshold potential to prompt switching behaviour, tuneable on/off ratios with accessible multi-level data storage states, etc. Moreover, the analytical studies on carrier drift/diffusion controlled-memristor response and the estimation of time constants at various applied fixed potentials provide tangible evidence to support valence change mechanism in CeO2 based memristors.

We report a simple atomic force microscopy-based concept for a hard disk-like data storage technology. Thermomechanical writing by heating a Si cantilever in contact with a spinning polycarbonate disk has already been reported. Here the medium has been replaced with a thin polymer layer on a Si substrate, resulting in significant improvements in storage density. With this new medium, we achieve bit sizes of 10–50 nm, leading to data densities of 500 Gbit/in.2. We also demonstrate a novel high-speed and high-resolution thermal readback method, which uses the same Si cantilevers that are used in the writing process, and the capability to erase and rewrite data features repeatedly.

Memristors and memristive systems have been extensively studied for data storage and computing applications such as neuromorphic systems. To act as synapses in neuromorphic systems, the memristor needs to exhibit analog resistive switching (RS) behavior with incremental conductance change. In this study, we show that the dynamic range of the analog RS behavior can be significantly enhanced in a tantalum-oxide-based memristor. By controlling different state variables enabled by different physical effects during the RS process, the gradual filament expansion stage can be selectively enhanced without strongly affecting the abrupt filament length growth stage. Detailed physics-based modeling further verified the observed experimental effects and revealed the roles of oxygen vacancy drift and diffusion processes, and how the diffusion process can be selectively enhanced during the filament expansion stage. These findings lead to more desirable and reliable memristor behaviors for analog computing applications. Additionally, the ability to selectively control different internal physical processes demonstrated in the current study provides guidance for continued device optimization of memristor devices in general.

Pt fibers (15 μm) were coated with topological insulator Bi2Se3 nanoplates via a single mode microwave-assisted synthesis technique. With the Bi2Se3/Pt fibers, flexible memory devices were facilely assembled, and they were demonstrated to exhibit rewritable nonvolatile resistive switching characteristics of low switching voltage (−1.2 V and +0.7 V), high ON/OFF current ratio (106), and good retention (4500 s), showing the potential application in data storage. The resistive switching mechanism was analyzed on the bases of formation and rupture of conductive filaments.

The development of single-step printable holographic recording techniques can enable applications in rapid data storage, imaging, and bio-sensing. The personalized use of holography is limited due to specialist level of knowledge, time consuming recording techniques, and high-cost equipment. Here, we report a rapid and feasible in-line reflection recording strategy for printing surface holograms consisting of ink using a single pulse of a laser light within seconds. The laser interference pattern and periodicity of surface grating as a function of tilt angle are predicted by computationally and demonstrated experimentally to create 2D linear gratings and three-dimensional (3D) images. We further demonstrate the utility of our approach in creating personalized handwritten signatures and 3D images.

Fowler–Nordheim tunneling of electrons through “crested” energy barriers (with the height peak in the middle) is much more sensitive to applied voltage than that through barriers of uniform height. Calculations for trilayer barriers, with layer parameters typical for wide-band-gap semiconductors, have shown that by merely doubling the voltage, the tunnel current may be changed by more than 16 orders of magnitude. It is argued that this effect may be used for the implementation of nonvolatile random-access memories combining a few ns cycle time with a few years retention time and for ultradense electrostatic data storage.

Ultrahigh density data storage on a novel organic thin film by scanning tunneling microscope (STM) under ambient conditions is demonstrated. The material, N-(3-nitrobenzylidene)p-phenylenediamine (NBPDA), is used for preparing thin film by vacuum evaporation method. Crystalline NBPDA films with electrical bistability are obtained by this method. Recording experiment on the films is made by applying voltage pulses between the STM tip and substrate. The recorded marks are 0.7 nm in size, corresponding to a storage density of 1014 bit/cm2. Current–voltage characteristic measurement shows that the resistance of the unrecorded region of the NBPDA films is much higher than that of the recorded region. The mechanism of recording is discussed.

Recently, there have been significant advances in demonstrating the possible application of scanning probe techniques for high density data storage. While many obstacles have yet to be overcome, one of the more promising applications of such devices is for very high density read‐only disk drives. Such an application requires the means to pattern and replicate nanometer scale features over macroscopic dimensions. We have developed a technique for both mastering and replicating data patterns for use in such a device at a density 100 times that of current read‐only disks. The process consists of using electron beam lithography to write data features as small as 50 nm and a photopolymerization process to faithfully replicate the written marks.

Near‐field scanning optical microscopy (NSOM) has been utilized to study the behavior of liquid crystals at room temperature. The material, 4′‐octyl‐4‐biphenylcarbonitrile (8cb) was studied at the air–liquid interface. The NSOM probe is shown to take an active role in modifying, and subsequently reading, the liquid crystal with about 65 nm resolution. The optical modification is proven to be independent of topographic modification. Results indicate potential technological uses in data storage and displays.

Ferroelectric polymers offer the promise of low-cost and flexible electronic products. They are attractive for information storage due to their spontaneous polarization which is usually switched by electric field. Here, we demonstrate that electrical signals can be readily written on ultra-thin ferroelectric polymer films by strain gradient-induced polarization switching (flexoelectric effect). A force with magnitude as small as 64nN is enough to induce highly localized (40 nm feature size) change in the polarization states. The methodology is capable of realizing nonvolatile memory devices with miniaturized cell size and storage density of tens to hundreds Gbit per square inch.

We report novel biphotonic holographic storage of text and gratings on unoriented films of a side‐chain liquid crystalline polyester capable of high density storage and complete erasure. The holograms have a typical size of 1 mm. The recording utilizes unusual photochemistry involving azo dye molecules. We believe that this technique would have a great potential in the recording of thousands of holograms in a two‐dimensional plane, as for instance in text retrieval systems and in the fabrication of high density interconnects in optical neural networks.

This work demonstrates a cantilever based electrostatic microelectromechanical system device operating as a memory element. Volatile and non-volatile functions are engineered by manipulating molecular adhesion force through contact dimples and restoring force using the cantilever design. For non-volatile RESET operation, a method of detaching the cantilever with 3 V pulsating DC signal at 1 MHz is proposed. SET/RESET cycles are performed up to 103 times at 300 °C without any performance degradation. A writing speed of up to 0.94 μs is achieved, which is faster than conventional high temperature flash memories. With demonstrated attributes, the fabricated device offers excellent potential for harsh environment data storage applications. ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

Heat assisted magnetic recording (HAMR) has been recognized as a leading technology to increase the data storage density of hard disk drives. Dispersions in the properties of the grains comprising the magnetic medium can lead to grain-to-grain Curie temperature variations, which drastically affect the jitter in the recorded magnetic transitions and limit the data storage density capabilities in HAMR. Here we present a method to measure the switching probability of an ensemble of exchange-decoupled grains with perpendicular anisotropy subject to nanosecond heating pulses. The short heat exposure time ensures that the grains switch by reaching the Curie temperature rather than through thermal activation. The switching probability can be directly interpreted as representing the Curie temperature distribution. The method is applied to two sets of samples to reveal the sensitivity of the Curie temperature distribution to FePt HAMR media fabrication parameters. This technique is of importance to engineer suitable HAMR media capable of high density magnetic recording and for fundamental studies on sources of magnetic disorder in granular magnetic media.

A new analog memory (AM) has been demonstrated using heterojunction acoustic charge transport (HACT) technology. The initial HACT AMs had storage time capabilities of 100 μs at 25 °C. The Schottky electrode storage array had 36 memory cells, each cell holding 2 charge packets, giving a maximum signal frequency of half the Nyquist frequency. Hold voltages in the 6–8 V range were found to be adequate, and effective storage was obtained at the same dc transport current level that resulted in the best charge transport efficiency. Storage times in the millisecond range are possible with cooling.

Near‐field scanning optical microscopy (NSOM) has been used to image and record domains in thin‐film magneto‐optic (MO) materials. In the imaging mode, resolution of 30–50 nm has been consistently obtained, whereas in the recording mode, domains down to ∼60 nm have been written reproducibly. Data densities of ∼45 Gbits/in.2 have been achieved, well in excess of current magnetic or MO technologies. A brief analysis of speed and other issues indicates that the technique may represent a viable alternative to these and other methods for anticipated high density data storage needs.

The state of bistable defects in crystalline silicon such as iron-boron pairs or the boron-oxygen defect can be changed at room temperature. In this letter, we experimentally demonstrate that the chemical state of a group of defects can be changed to represent a bit of information. The state can then be read without direct contact via the intensity of the emitted band-band photoluminescence signal of the group of defects, via their impact on the carrier lifetime. The theoretical limit of the information density is then computed. The information density is shown to be low for two-dimensional storage but significant for three-dimensional data storage. Finally, we compute the maximum storage capacity as a function of the lower limit of the photoluminescence detector sensitivity.

Bacteriorhodopsin (BR) films allow write-once-read-many recording of polarization data by a two-photon-absorption (TPA) process. The optical changes in BR films induced by the TPA recording were measured and the Muller matrix of a BR film was determined. A potential application of BR films in security technology is shown. Polarization data can be angle-selective retrieved with high signal-to-noise ratio. The BR film does not only carry optical information but serves also as a linear polarizer. This enables that polarization features recorded in BR films may be retrieved by merely using polarized light from a mobile phone display.

Quantized conductance was observed in an anion-migration-based resistive switching memory cell with the structure of (Ti, Ta, W)/Ta2O5/Pt. The conductance of the cell varies stepwise in units of single atomic conductance (77.5 μS), which is responsible for the formation and annihilation of atomic scale filament built from oxygen vacancies in Ta2O5 film. The quantized conductance behavior can be modulated by voltage pulses as fast as 100 ns. The demonstration of conductance quantization in Ta2O5 based memory device would open the door for quantized multi-bit data storage of anion-migration-based resistive switching nonvolatile memories.

Vinylidene fluoride-trifluoroethylene-chlorofluoroethylene terpolymer, P(VDF-TrFE-CFE), with small amount of CFE is utilized for thin-film nonvolatile memory. Polarization switching voltage for a 50 nm-thick film can be as low as 1 V, and is well suited for integrated driving electronics. The writing-erasing procedure is completely reversible. High signal-to-noise and high capability for data storage are observed in this memory system. Polarization state of the terpolymer is rather stable, making it applicable for memory devices. Polarization switching behavior in the terpolymer can be ascribed to reduced polar domain size with respect to the P(VDF-TrFE) copolymer, and energy cost of domain wall motion during electrically polarization switching decreases.

We investigate the surface deformation in two-photon induced multi-dimensional data storage. Both experimental evidence and theoretical analysis are presented to demonstrate the surface characteristics and formation mechanism in azo-containing material. The deformation reveals strong polarization dependence and has a topographic effect on multi-dimensional encoding. Different stages of data storage process are finally discussed taking into consideration the surface deformation formation.

The periodically poled ferroelectric wafer is a two-dimensional phononic superlattice. The important applications of such a solid include ultrasonic transducers at the micro/nano-scale for low intensity ultra-sonography, ferroelectric data storage, and development of very high frequency chips for next generation communication and information technologies, and others. In this work, we show theoretically and experimentally that a ferroelectric phononic superlattice has two distinctive resonances in acousto-electric transformation. They are associated with a split acoustic mode at the boundary between the first and second acoustic Brillouin zone.

Multiferroics exhibit both ferroelectricity and ferromagnetism. The combination of ferroelectricity and ferromagnetism in single phase offers the ability to obtain four physical polarization states, i.e., two electric polarization combined with two magnetic polarization states, achieving four-state memory devices. The four-state memory devices can exponentially increase data storage capacity. In this letter, we synthesized single phase Sr3Co2Fe24O41, which exhibits ferroelectricity,ferromagnetism, and magnetoelectric coupling effect at room temperature. The as-prepared Sr3Co2Fe24O41 was used as a four-state memory prototype. The information was written by electric and magnetic fields, and read out by magnetoelectric coefficient (αE ) with the help of a small bias magnetic field.

The electrical properties of a resistive-switching memory based on a single graphene sheet suspended on a patterned indium-tin-oxide electrode pair were investigated. Current-voltage measurements on the planar device showed a large ON/OFF ratio (∼106) and excellent retention ability in ambient conditions. Data storage of the device can be realized by applying voltage bias and rewritten after simple heat treatment. Switching mechanisms for the graphene-based memory device were found to be related to the local oxidation of graphene sheet at the graphene/electrode interface.

We demonstrate an all-optical data storage and readout technique on a medium that has proved to be stable over centuries—glass containing metallic nanoparticles. Using ultra-short laser pulses to persistently change the shapes of the nanoparticles dependent of the laser polarization, well-defined local dichroism in the focal volume can be produced. The latter could be utilized for multi-bit encoding in spot sizes down to the diffraction limit, where the information can be read out very fast by wavelength- and polarization-sensitive detection of the transmitted light. The storage capacity of the proposed technique is comparable with that of blu-ray discs.

The origin of multilevel resistances of In3Sb1Te2 (IST) phase-change random access memory cell has been investigated with high-resolution transmission electron microscopy (HR-TEM). The HR-TEM indicates that the microstructure of IST in the programming volume changes from amorphous to InSb and amorphous at the first state, and InSb and InTe at the second state, and IST at the third state, which are fairly consistent with four different levels of resistance. The resistance difference between the amorphous and the IST is about four orders of magnitude.

A new method to achieve real information recording with a density above 1 Tbit∕in.(2) in ferroelectric data storage systems is proposed. In this system, data bits were written in the form of the polarization direction, and the data were read by scanning nonlinear dielectric microscopy technique. The domain-switching characteristics of the virgin and inversely prepolarized media were compared, and the conditions of the pulse voltage for writing were optimized. As a result, actual data containing 64×64 bits were recorded at an areal density of 4 Tbit∕in.(2). The bit error rate was evaluated to be 1.2×10(-2).

A nonvolatile memory device with multilayered SiCnanocrystals for long-term data storage was fabricated, and its electrical properties were analyzed. The average size and density of the SiCnanocrystals, which were formed between the tunnel and control oxide layers, were approximately 5 nm and 2 × 10 12 cm − 2 , respectively. The memory window of nonvolatile memory with the multilayer of SiCnanocrystals was about 2.5 V after program and erase voltages of ±12 V were applied for 500 ms, and then it was maintained at about 1.1 V for 10 5 s at 75 ° C . The activation energy estimated from charge losses of 25% to 50% increased from 0.03 to 0.30 eV, respectively. The charge loss could be caused by a Pool–Frenkel current of holes and electrons between the SiC quantum dots and the carrier charge traps around the SiCnanocrystals embedded in SiO 2 or the degradation effect of the tunnel oxide by stress induced leakage current.

Crystallization of Si nanostructures in free-standing Si/SiO2 superlattice films by a strongly focused laser beam is studied. The structural change is obtained in small areas of submicron sizes, which is detectable by camera photographs and by Raman scattering and transmission measurements. The obtained optical changes are stable at very high temperatures as shown by prolonged furnace annealing at 1200 °C. An approach based on silicon stress state is also presented, which allows erasing and rewriting data readable by Raman spectroscopy. These results can be used for nonvolatile data storage.

To improve the stability of organic multifunctional materials and enhance the ON/OFF ratio, a donor-π-acceptor molecule with the triphenylamine (TPA) unit is designed and synthesized. The TPA unit can effectively stabilize the charge transferred state, and the thin film shows excellent bistable electronic switching behavior with high ON/OFF current ratio of about 105. Meanwhile, reversible and stable nanometer-scale data storage is realized on the thin film by applying pulsed voltages, and optical information storage is achieved simultaneously by utilizing fluorescence changes under UV irradiation.