Write-once-read-many Research Articles

RRAM and WORM memory devices using Protamine Sulfate and Graphene Oxide

Biomaterials are extensively exploited as the resistive switching materials since last decade. Biomaterials such as proteins, DNA, enzymes, polysaccharides, starch, natural materials are being used as the active layer for the resistive switching memory devices. In this report we have investigated the Resistive Switching (RS) Memory behavior of a biomolecule Protamine Sulfate (PS), Graphene Oxide (GO) and their mixture. It has been observed that RS device having pure PS or GO as the active layer showed non-volatile memory behavior suitable for Write Once Read Many (WORM) memory applications. Dynamic transition of switching behavior from WORM to bipolar switching observed in the device designed with PS + GO mixed system. In case of the mixed film the set and reset power is found to be less than the individuals which is advantageous with respect to the power consumption. The memory window is also found to be increased multiple times.

Probing Pathways of Conductive Filaments of FAMAPbI3 with Controlled FA Composition Using Conductive Atomic Force Microscopy

The characteristics of FAMAPbI3-based write-once-read-many (WORM) devices were controlled by a cation-exchange process as part of a technique to alter the FA composition in FAMAPbI3 films. Interest...

Quasi-2D Halide Perovskite Memory Device Formed by Acid-Base Binary Ligand Solution Composed of Oleylamine and Oleic Acid.

Organometal halide perovskite materials are receiving significant attention for the fabrication of resistive-switching memory devices based on their high stability, low power consumption, rapid switching, and high ON/OFF ratios. In this study, we synthesized 3D FAPbBr3 and quasi-2D (RNH3)2(FA)1Pb2Br7 films using an acid-base binary ligand solution composed of oleylamine (OlAm) and oleic acid in toluene. The quasi-2D (RNH3)2(FA)1Pb2Br7 films were synthesized by controlling the protonated OlAm (RNH3+) solution concentration to replace FA+ cations with large organic RNH3+ cations from 3D FAPbBr3 perovskites. The quasi-2D (RNH3)2(FA)1Pb2Br7 devices exhibited nonvolatile write-once read-many (WORM) memory characteristics, whereas the 3D FAPbBr3 only exhibited hysteresis behavior. Analysis of the 3D FAPbBr3 device indicated operation in the trap-limited space-charge-limited current region. In contrast, quasi-2D (RNH3)2(FA)1Pb2Br7 devices provide low trap density that is completely filled by injected charge carriers and then subsequently form conductive filaments (CFs) to operate as WORM devices. Nanoscale morphology analysis and an associated current mapping study based on conductive atomic force microscopy measurements revealed that perovskite grain boundaries serve as major channels for high current, which may be correlated with the conductive low-resistive-switching behavior and formation of CFs in WORM devices.

Irreversible Resistive State Switching in Devices with a Homoleptic Cobalt(II) Complex Active Layer.

Molecules with bi-stable electronic transport behaviour have been in upfront research topics of the molecular semiconductor devices in the past few decades due to the use of such materials in resistive data storage devices. Transition metal complexes (TMC) are expected to be potential candidates in regard to the tunable and manifold redox behaviour expecting multiple bulk transport states. Finding alternate mechanisms in such devices with TMC as the active layer materials would revoke the multifaceted approach to the functional gain. We have succeeded in demonstrating write once-read many (WORM) type of resistive memory device using a homoleptic Cobalt(II) (Co(II)) complex with large on/off current ratio ensuring the easy readout process at lower voltage. The advantage of this device was the turn on voltage was found to be the low (<2.7 V) operational voltage and the success ratio of the devices were more than 83%. The durability of the stored data was found to be more than 35,000 seconds which ensures the stability of the bistable state in the fabricated devices. Such ambient stable, solution processable devices are important for the large-scale printable devices. The manuscript describes the preparation, optical and electrochemical characterisation of the metal complex used along with a detailed mechanistic investigations and electrical characterisation of memory device obtained from a stable cobalt complex.

Large-scale fabrication of all-inkjet-printed resistors and WORM memories on flexible polymer films with high yield and stability

We report on the development of inkjet-printed thin-film resistors using both organic and inorganic ink formulations. The passive devices were manufactured on flexible polymer substrates in ambient condition without the need for a cleanroom environment or inert atmosphere and at a maximum temperature of 150 °C. By using the same manufacturing process, the rapid electrical sintering (RES) method is demonstrated as effective for the fabrication of inkjet-printed, programmable Write-Once-Read-Many (WORM) memories. Several hundred fully inkjet-printed resistors with different parameters were fabricated and subsequently morphologically and electrically characterized with the aim of obtaining statistically significant data. From a manufacturing process viewpoint, the procedures based on inkjet printing herein described are highly attractive: they do not require high temperatures, low pressures, special atmospheric conditions, and any masks, therefore providing a versatile low-cost approach to fabricate passive electrical components and simple circuits useful for the electronic industry. Printing can be carried out at a sufficiently low temperature to avoid damage to the fabric substrate and these devices can be used in a range of applications requiring flexible and conformal devices from embedded passive filters in PCBs to wearable electronics.

Effect of nitro substitution of azo-chalcone derivatives nano film on electrical memory properties

A nitro substituted azo-chalcone derivative 3-(4-(dimethylamino) phenyl) diazenyl)phenyl)-1-(4-nitrophenyl) prop-2-en-1-one (AZOC-4N) and a reference compound 3-(4-(dimethylamino) phenyl) diazenyl) phenyl)-1-phenylprop-2-en-1-one (AZOC-H) were synthesized by Claisen Schmidt reaction. Thermogravimetry, UV-vis and cyclic voltammetry were used to study the influence of the introduction of nitro in the conjugated molecule AZOC-4N on the photoelectric properties. The active layer was further prepared by solution spin coating, and the morphology of the film was characterized by AFM. The electrical memory performance of the device is studied. It is found that the device has the nonvolatile binary write once read many (WORM) memory performances, and the threshold voltage of the device prepared by introducing nitro group into the molecule is lower—1.4 V. Finally, the electrical memory performance of the device is analyzed by theoretical calculation.

The electric memory properties of azo-chalcone derivatives based on different film forming processes

The azo chalcone derivative 3-(4-(dimethylamino)phenyl)diazenyl)phenyl)-1- (2-nitrophenyl)prop-2-en-1-one (AZOC-2N) was designed and synthesized. The active layer was prepared by solution spin coating and vacuum evaporation methods, respectively. The accumulation of molecular film was studied by AFM and crystalline structure. It was found that the device had a non-volatile binary write once read many (WORM) memory performance and device in which form by vacuum evaporation with a higher threshold voltage -2.1 V. Finally, the electrical memory performance of the device is analysed by theoretical calculation simulation.

Multilevel Optical Labeling by Spectral Luminescence Control in Nanodiamond Color Centers.

Distinguishing a multitude of optical labels is crucial to improving the spatial and temporal resolution of bioimaging. However, current multicolor imaging approaches are limited by the spectral overlap of employed fluorophores. We here discern different instances of a single optical label type through their emission intensity. Such multilevel optical labels are enabled by an optical writing process that permanently modifies their spectral response in a predictable manner and by a separate spectral feature that serves as normalization in the presence of sample variability. The proposed approach was realized by independently controlling the emission properties of highly functionalized fluorescent nanodiamond. Upon laser irradiation, the contribution of the spectral region associated with the N3 color center decreases in a predictable and permanent fashion, while the nitrogen vacancy (NV) emission remains stable. This selective photobleaching of N3 centers was found to originate from a two-photon-assisted dissociation process that results in a 105 higher mobility of photoexcited carriers in N3 centers compared to NV. The resulting write once read many (WORM) memory exhibits multiple distinct memory levels that can be stored and read out with high robustness and reproducibility. The potential of our approach was demonstrated by characterizing markers in HeLa cells with high fidelity, despite the complex emission background. Finally, direct manipulation of label information inside of cells was demonstrated, opening up new routes in advanced bioimaging.

DNA Micro-Disks for the Management of DNA-Based Data Storage with Index and Write-Once-Read-Many (WORM) Memory Features.

DNA-based data storage has attracted attention because of its higher physical density of the data and longer retention time than those of conventional digital data storage. However, previous DNA-based data storage lacked index features and the data quality of storage after a single access was not preserved, obstructing its industrial use. Here, DNA micro-disks, QR-coded micro-sized disks that harbor data-encoded DNA molecules for the efficient management of DNA-based data storage, are proposed. The two major features that previous DNA-based data-storage studies could not achieve are demonstrated. One feature is accessing data items efficiently by indexing the data-encoded DNA library. Another is achieving write-once-read-many (WORM) memory through the immobilization of DNA molecules on the disk and their enrichment through in situ DNA production. Through these features, the reliability of DNA-based data storage is increased by allowing selective and multiple accession of data-encoded DNA with lower data loss than previous DNA-based data storage methods.

Triggering WORM/SRAM Memory Conversion by Composite Oxadiazole in Polymer Resistive Switching Device

Electrical characterization indicates that the nonvolatile write once read many (WORM) times/volatile static random access memory (SRAM) conversion was triggered by the composite of the oxadiazole small molecule. FTO/PMMA/Ag device possesses nonvolatile WORM memory behavior, while the FTO/PMMA+oxadiazole/Ag device shows vastly different volatile SRAM feature. The FTO/PMMA/Ag and FTO/PMMA+oxadiazole/Ag memory devices both exhibit high ON/OFF ratio nearly 104. The additive oxadiazole small molecule in the polymethyl methacrylate was suggested to form an internal electrode and serve as a channel during the charge transfer process, which is easy to both the charge transfer and back charge transfer, as a consequence, the WORM/SRAM conversion upon oxadiazole small molecule complexation was triggered. The results observed in this work manifest the significance of oxadiazole small molecule to the memory effects and will arouse the research interest about small molecule composite applied in memory devices.

Nano‐Graphite Clusters Regulation for Reliability Improvement of Amorphous Carbon‐Based Resistive Random Access Memory

Herein, the influence of nano‐graphite clusters on amorphous carbon‐based memories reliability is studied in detail. The size of nano‐graphite clusters is effectively controlled through vacuum annealing process, which is experimentally verified by Raman spectra. Taking advantage of the local electric‐field enhancement around the nano‐graphite clusters, the relative fluctuation of high‐resistance state/low‐resistance state (HRS/LRS) and SET/RESET voltage reduce from 66.5%/41.2% to 25.3%/19.7% and 43.2%/21.4% to 18.8%/15.4%, respectively. In addition, highly reliable write‐once‐read‐many (WORM) memories with excellent anti‐interference and high temperature (300 °C) retention capacity are also prepared thanks to the electrical modulating characteristic of graphite clusters to amorphous carbon (a‐C) film.

Nonvolatile WORM and rewritable multifunctional resistive switching memory devices from poly(4-vinyl phenol) and 2-amino-5-methyl-1,3,4-thiadiazole composite

A multifunctional resistive switching memory devices with the typical sandwich structure of Al/Poly(4-vinylphenol) (PVP)+2-Amino-5-methyl-1,3,4-thiadiazole/Al is fabricated. Al as the bottom and top electrodes is easy to realize by simple thermal evaporation process, and a PVP and 2-Amino-5-methyl-1,3,4-thiadiazole composite film as the active layer is prepared by sol-gel method and spin coating process. The as-fabricated resistive switching memory device shows write-once-read-many (WORM) and rewritable multifunctional memory behaviors, for the rewritable and WORM memory modes, the ON/OFF ratio is 104 and 80, respectively. The as-fabricated device shows tristable conductivity states which equivalent to “0”, “1” and “2”, and these three conductance states are steady under the constant voltage retention test, as well as during the endurance test, indicating advantageous features of stable operation and dependable endurance. It is noteworthy that the simple preparation process is expected to promisingly hold the post of industrialization low-cost preparation in future electronic devices for ternary data storage utilities.

Write once read many times resistance switching memory based on all-inorganic perovskite CsPbBr3 quantum dot

Write Once Read Many (WORM) Memory, as one of the most important nonvolatile memory type, has widespread used in a variety of permanent storage applications in the Big Data age. As an excellent material, CsPbBr3 quantum dots have widely used in a lot of photoelectric devices, but CsPbBr3 quantum dots based memory device remain to be studied. In this work a WORM memory device based on CsPbBr3 quantum dots is demonstrated. The CsPbBr3 QDs based WORM shows great reproducibility, good data retention ability, irreversible electrical transition from the high resistance state (HRS) or OFF state to the low resistance state (LRS) or ON state and the resistance ratio (ON/OFF) can reach almost 104. Additionally, the device exhibits high performances under low power consumption — low reading voltage (−0.5 V) and writing voltage (−1.1V). To study the CsPbBr3 QDs based WORM provides an opportunity to develop the next generation high-performance and stable WORM devices.

Multiple resistive switching behaviours of CH3NH3PbI3 perovskite film with different metal electrodes

The utilization of defects in organic-inorganic hybrid perovskite materials such as CH3NH3PbI3 is beneficial for memory applications. In this work, a simple CH3NH3PbI3 memory device with various commonly used electrodes such as aluminium (Al), silver (Ag), and gold (Au) yielded different switching behaviours. Using Al in ITO/CH3NH3PbI3/Al device reveals Resistive Random Access Memory (ReRAM) behaviour with a SET voltage of 4.5 V and can be RESET by applying a negative sweep voltage above 1.3 V due to the formation of iodide vacancy filament. Interestingly, by using Ag and Au cathodes to replace Al, yielded Write-Once-Read-Many (WORM) resistive switching characteristics. The conversion process from OFF to ON occur at around 4.7 V and 4.0 V for Ag and Au, respectively. The “shorting effect” remains even though a reverse voltage was applied indicating data retention. These fabricated devices could contribute to further understanding of selecting the right electrodes and open up new possibility of studies in the direction of resistive switching memory applications.

Organic WORM memory with carbon nanoparticle/epoxy active layer

Following the “All With One (AW1)” technology proposed in our earlier work, the present study is focused on the production and the characterization of write once read many (WORM) memory devices with a carbon nanoparticle/epoxy resin nanocomposite, where the main advantage stands on the ease of production of the nanostructured phase. The results revealed that short 100-ns, low-voltage (5.0-V) electric pulses are enough to record a bit, and the bit one to bit zero current state ratio \(I_\mathrm{{ON}}/I_\mathrm{{OFF}}\) reaches 10\(^{7}\).

Synthesis and resistive switching characteristics of polyimides derived from 2,7-aryl substituents tetraphenyl fluorene diamines

Four new symmetric diamines (4,4′-(2,7-diphenyl-9H-fluorene-9,9-diyl)dianiline (TPF-Ph), 4,4′-(2,7-bis(4-(naphthalen-1-yl)phenyl)-9H-fluorene-9,9-diyl)dianiline (TPF-Ph-Na), 4,4′-(2,7-di([1,1′-binaphthalen]-4-yl)-9H-fluorene-9,9-diyl)dianiline (TPF-2Na), and 4,4′-(2,7-bis(3,5-dimethoxyphenyl)-9H-fluorene-9,9-diyl)dianiline (TPF-Ph-OMe)) containing tetraphenyl fluorene (TPF) core were synthesized through Suzuki coupling reaction, the corresponding four polyimides (PI(TPF-Ph), PI(TPF-Ph-Na), PI(TPF-2Na), and PI(TPF-Ph-OMe)) were prepared through polymerization reaction. The electrical memory measurement displayed that PI(TPF-Ph) and PI(TPF-Ph-Na) exhibited volatile dynamic random access memory (DRAM) behaviors, PI(TPF-2Na) possessed volatile static random access memory (SRAM) behavior due to the more distorted structure of 1,1′-binaphthalenyl moiety, and PI(TPF-Ph-OMe) showed non-volatile write-once read-many (WORM) behavior due to the presence of deeper charge traps and higher dipole moment of 3,5-dimethoxyphenyl substituent. They possessed low turn-on switching voltages and the ON/OFF current ratios were between 103 and 105 with the retention times up 4 × 103 s. Quantum simulations about energy levels, electrostatic potential (ESP) surfaces, and dipole moment were used to demonstrate the switching mechanism. The experimental results indicated that the electrical memory behaviors of the synthesized polyimides could be tuned through rational structural modification of the electron donor moiety.

Self-assembled oligosaccharide-based block copolymers as charge-storage materials for memory devices

Over the past few years, extremely high charge-storage capacities of glucose-based oligo- or polysaccharides have been discovered that enables such materials to hold a great potential in electronics applications due to their abundant and renewable materials. Typically, the introduction of an α-glucan-containing polysaccharide into the dielectric layer of a transistor-type memory device causes excellent irreversible electron-capture properties; hence, a transistor device embedded with oligosaccharide maltoheptaose domains expresses write-once-read-many (WORM)-type behavior, which confirms that green materials can be used for advanced electronics. However, their irreversible WORM-type characteristics also restrict the application α-glucan-containing polysaccharides in high-performance electronic devices. Recent advances in oligosaccharide-based block copolymers through the inherent immiscibility of different polymer segments can enhance not only the formation of self-assembled nanostructures but also the switching of memory properties. Furthermore, supramolecular structures composed of oligosaccharide-based block copolymers and conjugated moieties can be developed into high-performance nonvolatile organic field-effect transistor (OFET) memory devices. This mini review presents an overview of the recent literature in oligosaccharide maltoheptaose-based block copolymers and their promising applications in organic memory devices.

Sulfur (VI) Fluoride Exchange Polymerization for Large Conjugate Chromophores and Functional Main-Chain Polysulfates with Nonvolatile Memory Performance.

Sulfur (VI) fluoride exchange (SuFEx) reactions can be applied not only in organic click synthesis, but also in the preparation of functional main-chain polymers. In this work, four functional main-chain polysulfates (PNT-PS, NPNT-PS, PHF-PS, and TPE-PS) are synthesized in high yield using the SuFEx reaction at room temperature. The polysulfates exhibit satisfactory thermal stability and solution processability. They are used as the active layer for memory devices (ITO/PNT-PS/Al, ITO/NPNT-PS/Al, ITO/PHF-PS/Al, and ITO/TPE-PS/Al). I-V measurements show that ITO/PNT-PS/Al and ITO/NPNT-PS/Al exhibit stable flash-memory (write-read-erase) behavior, while ITO/PHF-PS/Al and ITO/TPE-PS/Al exhibit WORM (write once read many) behavior. Our studies provide a feasible and efficient synthetic methodology for the preparation of new memory materials.

Silver Nanowire Mesh-Based Fuse Type Write-Once-Read-Many Memory

Fuse type write-once-read-many (WORM) memories are fabricated based on silver nanowire (AgNW) meshes using simple dispensing and bar-coating processes without needing precise patterning. Compared to previous work, the AgNW mesh WORM memories can be programmed at lower voltage (2.3 V) and current (<10 mA), and thus through near field communication by smart phones. The devices present stable “unwritten” and “written” states for reading operations of 6000 times. Finally, 4-bit WORM memories are fabricated and attached on a packaging box with programming and reading operations by a smart phone to verify its potential for practical applications.

Development of a Measurement Software for the Characterization of WORM Devices for Novel Memory Storage Applications

We hereby propose a software solution to perform high quality electrical measurements for the characterization of WORM (write-once read many), a new generation memory device which is being intensively studied for non-volatile data storage. The as-proposed software is completely based on .NET framework and sample C# code. The paper performed a relevant measurement based on this software. Working WORM devices, based on a polymeric matrix embedded with gold and copper sulfide nanoparticles, have been used for test measurements. The aim of this paper is to show the main steps to develop a fully working measurement software without using any expensive dedicated software.