Flexible Resistive Switching Memory Research Articles

S-Layer Protein for Resistive Switching and Flexible Nonvolatile Memory Device.

In this work, a flexible resistive switching memory device consisting of S-layer protein (Slp) is demonstrated for the first time. This novel device (Al/Slp/indium tin oxide/polyethylene terephthalte) based on a simple and easy fabrication method is capable of bistable switching to low resistive state (LRS) and high resistive state (HRS). This device exhibits bistable memory behavior with stability and a long retention time (>4 × 103 s), being stable up to a 500 cycle endurance test and with significant HRS/LRS ratio. The device possesses consistent switching performance for more than 100 times bending, corresponding to desired applicability for biocompatible wearable electronics. The memory mechanism is attributed to a trapping/de-trapping process in S-layer protein. These promising results of the flexible memory device could find a way in the wearable storage applications like smart bands and sports equipments' sensors.

Highly Flexible Resistive Switching Memory Based on the Electronic Switching Mechanism in the Al/TiO2/Al/Polyimide Structure

A highly flexible resistive switching (RS) memory was fabricated in the Al/TiO2/Al/polyimide structure using a simple and cost-effective method. An electronic-resistive-switching-based flexible memory with high performance that can withstand a bending strain of up to 3.6% was obtained. The RS properties showed no obvious degradation even after the bending tests that were conducted up to 10 000 times, and over 4000 writing/erasing cycles were confirmed at the maximally bent state. The superior electrical properties against the mechanical stress of the device can be ascribed to the electronic RS mechanism related to electron trapping/detrapping, which can prevent the inevitable degradation in the case of the RS related with the ionic defects.

Hydrogen-peroxide-modified egg albumen for transparent and flexible resistive switching memory

Egg albumen is modified by hydrogen peroxide with concentrations of 5%, 10%, 15% and 30% at room temperature. Compared with devices without modification, a memory cell of Ag/10% H2O2-egg albumen/indium tin oxide exhibits obviously enhanced resistive switching memory behavior with a resistance ratio of 104, self-healing switching endurance for 900 cycles and a prolonged retention time for a 104 s @ 200 mV reading voltage after being bent 103 times. The breakage of massive protein chains occurs followed by the recombination of new protein chain networks due to the oxidation of amidogen and the synthesis of disulfide during the hydrogen peroxide modifying egg albumen. Ions such as Fe3+, Na+, K+, which are surrounded by protein chains, are exposed to the outside of protein chains to generate a series of traps during the egg albumen degeneration process. According to the fitting results of the double logarithm I–V curves and the current-sensing atomic force microscopy (CS-AFM) images of the ON and OFF states, the charge transfer from one trap center to its neighboring trap center is responsible for the resistive switching memory phenomena. The results of our work indicate that hydrogen- peroxide-modified egg albumen could open up a new avenue of biomaterial application in nanoelectronic systems.

Silver Nanowire/Colorless-Polyimide Composite Electrode: Application in Flexible and Transparent Resistive Switching Memory

Improving the performance of resistive switching memories, while providing high transparency and excellent mechanical stability, has been of great interest because of the emerging need for electronic wearable devices. However, it remains a great challenge to fabricate fully flexible and transparent resistive switching memories because not enough research on flexible and transparent electrodes, for their application in resistive switching memories, has been conducted. Therefore, it has not been possible to obtain a nonvolatile memory with commercial applications. Recently, an electrode composed of a networked structure of Ag nanowires (AgNWs) embedded in a polymer, such as colorless polyimide (cPI), has been attracting increasing attention because of its high electrical, optical, and mechanical stability. However, for an intended use as a transparent electrode and substrate for resistive switching memories, it still has the crucial disadvantage of having a limited surface coverage of conductive pathways. Here, we introduce a novel approach to obtain a AgNWs/cPI composite electrode with a high figure-of-merit, mechanical stability, surface smoothness, and abundant surface coverage of conductive networks. By employing the fabricated electrodes, a flexible and transparent resistive memory could be successfully fabricated.

Transferable and flexible resistive switching memory devices based on PMMA films with embedded Fe3O4 nanoparticles

We demonstrated transferable and flexible resistive switching (RS) memory devices using a nondestructive water-dissolution method. To satisfy future demands, the free-standing Al/Fe3O4-PMMA/Al devices were transferred onto various nonconventional substrates to demonstrate various features, such as flexibility, 3-D conformality, and biocompatibility. Thanks to the strong van der Waals interaction, the devices can easily conform to these substrates and normally display RS behavior even after undergoing bending tests. In particular, the memory devices with the PET substrate present excellent memory performance as well as high flexibility, including fast switching speed (<50 ns), large ROFF/RON ratio (∼4 × 105), and long retention time (>104 s). No performance degradation occurs after bending the device to different angles and up to 104 times. The RS mechanism can be attributed to the trapping/de-trapping of electrons at the sites of Fe3O4 nanoparticles. This result provides a feasible approach to achieve transferable RS memory device for future conformal and flexible electronics.

Metal-Organic Framework-Based Flexible Resistive Switching Memory Devices

Metal-organic framework (MOF) which consists of metal ionic nodes and organic linkers has wide applications such as hydrogen storage, catalysts, and gas sensors due to its structural and chemical versatilities. On demand for currently increasing interests for flexible and wearable electronic devices, it is suggested that some MOF materials have electrical hysteresis phenomena which can be further utilized as data storage device. The hysteresis arises from redox-active behavior of organic molecules. By selecting proper substances, realizing MOF-based resistive switching memory device could be possible. In this work, we applied zeolitic-imidazolate framework (ZIF-8), one of MOF materials, which is composed of zinc ions and imidazole molecules, as the resistive switching layer on the plastic substrate. The ZIF-8 layer on the gold-coated polyethylene terephthalate substrate is deposited by simple solution processes. Flexible ZIF-8-based resistive switching memory possesses set/reset behavior consistent over several cycles with good mechanical flexibility. The resistive switching behavior of ZIF-8-based device is thought to be due to the changes of charge conduction mechanisms from electron hopping to transporting through conjugated organic molecules. Flexible resistive switching memory device with solution-processed ZIF-8 thin film could be a promising candidate for flexible and wearable memory devices.

Direct Observation of Indium Conductive Filaments in Transparent, Flexible, and Transferable Resistive Switching Memory.

Electronics with multifunctionalities such as transparency, portability, and flexibility are anticipated for future circuitry development. Flexible memory is one of the indispensable elements in a hybrid electronic integrated circuit as the information storage device. Herein, we demonstrate a transparent, flexible, and transferable hexagonal boron nitride (hBN)-based resistive switching memory with indium tin oxide (ITO) and graphene electrodes on soft polydimethylsiloxane (PDMS) substrate. The ITO/hBN/graphene/PDMS memory device not only exhibits excellent performance in terms of optical transmittance (∼85% in the visible wavelength), ON/OFF ratio (∼480), retention time (∼5 × 104 s) but also shows robust flexibility under bending conditions and stable operation on arbitrary substrates. More importantly, direct observation of indium filaments in an ITO/hBN/graphene device is found via ex situ transmission electron microscopy, which provides critical insight on the complex resistive switching mechanisms.

Zeolitic-imidazole framework thin film-based flexible resistive switching memory

A flexible resistive switching memory device based on ZIF-8 is fabricated using a dip coating method. The device shows reliable resistive switching with mechanical stability.

Highly flexible resistive switching memory based on amorphous-nanocrystalline hafnium oxide films.

Flexible and transparent resistive switching memories are highly desired for the construction of portable and even wearable electronics. Upon optimization of the microstructure wherein an amorphous-nanocrystalline hafnium oxide thin film is fabricated, an all-oxide based transparent RRAM device with stable resistive switching behavior that can withstand a mechanical tensile stress of up to 2.12% is obtained. It is demonstrated that the superior electrical, thermal and mechanical performance of the ITO/HfOx/ITO device can be ascribed to the formation of pseudo-straight metallic hafnium conductive filaments in the switching layer, and is only limited by the choice of electrode materials. When the ITO bottom electrode is replaced with platinum metal, the mechanical failure threshold of the device can be further extended.

Facile Synthesis of Co9Se8 Quantum Dots as Charge Traps for Flexible Organic Resistive Switching Memory Device

Uniform Co9Se8 quantum dots (CSQDs) were successfully synthesized through a facile solvothermal method. The obtained CSQDs with average size of 3.2 ± 0.1 nm and thickness of 1.8 ± 0.2 nm were demonstrated good stability and strong fluorescence under UV light after being easily dispersed in both of N,N-dimethylformamide (DMF) and deionized water. We demonstrated the flexible resistive switching memory device based on the hybridization of CSQDs and polyvinylpyrrolidone (PVP) (CSQDs-PVP). The device with the Al/CSQDs-PVP/Pt/poly(ethylene terephthalate) (PET) structure represented excellent switching parameters such as high ON/OFF current ratio, low operating voltages, good stability, and flexibility. The flexible resistive switching memory device based on hybridization of CSQDs and PVP has a great potential to be used in flexible and high-performance memory applications.

Resistive Switching in Al/Al2O3/TiO2/Al/PES Flexible Device for Nonvolatile Memory Application.

Resistive switching memory devices with superior properties are possibly used in next-generation nonvolatile memory to replace the flash memory. In addition, flexible electronics has also attracted much attention because of its light-weight and flexibility. Therefore, an Al/Al2O3/TiO2/Al/PES flexible resistive switching memory is employed in this study. The resistive switching characteristics and stability of the flexible device are improved by inserting the Al2O3 film. The resistive switching of the flexible device can be repeated over hundreds of times after the bending test. A possible resistive switching model of the flexible device is also proposed. In addition, the non-volatility of the flexible device is demonstrated. Based on our research results, the proposed Al2O3/TiO2-based resistive switching memory is possibly used in next-generation flexible electronics and nonvolatile memory applications.

Flexible resistive switching memory with a Ni/CuOx/Ni structure using an electrochemical deposition process

Flexible resistive switching memory (ReRAM) devices were fabricated with a Ni/CuOx/Ni structure. Fabrication involved simple and low-cost electrochemical deposition of electrodes and resistive switching layers on a polyethylene terephthalate substrate. The devices exhibited reproducible and reliable ReRAM characteristics. Bipolar resistive switching was observed in flexible Ni/CuOx/Ni-based ReRAM devices with low operation voltages. The reliability of the devices was confirmed by data retention, endurance, and cyclic bending measurements. The processes for fabrication of flexible ReRAM devices were based on simple-solution, bottom-up growth and they can be performed at low temperatures. Therefore, the methods presented in this work could be a viable solution for fabricating flexible non-volatile memory devices in the future.

Biocompatible and Flexible Chitosan‐Based Resistive Switching Memory with Magnesium Electrodes

A flexible and transparent resistive switching memory based on a natural organic polymer for future flexible electronics is reported. The device has a coplanar structure of Mg/Ag‐doped chitosan/Mg on plastic substrate, which shows promising nonvolatile memory characteristics for flexible memory applications. It can be easily fabricated using solution processes on flexible substrates at room temperature and indicates reliable memory operations. The elucidated origin of the bipolar resistive switching behavior is attributed to trap‐related space‐charge‐limited conduction in high resistance state and filamentary conduction in low resistance state. The fabricated devices exhibit memory characteristics such as low power operation and long data retention. The proposed biocompatible memory device with transient electrodes is based on naturally abundant materials and is a promising candidate for low‐cost memory applications. Devices with natural substrates such as chitosan and rice paper are also fabricated for fully biodegradable resistive switching memory. This work provides an important step toward developing a flexible resistive switching memory with natural polymer films for application in flexible and biodegradable nanoelectronic devices.

Characteristics of graphene-oxide-based flexible and transparent resistive switching memory

Recently, resistive switching memory attracts much attention because of its simple structure, easy operation, and non-volatility. In addition, transparent and flexible electronic equipment also attracts much attention. Therefore, ITO/GO/ITO/PES flexible and transparent resistive switching memory devices are proposed. The resistive switching characteristics of the flexible devices are almost unchanged after performing a bending test. So the flexibility of the devices is demonstrated. The retention time of the flexible devices reaches to 105s. The transmittance of the flexible devices is over 80% for the visible light region. Generally speaking, the proposed ITO/GO/ITO/PES device shows great performance. It possibly can be used in the next-generation flexible and transparent electronic equipment.

Highly flexible titanium dioxide-based resistive switching memory with simple fabrication

We demonstrate a flexible resistive switching random access memory (ReRAM), which is a promising next-generation memory on a flexible substrate. The proposed method enables us to fabricate an Al/TiO2/Al structure on a polyimide substrate, which has highly flexible and durable characteristics, rather than a Si-based substrate by a simple fabrication process. To understand the role of oxygen vacancies in TiO2, our devices was analyzed by X-ray photoelectron spectroscopy (XPS) and XPS depth profile analyses. Moreover, severe bending of the device did not affect the memory performance owing to its small channel length and the high ductility of the electrode. The results presented here can provide a new approach to the fabrication of nonvolatile memories for flexible electronic devices.

Resistive Switching Behavior of Al/Al<sub>2</sub>O<sub>3</sub>/ZrO<sub>2</sub>/Al Structural Device for Flexible Nonvolatile Memory Application

Resistive switching memory with good performance can be possibly used in next-generation nonvolatile memory and flexible electronics. In the previous studies, some of the flexible resistive switching layers were organic materials. In this paper, an inorganic Al/Al 2 O 3 /ZrO 2 /Al flexible resistive switching memory fabricated at room temperature is proposed for the first time. The resistive switching can be reproduced for over 100 times with stable resistive switching characteristics. In addition, a possible resistive switching filamentary model of the flexible device is demonstrated in this paper. The flexibility and nonvolatility of the flexible device are also demonstrated. Based on the experimental results, the proposed Al/Al 2 O 3 /ZrO 2 /Al flexible device is possibly used in next-generation flexible electronics.

Graphene-oxide-based resistive switching device for flexible nonvolatile memory application

Resistive switching memory, flexible electronics equipment, and graphene-oxide-based devices have attracted much attention recently because of their possible application in next-generation electronic devices. In this study, a graphene-oxide-based flexible resistive switching memory is proposed. The flexibility and nonvolatility of the flexible device are demonstrated. A possible resistive switching filamentary model of the flexible device is also proposed. The experimental results indicate that the proposed graphene-oxide-based device is promising for use in next-generation nonvolatile memory and flexible electronics equipment.

Transparent and flexible resistive switching memory devices with a very high ON/OFF ratio using gold nanoparticles embedded in a silk protein matrix

The growing demand for biomaterials for electrical and optical devices is motivated by the need to make building blocks for the next generation of printable bio-electronic devices. In this study, transparent and flexible resistive memory devices with a very high ON/OFF ratio incorporating gold nanoparticles into the Bombyx mori silk protein fibroin biopolymer are demonstrated. The novel electronic memory effect is based on filamentary switching, which leads to the occurrence of bistable states with an ON/OFF ratio larger than six orders of magnitude. The mechanism of this process is attributed to the formation of conductive filaments through silk fibroin and gold nanoparticles in the nanocomposite. The proposed hybrid bio-inorganic devices show promise for use in future flexible and transparent nanoelectronic systems.

Flexible resistive switching memory devices composed of solution-processed GeO2:S films

► ReRAM devices are fabricated with solution-processable GeO 2 :S on flexible substrates. ► The Al/GeO 2 :S/Au ReRAM devices exhibit unipolar resistive switching behavior. ► The on/off ratio is about 10 7 . ► The memory characteristics are retained after 10 4 s. ► The memory characteristics are retained even after bending test for 10 3 cycles. In this study, resistive random access memory (ReRAM) devices are fabricated using solution-processable sulfur-doped GeO 2 (GeO 2 :S) on flexible substrates. The Al/GeO 2 :S/Au ReRAM devices exhibit the unipolar resistive switching behavior with an on/off ratio of more than 10 7 and the memory characteristics are retained after 10 4 s. The memory characteristics are unaffected by strains, even after the continuous substrate bending test for 10 3 cycles.

P‐76: Resistive Switching Memory Device Based on Amorphous Al‐Zn‐Sn‐O Film for Flexible Electronics Application

AbstractWe have fabricated flexible resistive switching memory (RRAM) using Al‐doped zinc tin oxide (AZTO) as resistive switching layers. The AZTO RRAM with robust memory window over hundreds of switching cycles. Besides, a conceptual co‐operation scheme was also demonstrated between AZTO RRAM and thin film transistor (TFT) for flexible electronics application.