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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. • A multifunctional resistive switching memory devices was fabricated. • The as-fabricated device shows tristable conductivity states. • It is expected to promisingly hold the post of ternary data storage utilities. [ABSTRACT FROM AUTHOR]

Abstract The influence of blending ratio on resistive switching effect in donor-acceptor type composite of [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) and poly(N -vinylcarbazole) (PVK)-based memory devices are investigated. Current-voltage (I - V) curves for the ITO/PCBM + PVK/Al devices with 9 wt.% of PCBM showed a current bistability with a maximum OFF/ON resistance ratio of 9 × 104, which was 100 times larger than that of the device with 23 wt.% of PCBM and was 2000 times larger than that of the device with 41 wt.% of PCBM. Furthermore, the threshold voltage obviously decreased as the PCBM concentration increases. The retention time was above 105 s indicative of the memory stability of the as-fabricated devices. The I - V characteristics at OFF state dominantly comply with the rules of space-charge-limited-current behaviors, and I - V curve at ON state obey Ohmic laws. The proposed device suggests a promising approach for adjustale OFF/ON resistance ratio and threshold voltage in electronic memory devices. Graphical abstract Image Highlights • The influence of blending ratio on resistive switching effect are investigated. • The threshold voltage obviously decreased as the PCBM concentration increases. • The resistance ratio obviously increased with the PCBM concentration decreases. [ABSTRACT FROM AUTHOR]

Organic materials are the key to the next generation of electric memory elements because of their low cost, high flexibility and high scalability. Solution-processed n-channel and p-channel organic field effect transistors (FETs) by spinning coating technique was demonstrated. We use based-poly (vinylcarbazole) (PVK) p-type transistor and based-6-phenyl-C61 butyric acid methyl ester (PCBM) n-type transistor as the channel of bottom gate structure FET, respectively, to fabricate the complementary inverter. The maximum voltage gain of the electrically isolated FET complementary inverter is up to 22, the power consumption is less than 3 μW, and the transition voltage is −4.2 V. In addition, our devices are able to implement "AND", "NAND", "OR", and "NOT" gate logic well. But more than that, p-type transistor based on PVK and n-type transistor based on PCBM were combined with the memristor, reward-modulated spike timing dependent plasticity was implemented by introduced reward/punishment signals to guide synaptic weight updates. It shows great potential in the electronic application system with low cost and high energy efficiency. [ABSTRACT FROM AUTHOR]

The incorporation of the one-dimensional carbon nanomaterial carbon nanotubes (CNTs) in poly(methyl methacrylate) (PMMA) was found to successfully develop a resistive switching. It implements memristic characteristics which shift from bistable to tristable memory. The localized current pathways in the organic nanocomposite layers for each intermediate resistive state (IRS) are attributed to the trapping mechanism consistent with the fluorescent measurements. Multi-bit organic memories have attracted considerable interest, which provide an effective way to increase the memory density per unit cell area. This study will be useful for the development and tuning of multi-bit storable organic nanocomposite memory device systems. [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotube (MWCNT) displays peculiar electrical behavior, with its nano-configuration consisting of exceptional graphene flakes. As for MWCNTs blended into polymethyl methacrylate (PMMA), sandwiched Ni/MWCNTs(2 wt%):PMMA/ITO was manufactured to investigate into the multi-bit resistive switching regarding the turn-on compliance current as well as the thickness of the active layer. It bears ternary write-once read-many-times (WORM) memory, whose current proportionality between ON-state and OFF-state can exceed 10 7 . Moreover, the memory performance, covering the long-term retention (>10 6 s), better endurance (>10 12 cycles) and device-to-device profiles, confirms the excellent ternary memory of MWCNTs:PMMA. Concentration on multi-bit resistive switching in respect of MWCNTs underlies performance enhancement, higher integration and advanced architecture. [ABSTRACT FROM AUTHOR]

• Threshold switching characteristics has been reported in 2D composite nanomaterials. • The effectiveness of cross crosstalk suppression was indicated by assembled 1S1R unit. • The developmental potentiality to restrain the crosstalk issue was indicated. 2D composite nanomaterials of insulating boron nitride (BN) and semiconductor molybdenum disulfide (MoS 2)-based flexible threshold switching selectors (Ag/BN+MoS 2 /Ag based on BM1 and BM2) are fabricated. Both selectors shown excellent bidirectional threshold switching characteristics. The assembled 1S1R unit comprising Ag/BN+MoS 2 /Ag based on BM1 selector and bipolar rewritable Ag/ZnO/Ag resistive switching memory shows the effectiveness of cross crosstalk suppression. The thermal conductivity of the functional layer based on BM2 decreasing to some extent with the content of BN decreasing, resulting in an increasing trend of V hold compared with selector based on BM1. And the selectors of Ag/BN+MoS 2 /Ag based on BM2 were assembled with a unidirectional open WORM Ag/polyvinyl carbazole/Ag memory, it also shows a good effect in restraining the crosstalk. It has large developmental potentiality in flexible 2D composite nanomaterials threshold switching selector to restrain the crosstalk issue for a large RRAM array. [ABSTRACT FROM AUTHOR]

The resistive switching memories are in prosperity development on account of its simple structure and high performance. A primary problem of resistive switching memory reliability is discrete and random distribution of resistive switching parameters, which limits greatly the possible range of its digital memory application on account of uniformity of resistance parameters is poor and the distribution range is too large. But, from the other side, these random parameter distributions are eable be used to complete some computing tasks. Here, a random number generation is demonstrated with stochastic variation of V set in a flexible threshold switching device by using the carbon nanotube and polyvinyl alcohol composite materials. Two reading voltages was applied to the two threshold switching devices, the electric potential of V cin randomized either positive or negative in accordance with the cycle to cycle evolution of two threshold switching devices by the control of the voltage divider, which in return comes about a random bitstream after passing by the comparer. As well as, its transient characteristics have been illustrated for data security appilcation. Image 1 • For data safety, polyvinyl alcohol and Mg were used to fabricated transient device. • The volatile ovonic threshold switching behavior has been reported. • A random number generation is built with stochastic variation of V set in a threshold switching device. • The transient characteristics have been illustrated for data security appilcation. [ABSTRACT FROM AUTHOR]

• The Al/PCBM + PVP/Al memory devices are prepared by spin-coating process. • The memory device exhibits a typical nonvolatile write-once-read-many-times storage effect. • The multistage resistive switching processes in memory device were reported. • The broken processes of carbon-rich conducting filament have been clarified. • The conductance quantization during resistive switching processes was analyzed. Memory devices were prepared by spin-coating process, and the multistage resistive switching behavior has been found in organic coating films-based of memory device. The composite of 6 , 6 -phenyl C 61 -butyric acid methyl ester and polyvinyl pyrrolidone were used as active layer materials. The as-prepared device exhibits a typical nonvolatile write-once-read-many- times storage effect, and shows multistate resistive switching behavior, and there are obvious distinctions between different resistance states. The resistance in low resistance state (LRS) and high resistance state (HRS) dependence on temperature is tested, and the resistance of LRS and HRS show metal and semiconductor characteristics, respectively. As well as, the resistance in HRS shows evident dependence on cell size. Hence, the resistive switching mechanism was attributed to the broken processes of carbon-rich conducting filament. Furthermore, conductance quantization during resistive switching processes was analyzed. This work might make it attractive for exploiting high density data storage. [ABSTRACT FROM AUTHOR]

The logic circuit is the main component of an integrated circuit chip that dictates the operation and performance of the chip. The logic circuit based on a memristor can improve the integration and operation speed of the existing integrated circuit and reduce the chip size and the number of devices used by a single logic circuit. However, most of the research on logic circuits based on memristors has focused only on simulations, and research on the realization of logic circuits by hardware using actual memristors is limited. In this paper, a memristor based on graphene oxide with stable complementary resistive switching characteristics is fabricated, a logic circuit is built by using this device, and the logic functions of "IMP," "AND," and "NOR" are successfully realized. The complementary resistive switching device can alleviate the severe power loss caused by the memory separation of the von Neumann architecture. Moreover, its unique structure enables it to realize material logic independently without the use of multiple memristors and resistors, providing a new scheme for the physical realization of logic circuits. It also opens up a new path for integrated chips to break through von Neumann architecture. [ABSTRACT FROM AUTHOR]

A multistate data memory device can store more than one bit in each cell. Such devices have broad application prospects because they provide a simple and low-cost way to improve memory capacity. As a biomaterial, silkworm hemolymph (SH) has the advantages of being easily accessible, biodegradable and biocompatible. In this study, performance-tunable multistate data storage devices with an indium tin oxide (ITO)/graphene oxide (GO)/SH/GO/Al structure were fabricated with SH and GO as dielectric layers. The results show that the proposed device structure has stable nonvolatile and bipolar switching characteristics. The conductivity and ON/OFF current ratio (1–103) of such a device can be adjusted by modifying the GO concentration. With appropriate control of the compliance current (I CC), the device can be switched to six different resistance states, enabling multistate data storage capabilities and allowing high-density data storage to be realized. These devices have a long retention time (104 s) and extended endurance. Their switching behavior is attributed to the formation and fracture of oxygen vacancy conductive filaments. This research introduces a new approach to the development of biocompatible high-density memory devices. [ABSTRACT FROM AUTHOR]

In this work, a resistive switching memory device was fabricated based on egg protein, a natural biomaterial. The effect of graphene composite on the resistive switching characteristics of the device was investigated. The experimental results show that both pure egg protein and graphene composite devices exhibit bipolar nonvolatile resistive conversion properties. Both devices have good data retention capability. Furthermore, the composite of graphene can effectively improve the device endurance and the consistency of the on-state current distribution of the device. Based on the theory of capture and de-capture of charge carrier, the mechanism of resistive switching is analyzed. The biological egg protein was used as functional layer, and graphene was used as channel medium and trap layer material. Then, the effect of graphene composite on biological egg protein resistance switching memory properties was investigated. The endurance property and the consistency of the on-state current distribution of the device have been effectively improved by the composite of graphene. [ABSTRACT FROM AUTHOR]

Owing to the highly parallel network structure of the biological neural network and its triggered processing mode, tactile sensory neurons can realize the perception of external signals and the functions of perception, memory, and data processing by adjusting the synaptic weight. In this paper, a piezoresistive pressure sensor is combined with a memristor to design an artificial tactile sensory neuron. The polyurethane sponge sensor has excellent sensitivity and can convert physical stimuli into electrical signals, and the chitosan‐based memristor has stable bipolar resistive switching characteristics, allowing further information to be memorized and processed. The neuron can respond to tactile stimuli of different degrees, durations, and frequencies; realize potentiation/depression modulation, paired‐pulse facilitation, and spike‐timing‐dependent plasticity; exhibit spike‐rate‐dependent plasticity; and store and erase tactile information through memistor state switching, which has great application potential in biological sensing systems. [ABSTRACT FROM AUTHOR]

A stable I – V repeatability memristor based on amorphous InGaZnO (a-IGZO) with a TiO 2 insertion layer was investigated. Two memristive structures composed of Pt/a-IGZO/Pt and Pt/TiO 2 /a-IGZO/Pt were manufactured on SiO 2 /Si substrate by the magnetron sputtering method. The crystallization of IGZO thin films was analyzed by the XRD process under different annealing temperatures, and the results show that the thin films remain in a stable amorphous state. The resistive switching performance of the two structures was tested by the semiconductor parameter analyzer 4200-SCS at room temperature. After 30 cyclic scans, the Pt/a-IGZO/Pt structure shows signs of degeneration in its I – V cyclic characteristics. However, in the Pt/TiO 2 /a-IGZO/Pt structure, the cyclic characteristics of I – V are highly stable (cycles >105 sweeps) with a limiting operating current of 0.01 A. Its rectification ratio is approximately 20 at low operating voltages (±1.0 V), and conductance increases (or decreases) progressively with continuous positive (or negative) voltage scans. Further analysis of the experimental energy band diagram was measured by UV–vis spectra and ultraviolet photoemission spectroscopy (UPS). The results demonstrate that the operational mechanism is the modulation of the barrier at the TiO 2 /a-IGZO interface, which is conducive to the stable I – V cyclic characteristic of Pt/TiO 2 /a-IGZO/Pt memristor. [ABSTRACT FROM AUTHOR]

The synaptic behavior of the Ni–Co layered double hydroxide-based memristor was demonstrated. The modulation effect of pulse amplitude, duration, and excitation interval on the conductance of memristor is analyzed. On account of analog resistive switching features, and the nonlinear transmission characteristics of synapses, pulse-time-dependent plasticity, long-term/short-term memory, and "learning" and "forgetting" behaviors of synapses are simulated and carried out. The analog bipolar resistance switch was ascribed to the formation and breakdown of oxygen filaments formed in Ni–Co layered double hydroxides films. This kind of memristor with an analog resistance switch is very promising to provide an implementation method for the development of electronic synapse function. [ABSTRACT FROM AUTHOR]

By doping a dielectric layer material and improving the device's structure, the electrical characteristics of a memristor can be effectively adjusted, and its application field can be expanded. In this study, graphene quantum dots are embedded in the dielectric layer to improve the performance of a starch-based memristor, and the PMMA layer is introduced into the upper and lower interfaces of the dielectric layer. The experimental results show that the switching current ratio of the Al/starch: GQDs/ITO device was 102 times higher than that of the Al/starch/ITO device. However, the switching current ratio of the Al/starch: GQDs/ITO device was further increased, and the set voltage was reduced (−0.75 V) after the introduction of the PMMA layer. The introduction of GQDs and PMMA layers can regulate the formation process of conductive filaments in the device and significantly improve the electrical performance of the memristor. [ABSTRACT FROM AUTHOR]

As artificial synapse devices, memristors have attracted widespread attention in the field of neuromorphic computing. In this paper, Al/polymethyl methacrylate (PMMA)/egg albumen (EA)–graphene quantum dots (GQDs)/PMMA/indium tin oxide (ITO) electrically/optically tunable biomemristors were fabricated using the egg protein as a dielectric layer. The electrons in the GQDs were injected from the quantum dots into the dielectric layer or into the adjacent quantum dots under the excitation of light, and the EA–GQDs dielectric layer formed a pathway composed of GQDs for electronic transmission. The device successfully performed nine brain synaptic functions: excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), short-term potentiation (STP), short-term depression (STD), the transition from short-term plasticity to long-term plasticity, spike-timing-dependent plasticity (STDP), spike-rate-dependent plasticity (SRDP), the process of learning, forgetting, and relearning, and Pavlov associative memory under UV light stimulation. The successful simulation of the synaptic behavior of this device provides the possibility for biomaterials to realize neuromorphic computing. [ABSTRACT FROM AUTHOR]

Three novel conjugated polymers based on 9,9′‐dioctylfluorene unit and isoindolo[2,1‐a]benzimidazol‐11‐one with different fluorine substituents (0, 2 and 4) were synthesized. PLED and resistive memory devices based on these polymers were prepared consequently. PLED based on four‐fluorinated polymer showed the highest maximum brightness of 3192 cd m−2 with almost 5‐fold increase of current efficiency 8‐fold increase of external quantum efficiency compared to that of the other two, and all the PLEDs exhibited good emission stability with no noticeable change of electroluminescence even under high voltage of 10 V. The memory device of doubly‐fluorinated polymer exhibited ternary flash behavior with threshold voltages below −2.5 V, while device of four‐fluorinated polymer possessed ON/OFF current ratio above 104. Impact of fluorine substitutions on the performance of devices were briefly investigated. The results revealed that the improvement of device performance might not scale with the increasing number of fluorine substitutions, and the four‐fluorine‐substituted polymer and doubly‐fluorinated polymer could be encouraging materials for applications of PLED and resistive memory device and worth of further design of other new polymer systems. [ABSTRACT FROM AUTHOR]

We report the application of graphene oxide (GO) as the active layer of memory devices. The indium-tin-oxide/GO/Al devices present the ternary write-once-read-many times resistive switching memory, and retain the data information for 3 × 1 0 5 s. In the OFF states, the I – V characteristics in the applied voltage dominantly followed the space-charge-limited-current behaviors. The intermediate resistance state was attributed to the thermionic emission mechanism. In the ON state, the curve in the applied voltage range was related to an Ohmic mechanism. The sandwich structure, ITO/GO/Al resistive switching device, was fabricated. The as-fabricated devices exhibit nonvolatile ternary WORM features memory with retention performance of 3 × 1 0 5 s. The ternary WORM memory of ITO/GO/Al devices open up the door to the possibility of ultrahigh density data storage of high performance nonvolatile memory devices at low cost. [ABSTRACT FROM AUTHOR]

Resistive memory is one of the important components for building neuromorphic systems, which can be used as artificial synapses to transmit information. Natural biomaterials are naturally degradable materials, and artificial synaptic devices fabricated from them are particularly important for sustainable green electronics development. Here, on the basis of soybean material as a dielectric layer, we embed gold nanoparticles into it to obtain better memory properties. The switching current ratio of the resistive memory after embedding gold nanoparticles is increased, up to 105, which avoids the possibility of misreading errors during data storage and provides a powerful condition for realizing multilevel behavior. In addition, the device was also demonstrated to simulate the synaptic potentiation/depression function, and the results indicated that the high-performance soybean resistive memory has high-density data storage and exhibits great potential in applications as artificial synapses. • Au nanoparticles are doped in the soybean dielectric layer, which increases the switching current ratio of the device. • By changing the method of limiting the current, 4-bit storage can be achieved to improve the storage density of the device. • Applying excitations to the device can successfully simulate synapses. [ABSTRACT FROM AUTHOR]

To further improve the sensitivity temperature characteristics of pressure sensor, a kind of pressure sensor taking nanopolysilicon thin films as piezoresistors is proposed in this paper. On the basis of the microstructure analysis by X-ray diffraction (XRD) and scanning electron microscope (SEM) tests, the preparing process of nanopolysilicon thin films is optimized. The effects of film thickness and annealing temperature on the micro-structure of nanopolysilicon thin films were studied, respectively. In order to realize the measurement of external pressure, four nanopolysilicon thin films resistors were arranged at the edges of square silicon diaphragm connected to a Wheatstone bridge, and the chip of the sensor was designed and fabricated on a orientation silicon wafer by microelectromechanical system (MEMS) technology. Experimental result shows that when = 6.80 mA, the sensitivity of the sensor PS-1 is 0.308 mV/kPa, and the temperature coefficient of sensitivity (TCS) is about −1742 ppm/C in the range of −40-140C. It is possible to obviously improve the sensitivity temperature characteristics of pressure sensor by the proposed sensors. [ABSTRACT FROM AUTHOR]

Al/PMMA/SY : GQDs/PMMA/ITO devices with multilayer structures were fabricated by imbedding PMMA at both ends of soybean (SY) and graphene quantum dot (GQD) dielectric layers, which not only improved the stability of the devices but also reduced the threshold voltage and power consumption. A single unit of the device can complete the logical "AND" and "OR" operations to realize the memory calculation, which provides a new way to overcome the memory bottleneck of computer systems. [ABSTRACT FROM AUTHOR]

Al/PMMA/CS/PMMA/ITO structure devices are fabricated using polymethyl methacrylate (PMMA) and chitosan (CS) as dielectric layer materials. Its electrical characteristics and conductive mechanism are studied using its own physical characteristics to build a memristor true random number generator (TRNG). The generated true random sequence is optimized by a field programmable gate array (FPGA), and the optimized random number sequence is tested by the National Institute of Standards and Technology (NIST) to analyze its randomness. The pipeline structure is introduced to optimize the whole image encryption system, and the optimized random number sequence is used to realize image encryption inside the FPGA. Then, the encrypted image is displayed on a liquid crystal display (LCD) screen to realize random number generation and image encryption of all hardware. Finally, the encrypted image is analyzed. [ABSTRACT FROM AUTHOR]

Electronic devices based on biological materials have shown great application potential in many fields, so they have become a hot topic of research. In this paper, biomaterial soybean and one-dimensional nanomaterial multiwalled carbon nanotubes (MWCNTs) were mixed as the active layer to fabricate Al/soybean MWCNT/ITO/glass memristor devices. The device shows a bipolar resistive switching characteristic, and the retention time exceeds 104 s. By adjusting the concentration of MWCNTs, the ON/OFF current ratio can be modulated in the range of 1–104, and the endurance of the device is enhanced by increasing the MWCNT concentration. By changing the compliance current, the device can realize multilevel storage and improve the storage density. The write-read-erase-read process can still be completed under low voltage (±2 V), which opens up a new way for the fabrication of low power consumption memristor devices. In addition, the device successfully simulates the potentiation and suppression behavior of biological synapses, showing promise for making new breakthroughs in the field of implantable neural system research for biological memristor-based artificial synapses. [Display omitted] • By adding MWCNTs into soybean, the ON/OFF current ratio can be adjusted in the range of 1–104. • The Al/soybean:MWCNT/ITO device can still complete write-read-erase-read at ±2 V. • By changing the compliance current, 4-bitstorage can be achieved to improve the storage density of the device. • Applying pulses to the device can successfully simulate the potentiation and depression behavior of synapses. [ABSTRACT FROM AUTHOR]

The logic gate is the basic unit of a digital circuit structure. The operation, memory, I/O, and other reading and writing functions of computer systems require logic circuits. Logic gates based on resistive memory can make existing integrated circuits denser, smaller, faster, and use fewer devices. In this paper, Al/polymethyl methacrylate (PMMA)/egg albumen (EA):Au nanoparticles/PMMA/Al multilayer biological resistive random access memory was prepared based on the natural biological material—egg albumen (EA). The device has bipolar switching behavior, a higher switching current ratio, a lower threshold voltage, and better stability. A circuit based on auxiliary logic is constructed using this device, and the logic functions of AND, OR, NOT, NAND, and NOR are realized. This device provides an effective potential solution for implementing high-performance electronic devices and large-scale integrated circuits. [ABSTRACT FROM AUTHOR]

Biomaterials have attracted attention as a major material for biodegradable and transient electronic devices. In this work, biocompatible gelatin-doped graphene quantum dot films are reported as active layer switching memories with good electrical properties and physical transient properties. Such nonvolatile memory devices have write-once-read-many electrical properties and a concentrated distribution of low-resistance and high-resistance states. It provides a solution for the current obstacle of resistive memory storage and computing integration. Based on the sensitivity of the device to ultraviolet light, the "OR gate" logic operation is completed. Furthermore, the active layer can be dissolved in deionized water within 15 min, and the gelatin substrate-based device can be destroyed immediately in water, indicating the potential biodegradation and physical transient properties of our fabricated device. Biocompatible memory devices are environmentally friendly, sustainable for safe storage, and low-cost, making them ideal for storage applications. [ABSTRACT FROM AUTHOR]

In this paper, a floating-gate flexible nonvolatile memory is reported that is composed of natural biological materials, namely, silkworm hemolymph, graphene quantum dots as the floating-gate layer, and polymethyl methacrylate (PMMA) as the insulating layer. The device has a high ON/OFF current ratio (4.76 × 106), a low setting voltage (<−1.75 V), and good durability and retention ability. The device has two storage characteristics, namely, Flash and WORM, which can be effectively and accurately controlled by adjusting the limiting current during device setting. The resistance switching characteristics are the result of the formation and fracture of conductive filaments. The floating-gate flexible bioresistive random access memory prepared in this paper provides a new idea for the development of multifunctional and biocompatible flexible memory. [ABSTRACT FROM AUTHOR]

Physical transient electronics have attracted more attention as the basis for building green electronics and biomedical devices. However, there are difficulties in selecting materials for the fabricated devices to take into account both biodegradability and high performance. In this paper, a physically transient resistive random-access memory (RRAM) device was fabricated by using egg protein and graphene quantum dot composites as active layers. The sandwich structure composed of Al/EA:GQD/ITO shows a good write-once-multiple-read memory characteristic, and the introduced GQD improves the switching current ratio of the device. By using the sensitivity of GQDs to ultraviolet light, the logic operation of the "OR gate" is completed. Furthermore, the device exhibits a physical transient behavior and good biodegradability due to the dissolution behavior in deionized water. These results suggest that the device is a favorable candidate for the construction of memory elements for transient electronic systems. [ABSTRACT FROM AUTHOR]

Organic-resistance random access memory has high application potential in the field of next-generation green nonvolatile memory. Because of their biocompatibility and environmental friendliness, natural biomaterials are suitable for the fabrication of biodegradable and physically transient resistive switching memory devices. A flexible memory device with physically transient properties was fabricated with silver ions and egg albumen composites as active layers, which exhibited characteristics of write-once-read-many-times (WORM), and the incorporation of silver ions improved the ON/OFF current ratio of the device. The device can not only complete the logical operations of "AND gate" and "OR gate", but its active layer film can also be dissolved in deionized water, indicating that it has the characteristics of physical transients. This biocompatible memory device is a strong candidate for a memory element for the construction of transient electronic systems. [ABSTRACT FROM AUTHOR]

Bistable electrical switching and nonvolatile memory devices with the configuration of indium tin oxide (ITO)/active layer/aluminum (Al) are reported. The active layer were prepared from the mixed compositions of 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole, (PBD) and poly( N -vinylcarbazole) (PVK). The as-fabricated ITO/PBD:PVK/Al sandwiched devices exhibited rewriteable flash memory property. Due to the strong interaction between oxadiazole acceptor and carbazole donor, the devices demonstrate excellent performance. The memory devices can operate over a small voltage range, the absolute value of switching-on threshold voltage is less than 1 V and the switching-off threshold voltage is less than 3.5 V. The ON/OFF ratio of current switches in the range of 10 4 –10 2 during the variation of applied voltage and the two different resistance states can be maintained over 4 h. [ABSTRACT FROM AUTHOR]

[Display omitted] • The asymmetric gate design was used to suppress the inherent ambipolarity of graphene. • Combined with chemically doped method to suppress the off state current of graphene transistors. • The on-state current is increased while the off-state current is effectively suppressed. • The on/off ratio is increased by nearly two orders of magnitude compared with the normal gate structure device. • Better threshold swing and smaller threshold voltage are obtained. Graphene is considered a promising transistor component for future integrated circuits. Due to high operating speed and low power consumption, high on/off ratio and low off state current are ideal transistors. However, due to the inherent ambipolarity of graphene, a significant ambipolarity behavior with a fairly high off state current is usually observed in graphene transistors. In this work, an asymmetric gate design combined with a chemically doped method to suppress the ambipolarity of graphene transistors was reported. Thus, the off-state current is effectively reduced and the on-state current is increased. The on/off ratio is increased by nearly two orders of magnitude. Compare to the normal gate structure device, better threshold swing and smaller threshold voltage are obtained. [ABSTRACT FROM AUTHOR]

• A resistive random access memory with biodegradability and biocompatibility is fabricated. • The device has a high ON/OFF current ratio of 5.22 × 105. • The single memory cell of this device has multilevel (8 levels, 3 bits) data storage capacity. • The device can simulate the potentiation and depression of synapses. [Display omitted] In this study, silkworm body fluid (SF), a natural biological material, was compounded with gold nanoparticles (Au NPs) to form a dielectric layer, and the biodegradable resistive random access memory (RRAM) of Al/SF:Au NPs/indium tin oxide (ITO) was fabricated. The experimental results show that embedding Au NPs increases the ON/OFF current ratio of the Al/SF:Au NPs/ITO device to 5.22 × 105. The resistances of the high resistance and low resistance states of the Al/SF:Au NPs/ITO device are well maintained, reaching 104 s. These devices can be easily fabricated using solution-based processes on substrates at room temperature, and they have reliable data storage capability. Because the compliance current is controlled, a single memory cell of a device based on SF:Au NPs has a multilevel (8 levels, 3 bits) resistance state for high-density storage, enabling multilevel data storage. Application of the device in simulating neurobehavior is further explored, and potentiation and depression of the simulated synapse can be achieved by applying pulses to the device. SF:Au NP-based RRAM shows great potential in multilevel data storage and neuromorphic computing. RRAM based on natural biomaterials has the advantages of biocompatibility, biodegradability and low cost, and it provides an important step toward the future development of bioelectronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Memristor based on Co-Ni LDHs hybrid nanosheets is reported. • Devices exhibit nonvolatile resistance switching behavior. • Multiple progressive resistance switches could be achieved. • Memristors were used to simulate synaptic function in biology. • O vacancy is the physical mechanism of the resistance switch behavior. Because of its excellent electrical properties and promising application prospects, two-dimensional materials have attracted extensive research interests of researchers. Among them, Co-Ni layered double hydroxide (LDH) has semiconductor properties and has been widely studied in super capacitor. However, there are few reports about 2D Co-Ni LDHs materials as memristors. In this work, a memristor based on Co-Ni LDHs hybrid nanosheets is reported. After electroforming, Al/Co-Ni LDHs/Al devices exhibit nonvolatile resistance switching behavior. More importantly, multiple progressive resistance switches could be achieved by adjusting the duration or amplitude of the applied pulse (less than the set threshold voltage to prevent a sudden setting process). Given its gradual resistive switching, Co-Ni LDHs-based memristors were used to simulate synaptic function in biology, including: "learning" and "forgetting" process, STP and LTP, PPF characteristics, and STDP. By studying the microstructure, it is proposed that the O vacancy is the physical mechanism of the resistance switch behavior. This work reveals that Co-Ni LDH nanosheets have excellent application potential in memristors, which may open the door to more functions and applications. [ABSTRACT FROM AUTHOR]

In this paper, a tuneable multilevel data storage bioresistive memory device is prepared from a composite of multiwalled carbon nanotubes (MWCNTs) and egg albumen (EA). By changing the concentration of MWCNTs incorporated into the egg albumen film, the switching current ratio of aluminium/egg albumen:multiwalled carbon nanotubes/indium tin oxide (Al/EA:MWCNT/ITO) for resistive random access memory increases as the concentration of MWCNTs decreases. The device can achieve continuous bipolar switching that is repeated 100 times per cell with stable resistance for 104 s and a clear storage window under 2.5 × 104 continuous pulses. Changing the current limit of the device to obtain low-state resistance values of different states achieves multivalue storage. The mechanism of conduction can be explained by the oxygen vacancies and the smaller number of iron atoms that are working together to form and fracture conductive filaments. The device is nonvolatile and stable for use in rewritable memory due to the adjustable switch ratio, adjustable voltage, and nanometre size, and it can be integrated into circuits with different power consumption requirements. Therefore, it has broad application prospects in the fields of data storage and neural networks. [ABSTRACT FROM AUTHOR]

In this study, a flexible bioresistive memory with an aluminum/tussah hemolymph/indium tin oxide/polyethylene terephthalate structure is fabricated by using a natural biological material, tussah hemolymph (TH), as the active layer. When different compliance currents (Icc) are applied to the device, it exhibits different resistance characteristics. When 1 mA is applied in the positive voltage range and 100 mA is applied in the negative voltage range, the device exhibits bipolar resistive switching behavior. Additionally, when 1 mA is applied in both the positive- and negative-voltage ranges, the device exhibits write-once-read-many-times (WORM) characteristics. The device has good endurance, with a retention time exceeding 104 s. After 104 bending cycles, the electrical characteristics remain constant. This memory device can be applied for "AND" and "OR" logic operations in programmable logic circuits. The prepared flexible and transparent biomemristor made of pure natural TH provides a promising new approach for realizing environmentally friendly and biocompatible flexible memory, nerve synapses, and wearable electronic devices. [ABSTRACT FROM AUTHOR]

In order to improve the output sensitivity of the piezoelectric acceleration sensor, this paper proposed a high sensitivity acceleration sensor based on a piezoelectric metal oxide semiconductor field effect transistor (MOSFET). It is constituted by a piezoelectric beam and an N-channel depletion MOSFET. A silicon cantilever beam with Pt/ZnO/Pt/Ti multilayer structure is used as a piezoelectric beam. Based on the piezoelectric effect, the piezoelectric beam generates charges when it is subjected to acceleration. Due to the large input impedance of the MOSFET, the charge generated by the piezoelectric beam can be used as a gate control signal to achieve the purpose of converting the output charge of the piezoelectric beam into current. The test results show that when the external excitation acceleration increases from 0.2 g to 1.5 g with an increment of 0.1 g, the peak-to-peak value of the output voltage of the proposed sensors increases from 0.327 V to 2.774 V at a frequency of 1075 Hz. The voltage sensitivity of the piezoelectric beam is 0.85 V/g and that of the proposed acceleration sensor was 2.05 V/g, which is 2.41 times higher than the piezoelectric beam. The proposed sensor can effectively improve the voltage output sensitivity and can be used in the field of structural health monitoring. [ABSTRACT FROM AUTHOR]

We used graphene oxide (GO) and egg albumen (EA) to fabricate bipolar resistance switching devices with indium tin oxide (ITO)/GO/EA/GO/Aluminum (Al) and ITO/EA/Al structures. The experimental results show that these ITO/GO/EA/GO/Al and ITO/EA/Al bio-memristors exhibit rewritable flash memory characteristics. Comparisons of ITO/GO/EA/GO/Al devices with 0.05 ωt %, 0.5 ωt %, and 2 ωt % GO in the GO layers and the ITO/EA/Al device show that the ON/OFF current ratio of these devices increases as the GO concentration decreases. Among these devices, the highest switching current ratio is 1.87 × 103. Moreover, the RESET voltage decreases as the GO concentration decreases, which indicates that GO layers with different GO concentrations can be adopted to adjust the ON/OFF current ratio and the RESET voltage. When the GO concentration is 0.5 ωt %, the device can be switched more than 200 times. The retention times of all the devices are longer than 104 s. [ABSTRACT FROM AUTHOR]

A three-axis accelerometer with a double L-shaped beams structure was designed and fabricated in this paper, consisting of a supporting body, four double L-shaped beams and intermediate double beams connected to two mass blocks. When applying acceleration to the accelerometer chip, according to the output voltage changes of three Wheatstone bridges constituted by twelve piezoresistors on the roots of the beams, the corresponding acceleration along three axes can be measured based on the elastic force theory and piezoresistive effect. To improve the characteristics of the three-axis accelerometer, we simulated how the width of the intermediate double beams affected the characteristics. Through optimizing the structure size, six chips with different widths of intermediate double beams were fabricated on silicon-on-insulator (SOI) wafers using micro-electromechanical systems (MEMS) technology and were packaged on printed circuit boards (PCB) by using an electrostatic bonding process and inner lead bonding technology. At room temperature and VDD = 5.0 V, the resulting accelerometer with an optimized size (w = 500 μm) realized sensitivities of 0.302 mV/g, 0.235 mV/g and 0.347 mV/g along three axes, with a low cross-axis sensitivity. This result provides a new strategy to further improve the characteristics of the three-axis accelerometer. [ABSTRACT FROM AUTHOR]

A micro-pressure sensor with an isosceles trapezoidal beam-membrane (ITBM) is proposed in this paper, consisting of a square silicon membrane, four isosceles trapezoidal beams (ITBs) and four piezoresistors. To investigate how the elastic silicon membrane affects pressure sensitive characteristics, simulation models based on ANSYS 15.0 software were used to analyze the effect of structural dimension on the characteristics of pressure sensor. According to that, the chips of micro-pressure sensors were fabricated by micro-electro-mechanical system (MEMS) technology on a silicon wafer with 〈 1 0 0 〉 orientation. The experimental results show that the proposed sensor achieves a better sensitivity of 9.64 mV/kPa and an excellent linearity of 0.09%F.S. in the range of 0–3.0 kPa at room temperature and a supply voltage of 5.0 V, with a super temperature coefficient of sensitivity (TCS) about - 2180 ppm/ ∘ C from −40 ∘ C to 85 ∘ C and low pressure measurement less than 3.0 kPa. [ABSTRACT FROM AUTHOR]

A magnetic field sensor with a new concentrating-conducting magnetic flux structure (CCMFS) is proposed in this paper, using a silicon-on insulator (SOI) Hall element fabricated by complementary metal oxide semiconductor (CMOS) technology as a magnetic sensitive unit. By fixing the CCMFS above the Hall element packaged on a printed circuit board (PCB) based on inner-connect wire bonding technology, a non-magnetized package can subsequently be obtained. To analyze the inner magnetic field vector distribution of the CCMFS, a simulation model was built based on a finite element software, where the CCMFS was processed using Ni-Fe alloys material by a low speed wire-cut electric discharge technology. The test results showed that the measurement of magnetic fields along a sensitive and a non-sensitive axis can be achieved when VDD = 5.0 V at room temperature, with magnetic sensitivities of 122 mV/T and 132 mV/T in a testing range from −30 mT to 30 mT, respectively. This study makes it possible to not only realize the detection of magnetic field, but also to significantly improve the sensitivity of the sensor along a non-sensitive axis. [ABSTRACT FROM AUTHOR]

To research the piezoresistive properties of SiC thin films, a testing structure consisting of a cantilever beam, SiC thin films piezoresistors and a Cr/Pt electrode is proposed in this paper. The chips of testing structure were fabricated by micro-electro-mechanical system (MEMS) technology on a silicon wafer with 〈 100 〉 orientation, in which SiC thin films were deposited by using radio-frequency (13.56 MHz) magnetron sputtering method. The effect of sputtering power, annealing temperature and time on the microstructure and morphology of the SiC thin films were investigated by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). It indicates that a good continuity and uniform particles on the SiC thin film surface can be achieved at sputtering power of 160 W after annealing. To verify the existence of Si–C bonds in the thin films, X-ray photoelectron spectroscopy (XPS) was used. Meanwhile, the piezoresistive properties of SiC thin films piezoresistors were measured using the proposed cantilever beam. The test result shows that it is possible to achieve a gauge factor of 35.1. [ABSTRACT FROM AUTHOR]

In this study, Al/Scindapsus aureus (SA)/ITO and Al/polymethyl methacrylate (PMMA)/SA:graphene quantum dots (GQDs)/PMMA/ITO devices of different memory types and with different electrical characteristics were fabricated based on SA. Al/SA/ITO devices have bipolar resistance switching characteristics with a switching current ratio of 103 and a holding time of more than 104 s. When an Al/SA/ITO device is fabricated on a flexible substrate, the device still maintains stable resistance switching characteristics. After the addition of GQDs into the dielectric layer, the switching current ratio is increased (>105). Accordingly, Al/PMMA/SA:GQDs/PMMA/ITO resistive memory was fabricated based on SA and GQD composites. Al/PMMA/SA:GQDs/PMMA/ITO/glass devices also show bipolar resistance switching characteristics; a single memory cell can be switched more than 200 times continuously, with the lowest threshold voltage, and the holding time is greater than 2 × 104 s. A cell of the Al/PMMA/SA:GQDs/PMMA/ITO/PET memristors fabricated in this study can exhibit both bipolar and write-once-read-many-times (WORM) memory characteristics under different limited currents. The results show that SA is a promising biomaterial for memory fabrication, and this research opens up a new avenue for the application and development of memory with multiple functions and flexible wearable electronic devices. [Display omitted] • Flexible resistive memory with different storage properties is fabricated based on the biomaterial Scindapsus aureus. • By doping with graphene quantum dots, the switching current ratio is increased, and the data misreading rate is reduced. • The device has more stable resistance switching behavior and a reduced set voltage, enabling low-power storage. • The devices fabricated on PET can exhibit both flash and WORM memory characteristics under different limited currents. [ABSTRACT FROM AUTHOR]

A silicon magnetic sensitive transistor (SMST) with the negative resistance oscillation phenomenon is presented in this paper. The SMST of cubic structure is composed of three regions and three electrodes (E, C and B). Two of the regions (collector region and base region) are designed on the top surface of the SMST, and the emitter region is designed at the bottom of the SMST. Using microelectromechanical system (MEMS) technology, the chip is fabricated on 〈 1 0 0 〉 orientation p-type silicon (near intrinsic) wafer and packaged on printed circuit board (PCB). When collector voltage (V ce ) and the base injecting current (I b ) are a certain value, the experimental results show that the collector current (I c ) attains negative resistance oscillation phenomenon and it is influenced by the external magnetic field (B) and temperature (T). Based on the effect of deep-level impurities on the carrier net recombination rate, theoretical analysis demonstrates that the deep-level impurities are the main factors of the appearance for oscillations phenomenon. [ABSTRACT FROM AUTHOR]

The humidity sensor based on silicon substrate is presented in this paper, which consists of anodic aluminum oxide (AAO) film and interdigitated electrodes. By using electro-chemical oxidizing technique, AAO film with high porosity is fabricated on the silicon substrate. Under optimal oxidization condition, pore diameter of 37–79 nm and depth about 7μm is achieved. Interdigitated electrodes are fabricated on the top of AAO film by vacuum evaporation deposition method. The results show that the sensor has different nonlinear response in whole range of relative humidity (RH). Moreover, it has almost linear relationship between the capacitance and RH at high RH from 75% to 95%. The highest sensitivity is obtained 613 pF/%RH at 1 kHz, which is much higher than other frequencies. [ABSTRACT FROM AUTHOR]

In this paper, a force sensor based on piezoelectric effect of Li-doped ZnO (LZO) thin films was presented, which constituted by Pt/LZO/Pt/Ti functional layers and Si cantilever beam. The chips were designed and fabricated by micro electro-mechanical system (MEMS) technology on silicon wafer with 〈100〉 orientation. In this sandwich structure, the top electrode (TE) was Pt and bottom electrode (BE) was Pt/Ti, LZO piezoelectric thin films were prepared by radio frequency (RF) magnetron sputtering method. The microstructure and morphology were analyzed through X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM), analysis results shows that the LZO thin films with highly c-axis orientation and uniform grain size distribution under sputtering power of 220 W. The experimental results show, when external force loaded on the tip of the beam, the output voltage (Vpp) was 280.3 mV at external force of 5 N, the sensitivity of the proposed sensor was 46.1 mV/N in the range of 1–5 N. [ABSTRACT FROM AUTHOR]

Two-dimensional NiAl layered double hydroxides (LDHs) were synthesized by urea hydrolysis method. Considering its unique layered structure and high-speed carrier transfer channel, NiAl-LDHs were applied to the active layer of memristor through spin coating process. It is found that the Al/NiAl-LDHs/Al memristor exhibits unipolar resistance switching characteristics, which resistive switching mechanism is attributed to formation and fusing of conductive filaments controlled by oxygen vacancies. Based on this Al/NiAl-LDHs/Al memristor, a D -type latch was constructed. A memtransistor with Si/SiO 2 /graphene oxide (GO)/Al/NiAl-LDHs/Al structure was built by connecting Al/NiAl-LDHs/Al memristor in series on the drain electrode of GO transistor. The memtransistor exhibits excellent gate controllability and resistive switching characteristics. Combined with its characteristics, we used the memtransistor to build a D -trigger and verify its memory logical function. The result shows the great potential of layered bimetallic hydroxide materials in the field of resistance switching memory and memory computing. • The unipolar resistive switching characteristics of NiAl-LDHs memristor were investigated. • A D -type latch was constructed using NiAl-LDHs memristor, which logical function was verified. • A memtransistor was built by connecting Al/NiAl-LDHs/Al memristor in series on the drain electrode of GO transistor. • A D -trigger was constructed by the memtransistor, which exhibits excellent memory logical function. [ABSTRACT FROM AUTHOR]

A novel multilevel resistive switching was observed in epoxy methacrylate resin (EMAR) and carbon nanotubes (CNTs) composite films fabricated by spin coating method. The fabricated devices demonstrated the rewritable nonvolatile memory characteristics. More significantly, the memory device based on EMAR+CNTs composite exhibits multilevel stable conductivity states with stable intermediate resistance states in response to the applied voltage. By setting different compliance current and content of CNTs in composite film, the multilevel ON-states and even the multilevel OFF-states have been observed in our memory device. As fabricated devices exhibited multilevel resistive switching with stable resistance ratio between different resistance states having good data retention and endurance characteristics. It offers a novel design strategy for solution processable multilevel data storage. [ABSTRACT FROM AUTHOR]

The memory characteristic based on nonvolatile tuning behavior in indium tin oxide/poly( N -vinylcarbazole)/aluminum (ITO/PVK/Al) was investigated, the different memory behaviors were first observed in PVK film as the film thickness changing. By control of PVK film thickness with different spinning speeds, the nonvolatile behavior of ITO/PVK/Al sandwich structure can be tuned in a controlled manner. Obviously different nonvolatile behaviors, such as (i) flash memory behavior and (ii) write-once-read-many times (WORM) memory behavior are from the current–voltage ( I – V ) characteristics of the PVK films. The results suggest that the film thickness plays a key part in determining the memory type of the PVK. [ABSTRACT FROM AUTHOR]

[Display omitted] • A heterostructure consisting of two dimensional nanocomposite has been studied. • Transistor and memristor characteristics of heterostructure have been investigated. • By constructing schottky barrier, the current and threshold voltage were modulated. • Resistive switching behavior of heterostructure has gate control function. A novel heterostructure consisting of two dimensional nanocomposite Ni-Co layered double hydroxides (Ni-Co LDHs) and graphene with adjustable Fermi levels has been studied. Transistor characteristics and memristor properties of the Ni-Co LDHs/graphene oxide heterostructure have been investigated. In consideration of Fermi energy of graphene is modulated under external applied voltage, by constructing Schottky barrier, the current and threshold voltage of the device were effectively modulated by applied different gate voltage. The Ni-Co LDHs/graphene oxide heterostructure device exhibits a good endurance property, as well as data retention property is up to 104 s. The resistive switching characteristics are achieved via the conductive filament. The performance and scheme design of this device have a good prospect in memory applications. [ABSTRACT FROM AUTHOR]

Nanocarbon materials have the advantages of biocompatibility, thermal stability and chemical stability and have shown excellent electrical properties in electronic devices. In this study, Al/MWCNT:GQD/ITO memristors with rewritable nonvolatile properties were prepared based on composites consisting of multiwalled carbon nanotubes (MWCNTs) and graphene quantum dots (GQDs). The switching current ratio of such a device can be tuned in two ways. Due to the ultraviolet light sensitivity of GQDs, when the dielectric material is illuminated by ultraviolet light, the charge capture ability of the GQDs decreases with an increasing duration of illumination, and the switching current ratio of the device also decreases with an increasing illumination duration (103–10). By exploiting the charge capture characteristics of GQDs, the trap capture level can be increased by increasing the content of GQDs in the dielectric layer. The switching current ratio of the device increases with increasing GQD content (10–103). The device can be programmed and erased more than 100 times; the programmable switching state can withstand 105 read pulses, and the retention time is more than 104 s. This memristor has a simple structure, low power consumption, and enormous application potential for data storage, artificial intelligence, image processing, artificial neural networks, and other applications. [ABSTRACT FROM AUTHOR]

A kind of devices Pt/Ag/ZnO:Li/Pt/Ti with high resistive switching behaviors were prepared on a SiO2/Si substrate by using magnetron sputtering method and mask technology, composed of a bottom electrode (BE) of Pt/Ti, a resistive switching layer of ZnO:Li thin film and a top electrode (TE) of Pt/Ag. To determine the crystal lattice structure and the Li-doped concentration in the resulted ZnO thin films, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) tests were carried out. Resistive switching behaviors of the devices with different thicknesses of Li-doped ZnO thin films were studied at different set and reset voltages based on analog and digital resistive switching characteristics. At room temperature, the fabricated devices represent stable bipolar resistive switching behaviors with a low set voltage, a high switching current ratio and a long retention up to 104 s. In addition, the device can sustain an excellent endurance more than 103 cycles at an applied pulse voltage. The mechanism on how the thicknesses of the Li-doped ZnO thin films affect the resistive switching behaviors was investigated by installing conduction mechanism models. This study provides a new strategy for fabricating the resistive random access memory (ReRAM) device used in practice. [ABSTRACT FROM AUTHOR]