Electrical Bistable Device Research Articles

MoS2 nanosheets functionalized with ferrocene-containing polymer via SI-ATRP for memristive devices with multilevel resistive switching

Designing and preparing memristive materials with multilevel memristive switching characteristics is an effective strategy for improving the data storage capacity of devices. Herein, by grafting a ferrocene-containing polymer (PFMMA) from molybdenum disulfide nanosheets (MoS2 NSs) via polydopamine (PDA)-mediated surface-initiated atom transfer radical polymerization (SI-ATRP), we synthesized a novel two-dimensional nanomaterial, MoS2-PDA-PFMMA. The fabricated Al/MoS2-PDA-PFMMA/ITO sandwich-structured electronic device exhibited asymmetric multilevel resistive switching characteristics, which should give it a larger data storage capacity compared with traditional electrical bistable memristive devices. This work realized multilevel resistive switching in the device by material structure design, which opens up a new perspective for developing memristive devices with ultra-large data storage capacities.

Role of Hydroxyl on Conductivity Switching of Poly(ethylene oxide)/TiO2 Electrical Bistable Devices

Conductivity switching in a semiconductor nanoparticle/polymer composite electrical bistable device is typically associated with the electron trapping between the semiconductor trap center and the polymer matrix. However, the switch‐on mechanism is still not clear, and even in the same metal oxide (MO) nanoparticle/polymer system, two different models are applied to explain the conductivity switching mechanisms, including Fowler–Nordheim (F–N) tunneling current and trapped charge‐limit‐current (TCLC). Therefore, the analysis of the conductivity‐switching mechanism in MO/polymer composite devices is crucial to facilitate technology development. Herein, poly(ethylene oxide) (PEO) films are deposited on top of the various TiO2 films, and the two different electrical bistabilities are observed. The corresponding conductivity‐switching mechanisms are found to be significantly related to the different TiO2 surface traps. The results demonstrate that the F–N tunneling current dominates in the devices where a large number of hydroxyl groups are present in TiO2, whereas, after removing the hydroxyl groups from the device, the switching‐on current is dominated by the TCLC mechanism.

Role of nanoparticle surface defects in the conduction mechanism of polymer–nanoparticle electrical bistable devices

Surfactant induced conduction mechanism transition from TCLC to FN tunnelling in PEO : ZnO-NP electrical bistable devices.

基于PVP和PbSe 三维自组装超晶格复合体系的电双稳器件

基于PVP和PbSe 三维自组装超晶格复合体系的电双稳器件

Electrical bistable properties of nonvolatile memory device based on hybrid ZCIS NCs:PMMA film

A write-once–read–many-times (WORM) electrical bistable device was fabricated utilizing hybrid quaternary Zn-Cu-In-S nanocrystals (ZCIS NCs) and poly(methyl methacrylate) (PMMA) as active layer. A low turn-on voltage of 1.0V and the maximum ON/OFF current ratio of 4×103 were found from current-voltage (I-V) characteristics. The current stability in the ON and OFF state has a fluctuation loss less than 5% in the measurement duration of 104s. The electron transport and memory mechanism are described based on the fitted I-V curves and the energy band diagrams. The conduction models in the OFF state from 0V to 1.1V are described as thermionic emission (TE), space-charge-limited current (SCLC) and Fowler–Nordheim (FN) tunneling, respectively. And the Ohmic conduction dominates when the device is transited to the ON state at the voltage over 1.1V. The high-density defects in quaternary ZCIS NCs and the high barrier between ZCIS NCs and the PMMA are considered to contribute to the electron retention behavior. For device performance optimization, an additional PMMA layer is pre-deposited on the ITO substrate surface. The 50% reduction at turn-on voltage and over 50 times enhancement in ON/OFF ratio are reasonably attributed to the better film quality and decreased series resistance from the decrease of root-mean-square average surface roughness (RMS) of the ITO surface from 0.877 to 0.216nm. The better retention capacity is considered to relate to thickened tunnel barrier by PMMA inserted layer.

Electrical mechanisms of bi-stable memory devices based on an Al/PVK:ZnO NPs/ITO structure with different ZnO NPs annealing temperatures

We reported on the influence of the structural properties of zinc oxide nanoparticles (ZnO NPs) on electrical bi-stable device based on an aluminum/poly(9-vinylcarbazole):ZnO NPs/indium-tin oxide structure. ZnO NPs were synthesized by simple precipitation method with different annealing temperatures. When annealing temperature was increased, the ZnO NPs crystallite increased and the ZnO NPs gradually changed shape from nanostar-like to nanospherical. The structural parameters, such as the crystallite size of ZnO NPs and dislocation density, can be calculated from the XRD spectra. The effect of ZnO NPs annealing temperature on memory properties can be measured by current-voltage characteristics and retention time measurements. The maximum ON/OFF current ratio for the memory devices was about 103 and the devices exhibited the Write-Once, Read-Many (WORM) memory type. The operating mechanisms of the memory device were analyzed using theoretical models, in which electrons trapping in the ZnO NPs and electrons tunneling among a PVK matrix by direct tunneling process were discussed.

基于PVK/PbS纳米晶有机无机复合薄膜电双稳器件性能研究

基于PVK/PbS纳米晶有机无机复合薄膜电双稳器件性能研究

Electrical bistable devices using composites of zinc sulfide nanoparticles and poly-(N-vinylcarbazole)**Project supported by the National Natural Science Foundation of China (Grant No. 61377028), the Natural Science Funds for Distinguished Young Scholar, China (Grant No. 61125505), and the Fundamental Research Funds for the Central Universities, China (Grant No. 2014JBZ009).

N-dodecanethiol capped zinc sulfide (ZnS) nanocrystals were synthesized by the one-pot approach and blended with poly (N-vinylcarbazole) (PVK) to fabricate electrical bistable devices. The corresponding devices did exhibit electrical bistability and negative differential resistance (NDR) effects. A large ON/OFF current ratio of 104 at negative voltages was obtained by applying different amplitudes of sweeping voltage. The observed conductance switching and the negative differential resistance are attributed to the electric-field-induced charge transfer between the nanocrystals and the polymer, and the charge trapping/detrapping in the nanocrystals.

Organic memristive devices based on DNA embedded in silver nanoparticles layer

Two-terminal electrical bistable device is fabricated with structure “Al/deoxyribonucleic acid-cetyltrimethylam- monium bromide/silver nanoparticles/deoxyribonucleic acid-cetyltrimethylammonium bromide/indium tin oxide”, and I-V curves are measured. The results show that the conductivity and the memristive characteristics are significantly improved by the embedding Ag nanoparticles layer. The optimal particle diameters are in a range of 15 - 20 nm, and the maximum on/off current ratio can reach 103. It is also found that I-V characteristic of the device depends on the sweeping voltage amplitude VA. As VA increases, switching voltages (VSET, VRESET) and the on/off current ratio ION/IOFF increase. Furthermore, the transition between high-and low-resistance-state depends on the direction of the applied electric field, which shows that the device possesses polarity.

Electrical bistable properties of hybrid device based on SiO2 modified-ZnO nanoparticles embedded in poly-4-vinyl-phenol

Abstract An electrical bistable device was fabricated by using SiO2 modified-ZnO nanoparticles (NPs) embedded in poly-vinyl-phenol (PVP) polymer as the charge storage medium. Compared to the reference devices with PVP or ZnO NPs embedded in PVP, the proposed device showed improved reproducible electrical bistability. The time maintenance for On/Off states reached 10 4 s , revealing the better environmental stability. The carrier transport mechanism was interpreted by the space-charge-limited-current (SCLC), thermionic emission (TE) and ohmic conduction models. The charge trapping and de-trapping process of ZnO NPs were described based on the energy-band diagram of the device.

PbS纳米晶修饰的ZnO/PVP复合电双稳器件阻变机制

An organic /inorganic composite electrical bistable device with the sandwich structure of ITO / PVP /ZnO nanocrystal(NCs) /PbS nanocrystal(NCs) /PVP /Al was fabricated.Compared with the device structure of ITO /PVP /ZnO NPs /PVP /Al,the ON /OFF ratio of target device was improved by 2 orders of magnitude.The carrier transportation and resistance switching mechanism of device were discussed via I-V characteristics and the energy band structures of the devices.The effective capture /release of electrons could be attributed to the optimization of device structure and modification of ZnO NCs surface by PbS NCs layer.

Electrical bistability in self-assembled hybrid multilayers of phospholipid andnanoparticles

A novel kind of biomolecule-based electrical bistable device composed of phospholipid–CdTenanoparticle multilayered films was demonstrated. The composite film was fabricated by afacile solution-cast method. X-ray reflectivity and transmission electron microscopymeasurements showed the homogeneous distribution of nanoparticles within the lamellarlipid matrix with long-range ordering. Current–voltage scans on the Al/(lipid–nanoparticlecomposite film)/ITO/glass structures at room temperature exhibited an obvious currentbistable phenomenon. Further investigation of such bionanoparticle composite filmpromises to show its importance for applications in future memory nanodevices withtailored performance.

Alternative resistive switching mechanism based on migration of charged counter-ions within conductive polymers

In this paper, an alternative bi-stable resistive switching mechanism for non-volatile organic memory applications is reported. The memory device is formed from a sandwiched structure of Au/polyaniline:poly(4-styrenesulfonic acid) (PANI:PSSH)/ITO and operates via the migration of negatively charged counter-ions (PSS −) within the polymer composite. The electro-statically bonded PSS − within the polymer film segregates at the polymer’s interface upon electrical biasing, serving to disrupt current conduction pathways through the polymer by influencing the resonance state of the conducting main chain. By relocation of this PSS − layer at the polymer interface, electrical conductivity was modulated and an electrical bi-stable device was achieved. The resistive ratio between the ON/OFF states of the device is about 2–3 orders of magnitude, both of which can be read out for up to 500 times with negligible degradation.

Electrical bistability of composite film comprising hyper-branched polymer and gold nanoparticle

A hyper-branched polymer (HPS) with dithiocarbamate (DC) end groups and gold nanoparticle stabilized by HPS (HPSAu) were synthesized. We fabricated a single-layered organic electrical bistable device (OBD). It exhibited a unipolar switching behavior with a negative differential resistance (NDR). When a certain voltage was applied to the pristine state, the device changed irreversibly and began exhibiting bistable conductive states; the equivalent circuit of this device is a parallel circuit comprising one resistance and one capacitor.

Electrical bistable memory device based on a poly(styrene-b-4-vinylpyridine) nanostructured diblock copolymer thin film

This paper describes the performance of a nonvolatile memory device based on a solution-processed poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) diblock copolymer thin film. The Al/PS-b-P4VP/indium tin oxide memory device featuring metal-coordinated 30 nm P4VP cores exhibited an ON/OFF ratio of 2×105, an erase voltage of 0.75 V, a write voltage of −0.5 V, and a retention time of 104 s. The device exhibited a metallic behavior in the ON state, suggesting the formation of metallic filaments through the migration of Al atoms into the P4VP domain during writing. Such nanostructured diblock copolymer thin films open up avenues for fabricating organic memory devices using simple procedures.

Rapid Vapor-Phase Fabrication of Organic−Inorganic Hybrid Superlattices with Monolayer Precision

We report a new layer-by-layer growth method of self-assembled organic multilayer thin films based on gas-phase reactions. In the present molecular layer deposition (MLD) process, alkylsiloxane self-assembled multilayers (SAMs) were grown under vacuum by repeated sequential adsorptions of C=C-terminated alkylsilane and titanium hydroxide. The MLD method is a self- limiting layer-by-layer growth process, and is perfectly compatible with the atomic layer deposition (ALD) method. The SAMs films prepared exhibited good thermal and mechanical stability, and various unique electrical properties. The MLD method, combined with ALD, was applied to the preparation of organic-inorganic hybrid nanolaminate films in the ALD chamber. The organic-inorganic hybrid superlattices were then used as active mediums for two-terminal electrical bistable devices. The advantages of the MLD method with ALD include accurate control of film thickness, large-scale uniformity, highly conformal layering, sharp interfaces, and a vast library of possible materials. The MLD method with ALD is an ideal fabrication technique for various organic-inorganic hybrid superlattices.

Soluble dendrimers europium(III) β-diketonate complex for organic memory devices

We report the synthesis of a soluble dendrimers europium(III) complex, tris(dibenzoylmethanato)(1,3,5-tris[2-(2′-pyridyl)benzimidazoly]methylbenzene)–europium(III), and its application in organic electrical bistable memory device. Excellent stability that ensured more than 10 6 write–read–erase–reread cycles has been performed in ambient conditions without current-induced degradation. High-density, low-cost memory, good film-firming property, fascinating thermal and morphological stability allow the application of the dendrimers europium(III) complex as an active medium in non-volatile memory devices.

Electrical bistability in a xanthene class molecule: Conduction mechanisms

The author study conduction mechanism in two conducting states of a bistable device at 10–300K range. They find that in the electrical bistable devices, electrical switching is associated with a change in the conduction mechanism. Device current in the low-conducting state follows an injection-limited mechanism. The current in the high-conducting state conforms a bulk-dominated mechanism, namely, space-charge limited conduction with an exponential distribution of traps. The bistability has an associated memory phenomenon. The devices exhibit read-only and random-access memory applications for several hours.

Experimental study on thickness-related electrical characteristics in organic/metal-nanocluster/organic systems

Organic bistable devices with the trilayer structure, organic/metal-nanocluster/organic, interposed between two electrodes have been systematically studied by varying the thickness of the organic layers and the metal-nanocluster layer. Devices fabricated in this fashion exhibit either electrical bistability or current step, depending on the thickness of the metal-nanocluster layer. Electrical bistable devices have been studied by fixing the metal-nanocluster layer thickness at 20 nm and changing the organic-layer thickness from 20 to 60 nm. Device injection current at the on state shows an exponential decrease with an increasing organic-layer thickness, suggesting that the electron transmission probability of the devices decreases with an increasing thickness of the organic layer. This is in agreement with theoretical calculations based on the single-band Hubbard model. The evolution of the electrical current step is observed for devices fabricated by fixing the organic-layer thickness at 50 nm and changing the metal-nanocluster layer thicknesses (2, 4, and 8 nm). The discontinuous metal-nanocluster layer is believed to lead to the observed current step. When the metal-nanocluster layer is thick enough resonant tunneling occurs between nanoclusters causing positive and negative charges to be stored on the opposite sides of the metal-nanocluster layer inducing electrical bistability. Discussions of the observed phenomena are presented.

Design and Synthesis of New Polymeric Materials for Organic Nonvolatile Electrical Bistable Storage Devices: Poly(biphenylmethylene)s

The synthesis of new polymers, poly(biphenylmethylene)s, derived from bistriflates of bisphenol-type monomers, by Ni(0)-mediated polymerization has been presented. These polymers are interesting because of the nature of the polymer backbone that contains biphenyl units separated by substituted methylene units. The solubility, mechanical properties, and electrical properties of the polymers can be altered by proper selection of the methylene substituents. Polymers and oligomers had molecular weights ranging from 2000 to 15 000 g/mol, as measured by calibrated gel permeation chromatography (GPC), though light scattering and MALDI studies indicate that GPC tends to underestimate the molecular weights of these polymers. The polymers have Tg's between 230 and 300 °C and have thermal stabilities ranging from 400 to 493 °C. Thermally cross-linkable, 4-phenylethenyl end-capped oligomers were synthesized and fabricated into thin-film electronic devices, and preliminary results on their characterization are discuss...