Search

This paper describes synthesis of graphene/poly(4-vinylphenol) (PVP) nanocomposite and deposition of thin film by electrohydrodynamic atomization (EHDA) for fabrication flexible resistive switching device. EHDA technique proved its viability for thin film deposition after surface morphology analyses by field emission scanning electron microscope (FESEM) and non-destructive 3D Nano-profilometry, as the deposited films were, devoid of abnormalities. The commercially available graphene micro-flakes were exfoliated and broken down to ultra-small (20 nm–200 nm) nano-flakes by ultra-sonication in presence of N-methyl-pyrrolidone (NMP). These graphene nanoflakes with PVP nanocomposite, were successfully deposited as thin films (thickness ~140±7 nm, R a =2.59 nm) on indium–tin-oxide (ITO) coated polyethylene terephthalate (PET) substrate. Transmittance data revealed that thin films are up to ~87% transparent in visible and NIR region. Resistive switching behaviour of graphene/PVP nanocomposite thin film was studied by using the nanocomposite as active layer in Ag/active layer/ITO sandwich structure. The resistive switching devices thus fabricated, showed characteristic OFF to ON (high resistance to low resistance) transition at low voltages, when operated between ±3 V, characterized at 10 nA compliance currents. The devices fabricated by this approach exhibited a stable room temperature, low power current–voltage hysteresis and well over 1 h retentivity, and R OFF / R ON ≈35:1. The device showed stable flexibility up to a minimum bending diameter of 1.8 cm. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we have investigated the resistive switching behavior of nanostructured zirconium oxide (ZrO2) thin film deposition by spin coating. The metal (silver) electrodes were patterned by electrohydrodynamic inkjet printing technique. The X-ray diffraction and Fourier transform infra-red spectra confirmed that the presence of monoclinic phase in the as deposited ZrO2 thin film. The field emission scanning electron microscopic image revealed the uniform deposition of ZrO2 thin film with spherical morphology. The as-fabricated Ag/ZrO2/Ag memory device exhibited the characteristic bipolar resistive switching behavior under consecutive dc sweep. The possible mechanism of the bipolar resistive switching has been discussed in detail. The endurance and retention analysis of the fabricated device revealed the stability of the device. Our results ensure the promising applications of ZrO2 thin film in the memory device applications. [Copyright &y& Elsevier]

Resistive switching effect has been explored in the hybrid nanocomposite of organic-inorganic materials by fabricating all printed memristive device on a flexible PET substrate. Configuration of as fabricated device is Ag/PVOH ZnSnO 3 /Ag. Extremely uniform and high quality bottom Ag electrodes were deposited by reverse offset printing. Active layer of PVOH ZnSnO 3 nanocomposite was deposited by electrohydrodynamic (EHD) atomization and top Ag electrode was deposited by a non-contact printing technique of EHD patterning. Electrical and mechanical characterization showed that resistive switching characteristics of ZnSnO 3 were remarkably enhanced by adding PVOH polymer in it. The fabricated device showed bipolar, nonvolatile and rewritable memory behavior at low operating voltage. A high off/on ratio, endurance and retention time of > 10 2 , 500 voltage cycles and 36 h respectively were recorded without any substantial change in either HRS or LRS. The fabricated memory device showed remarkable mechanical robustness when tested against 1500 bending cycles. [ABSTRACT FROM AUTHOR]

Developments in organic bi-stable non-volatile memory devices have shown that organic materials are essential for the next generation of electrical memory unit owing to their low cost, high flexibility and large scalability. This study depicts an important aspect of organic memory devices by observing the effect of changing device structure on its switching characteristics. Memory devices with a bilayer and bulk-heterojunction structure were fabricated through an all printed technology by utilizing two organic polymers such as MEH: PPV and PMMA. Silver (Ag) was selected as the top and bottom electrode due to its high conductivity and easy processing. Though identical polymers were used in both device structures, but interestingly change in structure caused change in properties. It was observed that bilayer structure had much higher switching ratio and stability against various biasing cycles as compared to its bulk-heterojunction counterpart. Superior switching characteristics of bilayer structure were due to the presence of a well-defined interface between both polymers. Bulk-heterojunction device suffers the drawback of phase separation in a single organic layer between the two polymers. [ABSTRACT FROM AUTHOR]

This paper describes resistive switching in ZnSnO 3 thin film deposited by electrohydrodynamic atomization. The field emission scanning electron microscope analysis showed uniform surface morphology for thin films. The active layer, a thin film comprised of ZnSnO 3 nano-cubes was printed between screen printed silver (Ag) electrodes on glass substrate. Resistive switching behavior of the Ag/active layer/Ag sandwich structure was confirmed by current voltage analyses. The 3×3 array of memristors thus fabricated, showed characteristic OFF to ON (high resistance to low resistance) transition at low voltages, when operated between ±2 V, at 100 nA compliance currents. The memristor array exhibited stable room temperature current–voltage hysteresis, low power operation, retentivity in excess of 24 h. An R OFF / R ON ≈10:1 was observed at V Read =100 mV for more than 100 voltage stress cycles. All memory bits showed similar current voltage characteristics with respect to resistive switching parameters. [ABSTRACT FROM AUTHOR]

We propose all printed and highly stable organic resistive switching device (ORSD) based on graphene quantum dots (G-QDs) and polyvinylpyrrolidone (PVP) composite for non-volatile memory applications. It is fabricated by sandwiching G-QDs/PVP composite between top and bottom silver (Ag) electrodes on a flexible substrate polyethylene terephthalate (PET) at ambient conditions through a cost effective and eco-friendly electro-hydrodynamic (EHD) technique. Thickness of the active layer is measured around 97 nm. The proposed ORSD is fabricated in a 3 × 3 crossbar array. It operates switching between high resistance state (HRS) and low resistance state (LRS) with OFF/ON ratio ∼14 for more than 500 endurance cycles, and retention time for more than 30 days. The switching voltage for set/reset of the devices is ±1.8 V and the bendability down to 8 mm diameter for 1000 cycles are tested. The elemental composition and surface morphology are characterized by XPS, FE-SEM, and microscope. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) printing technique has been deployed to fabricate flexible printed resistive (memristive) switch in a metal–insulator–metal sandwich structure of Ag/ZrO2/Ag on a polyimide substrate under normal room conditions. The top and bottom electrodes were deposited through the jetting of EHD printing and the active layer of ZrO2 between two electrodes was deposited through the atomization of EHD printing process. The achieved dimensions of the printed device were around 100μm×100μm with the thickness of the bottom electrode, switching layer and top electrode were around 230nm, 680nm and 420nm respectively. The fabricated device showed stable bipolar memristive switching behavior around ±3V. The reversible resistive switching behavior was measured with the high OFF/ON ratio of 100:1. The device kept on exhibiting memristive characteristics after being physically flexed over 500 times that shows its viability for flexible electronics applications. [ABSTRACT FROM AUTHOR]

Abstract: An all printed resistive memory device, a 9-bit memristor, has been presented in this study consisting of 3 × 3 memristor crossbars deposited via electrohydrodynamic inkjet printing process at room conditions. Transparent zinc oxide active nano-layers, directly deposited by electrospray process, are sandwiched between the crossbars to complete the metal–insulator metal structure consisting of copper–zinc oxide–silver, where Cu and Ag are used as bottom and top electrodes respectively. The 9-bit memristor device has been characterized using current–voltage measurements to investigate the resistive switching phenomenon thereby confirming the memristive pinched hysteresis behavior signifying the read–write and memory characteristics. The memristor device showed a current bistability due to the existence of metal–oxide layer which gives rise to oxygen vacancies upon receiving the positive voltage hence breaking down into doped and un-doped regions and a charge transfer takes place. The maximum ON/OFF ratio of the current bi-stability for the fabricated memristor was as large as 1 × 103, and the endurance of ON/OFF switchings was verified for 500 read–write cycles. The metal–insulator–metal structure has been characterized using X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscope techniques. [Copyright &y& Elsevier]

Functional thin film of strontium titanate/polyvinyl alcohol (SrTiO 3 -PVA) hybrid nanocomposite was sandwiched between silver (Ag) electrodes for the application of resistive random access memory (RRAM). Bottom Ag electrodes were patterned using high resolution reverse offset printing system while the hybrid composite thin film and the top Ag electrode were deposited through electro-hydrodynamic (EHD) atomization and EHD patterning respectively. RRAM behavior of SrTiO 3 memory device has not been reported on a flexible substrate due to its brittle nature therefore, in this study we have successfully evaluated its mechanical robustness by forming its nanocomposite with highly flexible PVA polymer. The fabricated device showed bipolar, rewritable and nonvolatile memory behavior at low operating voltage. The bistable resistive switching behavior had off/on ratio of ~30, retention time of 8.64 × 104 s and electrical endurance of 500 operating cycles. The device illustrated mechanical robustness when subjected to 500 bend cycles and varying bending diameters. Image 100539 • A flexible resistive memory device was fabricated using hybrid composite thin film. • SrTiO 3 +PVA thin film was deposited using EHDA spray deposition technique. • All-printed memory device exhibited improved electrical and mechanical endurance. • It showed bistable, rewritable, nonvolatile memory behavior at low working voltage. • The device showed excellent mechanical robustness when tested for 500 bend cycles. [ABSTRACT FROM AUTHOR]