1,722,914 research outputs found
Photocatalytic water splitting under visible light with particulate semiconductor catalysts
No full textPhotocatalytic water splitting (PWS) is the most promising technology to produce H-2 energy directly from renewable water and solar light. PWS has made a remarkable progress last decades under ultra-violet (UV) light, but there are many technical challenges remaining for PWS under visible light. Several approaches are taken in search of photocatalysts efficient for PWS under visible light: (i) to find new single phase materials, (ii) to decorate UV-active photocatalysts with a photosensitizer absorbing visible light, (iii) to tune the band gap energy by modifying cations or anions of UV-active photocatalysts with substitutional doping, and (iv) to fabricate multi-component photocatalysts by forming composites or solid solutions. This article discusses the above approaches based on our experimental results as well as data available in the literature. At the moment, the greatest challenge to the progress of visible light PWS is the low efficiency of light utilization. Finding new photocatalytic materials with unique structure and phase is still the key to the success. In addition, the synthesis of these materials with high crystallinity and high surface area is also important, because these properties exert great impact on the activity of the material of the same structure and phase. Finally, smart combination and modification of known materials could also be fruitful.X11143sciescopu
Nonvolatile memory devices based on self-assembled nanocrystals
No full textNonvolatile memory devices are one of the most important components in modern electronic devices. Many efforts have been made to fabricate high-density, low-cost, nonvolatile solid-state memory devices for use in portable/mobile electronic devices such as laptop computers, tablet devices, smart phones, etc. Among the many available nonvolatile memory devices, flash memory devices are of great interest to the electronics industry owing to their simple device structure, enabling high-density memory applications. Flash memory devices in which nanoparticles or nanocrystals are used as the charge-trapping elements have advantages over conventional flash memory devices because the charge-trapping layer and memory performance of the former can be readily optimized. Active research has recently been conducted to fabricate and characterize self-assembled-nanocrystal-based nonvolatile memory devices. We reviewed various strategies for fabricating nanocrystal-based nonvolatile memory devices and discussed the programmable memory properties and the device reliability characteristics of nanocrystal-based memory devices to possibly apply nanocrystal-based memory devices to those used in portable/mobile electronic devices. Finally, novel device applications such as printed/flexible/transparent electronic devices were explored based on nanocrystal-based memory devices. (C) 2013 Elsevier B.V. All rights reserved.X1155sciescopu
Patterning of amorphous-InGaZnO thin-film transistors by stamping of surface-modified polydimethylsiloxane
No full textAn indium gallium zinc oxide (IGZO) layer was patterned and thin-film transistors (TFTs) were fabricated by surface modified polydimethylsiloxane (PDMS) stamping and IGZO solution. The PDMS stamp was prepared by immersion in piranha solution and treatment with UV-ozone to make a hydrophilic surface. Patterned PDMS was inked by contact with the IGZO layer, and then stamped on the desired substrate. The process did not cause etching damage, so the stamped amorphous-IGZO TFTs showed low leakage current of similar to 10(-11) A, high on/off current ratio of similar to 10(8), carrier mobility of 6 cm(2) V-1 s(-1), and narrow hysteresis of 0.2 V. UV irradiation on the IGZO layer caused a photochemical annealing effect that improved the electrical properties of IGZO TFTs. This method provides a simple and versatile process to fabricate transparent metal-oxide TFTs based on patterning the devices by reusable stamping methods.1110Ysciescopu
Control of resistive switching behaviors of solution-processed HfOX-based resistive switching memory devices by n-type doping
No full textIn this study, we investigated the effect of Ni and Ta doping on resistive switching behaviors of solution-processed HfOX-based resistive switching memory (RRAM) devices. The observations are discussed in terms of oxygen vacancies according to doping concentration. The initial resistance and forming voltages are influenced by doping concentration due to the reduction of formation energy of oxygen vacancies, whereby a higher concentration of dopant results in a lower forming voltage and initial resistance of RRAM devices. In addition, the Ni dopant has a significant effect on forming processes in HfOX-based RRAM devices. It is observed that 10% of Ni doping can lead to forming-free behaviors. This study demonstrates the facile control of resistive switching behaviors by doping processes during the preparation of solutions and suggests that proper doping is an easy method that can lead to modulation of RRAM properties for future nonvolatile memory applications.11118Ysciescopu
Highly scalable resistive switching memory cells using pore-size-controlled nanoporous alumina templates
No full textNanoscale resistive switching memory cells with controlled cell sizes in the range of 25 to 90 nm were successfully fabricated using anodized aluminum oxide templates, and their electrical properties were directly measured using a conductive atomic force microscope. The size of the memory cells was systematically controlled by controlling the pore size of the nanoscale masks. The devices exhibited controllable and reliable resistive switching characteristics suitable for programmable memory applications. The reported approach provides new opportunities for the preparation of nanostructured nonvolatile memory devices with continued device scaling.111414sciescopu
Design of an Efficient Charge-Trapping Layer with a Built-In Tunnel Barrier for Reliable Organic-Transistor Memory
No full text112011Nsciescopu
Flexible resistive switching memory with a Ni/CuOx/Ni structure using an. electrochemical deposition process
No full textFlexible 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 simplesolution, 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.111610sciescopu
Reliable resistive switching memory based on oxygen-vacancy-controlled bilayer structures
No full textWe fabricated resistive random access memory (RRAM) devices composed of a bilayer of AlOx. The AlOx layer was synthesized by atomic layer deposition (ALD) with different oxidizer sources. To control the number of oxygen vacancies, we used water and ozone as the oxidizer sources in ALD. The AlOx layer synthesized using water as the oxidizer source (AlOx(water)) contained more oxygen vacancies than the AlOx layer deposited using ozone as the oxidizer (AlOx(ozone)). We fabricated memory devices with a structure of Al/AlOx(water)/AlOx(ozone)/Pt by ALD. After the initial forming process the devices showed reproducible and reliable RRAM characteristics. Bipolar resistive change was observed in Al/AlOx(water)/AlOx(ozone)/Pt RRAM devices with low operation voltages of less than 1 V. Ohmic conduction behavior was dominant in the low resistance state and trap-controlled space-charge-limited conduction was observed in the high resistance state. The resistive switching is related to migration of oxygen vacancies and the formation/rupture of conductive filaments. Oxygen vacancies formed conductive filaments when an electric field was applied, and Joule heating broke them. The reliability of the devices was confirmed by data retention and endurance tests. The reliable bipolar resistive switching properties are attributed to a stable conductive filament in the AlOx(water) layer and partial connection/disruption of a conductive filament localized at the AlOx(ozone) layer.112114Ysciescopu
Resistive switching memory based on bioinspired natural solid polymer electrolytes
No full textA solution-processed, chitosan-based resistive-switching memory device is demonstrated with Pt/Ag-doped chitosan/Ag structure. The memory device shows reproducible and reliable bipolar resistive switching characteristics. A memory device based on natural organic material is a promising device toward the next generation of nonvolatile nanoelectronics. The memory device based on chitosan as a natural solid polymer electrolyte can be switched reproducibly between high and low resistance states. In addition, the data retention measurement confirmed the reliability of the chitosan-based nonvolatile memory device. The transparent Ag-embedded chitosan film showed an acceptable and comparable resistive switching behavior on the flexible plastic substrate as well. A cost-effective, environmentally benign memory device using chitosan satisfies the functional requirements of nonvolatile memory operations.X116443sciescopu
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