Min- Chen

Influence of electrode material on the resistive memory switching property of indium gallium zinc oxide thin films

The InGaZnO taken as switching layer in resistive nonvolatile memory is proposed in this paper. The memory cells composed of Ti/InGaZnO/TiN reveal the bipolar switching behavior that keeps stable resistance ratio of 102 with switching responses over 100 cycles. The resistance switching is ascribed to the formation/disruption of conducting filaments upon electrochemical reaction near/at the bias-applied electrode. The influence of electrode material on resistance switching is investigated through Pt/InGaZnO/TiN devices, which perform the unipolar and bipolar behavior as applying bias on Pt and TiN electrode, respectively. Experimental results demonstrate that the switching behavior is selective by the electrode.

Morphology and properties of denture acrylic resins cured by microwave energy and conventional water bath.

OBJECTIVES This study examined the influence of microwave energy levels on the morphology and properties of an impact resistant denture material poly(methyl methacrylate) with a thickness of 10 mm. METHODS A microwave flask containing two resin blocks was processed at 80, 160, 240, and 560 W for 15, 10, 7, and 2 min, separately. Each Flask was then turned over, and cured for an additional 2 min at 560 W. The process using conventional methods was carried out at 70 degrees C for 9 h. The blocks were tested for hardness, porosity, flexural properties, solubility, and molecular weight. The morphology of the specimens after staining with osmium tetroxide was examined by transmission electron microscope. RESULTS The changes in temperature with time were recorded during microwave heating at 80, 160, and 240 W, respectively. A significantly large difference in the curing temperature was observed when comparing these two processing methods. There was little difference in the mean values of surface hardness and the weight percent of the insoluble parts. The mean domain size and the volume fraction of the rubber phase favor of the water-bath method. However, the porosity in the water-bath-cured specimens was much less than that in the microwave-cured specimens. Thus, the conventionally cured specimens showed better flexural strength and flexural modulus than the microwave-cured specimens. SIGNIFICANCE This study has shown that microwave energy can efficiently polymerize denture base polymer. Highly statistical differences in morphology and flexural properties favor of the water-bath method. Choice of a suitable microwave power and polymerization time is important in order to reduce porosity to a minimum level and increase the domain size and volume of the rubber phase.

Bipolar Resistive Switching Characteristics of Transparent Indium Gallium Zinc Oxide Resistive Random Access Memory

This study investigates a sputtered InGaZnO (IGZO) thin film to apply into a resistive random access memory device. After the formation of an indium tin oxide (ITO)/IGZO/ITO structure at room temperature, the device exhibits a repeatable bipolar resistance switching behavior without an electroforming process and an excellent transmittance in the visible region. The conduction mechanisms for low and high resistance states are dominated by Ohms law and space-charge-limited current behavior, respectively. In retention and endurance tests, a resistance ratio of more than 1 order remains after 10 4 s at 90°C and after 100 dc voltage sweeping cycles.

A low-temperature method for improving the performance of sputter-deposited ZnO thin-film transistors with supercritical fluid

A low-temperature method, supercritical CO2 (SCCO2) fluid technology, is employed to improve the device properties of ZnO TFT at 150 °C. In this work, the undoped ZnO films were deposited by sputter at room temperature and treated by SCCO2 fluid which is mixed with 5 ml pure H2O. After SCCO2 treatment, the on/off current ratios and threshold voltage of the device were improved significantly. From x-ray photoelectron spectroscopy analyses, the enhancements were attributed to the stronger Zn–O bonds, the hydrogen-related donors, and the reduction in dangling bonds at the grain boundary by OH passivation.

Physical and chemical mechanisms in oxide-based resistance random access memory

In this review, we provide an overview of our work in resistive switching mechanisms on oxide-based resistance random access memory (RRAM) devices. Based on the investigation of physical and chemical mechanisms, we focus on its materials, device structures, and treatment methods so as to provide an in-depth perspective of state-of-the-art oxide-based RRAM. The critical voltage and constant reaction energy properties were found, which can be used to prospectively modulate voltage and operation time to control RRAM device working performance and forecast material composition. The quantized switching phenomena in RRAM devices were demonstrated at ultra-cryogenic temperature (4K), which is attributed to the atomic-level reaction in metallic filament. In the aspect of chemical mechanisms, we use the Coulomb Faraday theorem to investigate the chemical reaction equations of RRAM for the first time. We can clearly observe that the first-order reaction series is the basis for chemical reaction during reset process in the study. Furthermore, the activation energy of chemical reactions can be extracted by changing temperature during the reset process, from which the oxygen ion reaction process can be found in the RRAM device. As for its materials, silicon oxide is compatible to semiconductor fabrication lines. It is especially promising for the silicon oxide-doped metal technology to be introduced into the industry. Based on that, double-ended graphene oxide-doped silicon oxide based via-structure RRAM with filament self-aligning formation, and self-current limiting operation ability is demonstrated. The outstanding device characteristics are attributed to the oxidation and reduction of graphene oxide flakes formed during the sputter process. Besides, we have also adopted a new concept of supercritical CO2 fluid treatment to efficiently reduce the operation current of RRAM devices for portable electronic applications.

Characteristics and Mechanisms of Silicon-Oxide-Based Resistance Random Access Memory

Traditionally, a large number of silicon oxide materials are extensively used as various dielectrics for semiconductor industries. In general, silicon oxide cannot be used as resistance random access memory (RRAM) due to its insulating electrical properties. In this letter, we have successfully produced resistive switching and forming-free behaviors by zinc doped into silicon oxide. The current-voltage fitting data show that current transport mechanism is governed by Poole-Frenkel behavior in high-resistance state and Ohms law in low-resistance state, consisting with filament theory. Additionally, good endurance and retention reliabilities are exhibited in the zinc-doped silicon oxide RRAM.

Effects of Ambient Atmosphere on Electrical Characteristics of Al2O3 Passivated InGaZnO Thin Film Transistors during Positive-Bias-Temperature-Stress Operation

This study investigates the effects of ambient atmosphere on electrical characteristics of Al2O3 passivated InGaZnO thin film transistors during positive bias temperature stress. Under H2O vapor environment, the Al2O3 passivated device exhibited stable electrical behaviors (ΔV th < 0.5 V), while the unpassivated device showed an apparent hump effect in the transfer curves under bias stress. The hump phenomenon was attributed to the absorption of the H2O molecule which can serve as a donor to develop a conductive back channel. The experiment results suggest that Al2O3 is an effective passivation layer to suppress water vapor absorption in the InGaZnO back channel.

Bipolar Resistive RAM Characteristics Induced by Nickel Incorporated Into Silicon Oxide Dielectrics for IC Applications

In this letter, we successfully produced resistive switching behaviors by nickel doped into silicon oxide at room temperature. The nickel element was doped into silicon oxide, which is a useful dielectric material in integrated circuit (IC) industries by cosputtering technology. Based on the proposed method, satisfactory reliability of the resistance switching device can be demonstrated by endurance and retention evaluation. We believe that the silicon oxide doped with nickel at room temperature is a promising method for resistive random access memory nonvolatile memory applications due to its compatibility with the IC processes.

Low-power bipolar resistive switching TiN/HfO2/ITO memory with self-compliance current phenomenon

In this work, a TiN/HfO2/ITO memory device is fabricated, which shows stable bipolar resistive switching behavior, as well as excellent data retention and good endurance. Moreover, a very low SET voltage of 0.2 V is achieved with a self-compliance current effect. The result brings about an obvious reduction in SET power to 160 µW, which is crucial for future high-density resistive switching memories. On the basis of the conducting filament theory, a possible resistive mechanism is discussed to explain the low SET voltage and self-compliance current phenomenon.

Charge Quantity Influence on Resistance Switching Characteristic During Forming Process

In this letter, we presented that the charge quantity is the critical factor for forming process. Forming is a pivotal process in resistance random access memory to activate the resistance switching behavior. However, overforming would lead to device damage. In general, the overshoot current has been considered as a degradation reason during the forming process. In this letter, the quantity of charge through the switching layer has been proven as the key element in the formation of the conduction path. Ultrafast pulse forming can form a discontinuous conduction path to reduce the operation power.